texts: Can switching adaptor perform constant current mode?

texts:
I want to ask about  wall adapter (switching) with 2.5mm jack
let's assumed its label as 9V 2A.
I saw many tutorial even some product use normal adapter (2.5mm jack) with BMS module to charge Li-ion cells. (for this function BMS just over voltage protect and balance for each cell) So BMS module it's self don't have function to control charging current.

Q1: What happen when load draw current more than 2A? (Will it perform constant current mode?)

Q2: Is it safe to use wall adapter to charge battery? (Can we consider current on label as charge current?)


texts: How to avoid incorrect ADC readings due to a draining battery supply?

texts:
For a battery-powered design (3 to 3.6V), I'd like to use a sensor that outputs a small, low-power AC voltage signal.
To sample this signal, an ADC is used (this ADC is also powered by the battery), where currently the voltage is boosted by a DC source to prevent the sensor's output signal from going below 0V.

To replace this DC source, I figured a voltage regulator that's about 1/2 of the supply voltage (~1.6V) would work.
However, there's a concern that as the device's battery drains from 3.6V to 3V,
the ADC may read different values due to a fixed regulated voltage used to boost the sensor's AC signal.

Would it be possible or even a good idea to have a regulated DC voltage that is always half of whatever the supply voltage is (i.e.: half of 3.6V, half of 3.3V, half of 3V, etc.)?

(Update)

The following solution is what would have fully answered my question:

Basically:

1) By feeding multiple batteries in series to a 3.6V voltage regulator,
there would be less concern about the ADC reading different values due to a draining battery supply.

2) A decoupling capacitor / high-pass-filter (from Harry Svensson's response), would remove any inherent DC components in the AC signal.

3) A voltage divider would bias the decoupled AC signal to guarantee that the AC signal would always be centered at half the voltage supply.
I think the lower resistance also affects the high-pass filter cutoff frequency.

4) A voltage reference would ensure that the ADC's measurements are less affected by any possible fluctuations in the V+ voltage supply.


texts: Driving mosfets with a 74HCT241N buffer IC

texts:
I'm trying to drive IRLZ44N mosfets with a 74HCT241N buffer IC (as this is what i currently have laying around).  Current setup is trying to switch 2 mosfets which pass a 48V potential.

No previous experience with mosfets i'm afraid, first 74HCT241N connected directly to the gate of the mosfet went up in smoke.

Is there a way to make this work? (ie. with a set of gate resistors) and would i need pull-down resistors on the gate?

Update; added test circuit


texts: Efficiency of classic voltage regulator vs. "switching" regulator

texts:
I have this cheap voltage regulator (DIY kit). After purchase I have seen that it requires a huge heat-sink AND a cooler.

The input is 24V AC and the output will be around 12V DC and I will be used to power a 20W audio amplifier.

My question is: how this regulator compares with a modern "switching" regulator which requires a much lower heatsink and no cooler.
Do I want to use the above regulator or buy a "switching" one?


texts: Solve for junction capacitance from diode's SPICE parameters

texts:
I am trying to calculate maximum junction capacitance (or depletion capacitance) \$C_j\$ for the BAT62-02L diode from this datasheet based on its SPICE parameters:

\$I_s=\$ IS \$=\$ Saturation current \$=250~\text{nA}\$.
\$\eta=\$ XN \$=\$ N \$=\$ Emission coefficient \$=1.04\$.
\$r_s=\$ RS \$=\$ Series resistance \$=190~\Omega\$.
\$C_{j0}=\$ CJ0 \$=\$ Zero-bias junction capacitance \$=284.2~\text{fF}\$.
\$\phi=\$ PB \$=\$ VJ \$=\$ PN junction potential \$=0.224~\text{V}\$.
\$m=\$ MJ \$=\$ M \$=\$ PN grading coefficient \$=0.17\$.
\$\tau=\$ TT \$=\$ Transit time \$=55~\text{ps}\$.
\$V_{br}=\$ BV \$=\$ Reverse breakdown voltage \$=42~\text{V}\$.
\$E_g=\$ EG \$=\$ Band-gap voltage \$=0.53~\text{eV}\$.
\$p=\$ XTI \$=\$ IS temperature exponent \$=1.5\$.

I found this in c11 of MOSFET Models for VLSI Circuit Simulation:
$$C_j=\frac{C_{j0}}{\left(1-\frac{V_d}{\phi}\right)^m}$$
But he says that this only holds for \$V_d\leq\frac{\phi}{2}\$... Another source gives the following:
$$C_j = \cases{\frac{C_{j0}}{\left(1-\frac{V_d}{\phi}\right)^m}, & $V_d\leq \text{FC}\cdot\phi$\\
\frac{C_{j0}\left(1-\text{FC}(m+1)+\frac{mV_d}{\phi}\right)}{\left(1-\text{FC}\right)^{(m+1)}}, & $V_d>\text{FC}\cdot\phi$}$$
Is this correct & am I wrong to assume that \$\text{FC}\$ (the Forward-bias depletion capacitance coefficient) is always 0.5?


texts: How is a pin designed to be analog or digital on a Arduino/Raspberry Pi board? I don't mean what is the difference between analog or digital, or what functions do I need to use to write an analog/digital signal. I mean on one of these boards, certain pins are called "analog" pins and unlike digital pins, the analog pins can detect more values than just "ON" and "OFF." How is this feature implemented on the circuit board (i.e. the hardware)? Does the chip on the board have something to do with it? Where can I learn more about this?


texts: Bottle dynamo (bike generator) rectification and stabilization circuit for LED light

texts:
A friend of mine would like to convert her bottle dynamo (bike generator) to run a LED light.  The light needs to stay on for maybe 90 secs when the bike is stopped, and needs to blink (using a particular pattern).

The generator is labelled as 6V, though it has been difficult to establish what that actually means in practice: the available information suggests that peak voltage varies with speed (see here). On the assumption that the "dynamo" is producing higher voltage than is needed by the uC, Here is what I have in mind for the solution:

The idea for two capacitors as following:

it is difficult to find an affordable supercap that is rated for high voltage, while 5.5 V 1F caps are cheaply available
C1 smooths out the input to the Vreg
C2 is what the LED/uC runs on while stopped. The LED might not be as bright (controlled by R1), but at least it is on.

I am concerned about what happens when the voltage generated by the "dynamo" is not sufficient to supply the uC power, and about wasting power in the regulator. Do you have suggestions for mitigating these problems, and is there anything else I am missing?


texts: What is the bypass capacitor at the emitter of a common-emitter amplifier for?

texts:
Why do we have the by pass capacitor parallel to R(E) in this amplifier circuit? They say it is to bypasses the RE resistor for AC signals but then why is it required to by pass the R(E)

They say that it is to avoid the negative feedback by the resistor but i do not understand the concept of negative feed back in this case? What's negative feed back and why to get rid of it?


texts: How do I build an RC-base negative edge detector, that makes a low pulse on a falling edge?

texts:
I keep coming back here searching for an RC-based negative edge detector for TTL levels, that generates a negative pulse on a falling edge. The only place I find this solution is a certain spot in a certain video by Ben Eater. But I keep forgetting it and there is no clear entry on this site about it, and I'm tired to go back to a video to jog my memory.
Note: I have already answered the question with the only way I know. But it has problems, and therefore I am not accepting my own answer, but the answer that has fewer issues, and is simpler than mine.


texts: What exactly do we write in a test vector?

texts:
My professor has asked me to write Test vectors for the controller shown in the circuit  below:

We have not implemented the controller as of now. I want to understand what exactly we write in a test vector. Is this merely all the possible permutation and combination of inputs?  For an AND gate I can write test vectors very easily:

Reg A;
Reg B;

   A B
1- 0 0
2- 0 1
3- 1 0
4- 1 1

But in the present case I am having different scenarios:

1- BLANK =1, CLOCK=1 (some signals defined in spec of the chip TLC5944)

{

}

2- BLANK =0, CLOCK=1

{

}

and so on.

Is this the correct approach to write test vectors? Can anybody please suggest me what are the best practices for writing test vectors? and what exactly we write in a test vector?


texts:
I want to use several transistors in parallel to control current through a load. This is to distribute the current through the load across the transistors so that individual transistors with a rated collector current less than that going through the load can be combined to control the load.

Two questions:

Would an arrangement such as in the schematic below work well? (Resistor values only very roughly approximated).
How should the resistor values be calculated? I was thinking of using the range of hfe values for the transistor as follows: calculate two collector currents: for the minimum value of VR, the minimum and maximum collector current for the minimum and maximum hfe values.

Thanks

simulate this circuit – Schematic created using CircuitLab

Edit: Actually I would remove R-limit, and have VR stretch across the rails, with the wiper connected to R1-R3


texts:
I was working on the below circuit, to create a balanced audio output.

But have been told this creates a differential audio output, not a 'true' balanced audio output.

"A true balanced output would couple interference on one leg to the other, improving common mode rejection at the receiver. Short either leg to ground. If the amplitude on the other leg doubles, it's balanced."

So my question is how to create this 'true' balanced audio?!

Everything I see online from hours of searching all show some variation of the above circuit, with opamps to create a signal and an inverse signal.

Can anyone point me to a circuit that would create a 'true' balanced audio output?


texts: Digital GPIO vs Analogue inputs on microcontroller

texts:
A general question that I can't find an answer to so easily. Why is it that each digital input pin to a microcontroller doesn't require an extra pin for ground? Each analogue input requires two inputs , + and -. I would have thought that all inputs, be it digital and analogue would need a reference voltage (ground).

I am talking specifically about using a development prototyping board. The one I am using Atmel is Xplained pro for SAMD21 chip.

Thanks in advance.


texts:
I've built a few guitar pedals using op-amps, transistors, etc. (with supporting resistors & capacitors of course), and I've generally 3D printed the housing for the components for custom designs. With these circuits, there is generally static and sometimes radio stations being picked up and amplified. On the pedals and circuits on my full metal test rig, however, I almost never have any interference and noise problems. My best guess is that the metal acts as a Faraday cage and blocks most, if not all, interference that the plastic boxes instead let through. I've thought of different ways to shield my 3D printed pedals with aluminum foil or other metal, but I'm sure there is a way I'm not thinking of. How can RLC audio circuits be shielded in a plastic 3D printed pedal box?

Edit:

The legendary Marshall 100W Super Lead adapted for use as a distortion stompbox is one of the schematics (of many). Schematic from Runoffgroove.com.


texts: How often is FPGA used for UAV flight control?

texts: I need to design a flight controller for a UAV. I searched the internet and found that FPGAs are mostly used for communication (encryption, decryption etc.) and feature extraction. To me it seems that the FPGAs benefiting from ARM, like Zynq series, could be a very nice fit. The problem is I see nobody is using it. Is there any specific disadvantage to it?


texts: Increase incorrect thru-hole size by hand on PCB?

texts:
I recently ordered a PCB and on one component footprint I accidentally set the solder pad size to what should have been the hole size (diameter) for a thru-hole component.

The difference is about 0.5mm / 20mil. The component is a fuse holder with two pins per terminal which I will use with a 10amp fuse (so roughly 5amps will be carried by each pin):

In order to do some testing on this board while I wait for a re-order, I am wondering about a temporary fix. Here are my questions:

Can I use a drill to increase the size of the holes?
Do I need to do anything to the hole after increasing the size in order to ensure a good connection?


texts:
I have a 16 channel SainsMart relay board and I'm controlling 120VAC on one side and DC on the other.

I tested with DC by wiring the source to the common pin, and the load on the NO pin.

I intend on doing the same thing for the 120V rail. However, it's common convention to wire the source to the NO and the load to the common. This way, only one PCB trace and screw is energized while the relay is open.

My only question to my fellow engineers is if they are aware of any downside of wiring the source to the common pin and the load to the NO pin. Essentially, it makes no difference as far as I can see. The relay contacts would seem to have less chance of arcing the way I'm wiring it, does anyone agree or disagree?


texts: Good MOSFET for high-side switching 200mA from 5V logic

texts:
I want to switch the power on/off to the WIFI module using an IO pin of a microcontroller, peak current is 200mA, average current 100mA. Which MOSFET(part number) should I use?

simulate this circuit – Schematic created using CircuitLab


texts: How to set up an analog to digital converter like parallel TLC0820AC, to convert input voltage (volts and tenths) into a BCD?

texts: I would like to use an AD chip to convert the input voltage into two digits - volts and tenths. Such a simple voltmeter. Unfortunately, I don't know how to set the input voltage to get an error-free scale of the 0-10V conversion. I have tried to use a triple voltage divider but it only works fine for volts (one LED).


texts: I made this schematic using NI Multisim and I got asked to find the ‘gain of this circuit using a 1V p-p 1kHz sine signal’ and I was unsure about this because I’m not sure if it means voltage gain or current gain. Anyways I put the desired signal in, but the waveform is the exact same as shown below and I don’t see some type of gain. I just need to know the gain of this circuit and whether this waveform is correct.


texts: Showing through-hole pads in printouts with Altium

texts:
In Altium (at least in version 14) when I create a PDF I don't see the pads.  I generally create outjobs to produce PDFs of the PCB that have different copper layers on each page, essentially a PDF of the Gerbers.  But through-hole pads which are multilayer don't appear on the top or bottom layers.

This is an example of what I mean.  Here is what the PCB looks like in the layout editor:

And this is is what the PDF looks like, top and bottom:

I would like the option to show the pads so I can confirm connectivity, etc. without needing to use a Gerber viewer.  I can change the color of the 'Multi-Layer' layer in the PCB Printout Properties in the Preferences window, e.g. to red, as shown below, but then the pad appears red on all layers, instead of blue on the bottom layer and red on the top layer.


texts: How to calculate correct value of capacitor C2?

texts: I have the following connection, what should be the correct capacity of C2, for the case when the device is turned on, so it will load untill my MC will be not ready? Thanks


texts:
I plan to use a small 220v to 5v buck converter I bought, to power a Wemos D1 mini from 220v mains power. I am not sure how to safely hook it up to the mains power.

It seems that because the system will not draw a lot of current I could use a relatively thin wire, but somehow it feels unsafe to use thin wires for 220v. The power converter I have has small holes in the PCB for the input, so I can not solder 'normal' 220v wires directly to them.

The project is a power monitor which will be installed into a box with a 220v socket. So I can easily branch off the 220v from there. This also means there will not be a lot of strain on the wire as it is all contained in the same enclosure. Another concern however is that I want to keep it small so all can fit into the existing enclosure. To summarize, my question breaks down to:

What type of wire is safe for the 220v input side of the converter
Can I solder the wires directly to the converter or should I use some sort of screw terminals (which will take up more space)
Should I use a fuse between the mains power and the converter?
Should I be concerned about heat beeing generated by the converter in a small enclosure


texts: Full Wave Bridge Rectifier vs.centre tap rectifier

texts: Why does the DC output in bridge rectifier higher than centre tap rectifier.


texts: What external factor could cause increased current draw?

texts:
I have a metal cased device powered by 2x 1.5v AA batteries with a standby current draw of 19.7 microAmps. If I then cause a build up of static by shuffling across a synthetic floor and touch the metal casing, the current draw at least doubles to +50microAmps. I am unsure of the principles behind this effect.

What external factors (to the device) could cause increased current draw? Could an appliance in close proximity that charges capacitors to provide a burst of 10's of 1000's of volts which then discharges cause increased current draw?

Edit - 14:30 29/10/14
The board has a conformal coating and has passed EMC testing covering immunity for residential, commercial and light industrial environments.

65 identical devices were measured for current draw and all were consistently within a current draw range of 0.81uA.

Discharging a static charge by touching the metal casing cause a measurable increase in current draw. The larger the charge, the larger the current draw.

Measurement has been using a digital multimeter wired in series with the positive power feed.

Edit - 15:17 29/10/14
Some further information that has come to light - the device has a battery pack that is located within a metal cabinet (the device itself is on the outside of the cabinet). Also within the cabinet is a piece of electrical equipment that performs automatic self-tests. The battery pack has two wires running inside of the cabinet before going through a small hole to the external mounted device. From my research and suggestions below, it would appear that perhaps ESD or EOS is somehow in play. I do not pretend to understand this field and would appreciate any further answers regarding possible factors.


texts:
Hi I am a Korean student studying physics. Recently I was solving a physics problem about coil emf and I have a question.

As you see in this circuit and the graph, when you close the switch the emf of the coil reaches '-E'(voltage of the battery).
However when you open the switch the emf reaches far more than 'E'
Why does this happen? I already asked my physics teacher and he said that in theory when you open the switch the emf should be 'E'

How does the voltage reach far more than E?


texts: Brushless DC motor values at voltage other than nominal

texts:
I am currently using a maxon three phase BLDC motor (datasheet PN:412825) that is rated for 48 volts (see spec sheet below). I am running the motor at 18.5 volts (requirement for my application). I am in the process of tuning the controller, and the application is asking me to enter some values such as peak current and continuous stall current.

As far as motor characteristics, I believe these are constant and are irrelevant to changes in voltage (correct me if I am wrong).
For the values such as stall current and nominal current, I'm assuming these are dependent to the system voltage.

My question is: Can I just take the values from the datasheet, or do I have to calculate or obtain them from an experiment? If so what are the steps to obtaining these new values.


texts: Bar connecting leyden jars on wimshurst machine

texts: So I finally finished building my wimshurst machine! Disks are around 14" and it works, but the sparks get about 1/2" :( so i was wondering what i could fix and for my metal thats connecting the outside of both leyden jars, im using a thin ribbon cable wire. Is this an issue? Should i replace it with something thicker or is this not the problem?


texts: When using SWD interface, is the reset pin necessary?

texts:
When using the SWD interface, is the reset pin is necessary?

In JTAG, there are 5 pins TCK, TMS, TDO, TDI and RST but usually SWD is a 2 wire interface. So I am confused about this.


texts: Phone disassembly: what's that part for?

texts: I replaced a broken screen for a Moto G (1st generation), and now I'm struggling with 'ghost inputs/ghost touches'. In order to track down the problem, I came across a part which is located between the backside of the screen and the 'mainboard' of the phone (see image attached). What is this part required for?


texts:
What is the shortest time (pulse 010) to visibly light a LED?

Visibly = The human eye can see the LED blink.

I use 5V as source and PIC16F628A@20MHz for the project.

Here is a datasheet for the particular LED (red).

Extra question: What is the shortest time needed for the LED to receive max current (20mA) through it?


texts: 74LS14 datasheet question (Short-circuit output current)

texts:
the 6th row in the table (Short-circuit output current).
When exactly this value is to be considered? (When output shorted to ground? or Vcc?)
And does it mean I have to consider this value (i.e using external resistor) or is it just what's built into the chip?


texts: How to detect when a 3v supply is on with Raspberry Pi

texts:
I am working on a project automating my garage door.
The machine that operates the door provides a 24v out that is only on when the door is open (flashes while the door is moving then stays on for as long as the door stays open)
I intend to use that 24v power to let my Pi know whether the door is open or not.
I bought a step-down chip to get from 24v-> 3.3 (or 3v?) in order to intercept the signal with the pi.
This is the chip:

I need some help on how to actually connect the 3v output to my GPIOs.
With my limited knowledge, i suppose ill need to short my PI GPIO to  PI GND
with a resistor to act as a pull down.
Then the stepdown's + to the pi's GPIO and the stepdown's - to the pi's GND?
Do i have it figured out correctly or am i going the wrong way?
Will a 10kΩ resistor be enough?

Thanks in advance.


texts: ESP8266 ESP-01 internal pull-up at pin GPIO0? +GPIO2 doubt

texts:
I have a PCB prototype which uses an ESP8266 module, ESP-01, the first ESP model with a 4x2 male pin header, and I will interface the ESP with a microcontroller.

My main doubt is about GPIO0 pin of this module. GPIO0 is floating on my PCB. I measured the voltage on it and observed 3.3V. Ok, it should have an internal pull-up resistor on the module. But the question is: can I, WITH SURE, leave GPIO0 floating? (considering that I don't want to flash the ESP memory via UART). Does all ESP modules have internal pull-ups at these 2 pins?

The other GPIO of ESP-01, 'GPIO2', is connected to an I/O of the MCU and that I/O of the MCU is configured as output and driving logic 1 (3.3V) to the GPIO2 pin. Maybe it would be better to configure this I/O of the MCU as digital input... Do you have any observation about putting that I/O of the MCU as output?

Regards.


texts: Frequency response of accelerometer MMA7361L

texts: In order to create the model of the MEMS accelerometer MMA7361L I'm going to need the frequency response of it, but I don't have access to the university lab to use the oscilloscope because of the pandemic and I don't have one at home. Has anyone profiled the frequency response of the MMA7361L before?


texts: AC Power Socket Connector without polarity connected to switching power supply module

texts:
I bought a switching power supply module to convert ac power from wall into dc for my electronic Projects. It looks like this:

it looks like that without the case/cover:

I plan to connect the module to male plug IEC320 C8 AC Power Socket Connector rated: 2.5A 250V. It looks like this:

The C8 AC Power Socket Connector will receive electricity from my wall. As you can see the AC Power Socket Connector do not have polarity. It can be connected either way, but the supply module AC INPUT pins is marked with N and L.

Do i need some reverse electricity protection ?

Do i have to connect the C8 AC Power Socket in a certain polarity with the supply module because of the N and L ? or it will work in any polarity?

Please help me to understand


texts: How to calculate battery ratings for your solar panel?

texts:
If I want to choose a battery for my solar panel which is required to run a load of 5 kWh/day. Then I will be needing a battery with a rating of above 23 ampere hours since 5 kWh/220 V (since 220 V we get from grid in Pakistan) is equal to 23 ampere hours.

I want to ask if a battery is of 23 A and it runs for an hour VS a 1 ampere battery which runs for 23 hours. Will they be both accurate as a battery backup for solar panel? Because they both makes 23 Ah
And if yes, then I wonder how this 1 ampere battery will provide current to my household? My appliances won't run, will they?
If no, then why do we even calculate ampere hours when they are of no use?


texts: How do you pronounce the following set of 'words'?

texts:
I've heard people pronouncing the following 'words' in different ways and I would like to know the correct way of pronouncing them.

SPI (spy vs s.p.i)
I2C (I.2.C vs I.squared.c)
LED (lead vs L.E.D)

I use s.p.i, i.2.c and l.e.d because these are all abbreviations and not really 'words'. I mean, people don't really call USB as us-b right?


texts: RLC band pass filter — getting the correct phase

texts:
Consider the RLC band pass filter circuit:

I’m trying to construct this circuit with a maximum of the transfer curve at \$f=5-6\$kHz and bandwidth \$\beta=2\pi \cdot 2\$kHz and so I have chosen a 88k\$\Omega\$ resistor, 7H inductor and 0.1nF capacitor, according to the formulas $$f=1/(2\pi \sqrt{LC})$$ and $$\beta=R/L \ .$$
See the attached image. The maximum occurs at approximately 4.5kHz. The blue wave on the oscilloscope is the output signal after the resistor in the circuit above. The yellow the input signal. At 4.5kHz however, the waves are out of phase. Aren’t they supposed to be in phase?

EDIT1: As the frequency decreases below 4.5kHz, they get in phase. Above they get even more out of phase.
EDIT2: After increasing capacitor by 100 and decreasing resistor and inductor by 100, the two signals are more or less the same as the frequency varies.


texts: Reduce golf cart voltage from 48V to 36V

texts: I've got a 48V golf cart. I had a light kit installed. The kit is a 48V kit instead of 12V so there is no voltage reducer. I want to add indicator lights on the dash to let me know when the blinker or flashers are on. I can find 36V indicator lights but not 48V. What can I use to bring the voltage down to 36V for each indicator? The current draw for each light is 6.6mA.


texts: Freescale HCS08 Background Debug Module (BDM) connector: clarification wanted

texts:
I'm designing a device which contains a Freescale HCS08 (9S08GT32). In the datasheet I found this drawing (page 237):

I can't tell from the text whether this is a view on the PCB's header or on the BDM' cable connector. Can you tell me which it is?


texts:
I have a SOT-23 SMD transistor marked "2.X L" as shown in the image.

I managed to find out that "2X" stands for 2N4401 and the dot seems to mean "lead free". But I couldn't find the meaning of the perpendicular "L". I think it could be a "date code" but I'm not sure and I don't know either what its purpose is (e.g. does it affect the pinout?).
I would appreciate any help.

Regards


texts:
I'm rather new to electronics, and I'm really in trouble here.

I'm have a bit of a puzzle here, regarding my Rigol DS1052E Oscilloscope.
I'm trying to adjust the probes, but I get a wierd result on channel 1.

For both channels I use the same settings:

Coupling = DC
Bandwidth limit = on
Probe = 10x (Also 10x on the actual probe)
Digital filter = OFF.

I use the squarewave on the scope as input for both channels, and I use the same (one) probe for both channels.
Channel 2 gives me the expected squarewave with 3 volt signal.
Channel 1 however, gives me 1/5 = 600 mV and the signal is nowhere near a squarewave. See attached photos.

Please give me your advice.
If I can assist you with further information, then please feel free to comment regarding this.

Thanks in advance.

Channel 1:

Channel 2:

Images on link with pure DC (3.84V) measured with multimeter:
https://drive.google.com/open?id=0B7SZfQswIltgMkszckpuN2lMaEU

Channel 1: 3.84V DC

Channel 2: 3.84V DC


texts: Technical term for this kind of PLC I/O?

texts:
I don't claim to be an electrical engineer or even an electrician as I work with software more often than hardware, my job does however often work with panel wiring and wiring I/O; I was hoping someone could define a type of wiring for some technical documentation I'm putting together?

The component being used is a Phoenix ILB ETH 24 DI16 DIO16-2TX wired to support simple outputs and inputs using the image below:

I would generally feel to these as PNP/NPN but I think this only apply to a circuit using a transistor? Any explanation as to explain this type of wiring would be great as I understand the practical side but not the theory.


texts:
I need some simple solution, for grounding an AdKey for a short time lets say 200ms, only once, on each power on.

I don´t know the exact needed time so it would be nice if i can change the time with an resistor or so.
Till i found the right time.

I am using that circuit to power on/power off the load.

Is there a way to hold up the grounding from the on/off keypress a bit longer. becaus when i put the AdKey direct behind the on/off button. and u press the right time or make 2 short presses. It triggers. (The mcu take a bit time to bootup.)

Can that solution work?

So after 100ms or so the p-channel JFET(J1) should cuttoff,and stopping the ADKEY Ground.    In a couple days my hfet should arrive and i can tell more.

Big Thanks in front.


texts: Where to put freewheeling diode in relay circuit?

texts:
I am building a circuit to lock/unlock a door using a standard electromagnetic door lock (http://www.amazon.com/Seco-Larm-E-941SA-600-Enforcer-Electromagnetic-Holding/dp/B00196YB5Y) and controlling it with a PIC microcontroller. I selected an appropriate relay (http://www.digikey.com/short/7cdzzv) with a 13mA switching current that the PIC could drive safely.

I have read in a number of places that I need a freewheeling diode to protect against inductive loads, and as such I purchased a few 1N4007. My understanding is that I need one across the coil to protect the PIC, but I am wondering since the electromagnet is an inductive load, do I also need one to protect the relay? Most articles talk about the freewheeling diode in one place, but not the other.

Thanks!


texts: Characterizing Solar Panel Efficiency Based On Lumen Input

texts: I'm new to the solar power field. I am trying to mathematically determine the output of a PV system based on the amount of lumens being directed onto the system. I have a lux meter which I plan to take periodic samples to see how much light will be hitting the system.  I am having trouble finding the correlation between incoming lumens and output power. I see a lot about peak power, but at what lumen threshold is this achieved?


texts: Altium: How to place the pin name inside rectangle in schematic library

texts:
How can I make the pin name to be adjacent to the "Active X" mark on the pin?

In earlier version of Altium it was default. Here V.17.

In V.19 it is the opposite. In order to make the name go inside the rectangle I have to set the margin to -600mil

But as you see, it screws up the whole alignment.

Here on the 555 timer schematic it is perfect.


texts:
I have a circuit like this. I want to calculate the gain of this circuit. If there is no R4 then it is easy to calculate.But now I have a problem. If I have a input current I=0.5A, then what is the output current or voltage ?

Sorry, last resistance is 50 ohm.  not 100.


texts:
I'm currently doing some independent research on silicon based devices and I have come up with one question I can't seem to find the answer to elsewhere.

I understand that when an n-type and p-type silicon are put back-to-back the free electrons from the phosphorus diffuse over the barrier and combine with the boron atoms free valence shell holes. I understand that this comes to equilibrium and an electric field opposed to further diffusion is created, the remaining free phosphorus electrons are opposed by the positive boron ions and that force is greater than the pull from the boron holes further away.

Now what I don't understand is why then the electrons on the p-type side that have combined with the boron atoms cannot diffuse further over the p-type silicon.

The only thing I can think of is that the boron atoms are happy being negative ions as this satisfies the octet rule and the boron holes in the p-type haven't got enough energy to break them out of the valence shell.

One last smaller question is do the boron negative ions oppose the n-type free electrons or are the boron holes too far away to further attract the electrons? I presume the former due to the fact the n-type free electrons don't diffuse into the n-type side depletion zone. This also applies to the boron holes, I presume they are repelled by the positive phosphorus ions.

Thanks in advance for anyone's help and sorry if this relates more to physics than EE.


texts: Can't turn ON transistor from output of comparator?

texts:
I can't seem to turn on a 2n2222a with the output of a LM339 comparator, as soon as the base is connected to the output, directly or with a resistor, even if the output is 5 volts, 9 volts, I always get 0.6 volts to the base of the transistor?? How odd...there is a pull-up resistor on the output of LM339.
I also tried a super simple comparator setup with LM324 op-amp, and same thing, I only get 0.6volts when the output is connected to base...

What am I missing? Why always 0.6 volts?


texts: How is NAND flash going to die when overheating

texts:
If I have a NAND flash which is say 70°C rated, what is going to happen to that NAND flash when I heat it to 80°C or 100°C?

I'm thinking of a scenario when the 70°C rated sample actually starts producing errors at 71°C and I'm not looking at a sample which will have no problems above 100°C.

My current assumptions are that it can either the logic be corrupted (like in RAM and CPU) or the actual NAND bits can flip more often?

I'm basically trying to figure out a high level testing methodology that can run from Linux.

Thanks!


texts: How to apply solder paste with stencil in a 2 sided PCB?

texts:
I have seen lots of tutorials about how to apply solder paste using a stencil, but all of them only show how to apply the stencil to one side of the PCB. My current project is 2 sided and I would like to make 2 stencils (one for the top and one for the bottom) for easier application.

Is it there any tips and tricks for doing it or DIY in this case will fail and I need something more industrial?

(In case someone didn't get the problem, once the first side is soldered it won't be flat anymore, so the application of the stencil becomes impossible by the usual DIY way).


texts: Weird output Pulse in Vector Waveform in Quartus 2

texts:
I have an obscure output pulse in my output waveforms for my half-adder. Is it because that the inputs are both high at 40ns? So I should slightly delay b going high after a has gone low? The time 58ns suggests this is the case because the FLEX 10k70RC240-4 has a propagation delay of approximately 20ns.

My output looks like and the pulse is at about 58ns:


texts: How can I stop my relay chattering as the voltage falls?

texts:
I'm powering a relay from a 12v power source, however this source does not immediately turn off, rather falls gradually for a 'fade' rather than straight off.

Unfortunately this makes my relay chatter multiple times in rapid succession open/closed just before it opens for the last time until next power on, as the voltage is just fluctuating around the critical level.

How can I avoid this? I tried some capacitors and while it helped I still wound up with it chattering at the end (Although slightly less).


texts: Why 28V DC bus is a de facto standard in Aviation industry?

texts: 12V bus is a de facto standard in cars. Aviation has 28V DC bus as a de facto standard for most of the commerical jet aircrafts. Any particular reason behind the selection of 28V for the DC bus?


texts:
Can you please help me to identify this connector?

It's being used to connect a 6V power supply (4 x D batteries) to a PCB

EDIT:

The pitch appears to be just over 2.5mm. Please see image below for evidence of this. I've also attached a further image of the top elevation.


texts: How can i use a BLDC motor driver to control a brushed dc motor?

texts: I have a BLDC motor driver and i wonder if i can use it as a controller for a brushed DC motor.


texts: Electronics in high temperature - operating 30 mins - 2 hours, up to 500 °F - possible?

texts:
Would electronics survive if the ambient temperature of the environment was between 120 °C (250 °F) and 260 °C (500 °F) and the operating time was between 30 minutes and 2 hours? After this time the electronics would cool back to room temperature.

As others have mentioned, items going through reflow would hit these temperatures, but only for a short period of time.

Of course this would be based on "normal" components, not "space grade" items.

Would some kind of coating help? Something like High Temperature Epoxy Encapsulating & Potting Compound 832HT Technical Data Sheet.


texts: Replace Tight Capacitors for Better Tolerance?

texts:
There are some capacitors (10 \micro F and 4.7 \micro F) which are limiting my development of Raspberry Pi Hats because they are provided only with tolerance of 10% or greater.
It seems that the physical components which they use are difficult to extract from the nature, making their price if available high.
I would like to understand how you can replace such capacitors with low-cost components.

My current design requires me in using the expensive capacitors.
I think how you can replace those with cheaper ones without altering the other components of the board. I can easily make the board bigger if necessary for cheaper replacement.

How can you replace tight capacitors with low-cost components for better tolerance?


texts: Is there a way to know if there is a flyback diode?

texts:
I have two 12V water pumps that I want to control with an Arduino via a relay. They are generics and I am unable to find a reliable datasheet:
Good Pumps with Rohs Motor:

Goso GB37-530

Is there anything I can measure to check if they already have a flyback diode, or to know if they need it?


texts: What type of sensor to detect if an object passes through?

texts:
(Sorry for my bad English)

Hello guys, I need your help since I have no idea about electronic stuff.
I have a table soccer and want to install motion sensors in the goals, so whenever the ball passes through the goal line, the computer counts 1 goal.
The ball's diameter is aprox. 4 cm (1,6 inches).
Since I can´t access the inside of the ball return cup (where the ball goes after it passes through the goal,) I can‘t install the goal counter there. So it really has to be placed in the goal.

I have the following questions regarding this project:

What kind of sensor do I need for this? Keep in mind it has to be a sensor that doesn't disturbe the goal, when a player shoots I obviously don't want the sensor to block the ball. So it has to be pretty small and/or thin.
Are there maybe any foldable or flexible sensors for this?
What hardware is the best option for this matter: Rasperry Pi, Arduino or maybe others?
Since my table soccer has a glass plate on top to prevent the ball from escaping the field, could I place some kind of laser motion sensor right one milimeter (0,03 inches) before the goal? Like a barrier that consists of multiple lasers in a row which point down through the glass and detect if an object passes through? Is this possible?
It'd be pretty awesome also, if I could calculate the speed of the ball once it passes through the goal line in km/h or m/s (like in tennis for example.) Is this possible?


texts:
I have an ac signal in the range of 1.5v-10v and it needs to be shifted down by 0.5v so it is in the range of 1v-9.5v. How can i do this exactly? assuming it uses a single power supply.

any help appreciated.

thanks


texts:
I am wondering why 12V is the standard voltage for LED strips (RGB/W) when each SMD LED whether it be 3535 or 5050 is usually rated for ~3V.

A lot of energy is wasted as heat through the SMD resistors for each LED.

Wouldn't it be beneficial if LED strips/drivers were 3V?


texts: Powering LED Strip with the right supply

texts:
I am currently working to power a very large project. I am in the US and am planning to run some large amounts of 5M (16.4') 12V 5050 RGBWW Supernight 300 LED/strip (EBT459). I calculated the length I need to run as 72.5'. My calculations are as such...

The strip I am using uses 3.2 watts per foot, so calculating in with 72.5' gives me a total of 232 watts. Adding in the Rule of 80% it comes out to 290 watts. After calculating amperage, I am at 24.16 amps, so 1- 12v, 30A, 360W power supply.

However, I am running 8 strips, 4 per level, which will require signal amplifiers, set in between each run of 2 strips (10 meters) to combat dimness.

I decided to up the power supplies to be 2- 12V, 60A, 720W power supplies, one to run each length of 4 strips. These will be connected into a TC420 LED timer box then run to the LED strip to control color effects.

My question is, can I run the LED signal amplifier, from the SAME power supply as the strip will be connected to? Meaning, run the leads for the amplifier back to the same power supply that will be connected to the LED controller and have 1 power supply be able to power the entire 72.5' of strip, or will I have to break it down and run multiple power supplies, meaning 1 power supply to run each 2 strip section of LED?


texts: How can I tell how many power supply's it is safe to put in series?

texts:
So at university, to provide both negative and positive supply rails for op amps, we were told to set two independent supplies to a required voltage, lets say 15V, then plug the positive terminal of one of them to ground, and the negative terminal of the other to ground and thus achieve -15V and +15V.

This is a diagram of the sort of thing we did:

My question is this, if you wanted to achieve a higher voltages by adding even more power supplies, what would be the limiting factor at which point you could no longer add supplies safely (Without blowing them up)? What specs on the data sheets of my power supplies determine this and I should look out for?

Also does the relative voltage to ground have any effect, or just total potential difference. For example does it matter if I do this:

or this:


texts: Thevenin voltage (Voc) with a resistor in the way?

texts:
simulate this circuit – Schematic created using CircuitLab

I'm still having trouble with how Thevenin voltages are obtained. Above is an example with designated terminals (red). What if there is a resistor in the way (R3)? Is Voc only R2/(R1+R2)? How can R3 not matter? How can a voltage be obtained, even if "open", without closing the circuit?


texts:
So this segment of transmission like has inductance, resistance and a capacitor in series in one of the branches.

They have calculated the equivalent impedance as follows:

My question is, in the calculation of the total impedance why is the angle of the inductive reactance taken to be negative and that of the capacitive reactance taken to be positive?
I thought it was supposed to be the other way around? like below:


texts: How to power multiple microprocessors and loads for a modular system on single bus?

texts:
I am considering high-level design choices to build a modular system. I want to make a single design of a microprocessor board that can be connected to identical copies of itself and share a single bus so they can be easily hooked together and communicate with one another. So that the end user could connect say between 3 and 20 of them in a row without thinking and have it work.

I am thinking that each microcontroller would be powered with an LDO and also control switching transitors that would connect the ground and power lines to another load for simplicities sake lets say a high power LED the microprocessor cannot provide enough amperage to power. Only one of these LEDs out of all of the boards would be turned on at a time.
Is this a reasonable high-level design to pursue if I get a large enough power supply? Or will I run into problems connecting so many LDOs in parallel that I am not thinking of or need an insane amount of power? Would the better design decision be to have a second power supply to power my loads just to make the engineering easier on myself?
I know the easiest solution in terms of design would be to connect each board directly to the power supply but that would lead to a rats nest of cables and what I am trying to avoid. A single bus with more cables would be ok.


texts: How to read a high voltage signal with Arduino (wirelessly)

texts:
I am trying to build a tachometer for my motorcycle, something like this:
https://youtu.be/GmLaNy2NBcQ

What I need to determine is the time between two spark plug "sparks". How could I determine whether there is current flowing through the spark plug wire or not? (On/off)

I thought of using inductive pickup but I am not really sure how to do it... Would a Hall effect sensor do the job?

The bike has no tachometer from the factory and no tachometer wiring or anything (2004 Cagiva Raptor 125).


texts: Can an audio receiver with a 130v-rated switching power supply be modified to be used without a power transformer?

texts: I have a Harman Kardon AVR, imported from the US, which uses an SMPS (130v) that I will use in Asia. Is there a way to modify the component inside the Power supply so that I can use it without a bulky, and rather unstable transformer? I know the simpler way is to just use one, but humour me if you have any wild suggestion.


texts:
I am using camera traps a with passive infrared sensor for my research and last week I decided to test their detection zones. I expected to find detection zone looking like this:

with a certain angle and range in which the sensor would operate, but instead I kept finding that the camera would only detect within a more 'rounded' zone:

Is this normal for passive infrared sensors? Or is it a consistent measurement error? Someone mentioned directivity to me but I have not been able to understand how that applies here. I hope this is the right place to ask, otherwise please point me in the right direction.


texts:
What would be the right syntax for writing a variable lets say the int 100 into the RTC Memory of an ESP8266 12-E module and retrieve it after reboot or deep sleep.
I am using the Esp8622 12 E with an USB to serial converter and I am flashing it with arduino ide.


texts:
we have a circuit using a DAC http://www.analog.com/media/en/technical-documentation/data-sheets/AD5593R.pdf so basically the DAC output voltage is from 0 to 5V

This DAC needs to finely control current in a LED (that needs from 8microamp to 15 miliamps in 1024 steps)...therefore the need for a Mosfet

Can anyone help us to find a suitable part ?

Adding three more details (important)
1. We will use an ADC for sensing
2. Vin = 5v
3. Controller  will be present on board


texts:
I'am working with Stm32f4 discovery board ,
i need to know the right value of the pull up resistor on the GPIO port

all there is on the datasheet is : week pull up

Thank you


texts: Usage of complex filters in communication

texts:
In the last stage of a communication transmitter, at the front end a filter is used to eliminate unwanted signals from other frequencies. As far as I read in literature, are these filters "real" filters? Why can't we use a complex filter in communications?

If the answer is no, can you give me an application where complex filters are used ? (In signal processing).


texts: sallen-key bpf giving low gain after coupled to differential input

texts:
I designed a Sallen-key band pass filter where the gain at center frequency is 45.6dB. After feeding it with a sine wave at the center frequency, it amplifies the signal by 45.6dB. However, after coupling the output of a Gilbert cell (at 25mv max and consisting of two multiplied signals with the carrier at the center frequency), the band pass filter only amplifies it 1.6 times.

I used an op-amp to subtract the two voltages from the Gilbert cell as well as to isolate the currents. The input measured at the input of the filter is 25mv so why is the output only 40mv?


texts: About the mechanical layer in altium PCB

texts:
I have downloaded the footprint for ATmega32 SMD as in the figure my question what is the need for the mechanical layer with purple and green  colors in this foot print (and after fabricating the board is this layer will be appear on the pcb)
What do we have mechanical layers and what are they used for?


texts: If op-amp offset trims are provided, but not needed, what is the best practise for connecting them?

texts:
I'm using op-amps with offset trims available, but not needed as they already have very low offset voltage. What is the best practise for the PCB pad connections - should they simply be left floating?

(I'm beginning to realise how much my degree left out)


texts:
I am desigining a 4-layer PCB with the following stack-up: Signal Top, Ground Plane, Power Plane, Signal Bottom.

This is the first PCB I make like this, which includes a noisy SMPS with a switching frequency of 600KHz, as well as a 32MHz uC and a wireless 2.4GHz module.
I wish to isolate the noise of the different blocks and prevent it from interfering in another block, for example, the SMPS and uC noises should not interfere with the wireless module. For that, I am splitting the power plane in three closed areas, one for each voltage (SMPS' generated 5.0V and 3.3V and 5.0V from a very small 50mA linear regulator for the auxiliary turn-on system), but keep the ground plane unsplitted and covering all of the board. The SMPS, the uC and the wireless module blocks are separated from each other's on the board.

The questions are:

This split up arrangement would help from noise traveling between the modules?
Would pouring up ground copper in the top and bottom sides help reduce EMI noise
external to the board?
Would be better to also split up the ground plane (and NO ground pouring on top and bottom sides to avoid a loop), and connect it in a star fashion? I heard that is better to keep the ground plane whole, but everyone seems to have his own version.

My understanding is that a ground place should always be below or above the signal and power traces to minimize loops and reduce EMI generated by the board. Also, IF the different blocks are already physically separated on the board, their return currents would flow in the unsplitted ground plane without interfering with each other. Is that correct?
But I also read about splitting the ground plane into zones, one for each subsytem and connecting these different blocks in only one point (star connection). Which is better, and why?


texts: Why don't we get shocked when we touch a car?

texts:
According to this answer to a question about car batteries:

  [...] so the entire chassis is an extension of the minus terminal of the battery.

If this is the case, I would expect that you'd get shocked when you touch something metal on a started vehicle if you're grounded.

I've read that 10mA passing through the heart at a high enough voltage is enough to kill a human, but only if the voltage is high enough (which in the case of most car batteries is only 12V.)

Is the voltage simply too low to produce an electric shock?


texts: Dim a LED array through PWM on power supply or output enable?

texts:
I have an 8-LED array driven by an 8-channel source driver (TD62783AP) controlled from an 8-bit shift register (74HC4094).

When it comes to dimming the LEDs using PWM, I came up with two solutions, and I was wondering if one was better than the other:

I can PWM the Output Enable pin of the shift register
I can PWM the supply VCC of the source driver

Which one, if any, would be best, and why ?


texts: Could you use a DAC to scale and modify an input signal?

texts: We are getting an input signal and need to modify it without changing the phase, would it be possible to do this by feeding it into a DAC through the reference voltage pin?


texts: How to get NodeMCU to detect an external switch closure of an unknown voltage?

texts:
I'm getting really into home automation as a side project of mine and one of the next things I would love to automate is my doorbell.

Short question: If I have a switch (momentary button in the form of an intercom buzzer) of an unknown voltage/current etc. how would I go about allowing the NodeMCU to read whether or not the buzzer has been pressed without risking frying the NodeMCU?

Long question: I plan to hook up my NodeMCU in some way to my intercom system so that when someone buzzes the door, it will send an http request to my Homebridge server which is running homebridge-http-motion-sensor, therefore allowing me to be notified as to when someone is at the door. I am capable of almost everything else including programming the NodeMCU etc. but can't seem to find anything online which tells you how you can get a NodeMCU to detect a switch closure on something not being run off the 3.3V out (i.e. something like this wouldn't work). Is there any sort of hardware out there like a reverse relay sort of thing which would allow me to do this?

If you would like a clearer picture of what I'm talking about; here is a rather poorly made diagram of mine which should allow you to get an idea of what I'm talking about:

I would really appreciate it if someone could give me some guidance on how to best do this.

Thank you in advance for any help,

Kind regards, John


texts: What is simplest way to convert digital signal 1 0 0 1 0 0 1 0 0 (i.e. 1/3 of time its ON and 2/3 of time its off) into sinusoidal signal of same frequency, which can vary from 3 KHz to 6 MHz?


texts:
I've looked at a dead power supply and see transistors, ICs, an optocoupler, etc and have come across what the board says are resistors[ R<#>].  Resistors that I've come across are the typical 3/4/5 band DC ones.  I'm guessing these are high voltage resistors though I don't know the real term for them.

Resistor 1 looks like a relay but with "0.18ohm", so it's a resistor.
Resistor 2 looks like a resistor but with none of the bands (which I guess comes with the territory of high voltage resistors).
The question I'd like to ask is are these actually resistors? And if so, what is the right terminology for these?  Furthermore, what are the differences between the two?  I tried testing them out with a multimeter and got really weird values.
1: while holding the two leads for resistor 1 and testing the resistance, I get 0.3ohms.  When I put it on the table and measure it, I get 1ohm].
2: while holding the two leads for resistor 2, I get 0.4ohms.  When I put it on the table and measure it, I get 0.9ohms.]
3: When I test for continuity, I get a beep for both resistors.
At this point, I'm terribly confused and am thinking I've been testing resistance wrong, or my understanding of resistance is wrong (or even both).
Or am I testing high-voltage resistors wrongly?
Can someone point out if I've done something wrong?


texts: Arduino Nano: How to decide voltage divider values that are safe for the input of the ADC

texts:
I am building a simple voltmeter circuit that needs to measure up to about 35 volts.  Looking around the web, I am finding all sorts of suggestions for voltage divider values, like 1 Mohm / 10 Kohm, and the one I am currently experimenting with, which is 10K/2K.  I am having issues with allowing enough time between readings for the Arduino Nano to settle down, of course, but that is not the question.  Using 10K/2K it maxes out at a reading of 1020 on A6 with an input of 27 volts.

I do not understand why one posting says to use resisters in the Mohm range and the other (that I am using) is a total of 12k.

Question:  Is there a rule of thumb that should be used to decide what resistances should be used for the divider for measuring this level of voltage?

And how important might it be to keep the resistance between Vcc and GND higher than what I am using?

--
EDIT:  EE asked me if this was the same as another suggested Q/A - and this is only different because it is specific to the Arduino's ADC input impedance.  The other answer only talked about the ratios.

The answers to this are great for my particular application.

--FURTHER EDIT:  Based on the collective berating from the powers that be, I would mention that this started in an Arduino forum where I was concerned about the particular ADC, then it got moved here.  Calling this a duplicate is incorrect.  It is very specific to the Nano application.  I wanted to make sure my small values wouldn't cause problems by being between Vcc and GND.  Plus, I did not know the proper input impedance for the Nano's ADC.  It all got answered here, nicely.

Thus I believe it stands as being unique here.  I can find no duplicates of this particular question.  Being marked this way with no explanation is frustrating.  If there really are duplicates then I would like to see their answers.  But finding none, this one adds to the community and I believe it should not be marked as a duplicate here.

And the good thing is that one respondent brought up smoothing capacitors.  So now I am using one, and it helps stabilize the readings.  So this has been a positive experience.

The problem now is that Arduino people won't necessarily know to look here for this answer when they try to use their Arduinos this way.  So there will likely be duplicate questions there which just got answered here.


texts: Why the speed and current will decrease when I change the connection delta to star on ac motor?but reduce motor voltage will have opposite result?

texts:
On the 3phase motor, The motor has been accelerated to a stable operating speed, then I reduce the line voltage -> speed decrease -> slip increase -> current increase -> the power will constant.
But I change the connection from delta to star -> the phase voltage decrease (380V -> 220V), the speed decrease to 1/3, phase current decrease to 1/root3, decrease to power 1/3.
Why the speed and current will decrease when I change the connection delta to star on ac motor,but I reduce the motor voltage will increase the current and speed?


texts: Is it safe to use a higher value capacitor?

texts: I am trying to replace a bad 820 µF, 6.3 V capacitor on my PC's motherboard. Right now I don't have a 820 µF capacitor in my home and also don't have enough time to buy a new capacitor. I have two 470 µF capacitors rated at 16 volts. The damaged capacitor is located near a RAM socket of the motherboard. Can I use a combination of two 470 µF capacitors that is almost 940 µF? Is it safe to use higher value capacitors in computer systems?


texts: How to connect 111ager Solid State Relay with Arduino to control a 5VDC@2.1A load

texts:
I just bought from ebay 111ager SSR 3-32VDC input power supply with load current upto 5A @ 5-220VDC. Link to the product: (https://goo.gl/MOkAU3).

I wanted to use it to control a 5VDC@2.1A load using Arduino UNO. I didn't connect any external component as I thought the SSR should do the task it is designed for without having to include external electrical components.

The code in the arduino puts high the SSR pin for 10 seconds and then turns it low for 5 seconds. I connected my smartphone (samsung galaxy S6) on the load side. And here is what happens: My phone just blinks without charging after each 5 second the SSR is LOW. The picture below shows the connection diagram.

My guess was that the phone is not getting enough current from the USB power supply as the SSR probably has higher resistance. But I don't know what I should do.  Any kind of comment/suggestion is quite welcome.

[PS: I connected the SSR input at 5V DC of the Arduino. The same things happens with the 3.3v of the arduino]

Look forward!


texts: How can 400V & 690V on e-motors result in the same power

texts:
Forgive my ignorance, but how can two 3-phase ratings on the same motor result in the same output power?

The one I have is rated for 0.7kW in triangle for both 400V and 690V.


texts:
Hi I am writing a code for image processing that includes a Ram to/from which data will be written and read. However, I am getting 15 errors like the one below.

[DRC MDRV-1] Multiple Driver Nets: Net address_ram[10] has multiple drivers:
address_ram_reg[10]/Q, and address_ram_reg[10]__0/Q.

I created this ram by using block ram generator in Vivado 2017.2. It is single port ram and initialized with some .coe file. My knowledge on rams is limited. What I know or what I strongly assume to be true is that when write_enable is 1, data will be written to the location described by the address_ram. Does not matter if write_enable is 1, data will be read from the location described by the address_ram. By the way, ram is always enabled.

Here what I have

I read in rising edge of the clock and write in falling edge of the clock in order to avoid some clashing.

Reading_from_Ram: process(clk) is
begin
if rising_edge(clk) then
if (pos_x < PICTURE_WIDTH_HEIGHT) and (pos_y <PICTURE_WIDTH_HEIGHT) and
(pos_x >= 0) and (pos_y >= 0) then
address_ram <= (conv_std_logic_vector((pos_x +
pos_y*PICTURE_WIDTH_HEIGHT),16));
end if;
end if;
end process;

Writing_to_Ram: process(clk) is
begin
if falling_edge(clk) then
if (pos_x < PICTURE_WIDTH_HEIGHT) and (pos_y <PICTURE_WIDTH_HEIGHT) and
(pos_x
>= 0) and (pos_y >= 0) then
write_enable <= '1';
address_ram <= (conv_std_logic_vector((pos_x +
pos_y*PICTURE_WIDTH_HEIGHT),16));
end if;
write_enable <= '0';
end if;
end process;

U4: Block_Ram port map(addra => address_ram,
                       clka => clk,
                       dina => data_in_ram,
                       douta => data_out_ram,
                       wea => write_enable);

data_out_ram and data_in_ram are used in changing brigtness and contrast.

U5: Brightness_Contrast port map(clk_in => clk,
                                 operation => operation,
                                 pos_x => pos_x,
                                 pos_y => pos_y,
                                 data_in => data_out_ram,
                                 cursor_pos_x => cursor_pos_x,
                                 cursor_pos_y => cursor_pos_y,
                                 length => length,
                                 output_of_operation => data_in_ram,
                                 mode => mode);

This is all I can say. How can I get rid of these errors??

edit:

Reading_Writing_Ram: process(clk) is
begin
if rising_edge(clk) then
if (pos_x < PICTURE_WIDTH_HEIGHT) and (pos_y <PICTURE_WIDTH_HEIGHT) and
(pos_x >= 0) and (pos_y >= 0) then -- if within picture
address_ram <=(conv_std_logic_vector((pos_x +
pos_y*PICTURE_WIDTH_HEIGHT),16));
if ( pos_x > cursor_pos_x - 1) and (pos_x < cursor_pos_x + length) and (
pos_y > cursor_pos_y - 1) and (pos_y < cursor_pos_y + length) then --if
within cursor
write_enable <= '1';
else
write_enable <= '0';
end if;
end if;
end if;
end process;

I rewrote it again(code above) and solved the problem.
Thanks everyone who helped


texts: Step up converter for electrical motor, 110V to 230V

texts:
Wasn't being careful when purchasing a vacuum pump for silicone de-gassing so I ended up with an american standard. (I live in sweden)
Tried to search this but with limited knowledge comes limited lingo and understanding.

Speccs on pump:
110V/60hz,
1/4hp (or ~186W according to google)

Speccs on wall plug:
230V/50hz

Is a 230->110V, 300W max, converter ok to use?
I read that as this is an electrical motor I should be very careful when choosing a converter to handle power surges/spikes, what am I worried about here?

3.Other than loosing some performance in going from 60 to 50hz, are there any other risks/drawbacks?

Cheers and thank you for reading!

Edit1:
link to product: http://www.amazon.com/Zeny%C2%AE-Single-Stage-Rotary-Vacuum-R410a/dp/B012CFTYX4

So far I've been unable to find more technical documentation for it, the manual doesn't seem to show any carbon brushes but there's a big capacitor attached. Guessing it's an induction motor.


texts: Why do we use FIFOs and RAM in an image processing scheme?

texts:
I found a cool project (https://www.youtube.com/watch?v=aGCcT7p0-wY&lc=) which I want to replicate.
This is the flow:
Analog camera
-> ADV7180 (it converts the video from NTSC or PAL to 8-bit BT.656 YCrCb 4:2:2)
-> BT656 decoder
-> YCrCb to RGB converter
-> Dual Clock FIFO
-> SDRAM
-> Dual Clock FIFO
-> VGA

Before replicating this project, I would like to understand the flow, so my question is:
Why this guy is using two Dual clock FIFOs and the SDRAM ? What's the purpose of using them?
Thanks in advance.


texts: How do I select the accompanying components for an optocoupler?

texts:
I'm using an optocoupler (MOC3021) to sense the On/Off state of an electrial appliance  using a microcontroller ATmega16L. How do i go about doing this? My mains supply specs are 230V, 50Hz. How do I design the surrounding circuit and select component values, like the resistors?

EDITED on 13th June 2012

Note: This is the first time I'm solving a circuit like this. Please send any helpful feedback. (including things I did wrong or any improvements)

Referring to the above schematic. The idea is to use this circuit to determine whether the load is on or off. The output pin from the optocoupler connects to an external interrupt of the Microcontroller I'm using which is ATmega16L. The interrupt will Monitor the state of the load. After monitoring I can toggle the state of the load using a relay (relay acts as a Control mechanism) which connects to the same microcontroller.

Now, I tried calculating the resistor values for R1, R2 and Rc.
Note, microcontroller's VIL(max) = 0.2xVcc = 660mV and VIH(min) = 0.6xVcc = 1.98V and VIH(max) = Vcc+0.5 = 3.8V.

To calculate Rc is quite easy. When the transistor is not conducting the output is high (at 3.3V). When the transistor conducts the output is pulled low. so from microcontroller's point of view, output high means load is switched OFF and output low means load is switched ON.

Looking at the datasheet for SFH621A-3, using 34% minimum CTR at IF = 1mA. Therefore, at 1mA input, the output is going to be 340uA. So in order for the microcontroller to detect low voltage from the output of the optocoupler can I use resistor value of 1Kohm? So that the output from the optocoupler will have a voltage of 340mV (which is below VIL(max))

More on this later, been a long day.

EDITED on 15th June 2012

Note: Solving for resistors on the power line (R1 and R2). Please check my calculations and any appropriate feedbacks.

Aim: the aim is to keep the LEDs *ON** for maximum period of time in a 10mS half period (20mS full period of 50Hz).
Lets say LEDs have to be ON for 90% of the time, that means LEDs require at least 1mA of current for 90% of the time for that half period which means LEDs will be active for 9mS in a 10mS half period. So, 9mS/10mS = 0.9 * 180(half period) = 162 degrees. This shows the current will be 1mA between 9deg and 171deg (and less than 1mA from 0deg to 9deg and 171deg to 180deg). Did not consider ON time to be 95% as working with whole numbers is neat and 5% doesn't make any difference not in this application at least.

Vpeak-peak = 230V x sqrt(2) = 325V.
Taking tolerances into account. Minimum tolerance of 6%.
325 x 0.94 (100-6) x sin(9) = 47.8V

So, R1 ≤ (47.8V - 1.65V) / 1mA = 46.1 Kohms
Choosing a value one smaller than 46.1 Kohms of 39 Kohms (e12 series).
Now that a smaller value resistance is chosen compared to what was calculated, means current through the diodes will be greater than 1mA.

Calculating new current: ((325V x 110%) - 1.25V)/39 Kohms = 9.1mA (too close to max If of diodes). Coming back to this in a moment [Label - 1x]

First calculate the power ratings of the resistor (considering 39 Kohm)
((230 + 10%)^2) / 39K = 1.64 Watts (too high).

Going back to calculation [Label - 1x]
Lets choose two 22 Kohm resistors. Together they add upto 44 Kohm which is quite close 46.1 Kohm(calculated above)

checking power rating of the two resistors combined:
((230 + 10%)^2) / (2 x 22) Kohm = 1.45W.
choose 22 Kohm resistors each with 1W power rating.

Now, after all this the initial CTR was 34% which means 1mA in will be 340µA out. But now because of 2x22 Kohm resistors the current will be slightly more on the output. That means higher potential across the pull up resistor Rc. Would there be an issue to get a volt drop below 500mV on the output of the optocoupler??


texts: I'm confused about how to calculate noise for an SNR?

texts: My Rx radio is getting -60 dBm but I don't know how to find the noise. My thermal noise is on the order of E-12 so it barely affects my SNR. Where does noise come from and how can I calculate it?


texts: Why does my voltage divider output seem to vary depending on the order of magnitude of overall resistance?

texts:
I'm working on a project where I want an Arduino Uno to measure the voltage of a 12V lead acid battery.

The Uno's analogue read pins can't handle raw 12V, so I need to use a voltage divider with roughly a 1/3 stepdown ratio to take the max 14.70 (while charging) down to 5V or less so the pin doesn't fry.

I initially built my divider circuit with R2=503K ohms, and R1 = 1M Ohms, which should give a Vout/Vin ratio of 0.334. I built the circuit and in practice I get a ratio of 0.252 or something like that (battery voltage is 12.97 and the divider is outputting 3.28V, all measured with multimeter.) 0.252 would be fine and safe enough for the Arduino, but I want to get as close to 0.334 as possible to get as much resolution of my battery voltages as the 0-5V of the analogue pin can give me.

I chose the biggest resistors I have because I don't want any more current than absolutely necessary to flow through the divider and get wasted as heat (also makes me nervous as a short circuit risk.) I do realize that this will make the current flow through the divider extremely small, something on the order of 10^-6 Amps. However this seems to be affecting the voltage that's produced.

I wonder if there is some sort of minimum current requirement for a multimeter/analogue pin to read a voltage correctly?

I've double checked the resistor values with the multimeter (within what their specs say they should be with 5% tolerance) and I set up an experiment that demonstrated the weird behaviour I'm seeing.

With R2=R1, I built two different voltage dividers, the first one with two 680K resistors, and the second one with 68K resistors.

The 68K divider gave Vout/Vin of 6.33/12.97=0.488, closer to the theoretical number I should be getting of 0.500.

The 680K divider gave Vout/Vin of 4.85/12.96=0.373.

What gives?


texts: Circuit for safety button which turn off relay power supply

texts:
I have safety button with 2m of cable which is normal closed. When somone push safety button, circuit should turn off 5V_REL section. But there is some noise envoirment, and I do not want to 5V and 5V_REL on button. Additionally I need to detect disabling this voltage on 3.3V level and I need LED on 2m cable which indicates that 5V_REL is off.
What should I use for that circuit optocoupler? or just RC filters.
Using MOSFET for disconnect 5V_REL?


texts:
I would like to power a large set of LED strips. Doing my calculation, at maximum output, I would require 120w at 5v. I am relatively new to electronics, so please excuse the noob question.

In my research, I have found significant limitations in what I am trying to do. I have not found a wallwart capable of doing this. I have also found that using voltage regulators will produce too much heat, and would be dangerous. I have been searching transformers, but I am not finding this much help either.

I have found, however, a 110 V converter switching power supply that is rated at 350w. I suppose this would be what I need to use. I can only find this on eBay or AliExpress. Using something like that direct from China makes me nervous. This will be installed in my house.

Could anybody please point me in the right direction? I am looking for theory, as well as safety information.

Thanks in advance.


texts: How to calculate equivalent resistance in mixed circuit?

texts: I don't understand is this paralel or serie, can somebody help me?


texts: What happens for DC frequency of a signal when frequency doubler is applied to a signal?

texts:
Suppose there is a frequency doubler that doubles frequency, non-ideally. I heard that frequency doublers cannot be applied to a signal with DC bias. I really do not get what this means, so the question.

What happens for DC bias of a signal when a frequency doubler is applied? Does it spread over, or does it keep its place at zero frequency?


texts: What do solid/striped lines on a wire indicate?

texts: What do solid or dashed lines on a wire indicate?  Is there a difference between the solid and dashed indicators?


texts:
I'm having trouble with a circuit I'm putting together. I think this is how to represent it (may be wrong about that).

I'm using a SPDT switch to turn off a circuit, but I want it to turn off after a delay. I have a 12v Delay Switch Ne555 Module that I switch on when MAG is in an NC state. This works.

The issue is the circuit is permanently on and never switches off. It seems like the timer fires immediately but never switches. The module makes a buzzing noise.

If I move the timer switch to the opposite leg the timer works - it turns off immediately and then turns on after a delay - the opposite of what I want. No noise is made.

simulate this circuit – Schematic created using CircuitLab

I think the diagram is slightly wrong - there isn't two switches inside the module. I just wasn't sure how to represent a timer switch that needed voltage.

What am I doing wrong?


texts:
I'm currently designing a single rail power supply audio amplifier and just wondering what the benifits are (if any) and if its worth including a film/poly capacitor in parallel with the large electrolytic capacitor.

This is an example:

In short, are there any advantages to the 10uF poly capacitor?
If so, what type would be best? MKP, MKS, PIO?


texts: How to drive LED when sinking current to MCU?

texts:
Hopefully a simple one.  Should I always control by writing to the GPIO digital output? Or should I always leave it low and then tri-state the output?

LED turns on when MCU pin sinks current:

In code, I mean the difference between the following for the given schematic:

// Control entirely via GPIO
TRISBbits.TRISB5 = 0; // configure as digital output
LATBbits.LATB5 = 0; // turn on the LED
LATBbits.LATB5 = 1; // turn off the LED

// Tri-state output to always just enable/disable
LATBbits.LATB5 = 0; // drive output low
TRISBbits.TRISB5 = 0; // turn on by configuring as digital output
TRISBbits.TRISB5 = 1; // turn off by configuring as digital input


texts:
I am trying to make a JK flip-flop in ActiveHDL environment.
I want to make it with logic gates.

It should look like this:

This is my code:

--nand3.vhd
library ieee;
use ieee.std_logic_1164.all;

entity nand3 is
    port(
    A,B,C: in std_logic;
    D: out std_logic
    );
end entity;

architecture nand3 of nand3 is
begin
    D <= not(A and B and C);
end architecture;

--nand2.vhd
library ieee;
use ieee.std_logic_1164.all;

entity nand2 is
    port(
    A,B: in std_logic;
    C: out std_logic
    );
end entity;

architecture nand2 of nand2 is
begin
    C <= not (A and B);
end architecture;

--JK.vhd
library ieee;
use ieee.std_logic_1164.all;

entity JK is
    port(
    J,K: in std_logic;
    Q, NQ: out std_logic;
    CLK: in std_logic
    );
end entity;

architecture JK of JK is
component nand3
    port(
    A,B,C: in std_logic;
    D: out std_logic
    );
end component;

component nand2
    port(
    A,B: in std_logic;
    C: out std_logic
    );
end component;

signal s1, s2: std_logic;

begin
    C11: nand3 port map(NQ,J,CLK,S1);
    C12: nand3 port map(Q,K,CLK,S2);
    C21: nand2 port map(S1,NQ,Q);
    C22: nand2 port map(S2,Q,NQ);
end architecture;

The problem is that i am getting this error when I compile JK.vhd file:

# Error: COMP96_0411: JK.vhd : (31, 22): Actual of mode "out" can not be assigned to formal "A" of mode "in"
# Error: COMP96_0411: JK.vhd : (32, 22): Actual of mode "out" can not be assigned to formal "A" of mode "in"
# Error: COMP96_0411: JK.vhd : (33, 25): Actual of mode "out" can not be assigned to formal "B" of mode "in"
# Error: COMP96_0411: JK.vhd : (34, 25): Actual of mode "out" can not be assigned to formal "B" of mode "in"

I think the problem is the backward signals.


texts: How do implement my pic24 onto a pcb board?

texts: I have a microstick development board for the pic24, shown here. The microstick contains many other components and parts other than the pic24 that are used for voltage regulating, debuggers, etc. In the project that I am working on, we will eventually need to just have a surface mount package of the pic24 and solder it to a pcb. Will I be able to just take the surface mount package of it and put it on a pcb and have it work or will I need to add the rest of the components that the microstick development board contains?


texts:
I've recently written a program to predict power density around antenna for compliance with radiation limits. One of the parameters required for the program is antenna transmit power. Antenna transmit power is defined as the amount of power radiated by the antenna. The transmit power is proportional to the input or consumed power of the antenna. Transmit Power=Efficiency*Input Power. Data sheets on antennas typically show the maximum consumed power per port but not efficiency. I realize power transmission efficiency is a combination of antenna eff., connectors losses, and matching impedance. It would be nice to know  if there is a way to estimate the antenna efficiency or transmit power based on the input power.  Also I assume an antenna wont operate at its full rated power at all times. So what influences how much power an antenna consumes?

Here's some relevant information I found:
https://www.mountpearl.ca/wp-content/uploads/2016/09/Compliance_SC6.pdf
I found a radiation compliance report. In their report on pg 13 they stated that they ran their simulation using a transmit power of 20W. I looked up the antenna datasheet and the max power per port was 250W-500W (depending on frequency)
https://www.scribd.com/document/370154811/ADU4518R9
So how do you think they came up with the 20W for their simulation?


texts: Arduino and embedded C programming in a windows based system?

texts:
I am currently using Arduino Ide to code my arduino but now i want to code my arduino in C/C++ and i dont know where to start from what is the best tools and tutorials suggested for this. I'm a windows 7 user but am very new to programming, much less embedded systems programming.

What do I need to do to start working in a real embedded programming environment? As Atmel's site is a bit daunting for a beginner...


texts: Is there any standard which defines that a particular connector or header on PCB has to be male or female?

texts:
Is there any standard which defines that connector (DB9, DB25, USB or header) type  has to be MALE or FEMALE while choosing one to use on circuit board?
 I am designing a microcontroller circuit board for general use.


texts: Help identifying this short, red antenna-like(?) structure

texts:
I saw this device along a trail while hiking in hills in the suburbs of Taipei. It sits on short legs only about 1.5 meters tall.

It has two attachments which appear to be thick cables but I couldn't tell for sure, the area is overgrown and behind a bit of a fence. These are the best zoomed photos I could get.

The exposed red cylindrical section in the middle appears to be made from some kind of dielectric insulator or maybe fiberglass, and I estimate it to be about 38cm (15 inches) long and about 10 cm (4 inches) in diameter.

If it were a base-loaded antenna I'd expect at least a little more radiator on top, and one coax instead of two cables. I don't think it's a red light either, it doesn't appear to me to be even partially translucent.

I've cropped the best view of the label. I can make out ingelva parafulmini and Varese Italy. The The part number is very difficult to read, and I've obscured the four digit serial number for a bit to anonymize the end-user. I don't know what this is nor whose it is, but it sets only about 2 meters off of a popular hiking trail and so it's at least not "top secret".

Spares: 1, 2


texts: Can a device with a single wireless antenna work as a repeater?

texts: Not sure where, but I encountered the claim that a device with a single antenna (e.g. laptop) can be configured as a wireless repeater. Is this true?


texts:
The datasheet for the chip TLC254 says that it uses a serial communication interface at the top of the datasheet, however, it has MOSI MISO SS CS and all the other SPI styled pins. Is it safe to assume that it is SPI or is it Serial? If it is SPI what Mode should I use since there is no mention of the mode in the Datasheet.
Datasheet: https://www.ti.com/lit/ds/symlink/tlc2543.pdf

EDIT:
Thanks for bearing with me for I am pretty new to Communication.
I now realize that SPI is a branch of Serial thanks so some awesome people here.


texts: What does the HP/kW power rating on the specification sticker of a pump mean?

texts: Pumps have power given as kW/HP on the specification sticker and also efficiency is mentioned on them. Is this power the electrical input power or mechanical output power? For example in this case is the electrical power used by the pump 3 HP/2.2 kW or 3HP/2.2kW / (0.4) ? Here 0.4 is the efficiency of the pump given in this sticker


texts:
How do I receive data with my stm32f4 board with a classic 433 Mhz receiver?

Arduino and Raspberry have their libraries to do such a thing. Do I have to implement it myself?
If yes, how do I do that?
My guess is to start a timer at 433 Mhz and read the value from the data pin in the interrupt method.


texts:
I am trying to optimize a design that does not meet the constrains.

I know that you can use Timequest Timing Analyzer -> Report Top Failing Paths to report the paths that have negative slack but it will only show the start and end node of the path.

How can I see the entire path?


texts:
I am a beginner with LED lights, but would like to use a 5mm UV LED to make a pendant with a small fluorescent crystal.
(This is what I purchased (https://www.amazon.com/uxcell-365-370nm-Ultraviolet-Electronics-Components/dp/B07XKPR25C/ref=sr_1_22?dchild=1&keywords=Uv+bulb+5mm&qid=1607026696&sr=8-22)).
I would like to create a very simple, very compact circuit with a coin cell (watch battery), and an on/off switch. What would be the easiest way to do this?
Also, would using 2 batteries fix the voltage issue?


texts: What causes a voltage drop at the input of this TL082CP Op-Amp?

texts:
I am breadboarding a circuit using a TL082CP Op-Amp, and I am reading consistent values with the multimeter.
The Op-Amp stage is powered with a single 9V battery, like this:

The Op-Amp stage looks like this:

However, a thing is making me scratch my head: If there is no input signal, I would expect to read around 4,5V at the non-inverting input and at the output of the Op-Amp, but actually if I measure with the multimeter the voltage between the + pin and the GND, I read around 2,5V, while the output is consistently at 4,5V.

Why is that?

I measured the voltage across the R4 resistor and it was 0V, so there must be no current on that; I tried to use a 10K resistor instead of a 470K, and then on the + pin I read around 4,5, so it must be that some sort of current is flowing at the input of the op-amp, and a bigger resistor just causes a voltage drop with that current. Am I wrong?

Is that current coming from the power stage or is it coming from the Op-Amp?

I also tried to disconnect the Op-Amp to see if the C5 capacitor was leaking, but it seemed to work fine.
I am kind of inexperienced with Op-Amps, and maybe I am doing a very basic error in measuring or breadboarding, but what confuses me is that the output of the circuit seems to be correct.
I would greatly appreciate your help.


texts:
I am currently reading Practical Electronics for inventors and am having a bit of trouble understanding the output of the following circuit:

Now as I understand, if Vin>Vref then the transistor should be switched on and conducting therefore Vout should be equal to zero. But here it is indicated as +5V

Would be great if someone could clarify.Thanks


texts: multiplex multiple photodiodes to one transimpedance amp

texts:
TIA = transimpedence

I have lots of photodiodes for barrier detection, I tested one photodiode with one TIA op amp, and it was OK

1) Now I want to multiplex multiple photodiodes for my project, and I use 74HC4051 IC for that, I read in datasheet that between each of inputs to output 60 Ohm resistor, what's the effect of this resistor ?

2) I read this application note for TIA pcb design, and in this article author implied that the photodiode should be as close as possible to TIA because of the very low current of photodiode and TIA input bias current, It's very good for one photodiode, But when I use multiple photodiodes, I'm forced to place some photodiodes far away from TIA (40 photodiodes), what should I do for this in circuit design ?


texts:
I am working on a project and I have run into a little bit of a problem.  I have a speedometer gauge that I am trying to send a signal to on a bench (out of car).

The way in wich the it works is pictured as follows.

One side is ground and the other side goes to the gauge as the sender.

So essentially what I need to do is create a circuit that simulates grounding the sender pin to ground at a high frequency with a square wave and 50% duty cycle.

I thought about using some sort of relay and turning it on and off really fast but that probably wont be fast enough and will probably wear out the relay really fast.

I would like to be able to use an Arduino to accomplish this.


texts: Negative current through capacitor on multisim simulation

texts: I am learning about capacitors and decided to run a simulation on Multisim to understand them a bit more. Whenever I connect the capacitor to a DC source and connect an ammeter the result is quite high negative current. What is the significance of this? and why would it happen since its supposed to be no current at all since dV/dt = 0?


texts: Purpose of high pass filter for AC Mains?

texts: I wanted to ask what the purpose of the high pass filter does in the below circuit. Is it necessary?


texts: Minimum energy required for LED blink to be visible

texts:
I have a 5V schematic with 15n capacitor and I wondering if I will be able to blink an LED, powered from this capacitor. My calculations is that the capacitor will have about 0.2 uJ of energy. This I could convert to approximately 100 uSecs of 300 uA current.

So the questions are:

What is the minimum energy (energy, not power, as I need to have a visible blink, not constant light) needed to make LED blink visible in ordinary office circumstances (OK, I will cover LED with my palm to avoid direct light exposure :-D)?
Is it important how I will distribute this energy in time?
Is there any color difference (maybe there are any human eye response difference)?


texts:
The loss of electricity in transmission and distribution is only 6%, so why is it that electric heating is so inefficient?

I would imagine that the generators at power plants are far more efficient than any engine you can put it in my house for heating, and I also assume there is very little energy loss from going to electrical energy to thermal energy (if not, then where does the energy go?).

Where am I going wrong in my thought process?


texts:
I would like to build simple and small power supply for my projects with microcontrollers. This supply should be powered by two Ni-MH batteries and output should be 5V (maximum current 500mA).

I know there are plenty of them on the Intenet (MintyBoost from Adafruit and cheap ones from China on eBay) but I want to build one by myself.

The LTC3400 looks very good but not cheap. Do you know any other step-up converter (Vin 1.8V and less, output current 500mA and more)? By cheap, I mean circa $1.


texts: What's the third footprint pad on some SMD LEDs for?

texts:
This has been asked, or brushed by before, but not really answered, for instance, here:
SMD LED footprint

I still don't know what the 3rd footprint pad for some SMD LEDs (like the Vishay VSMG10850; the red bit in the image) is for, do I need to add one on the board, and if so, do I leave it unconnected, connect it to the GND for instance, or what?

Some of the explanations mentioned it might be for heat dissipation. If so, how should it be connected to anything larger than the small pad for actually dissipating some of the heat? Another guess is that it has to do with just mechanical attachment to the board, especially for automated layout hardware.


texts: Equivalent Inductor Equation (Antoniou Gyrator Proof)

texts:
I've been working on a proof for University and I've been able to understand most of what I was asked, but I'm having trouble understanding why is it that the equivalent inductor in an Antoniou Gyrator has inductance L = (R1*R3*R5*C4)/R2, referring to the image below.

I've understood the parts of the proof concerning the differentiator and the operational amplifiers and I have almost closed my reasoning, but I don't precisely understand why that equation works out to be that way. From what I've understood, R5*C4 is the gain of the differentiator, but other than that, I don't know where the equation comes from.

Can you guys help me on this? Any tips?
I looked at the other question on here about this type of gyrator, but it didn't answer my specific question. Thank you!


texts: estimating cutoff frequency from magnitude of phasor transfer function

texts:
Given the magnitude of a transfer function for an RC high pass filter:

$$|H(\omega)| = \frac{\omega RC}{\sqrt{1+\omega^2 R^2 C^2}}\tag{1}$$

The textbook say:, "we take a digression to learn how to estimate the cutoff frequency.  This occurs when |H| is at half of its peak value, that is:

$$ \frac{1}{\sqrt{2}} = \frac{1}{\sqrt{1+\omega^2 R^2 C^2}}\tag{2}$$

I'm not sure I understand this statement..  how is:

$$\frac{1}{\sqrt{2}}$$

half of the value of:

$$|H(\omega)|$$

anyways, if you solve the equation (2) you get a cutoff frequency of:

$$2 = 1 + \omega_c^2 R^2 C^2$$

$$\omega_c = \frac{1}{RC}$$

textbook continues: "so by tuning the values of resistor and capacitor, we can contrutruct a high pass filter with the desired cutoff frequency..."

I could brute force it and get the cutoff frequency by plotting the magnitude function with matplotlib...but i though it would be useful to know how to estimate it from the magnitude of the transfer function...


texts:
I would like to understand how to handle digital voice on gsm modules.

After reading 3gpp gsm mux 07.10 specification it is my understanding that gsm modules can be configured to transport voice frames on dedicated channels (DLC) sending a SNC frame with bit3 set on.

I considered to use simcom sim900 module but official documentation indicates that SNC frames are not supported.

Are DLCs channels the right approach to send&receive voice frames?
is there another way to do it (PCM, PWM, I2S interfaces)?


texts: Flip Switch with transistor and push button

texts:
Sorry if this is a duplicate, I don't know the actual term for what this is called.

I am trying to create a circuit where the push button will switch the current from Red LED to Blue LED on right. Currently the blue LED lights up but Red one doesn't go off. I know I am missing something small which is apparently big enough.

What am I missing?

Resistors:
LEDs: 200 ohm
Transistor Base: 1K

Working Voltage: 5V
Transistor: Generic NPN

Simulation of the circuit below


texts: How can I attach a custom built antenna to the NodeMCU (ESP-12E)

texts: Is there any possibility I can disable/remove the PCB antenna and replace it with a custom one, like a directional helical antenna? Can I just solder it on? I am an absolute beginner and have no real idea of how this works.


texts: Using Electro-galvanic_oxygen_sensor ; Oxygen concentration varying b/w 19% to 30% for ambient air (which should be 21%)

texts:
We are using Oxygen sensor from SGX Sensortech. The datasheet link is attached here. [link].
We are using ARM Cortex-M7 core. The ADC voltage range is 0-3.3V, it has 12 bit ADC.
We are using OPA388 (Zero-Drift, Zero-Crossover,) operational amplifier from Texas Instruments in the non-inverting configuration. We have selected the gain of 40. The circuit is shown below.

The sensor gives output of 9-13mV for 21% O2 concentration, which translates to ca. 45mV - 65mV at 100% O2.

Experimental value:

Voltage from the sensor 10.2 mV. After amplification from Opamp we are getting 0.405 (405 mV). The gain of the amplifier is set at 40.
In the program we are getting variation in the oxygen concentration from 19% to 30% (it should be 21%).
We are using a shielded cable pair and our wire length is one meter from sensor to the controller.

The logic of the program is:
First it will measure the mV at 21% stores the value ; the voltage from O2 sensor vary linearly from 21% to 100% of O2 concentration.

We are planning to moving avg filter or Kalman filter to reduce variations.
Any recommendations, mistakes in the above logic/ circuit.


texts: Eliminating mains hum from frequency modulated RF LC oscillators

texts:
I'm trying to build a frequency modulated LC oscillator but all circuits I've tried have terrible mains hum after demodultaion.

The oscillator is tuned by capacitive sensor but I'm using a fixed capacitor instead until I solve this problem. I've tried different topologies: Franklin, Clapp, Vackář, Hartley at different frequencies from 60 to 500 MHz but there's no difference between them in terms of mains hum. I'm using an SDR receiver for demodulation, it works fine and cannot be the source of hum. Using battery instead of AC supply didn't help. I`m using 10 µF and 10 nF capacitors for decoupling. Using physically smaller inductors helped a little, but the noise is still unacceptable.

As suggested in comments, I've tested all circuit nodes with and without powering the circuit and 50 Hz component appears only at the antenna output.

Here are some PCB drawings, maybe there are mistakes in routing?

Fig. 1: Vackář topology, the transistor is BF545C

Fig. 2: Franklin topology, both transistors are ATF-38143

[UPD:]

Uploading my setup and schematics as requested. The setup is just an SDR receiver and the oscillator with a piece of wire at the output as a makeshift antenna. The capacitive sensor Cvar is absent, as I'm using a fixed capacitor C4 instead.

Fig. 3a:

Fig. 3b:

Fig. 3c:

[UPD2:]

SNR at 50 Hz is 4.3 dB. Maximum frequency deviation for Franklin oscillator is 290 kHz, output power is 7.8 dBm, received signal level is –26 dBFS. Grounding the laptop makes no difference.

[UPD3:]

I've made a new board with a ground plane and a nickel silver EMI shield. I've added a 1.8V LD1117 regulator and 100pF and 390pF NP0 decoupling capacitors — and still no luck. There are no significant changes in the noise performance. Unfortunately, I couldn't find an iron box to put the whole circuit in, but I'm almost sure there are some clever circuit and PCB design techniques that do not require magnetic shielding. For example, I've tested the SDR receiver on a cheap unshielded FM transmitter: there's no hum at all, even with the volume maxed out, so the culprit is definitely the circuit and PCB design.

Here are some photos of the board (sorry for the flux, I did try to remove it but failed)

Fig. 4a:

Fig. 4b:

Fig. 4c:

Also, as suggested in the answer below, I've recorded an IF from my SDR receiver and generated its spectrum at low frequencies.

Fig. 5a: Without the EMI shield

Fig. 5b: With the EMI shield

[UPD4:]

Now that is interesting.

Increasing C4 (see Fig. 3c) reduces the noise significantly. Look at the demodulated signal spectrums (the 440 Hz component is a test signal recorded from the sensor for SNR measurement):

Fig. 6a: C4 = 1.5 pF

Fig. 6b: C4 = 2.7 pF

Unfortunately, I've got no other capacitors in the range between 1 and 10 pF to make further tests (the oscillator won't start with C4 ≥ 10 pF). I guess that the AC line noise picked by PCB traces and L2 changes the gate capacitance of J1, and increasing the value of C4 reduces the influence of those changes on frequency. This is also confirmed by adding a strong noise source, e.g. a cell phone making a call. You can see large spikes on Fig. 6c and the frequency does actually increase when I add a noise source, meaning that the gate capacitance of J1 is inversely proportional to voltage. Makes sense to me. Seems like I need to either reduce coupling between J1 and LC tank or add some high-pass filtering between them, but I'm not sure what the best way of doing it is.

Fig. 6c:


texts: Sequence diagram, having hard time to understand how to interperet question

texts:
I have to construct a sequential circuit:
We have input x0 and x1
If the following sequence is done, then we want to open a lock, represented by lighting up an LED:

x0 = 0, x1 = 0
x0 = 1, x1 = 0
x0 = 1, x1 = 1

The lock shall remain open until we get x0 = 0 and x1 = 0 again, where we will return to the starting stage and new tries to open it can be made again.
We also have an async reset that will make it so that we return to the starting stage and the whole sequence will have to be done again.
I made the following 2 sequence diagrams, I am leaning more towards the second one being correct because of the async reset, right? Because the async reset only resets the D flip flops and not the input, if we were to reset when we currently have x0= 1, x1 = 0, then we would get problems if we were to use the solution in the first diagram, right?
The circuit is supposed to be a Moore circuit.