texts:
I’ve been making LED Neon Flex signs and I’d love to eventually sell them on, but I’ve started looking into CE testing/LVD and it’s looking like a minefield. Wondered if anyone knows the best way to go about it - It looks like you can self certify LVD/CE but there’s also companies offering it online - but would personalised signs need testing again? Seems like it’d get quite expensive! Also, if it’s built with plug and play components would it need testing  at all?

Sorry if my question’s a bit muddled - I guess I’m wondering if there’s a guide for dummies, or if anyone has been through it and has any advice. Thanks in advance!


texts:
In the following circuit, one could use a simple KVL to calculate that the voltage across the resistor equals 10V, and therefore the current flowing in the circuit is 1A, from the right side to the left side of the resistor.
This then shows that the power delivered by the right voltage source (using the passive sign convention) is P = -VI = -(20)(1) = -20W = 20W delivered.
However, when moving to the left voltage source, and still applying the passive sign convention, since the current enters the positive terminal, the power of the source is P = VI = (10)(1) = 10W = 10W absorbed.
We have faced this situation often in my current circuit analysis course. My question is - how is it possible that a voltage source has a net absorption of power? This just doesn't make any logical sense to me. If its a source, why is it absorbing power?

simulate this circuit – Schematic created using CircuitLab


texts: How to calculate the range of change of a Local oscillator

texts:
I was solving exercises from a book to prepare for exam and I found a question like this:
Determine the range of change the LO frequency and I have frequency of IF and RF ranging from 890-960 so what I did is calculating f(lo1)=890-f(IF) and f(lo2)=960+f(IF) and then from the results It ranges from  820 to 1030

second question was: Determine the value of frequencies before IF filter
so I calculated
f(lo1)=820
f(lo2)=1030
f(lo3)=960
f(lo4)=890

is what I'm doing correct or false?


texts: Voltage comparator - how to get a stable voltage reference from a battery

texts:
I'm trying to build a circuit which will be used to monitor the voltage of Li-ion battery. The voltage comparator I'm using is LM393.
Since the whole circuit will be powered by, it the battery will be drained and would not stayed at the constant voltage. The battery stays at 4.2 V when it is fully charged. I want to put the reference voltage at 3.7 V and the actual voltage of the battery at V(in).
I tried to put a voltage divider at the reference voltage but cannot find the resistor values which will satisfy this case.
How do I build the circuit so that the ever changing voltage of the battery gives a stable constant value at the reference node?


texts: How can I evaluate a bond wire's effect on high-speed signal integrity

texts:
I am currently getting involved in one PCB design which is associated with high-speed signal(40Gbps PAM4 signal).On the board,a chip which transmits and receives data is bonded and transfers data through the traces and connectors.

I know signal running at such speed is susceptible to skin effect,dielectric loss and reflections.I have also heard bond wire should be as short as possible to reduce its inductance,so I try to place those pads(also known as gold fingers) of high-speed signal really close to the chip(as 7,8,13,14,17,18,20 shown in 1).

My questions are:

(1)Is the length of bond wire shorter,the better?What is the theoretical basis?

(2)Can I pick up the best bonding wire length based on simulation result?What simulation tool should I use?(HFSS,ADS maybe?)

(3)In some article,bond wire is treated as transmission line.But isn't this too short to be modeled as?Is this a good approximation?

(4)Except from bond wire length,what are the design considerations of pad(gold finger) size?

Any insightful answer of any one of the questions will be appreciated,thanks!


texts: amplifying out signal of germanium diode

texts:
Hello
Dear All.

Please see the attached pic. As you see i have used a germanium Diode and am going to drive to a logic gate (74hc14N). But the forward voltage of diode is 0.3v, whereas the 74hc14N can't active with it! So i have to amplify the signal, please guide me.
Thanks.


texts:
Edit/added - RM: See Karl's prior question of December 20th last DS1822 1-Wire Sensor, Parasitic Power, and Strong Pull-Up Circuit which gives a very clear explanation of what he is actually trying to achieve. The following material is related to his attempt to understand the high side strong-pullup requirement of the IC concerned.  < /edit >

I have been looking through many of the posts with MOSFET in them, but can't seem to find exactly what I'm looking for. Apologies in advance if this is a common or duplicated question.

I have obtained an N-Channel MOSFET (IRLB8721PBF-ND) (http://www.irf.com/product-info/datasheets/data/irlb8721pbf.pdf) to use as a logic level MOSFET.

To test out the behavior I'm expecting to see with a 3.3v MCU, I hooked the Gate to a 3.3V power source with a 10k ohm pull down resistor. Drain was hooked to the same 3.3V power rail and Source connected to a 360 ohm resistor running through an LED to ground.

The behavior I saw regarding voltage was not what I expected. It seems that the voltage measured at the Drain is 3.3V (expected) and at the Source is 1.65V (not expected).

Disconnecting the LED and current limiting resistor brings the Source to 1.93V.

What I am attempting to determine is if the 1V+ voltage drop I'm seeing is due to the MOSFET's diode forward voltage maximum of 1V, or if there is something else at play here.

The intention of using the MOSFET is ultimately use it to directly connect a parasitic 1-wire device to the power rail during current intensive operations to retain the needed ~2.8V level.

This shows me that the setup I have now would not work. If my assumption is correct, do 'logic level' MOSFETs exist that have an almost negligible forward voltage drop?

If my assumption is incorrect, then perhaps I've wired something incorrectly and this setup could still work.

Additionally, I've seen recommendations to place a current limiting resistor between the MOSFET Gate and an MCU pin to avoid high current levels that may come back through. With the already existing 10k pull-down resistor from the gate, would this not create a voltage divider? I believe that's the behavior I saw at one point earlier in my experimenting.

edit
This schematic shows a modified circuit based on the request to move the LED and resistor to Vcc and the drain.  Originally, they were both located between the Drain and ground. I guess at this point I have some confusion over high side / low side and why this now works. My actual intent for the circuit is to use the same schematic but instead of an LED/Resistor, the MOSFET will be used to provide increased voltage for an open drain port on an MCU connected to a 1-Wire parasitic device.

Here's the schematic I'm ultimately aiming for with the MOSFET.  It comes from from Maxim's own datasheets.


texts: How to turn off 555 Timer for a period of time after Vout signal passes through

texts:
I have a single-shot 555 Timer. After triggering, output goes high for a period of time.

What I would like to do now: After Vout goes high and then low again, I want to disable the 555 timer for a period of 10 seconds. During this period, if trigeer signal is activated, it would not set Vouth high.

My theoretical idea is to delay a trig signal for a length of anticipated Vout (50ms-100ms). This delayed trig signal would go to Trig pin of another 555 Timer. This timer would generate Vout2 10s long. Then, I would add a MOSFET - Drain to Reset pin of first 555 Timer, Source to GND. Vout2 would be connected to gate, and on activation it would pull Reset of first 555 Timer to GND and disable the circuit for 10s.

Problem with circuit: How to delay trigger signal?

Other suggestions also welcomed.

Thanks.

Thanks!


texts: Function Generator amplifier to drive resonance circuit help

texts:
I have a model resonance circuit that is excited with an auxiliary winding and I need to build an amplifier to be able to amplify the current from the function generator in order to drive the auxiliary winding. I have used an OPA548 in Multisim in order to amplify the generators signal by a factor of 3 and it is current limited to an amp. However when simulating I am getting unexpected outputs across the auxiliary winding (7mH inductor) and I do not know how to resolve this or if this is just a multisim error.

Here is the resonance circuit.

Any help would be appreciated, I've never had to make an amplifier for an inductive load before so i'm not sure what I have to account for.


texts: Newb question: Is it OK for the outside of my power supply to touch these metal brackets and screws?

texts:
This is a newb question regarding safety...

I am using a piece of wood to hold a few electronics boards in place physically. I want to use these metal L brackets and screws into the plywood to secure them.

Is this safe? I know about metal-touching-metal probably isn't good, but nothing too specific. What kind of considerations should I worry about?

Picture below

EDIT - datasheet:

http://www.omc-stepperonline.com/download/pdf/S-350-60.pdf


texts:
So my buddy brought me his Kawasaki Ninja service manual and asked me what this symbol is - sort of looks like part of a diode with a box instead of a line and is half shaded. I've tried looking it up but haven't had any luck and in the context of the diagram not a ton of things make sense. My best guess is they're connectors?

Also in the legend BK is black, Y is yellow and G is green.

Anybody know what these are?


texts: Conversion of a Cold Cathode kit to work outside a PC

texts:
I have something similar to this Kit

Now I want to run this off the mains so I will be purchasing a 12V transformer plug. Something similar to this

Now my issue the inverter(blue box) takes in some odd connection a two/two pitch connector. I could simply cut the molex connector off this and solder on a connection which would allow the Transformer to be plugged into this.

I'm asking this question with just a vague idea that this will work. I want to know a few things.
Is my logic correct?
What are the risks with this approach?
Am I making a mountain out of a molehill, is there a more obvious cleaner implementation which would yield the same perhaps better results.

Thanks for reading

Edit

This is the Connection to the inverter

This is a powersupply unit I have have found which may do the job but low Amp output so not sure.

A list of the specs from the kit.


texts: I had seen that flip flop have two stable states 1,0 and 0,1 as output. Why are 1, 1 or 0,0 is not a stable state? Or what do you mean by a stable state here?


texts: surface/external edge coupled microstrip vs (internal) asymmetric edge coupled microstrip

texts:
In the process of determining the track width/separation of differential pairs for a board design
that needs to route usb2, pcie(90R) , gigabit ethernet(100R), CSI/DSI(100R), HDMI
im looking a a four layer board with a stackup of
GND
PWR/Signal
PWR/Signal
GND

euro circuits does an impedance controlled stackup, based on is400, of
copper
prepreg PR2116 0.12mm
copper (35 um)
Core fr4-improved 1.2 mm
copper (35 um)
prepreg PR2116 0.12mm
copper

i can calculate the pairs using https://saturnpcb.com/pcb_toolkit/
i can't find a second calculator for (internal) asymmetric edge coupled microstrip
or the actual equations for them
im trying to understand why when moving a track from surface to internal the track separation
has to increase to get the same differential
e.g
Target 100R
surface
W = .125
S = .2
H = .12
zDiff = 95.457
internal
W = .125
S = .787
H = .12
h2 = 1.2
zDiff = 95.463


texts:
I'm trying to design some sort of arc suppression for a relay under short circuit when tripped. So i'm trying to understand how these arcs form. From my understanding, at the instant of tripping, the relay contacts instantly changes its voltage to the supply voltage. Since the switch takes some time to fully open, E = V/d, and we have a very small distance (at instant of tripping) with a very large voltage (230 V AC rms in my case). The electric field is so high that it causes breakdown of the air and a conduction arc forms.

Correct ?

So my main goal is to reduce the dv/dt across the switch which will reduce the electric field and prevent breakdown ?

How can I prevent or suppress the arc from forming ?, will a snubber across the contacts work ?


texts: What is the output impedance of HF power amplifiers?

texts:
In case it matters, let's discuss solid-state, linear, class AB amplifiers operating below 50 MHz and on the order of 100 W.

Here's my confusion: I'd think ideally, the output impedance of the amplifier would be 0Ω, or at least as low as possible. This would minimize loss and the load impedance wouldn't matter much.

Yet, datasheets for these amplifiers almost always specify the output impedance as 50Ω. Sure, this means any reflections from the load will be absorbed in the source, but for HF and the kinds of things usually transmitted on HF (AM, SSB), reflections will not appreciably distort the signal.

I would think any kind of resistive 50Ω source would mean the amplifier efficiency can't be more than 50%. The 50Ω source could also be realized with reactive components which would improve efficiency, but preclude usage on multiple frequencies.

So what is the output impedance of a typical amplifier of this sort, and why?


texts: Transformer basics: Why don't they shift phase by about 90°?

texts:
I learned that current is induced in a conductor by a changing magnetic field.  According to this, it would follow that the secondary voltage (sinusoidal input) of a transformer should peak when the primary current is changing fastest — that is at the zero crossing.  It doesn't.

My question is: Why aren't primary current and secondary voltage out of phase by about 90°?


texts:
I am using a tracer battery BP2603(12V,3.5A) to turn on my camera. The camera needs 12V and it consumes max 3A. Maximum voltage the camera can accept is 13.5V. But I've found that when the battery is fully charged it has a voltage of approx 13.7v and it is not able to turn on the camera. So I need to drop approx 0.2V-0.3V to turn on the camera. I had a thought to use shunt resistor but the power dissipation is nearly 1W. The second option I thought about using a voltage converter. Is there any other way I can drop 0.2V-0.3V? Please let me know if there is any other way.

Thanks in advance


texts:
I am asking you how would i be able to implement a multimodel system using RC filters.I need a nonlinear model and my teacher told me to use RC filters.By using  a RC filter i get a first order system and i would need a switch that would add to the circuit another RC filter which would make the system a second order.
I would then use my development board and implement 2 PID controls that would commute depending on the situation.

I am not sure about the electrical design still.
Any ideas?


texts: Calculate C and R in a CMOS Crystal Oscillator

texts:
I stumbled over this simple solution to drive a crystal oscillator, but I need to connect a 25.17MHz crystal instead of the 10MHz in this schematic. How do I calculate R1 and C for a given frequency f(max)?
If C is taken from the crystal's datasheet, how do I calculate R1 then?

simulate this circuit – Schematic created using CircuitLab

I'm going to use this as a VGA pixel clock driving a couple of counters. If anyone has an even simpler solution, it's mostly welcome.


texts: How to use MAX7219 with high current LEDs

texts:
I am fairly new to electronics. I am using the MAX7219 to control an led matrix and the data sheet for the MAX7219 says that the maximum current each light can get is 40mA, but for my purpose I need 70mA for each light. I am using an Arduino to control the leds and the max pin output is also 40mA. The basic schematic for how I have the matrix set up is here:

Is there an easy way using transistors or something that I can get the higher current leds working with the lower current control?


texts: Replacing 28.8Mhz TCO with up-converted GPSDO 10Mhz signal?

texts:
Would it be possible to design a circuit that could replace
the TXCO (28.8Mhz) of a RTLSDR dongle by replacing it with a signal generated
from a 10Mhz reference signal, coming from a GPSDO?

And what kind of components could do the job?


texts: Is there anything like spring steel hold-down probes to help with SMT assembly?

texts:
I occasionally do minor SMT assembly and re-work. I know the standard practice for holding parts is to glue them, but sometimes I'd like to have a more temporary approach. For example, sometimes I need to build an assembly of several SMT components connected in "free space" to wires without being on a board.
My binocular microscope has a couple of spring-steel "tabs" that can hold the board, but are to big and too short to hold components. (see image below)
Does anyone know of if something exists like hold-down probes made of spring steel or piano wire, that would be small enough to hold down a component or package while soldering (without gluing it?) and thin enough to not get in the way of soldering small resistors or diodes?
I thought this would exist, but maybe I don't have the right term to search on. I'm imagining something like the "catwhisker" probe from early crystal radios, but larger.
Example of tabs on my current microscope:

Example of cat whisker for crystal radio:
(Image no longer available.)


texts: Meggering Three Phase Motor (Phase-GND, Phase-Neutral, GND-Neutral)

texts:
When meggering a three phase motor, could someone please help me understand the values we would expect to see for a motor with no insulation or ground faults.

From my understanding:

Phase-GND: should see a very high resistance (in MegaOhms)

Phase-Neutral: should see a very low resistance (near zero) since all the phases are tied together at the neutral

GND-Neutral: honestly I'm not sure...


texts: Slewed fpga drive rise time on pcb to enet phy

texts:
What can cause rise times to be slewed from an fpga to an enet Phy? Can it be trace capacitance?

This is a high density 14 layer board . Traces route from fpga to ribbon connector, along a short ribbon then along a second pcb up an Ethernet phy running at Gb enet using rgmii.

Using matching resistors driving side of the ribbon. 10bt and 100 bt work with some packet loss but Gb does not work . the rise times refardless of fpga settings the rise and fall times are slewed .  So much do the sample and hold times for Gb enet can’t be met.

I have redesigned ribbon rather than all data to be gnd sig gnd sig gnd sig etc etc.
Taking ribbon off or testing board with hard connections I still have slow rise times.

My gnd floods are 0.1mm or less from all enet signal lines and vias both sides. Could this add capacitance? Maybe vias?
After solving this problem how do I si simulate the ribbon?
Thanks.


texts: Replacing SMD Fuses without access to schematics

texts:
I'm curious to know if there is a sane way to determine the specifications of a blown SMD fuse without resorting to manufactures schematics / repair manuals.

In my particular case there are no obvious markings on either the board or the component (naturally).


texts:
I'm working on a project that powers 20 LEDs with a 9 volt battery. What gauge of wire should I use?

A couple of LEDs are in series with a 180 ohm resistor. Then each pair are in parallel.


texts: If voltage is measured between two points on a wire, with no resistance in between is the voltage zero?

texts:
I have a series circuit. Let's say the battery has a potential difference of 10 Volts.

On two points of the wire before the current hits any resistors, I attach the readers of a voltmeter. Since there is no resistance, and the formula for voltage is V = IR, does this mean that the voltage would read zero in between those two points?

But how can this be - we know there is 10 volts of current flowing through!

The example my teacher gives is that electricity is like a running river. The voltage is the force of the running water. Pile rocks in middle of the river and this is the resistance. But if you don't pile rocks and measure at two points, that doesn't mean that there is no power (read: voltage) in the river's flow.

Can someone please clarify?


texts: Split wires for the purpose of measuring high currents

texts:
According to I need an amp meter that requires no splitting of the wires there is an accessory that splits wires for the purposes of measuring current.
From the looks of the device it's limited to 110V/15A circuits (or maybe 110V 30A at most).  I need something like that but for higher amperages.
I would like to do the same thing but for the following types of circuits

30 to 50A 208V attached with twistlock adapter
20 to 50A 208V to 480V permanently installed by qualified electrician but safely accessible by anyone to clamp onto with amp meter

Is there a plug-in solution at these higher currents?  Or better yet for case 2) could this be improvised asking the electrician to split the wires by means of a junction box?


texts: Can I drive a BLDC driver with this diagram?

texts:
I'm a programmer and I've only started messing with hardware half a year ago, mainly with the Raspberry Pi. I now want to drive a brushless DC motor using my Raspberry pi. To do this, I've bought this BLDC motor driver (it's still on its way) which comes with the following diagram:

From this image I understand that I need to provide 5 different inputs to the driver (SV, COM, F/R, EN and BRK). And here's where I think I get into trouble, for two reasons:

the SV requires an analog input, but as far as I know the Raspi doesn't have an analog GPIO pin.
All these inputs require 5V, while the Raspi GPIO pins only supply 3.3V

So first question; am I correct in these problems?

I guess I can overcome these problems as follows:

I could use either PWM or a DAC as described here for the analog input, but since I want the motor to always run at top speed, I guess a simpler solution would be to always power the SV with 5V. Am I correct in this?
To power the other ports with 5V I could use opto-couplers in combination with the 5V powered GPIO pin to supply 5V to the other 4 ports.

So I created the following drawing:

Using the above diagram I guess I can power all those 5 connections on the motor driver with 5V and I can turn them on and off programatically using the regular 3.3V GPIO pins.

But since I'm really a beginner: does this make sense? Do you think this will work? Won't it damage anything?

All tips are welcome!


texts:
I am a mechanical engineering student and i need to measure electrical output. I have some voltage and current measuring instruments. I used them to measure the voltage & current of a blower(resistance heater).
The results were 3 ampere and 155 volts. But the appliance is rated at 2kW. So according to the formula, P=VI, the load of the appliance should be 155*3=465W. Why does this deficit exist between the rated power and the one i measured. Do i need to introduce power factory in the P=VI equation?
Someone told me it involves the concepts of apparent power reactive power, real power. If so can someone please explain those terms to me in a  simplified manner, my knowledge of electrical engineering and circuits is poor.


texts: what is meaning of wavelength in very short conductor length

texts:
I know the wavelength is distance between 2 point of maximum sine wave.
when the conductor length is very shorter than wavelength, what is meaning of wavelength? ??(how long distance propagate in short length? ??)


texts:
I am still unsure about connecting two DC-DC converters to achieve a higher output voltage. Regarding my question about this DCDC converter. The answer I selected does not work when no load is connected, and therefore I want to use the answer below but I do not fully understand it.

Would connecting "Common pin" with Vout+/ Vout- via the load resistors not short the connection I want to make and only produce +15V/-15V between my ground?

If this schematic is correct, can I still produce the +15V/-15V between the midpoint of the circuit?

EDIT: After the comments I changed my schematic

Am I correct, that the COM+ are now the GND connection for my devices that need +15V


texts: RS485 minimum node spacing - 3 x RS485 device on PCB

texts:
I would like to ask something about RS485 minimum node spacing which is described in (Page 5)

TI Design guide

I would like to create device which consists from 3 existing RS485 devices. My plan was that I put these 3 devices together on single 2 layer PCB and connect them via single RS485 line (A, B). According to material above this shouldn´t be a good idea because there will be very small length traces between these devices.

Do you have any experience with this approach of placing more RS485 devices on same board?
Is there any technique which could help the signal integrity?

Thanks


texts: Bypass Gate-to-trigger-converter via switching jack

texts:
Goal

I like to trigger a LF398 Sample-and-Hold IC via a 3.5mm Jack (modular synthesizer). The desired behaviour would be:

if a cable is plugged in, incoming signals will be converted to short triggers.
if no cable is plugged in, the LF398 should sample all the time (the trigger part should be essentially bypassed)

This is the way the circuit looks right now:

The sections of the circuit are described below. The simulation pictured can be found here.

Problem

Is there any way I can reach the goal without adding too many parts or increasing complexity? Can I switch a signal path just by this switching jack?

Maybe if I exchange the switching jack with a stereo jack and add something on the ring that switches high as it is pulled to ground?

Edit: lifting ground at D8 and R20 would work, but how do I switch it the way I want?


texts:
the question is to find the small signal voltage gain(vo/vs).
I found out that vo = 1/3(vb+vs).
and the nonlinear resistor acts as an amplifier when 3 < vb < 8!
how can I get small signal voltage gain from here?


texts: Should I use a resistor between the gate driver and MOSFET (gate pin)?

texts:
I'm making a PWM driver for a DC motor. After some questions were answered in this post, I ended up with this schematic:

And I have some new questions:

Do I need a resistor between the gate and the output of the gate driver (U?)?
Do I need a pull-down resistor at the gate of the MOSFET?

MC34152 gate driver datasheet


texts: HFA3096 transistor array breakdown voltage

texts:
In the book Learning the Art of Electronics, one of the labs is to build a differential amplifier with a CA3096 transistor array. The author admits that the chip may be difficult to find and gives the HFA3096 as a suitable replacement. However, the datasheet for the HFA3096 gives the following breakdown voltages:

The circuit is a standard differential to single ended amplifier:

simulate this circuit – Schematic created using CircuitLab

Is it just me or does this circuit violate the transistor breakdown voltages? The author doesn't mention anything about using reduced supply voltages with the alternate chip. Am I interpreting the breakdown voltages correctly?


texts: I am trying to create a project for a 3 phase brushless DC motor rated at ~36A and 12V. What I want to determine is whether a particular motor driver with a gate drive current of whatever mA is sufficient for a given set of mosfets. For example, the STEVAL-SPIN3202 board from STM has an output current of "up to 15A" rms. When I check the driver (STSPIN32F0A) it can produce 600mA output and the mosfets used (STD140N6F7) have a drain current of 80A. So, where does the value of 15A come from is this example? Is there a standard calculation involved and what should I be looking for in the datasheets of both? For my project I was thinking of using the DRV8308 from TI, which has a gate drive of 0.13A, but looking at other evaluation boards it seems like this would not be enough to drive mosfets rated for say around 50A. Because BLDCs use PWM, would a too low gate drive current mean the switching of the mosfets would be simply too slow in practice, or what other issues would arise with a too low drive current?


texts:
I need to solve the task shown on the picture.

The first part is to calculate the temperature (in °C) from the NTC when Uv = 2V is. This means Iv is infinite.

The given Values are: Uq = 12V, R1 = 100Ohm, R2 = 200Ohm, R3 = 300Ohm

NTC: Rn = 1kOhm, b = 2000Kelvin, Tn = 293K

I tried using the formula: Uv = Uq((R2/(R1+R2)) - (R3/(R3+NTC))) and got 600Ohm for the NTC. After using it in the forumla for calculating an NTC I got only 81.85 degrees Celsius.

Can someone help me?


texts: Converting an AC switch signal into a reliable Digital ON/OFF signal

texts:
I am working on a project to add some digital processing, using Arduino, to an old Electro-Mechanical Pinball Machine.  Specifically, I want to detect the score reel triggering on the pinball machine and make a digital version of the score.

When a score reel is triggered, a switch closes, putting power into the coil of the score reel mechanism. This then advances the reel one position, and the power is switched off to the coil.

The pinball uses 25V AC through the switches and the coils. I have connected up and opto-isolator circuit across the switch, and so I can detect when it is powered. If I sample it constantly, of course with it being AC, I get a lot of ON/OFF's per second (UK 50Hz). I have programmed in a delay, which is partially working, but I either get too many or too few digital readings, compared to the mechanical movement of the score reel itself.

Part of the problem is that within the pinball machine, lots of different targets, rollover switches, etc. can trigger a point score. These work at different speeds and switch the coil on for different time periods. Also, say, if the pinball rolls over a rollover switch slowly, that switch is on for a long time, compared to a fast moving ball that triggers the switch for much less time.  So, I cannot rely on fixed timing. I need to treat one instance of the switch being truly on as one digital read (or point score).

I have tried a full bridge rectifier, to turn the AC signal into DC, but this doesn't help fully either, although has improved. So I'm looking for any other ideas please.


texts: Switching relay on and off affects analog sensor output voltage

texts:
I am working on an AVR project that involves measuring tempereture with an analog sensor (TMP36) and switching a heater on and off through relay to keep the temperature at desired level.

However, I've noticed that every time I switch the relay on, it causes the output voltage of the sensor to instantly drop, quite consistently by 0.01V to 0.02V (it's up to 2°C difference, so not negligible). To check whether that's AVR related problem or not I have constructed a simple test circuit, shown below. I simply enable the transistor by pushing down the button and observe voltage readings at sensor pins with a multimeter. It still shows the same behavior as with the AVR - switching on relay causes the same voltage drop.

Max current of my power supply is 5A, so it shouldn't be a power related problem.

Another important fact is that it doesn't matter if there's anything connected to relay's switching pins - this behavior seems only to depend on the relay coil being switched on and off.


texts:
I have a SMPS transformer and a LCR meter.
I can measure 3 different resistance on a winding:

R on a certain frequency(10kHz): 0.065R
Rs: 0.086(I don't know what is this)
DCR: 0.06

Which one is the transformer winding resistance here? I didn't shorted the secondary like leakage measurements, should I?


texts: create phase delay between square pulses in psim

texts:
i want to create phase delay between square pulses so that the mosfets don't overlap. block C was created to turn on-off the mosfet. however I am not allowed to use the 3 available square pulses as shown in the figure. how can i use only 1 square or triangle pulse to control the mosfets that are not concurrent??
Help me please


texts: Timer 1 (16 bit): Why is overflow interrupt sometimes missed?

texts:
Initialization of timer 1, the 16 bit timer on the ATmega328:

TCCR1A = 0; // normal operation
TCCR1B = bit(CS10); // no prescaling
OCR1A = 0;
OCR1B = 0;
TIMSK1 |= bit(TOIE1); // Timer/Counter 1, Overflow Interrupt Enable

16 bit overflows increment an overflow counter:

ISR(TIMER1_OVF_vect) {
    timer1OverflowCount ++;
}

In a loop it is checked whether the two 16 bit counters increment correctly:

void loop() {
  static uint16_t lastOc = 0, lastC = 0;
  uint16_t oc, c;

  ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
    oc = timer1OverflowCount;
    c = TCNT1;
  }

  if (c < lastC && oc == lastOc) {
    print(oc, c, lastOc, lastC);
  }

  lastOc = oc;
  lastC = c;
}

Sample output to the serial console:

Bad overflow: oc = 31, c = 49, lastOc = 31, lastC = 65440
Bad overflow: oc = 58, c = 49, lastOc = 58, lastC = 65440
Bad overflow: oc = 66, c = 49, lastOc = 66, lastC = 65440
Bad overflow: oc = 118, c = 49, lastOc = 118, lastC = 65440
Bad overflow: oc = 127, c = 49, lastOc = 127, lastC = 65440

Why does the overflow counter sometimes not get incremented?

I understand that the loop accesses the overflow counter a lot. During an access, interrupts are turned of with ATOMIC_BLOCK(ATOMIC_RESTORESTATE). However, the access is fast, and I expect the overflow interrupt to get queued so that it is never missed.

Full code for the Arduino Pro Mini ATmega328P (5V, 16MHz), compatible with the Arduino IDE 1.8.1:

#include <util/atomic.h>

volatile uint16_t timer1OverflowCount = 0;

ISR(TIMER1_OVF_vect) {
  timer1OverflowCount ++;
}

void setup() {
  TCCR1A = 0; // normal operation
  TCCR1B = bit(CS10); // no prescaling
  OCR1A = 0;
  OCR1B = 0;
  TIMSK1 |= bit(TOIE1); // Timer/Counter 1, Overflow Interrupt Enable

  Serial.begin(9600);
}

void print(uint16_t oc, uint16_t c, uint16_t lastOc, uint16_t lastC) {
  Serial.print("Bad overflow: ");
  Serial.print("oc = ");
  Serial.print(oc);
  Serial.print(", c = ");
  Serial.print(c);
  Serial.print(", lastOc = ");
  Serial.print(lastOc);
  Serial.print(", lastC = ");
  Serial.println(lastC);
}

void loop() {
  static uint16_t lastOc = 0, lastC = 0;
  uint16_t oc, c;

  ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
    oc = timer1OverflowCount;
    c = TCNT1;
  }

  if (c < lastC && oc == lastOc) {
    print(oc, c, lastOc, lastC);
  }

  lastOc = oc;
  lastC = c;
}


texts: What are the differences of a ferrite core transformer and an iron core transformer at low frequencies?

texts:
I made the BH curve of a ferrite core transformer and an iron core transformer with a 2V and 20Hz sine wave in input and saw that the BH curve of the iron core transformer is a bit larger than the other one.

What does that mean? What happens if I increase the frequency for each case?

Thanks !


texts: Wire color standards for a reversible DC motor

texts: I'm working on a project with a DC motor that runs in both directions. If the motor ran only in one direction, I'd use red/black for positive and ground, but as they reverse, there isn't a consistent positive or negative terminal. I understand that wire color isn't the most important thing, but I'm wondering if there is any standard or convention, even if it is weak.


texts:
I have a 4 digit LED display that I would like to integrate into my project, but only has 12 total pins when there are 4 digits. I am a beginner so I do not know how or which pins to power in order to display the required digits. Here are a few images of the LED Display. The number on the side is LD-5461BS.

If there is a configuration manual for this particular LED display, that would help as well.


texts: Are there any commercially available PLC's that can compile/ download programs through an API?

texts:
My team has decided to use a PLC for controlling an industrial process that requires simple, real-time IO to external devices with minimal processing. However, we expect the exact outputs needed to vary between runs (in fact, a given run will very rarely ever be repeated), and the operator will not have any PLC/ software programming experience.

While I can't disclose the actual product, the best analogy would be that we're designing an industrial smoothie maker, with PLC controlling precisely the opening and closing of different valves in real-time. The operator will use our software to design a custom sequence of additions of different reagents and the on/ off of relevant heavy machinery (e.g., an industrial mixer).

Here's the challenge: our current approach is to write our own compiler that translates the instructions that the operator gives (open valve A for 10 ms, open valve B for 20 ms) into ladder logic and PLC machine code. We would then directly download our self-compiled program to the PLC via serial. All of this would need to be automated so that the operator only needs to click a button after coming up with his sequence of steps.

However, despite my research, I have not found a single PLC vendor that both 1) has a compiler with API or publishes enough information about their PLC machine code to allow one to write a compiler, 2) supports direct downloading of programs to the PLC without use of the vendor's programming software (CX-programmer, Atmel studio, etc.).

I'm led to believe we might be taking the wrong approach, or at least don't know what product to look for. The i/o is simple enough to not justify the building of our own board, but the functionality we're looking for, namely PLC interaction with high level PC software, doesn't seem to be available.

Ideally, we'd like to download the entire program to the PLC at once and not be sending instructions one at a time. Execution of all instructions on the PLC (or whatever device we end up using) needs to be real time.

Are there any commercially available PLC's that support compiling and downloading of machine code, such that the entire process could be automated by a larger program? Is there any other way to download a real-time program to a PLC written by PC software written in a high level language?


texts: EA2-3NJ Relay won't switch, what am I doing wrong?

texts:
I purchases a tube of EA2-3NJ relays from Mouser. Reputable company, not counterfeit parts, yada yada. I try using them with 3.3V coming off a Raspberry Pi and they won't switch. I tried several other 3.3V sources, can't get them to switch. I tried 10 different ones from the sleeve, no luck. Contacted Mouser, after a little back and forth, they sent me a replacement set. Same issue.

Here is the datasheet. The coil wants to be connected one way (+/-) and I am sure I am connecting it that way. I am not using a pulsed or waveformed voltage. The 3V model that I am using has a Must Operate Voltage of 2.25V. I tried voltages down to 2V and as high as 5V. Never switched. The contacts will handle 1A at 30V, I was using 5V connected to a couple of LEDs to test the circuit. I tried it both with and without a flyback diode.

So, I don't know what else to try. It's a relay, it's not rocket science. The only thing I can find in the datasheet that might suggest a problem is related to storage time -- no more than 3 months at 70% relative humidity or 6 months at 50% relative humidity. So, could I have received two bad batches from Mouser or am I doing something wrong?


texts:
I am designing a power supply for a system which will require a 5v line and a 3.3v line and the ability to provide these lines from mains or a backup lithium-ion battery pack. The power supply must be able to charge the lithium-ion battery while mains power is connected and be able to automatically switch over to battery power when mains is disconnected. From 230v ac wall power I will use a full-bridge rectifier to obtain 12v dc. I would then like to use this 12v as input to the following circuit based around the TI BQ24103 charge management IC to do the charging of a two cell lithium-ion battery. Switch over is controlled with MOSFETS Q1, Q2 and Q3.

When VIN is on, the input powers the system directly via Q1 and Q2 and the charger at the same time.
Q3 is off during this time. When the input adapter is removed, Q1 and Q2 turn off and Q3 turns on. This
action ties the battery to the system.
Soft turnon of Q2 may be necessary to minimize the inrush current during the transition. The turnon time
of Q2 can be adjusted by changing the value of the capacitor C1 across the gate and source.

From the source of MOSFET Q3 my plan is to connect two buck converter circuits (one to get the 5v output and one for the 3.3v output). The buck converter circuits will need to provide their 5v or 3.3v output from either the 12v Vin or the 7.4v from the battery back depending on whether the mains power is on or off.

I would like to simulate this circuit either in LTspice or Orcad to test if it will work but I am uncertain how to go about this, I unfortunately can't find any spice models for the BQ24103. How would I approach simulation of this circuit?


texts: 50 MHz FPGA (Cyclone IV @ DE0-Nano) and 60 MHz input from FT2232H

texts:
I want to read data from FT2232H used in an FT245 style synchronous FIFO mode (http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT2232H.pdf p.27) with DE0-Nano FPGA board:

process(clk)
begin
    if (rising_edge(clk)) then
        next_state <= current_state;

        case current_state IS
            when POLL_UNTIL_RXF_LOW =>
                if (rxf = '0') then
                    current_oe <= '0';
                    next_state <= WAIT_SET_RD_LOW;
                else
                    current_oe <= '1';
                end if;
                current_rd <= '1';

            when WAIT_SET_RD_LOW =>
                current_oe <= '0';
                current_rd <= '1';
                next_state <= SET_RD_LOW;

            when SET_RD_LOW =>
                current_oe <= '0';
                current_rd <= '0';
                next_state <= READ_DATA;

            when READ_DATA =>
                if (rxf = '0') then
                    current_oe <= '0';
                    current_rd <= '0';

                    -- access data here
                else
                    current_oe <= '1';
                    current_rd <= '1';
                    next_state <= POLL_UNTIL_RXF_LOW;
                end if;

            when others =>
                null;
        end case;
    end if;
end process;

rd <= current_rd;
oe <= current_oe;

siwu <= '1';
wr <= '0';

This code doesn't work well: about 51% of my data gets lost. I think, this is happening because clk in this code is 60 MHz clock provided by FT2232H; however, the DE0-Nano has an on-board 50 MHz oscillator connected directly to one of the FPGA clock pins. Is it possible to read 60 MHz data with 50 MHz clocked FPGA at all? How do you do it?


texts:
Is there a standard for DC power connectors for 12V solar systems?

I am familar with Molex connectors, but they seem more suitable for internal connections, not something that would be outside of a housing.

Indoor
20-amp maximum


texts: LTC7001 Mosfet Driver is not working because of DPDT Relay

texts:
I am using a mosfet driver(LTC7001) to drive a mosfet. The mosfet is conducting 28 V continously which means its driver is always open.
In a step I must reverse polarity of load by using a DPDT relay. After doing this, mosfet driver is not working, I am afraid it is fried. Could you explain this please?

Datasheet of driver: Datasheet of LTC7001


texts: Two questions about astable multivibrators and transformers

texts:
Here's something that confuses me: The output on an astable multivibrator will be shown on a multimeter as half the input voltage (for example we have 9V-0V-9V-0V...and the multimeter averages it out and displays 4.5V). But then if I put that output to a voltage doubler, the voltage should be 18V, not 9V right? Since the voltage doubler will output in DC.

Second question is basically me being stupid: I've tried hooking up a transformer (9V to 230V, 0.5A) to an astable multivibrator (which operates at 671Hz) but something starts to smell burnt and the components of the astable multivibrator get hot. How do I fix this? (the components still work, I checked)
Here's the circuit:


texts: 15A 250V Extension Cord, but the voltage rating in my country is 220... What does that mean?

texts: Written on my Extension Cord: 15A 250V, but the voltage rating in my country is 220... What does that mean?


texts: Insulate a copper wire in home condition

texts:
I know I could buy magnet wire but unfortunately, the availability of magnet wire in my area is close to non-existent.

I'm looking to make 2 transformer coils one of 60 turns AWG10 (5 metre) and one of 10 turns (2 parallel wire AWG10 around 2 metre).

As a test, I made a small electromagnet out of AWG10 as insulation, I used electrical tape to prevent any short, each layer is covered with tape and each turn has some space which prevent wires to touch themselves on the same layer.

This seems to be good enough for a low power electromagnet but I'm wondering if there is a better way to insulate a cooper wire at home considering a lot of current is going to flow in the transformer I'm looking to make.


texts: can I use function generator as electrocutaneous

texts:
I am looking to build a electrocutaneous system to stimulate tactile sensation.

I researched and find we need to provide current wave of ~2mA ~0.2ms ~200Hz.

Can I build a function generator with arduino to use?

Is function generator same as Transcutaneous electrical nerve stimulation system?


texts: I am getting a Drill Size error and overlapping errors because I added a new via and a wire to my PCB. I'm not really sure why I am getting these errors. Is there a way to add a new wire and get it to connect to a wire that was already there without getting an overlap error? Also, do I need to make that via bigger in size? If so, how? I attached a picture that shows the area I need help with.


texts: Identify this 2-pin, grid-style, wire-terminated connector?

texts:
Can anyone help identify the type of connector in the picture below?
I need to make an extension cord for an electric bicycle's control throttle which happens to have that connector on it.


texts: Reverse engineering the manufacturer's programming sequence of an FPGA

texts:
As much as IP tends to make things easier, I would like to find was to learn more about protocols and interfaces by doing everything myself (I understand the difficulty of the task, and I have resources to aid me as in professors and books). From what I understand though, it is near impossible (without reverse engineering) to use any hardware features on an FPGA without IP. I have poked around online and found next to nothing on the subject as people seem complacent on using IP. Essentially I'm trying to find more open source HDL resources as there is a lack of it at the moment.

Edit: to be more concise, is it possible to work around manufacturers' IP to program fpgas?


texts: Setting the bias for the power amp section of an audio amplifier?

texts:
I've been working on the internal amplifier of SW-12 active subwoofer. I started suspecting its power amp section may not be working properly. (I get musically coherent sound out of the attached woofer, but the volume seems to be lower than before I started fooling around with the amp.).

Since I have changed R88, R89, and R90 (with the resistors of the same resistance rating but with 7W power rating), I think I'd better check if the bias for the power amp section is correct, at the least.

How do I do that? Can somebody guide me through this?

What mode do I set my multimeter to and measure where?

I have numbered various points in the schematic of the power amp section:

Oh, and what should the value/s be?

Do the LEVEL, PHASE, and LOW PASS settings matter when I do this?

How about signal going into the amp's LINE in? Is no signal fine?

= = = = = = = = = = = = = = = = = = = = = = = = =

The service manual for SW-12 is here:

http://www.audiolabga.com/pdf/SW12-15%20I.pdf

As far as I can tell, it doesn't mention anything about setting the bias for the power amp section of the amplifier.

= = = = = = = = = = = = = = = = = = = = = = = = =

Update (3/6/17):

Per jonk's guidance, I have checked the following:

+/- 81 volt rails: about +/- 91 volts;

+/- 15 volt rails: about +/- 15 volts;

voltage across two zener diodes, D5 & D6: +33.6V and -33.6V, respectively

Per Tonny Elliot's guidance, I had checked/adjusted R50 to make the DC offset at the speaker output 0V +/- 10mV or so (within spec) before starting the thread here.

= = = = = = = = = = = = = = = = = = = = = = = = =

A picture added (3/8/17):

R66, R67, R139 (brown resistor), and C55. I thought some of you might find this configuration interesting.

= = = = = = = = = = = = = = = = = = = = = = = = =

2 pictures showing speaker output V, A, and V*A added (3/11/17)

The load attached is a space heater with 17.2 ohms (not exactly 16 ohms as required for the alignment procedure described in Service Manual), but good enough for taking these readings, isn't it?

Adjusting R84 doesn't seem to affect these numbers significantly, by the way.

= = = = = = = = = = = = = = = = = = = = = = = = =

Further thought - Added (3/13/17)

After looking at the numbers (V, A, and V*A of the speaker output) and the accompanying charts above last night, I started thinking maybe the amplifier is OK. I don't like abrupt changes I see around LEVEL 6~7, but that how the circuit for this amplifier may have been designed. When this subwoofer was working fine, LEVEL 7 (1 o'colock) was about the highest I used. If this is the case, I don't know why I feel the sound lacks energy today. (I can't rule out the possibility of the woofer being damaged.)

Can somebody tell whether the numbers above look at least reasonably OK or absolutely not?

According to the specs for my subwoofer, SW=12, the maximum rated output is 150W into 8 ohm. (The input sensitivity for max rated output is listed as 60mVrms for LINE IN.) If my reasoning is correct, the voltage required to deliver 150W into 8 ohms is 34.6V. So, the amplifier seems to be amplifying the signal enough. or does it?

Several hours later. . .

I just remembered this comment of mine that I posted on March 9:

jonk: "Also, consider examining R34, too, which sets the gain." I made a test CD with 30 Hz. sine signal. Per instructions in the service manual, I set the output of the receiver to 60mV and measured the output of the subwoofer's amplifier with a 17.2 ohm dummy load connected. The voltage was about 20V. I increased the gain to make the output voltage about 33V (per spec). I found the sound quality got noticeably worse.

I hadn't touched R34 until then, so a part or parts of amplification may be missing. As to R30, the output voltage is noticeably lower than the spec's value, but I can't increase it because R30 had been rotated CW (to increase) fully.


texts: Can a diplexer connect two antennas with 2.4GHz signal to one transceiver?

texts:
I'm looking at using a single transceiver to handle multiple 2.4GHz signals.  Think like 2.4GHz mouse or game controller.

A diplexer can easily take two antennae and plug them into one RF signal port on an RF Microprocessor, which can then split out the 2.4GHz and 5GHz signals.  What about 2.4GHz signals in different channels, e.g. 2.4GHz Wifi and 2.4GHz mouse from two antennae going to the diplexer?  Would that be infeasible due to proximity of the frequencies?


texts:
If I have an oscilloscope, and tell you to move the X cursor, does this cursor move horizontally (Read X values), or is the cursor itself horizontal, parallel to the X axis?

I need the correct naming for an API interfacing with an oscilloscope-like GUI widget, and to avoid confusion, I need the right name.


texts: How can I make a voice transmitter receiver?

texts: How can make a system which have two circuit. And one is place at ground floor and another is in roof. We send voice (like call) one from other by pushing a switch and vice versa. It may be wired system. I want to make this system. Can you please help me?


texts: VU Meter only with 1LED (PWM) no IC except for OPAMP

texts:
first of all yes it is homework but I worked on it and stuck at only this part. Maybe I am approaching on wrong side I am open to every advice.

I changed the idea in my mind.

I want to make a voltage selector circuit with opamps, capacitor, diodes only (Transisors and other IC's forbidden except only for opamp). But I couldn't find a way, do you have any advice for me ? Its like a dot display level meter (dot not bar) but I can not use LM3915 etc.

I have a varying DC voltage and want to make a circuit that choose a specific path for its amplitude. I don't need to save dc input I don't need its information, I only want to know its amplitude Voltage range

Like if dc source has 0-1V current flow goes path 1, if it has 1-2V current flow goes path2, if it has 2-3V current flow goes path3 etc. But when it goes from path 3, it cannot goes through path 1 and 2.

I know that I will use comparators but couldn't find a logical connection which will stop unneeded paths.

(Paths will not be open circuited as I show it on image there will be more connections to them by using buffers.)

I tried to make something I figured out this circuit. But I couldn't find a way to block lower levels. For example if I have 5 V as in figure, it doesn't go through R3 yes its achieved, but it shouldn't go through R1 as well it should only go through R2.

Thanks


texts: Some confusion on basic antenna theory and crystal radio antenna

texts:
I found a similar question here:Making a suitable antenna for a crystal radio but it didn't satisfy my questions.

Imagine an AM crystal radio as in below illustration:

Most of the time the ground of the coil is actually connected to the "earth ground". (I still don't get why)

Isn't the antenna size related to the wavelength of the radio signal of interest? Why is not both terminals of the LC circuit not connected to two very long wires proportional to AM carrier wavelength instead of earth. I also would be glad if someone might explain how can small antennas receive long wave length radio waves? I mean isn't it that according to the antenna theory the antenna     arms should be approximately 1/4 wavelength long?


texts: Grove capacitive fingerprint sensor not working

texts:
I have just purchased one grove capacitive finger print sensor.
link.
I am using Arduino Nano and followed there tutorial but the example code isn’t working.
Blue light on sensor never turn to green as it should according to the code. Also it says register ok without putting any finger on it.
I am sharing the result of full process code.
18:12:23.433 -> Uart===> : EF.1.FF.FF.FF.FF.1.0.8.31.0.1.4.0.F.0.4E.

18:12:23.433 ->

18:12:23.433 ->

18:12:23.433 -> Usage:

18:12:23.433 -> Please put your finger on the touchpad, from green light which on the touchpad lights on till it lights off.

18:12:23.433 -> Repeat for 4 times.

18:12:23.433 -> If the red light lights on, it indicates that an error occurred.

18:12:23.433 ->

18:12:23.433 ->

18:12:23.433 ->

18:12:23.433 -> Uart<=== : EF.1.FF.FF.FF.FF.7.0.5.0.0.0.0.C.

18:12:23.480 ->

18:12:23.480 -> Register ok!

18:12:24.456 -> EF.1.FF.FF.FF.FF.1.0.8.32.0.FF.FF.0.7.2.40.

18:12:24.456 -> Uart===> : EF.1.FF.FF.FF.FF.1.0.8.32.0.FF.FF.0.7.2.40.

18:12:24.456 ->

18:12:24.456 ->

18:12:24.456 -> Please put your finger on the touchpad, from green light which on the touchpad lights on
till it lights off.

18:12:24.456 -> To verify your finger print.

18:12:24.456 ->

18:12:24.456 ->

18:12:24.456 ->

18:12:24.502 -> Uart<=== : EF.1.FF.FF.FF.FF.7.0.8.24.5.0.0.0.0.0.38.

18:12:24.502 ->

18:12:24.502 -> Verify failed,error code = 0x24

18:12:24.502 -> Ret param = 5.0.0.0.0.

18:12:24.502 ->

18:12:24.502 -> Please check the error code through datasheet!

18:12:24.996 -> EF.1.FF.FF.FF.FF.1.0.3.D.0.11.

18:12:24.996 -> Uart===> : EF.1.FF.FF.FF.FF.1.0.3.D.0.11.

18:12:24.996 ->

18:12:26.518 -> Uart<=== : EF.1.FF.FF.FF.FF.7.0.3.0.0.A.

18:12:26.518 ->

18:12:26.518 -> Operation succed.

18:12:26.518 -> Delete ok!

I get this without doing anything and while light is still blue.
I tried to find datasheet but could not find one to see what this error code mean.
Is it because my module says it is KCT203 and library is for KCT202 ?


texts: Altium error: Open emitter pin and power pin object!

texts:
I am new with Altium Designer. I receive the following error:
(+12V contains Open emitter pin and power pin object!)

Here is the error schematic part:

The error is in Pin 4. Any TIPS?


texts: Driving single phase induction motors on three phase inverter

texts:
I like to drive a small (150W) single phase induction motor by an existing three phase inverter by removing the capacitor and just connecting the two windings to the inverter in an incomplete triangle circuit.

I've done that with very small (15W) motors before, which run well, despite a little bit more noisey at low frequencys. I guess this is because the single phase motor uses a 90 degree offset between the main and the capacitor generated phase, while the inverter provides a 120 degree phase offset.

So I like to know what problems (despite the noise) may occur by this abuse if driving very low torque and speed in respect to the motor capabilities.


texts: Why are kiCAD Net Labels not searchable when converted to pdf?

texts: I converted the kicad schematics to pdf but when I search for "I2C_SENSORS_SCL" - the text does not show up. Is there any way to make the net names searchable text in the pdf?


texts: How to use gold finishing to reduce corrosion on a moisture sensor?

texts:
Background
I have a raspberry pi with a moisture sensor that suffers from corrosion. My setup is similar to the one described in this raspberrypi.stackexchange question about corrosion of a moisture sensor.
A solution to this problem, suggested in this answer, is to coat the PCB in gold finishing.
This is something I would like to try.
Question
However, as I am a complete newby to the field, I do not know what section exactly to "gold finish". Therefore my questions are:

Do I need to cover the "connections section" with gold finish? By which I mean the section where the pins are connected to the wires. See the green highlighted area in the above figure.
I can see that protecting this area might be smart, especially since this sensor is used in a moist environment, but I do not see how gold plating the "connections section" prevents corrosion, which happens on the "rods section".

Do I need to cover the "rods section" with gold finish? By which I mean the two "pointy" parts of the sensor. See the orange highlighted area in the above figure.
I can see that this might prevent corrosion, but won't this stop the sensor from working by covering its rods?


texts: Inverter : drive with high impedance. Results on the output

texts:
I have to compile a 9-valued logic table for a circuit.
I would like to know what happen to the output of an inverter and of a pass-transistor-gate if driven in high impedance.

Specifically in this circuit :
a1=Z
a2=1 (or HIGH)

Why y=WEAK?


texts: Phone touchscreen malfunction when connecting audio circuit to it's jack

texts:
I use this circuit to convert audio signal to infrared signal and control my DSLR camera.
It works fine on my laptop jack, but when I plug it to my smartphone jack, it shows some malfunctions in touchscreen (random taps without my Interference). How should I prevent this?
(I use a DC adapter(+ ground wire) as power source, but it will be replaced by battery later)


texts:
I had used the Royer Oscillator topology (or a Mazzilli, are there significant differences ?) for a project on Induction heater. I had a hard time understanding how it actually works, especially how the two Mosfets trigger the oscillations. Somehow I ended up concluding that it has to do something with a tiny difference in the Q-points of the fets. Can anyone throw some light on this ? Thanks.

Edit:
This is the version of the circuit I was referring to:

My actual doubt is whether the VI characteristics of the two transistors has a role to play, i.e, whether a tiny difference in their characteristics help one of the FETs to switch ON first and then on the switching alternates ?


texts: Temperature dependance of IGBT max collector current

texts:
I have an IGBT (datasheet), that I am using as a switch for a coilgun. How would I calculate the maximum pulse collector current in function of the ambiant temperature and time?

Also, if we're missing anything, is there a method we could use to maximize our maximum pulse collector current that doesn't involve temperature reduction?


texts: Can you get shocked if you touch a hot wire whilst perfectly electrically insulated?

texts:
Okay this issue has been bothering me immensely so hopefully someone will be able to help me out or steer me in the right direction.
Lets say hypothetically I possessed an absolutely perfectly insulating chair and I stood on it and then touched the hot wire of a three prong socket, would I get shocked? My existing knowledge tells me that I will get 'somewhat' of a shock. This will be because a human body has a non-zero capacitance  and so charge will flow onto and off me sequentially in sync with the frequency of the mains supply as it oscillates my potential up and down with the wire that I am presumed to be touching. The question of whether this oscillating current into and out of my body at say 50Hz will shock me severely or not depends on the capacitance of my body. If my capacitance is extremely low (as is the case for a bird perhaps), then the shock and the sensation all together would probably be minimal. If I were a large animal like an elephant then the current would be greater since my capacitance would be greater. So my question becomes : Is the capacitance of a human body great enough to cause a severe shock in this case?
Now if this is all true and my suppositions are correct then why does a high voltage repairman have to wear a Faraday cage type suit (as in the case in this video https://www.youtube.com/watch?v=9YmFHAFYwmY). Is this because the voltage is so high and the capacitance of the helicopter is very large so that immense current flows back and forth during each oscillation? Because of this immense current, both the repairmen and the pilot must wear a Faraday cage suit to ensure that the current flows around their bodies via the skin effect? If they did not wear those Faraday cage suits then they would surely be shocked to death since the arc between the wand they use to initially touch the line shows that the current going into and out of the helicopter as well as the potential difference between the line and the helicopter is immense (surely enough to kill them both). So then I ask, well if the Faraday cage suit is what is protecting them from severe potentially fatal shocks, then why do electricians not wear them when working? If my belief about the Faraday cage suit being the primary protection of the high voltage line repairmen is true, then surely if I wore one and touched the live wire of a three pronged socket whilst perfectly grounded I should be completely immune to a shock?
Any help on this would be greatly appreciated!


texts: LED PCB through-board connectors - how to search for them?

texts:
I have been looking for a through-board connector solution for single layer MCPCB LED boards for a while.

Some options are edge connectors or right angle male/female connector sets.
But these either don't have the correct current rating or are just too costly.

Generic bottom entry surface mount female headers don't have slightly angled pins (like your regular SOIC ICs) for avoiding shorts with the milled cutout below.

So while scrolling Google, it seems that LIFX has it all figured out when it comes to cheap and simple mass production connectors.

I added some pictures of connectors from teardowns (not mine), but can't seem to find any part# or source for them.

If anyone knows some magic buzzwords to search for or even better a part#, please tell me.

And another variant with a pass-through for a WiFi antenna to stick out.


texts: Why should signals in circuits propagate much slower than the speed of light?

texts:
I've read a couple of other topics (such as this one and this one) about the lumped circuit abstraction requiring that signal timescales (i.e. the period of the highest frequency signal component) be much longer than the propagation delay of the signals though the circuit, and that the wavelength should be much longer than the largest dimension of the circuit. This makes sense to me as explained in the linked topics above.

However, in the book Foundations of Analog and Digital Circuits by Agarwal and Lang there is this additional comment:

  If we are interested in signal speeds that are comparable to the speed of
  electromagnetic waves, then the lumped matter discipline is violated, and therefore we cannot use the lumped circuit abstraction.

The author of this book also states in this lecture (timestamped) that the assumption is that all signal speeds of interest are much slower than the speed of light.

This is confusing to me since it seems to be saying that the actual wave propagation velocity needs to be small. I don't understand how this is the case since it seems that faster wave propagation would actually help the circuit.

So suppose that you have a circuit with largest dimension \$d\$. You want your signal to propagate at the speed of light, \$c\$. You know that the wavelength \$ \lambda \$ of the signal should be greater than \$d\$, so pick a signal which will have \$ \lambda = 10d \$, as an example.

Then,

$$
\lambda f = v  \to f = v/ \lambda  \to f = \frac{c}{10d}
$$

Then if for example \$d\$ is 1 cm, choose \$f\$ to be approximately 3 GHz. So now the signal period is about 333 picoseconds and the propagation delay is about 33 picoseconds.

Why is this invalid?


texts: What limits the maximum allowable current of a power LED?

texts:
I wonder what it is that limits how much current can flow through a power LED. If the heat removal is managed properly how large can the current get? Why 45x45 mil size LED chips are rated 3W (700mA) but smaller ones 350mA?
I've got an LED module, it has 9 45x45mil LED chips (It is RGB), I want the maximum light intensity possible, what is the maximum safe current? I don't care if the life is shortened to half or one third compared to if it were drived at 350ma (the manufacturer rated current).


texts: Effect Of Electronic Devices In Close Proximity

texts:
From reading other posts, it seems like electromagnetic induction is the greatest threat to electronic devices these days with either traditional HDDs or newer SSDs.  Since current in a wire creates an electromagnetic field, I assume most electronic devices create their own field (albeit probably a weak one). Electromagnetic induction could be created by moving the devices around each other in a rapid fashion. Is there any danger to electronic devices (including their memory/storage and microchip functionality) when they are placed in close proimity to each other... say stacked on top of one another while operating?

Bonus Points: Assuming I was able to measure the electromagnetic field, what values would cause concern?


texts: How does a capacitive receiver work for a fox and hound set?

texts:
I have been scouring the internet trying to find this answer, I've found hints and ideas, but nothing concrete, like an actual theory of operation.

I'm making a fox and hound wire tracer for my final project in ECE 202. The signal generation isn't hard, I get that concept, but I'm having trouble figuring out the theory behind the "hound," that picks up the signal from the wire.

I had always thought they used inductance to pick up the signal from the wire, and found one such design here. I may go with that, but I still want to know how the more common (and likely less bulky) capacitve probes work.

I found these three schematics, all of which seem to be a variance on the same principle. I see a capacitor connected to a high impedance before going into the amplifiers. The fancier ones appear to have some sort of bandpass filtering circuit as well, but I know what to research there.

I just don't understand the principle which is allowing these to pick up the signal.

Is it just an antenna? If so, what is the purpose of the capacitor? I vaguely recall something about electrically lengthening an antenna with inductors and shortening with capacitors, but that doesn't seem like what's going on here.


texts:
Sorry for the crude drawing I hope it explains the situation.

Basically I have 12 pieces of 24v panels connected in 3 strings of 4 serial connected panels. My Open Circuit Voltage is 150V and I can have 3x10=30A of closed circuit current. I have a charge controller which can accept 150V and charge a 48v battery bank. So far so good. But now I need to connect a pump driver (a frequency control inverter) which needs at least 340V. I was wondering is it possible to use diodes as shown in the drawing to get both 150V and 450V from the PV arrays without damaging anything ?


texts:
Question: find current, voltage and power at each branch using fourier series analysis

Update - here is my solution attempt:


texts:
I'm reading through the datasheet for the TL064, which contains this figure on page 16:

This is of course an instrumentation amplifier that apparently uses an inverting amplifier's output instead of a ground in the lower-right corner of the above figure, but what really perplexes me is the 100 kΩ resistors attached directly to the noninverting inputs of three of the four amps. I don't recall seeing an instrumentation amplifier circuit in books or application notes that have them, and all of the instrumentation amplifiers I've built using the three op-amp scheme works fine without them.

The datasheets specifies an input resistance of 1012 Ω, which is 10,000,000 times greater than 100 kΩ, so it doesn't seem to add anything to the already high-impedance JFET inputs. I thought perhaps it has something to do with input bias currents, but that's just me making a wild stab in the dark.

Curiously, figure 26 in the same datasheet (page 18) shows a two-op-amp version of an instrumentation amplifier without the 100 kΩ resistors at the noninverting op-amp inputs!

What's the purpose of the 100 kΩ resistors at the noninverting inputs in the above circuit? Am I missing something completely obvious?


texts: Global variable in AVR interrupt routine

texts:
I am writing a code with interrupt routine. For debugging the code am using UART. So, here is the snippet:

volatile int overflow_count = 0;

int main(void) {
  while (1) {
    continue;
  }
}

ISR(TIMER1_OVF_vect) {
  char* time = "";
  overflow_count++;
  sprintf(time, "overflow-%d", overflow_count);
  uart_send(time);
  if (overflow_count == 2) {
    overflow_count=0;
    uart_array("Alarm code execution");
  }
}

Until first time the interrupt routine is called overflow_count value is 0 and after that, value is not incremented by one as per the code. Instead a random value (eg. 142851) is displayed while sending it from serial port. So, it never satisfies the condition if (overflow_count == 2). I am curious to know why it is not working.


texts: Find the thevenin equivalent resistance for the given circuit

texts:
I need to find the equivalent thevenin resistance, everything from the points A,B is exchanged.. however after I construct the image:

It says the answer is Rth = 100 Ohm, but I can't figure out how, would it be different if I move the points A,B between R2 and R3 and R4 and R5 respectively (the points A&B aren't given , I just have to change the rest of the circuit to a thevenin equivalent and just leave the branch where Rp is.)

I know this is a homework like question, but can someone just explain it to me how would I get to the result, or link to some useful tutorial so I can learn it on my own.


texts:
i'm a grade 9 student and a beginner at Arduino. I'm working alone on a robotics project. I am working on a Poulo QTR-1A Reflectance sensor and I was wondering what this symbol represents.

Any help would be appreciated.


texts:
I am using SPST switch as a digital input to my NXP MBED Module.I have done the design of the whole circuit in OrCAD Capture and Allegro PCB Editor.
the switch I am using is Panasonic's ESE-11SV1.The land pattern in the datasheet which can also be found on the link-http://www.panasonic.com/industrial/components/pdf/011_es081_ese11_dne.pdf
shows 4 terminals-Two pins called C(common terminals) and Pin no.1 and 2.
How should all the pins be connected as digital input to the MBED Module?Usually any SPST NO (Normally Open) switch has only 2 terminals,but the Land Pattern of this part shows 4 terminals.How should they be connected?


texts: Is simple voice synthesis (just digits 0-9) possible with Cortex-M0+ with 4kB flash?

texts:
I'm working on a little side project with the LPC810 (Cortex M0+ 32 bit ARM MCU, 8 pin DIP package, 4kB flash, 1kB SRAM). I need a UI to convey to the user a temperature setting. I only have about 2 pins spare to implement the UI.... so using LEDs is going to a challenge.

I had an idea of using just one pin to drive a speaker or peizzo buzzer and convey the temperature in speech. Just the digits 0 - 9 in english is all I need. Storing  0-9 in PCM is out of the question with so little flash. So I was wondering is anyone aware of open source code that would allow for very high compression of a small dictionary of words what would be light enough on CPU/RAM to work with a Cortex M0 class MCU?  (I have a strong hunch this is plain out of reach of low end Cortex M0 MCUs without external memory).


texts: Planar Transformer Design and Insulation Requirements

texts:
I am currently thinking of designing a planar transformer for my SMPS application. The input voltage will be somewhere in the region of 150V, the output voltage in the region of 1.5kV.

First of all, I have noticed a severe lack of information on the internet that discussed the design process for planar transformers. Typing "Planar transformer design guide" tends to just get me companies trying to sell me their planar transformers. I wish to design my own. Does anyone know of any good material that discussed the actual design of a planar transformer - such as the selection of primary turns, secondary turns - winding configurations, etc.

Furthermore, my transformer must be insulated above 10kV for safety reasons - 1.5kV is not my final output voltage. I am looking online and have noticed that the insulation is typically achieved by placing thin sheets of insulators between the primary and secondary PCB boards stack-up. I have attached such an example for illustrative purposes.

My question is - does each layer of insulation between the primary, secondary PCB boards need to be the entire 10kV? Or does the total isolation between the top board, and the bottom board, need to be 10kV?

To me, it only makes sense that the insulation should be 10kV/insulating layer, since there will be high voltages between each of the secondary PCB stacks.

Additionally - what materials would be recommended to insulate a transformer at such voltages? I have seen Teflon, "FR4" and the like which are used for HV insulation applications

How can we tell which insulators would be good at High frequency? It is to my understanding that insulators lose their properties at high frequency. This info doesn't tend to be held in data sheets for these insulating materials!


texts: What is this checkered pattern in altium when placing tracks?

texts:
I'm learning altium and trying to re-route an existing board that I have not that much experience with I've found this checkered pattern in some tracks that Altium is being very annoying at:

They appear by the looks of it when tracks are too close together, if I delete one track it dissapears:

It probably has to do with the fact that altium does not allow me to place the tracks too close together (0.5mm). There is no rule that I can see that makes this happen (track to track clearance is 0.15 or 0.2mm), and when drawing with the clearance boundaries on it doesn't appear to be any restrictions, but i can't place tracks closer than 0.5mm and it doesn't even allow me to place them on the pads of an SMD component because of that. :

Both nets are probably a differential pair but i haven't seen any restrictions that apply to that either. Differential routing does not help either, the tracks dont appear (because they would be for sure closer than 0.5mm). Sorry if the question is obvious, but i've been looking at the documentation for awhile and haven't found anything.


texts: In transmission line does reflected wave travel on the path before impedance or after impedance?

texts:
I was taught in class that 2 port RF networks have the following structure below, where V2+ is the reflected wave if load at end of port 2 does not match the characteristic impedance of lines at port 2:

simulate this circuit – Schematic created using CircuitLab
Let's take a simple circuit that we can make practically, it consists of 2 ports where input is being applied at port 1. The network consists of a single resistor whose value may not match with characteristic impedance of either lines resulting in reflection:

simulate this circuit
What I want to understand: If frequency of source is so low such that wavelength of input wave is much greater than L1 and L2 then the circuit doesn't need reflection consideration. What I mean is it would be like a 10 Hz source powering an appropriate load of wire length say 5 cm. This means voltage at load and source vary exactly as each other.
Statement 1: So, in above case, when we reduce it to simple network theory and we say that the current will travel thru Path 1 and return thru Path 2 (which we usually call ground path).
Statement 2: When we increase frequency such that wavelength is comparable to network, then also current should return thru Path 2. But according to first diagram, the reflected voltage/current returns thru path 2.
So, my confusion is does the reflected current wave, I1- (according to first diagram) returns on path 1 or path 2. If it returns on path 2, then does it add with the returning I1+?


texts: Fuse current rating and breaking capacity

texts:
I want to use the following fuse  to safely interrupt a buck power supply with rated parameters Input (1A, 24V)==> Output (250mA, 12V). In the datasheet of the fuse, the constructor specifies the rated current and also the breaking capacity parameter.
 The fuse i want to choose in the datasheet has a rated at 1A and has a breaking capacity of 100A. What happen if i choose this fuse, knowing that the power supply cannot provide a 100A current even in case of short circuit ?


texts: If I have a 3 and half digital voltmeter operating on the voltage range of 40V then what would be its resolution? While trying to solve this I found in one of the books that only active digits ( which in this case are 3) will be used to calculate the resolution. However doing so I was getting the wrong answer.  Is this method not correct?


texts: Precise Resistance Measurement Techniques

texts:
This question is inspired by some basic questions on resistors I've read here lately.

What's the most accurate/precise technique for measuring the value of a resistor you can think of? What level of precision can be practically achieved? Can you repeatably measure a resistance to +/- 1 micro-ohm? +/- milli-ohm? Can you somehow distinguish between a resistor of a given value and equivalent series resistors? equivalent parallel resistors?

Not to limit answers too much, but I'd be interested in using a microcontroller plus external circuitry to take the measurements. Sorry if this is too vague of a question, I struggled to narrow down the scope. I'm thinking of techniques that incorporate GPIO pins and onboard peripherals like ADC and Analog Comparators.


texts:
I found the following note with a set of test leads we use for our Agilent 34461A[1][2]:

  This Test Lead Set is designed for use with the Agilent 34xxxA Multimeters, and also the U274A, U3401A, and U3402A Multimeters. Do not use with the Agilent 3458A.

I suppose they're simply not calibrated for use with other meters and 'too inferior' for use with the 3458A[3]. But afar from precision, is there any reason not to use them on a different multimeter, provided they fit?


texts: Highspeed Signals on outer layers of pcb

texts:
in many application notes for processors in a BGA package I see a declaration that you could fully fanout the bga using only 4-6 layers and almost no HDI technology like microvias, burried vias even for high speed signals like DDR,USB etc.
For example in the application note for the  STM32MP1 on page 46 ff. you can see their 4 layer stack up with µV only from L1 to L2. On page 50 you see they achieve this fanout by using the top and bottom layer for signals and L2 and L3 for VCC/GND reference plane.

But is it such a good idea to route highspeed signals like DDR, USB on the outer layers? I always thought they are best routed in the inside sandwiched between reference planes. This way they are well shielded an protected from environmental influences or is this just overengineering and too expensive?
Is this 4 layer layout just a marketing stunt or is this kind of fanout really used in industry, because its cheaper and reliable enough?


texts:
I'm designing a PCB for a device, which will contain the following functional blocks:

12V power input with SCR crowbar, reverse polarity protection, soft-start, and 3.3V linear regulator. Regulator feeds all ICs on the board (MCU+INA219+MAX31865);
DB-9 connector which leads to external heater device with PT100 sensor, INA219 to measure heater current and MAX31865 to measure PT100 temperature. Heater is designed to draw relatively small currents, not more then 800 mA;
MCU, which drives the heater via logic level MOSFET, communicates with INA219 and MAX31865 on board, and CP2102 for USB link.

On the below image I've shown board sketch with 3 zones, where I've placed components of 3 logic blocks mentioned above. Board is 4 layer (signal-GND-3.3V-signal).

Am I right with this layout? If yes, how should I divide ground plane (and should I?)? Should I add second linear regulator to feed ADCs separately?
I've read many forums and replies on this site about digital and analog ground, however some advices are contradictory, and for me it's complicated to apply abstract advices to real board layout (this is the first board of such complexity for me).
ADDED:

+12V is supplied from wall wart AC/DC
+12V and +3.3V have common ground
USB is connected to a PC, can be disconnected. USB +5V isn't used to power the circuit (connected to VBUS pin of CP2102 according to the datasheet).


texts: What data format do audio cassettes use?

texts: How do the sound pressure values correspond to the magnetic domains on the tape? Is the format analog or digital?


texts: How to read 0 -10V analog voltage with lower voltage tolerant ADCs without a voltage divider

texts:
Background Information
I want to implement an ADC as an extension to a Raspberry Pi, so that it has the capability to read analog signals. I will be using the MCP3004/3008, as I got lost in the datasheets of the TI counterparts. For now, 10-bit resolution is good enough.
I am aware that I could use a voltage divider like this:

simulate this circuit – Schematic created using CircuitLab
The Question
Because this is for a prototype that should be up to industrial safety standards, my boss wants me to isolate the 10 V from the 3.3 V logic. I don't really know a method to do this though while reading analog signals.
My Google search didn't yield any answers to me. So I was wondering if there is a method to read analog values, without a voltage divider that is safer to use when reading higher voltages with low logic voltage components. I would use an opto-coupler if this was a digital signal, but I am not sure if there is a way to achieve the same level of isolation while reading analog values. I would appreciate it if somebody more experienced would share his knowledge.
Edit: I have decided on using 2 ADS1115/ADS1015 instead of MCP3004/3008.


texts: Do purple LEDs mix blue and red, or do they emit true violet?

texts: Do the rare "violet" LEDs emit true violet (400-420nm) light, or do they mix blue and red (440nm and 700nm) light?


texts: I am constructing igbt based switching circuit for switching multiple coils with a proper time delay for a scientific experiment. I need to simulate the circuit before doing on board. I am using pspice. It doesn't have igbt gate driver as I require. How to go about it?


texts: Easiest way to solder connections to all the legs on a surface-mount chip?

texts: Recently, I went through the process of soldering wires onto the legs of a TQFP chip (~0.8mm pitch) which has already been mounted on a PCB. This is a project where I am doing some modifications to the original hardware, so I don't have the ability to change the PCB design at all. I was curious if there was any way to more quickly attach connections to this chip - perhaps some sort of socket that sits on top of the chip? Really, is there any way to make connections to the legs of the chip other than painstakingly soldering individual wires?


texts:
What's a good way to read a 24v emergency stop signal with an mbed?

The 24v signal is connected to an E-stop contactor which disconnects power to a motor when the 24v is interrupted (i.e. when e-stop button is pressed).

I need a good way to read when the 24v signal is interrupted with an mbed.
Would an opto-coupler be a good way to isolate the signal and lower the voltage to a value which the mbed could tolerate.


texts: problem generating Triangle wave using DDS

texts: I'm trying to generate several waves using a Mojo-V3 board, that has a Spartan-6. I use DDS method to generate the waves. The description of the hardware is in VHDL. At the output of the FPGA there is R-2R DAC to convert the data to analog values. I have no problem with sine wave, but, when I generate Triangle wave, the osciloscope show me peaks when the wave reaches the highest and lowest values. I think the problems are the harmonics, can you confirm that?. At the output of the DAC there is no filter. I use the 20Mhz Bandwith filter and the peaks are lower, but it still appearing in the wave. How can I fix that?


texts:
Why is the supply voltage 400V when the neutral is disabled in a three phase supply?

Phase voltage is 230V. Line Voltage is 400V.


texts:
I am constructing a Chebishev or Butterworth audio filter (low and high pass), but I need to have all parameters highly adjustable - especially Fo and Q. For this purpose i would need to be able to adjust capacitance (and/or inductance in case I decide to go to the passive filter topology instead) very accurately and in very wide range - from 1nF to 10uF ultimately.
There are some IC variable capacitors with digital control (SPI/I2C) on the market, but the max capacitance offered is way too little. In order to solve this problem my first attempt was to use analog switches to connect /disconnect several capacitors in paralel in order to obtain the desired capacitance.
The capacitance (inductance) should be able to be controlled digitally, as the topologies require adjustment on all parts in order to obtain desired Fo /Q.
Low noise is of paramount importance.
My question: How would you address such a problem? Are there anywhere already available solutions for this? I was looking for an analog switch 16:1 or 32:1 which could be able to crosspoint-connect any of the inputs, but so far no any luck. All of them are connecting only one of all inputs to the output, or they are not bi-directional. Please help.


texts:
I have a hypothetical question in regards to phase conversion and transformers, more specifically on their combination. I am not a certified electrician or engineer, so I don't know what all goes into something like this, but I am very much so interested in learning, so I welcome any constructive input.
My question is: if you have (I believe it is) single phase 120v from a residence, is it possible to use a transformer to step that up to 480v, which in turn goes into a 1-3 phase converter, to provide 3 phase 480v output? Would this be a single device, or multiple units linked together? The resulting power would then be used for something like a Tesla Supercharger, which I understand requires a 3 phase 480v supply. And money being no factor, would it be possible to install something like this in a residential setting? Why or why not? What would go into building something like this?
Again, this is a hypothetical question, driven by a conversation between my EV enthusiast friend and I late at night, of which neither of us has an electrical background, so I thought I would consult the great minds of Stack and see what may or may not be possible. I am very well aware of the dangers working with voltage, especially when it comes to mains power, and I have no intention or desire to make this type of system myseld, I'll leave that to those learned and certified to do so, much safer that way.
Thanks!


texts: What do terms half-rate and quarter-rate mean for DRAM memory controllers?

texts: DDR3 Memory controller are often presented as being half rate or quarter rate, but what does this mean? e.g if I have a DDR3 SDRAM that is x16, what does the half or quarter rate imply in that case and why do we need to create such memory controllers?


texts: Calculate voltage, current and resistance in a complex mixed circuit

texts: How can I calculate voltage and current on each resistor (especially R5) in this circuit? What is its overall resistance? I have no idea how to do this.


texts: How does one determine the power consumption of a device/load in a circuit?

texts:
I have a question regarding circuit design, however i'm not sure whether i can express it in correct terms or if there's a fundamental flaw in my thinking.

When using a device,how do we know exactly how much power it requires in
order to start up/operate correctly?
How do we calculate such requirements?

Let's say we have a circuit consisting of a power    supply, resistor    and some device like a chip or other    microcontroller, or any other    kind of load for that matter.

How do we reason about the power supply needed for that device to
work?
Knowing that power is essentially voltage times current, how do
I choose values for those components?

Forgive if my qeustion does make any sense
Regards


texts: STM32F103R6 (Cortex-M3) trouble with rising edge detection

texts:
I'm using Proteus 8.6 for simulation of STM32F103R6 microcontroller with ports C0 connected to a LED and port C1 connected to a button. I'm trying to capture the rising edge of the button so that it switches the LED on every third click. I'm getting a weird behavior because it switches the LED on the 2nd click(rising) and it turns the LED off on the click after that(falling). I've tried 3 other configurations, using pull down input mode, but capturing the falling edge and using pull up input mode and capturing both rising and falling edges with button connected to the ground. Only configuration that gives me weird behavior is when the button is connected to power and I'm using pull down input mode while capturing the rising edge. Here's my code:

    #include <stdint.h>

#define RCC_APB2ENR (*((uint32_t *) (0x40021000 + 0x18)))
#define GPIOC_CRL (*((uint32_t *) (0x40011000 + 0x00)))
#define GPIOC_ODR (*((uint32_t *) (0x40011000 + 0x0C)))
#define GPIOC_IDR (*((uint32_t *) (0x40011000 + 0x08)))
#define AFIO_EXTICR1 (*((uint32_t *) (0x40010000 + 0x08)))

#define IOPCEN (0x01 << 4)
#define AFIOEN (0x01 << 0)

#define MODE_OUT_2MHZ 0x02
#define CNF_GP_OUT_PUSH_PULL 0x00

#define MODE_IN 0x00
#define CNF_GP_IN_PULL 0x08

#define EXTI_PORT_C 0x02

void init_GPIOC()
{
    RCC_APB2ENR |= IOPCEN | AFIOEN;

    GPIOC_CRL |= MODE_OUT_2MHZ << (4 * 0) | CNF_GP_OUT_PUSH_PULL << (2 + 4 * 0);
    GPIOC_ODR = 0x0;

    GPIOC_CRL |= MODE_IN << (4 * 1) | CNF_GP_IN_PULL << (2 + 4 * 1);
    //GPIOC_ODR |= 0x01 << 1;

    AFIO_EXTICR1 |= EXTI_PORT_C << (4 * 1);
}

#define EXTI_IMR (*((uint32_t *) (0x40010400 + 0x00)))
#define EXTI_RTSR (*((uint32_t *) (0x40010400 + 0x08)))
#define EXTI_FTSR (*((uint32_t *) (0x40010400 + 0x0C)))
#define EXTI_PR (*((uint32_t *) (0x40010400 + 0x14)))

#define MR_NOT_MASKED 0x01
#define TR_ENABLED 0x01
#define TF_ENABLED 0x01

void init_EXTI()
{

    EXTI_IMR |= MR_NOT_MASKED << 1;
    EXTI_RTSR |= TR_ENABLED << 1;
    //EXTI_FTSR |= TF_ENABLED << 1;
}

#define NVIC_ISER0 (*((uint32_t *) (0xE000E100 + 0x00)))

#define SETENA 0x01

void init_NVIC()
{

    NVIC_ISER0 = SETENA << 7;
}

int counter = 3;

void process_button_click()
{

        if(--counter == 0)
        {
            // Stanje diode menjamo na svaki treci pritisak dugmeta
            GPIOC_ODR ^= 0x01;
            counter = 3;

        }

}

void exti_1_handler()
{

    if((EXTI_PR & 0x02) != 0)
    {
        EXTI_PR = 0x02;

        process_button_click();

    }
}

int main()
{
    init_GPIOC();
    init_EXTI();
    init_NVIC();

    while (1)
    {

    }

}


texts: Why do transistor transmitters not have base resistor connected to collector instead of vcc?

texts:
I was researching here on transistor amplifiers:

http://www.talkingelectronics.com/projects/TheTransistorAmplifier/TheTransistorAmplifier-P1.html#Stage and they were talking about these two transistor amplifiers. I use the one on the left because my circuits function better.

When I built my regen receiver, it utilized negative feedback in all stages and the circuit operated fine. If however, I took the class C approach, then the regen wouldn't oscillate as well.

I then read on the site in regards to the circuit on the right:

  This stage produces the maximum voltage amplification but it is very difficult to "set-up" because the value of the base resistor will either make the collector voltage nearly zero or full rail voltage. It is very difficult to get the collector to sit at mid rail.
   If the base resistor is a high value, the collector will sit at rail voltage.  If the base resistor is a low value, the collector will sit a 0v.
   If a transistor with a different gain is fitted, the collector voltage will change completely.
   If it sits at mid-rail, the noise produced by the transistor will make the collector voltage rise and fall and produce a lot of noise.

In a transmitter, I want to be able to transmit the signal I want, not a bunch of random noise that a transistor produces.

I then go find a random transmitter design from the internet and resistor R4 is connected from base to VCC instead of from base to collector of the same transistor. Why is that?


texts: Portable Speaker Powered by Battery and Power Supply Separately but Can Charge the Battery From the Same Power Supply

texts:
I'm building a portable speaker using a PAM8403 amp, 3.7v battery, and a battery charging module, all powered by USB input. What I want to do is be able to switch between

1) charging the battery from USB input

2) Power amp just from 3.7v battery.

3) power amp just from USB input(So when it is plugged into the wall it runs 5v. to the amp and gives it more power than when running off the battery).

I can't figure out how to do this without using switch for the battery, the power input, and to turn it all on and off. so many switches would be very user friendly. Is there a way to do this with less switches?


texts:
I was recently diagnosed with Type 1 diabetes. With the need to test my own blood upwards of 8 times a day I have a ton of data to keep track of. My testing unit has the ability to upload its data to a mobile (OTG) or PC (USB).

Sadly, the company who makes the unit does not ship either cable. They are an expensive accessory.

I have enough parts, and should be able to make this, however it's proving difficult.

The USB cable of theirs has windows drivers built into the cable. I was able to get a helpful person at the manufacturer to send me those. That person also told me that OTG wouldn't require drivers.

The photo of both cables on their website show the unit end of the cable as being a 2.5mm (3 ringed) audio jack.

So far I cut open a male USB, I also did the same with the end of an old 3.5mm headphone jack. I then purchased a 3.5mm to 2.5mm adapter. But I'm struggling with the wiring, and trial and error is not producing any results for OTG or USB. I'm also a little concerned that I'll damage my phone, laptop or blood glucose unit. Although all seems to be well after my tinkering.

My USB has Green (Data), White (Data), Red (5v), Black (Earth) and some sheilding by the looks of it.
My 3.5mm headphone cable has Red (Normally right audio), Yellow (Normally left audio) and White (Earth)
I also have a USB to OTG adapter

Note that my adapter has 4 rings, like an ipod shuffle cable or headphones with a mic. I'm assuming that's not introducing any crossed wires as using it for audio still delivers full stereo.

Here are some pics

Am I missing something in my approach? If not, how can I figure out which wires connect to which? I would be happy with either a working OTG or USB cable. My tests have shown no response in the mobile app, and only generated USB malfunction errors in Windows (as expected).

Edit: Thanks for all the really good info. I have contacted CareSens for a NFC unit. I will update here when I find out more. This was going to be a fun project during my time off, but it looks like it's a bit more complicated than I first thought.


texts:
Has anyone used a SpokePOV in the rain?
Will they survive wet weather?


texts: What does this symbol with white rectangles around my vias mean in Altium?

texts: I'm doing a PCB in Altium and I don't know what these white rectangles beside my vias are meant to indicate. A screen shot is below: