texts: Solenoid capacitor circuit for paintball gun

texts:
Recently my electric paintball gun broke so i decided to come up with my own circuit. I tried to reverse engineer  the one my gun had but it was covered in black glue...

I have been trying to design a circuit that will power a solenoid to fire my paintball gun. My problem is that the capacitor does not charge fast enough after being discharged to fire the gun. The capacitor the gun uses is a 6800uF electrolytic cap and the battery is a 9.6 volt alkaline battery specifically for my gun. The solenoid has a resistance of about 1.2-1.5 Ohms. I did the calculations and you need .313 Joules of energy in order to fire the solenoid. Normally i would like to use a regular 9V alkaline battery instead of the 9.6 one. Either way, I'm having trouble keeping the capacitor charged at 9 volts  so that it fires the solenoid repeatedly without dropping the voltage too low.I know its possible because i used the circuit from my friends gun to fire my solenoid while measuring the output of the capacitor. The voltage would never drop below 8.8 volts if i used the 9 volt battery. Any idea on what i can do?

[ I included a picture of the original circuit my gun had. It looks like they have 1 IC, 2 transistors, a few caps and resistors and 1 or 2 diodes.1[The other side just has a button a capacitor and an led [2]]


texts: Do batteries obey Ohm's law during charging?

texts:
A Battery can be modelled as an RC network, which has an impedance. If we take 4.2V L-ion battery with internal resistance of 0.1 ohm, and by applying 4.2 V, at OCV of 3.7V, it will not accept 5A.
What actually happens electrically while charging the battery?


texts:
i am working on piezoelectrics sensors.now after converting the voltage from ac to dc i need to store it in a btttery so that i can further use it as any charging device (THATS later part).Now i need an idea ,that the voltage  through
these plates is discontinuous,my ques is that is there any problem in charging a battery with discontinuous voltage ,if no then its ok ,but if there is a problem ,what can i do to make voltage continuous, or any suggestion u guys have .

thankyou


texts: Is FFC suitable for remote Ethernet jack?

texts:
I'm working on a product design which includes an Ethernet jack (with integrated magnetics) that will need to be remote from the controller. The controller and jack are contained in different parts of the product that rotate relative to each other. Because of this I was thinking to use FFC cable. The total cable distance would be 10-15cm. I'm fine with only 10Mbps so I thought it should work OK.

I was planning to alternate signal with ground in the cable (as described here: I2C on FFC or IDE cable - interference?) but I'm a little concerned about the impedance of the FFC.  I would normally use a calculator like this https://www.eeweb.com/toolbox/microstrip-impedance to determine trace widths, but they assume a ground plane and I wanted to use a standard FFC cable with no shielding.  What would the optimal pitch and conductor width be to achieve 50Ω impedance, assuming the signals were G S G S G, etc.?

The controller would likely be something like the LAN9514, with integrated MAC and PHY. If the above approach is a major problem, would splitting up the MAC and PHY (placing the PHY by the jack) be a better solution?


texts: How is op amp output not zero if inputs have the same voltage?

texts: So I have started learning about op amps and have a question. If Vout is the gain times the difference in voltage at the inputs how is Vout not always zero if we assume the voltages at the inputs are the same due to the golden rule?


texts:
I'm drawing a bit of a blank with this. I have a 1602A-1 16x2 LCD screen hooked up to an i2c port expander chip.

I'm using the screen in 4 bit mode so I have DB4-7 hooked up to GPIO 0-3 respectively.

I have also hooked up RS, R/W and E to other GPIO pins.

I can see the function set binary string is 001010xx to set 4 bit mode with 2 display lines and 5x8 dots display mode. I am thus setting the GPIO 0-3 pins to 0010 and then setting the enable pin high. I set the enable pin back to low and set the GPIO 0-3 pins to 1000. Again, I pulse the enable pin.

All the time, the RS and R/W pins are low to signify Instruction Input & Write, respectively.

I've tested the pins output with a multimeter so I'm confident that they are high and low when they should be... however it's just not working. The screen does not change to 2 lines nor can I send 4 bit commands in a similar way, following this.

Anyone have any insights?


texts:
What physical processes causes the generation of electrical and radio/EM/RF flicker or 1/f noise?
Or why are those sources not generating normally distributed electrical observables (such as thermal noise in resistors).


texts: Extract AC current from AC/DC current generated by a solar module

texts:
I have a solar module with capacitance in nF range. There is an AC and DC current coming out from the module due to the incident DC and AC light. I would like to treat this like an AC/DC current source in parallel with nF capacitor. I need to measure this AC current (square pulses in the 200-400Hz frequency range) at the output. (or in terms of voltage)

DC current range: 1 A to 8 A
AC current range: 5 µA to 80 µA

I cannot connect a large resistor at the output, as my solar module must be maintained at short circuit condition. Also, the circuitry must not depend on the capacitor value.


texts: Bulk capacitor capacitor type and configurations matter?

texts:
When using a bulk capacitor would the type of capacitor matter? For example in an application where 100uF bulk capacitance is needed, would it matter if I use Tantalum, Ceramic, or electrolytic? Because in these situation I am tempted to go with a ceramic one because of much smaller size than the other two.
Also in another situation where 1000uF bulk is needed, which typically only electrolytic can achieve this value, would paralleling ten 100uF ceramics be okay since vertical space is limited compared to the board space?
EDIT: This question just popped into my mind and i am not currently creating a circuit. I understand that a more specific scenario is needed to answer the question. So to add to the question i have two scenario where i had and most likely going to use a bulk capacitor is in a buck/boost converter and a motor driver driver IC.


texts: I'm thinking about making a self contained Bluetooth LE temperature sensor. I'd like it to be usable up to the boiling point of water. All the BTLE device seem to be rated up to 85C. Do you think they would operate at 100C?


texts: PIC32MZ: MSB of I2S data from digital microphone is always high

texts:
I have interfaced a I2S digital microphone to PIC32MZ controller. I am able to read the digital output from the microphone over I2S-DMA transfer.

Following are the details of my set-up:-

Controller:- PIC32MZ1024EFE064
Audio Sensor:- SPH0645LM4H-B
MPLAB Harmony Configurator (MHC) v2.0.6.0

When I play some tone near the microphone, I get somewhat these values:-

0xFA8C8000
0xFA8AC000
0xFA6EC000
0xFA6C8000
0xFA600000
0xFA544000
0xFA6E0000
0xFA6AC000

I tried to cover the microphone with glue and tape (so that it does not catch any audio signals), and got the following values:-

0xF9DD0000
0xF9DD0000
0xF9D9C000
0xF9D80000
0xF9D6C000
0xF9D5C000
0xF9D4C000
0xF9D3C000
0xF9D30000
0xF9D24000

In the answer to the post Digital Microphone : I2S data output, it is mentioned that the I2S has a rather weird one clock offset compared to the other common formats, and if you get this wrong you will always see a 1 in the MSB of the recovered sample which causes everything to appear negative if interpreted as a signed value.

In my set-up, the MSB is always 1 (or 0xF), no matter what input I give to my microphone. I am planning to use my data to calculate the mean, average and peak-to-peak values. So, the sign-bit is important to me.

Now, I have used MPLAB Harmony to configure my I2S.

My questions are,

If the one clock offset of the I2S clock is causing the MSB of my data to always be 1, which settings/code should I modify in MPLAB to resolve this issue?
Apart from the I2S clock issue, what else can be the issues that I must resolve in order to read correct data from my microphone?

Thanks in advance


texts: Difference between ferrite pipe core and full ferrite core?

texts:
Disclaimer: I’m computer scientist
It is possible to buy ferrite pipe core coils and full ferrite core coils. The seller sell them for audio applications.
I’m considering using the coil to measure a slow varying magnetic field (<10kHz) of low induced voltage intensity (<1V).
How could this difference affect the induced voltage ? Is it relevant ?
Edit 1: There is no data sheet. Here is the documentation on the producer’s web page of a coil I bought for testing: https://www.mundorf.com/audio/en/shop/coils/pipe_coils/MCoil-P50-PipeCore/?card=3295.


texts: Capacitances in a PMOS transistor: what about the n-well?

texts: So I'm studying MOS transistors and came across the topic of capacitances between various terminals/contacts, including the bulk terminal. These capacitances are due to lateral diffusion as a consequence of the self-aligned process of the MOS transistors, the channel charge and the PN junctions formed in the MOS. Anyway, a capacitance value that is never defined is the capacitance between the nwell and the p-substrate in a PMOS transistor. These capacitance is never modelled in the schematic, unless we can extract it from the layout of the transistor. Can someone explain me why?


texts:
After various disappointments i finally understood how to find those damn wires on stepper motors.
I tought it was simpler to drive bipolar motors but at the end i prefer unipolar stepper motors.. more cables but easier to drive.

Anyway... after breaking my only L293D i decided to try again with the famous ULN2803A. With some patience and low voltage (5v) i followed the previos mentioned video description and wrote down all the wire sequences of the stepper motors i have salvaged.

OKI EM-199 (SMA6511) from epson printer
OKI EM-154 (STK6711AMK4B) from epson printer
OKI EM-318 (LB1847) from epson printer
Mineba PM35L-048-HPI2  from hp printer
Mitsumi M55SP-1N from hp printer

As you can see i only found the datasheets of the motors that i could not find the drivers datasheet. So...

From what i understand the Mitsumi M55SP-1N:

consumes less: 259mA/phase
the excitation mode is the one used in the library 2-2 Phase excitation
and i know i can use 12v to drive it.

It's the first time i use a stepper motor

  I don't want to destroy my microcontroller or any other part of the
  circuit.

And here is the question:

Am i safe using a ULN2803A to drive the Mitsumi M55SP-1N at 12v from 3,3v or 5v?

by that i mean:

the ULN2803A has already lots of protection diodes.. safe enough?
the Mitsumi M55SP-1N datasheet says 259mA/phase*4=1,1Amp..correct? uln2803 handles 500mA per channel and a max of 2,5A .....
powersupply of 1.25 Ampere....enough right?
A strange thing happend .. @5v with high speed stepping the ULN2803A got hot. 50-60 deg C. normal?

simulate this circuit – Schematic created using CircuitLab

If its ok (safe) .... what Capacitor should i put near the Vin of the stepper motor?

And if you think i should use one of the above stepper drivers or know more about the unknown motors, i'm happy to learn new things...

Note: Like i said i already tested all motors at low voltage & low RPM, all of them work at 5v using the above circuit except the capacitors. This on a breadboard.. now i want to solder it together. I'm new to electronics, and something that, for you, is obvious, is probably something that i don't even know.


texts:
Could someone tell me alternatives to multisim for simulating pic
microcontrollers.

Free alternatives , not just the free demo version of Proteus.

Thanks


texts: Some questions about an active filter design using a design tool

texts:
After a previous question I decided to make an active LP filter by using Analog Device's filter design tool. I found a +/-15V dual supply so I want to use it to power the filter. I'm quite new in using this tool and first I set the desired values for the passband and stop band and chose 4 stage 8th order Butterworth Bessel. One of the reason is that I noticed if I set like this the flatness of the passband does not overshoot with different tolerances. So here is the basic settings:

Then it shows the Bode diagrams for selected component tolerances:

And below is the group delay:

And it suggests LT1007 as a low noise opamp and here is the whole circuit:

I'm not going to solder this on a PCB but on a stripboard or euroboard. And if so far there's no fatal mistake in the design, I'm completely blank about two points.

How can the group delay plot be interpreted? Does it matter in this
filter application if the input is not a pulse but a varying analog
signal? I don't know how to interpret that plot and whether I need
to make any adjustment.
The tool is suggesting me four pieces of LT1007. There is also
LT1125 which is very similar(maybe the same) to LT1007(¿). Is it
better in terms of noise or another issue to use a quad opamp rather
than four pieces of opamp? (Or a cheaper LM324 would be adequate for this filter?)


texts: Why do DMMs have a capacitor on their AC measurements?

texts:
see answers to this question.

Is a capacitor really necessary? And wouldn't it make measurements frequency-dependent?


texts: MP111 Op-Amp: Non-linear gain at low input voltages?

texts:
I'm currently using the MP111 hybrid op-amp set  up as a voltage controlled current source with a gain of 1. But what I'm finding is that at low input voltages the gain is much higher than it should be - up to 8 A/V. As we increase the input voltage the gain decreases sharply and then becomes 1.

Why is the gain so off at low input voltages? Is there a way to fix this?

I'm calculating the gain by dividing the current seen passing through the shunt resistor (Rs) by the input voltage.

MP111 datasheet: https://www.apexanalog.com/resources/products/mp111u.pdf

MP111 configuration as current source (figure 8): https://www.apexanalog.com/resources/appnotes/an07u.pdf

Rs = 0.01 Ohms, Rload = 0.05 Ohms, Rin = 101 kOhm, Rf = 1 kOhm.

The positive and negative rails are at +15V, -15V respectively. Boost functionality is not being used therefore Vboost pins are connected directly to the power rails.


texts: Can I connect two microcontrollers via RS232 separated by a distance of 3.5 inches? Both are on two separate PCBs

texts:
This design has two PCBs, each with a microcontroller. One can be said to be main and the other is a possible expansion if the user wishes to use it.
The microcontrollers will communicate via RS232 (RX, TX, CTS and RTS lines.)
Both boards will be joined by header type connectors.

The first option is to connect it directly, similar to this image:

The next option is to use an RS232 interface chip:

This second option I think that most will tell me that it is the best and recommended, but a third one occurs to me where I only use a buffer as an amplifier of the communication lines as follows:

Is this third option a good idea?


texts:
I'm currently building an FM Microphone kit and I'd like to understand its operation before physically putting it together. The documentation only provides an overview of some aspects and provides no calculations or insight into the selection of component values.

Am I correct in identifying R1 and the condenser microphone (hereafter Mic,) and R2 and R3 as voltage dividers?
Given an input of 9V, R2∩R3 will output 1.59V?
For R1∩Mic to be in voltage equilibrium with R2∩R3, the impedance of the Mic at rest must be 59KΩ?
Why is a polarised type used for C1? (a tantalum cap was provided in the kit if that helps)
What are C2 and C3 doing? Do they form some sort of lowpass filter?
To keep the LC tank oscillating, how do you calculate what power to inject each cycle? (I know it has to be in phase)


texts: What does the abbreviation U.FL-LP connector stand for?

texts: I am writing up a document on a product that includes some U.FL-LP connectors.  I try to always put the full version of abbreviations when they are first mentioned and I assume U.FL and LP in the U.FL-LP radio frequency (RF) connector names are abbreviations.  Please can anyone tell me what the full name is?


texts: Is my Rigowksi Coil turns calculation correct and how to calculate the sensitivity?

texts:
First, I would like to show my calculation. Please correct me if I'm wrong.

Suppose the maximum induced voltage in the coil is 250mV and the current to be measured is maximum 1000 A.

So, the current  equation is:

Suppose the dimension of my coil is:

a=16.5 mm
b=32 mm

According to this formula:

I want to calculate how many windings I should make. The result is:

N = 353 turns

So, am I correct? Or did I make a mistake?

Then, how to calculate the sensitivity?
Can I just simply divide 250mV/(1000*sqrt(2) A) ?


texts:
I wanted to dabble a bit in RF energy harvesting. Nothing fancy, just see what's possible. I came up with the following circuit, but I'm a complete layman when it comes to antennas and the like.

simulate this circuit – Schematic created using CircuitLab

The layman in me says it should work, the engineer says it's never that easy. Am I missing something? Do I have to match the antenna's impedance (and if so, how)? Does the right side of the PCC110 actually work as intended in this scenario? Is this even possible?

Links to the datasheets of the parts:
LED,
Antenna,
Power harvester

There's very little information on the chip... I found a reference design here where it's used together with the PCC210 (see PCC110 datasheet). I was hoping to keep it simple though (and cheap). Also, I want to operate on ~2.4GHz instead of the 915MHz the reference design is for.

Thanks in advance ~


texts: How to protect microcontroler analogue 0-5V input pins from high/negative voltage

texts:
Just a little background info, I'm designing a small standalone battery powered unit to be developed that will allow the output of a sensor to be displayed on an LCD screen and that the input to the unit will have a 0-5V range from the sensors.

My question is how could I protect the analogue input pins of my microcontroller from high/negative voltages while also being able to display values from sensors that do not have this output range?

EDIT: I am designing this device for others to use and will not know what kind of sensor they would be using, all I'm told is to expect a range of 0-5V and include protection from anything else.


texts: Switching high voltage with consistent risetime

texts:
I'm trying to design an IEC61000-4-4 compliant EFT generator for in-house use, which is based on following schematic:

I've been able to determine all values for all components, And I've been able to generate a wave which meets the specifications

rise time 5ns +- 30%;
duration time (to 50%) = 50ns +- 30%;
Vpeak = 1000V +- 10%

I've accomplished this using 4 avalanche transistors in series, with base and emitter connected, and the last transistor triggered with a 1:1 transformer:

The problem with this method is that I cannot vary the voltage from 0V to 4kV, as the avalanche circuit only works for a certain voltage range.

As I would like to make the output voltage variable from 0v to 4kV, I am looking for another way to implement the switch. It needs to switch within 5ns.

If anyone has an idea on how to do this, thanks in advance.


texts: Implications of short burst transmissions in radio? (SDR/gnu-radio)

texts:
First of all, I do not have an electronics background. I have recently been experimenting with software radio using GNU Radio and a USRP1. I came here in hopes that some people outside of GNU Radio could lend some insight into my problem. I am not sure if I'll get any answers from here, but it's worth a shot.

We are experimenting with tunnelling a known communications protocol inside our GNU Radio transmissions. Within GNU Radio's modulators a packet_encoder class takes the incoming data stream, divides it into packets, and then sends it along to the modulator. The modulated data is then sent to the USRP for transmission.

Our problems seem to revolve around very short burst transmissions. For example, we are trying to perform a sort of hand-shaking process where one radio transmits a 'hello' packet and waits for a response. We are unable to reliably transmit single packets, but it seems we can get some throughput if we spam the same packet a few hundred times. Similar setups which continuously stream data from an input file seem to work fine in the same setup.

We have two USRP1 devices with suitable antennas located in the same room. As I have said continuous transmissions seem to work ok, but very short burst transmissions are a problem and we are not able to successfully transmit.

SO, my question is what are the various implications/issues surrounding short burst transmissions in radio? I am having a hard time finding the problem on the software side of things, and was curious if some insight into the hardware could help me. For example, are issues like this common in 'cheap' hardware like the USRP1?

http://en.wikipedia.org/wiki/Universal_Software_Radio_Peripheral

Thanks for looking!


texts:
I am working on a project to switch a spring-applied brake (datasheet, page 84, MCNB 2GR) using a Teensy 3.5.
I only have limited electronics knowledge and am struggling with weird behaviour from the transistor. I have previously asked for some help in this post and have applied the help to create the following circuit:

As opposed to my previous question, I have switched to using a Teensy 3.5 which only supplies 3.3 V as an output on the digital pins.
The idea is to use a Sharp PC817 (datasheet) to isolate the Teensy and the 24 V circuit and then use a 2N3904 (datasheet) to turn on off the 24 V for the brake which is symbolised as R1.
The strange behaviour starts after a few seconds of sending a 3.3 V signal to the opto-isolator. At first the circuit works as expected and the brake turns on and off based on the current state of the output pin. However after some time (probably about 5-10 seconds), the brake doesn't turn off anymore (i.e., it still receives enough power to be in its on-state) when the output pin is turned off. The only way to turn it off is to turn off the 24 V DC power supply.
After some investigation, I found that the transistor gets extremely hot, hot enough to cause burn marks when touching it for less than a second. Considering that the circuit works normally after a little while, I think this issue is transistor related and has some relation to its temperature. I have also taken voltage readings on the transistor and have found the following:
When turned off: E: 0 V, B: 0 V, C: 23.96 V
When just turned on: E: 0.125 V, B: 0.84 V, C: 5.76 V
When turned off after being on 5-10 sec: E: 0.075 V, B: 0.493 V, C: 8.6 V
It seems to me as if the transistor does not completely turn off and still letting enough voltage/current through to keep the electromagnet in the brake engaged.
I am not entirely sure if the temperature is the problem. I am guessing that I may have either chosen the wrong resistance values in my circuit or that maybe the transistor is no good for what I want to do.
Is there a way to fix this without changing the transistor?


texts: Using 1 momentary switch to toggle between two latched states. Plus relay question

texts:
I know there are many ways to do this, but I'm looking for the easiest setup, not necessarily the cheapest.

I need to build a circuit in which a momentary switch alternates power between two 110v lamps. I believe I need to use a D flip-flop and have the output control a relay, but other than that I'm a little unsure. So, press the momentary open switch once, lamp 1 illuminates, press again, lamp 2 comes on. Simple as that.

I don't want to use any microcontrollers. I want to see if I can do this with minimal components. In this case the relays are just operating like transistors, at least from what I can tell.

Is there a simple way to use a spdt relay and just use the flip flop to toggle relay positions? What specific relays should I be looking for? (solid state or mechanical?) And is there a simple flip-flop IC that would work well for this?

I've considered just using a SPST high power switch, but for this project I need to use a specific arcade-style momentary pushbutton and therefore looking for a workaround.

I have to have it built within the week, I really appreciate anyone's help. Thank you, and I apologize if this question comes up a lot.


texts:
In the room I stayed I had a problem with air flow. Even when door and windows closed, a little bit of air still flows and that make me sick especially on winters.

So I want to detect this air flow with a cheap system. I looked for some airflow sensors but I it looked to me not so suitable for my reason. One of the ideas that come to my mind is using Infrared Thermometer and make an image of the room. The places where air flows should be cooler then other sides.

What are you opinions, what kind of system can be used for this reason?


texts:
So i got a multimeter from a friend for free. This is the one:

Multimeter Info

In the manual of the multimeter it says that the lowest resolution of DC Voltage is 0.1 mV. does that mean that i can measure all the way down to 0.1 mV (0.0001V)
or am i getting this wrong?

Thanks!


texts: Buck Converters Decreasing Current Consumption

texts:
I have designed 3 power supplies with 3.3 V, 2.5 V, and 1.2 V outputs.

I use BD9870FPS Buck converter to step down 8 V - 24 V to 3.3 V.

Then the 3.3 V is used as inputs for 2 buck converters ENPIRION EN5322QI to step down to 2.5 V and 1.2 V. These 2 power supplies are used for load.

The 3.3 V output is also used for load.

The question is: when I tested three of them, the outputs (voltage) are stable, good. However, the current draw is decreasing while the input voltage to the 3.3 V buck converter is increased. Is this normal?

I read that a buck converter steps down voltage by increasing current. But what I got was another way around.

So, can you help me to explain this?


texts: Why are the three component LEDs in an RGB LED so unbalanced?

texts:
I was recently spec-ing some RGB LEDs for a project, when I noticed that the millicandela ratings on the three colors are rarely close to the same number. (i.e. 710mcd Red, 1250mcd Green, 240mcd Blue).

Does this cancel out somehow, or does this mean that the LED will always look yellowish?

Also, why do manufacturers make such unbalanced LEDs?  Wouldn't it make more sense to pair up 3 LEDs of approximately the same brightness?

Example: CLY6D-FKC-CK1N1D1BB7D3D3 made by Cree


texts:
I need to measure the following characteristics of a frequency synthesizer using a spectrum analyzer:

Frequency range: 2.286 GHz to 2.346 GHz
Output power: -2.5 dBm to 2.5 dBm
SSB phase noise: typical: -122 dBc/Hz, maximum: -116 dBc/Hz, at 100 kHz offset
Integrated SSB phase noise: -45 dBc, at 100 Hz to 1MHz
Reference spurious suppression: typical: -106 dBc, maximum: -80 dBc, with reference frequency = 15 MHz
Non-harmonic spurious suppression: -90 dBc
Harmonic suppression: typical: -30 dBc, maximum: -20 dBc

Am I able to measure all those specifications using a Rohde and Schwarz FSC6 model .06: datasheet ?

I can choose any spectrum snalyzer in the world, but I was told that Rohde and Schwarz is the one of the best brands, and that's the one I found more useful for the specifications I need to measure, because of its frequency range and phase noise (I don't know if I'm reading it correctly). What do you think?


texts: how to create a square wave with large duration and high duty cycle

texts:
For a "plant waterer circuit" I would like to add a safety feature that prevents watering for over ~3 minutes, and delays the next watering from occurring for ~12 hours.

Currently the circuit is constantly checking the water level to see if water should be added. Thus, it seems that if I could create a square wave that is high for ~12 hours (circuit "off" during this time) and low for ~3 minutes (circuit "on" during this time) then I could use some simple logic to achieve my goal, except I don't know how to create this wave.

Timing chips like the 555 would require unwieldy resistor and capacitor sizes, so it seems those by themselves are not suitable.

I am considering using counter chips, as I could achieve the period I need (~12 hours). However, these output a 50% duty cycle (or 33%, etc.) which I don't want. Rather, the square wave I described above has a duty cycle of about .0042.

Any suggestions? Thanks.


texts: Is there an "L" type of five wire connector?

texts:
With the controller shown,

notice the connector heads "west" (yellow),

meaning a tight enclosing cabinet needs to be as wide as the red indication.

However, if the white connector immediately did a 90 degree turn down

(direction downwards in blue)

you can see it would drastically save width of a tight enclosure.

Is there such a thing?  A 90° version of the white connector seen?

(I suppose ... a 180 degree would be even better, a "backwards" connector)

Note - of course, for a one-off one could just modify the board and I guess solder on five wires which could hang straight down.  However it's not a reliable pipeline when producing many of them, allowing for easy field repairs, etc etc.

(FWIW I considered just specifying to "bend down" the five pins on all units, but then the "locking tongue" of the white connector would have to not exist ... again it's a flakey solution.)

thanks @RemcoVik, trying my best to add more photos!

It has no identifying marks I can see :/


texts:
I am trying to build a circuit using Yamaha Sound chip YM2151 with Yamaha DAC YM3012. This is my first attempt in doing anything with analog signals, so there is much to learn!

While reading a datasheet, I stumbled across the below schematic which shows Analog Ground.

Can someone please explain how it works? Why is there 10/15 V if my circuit required 5 V? How do I build this part of the circuit?


texts: Determining initial conditions for a simple circuit

texts:
Suppose the circuit is in steady state when the switch is at position (1). At t=0 the switch goes from position (1) to position (2)and the problem is to find the response of the system. I am having some difficulties finding the initial value for the voltage on the capacitor. Since it was stated that we can assume it is in steady state for t<0, I solved it in the phasor domain and got that the rms value of Uc=7.01V. Can I somehow use this for the actual initial value(in the time domain). Data given:

R = 10,
L=10 mH,
C=100 uF,
E = 10V,
e(t)=14.1*sin(1000t+ 135(deg)).

EDIT I see a lot of arguments in the comments below, and one question that basically repeats what is said in the question. I would be very grateful if someone could give a concise answer, how to solve it, and if it is not possible, why it is not possible.
EDIT 2 Thanks to everyone who was active in the comments section, and who answered. I will award the best answer. Basically, the easiest way is to solve the circuit in the phasor domain, reconstruct the equations for the time domain, and just plug in the value for t=0, since we are viewing the system for t=\$-\infty\$ to t=\$\infty\$


texts:
I'm trying to configure a DS1307 RTC to be in 12-hours mode.
I've double and triple check my settings, and cannot understand what I have wrong.

According to the documentation, bit 6 of register 0x02 should be high to enable 12 hour mode.
In 12 hours mode, bit 5 of register 0x02 will be high on PM, and low on AM.

I've correctly enabled the 12 hour mode in the register.
But when dumping the content of hour register 0x02 without any modification, I got the following value when transitioning from 11h59m59s AM to the next second: 0x52 -> 0x41.

On those two value, I have the bit 6 high, so I am in 12 hour mode. I also have a correct transition from a value of 12 hour to 1 hour. But the AM/PM bit don't change from AM to PM.

What did I miss here ? I really don't get it.


texts: Why do four cascaded all-pass filters cause a 180° phase shift?

texts:
This op-amp all-pass filter is reported to introduce a 90° phase shift at the cutoff frequency of the RC network placed at the + input.
(The FET is used as a controlled variable resistor to move the phase shifted frequency "up and down.")

In phasers, this signal is then added to the original one to have a cancellation (notch) at that particular frequency.
The famous MXR PHASE 90 phaser, instead, creates two notches to enhance the effect: it does so cascading four elementary phase shifting units like this:

How does that work?
I would expect the series of four identical units to create a 360° phase shift at the RC cutoff frequency, not two 180° shifts at two different frequencies.
It is also reported that in the phase 90 the phase shift is distributed like this (among the elementary units)

How can you have a 45° phase shift per unit using an all-pass filter that introduces a 90° shift?
It all seems very confusing to me.
I would greatly appreciate your help.


texts: Confused about op amp equation derivation

texts:
I'm studying op amps and I'm a bit stumped on a part of the derivation of the difference amplifier. In equation 4-1, I understand that \$R_G\$ and \$R_F\$ form a voltage divider that divides \$ V_{REF} \$ into the voltage at the non-inverting terminal (\$ =V_+ \$). I also understand \$ V_+ \$ is the input to an inverting amplifier circuit, hence the \$
 -V_{in}\frac{R_F}{R_G} \$ term. However, I'm struggling to understand intuitively where the third term comes from:

\$ (\frac{R_F+R_G}{R_G}) \$


texts:
Take this example:

port(clk        : in  std_logic;
 areset_n       : in  std_logic;
 ena            : in  std_logic;
 load           : in  std_logic;
 load_val       : in  unsigned(cnt_width-1 downto 0) := (others => '0');
 counter_value  : out unsigned(cnt_width-1 downto 0) := (others => '0')
);

counter_value should be initialised to some value since it's my output, but is it neccessary to initialise the input values too?

Should all the signals be initialised to 0, including clk and reset?


texts: What's the difference between a commercial JTAG debugger and an open source FT2232H OpenOCD debugger?

texts:
I have seen a few commercial JTAG debuggers such as:

iC6000 On-chip Analyzer (with Aurora protocol support)
Lauterbach – Microprocessor Development Tools

And OpenOCD FT2232H-based JTAG debuggers:

Flyswatter
NGX ARM USB JTAG

Why are these commercial debuggers big boxes compared to FT2232H JTAG debuggers which has just a small credit card size PCB? What additional hardware is present inside the commercial debuggers and in which part of debugging can these help?


texts: phase shift detection between 2 non-periodic signals

texts:
I would like to find the phase shift between two non-periodic signals read from an electret microphone. So what I did so far is the following:

read the signals from the mics using an arduino uno micro controller.
finished writing an fft code based on cooley_tukey algorithm.
tested the fft with the help of matlab.

My plan is:

search for the maximum value in each signal and store its index
find the phase corresponding to the index found in the previous step from fft using:
phase = atan(imaginary/real)
assume phase1 and phase2 corresponding to phases calculated in step(2) for signals 1 and 2 respectively.
difference = phase1 - phase2
if (difference < 0)  →  phase1 < phase2  →  signal 1 came first and vice versa.

So, is this procedure correct? Am I going to get the phase shift using this technique? I would to do a sound localization using 4 microphones.
Thanks in advance. Your help is appreciated.


texts: Output of Compact Fluorescent light (CFB)

texts: I have few unworking Compact Fluorescent Lights and i was wondering what is the output of the circuit?


texts: Output to an op-amp differentiator circuit

texts:
In an op-amp differentiator circuit, this is the input (VPULSE) to the circuit:

Would my output look like this?

If not how would you fix the simulation settings?


texts:
I need to use an ADC to convert analog signals from pressure and temperature sensors to a microcontroller (Teensy 4.0). I'm confused if I should use an ADC with Parallel or SPI interface. I'm currently designing the data processing unit for a rocket and I am worried that if I need 8 inputs from an ADC, It'll take 8 clock cycles to read from 8 registers, but if I read from an ADC with a parallel interface then I can read all the values at the same time. I am confused about how to go about this.

ADC I am thinking of using with SPI interface: http://www.ti.com/lit/ds/symlink/ads8168.pdf?HQS=TI-null-null-mousermode-df-pf-null-wwe&DCM=yes&ref_url=https%3A%2F%2Fwww.mouser.com%2F

This is the ADC with a parallel interface: https://www.mouser.com/datasheet/2/256/MAX11047-MAX11059-1514141.pdf

Edit: More on the application, I need to read the inputs from pressure transducers and temperature sensors in the rocket fuel pipeline. Using the information from the sensors I need to send an output from the MCU to MOSFET relays which will then open the solenoid valves on the pipeline.


texts: All commercial POE products I have seen feature DC current to power endpoint devices.  What are the reason(s) why AC is not used for POE products?


texts: Dashboard Camera - How to Fit a Supercapacitor

texts:
I do not have a background in electronics.

I am using a cheap Chinese sport camera as a dashboard camera – which seems to be a bad idea for the battery started to wear very fast. The battery swollen so much I couldn’t remove it from camera. I was able to remove it after it spent one night in the fridge.

The camera is configured to start when the power cable is inserted and to gracefully shut down when removed. Without battery, it starts fine, but it obviously can’t shut off correctly when unplugged – plus it does not keep the time (which seems to lead to some SW problems).

I disassembled the battery and kept the case and the connector/protection board (see the picture below). What I would like to do, if possible, is to fit some super-capacitors inside the case so as to allow correct shutdown and keep time for a day or two. I know cameras that are able to use super-capacitors, but they were designed for this.

Is it possible? What about the middle terminal? – the one that tells the kind of battery.
If possible, what is the diagram?
How large should be the capacitors? The camera has a display which cannot be turned off.

Thank you.


texts: What is the output type of the sn74lvc1g04?

texts:
It doesn't seem to clearly say totem-pole, open-collector, open-drain, etc.  I wanted to place a pull-up at the output to guarantee a default state, but I feel like this is a bad decision.

datasheet


texts: In pic below I have drawn a full adder and mentioned their delays, please help me to verify my answer.


texts: Lead Acid Battery charging from laptop psu

texts:
I working on a new project of running couple of low power devices from PicoUPS 120 ATV:

The review by this guy: Building a 12V DC UPS

Is this correct, this does not regulate the output voltage, the only thing it does is charges the battery and switch between input sources.

I am using a single maintenance free 12v@10Ah Lead-Acid battery (new).

I am using a regular old laptop power supply, rated for 19V DC 4.42A but the charging current itself for the battery was 4.5 A as I checked. I have found other post here stating that for lead acids this should be about 10-30% of the capacity so about 3A in my case.

Does anyone else have experience here with PicoUPS who can give me some advice how to implement this safely?

Thank you.


texts:
I am just starting out looking at more complex circuit diagrams, and I really do not understand what is being shown here

My initial guess was that this was a series circuit with the probe (consisting of a parallel combination), cable (consisting of a single capacitor) and oscilloscope (consisting of a parallel conbinatiin) all in series, however trying this has led to a very messy equation, so I'm not so sure I got it right. The depiction of the cable is very confusing to me.


texts:
simulate this circuit – Schematic created using CircuitLab
I am making an air blower with a Kingwin RL4B-B1402512H fan. Can I use the wall switch, and if so, can I use the dimmer as well?


texts: How to get the memory state of SRAM on power up?

texts: I am working on IoT authentication using a physically uncloneable function (PUF). I have read several articles which suggest that SRAM PUF can be used for that purpose. However, I want to know how can I read the SRAM memory state? Are there any existing implementations in C or C++ which can be used to retrieve the SRAM PUF fingerprint? If there are some libraries, can someone please point out those?


texts:
I'm having trouble understanding intuitively phase shift for RLC circuits. For example, I have seen the following:

  In the low-frequency regime, which element is the dominating element (highest gain) in this circuit? For the other two non-dominating passive elements, what are the respective phase shifts?

Now for the first question, I know it is the capacitor, as the other two have gains that are close to zero while the capacitor will have a gain near 1. However, I'm lost for answering the second question? Is there a simple way for me to know what their phase shifts will be? Would that simple way to know the phase shifts of those passive elements help with the high-frequency regime?


texts: Getting a large number of (~100) digital output signals from Arduino

texts: I would like to be able to control around 100 independent LEDs using an Arduino.  The problem is that the Arduino does not have nearly enough pins that can be configured for this.  What would be a way to solve this problem?  Is there a chip that can demux a more complex signal from the Arduino that could then control the LEDs?  Or is there another solution?


texts: Gate driver output 25% of PWM frequency - any idea how this is possible?

texts:
I am testing isolated gate driver IRS10752LPBF on the bench and I have a result I don't understand.
The only change I made on my test rig compared to the typical application proposed in the datasheet is that I don't have a bootstrap for the high side but an independent isolated power supply as I want to be able to run at 100% duty factor later on.
The gate output pin is floating for these tests (no MOSFET driven).
Screen shot attached: channel 1 yellow is the PWM signal while channel 3 purple is the gate driver output pin measured against the high side reference voltage.
As it can be seen on the screenshot, the output runs at 1/4 of the input frequency.
I have never seen that before. How is it possible? I am running at relatively low frequency. Is it a possible reason? My controller is limited at 1 kHz on this rig. (I don't see why but I am clueless on this one ...)
Any insight on what could cause this will be welcome
Added a second screen shot after a suggestion was made in a comment: The first  is the original at 50% duty factor while the second is at 25%
At the request of a commenter I am adding a crude schematic of the rig. It is very simple. Channel 1 is measured between pin 3 and 2 and channel 2 ( or 3 as I changed during the tests) between pin 5 and 4

[

Thanks


texts: Prerequisites to learning Passive and Active Filter Design

texts:
I am sorry for this as its not really a "question" per se. I am keen to learn analog filter design. So what prerequisites am I looking at before I start self studying myself about analog filter design? I have covered most of Network Analysis.. Network Synthesis is something which wasn't covered in our syllabus.. and I have been studying about op amps for quite a while.
Thanks!

EDIT: For the "design" purposes.. Do I need an extensive knowledge of Network Synthesis? I was working through a synthesis text and its gonna take quite a while if I have to grasp all of it.. I dnt wanna delve deep into synthesis if I dnt have to fr my purposes.


texts:
A board I'm working on has been populated with a TI TLV320DAC32 sound codec.  My target O/S is Linux and quickly looking in sound/soc/codecs I see support for the TLV320DAC33.

Octopart, DigiKey, even TI's website make no mention of the -33, just the -32.

Does anyone know why there's a difference here?  Was the -33 made for Nokia (I'm guessing since they did the driver) but the -32 is the one for general purchase?


texts: In the context of an vector declaration how does y downto x work when x > 0?

texts:
I am hoping someone can explain what exactly downto is doing for a

y downto x

where y > x > 0

From my reading x is supposed to be the LSB

Example:

constant FOO            : std_logic_vector( 5 downto  0)   := x"F";

  constant BAR             : std_logic_vector( 11 downto  0)   := x"6

  constant BAZ            : std_logic_vector(16 downto 12)   := x"0";

What exactly is the “downto” doing in this context? Why would somebody want to do 16 downto 12 instead of 4 downto 0?

How does the hardware generation look different? Is there wasted space on BAZ from 11->0 if not where is it allocated?

I am reviewing a very large project, so I am assuming they had a reason to define it this way?


texts: How to drive stepper motor at maximum speed with a higher voltage power supply in hand?

texts:
I had a question about "Wantai" Stepper Motor with an Arduino hooked up to an motor-shield.

Looking at the spec sheets the max volts and current allowed in that particular stepper motor is 3V and 2A. I have a supply of 7.5V and 2A.

Does anybody know how to alter the voltage without changing the current?

Also, does anybody know why my motor jerks/lags when I input anything more than 100 revs/min into it? It seems to be pretty slow with minimal torque.


texts: How to (best) use a SPI SD card with STM32F1 or STM32F4?

texts:
Below, is the SD card reader I would like to use. It's using SPI.

On an Arduino I got it to work (using SPI).

However, I want to test it on a STM32F103C8T6, and later use it in STM32F407VET6. However, I see both the F1 and F4 can use the FATFS file system, which I need, but only the F4 has the SDIO peripheral (the F1 has not).

But since it is an SPI SD reader, I don't think I will need SDIO anyway.
However, still I wonder how to control it. Should I find out myself what SPI commands I should sent or are there better ways? Or should I get an SD card reader without SPI?

For my project, the requirements regarding SD are pretty low. I want to read one file from it, from max. 128 KB, and I don't care much about the speed (within one second is good enough). Maybe later I want to write to it too (also no fast time restrictions).

What would be the easiest way to read from this type of SD card reader?

I would rather use CubeMX and System Workbench (Eclipse).


texts: Buffered Kelvin-Varley divider in AD7849

texts:
In ADI's data sheet of AD7849, page 11, it gives the internal structure as below:

It uses a so called 'Buffered Kelvin-Varley Divider'. But i'm not very clear with it's explanation

  To prevent nonmonotonicity in the DAC due to amplifier offset
  voltages, DAC1 and DAC2 leap-frog along the resistor string. For
  example, when switching from Segment 1 to Segment 2, DAC1 switches
  from the bottom of Segment 1 to the top of Segment 2 while DAC 2
  remains connected to the top of Segment 1. The code driving DAC3 is
  automatically complemented to compensate for the inversion of its
  inputs. This means that any linearity effects due to amplifier offset
  voltages remain unchanged when switching from one segment to the next,
  and 16-bit monotonicity is ensured if DAC3 is monotonic.

How the 'leap-frog' connections for DAC1 and DAC2 can prevent nonmonotonicity caused by amplifier offset voltage?  Anyone can explain it in more details?


texts: Teensy 4.x / IMXRT1062 - max output current

texts:
For my projects next revision, I'd like to drop the ULN2803A transistor array I currently use to drive eight optocouplers.
Using optocouplers with a lower current requirement means that I'd only need to sink / source 5 mA of current for each of the eight pins.
Unfortunately, neither the datasheet for the MCU nor the specs of the development board include a rating I'm used to - like the 40 mA per I/O pin limit on the ATmega328P.
Table 12 of the datasheet (1) contains a formula for some Imax;
Imax = N x C x V x (0.5 x F)

where F is the "Data change rate" in Hz - but I believe that would imply I couldn't supply any current if the outputs were static, which is probably not the case.
What currents can this MCU sink / source? How do I calculate that? Can I (safely) drive eight 5 mA optocouplers directly via the MCU?


texts: I am trying to use a LM324 4 channel opamp to create RGB color fading

texts:
Based on this design
http://www.moddingtech.de/tutorials/44-lichteffekte/66-led-fader.html
The LM324 has 4 opamps, this design is only using 2.

In the design one opamp is the timing circuit and the other creates the fade.

I am trying to get a phase shift on the individual outputs to drive pnp transistors that control the colors to the 4 pin RGBs.

Has anyone tried this?

I would like to achieve a slow color fade of a minimum 5 seconds per shift.


texts: Wiring up a 4 pin DVD drive stepper motor?

texts:
I have removed a stepper motor from a DVD drive which looks like the following:
http://forums.parallax.com/attachment.php?attachmentid=102789&d=1373845076

As seen, there are 4 pins in a rectangular arrangement and the problem is that I currently do not have access to a multimeter therefore, cannot check for continuity within the coils to determine which pairs related to which coil.

Within the shown arrangement, is there a "rule of thumb" or an educated guess for determining which pair of pins relate to each coil? I know that in a linear setup where 4 pins are all one beneath another, the "rule of thumb" is that the top two pins are for one coil and the bottom two for the other, is there a similar rule for these???

Also, would I damage anything if I accidentally connected this up wrong? I mean if I connected the coil backwards or mismatched wires between the two coils?


texts: Portable 5v power supply to duplicate wall wart

texts:
I've got a wifi device that works off of a 5v 2a wall wart.  I need to walk around with it to get some signal strength ratings, so I am making it a portable power supply.  However, the device won't boot with anything I've tried except for the wall wart, and it is baffling me.

The wall wart uses a 3.5mm/1.3mm power jack (reads 5.3V open), and I have a USB -> 3.5mm/1.3mm cord I am using with my attempts to power the device.

Here is what I've tried:

Using a usb power bank rated for 5v/2A output.
Using various batteries (up to a 12v SLA to make sure power or amps wasn't the issue) into two separate, known good, buck converter modules that brought the voltage to 5v, both rated for >3amps.
The above with/without a large decoupling capacitor attached to handle any startup current.

Here is what I see:

Wall wart:  Works fine, all LEDs on and steady.

Everything else:  Does not initialize.  Network LED blinking rapidly. (Which indicates a failure to initialize.) Another display led appearing to flicker at ~5-10Hz, like it is briefly losing power.  Ammeter never shows more than ~200ma draw.

Here is where it get's weird: I built a test point just prior to the device to monitor the voltage via oscilloscope.  I had assumed from the flickering (above) that my supply was dropping below 5V intermittently.  However, the scope proved that completely wrong.  The scope data (below) boggles me (left side is the wall-wart, the right side is my portable PSU (12V SLA -->Buck Converter --> 5v output).

(FWIW, both supplies were showing as ~5.2V on a DMM.  The portable has a ripple of +/- .1V.  The wall wart swings so wildly that it occasionally is negative.  If I lower the sampling rate, the spikes get lower in magnitude, but are always way larger than anything on my portable supply.)

So the working supply has terrible voltage regulation.  The supply far better regulation is the one that doesn't work.

What would cause this?  What can I try to make my supply work?


texts:
I am trying to build a Battery balancer system for 16S8P battery pack.It consist of li-on cells(NCR18650PF). I understood how serial balancing is working properly.If serial cells are not equal,an MCU based system or IC is balancing by the algorithm . But what I dont understand is that should I duplicate 8 times for each individual cell packets? I mean suppose that I designed IC for n serial cell and should I do it for m parallel cell?
I hope it is a clear question.


texts: Connecting a 1.5 KW VFD to a 2.2 KW motor

texts:
Today I saw a setup in a factory in which a  2.2 KW 3 phase induction motor is connected to a 1.5 KW VFD.

The motor plate:

the VFD plate:

The motor is connected to a gearbox (the transmission ratio is 1/20 I guess) to control a roller in a fabric rolling machine.

My question is how is it possible to connect a 1.5 KW VFD to a 2.2 KW motor?

Additional Information

I found out that the star connection is used for the motor which, accordong to the motor's plate, demands 5.73A which is lower than the vfd's maximum current (7.5A) does that make sense?


texts: Confusion with understanding the fixed bias circuit

texts:
Below shows a bipolar transistor in fixed current bias configuration. A text says that this topology is independent of β:

What I understand is, since Vcc, Vbe and Rb is constant the base current becomes fixed as:

Ib = (Vcc-Vbe) / Rb

As we see in the above formula since all three variables Vcc Vbe and Rb  are constant, Ib is constant and so fixed.

My confusion is the following:

Imagine if we now change the transistor with the same type but with a different β, will the Ic change?

Thought 1:
I'm asking because I guess we can say that after the transistor is changed the Vbe will not change(?). And according to the Ebers Moll equation the Ic will not change since Vbe will not change.(Ic is determined by Vbe)

Thought 2:
But if we think again after changing the same type transistor with different β which means Vbe will not change and so that means Ib is fixed at the same value as well. But now the new transistor has a different β and Ic = β × Ib. So this tells us that Ic will change.

Which thought above is correct and where am I making the logical flaw?


texts:
I'm pretty new to electronics and hope that this is the right place to post this. I want to take a battery powered analogue clock and make the hour and minutes hands spin faster. I want to make it seem as though the clock is spinning out of control. What is the best way to do this?

Can I make some change to the circuitry inside the clock or should I use an external gear to manually accelerate the speed of the clock hands?


texts: What is the function of these caps on the pcie lines?

texts: There are multiple traces connecting the gpu to the pcie slot to communicate with motherboard. On some traces, which I suspect to be Motherboard to GPU, there are 220nf caps. Normally I would expect some decoupling caps to filter the signal, that would connect to trace on one side and to GND on the other. Are these there so only the ac (the signal) can pass through?


texts: Circuit to drive 3 LEDs that flicker independently

texts:
My basic requirement is that I need 3 higher-powered LEDs that flicker (like those little battery-operated candles you can get), powered from one power supply. The three LEDs should flicker independently.

One way that I know of doing this, is by wiring a "flickering LED" (a.k.a. "candle flicker LED") before the higher-powered LED - similar to this approach.

Image source: Evil Mad Scientist - Does this LED sound funny to you?

The issue with the referenced article is that it seems rather hacky (i.e. the bundled collection of resistors, etc) and that I need 3 LEDs in total, flickering independently.

Given this, I was wondering if someone might be able to help advise exactly what I need to wire where, and what I need to get?

This is the type of higher-powered LEDs that I'm looking at getting, and this (or something similar) is the 12V power pack I was looking at getting (I would consider driving this off a battery pack, but I want it to be on a timer and I haven't found any good low voltage timing solutions). I also want to be able to add a dimmer, just in case they end up being too bright, etc.

Again, I believe this is fairly basic and there may even be a better way of doing this than using the hack referenced.


texts: Question about charge and discharge of a capacitor

texts:
Let's consider the following amplifier:

and suppose that a capacitor is connected between the output node and ground.
Let's suppose that the inverting terminal becomes much larger than the non-inverting one (i.e. I'm considering a situation which triggers the slew-rate condition). The situation becomes the following:

Indeed, the differential pair gets unbalanced and behaves like a current switch. The dc current (blue arrows) of transistor M9 can only flow through M2, M4 and the capacitor, being the other transistors turned off. This dc current discharges the capacitor.

Question: I have never thought to the following doubt, but yesterday suddenly it came to my mind. Assume that, before the unbalancement (i.e. in the quiescent condition), Vdd is 1.8 V and the output dc voltage is 900 mV. When the inverting terminal becomes much larger than the non-inverting one, the current discharges the capacitor. But how is it possible that the blue arrow through the capacitor has that direction? The current must always go from higher potential to lower potential. But here the discharging current goes from ground to 900 mV!


texts: How to find the output voltage of a system with a computing amplifier?

texts:
I got a question regarding the following system.

The only given value is the input voltage $$U_e = 8V.$$
Now the task is to find the output voltage $$U_a.$$
My question now is how do I find this value, if I only know the input voltage and that the computing amplifier is an ideal computing amplifier?
I tried to find a formula for the value that is being searched and came up with the following solution: $$U_a = \frac{R_2}{R_1 + R_2} * U_e.$$
$$R_1$$ is the first resistor viewed from above and $$R_2$$ is the second resistor viewed from above.
How does this formula help me to find $$U_a?$$

(Bear in mind that the rectangle is a resistor as we use this notation in Germany.)


texts:
I am trying to identify an LCD display to get its datasheet. It will help to understand the assembly code of a PIC18F that uses it.

What I know of the display:

the display is part of the K8101 USB message display kit from Velleman
128x64 pixels oldschool grey lcd with white led backlight
the only visible mark is a "A   WR60542801   K" that gives no result
the display had no pcb (so it is a Chip-on-glass kind?) but a 30 pins connector that I soldered in the underlying pcb (and of course, I did not thought about noting any useful reference from the lower side - if any)
the upper "display" pcb only helds 10 1µF ceramic capacitors and 1 1MΩ resistor and communicates with the lower pcb that hold the PIC (18F27J53) via a 18 pin connector. Seems to be in "8 parallel data lines" mode.
while searching for the 30 pin connector, I found it could be driven by a ST7565R controller found on some other lcd boards, but the controller seems to be able to address 132x65 dots so am unsure of that
the board diagram in the assembly manual does show a "ARROWTECH ATP12864WP67" name for the lcd, but searching for that name only retrieves... this assembly manual :(

I already dumped the PIC18 code, so having the display datasheet will help much.


texts: How do I place a long wire to make the EMI and inductance minimum?

texts:
I'm going to measure high current. After seeing that there is not a lot of low valued sensor resistors in the market and the available ones are very expensive, I decided to make my own current sensing resistor by using copper wire.

I wrote down a small program code to play with the parameters to find out a satisfying result (10mV voltage drop at maximum current). I ended up at 2mm cable in 23mm length.

Resistivity of the material : 16.8       mOhm.mm^2/m    (20 C)
Resistivity at amb. temp.   : 18.7464    mOhm.mm^2/m
Ambient temperature         : 50         C
Temperature coefficient     : 0.003862   K^(-1)
-----------------------------
Wire diameter               : 2          mm
Wire resistance             : 0.133333   mOhm
Maximum current through     : 75         A
Voltage drop at max. cur.   : 10         mV
Power loss at max. cur.     : 750        mW
-----------------------------
REQUIRED WIRE LENGTH        : 22.3444    mm

This wire will be connected at the bottom of an H-Bridge which will run at 50kHz frequency.

My demands are:

The cable inductance must be low enough to not damage the H-Bridge MOSFETs.
The rest of the circuit includes a lot of different opamps, and a TL494. I don't want the electromagnetic waves radiated by this wire to disrupt the circuit function.
The cable should consume smallest volume possible.

How should I place this wire? Should I make a winding in which half of the turns are in one direction and the other are in the other direction, so that they magnetic fluxes cancel out each other?


texts: How to attach normal Phone handset to jack 3.5

texts:
I have this Question :

How can I attach the normal phone handset to jack 3.5 to use with my cell phone?

For example : there is a product, http://www.cellphoneshop.net/redtel.html

Could someone give me DIY How-To ? I want to do it all by myself.

I'm Noob in electronics Fields , please explain to me simply.

Thank you in advance.


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So the left button of my mouse was broken and I wanted to repair it by replacing the switch. But when I took the switch off the solder pad came off too. As you can see in the picture below I tore it off clean. Is there anything I can do to save and fix this?

For the record I am a beginner in soldering so I am new to many terminology and methods. Thanks!


texts: Need help identifying unnamed micro-controller

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The chip I want to identify is a micro-controller with RSA cryptography acceleration utilized in a USB module. I suspect it is a chip manufactured by Chinese manufacturer and it might not be a general purpose product as well.

This is the schematic I extracted from the board:

And this is the board photo:


texts: Understanding topology for EMI supression in a power supply

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I am using an isolated DC/DC converter to supply a MOSFET's gate drive, in a high frequency and high voltage application, so I am concerned about the EMI in my design.

In the website of the manufacturer, I could find this document that has a suggestion of external EMI filter (page 3 and shown below), but I am having some difficult to understand the suggested topology:

My analysis

Usually, it is desired a low capacitance between primary and secondary of a isolated power supply. So the use of C2 sound a little bit strange for me in the first time, but I guess that it works like a shunt for the EMI, avoiding it to pass through the power supply. The use of the inductor L1 in series with C2 will create a high impedance for the conducted noise, making noise current flow very weak.

My doubts

Even if my analysis makes sense, it does not seem to enough for EMI suppression. I usually see some sort of dissipative element to “burn” the EMI energy, like resistor or ferrite bead. So, in this circuit, the EMI will only be redirected to the input side, not dissipated. In addition, even if the EMI current has low amplitude (due to the filter attenuation) the non isolated side usually has sensitive devices, so it doesn’t sounds good to redirect the high frequency noise to this side. Would not it be better if it was shunt to another part of circuit and use a bead to dissipate it energy?

Can someone clarify what I am missing in the circuit's analysis?


texts: Working with a BQ4285 RTC from Texas Instruments

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I recently acquired a BQ4285 Real-Time Clock manufactured by Texas Instruments... And I have one major problem! I have little idea how to use it.

I am trying to connect it to an Arduino Mega 2560, and I am struggling to do it on my own, and unfortunately, there is little information about this specific RTC on the web other than the datasheet, which is really quite unhelpful for someone who knows very little about working with RTCs.

Is there anyone here who has experience working with RTCs or who knows enough about them to be able to help me become familiar with them?

Specifically, I would like to know the steps involved in programming them (basically, set the time, date, month, etc.), and the steps involved in reading the data from them.

For more information, the product page from Texas Instruments can be found here.


texts: What is the actual purpose of having a copper foil layer in PCB?

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Out of several layers that make up a PCB, one of them is a layer of copper foil (see image below), What purpose does this layer serve to the PCB?

Also, some PCBs have just one copper foil layer on either sides of the substrate and some other PCBs have two layers on on each sides of the substrate. What difference does having a layer on either sides or on both sides of the substrate make?


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The conductivity of material A is half that of material B. The  ratio of relaxation time of A to that of B is?

As far as I know conductivity is proportional to relaxation time. so the answer should be 0.5, but the answer is 2. please explain?

Am I missing anything here?

And one more question:

when a temperature of conductor is approaching zero kelvin, the mean free path of free electrons in the conductor is proportional to ?

how is it proportional to collision or relaxation time?


texts: Why is the domestic power supply almost universally supplied at 230V?

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Most domestic power in the developed world is supplied at 230V (±10V).

I presume it's a "sweet spot" for something, perhaps:

the highest voltage that won't jump certain insulators
a balance of voltage vs lethal danger
the highest voltage that won't fry various components

Why has that voltage been chosen just about everywhere?


texts: Which accelerometer and storage chip should I use to measure Foosball rod acceleration?

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I want to prove my coworker rotates and laterally moves a foosball rod twice as fast as me.

I was thinking I'd need a biaxial accelerometer (which one?) attached to the rod in between men (to not hinder gameplay). I guess there'd have to be a memory chip near it (which one?), too, to store 20 minutes of accelerometer output. And a battery. And some way to put that data on a computer, after which I'd analyze it.

I'm new to building real things, if you get my drift. Any tips?

(source: wikimedia.org)


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I want to find phase and amplitude spectrum of this signal:

Here is what I have done:

$$f(t)=\sum_{-\infty}^{+\infty}Fne^{jnwt}, Fn=\frac{1}{T}\int_{0}^{T}f(t)e^{-jnwt}dt=\frac{1}{T}\int_{t1}^{t1+\tau}Ee^{-jnwt}dt=...=\frac{E}{T}\frac{1}{jnw}e^{-jnwt1}(1-e^{-jnw\tau})=\frac{E}{T}\frac{1}{jnw}e^{-jnwt1}e^{jnw\frac{\tau}{2}}(\frac{e^{jnw\frac{\tau}{2}}-e^{-jnw\frac{\tau}{2}}}{2})*2=\frac{2E}{Tjnw}e^{-jnw(t1+\frac{\tau}{2})}\sin{(nw\frac{\tau}{2})}$$

I stuck there :( What should I do next?


texts: How to Update firmware of microcontroller using DALI lines of a DALI slave module?

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I have developed a DALI slave module with PIC 16F18326 microcontroller. Now, I want to make a Bootloader for this PIC. But the problem is, I don't have a serial communication or USB connection with the DALI slave module. The only possible way is to communicate through the DALI lines (DA+ & DA-). The DALI-USB from Tridonic or Lunatone can be used to communicate. But, their supporting PC-software allow firmware-update for their products/ devices only.

So right now, if I want to update my firmware I have to use a Programming device, which is not a feasible method. Because, once the DALI device is installed in a building or inside a Luminaire it is difficult to open the DALI slave module and access to the programming pins of the PIC is extremely difficult. (So programming using ICD or normal serial communication methods are not a solution.) The only available wired contacts with DALI slave module are DALI lines (DA+ & DA-) and the Power lines (L & N , through which a communication is not at all possible ).

Do anyone know how to use the DALI lines to update the PIC firmware without having a specific PC-Software or how to bootload a PIC with DALI lines ?

Thank you.


texts: measuring wireless (inductive) power supplies

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I bought an electric toothbrush with a lithium-ion battery and wireless (inductive) charger. It came with one of those air/water jet flossing accessories, which also has a lithium-ion battery and a separate wireless (inductive) charger.

I noticed both devices are compatible with both chargers, despite the instruction manual indicating otherwise. I suppose they have different specifications. Also, not surprisingly I found a different brand toothbrush  also worked with both chargers and vice versa (Philips vs Braun).

I assume mixing and matching could effect battery life and so on where the specifications aren't exactly optimal. Is there some method to determine or predict the effect/consequences of doing this; and how might I (wirelessly?) measure the properties (i.e., output - Volts, Amps, Watts, Joules, Ohms, Hertz, continuity etc.) of an inductive charger and corresponding internal battery/receiver? Usually I would just use a traditional multimeter by probing the exposed (i.e., non-wireless) terminals.

Note: Consistent with the emerging paradigm of consumer electronics; the devices actually appear to be sealed and designed so the battery can't be replaced or even accessed. At least not non-destructively, or without considerable difficulty.

My motivation for asking the question is not anything to do with any of the specific products I've mentioned (I don't really care about toothbrushes, etc. they're just a nice example and useful segue), but more an intellectual curiosity regarding electronics and engineering in general.


texts: Is it beneficial to use a taper for the feed input of a PCB antenna?

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What is your opinion on using a taper for the feed input of a PCB antenna? Say the feed is 2mm wide and the transmission line is 0.45 mm. Would a taper just cause more impedance mismatch? Or would it smooth impedance transition? Would it just be better to use a constant 50 ohm transmission line all the way up to the feed input like in image 2 in green? Here is the explanation from the taper image source PDF: "The taper is needed in order to compensate the abrupt step transition encountered between the microstrip line feed and the antenna."
It seems like the widening of the taper would lower the impedance of the transmission line above the ground plane, but then once it leaves the ground plane and enters into the feed arm of the antenna, the impedance will go much higher with no ground plane underneath, so it seems like maybe the taper would be counterproductive in the sense that it would cause a more drastic transition in impedance, causing more reflections as a result. Although I am not knowledgeable of the effects of impedance on a trace with no ground plane underneath vs with a ground plane underneath, but normally the closer the ground plane is to the trace above, the lower the impedance of the trace. So if there is no ground plane it seems like the impedance would be much higher.
Also, would the taper possibly help to guide the currents smoothly into the transmission line if the skin effect is keeping them on the outer edges of the feed arm when the receiving signal is coming back to the transceiver from the antenna?
And what about the miter? Is this any benefit at all? Explanation from the PDF: "The miter is used to avoid a right angle microstrip bend, which results in a poor current flow on the
stub."
Taper image source: http://edge.rit.edu/edge/P11252/public/PIFA%20Antenna%20Design.pdf


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Im trying to understand exactly how a signal from a coaxial cable is interpreted. From my understanding based on disscussing with class mates and a couple of hours in a school laboratory my best guess is:

The cable working as a capasitor loads up to a degree where the change in voltage can be interpeted as a bit (0 or 1), alternating in a pattern that then gets interpeted by a reciever as data.

Also about the RC constant in a coax, is it correct that if I have a low RC, it would take a shorter time to put/remove a load on the cable, thus increasing the bitrate?

Im not studying electronics specifically, its just a part of a basic physics course im taking.

Thanks in advance!


texts: Is it possible to calculate the load resistance in a full bridge rectifier when given only power, inductance, and input voltage?

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I'm given a full bridge rectifier circuit with values for power, industance, and RMS input voltage: [P = 380 W, L = 85 uH, Vs = 115 V].

The question states to 'select' output resistance for a simulation, but I am unsure if it's possible to calculate this. It might be that it is asking to select an arbitrary number.

I'm guessing that it can be calculated using:

$$
R = V_s^2/P = 34.8 \varOmega
$$
I am wondering if the voltage drop across the inductor can be omitted at steady state. Is this the correct way one would determine the load resistance?


texts: Connect SIM5360 AWS server GET / POST calls

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I have a SIM5360 module, with a Vodafone card, and I would like to connect to some web services, to send and receive data in JSON format, which I have implemented on an AWS server.

To execute the AT Commands I use the Putty tool.

I tried to do it first using HTTP functions with the following calls:

AT+CHTTPACT=”XX.XXX.XXX.169″, 8080<CR>

+CHTTPACT:REQUEST

GET /XXXDWP/rest/user/list HTTP/1.1<CR><LF>
Host: XX.XXX.XXX.169:8080<CR><LF>
Content-Type: application/json<CR><LF>
Accept: */*<CR><LF>
<CR><LF>
<CR><LF>

<Ctrl + Z>

Other examples:

GET /XXXDWP/rest/user/list HTTP/1.1\r\nHost: XX.XXX.XXX.169:8080\r\nAccept: */*\r\nContent-Type: application/json\r\n
GET /XXXDWP/rest/user/list HTTP/1.1 Host: XX.XXX.XXX.169:8080 Accept: */* Content-Type: application/json

But the result of my calls is always:

+ CHTTPACT: 227

I have also tried to do it using TCP functions with the following calls:

AT+NETOPEN

AT+CIPOPEN=0,”TCP”,”XX.XXX.XXX.169″,8080

AT+CIPSEND=0,
>GET /XXXDWP/rest/user/list HTTP/1.1<CR><LF>
Host: XX.XXX.XXX.169:8080<CR><LF>
Content-Type: application/json<CR><LF>
Accept: */*<CR><LF>
<CR><LF>
<CR><LF>

<Ctrl + Z>

Other examples:

>GET /XXXDWP/rest/user/list HTTP/1.1\r\nHost: XX.XXX.XXX.169:8080\r\nAccept: */*\r\nContent-Type: application/json\r\n
>GET /XXXDWP/rest/user/list HTTP/1.1 Host: XX.XXX.XXX.169:8080 Accept: */* Content-Type: application/json

But the result of my calls is always:

……..
http/1.1 400 bad request
server: apache-coyote/1.1
transfer-encoding: chunked
……..

If someone could give me a hand and give me the steps to follow to correctly configure the SIM5360 and be able to make GET / POST calls to the server.


texts: How to switch between two 220VAC motor power supplies?

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I am not an electrician, electronics engineer or anything that will relate me with your interesting profession, but I am a Project Engineer, Mechanical Engineer, etc. and I am working in my spare time on one of my hobbies, so I would like to ask you guys kindly the following question:

I have an 220v electrical motor connected to an inverter which is fed with a 12v battery that I will use as a start up only, but once the motor reaches the max rpm, (the rpm must be controlled from 0 - 1500rpm) I want to replace(switch) the power supply from the inverter with a 220v permanent power supply ,let's say from the grid,but not necessarily.Is there any electronic, electrical or any device that could do the change of supply without interfering with the rest and in a faster way?


texts: Bluetooth 4.0 vs. Bluetooth LE, is there a difference?

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Is there a difference between Bluetooth LE and Bluetooth 4.0?  If so what are the differences?  If I'm buying devices (such as a TI SensorTag) and not the planning to use Bluetooth 2.x or Classic, should I care?

Also, is the preferred abbreviation BLE or BTLE?


texts: What is the best way to convert 1.8 V to 5 V?

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I connected HC-SR04 ultrasonic sensor, to single-board computer BeagleBoard-xM. Trigger pin requires 5 V DC. However, control pins of BeagleBoard-xM can provide only 1.8 V DC.

What is the best way to convert voltage to 5 V? Is there anything else I should pay attention to?


texts: A question on an approximate calculation of an ideal transformer inductance

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I have a 230V to 6V step-down transformer.

I'm trying to calculate the inductance of the primary side 'roughly' in an easy way.

Here is what I have in my mind:
For that I added some illustrations above.
I assume when the transformer's secondary is "not loaded" I can model the primary side as in Fig. 1.
I also assume the transformer is ideal, so I can model it as a series LR circuit as in Fig. 1. (??)

After these assumptions I do the following steps:

1-) When disconnected from power lines, I measure the resistance of the transformer's primary coil 'R' by a multimeter as 133 Ohm.

2-) Then I turn on the power in no load conditions and measure the rms current through the primary by a multimeter this is called Iz in Fig .1.

3-) Now I know R which is 133 Ohm, Vrms which is 230V and Irms; and of course the mains frequency 50Hz. These all reduces to solving L in an LR circuit.

4-) Then I use the phasor diagrams at Fig. 2, and Fig. 3(rms values as phasors here) for obtaining an equation as follows:

(in the figures: Iz = Irms is the rms current looping the circuit which can be meausred by a multimeter; XL is the inductive reactance, VL is the voltage across it; and VR is the voltage drop accross R)

From the phasor diagrams I write:

$$|Z| = \sqrt{{X_L}^2 + R^2}$$

Vrms = Iz * |Z| so;

$$X_L = \sqrt{\left( \dfrac{Vrms}{Iz}\right) ^2 - R^2} $$

$$L = \frac{X_L}{2 \pi f}$$

$$L = \frac{\sqrt{\left(\frac{Vrms}{Iz}\right)^2 - R^2}}{2 \pi f}$$

I can then plug in Vrms, measured Iz, R and f in the above equation and obtain L.

My questions is:

Assuming the transformer is ideal:
Is my equivalent circuit for the primary part in no load condition and the calcuations make sense for a rough calculation?


texts:
I'm looking for some help with understanding (in fact, correcting or confirming my understanding) of how the following circuit works:

U1 here is TL431 voltage regulator, for example from Texas Instruments. This circuit is intended to provide a regulated voltage over Vout pins, and I'm looking for proper explanation how that is achieved. Here is what I managed to figure out:

At some moment, U1 is closed and current is flowing from Vin through R1 resistor directly to the Q1 gate, which opens the transistor at some voltage. In that way, we achieve some voltage at Vout, but we want some regulated, i.e. constant voltage, more or less independent of a load resistance being connected to the output.

When the volate at the source pin of Q1 reaches some point, determined by resistor divider on R2, R3 and R4, U1 opens and current starts to flow through R1, then U1, reducing the voltage applied to Q1 and thus partially closing it, which reduce the voltage at Q1 source pin.

If we remove C2 and C3 capacitors from the circuit, we should see some the pulsations at Vout pin, caused by this transistor opening/closing.

Please let me know if my understanding is correct and if not, how this circuit achieves regulation.

Also if this question is not quite suitable for this site, I do apologise and will remove it.


texts: Safely charging jump-start battery with 80W solar panel?

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I have a limited electrical knowledge and have a few questions.

I have an Allpowers Foldable Solar panel, which has two USB outputs, and one 18 volt output.  I understand that, in full sun at 18V, the panel would be producing 4.44 amps.

I was considering purchasing a 20000mah 'jump start' battery and want to be able to recharge it with my solar panel.  I believe this is a lithium battery, although they don't specifically say on their site:  https://www.suaoki.com/u10.html

The charging input for this battery specifies the charging input as 15V, 1A.  The customer support folks for the battery felt that my solar panel would damage the unit if I tried to charge directly from my panel.

My questions are:

1) Is the problem the excessive voltage in full sun, or, would the problem be the excessive amps, or both?

2) If the problem would be the voltage, would using a buck converter to lower the voltage (to 15V) make it safe to charge through the 15V, 1A charging plug on the battery?

3) Is the excessive amperage a problem, or would the battery draw only the 1 amp that it needs?

4) While I have seen a number of inexpensive converters that would limit the output voltage from the solar panel, I have not found one that would convert 18V, 4.44A to 15V, 1A.  Does this type of voltage and amperage limiting converter exist, or is is simply that the extra amps don't matter in this case?

Thanks for any information you can provide on this.


texts: Rectifier Output Skewed with High Frequency input

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In our lab, we tested a half-wave and full-wave rectifier with the input being a sine function. As the frequency increased, the output began to look triangular rather than hills. I cannot find why this is so. How does increasing the frequency affect the rectifier output?

Thank you!


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Let's say I have a 25bit priority encoder. So each input pin from \$i_{24}\$ to \$i_0\$ has its distinct priority in our encoder. That means that if more than one inputs are active, the encoder will act as if only the input with the highest priority is active, and return a 5-bit vector, \$out_{4..0}\$ (according of course to ceil(log2(25))=5)

Ok, I guess that intro was not needed, everyone knows how a priority encoder works. My question is:----> If we want to change the priority of the inputs, and code a completely arbitrary priority for each input, how many bits is needed to contain the entire coding information?

So my line of thought was this: First input has 25 possible priorities, so we need 5 bits for it's value. Up until we have 16 inputs left, we need 5 bits for each input, so that's 9 inputs coded with 5 bits. Then we need 4 bits for next 8 inputs, 3 bits for next 4 inputs, 2 bits for next 2 inputs, 1bit for next 1 input, and zero bits for the last remaining input. That totals: \$9\cdot 5 + 8\cdot 4 + 4\cdot 3 + 2\cdot 2 + 1\cdot 1 + 1\cdot 0 = 94\$ bits. Is this correct? Do we need 94 bits to completely code priorities for a 25-input priory encoder?


texts: Good faraday cage to block bluetooth beacons

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For a project I need to test often with bluetooth beacons linked to an iOS app.

When I'm at home (office at home) I like to reduce exposure to radiation as much as I can. Not in a obsessive way, but just preventing letting any radiosignalling devices constantly bounce through the air.

I currently have only 3 beacons here, but soon might hold many more. Removing all their batteries is honestly too much of a hassle because of the way the bodies of the beacons are produced.

So I tried to make a small faraday cage, but actually am not really sure what parameters to take into consideration. Online you read a lot of conflicting things (ground or not to ground, multi-layering principals, size and conductor thickness).

I have this test-setup:

I'm running my app to scan for one of the beacons and clearly says around -70 decibels. When I put the lid on the box I'm already seeing drops to -90 and worse, sometimes even disappearing fully from the ranging in the iPhone that I'm testing with. Finally when I wrap the outer (big piece of) foil I'm getting a certain stop of signal. The iPhone fully fails to see the beacon, even with the phone literally laying on the box.

My question; what do I need to take into consideration on having this being most effective? For these three beacons, but also having a lot of them in a  later stage. Also is there any form of electrical/magnetic buildup inside the box? Are there dangers?


texts: Ceramic capacitor value for an LM386N project

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I am adding an LM386 to a music project and follow the guidelines in the datasheet:

My Vs is 4.7 V.
My Vin comes straight from a 12 bit DAC of a Cortex M3 MCU and goes from 0 to 3.3 V.
Pin 7 is not connected at all (I don't have a 10 µF ceramic capacitor (106) at hand right now and I am not sure how close I'd need to be to the spec, I have 104 and 108, but those are magnitudes away).
On pin 5 I used a 0.1 µF ceramic capacitor (104) since I don't have a 0.05 µF (503) one - should this be okay?

The main problem is that I don't get a clean output. I both check it with a speaker and an oscilloscope. I have a ready made breakout board (https://www.ebay.de/i/352510367394?chn=ps) and there I get decent output. On my own circuit, I can head the 'rhythm', but the output is very spiky and noisy (blue is from the ready made breakout, yellow is mine). There is some visual correlation. Any idea? How can I debug this other than comparing the schematics over and over?


texts: Why are my plated drills seen as non-plated by Eurocircuits?

texts: I have drawn a PCB with gEDA suite version 20140316 and uploaded my exported Gerber files to Eurocircuits – I selected Eagle export format. Everything looks fine with the exception all drill holes are seen as non-plated instead of plated (I guess the name of my gerber file, aka mypcb.plated-drill.cnc) is not what Eurocircuits checks). Why is it so and how can I make sure drill holes are indeed plated?


texts: How does this off-dim-bright lamp three-position rotary switch work?

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I have this UBERHAUS floor lamp, with a single-filament, two-terminal bulb.  They have a rotary switch in the tube (stem) that turns clockwise to three positions: off -> dim -> bright -> off.
My question is, how does a rotary switch (which must be small because the tube is only 1" in diameter) dim a 2-terminal bulb?  I tried searching the internet for answers, but I don't even know what you'd call one of these switches.  Also, would this lamp damage a non-dimmable bulb?


texts: Typically, do same-sized SMD ceramic capacitors with different capacitance have different ESR?

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I know that depending on the dielectric, the technology, the company etc, but typically, if say two SMD ceramic capacitors are the exact same size (also of the same technology if you wish,) and their only difference is their capacitance, which one of them has the highest ESR?
Do they "typically" have the same ESR, since ESR it is mainly dependent on the size of the capacitor?
Note that this question goes for impedance as well. Will those two caps have typically the same impedance?
EDIT: Example:
These two capacitors are all the same but their capacitance. One is 1000pF (0.001uF) and the other 0.1uF.
They share the same datasheet which does not state if capacitance affects ESR, for the same size capacitor.


texts: how to hard-bypass the input of a line driver with a switch?

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I want to use a balanced line driver of the type DRV134 or THAT1646. With a bypass switch I want to bypass the IC and send the signal to another circuit instead. In order to null the output of the driver IC in case the switch is in the bypass position, I thought of shunting the input to ground via 10k. Is this the correct way of handling this situation? Is it the correct resistor value? The driver source is an op-amp with no resistor or cap between them.

simulate this circuit – Schematic created using CircuitLab

(the other pole of this switch switches the input of the other circuitry, respectively)


texts: Set function to specific address in PIC18F with the HI-TECH C compiler

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I want to put a function in an specific address of memory like PIC C Compiler (#org).
I'm using MPLAB X, HI-TECH compiler and PIC18F4550.

In PIC C compiler:

#org 0x1000, 0x2000
void MyFunction()
{
}

//In other part of code I'll use: asm("goto 0x1000");

How to do this in MPLAB X with the HI-TECH compiler?


texts: Using switch in a device to indicate water level of two different tanks

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Following Device (circuit) to indicate the water level of two different tanks.

N MOSFET is used as sensor and 5 LEDs as output to indicate water levels.

Switches S1,S2,S3,S4,S5 are coming form tank one; and S6,S7,S8,S9,S10 are coming form tank two.

Separator S11 is used to switch between tank 1 and tank 2.

I think Separator is not enough to switch between two tanks which produces Mix/Misleading results.

I can not figure out, how to isolate both tank's output using Separator and diodes. I can understand there must be diodes to block current flow kindly help..

Update:
added 2 diodes between S1 and R1, and also between S6 and R1. still did not get what it suppose to do.


texts: Can a ground fault be caused by something outside the home?

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Yesterday afternoon, I had a GFCI switch trip. It would not reset. I figured I had a ground fault.

I left the home for a few hours and after I returned I was able to successfully reset the GFCI.

The only other factors worth noting are that before I left the house: a) it was raining outside and b) there was a crew from the city doing some work nearby some electrical power grid infrastructure (transformers, power lines, etc.). I did not see them physically on the poles but they had earth moving equipment. I don't have any idea what kind of work they were doing or if it was related to the electrical system at all.

What could possibly explain this fact pattern? In particular, how could the GFCI not be resetting before I left, then suddenly able to reset after I return? Could the problem have been caused (and fixed) from outside the home? Is this something I should worry about repeating and start looking for ground faults or doing some troubleshooting now?


texts:
I have an ultrasonic emitter, and two ultrasonic receivers. When the emitter emits a pulse, the receivers get the signal at different times. I am only interested in the difference between the two reception times.

At first, I was thinking of using a microprocessor, measuring individual arrival times, and then taking the difference. Taking two absolute measures when only a difference is required feels somewhat unnecessary, and may add inaccuracies.

Is there a way to measure pulse time differences in hardware, i.e. analogically? Would this be advisable?


texts: How to trigger a sampling oscilloscope on a PAM-5 signal

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I am trying to acquire an eye diagram on a Gigabit Ethernet (PAM-5) signal, measuring differentially over pair 1. I am using a Tektronix DSA 71254c.

I have not been able to successfully configure the trigger of the oscilloscope to trigger on the signal so that it produces an eye diagram, using only the differential signal and the oscilloscope without any external clock signal, clock recovery or other hardware.

Is it possible to do this, or do I need additional signals or hardware?


texts: What is  the difference between these two implementations as the feedback is in first implementation the last reg only but the second implementation last reg xored with the input bit, so, what is the difference and how can i take the output from them ?


texts:
Is it recommended to tin PCBs before applying solder stop mask or should I apply the solder stop mask to the PCB and then apply the tinning?

Would tinning before applying the solder stop mask be wasteful in terms of the tin? Or is this a better practice than to tin after the solder stop mask has been applied (to only have the exposed pads be tinned, since the other traces are already covered with solder stop mask anyway)?


texts:
I'm trying to drive a multiplexing double digit 7 segment (5261AS) using Arduino and two shift registers (74595)
I need to separate power supply for the 7 segment to avoid overloading current from the micro.
My question is, should i use transistors to switch power supply for the 7 segment (e.g. using a Darlington array like ULN2003) or powering 74595 vcc from a separate supply other than Arduino's 5v pin is enough?

Thanks


texts: Power circuit with several voltage regulators — design rules

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Please, share your professional rules you follow when designing a circuit with several voltage regulators (for example 5V, -5V, +2.5V, -2.5V, 3.3V).

It`s understandable and can be read in datasheet how to operate with one voltage regulator (adding capacitors). But what should one additionally do to have different voltages stable and accurate?

I have decoupling caps at input and output of all LDOs. I use only LDOs, not switched. They are connected this way: (1) 9V => LP2992 => 5V (2) 5V => LP5907 => 3.3V (3) 5V => TLV700 => 2.5V (4) 5V => LP2664 => -5 (5) -5 => NCP4586 => -2.5

I come to this question when I realized that 3 of 5 voltage regulators in my device do its work perfectly, but two voltage outputs from other LDO`s were wrong: 4V instead of 2.5, 1V instead of 3.3.

Also I have decoupling, which is shown on the image (DVDD = 3.3V, AVDD = 2.5, AVSS = -2.5).


texts: How to generate Red light from a Blue-Dominated Spectrum

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I have a white LED light source, the spectrum of which looks as follows ---

want to filter out red light from this white LED source. But as you can see the spectrum dwindles in the red zone.

And therefore, when I put red filter (absorptive filter) in front of my white LED light source, the brightness suddenly drops down to abysmal values.

Is there a way in which I could use this spectrum and get red lights without compromising on the brightness? I thought about interference and then I came across dichroic filters. But I'm not sure if that'll do it.

I also came across these filters called LEE LED filters which are filters specifically meant for LEDs. But I do not understand the scientific principle they work on. I would be grateful if you can follow the link and explain to me the scientific principle. From the spectrum shown in the link, these filters can give you more than 85% red. But the overall transmission is just 10.1% of the original intensity. So it's kinda bleh. Or maybe I don't understand properly.

A red LED light source would be just perfect for me, but a high wattage (50W-100W) red LED light source is hard to come across in the market.

Let me know if there are other options you guys can think of, for producing cool red LED light. Right now I use a tungsten lamp with RED absorptive filter, but there is so much heat (infrared) in it that my houseflies get fried up. [ I work in an insect flight lab and we use red light for high speed videography, since houseflies dont see well in the red zone]. So I want to switch to LEDs.


texts: Why are charge pumps only used for low current applications?

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Typically the most expensive (and hard to get) elements in a SMPS are the inductors. Thus I was wondering if it's possible to use inductor-less switching mode power supplies (i.e. charge pumps) for generic use cases, for example a bench-top power supply, fixed high power DC-DC converters (several amperes and some hundred watts power), etc.

All charge pump designs I could find though were for low power applications. What prevents one from designing a high power inductor-less power supply? Are there some inherent physical limitations?


texts: How to construct a differential equation from this RLC circuit?

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I'm trying to figure out how to construct a differential equation for the natural response of the following circuit and I am having trouble. The capacitor is initially charged with a voltage \$v_0\$ and I want to solve for \$v(t)\$, the voltage across the capacitor.

simulate this circuit – Schematic created using CircuitLab

Here is my attempt so far:

By Kirchhoff's laws, \$v_L=v_2\$, \$v=v_1+v_L\$, and \$i_1+i_2+i_3=0\$.
The currents and voltages are defined so that \$i_1=-\frac{v_1}{R_1}=C\frac{dv}{dt}\$, \$i_2=\frac{1}{L}\int{v_Ldt}\$, and \$i_3=\frac{v_2}{R_2}=\frac{v_L}{R_2}\$. $$C\frac{dv}{dt}+\frac{1}{L}\int{v_Ldt}+\frac{v_L}{R_2}=0$$ And I cannot come up with an equation the exclusively solves for \$v\$. Is there even an existing solution to this problem?


texts: sensor selection for temperature and humidity readings

texts: do anyone help me regarding selecting the sensor, digital temp and humidity in one module and have digital output and one pin connected to micro controller renesas V850 . I have only 3 pins unused. any suggestions please..


texts: control AC fan speed using microcontroller

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I have been trying for a long time to digitally control the fan speed and light intensity of a dimmable LED bulb, but I am not able to. Basically I want to replace the mechanical potentiometer with a digitally controlled resistance. I have tried every possible dimming solution.

Replacing the mechanical pot with LDR and varying its resistance by illuminating it with LED in closed tube. It's not at all a good & stable solution and the arrangement is difficult to replicate (the output fluctuates greatly).(commercially available solution is very costly)
Cutting a portion of AC waves by detecting zero crossing with the help of a micro (ATTiny). It gives a flickering output when a dimmable LED bulb is used.
Thought of digital potentiometer arrangement, but the voltage that comes across the mechanical potentiometer in a triac dimmer circuit is around 180V when the pot's at the highest resistance level of 300KOhm (The AC supply voltage in my country is 240V). It is well above the digital pot's max recommended voltage of 5V (Vdd) across the variable resistance legs. Can anyone suggest a digital pot that can be interfaced with a 5V micro and can withstand the voltage in a triac dimmer circuit. Is there any other solution to digitally control a resistance. I am willing to achieve this within 3$.

Is there any other better way to do it? Please help.


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I've been trying to build a 5V voltage regulator for a PCB that converts a input voltage from 10 to 30V. I've been searching on internet and I've found that the LM1085 was suitable for this case, with a maximum output of 3A that its fine. The problem is that it just outputs the same voltage of the input instead of the wanted 5V. I've been connected a LED with a resistor to make sure that it has the minimum current of 5-10mA and still outputs 22V.
These are the connections that I have done to the chip(the same that are indicated in its datasheet).
Can somebody tell me why it doesn't work?
Thank you in advance.