texts:
The input signal is simply composite sync signal, without any additional video information. It is CMOS - 0 to 5V levels. I need the same type of signal to appear in the cable along with the RGB lines.

The difficulties I face relate to the best way to tranform the signal - in terms of level and impedance.

First, the 5V CMOS signal can be easily transformed into 300 mV-pp or 600 mV-pp signal using simple resistor network, not introducing much currents and affecting logic output of the previous chip:

Vref will simply be a positive supply rail, and I can, and most probably will, DC bias the resulting signal somwhere within 1-2 V (relatively far away from the power rails).

As for the operational amplifier, I would be very happy using ADA4891 device for the purpose.

And then I have difficulties to decide how to proceed, as I need to match output impedance of the operational amplifier with the cables' impedance (75 Ohms).

Use G=+2 configuration. I will make input signal 300 mV-pp, and it will be converted to 600 mV-pp, and then divided back to 300 mV-pp by the 75-Ohm resistor network.

However my environment does assume single supply power. I read somewhere (e.g. here) that putting gain resistor onto the ground in this configuration is bad idea as it creates unnecessary currents from the output to ground (=to negative power rail of opamp), and capacitor must be used. Then it is stated that gain and capacitor will form a filter which will change the frequency response of the circuit. That sounds somehow complicated. I reviewed a number of sources and some of them signify these problems, but most just connect Rg onto the ground without further exploring the issues.

Use G=+1. It will be as simple as voltage follower, with no relation of the feedback to the power rails. I will make input signal as 600 mV-pp, and just translate it to 600 mV-pp at the output with low impedance - and then divided to 300 mV-pp by the 75 Ohm resistor network. That would be so simple if datasheet would not constantly recommend using this operational amplifier in G=+2 configuration for the video, even in its headline, e.g. Video specifications (G = +2, RL = 150 Ω).

Can I use the op-amp in G=+1 configuration as explained in point 2 and what risks will it present? Probaly datasheet has technical information on it, but I am unable to derive it out of there. Analysing plots does not give me any warning signs of possible problems...


texts: How to calculate a mosfet's maximum usable amperage based on a temperature

texts:
With 3.3v at the gate & 12v at the drain, how many milliAmpere can i let flow trough this mosfet keeping it at a resonable temperature?

and

What is a resonable temperature ?

40,60,80 or more °C

I just salvaged 3
IRLL3303 n-type mosfets. And a friend asked me if i could make him a rgb led lamp (for free). I'm trying to figrue out how many amperes i could let flow trough those mosfets but also keeping a low temperature.

i'm using a 3.3v mcu.
the volatage for the led strips is 12v.
everything should kept at a resonable temperature even in summer (max 37°C room temp).

I tried different calculations from various sites but i always get different values and most of the time i can't find all the variables needed in the datasheet.

I linked the datasheet but here is the important stuff:

  RDS(on) 0.045Ω (VGS = 4.5V, ID = 2.3A) but i use 3.3v on the gate.

  Power Dissipation (PCB Mount) 1.0 W

  Linear Derating Factor (PCB Mount) 8.3 mW/°C

  Junction and Storage Temperature Range -55 to + 150 °C

  Junction-to-Amb. (PCB Mount, steady state) normal=93°C/W max=120°C/W


texts:
I've been planning to make an aux cable for my BMW 3-series, because the original costs 80€...
So I've read a couple of DIY and I've found this

So I've ordered the cable, capacitors, and the resistor, but they sent me the 22uF capacitors instead of 0,22uF....
I just want to know what difference would it make if I were to install the 22uF ones, and would it work?

The capacitor i received:
Thank you for your help


texts: BLDC Current Driver Encountering Current Problems

texts:
The attached Schematic uses 6 N Channel Power Mosfets "IRL3303". I have wound my inrunner bldc motor with 180 windings per phase using a 26 Gauge Magnetic Wire. My motor is a 6 pole 2 magnets machine. The encountered problem is defined below.

Q. The mosfet being used has a Vgs Threshold as 1V. Arduino outputs are being used to power the mosfets(state-machine). Even at 15V VCC the drawn current by the motor is around 0.6AMPS. I have checked the winding connections seperately and it draws 2Amps at around 3-4V. My resistance per phase is around 5ohm and inductance 1.5mH. I have no clue how to fix it. Your input would be really appreciated. Thanks


texts: How to calculate wattage with a 2 way speaker

texts:
I have bought a DIY 2 way speaker kit (Seas Indunne) and cant figure out how many watts I need out of a channel to drive it.

It uses a woofer that is rated for 80 watts long term/250 watts short term
and a tweeter that is rated for 55 watts long term/150 watts short term


texts: Arbitrary direction of current Kirchhoff's Current Law

texts:
In the circuit shown, polarity across the top resistor is given. The question asks the value of \$V_0\$.

The answer given is \$-11.905 V\$. The answer can be found by assuming the current flows as the direction indicated in the diagram below, and after applying Kirchhoff's Current Law at node A: \$25+2V_0+V_0/10=0\$

But if I change the direction of either of the sideway currents, \$25-2V_0+V_0/10=0\$ the answer obtained will be different, \$13.158V\$, which is wrong.

In the textbook it reads direction of the currents can be assumed since, if the actual direction of a quantity is opposite to your assumption, the resulting quantity will have a negative sign, while having the correct magnitude. But this is not the case in my working.

Is it because the direction of the current depends on the polarity of the elements, which are already given? So let say someone has already assumed the polarity of individual elements, if I am to continue the calculation, the direction of the current must follow the sign convention?

Let say the polarity of the top resistor weren't given at first. And I assume opposite polarity at the top resistor as below:

Then I follow the sign convention for the current flow,

so, \$25+2V_0-V_0/10=0\$ the answer turns out to be \$-13.158V\$, which is wrong again. My question is, for the circuit below:

If the polarity of the top resistor is not given, is there only a unique value or more than one values of \$V_0\$ that will satisfy the circuit above? Or the information given regarding to the circuit is not sufficient enough for us to deduce the value of \$V_0\$?


texts: Altium : Default Visible Parameters in Sch library

texts:
I have difficulties with one parameters which constantly appear when I import a component from a Supplier Search to a library Parameters, this is the parameters Supplier Part Number 1 which automatically appear in the main PCb schematic Library editor when I import a part.

I have been into DXP Preferences Schematic Default Primitives and success to manage with other Parameters by scrolling and editing parameters in the list but I don't find the Supplier Part Number 1.
When I double click on the component I see that the parameters list make this Supplier Part Number 1 paramters automatically Visible.

I don't understand what's wrong here. I have been to the online documentation already but don't find on how to manage with visibility of those parameters who are already imported from the supplier search module.

Does anybody can let me know how to modify this ?


texts: Any obvious problems with this DIY home automation?

texts:
I'd like to know if anyone can spot any serious electrical issues in what I'm trying to do from an electrical viewpoint.

Youtube Demo

http://www.youtube.com/watch?v=BmsdXMbd2vo

Short version:

I have 220V relays in the house, connected to lights and 220V push buttons
I want to add an Arduino-controller 220V relay connected to the first one to send short "pulses" of 220V to toggle the existing ones on and off
By adding the Arduino-relay in parallel with existing switches i leave the original 'system' intact - if the Arduino stops working I can still use the lights normally, only losing the automation
To detect the state of a light, I plan on using ACS712 hall-effect modules

I'm good with writing software, but a novice regarding the electrical side of things.

Almost all lights are temporary push-buttons connected to a 220V relay
Two locations in the house where all the wires are connected
adding a 220V relay in series with the normal light switches, connecting it to an Arduino
A 30 amp current sensor is used for detecting the state of the light switch
Each Arduino (or at least one in a pack of many Arduinos - where one won't be enough) Ethernet shield is used to send/receive data over a closed network (not accessible from LAN/internet)

The 220V relay that are set up right now were put into place to allow lights to be opened or closed from multiple places from a room. Think of the relay as a 3-sided control circuit

One side has the 220V mains coming in
One side has the push buttons that work on 220V
One side has the output to the light bulb

The 220V is an on/off relay. Each time any button is pushed, it toggles its state, as long as you press a button more than 0.1 seconds (so it said in the relay manual).

My electrician installed the 220V relay, it is not 'normally open' or 'normally closed'. If power goes down and then comes back the lights return to their previous states.

The Arduino-relay has a 5V side for the Arduino, a 220V side for the mains and each relay is rated to 20A at 220V. From my calculations a 100W light bulb is around 0.5A, and I am using 30W lights so I have plenty of margin for error.

To trigger the 220V mains relay all I have to do is use a normally-open Arduino-relay and trigger the closed state for more than 0.1 seconds. I just need to send a 220V "pulse" to the 220V relay.

This is the main reason that the lights will still work as long as power is kept. All the Arduino can fail and the normal lights will work as usual, I will only lose the remote-control possibility and advanced scheduling/scripting.

More information posted on the home improvement board but what I did not post here is not as important from an electrical point of view.

Forgot to put in the picture:

the top red line coming to the 220v relay is from the mains
the red lines on the left and down side of the 220v relay always have 220v on them.

** Youtube Demo **
http://www.youtube.com/watch?v=BmsdXMbd2vo


texts: CANBUS keypad is not operational after power reset

texts:
I have a 6 button keypad from Greyhill. It can CANOPEN enabled and works fine in my CAN network.
But, sometimes when we power off the system overnight, and power it back up in the morning, this keypad is completely unresponsive. Typically we have to power-reset 3-4 times or do other things like press another button on the system, re-connect the PLC etc. to finally make it responsive.
So, since this is so random, I have not been able to put my finger on what might be causing this behavior. I tried using PCAN view for debugging but all is fine on the CAN network and all other CAN devices on the network work fine.
Any ideas is I am missing some key concept here? I do send a message from my PLC to wake up the keypad in every duty cycle.
Please also note that the keypad works completely fine without any issues once it becomes responsive.
Looking forward to absorb your expertise!


texts:
I'm currently trying to adapt a single li-ion battery charger based on the TP4056 to work with charging more than one battery. The idea is to use a logic circuit that is controlled by the IC's "FULL" output signal. Whenever the first battery is charged, the signal goes high and an LED switches on; the logic should then switch such that the charger is then connected to the second battery. Whenever that is charged, the charger should switch off (rather than switching back to the first, to avoid rapid switching). This has proved more difficult than I expected to design.

RM TP4056 datasheet here - presumably what you had in mind?

A friend of mine designed a circuit that should apparently do the trick, although it doesn't factor in propagation times and has one or two wrong connections which he later pointed out.

(source: pomf.se)

This is what he said about it:

  ah I think I wired the outputs wrong.
  Like I said, I was being lazy.
  X3 stays off while something needs charged
  X4, which isn't connected switches between a and b.
  so those two wires and the inverter connected to the leds should go to x4 not x3

With these in mind, is this circuit likely to work (once appropriate delay is used in case propagation times compromise switching)? It seems to me that the 3-input OR is a overkill, and that the same thing would be achieved by removing the left-most rail (indicated by X1), replacing the 3-input OR with a 2-input, changing the NAND at the top to a NOT, and removing the connection between the X1 rail and the U1 OR gate. Please advise.


texts: Would a triangle wave have finite or infinite sinusoidal components?

texts:
A discontinuity causes a signal to have infinite sinusoidal components, but a triangle wave is continuous, I was taking a class in which an instructor said that since the triangle wave is continuous it can be represented by a finite number of sine components and also showed a finite addition of multiple frequencies of sinusoids which did give the shape of a pure triangle wave.

The only problem I have in mind is that the derivative of a triangle wave is not continuous as it is a square wave and hence would need infinite sum of sinusoids so if one derivates the both sides of the formula of the Fourier series of a triangle wave, we would get a square wave being shown as a sum of finite number of sinusoids. Would that not be incorrect?


texts: What seems to be the issue with this simple diode bridge rectifier with smooth capacitor?

texts:
I don't know if it is some limitation on the simulator, or my mistake, but I am trying to build this circuit:

But this is what I get:

For some reason, the voltage at the marker 5V_DC only gets one positive half-cycle, at a peak of 34.80mA. I was expecting 50mA 5v / 100ohm or 36mA [5v - 0.7v - 0.7v]/100ohm , not 34.80mA.

And the current at the LOAD is not smooth, despite the capacitor being there.


texts: I see that the computational and bandwidth roofs are calculated based on the total amount of available resources (i.e. DSPs) and total possible bandwidth of all buses (i.e. high performance RAM-DMA interfaces), respectively. With my vague understanding of the roofline model, I was wondering if it would be correct to calculate the above based on the actual number of utilized resources and bandwidth dedicated for a specific application? This would assume that the remaining resources are reserved for other applications and are unavailable for maximizing the performance. Also, does it make sense to characterize a hardware module in this matter, or the roofline model only applies to an FPGA device as a whole?


texts:
I was hoping someone could point me in the right direction.  I have a Wind Vane that uses a 360 degree potentiometer as the sensor. The voltage produced at the arm of the pot is proportional to the wind direction.  The arm of the pot is connected to the ADC of an Arduino where the software takes care of converting the voltage to a wind direction.  All this works great with one exception.  The potentiometer has a small deadzone.  I assumed that when the arm was in contact with the deadzone I would get a 0 reading hence the R2 pull-down resistor but unfortunately it jumps around in the 50 to 100mv range according to the ADC.   I should add that the circuit is part of the wind vane assembly and not my design.

So, my problem is when the arm of the pot is in the deadzone, the ADC is sensing a voltage where none should exist.  I have tried a few things, I added a small capacitor across the arm and ground which seemed to help but not eliminate it.  I also added a buffer amplifier in between the ADC and the pot because but it had no effect rather made it worse. What I can do to eliminate this noise(?).  Could the diodes in the circuit be causing this?


texts: Amplifying the signal from a transponder detection loop

texts:
Transponder

I have a simple powered transponder which sends data using binary phase-shift keying (BPSK) on a 5Mhz carrier with a required range of 6-12 inches.  It is used to time laps of remote controlled cars and go-karts.  It has an inductor on the PCB as the transmitting antenna and looks like the below:

5Mhz BPSK transponder http://edeca.net/temp/photos/IMG_0638.jpg

Receiver

Right now the receiver uses a loop of stranded 24AWG wire.  This directly connects to a small transistor amplifier that is powered over coax.  The loop has to be tuned using the blue jumpers to adjust the amount of capacitance, making it resonant around 5Mhz.  This is dependant on the length of the loop.

Loop amplifier http://edeca.net/temp/photos/IMG_0640.jpg

The signal is sent back over the coax to another transistor amplifier and fed into digital demodulation.

Instructions for a professional equivalent show the below, point #3 is a 470 ohm resistor (presumably a virtual ground).  The width of the track is "max 10 metres", which could mean a length of anything from a few metres to >20 metres, with no adjustments required by the operator.

Test loop http://edeca.net/temp/photos/AMB_loop.png

I notice that this is very similar to what radio hams call a beverage antenna.  These are usually at least a wavelength long, impractical at 5Mhz because one wavelength is 60 metres.  However this made me wonder if it would be possible to use the loop more like an RF antenna rather than a fully tuned resonant circuit.

I have made a small test circuit which includes a balun wound on a suitable ferrite for the frequency, converting from 470 ohms to 75 ohms impedance of the coax.

Test loop http://edeca.net/temp/photos/Test_loop.jpg

My thoughts were to amplify and band-pass filter what comes off the loop, this is my starting point for removing the powered transistor amplifier.  This could hopefully reduce the total cost and will make it easier to operate.

So my question: if this is practical, how should I amplify the signal at the receiver?


texts:
I have a working custom motor controller for three phase sensorless bldc motors.  I've implemented open loop speed control, where the duty cycle is changed to change speed.  I've also implemented a closed loop PI speed controller where an RPM is set as a set point.  Now I would like to design a controller that closes the loop around torque/current.  I know this is possible with Field Oriented Control, but I need to spin at rather high RPM's so I'm trying to avoid this more complex algorithm.

I have been trying to use one phase current measurement to estimate the average current going to the motor and vary the duty cycle based on current error.  I am having some problems with stability and can't decide if it's due to a poor estimation of dc current, or if the transfer function from voltage to current might require some more controller design than I actually did(read none).

Main Questions:  Is this a valid approach to BLDC torque control, if not why specifically?  Are there alternatives to FOC for BLDC torque control?

Edit:

With Guy Sirton's info, I suppose I am going about it backwards from what is typical.  I hoped that if I only wanted to maintain a constant bus current I could slow the current loop way down (100 - 300 hz)and make it my outer loop.  With this in mind I just used the phase current to approximate the current coming from the power supply.  It may be true that due to the dynamics of the system, this slow measure of current is not sufficient.  It also may be true that I just need to put more thought into the controller, since there is really another integral between the input and the output(speed being proportional to voltage and current proportional to acceleration).  What is mentioned in the drivetechinc article at the very end is what I understood to be FOC.


texts: Can someone clarify how to charge a battery without an off-the-shelf battery charger?

texts:
I am a college sophomore studying EE, I am currently working on making a simple battery charger circuit for an integrated device. The device has 3 Li-Ion batteries in series for my motors, and a single cell by itself for the circuitry. I have been doing some research on charging techniques. I have seen a couple charge controller ICs and some simple schematics. I am trying to square away all aspects of charging a battery. I currently understand that a battery should be charged at its rated voltage (say 4.2V for a single cell) and that you should try to limit the current so that the battery doesn't overheat.

I have some uncertainties about how exactly to charge batteries. I was thinking that I could try plugging in the a battery to my voltage supply, setting it to 4.2V, and limiting the current to something manageable, then when the battery gets to 4.2V there will be no potential difference and the battery will stop being charged.

I was wondering if all of that is true. If not, what is the best method to stop charging a battery?


texts:
I would like to design an nxn IR long range break beam sensors and place them on a table with receiver at one side and transmitter over the other

Length of the table is 155 cm and width is about 140 cm.

The idea is, to place an array of IR break beam sensors.
Any object that falls within the IR grid, needs to be detected and the signal needs to be sent to an arduino / micro controller

Below is a high level sketch:

Objects that needs to detected within the IR grid ,are  of ping pong ball sizes
I need to send the output(whether a beam got broken or not) in the digital form to a micro controller
Finally, from the micro controller ,i am planning to transmit the data via blue-tooth to a smartphone.

I have just started to think about 2)

Did some googling and came across this https://youtube.com/watch?v=1vBegJTG-vE&t=7s

In my case, i will have to use multiple such sensors.

Could anyone throw me some pointers on the direction i need to take ?
Do i need to design a PCB which would comprise of several sensors?


texts:
How to measure phase difference of two signals of the same frequency in an FPGA?

For instance, say I have two 150 MHz signals (internal to the FPGA) that are synchronous to each other, but they are offset by some constant phase difference, how would I be able to measure this?

I have researched existing methods of a time-to-digital converter on an FPGA, but those mostly concern two one-time start and stop signals and measuring the time between those two events. I wonder if there's better method if we know that the signals are repeating with a constant phase difference?


texts: 12v circuit that turns off after 30 seconds

texts:
I (am seeking design help with building) a vehicle 12v circuit with blinking LED that turns off after 30 seconds, that plugs into the cigarette lighter socket. It stays off until the vehicle power is turned off and then turned back on again. Basically, every time I get into my vehicle and turn it on, I want the LED to blink for 30 seconds and stay off until the next time I get into the vehicle and start it.
Thank you for your assistance.
Ron
(edited above thanks to Eugene's question)


texts: Run heater on two powerlines, where the second line is switched according to the main line

texts:
I got a water heater which is rated 6kW. The "heating element" consists of 3 heating elements that are connected in series for 1-phase usage.

I would like to run two of those heating elements on one phase and the 3rd on a second phase to reduce the maximum load on a single phase (due to 3 x 25A total house connection). As the heater is rated for 230V, I cannot simply connect the heater to 3-phase electricity.

What kind of electronic module (diode?) can be safely used to switch the 3rd 2kW heating element when the first two are turned on and off? So that I can keep using the original control unit of the heater, but the 3rd heating unit runs on an independent cable + phase.

The installation will be done by a professional electrician, probably he will have his own simple solution, I don't know yet. I just want to have a suggestion for a cost effective solution on hand. Of course, for the electrician the most simple solution is to install a 40A 1-phase power line, but for me this solution is quite expensive, as in this case the main house connection has to be upgraded and a new main cable has to be installed = $$$.

EDIT/UPDATE: the 3 heating elements are connected in parallel, yet the heater is a 230V device, but it's controller has only 4-point input connector( L L N N ). Still I want one of the three heating elements to be connected to a separate phase to reduce the load on a single phase. But this third heating element should still operate according to the controller - so turn on and off when the controller turns on and off the first two elements.

Do I see it right, that I can simply connect two phases to the main input connection it says N N L L(see 2. picture top right corner)? Could this have some effect on the controlling unit?

Edit: Added a diagram from the manual, but don't believe what it says, because this same model is also available as 3-phase model, so I guess the diagram has not been edited for two version.

EDIT: So I want to go the 3phase way. I repositioned some of the cables according to the diagram for 3ph usage(see photo). However a few questions remain:

Do I use the 3phase connection with a single neutral or is it safer to use 3 isolated phases with each having its own neutral?
As this is not a motor, does it matter in which sequence the phases are connected?
I wanted to identify which two heating element connectors belong to each other. I thought, I just measure the resistance and the pairs with resistance lower than infinity will be my pairs - BUT I measure a measurable small resistance between any two of the six heating elements connections. If I measure the resistance between any of the power input and any of the N connectors I get a resistance of approx 28 Ohms, but when I measure the resistance between two power input connectors the resistance is just around 50 Ohms, where I would have expected it to be infinity. Is this all right or is this device badly isolated?
So what is the way to determine which two heating element connections belong together?

Edit: Looked through the manual - found this "choose the proper heater (220V or 380V). The heater and the board will be damaged if 380V were connected to the 220V unit". Is this sure nonsense or could it be that the board has and electronic design that does not allow 3-phase usage?

That brings me back to my original question, is there a ready to use module that lets current through only when on it's input current is applied?
That way I could leave the unit with 230V and just connect the two other phases directly to the other two heating elements through such a switching device.

Edit: @Tyler brought contactors to my attention, this is exactly the kind of device I was looking for.

[][]2[]3[]4[]5[]6[]7


texts: Choosing a suitable power supply for a MOSFET driver chip

texts:
I would like to use the TC4427 MOSFET driver chip, in order to switch the current through the IGBT AUIRG4PH50S, which will be placed in series with a resistive load. The power supply providing the main current through the load will be around 1V, and 100A. Another detail is that I would like to have up to x8 IGBTs (each with their own TC4427) - in parallel, to handle higher total currents through the main load. All x8 of these IGBTs will then be switched at the same time. The load will be being switched only around once per second.

The TC4427 will drive the gate of the IGBT up to +15V when "on", and so I need to choose a +15V supply to power the VDD pin of the TC4427. To isolate the supply from other parts of the circuit, I would like this +15V supply to be an isolating DCDC converter (this DCDC converter power supply is seperate to the one providing the main current through the load, although they share the same ground.)

My question is how to choose the power capability of this DCDC converter in Watts? The datasheet for the TC4427 says peak output current of 1.5A - does this mean that during the switching process the +15V DCDC converter will need to provide P = (1.5A x 15V) = 22.5W for each IGBT? Or would I have to somehow calculate the actual current output by the driver based on the gate capacitance of this particular model of IGBT?

I am looking at something like the XP Power JSM1012S15 (10W, 670mA output), but I am not sure either whether this will be sufficient, or will be completely overkill for this application. Datasheet is here: https://www.xppower.com/fr/Product/JSM10-Series

Any guidance on how to go about calculating these things would be great.

edit:
I later found a useful reference for a breakdown of the various power consumptions of a MOSFET driver: Avoiding MOSFET Driver Overstress
http://ww1.microchip.com/downloads/en/AppNotes/01327A.pdf


texts:
What is the simplest way to turn a regulated continuous analog DC +12 V (+/- 0.2 V) input signal into a 0 V output signal, and likewise turn a 0 V input signal into a +12V output signal?
Two separate sources are available for use, the first for driving the input signal at 12V+, or 0 V (when source is open circuited). The second for driving the output signal at 0 V (open circuit) or 12V+ nominal.
The first source is regulated to 12V +/- 0.2V or 0 V, the second source is unregulated 11.9 - 15 V.
The final detection circuit that will read the output signal considers 8.5V - 15V as a HIGH state. Anything below 8.5 V it registers as LOW.
Continuously-energized NC signal relays are undesirable due to duty cycle concerns (100% duty for months or even years), although some are rated for it and they may be the best solution. System is for safety purposes, so reliability is important.
I am looking for low power consumption, capable of withstanding -40°C to +85°C, reasonable amount of vibration tolerance, ideally a ready-made solution with minimal manual assembly and possible failure points.
Transistor inverter? Op amp comparator? Something else?


texts: How do I wire a relay board into existing series recepticles

texts: I have a four channel relay, that I'm going to attempt to wire into a terminal block. I have experience with mains wiring and some experience with electronics, but no experience wiring relays. Basically I have a number of receptacles that are wired in series. I would like to rewire them so that the relays can switch each one on and off. I'm assuming that it would break one of the wires with the relay, but I'm confused about what to do with the other wire. or the other terminal. Can I break just one side of the circuit? and leave the other side connected in series? or is there some inherent danger in that. Attached is a photo of the receptacles, and the relay.


texts: Noise on my oscilloscope when probing a wire

texts:
I am prototyping a NTC voltage divider circuit and I am having trouble with noise on my probe. It seems like I am constantly getting a large amount of noise (200-300mv) on my oscilloscope waveform even when all I am doing is probing a small wire. 200-300 mV is a lot isn't it? I feel like I can't really gauge the actually noisiness of an analog signal if my oscilloscope always has this minimum 200mV p2p noise on it.

Where is this noise coming from, and what can I do to remove it?

EDIT: Here are some more picture of the calibrating probe:

Zoomed in:

There seems to be a constant 50mV p2p noise signal when calibrating...


texts: Input and Output Impedance parameters of two port network

texts:
I am reading about two port network and I come to about Z-parametrs

$$\begin{bmatrix} \mathbf{V_1}  \\ \mathbf{V_2}  \end{bmatrix}=\begin{bmatrix} \mathbf{Z_{11}} & \mathbf{Z_{12}} \\ \mathbf{Z_{21}} & \mathbf{Z_{22}} \end{bmatrix} .\begin{bmatrix} \mathbf{I_1}  \\ \mathbf{I_2}  \end{bmatrix} $$

but then it introduces the concept of input and output impedance which is $$Z_{in} = Z_{11}-\frac{Z_{12}Z_{21}}{Z_{22}+Z_L}$$and also $$Z_{out} = Z_{22}-\frac{Z_{12}Z_{21}}{Z_{11}+Z_S}$$
Where \$Z_L\$ is load impedance and \$Z_S\$ is source impedance.
I don't know how writer concluded these impedance. Please provide me the explanation.


texts: Input and output power of ZVS not understood

texts:
I am trying to learn electronics and came across these ZVS drivers, which seem quite elementary. I understand what an inductor and a capacitor is (although obviously I don't know all the concepts). My questions is this: how can a ZVS driver heater with like an input of 12 V and 2-10 A (depending on what you put inside of the coil) output like 70 V and 30 A on the output?
Is there some kind of factor I am not seeing? Because otherwise how can one go from 120 W (12 * 10) to 2100 W (70 * 30).
This video of a well known engineer does not explain this 'gain' of power other than just saying it is reactive power (oscillation). https://www.youtube.com/watch?v=hFJeIt_JcEc
Just a simple explanation or a link would make me very happy :)


texts: Buck converter in pspice output value changes depending on the resistance. How do I correct this?

texts: I am trying to design a buck converter and simulate in pspice, however I am running into trouble. The voltage on the load (R1), varies significantly when the load value changes. How do I correct this problem and output a steady 5V?


texts: Active High and Low in Combinational Logic Analysis

texts:
I'm working through Joseph Cavanagh's Digital Design and Verilog HDL Fundamentals. In chapter 3, he discusses using (+) and (-) in front of bits to indicate active high and active low signals, i.e.

I understand the concept of active low, where a logical 0 is a TRUE.  And I think I understand what he's saying for figure (a), the equation is -z1 = (x1x2), and for (b), in order to get -z1, the active low signal, the equation is (x1x2').  What I want to make sure I understand are the semantics, for lack of a better term, of figure (b).  x1 is active high, x2, because of the (-) is active low, so in order to drive z1 low (i.e., -z1), x2 has to be negated so that -x2 becomes x2 (i.e, x2').
I was interpreting figure (b) as NAND(1, 0) = z1, and what we want is NAND(1, 0') = -z1, but the discussion of active high and active low was confusing me.  I think what I would like is confirmation my interpretation of figures (a) and (b) are correct.  Or that I am over analysing this.


texts: Measuring smartphone's battery State-of-Charge during charging

texts:
I'm designing a mobile device that uses a Li-Ion battery.
It is required to indicate to the user the State-of-Charge of the battery, similar to how it's done in smartphones.

At first I considered simply measuring the voltage of the battery. It doesn't decrease linearly with the SoC, so I figured I'd use a look-up-table in order to convert the voltage to the correct SoC.
This approach obviously fails when the device is being charged: an external voltage is forced on the battery, and so there's no point in measuring its voltage.
After reading several articles on-line, I figured that Coloumb counting has to be the way they do it in smartphones, since charging doesn't interfere with it, and it doesn't require sensing of internal chemical properties of the battery.

My question is: how is it usually realized in smartphones?
Do they use a serial current sensing resistor, whose voltage is amplified and read by an A/D? Does the smartphone processor do the integration, calibration and other calculation, or is there a specialized IC for that purpose? If there was, I'd love to use it!


texts: Why does a capacitor create a 90 degree phase shift of voltage and current?

texts:
First look at my circuit. The voltage source has a value of 5V with a phase angle of zero, and the capacitor's impedance is 5Ω. So the current is obviously 1A with a phase angle of 90°.

What is the physical reason behind this phase shift? I can prove mathematically that a capacitor can make a 90° leading phase shift. But I want to know the physical reason for it.


texts: Circuit for measuring high voltage DC voltage (up to 1000V)

texts: I am  a final year E&E student and I am trying to built a power meter that must be able to measure quite high DC voltages, up to 1000 V DC. I am measuring with a simple 12-bit ADC that has an input voltage range of 0 - 2.5 V. Would a simple voltage divider and op-amp buffer be sufficient for the application or is there another type of front end analog circuitry needed because the voltage is that high?


texts:
Beginner Warning!

I am trying to automate lights and fan in my house with the help of a raspberry pi. I read couple of guides in the internet. I finished the basic circuit. Now I can control a relay with my pi remotely.  If I connect the relay in Line, I will be able to control my light but for some reason i cant power my pi or relay I will not be to turn on my light

simulate this circuit – Schematic created using CircuitLab

Another solution is I will connect the switch directly to light and another line through relay. So if i turn on the switch my light works & if I enable the relay my light works. Will this work? or Will it damage my relay?

simulate this circuit

Here is the relay i am using


texts:
I'm admitting here that I'm a little out of my element, so take that into consideration.
I am working on a project that combines a few different electrical devices that use different DC power sources. To try and simplify and reduce the number of AC to DC plugs needed, I'm hoping I can just do some creative converting. Two lamps need output power of 12V 1A DC. The other device (light strip) has a power requirement of 24V 0.83A.
Is there some sort of converter I could use to either step up the light strip or step down the two lamps and just power them all from a single plug?
One of the other options would possibly be to convert AC directly to those DC power requirements, but I suspect that might be a little more difficult ultimately.


texts:
I have an old 12V cooler master fan that I am converting into a fume extractor for soldering and am connecting it to a standard 12v computer power supply.  I am trying to wire it and am confused about one thing.

On the fan's label it has a coding for the different wire colors (red, black, and white) and it says:

  red +

  black -

  white FG

I have looked up FG on google all over the place but can't seem to find anything that says what it stands for.  I was thinking that it might be "Ground" but then what would the black negative wire be?  Maybe I just have a fundamental misunderstanding (pretty new to all of this electronics stuff)

I did connect the black wire on the fan to a black wire on my power supply and the red wire on the fan to a yellow wire on the power supply (white wire connected to nothing) and it turned on and seemed to be working fine but I want to make sure that this is actually a correct wiring and isn't going to cause any problems in the future.


texts:
I have a schematic symbol for a micro-controller (40pin) created by a different person. On their schematic, they have pins grouped together in specific order, for example, say pins 1, 5, 23 and 36 are together since they go off to one specific device, then pins 21, 28 and 30 are next, because they go off to a second device, and so on.

I want to configure the pin groups in a different way. How is this done?

I imagine I can edit the schematic drawing itself, and manually move the pins, but is there an alternative way to do this?

Thanks.


texts: How can I set a custom form of my Bill of materials in Eagle

texts:
Actually I have made a schematic and I want to adopt the same format as in this file which was based on database
because when I run bom.ulp I get only a such table :. I know that is something generated using 'Database' and 'Output' but I don't know how to manage it.
Any Help?


texts: SOIC-8 IC input pins small spacing at high voltage

texts:
I'm looking at a high common mode voltage difference amp (AD629). The input voltage between the two input pins next to each other will be 150VDC. Normally the pads should be bigger on the PCB than the actual pin size. So between these two pads is at most 0.6mm space.

I think this isn't enough. Do I have to make a cutout in the PCB? Why do the manufacturers design something like this? One or two NC-pins between the input pins would be very helpful.
Thanks for your help.


texts: I was using an ESP8285 for a project that I started a little bit ago. I had let the project sit for awhile and had lost the documentation including the source code. Is there a way to pull the code out like as a hex file and upload it to a new ESP8285 module that I have?


texts: Could this power supply be causing problems?

texts:
I am using this power supply shown in the datasheet here: RS-D3305P Datasheet
Channel 1 is set to 26V, channel 2 is 5V and channel 3 is set to 3.3V. All the negatives are joined together.
Channel 3 is only used to power an ADC chip (AD7476A) and a pot circuit as the analog input. I have been having trouble getting any decent results from this ADC chip and was starting to wonder if the power supply was noisy. In the datasheet it shows the channel 3 has a load regulation of +-50mV. Is this a bad power supply to power an ADC with?
I am measuring 5mV at the input ADC but reading around 65. Maybe the power supply is adding ripple to it? could be an issue with the timing signals but would like to check out the power supply first.
Note, the ADC chip is 12 bit and the ADC analog input voltage is 3.3V
Below is an schematic for the hardware circuits:

Below is an image of the physical hardware circuit, which is built temporary:

Below is an image of the noise on the ADC input waveform:

Below is an image of of the ADC input voltage waveform in yellow, and the 3.3V in blue:

Conclusion
So I got a perf board soldered up today with the old circuit along with the modifications that has been recommended here in this forum. Honestly I can not believe the difference! The ADC value on the display now flickers at most by 2 bits. Even without any software filtering I can turn the pot to get any value on the display, with one or two at most LSBs of flicker, and at times there is no flicker! I am very happy with the results and can't thank everyone that posted here enough. I will try to summarise my modifications with some pictures to try and help other beginners like myself:

Got rid of the breadboard and soldered the circuit onto some perfboard (I think it is called, see image below). Having soldered traces on the perfboard instead of long flying wires seems to make a massive difference. I tried to follow a start point ground as best I could. It is the node with all the connections in the top left on the bottom of the board.

Tried my best with my limited analog knowledge to separate the analog traces and digital high speed traces by routing them away from each other. Although don't worry just as much about this (obviously don't cross over each other or this probably does matter if you are using a 24-bit ADC lol). When I had the last line which happened to be the SCLK, I ended up having to run it adjacent to the ground trace which isn't recommended, but still seems to work.

I added lots of capacitors, both electrolytic and ceramics across all IC supplies, the ADC pin and the potentiometer wiper. I kept them as close to the Vdd or positive connection for each device. I followed the datasheet for the ADC chip for the decoupling capacitor size, but the rest were just hand picked with whatever I had to be honest.

I added 330 ohm source resistors for the CS and SCLK on the FPGA output pins, and a 330 ohm source resistor on the SDATA right beside the pin on the ADC. The seem to help massively.

I still have flying wires from the ADC chip to the FPGA which you can see below in the pictures, but they are twisted and wrapped in tin foil and they seem noise free, honestly! Touching them has no effect on the ADC output.

Added a 330 ohm resistor directly across the 3.3V supply as was suggested to put a constant small load on the power supply in an attempt to improve it's regulation. Don't know if it made a difference to be honest, but doesn't do any harm. I won't be removing it anyway.

Note, there are different potentiometers used in the pictures, I decided to change it to one with screw connections just. I will post the complete modified schematic tomorrow.
Thanks once again, without this forum I wouldn't have been able to do this, and learn what I have learned.
Below is the top side of the ADC board:

Below is the bottom side of the ADC board:

Below is an image of the board, FPGA and connections:


texts:
I'm designing an integrated VCO for use in an FM Radio frequency PLL. In order to reduce the external part count, I had the idea of using MOSCAPs as the frequency tuning element instead of external varactors. My circuit is given below:
My basic topology is a Colpitts oscillator, with NM0 as the gain device, L0/M0/M1 forming the tank, and M2/M3 as my tuning elements. "vfb" is the tuning voltage, the feedback from the phase detector (i.e. the input to the VCO).

This curve shows the capacitance of my MOSCAPs as a function of bias voltage. The Y-axis is in amps because of the way my testbench is set up --- just imagine it's fF instead of fA. M0 and M1 are both reverse-biased to around -0.5V, while M2 and M3 are biased based on vfb.

And here are my results, from a transient simulation for various values of vfb.

My Question: How much do I need to be concerned by the significant ripple I see in the last figure? And are there any ways I can try to mitigate it in design? Or was my MOSCAP idea flawed from the start? (Note: I did introduce some noise in the simulation in order to get the oscillator to start up.)
Thank you!


texts: what is the approach to design edge triggered d flip flop?

texts: i know the circuit. I implement it using verilog and it giving result correct. like when we have to design any digital circuit we draw truth table. Optimize circuit using K-map and then implement. In case of edge trigger Flip flop( i am considering the easiest flip flop i.e. D flip flop) . How we draw its circuit using gates?


texts:
I have done a couple of prototyping using Wemos D1 Mini and would like to use the ESP-8266 12F Board directly without the devkit. Attached is the schematic for the same. Please let me know if i missed something in the design.

10K resistor for pullup (GPIO-0, Reset, CHPD) & 10K for pull down (GPIO 15) (Is 10K good value)
0.1uf Capacitor at Vcc(is this sufficient)
P2(programming header) connects to tx, rx, vcc & gnd. ( Some suggest to power externally MCU while flashing, which means to disconnect the Vcc from P2 Header Pin 3, not sure about this)
Any other improvements to the circuit.

Appreciate your valuable time & look forward to learn more.


texts: Need a solution: Why does the battery voltage drop for custom PCB?

texts:
I have a custom PCB to control a solenoid or DC motor.
Input voltage 6-7 volts with 4 batteries in series.

I have a few questions:

Why does the voltage drop by 1V to 1.5V when the switch is pressed to rotate solenoid or dc motor for 0.5 seconds?  Can anyone explain and provide a solution so that it doesn't drop?
I tried some non-rechargeable and rechargeable batteries. Almost all non-rechargeable batteries that I tried, the voltage drop was not fast or extreme, while every time I use a battery that can be recharged in one day the voltage drops so that the PC doesn't turn on. After I checked, out of 4 batteries, 2 voltages were in good condition, while 2 batteries dropped as they ran out of voltage.

Could anyone explain and give the cause and what should I check?


texts:
I got some buttons and switches that are for automotive usage, so the LEDs inside are for 12V supply.

Is there a safe and efficient way to power these from an USB connector? I am planning to use an Arduino clone as a controller for these buttons and have the computer recognize it as an USB keyboard. Though, I would like to see the buttons LED on too, without adding an extra wire from an AC adapter just for the lights.

Would that be dangerous for the USB port on the motherboard? I do recall that the max current on USB is 500mA, although I have no info about how much power is needed to power the LED in the buttons (10 of them).

Is this possible and safe, or should I avoid to bump up the voltage of the USB port to power the LEDs?


texts:
I have designed a function generator with the XR2206. That works well.
I can take it up to 2MHz (sacrificing on THD, however).
Where I have failed so far, is the power stage.
I have a supply of +10V/-10V for the power stage.
I would want 1,5-2A max. output current up to 2MHz.
I tried a transistor output stage, but it falls apart beyond 300kHz. Means, the signal is getting worse and worse with higher frequencies.
I tried LM675 and it does its job well. Problem is, it requires a min. gain of 10 to be stable and with the 5,5MHz GBP the amplitude goes down beyond 500kHz.
As I would like to keep the amplitude (gain) stable accross the freq. spectrum I added an LM7171 to boost the LM675. That works well, but with fixed gains for each stage, the amplitude is still going down beyond the 500kHz. Thus I tried feedback across both stages and then they became unstable.
So I hope, that you guys can help me, because I run out of ideas.

How would the schematic for both op-amps in series look like, given the requirement, that the total gain is stable up to 2MHz?
I could add an AB transistor stage to the LM7171 to get the output current. How would that look like? Or rather what transistors would you recommend, which have the necessary performance across the freq. range?
Any other suggestions are welcome.

Thanks in advance.

I can ditch the LM675, but I should have a better replacement. I have looked for long and did not find a better replacement though. Either they don't have the power or the GBP is even lower. The solution might be the LM7171 + transistors. Question is which transistors will deliver the power at 2MHz?
No, I don't have a simulator. Even with a simulator, I would prefer a schematic of an amp, which has been built up in real life before.


texts:
The diagram is from a wall mounted vacuum cleaner.
What can the green thing be and what could its price be so i can replace it?
Can i use 7 x AA NiMh batteries with 4800mAh each at 1.2 V ?
Can i redo the system so it works with the aformentioned new batteries and doesn't overcharge or be set on fire?


texts: nRF52832, using a chip antenna for short range purposes

texts:
In the past I have used nRF51822 to make small low powered devices for projects. I have used allready made modules from china (WT51822-S2) and programmed them using mBed. It was really easy but not really professional.

Now I would like to learn how to program it in Keil and make a costum PCB. Without the module, but with my own, costum solution. The problem is that I do not have that much expiriance designing PCBs, let alone antennas. I've read on a different post on this page that you can't just copy someones design and expect it to come out good.

I've found online that there is a possibility of putting a chip antenna. There are examples on how to use them in their datasheets (on where to position them and how).

Is it possible to just make a centimeter long line (as shown on the picture above), put capacitor in paralel, inductor in series and after that just the chip antenna and not all that components between like shown on the WT51822-S2 module?

Component values (L and C) I just plan to thake from the NRF52832 reference design below. Also, I dont need range further than 4 or 5 meters.

Thank you kind people!


texts: 4x4x4 led cube using mm5451 chips .. need a suggestion on a Mofet or equivalent

texts:
My son and I are building a 4x4x4 cube. We have been planning to use a pair of mm5451 source drain chips to select the columns and were thinking to use mosfets to select and power the tier .. thus lighting the desired LED.

Since the 5451 acts as a current drain .. I am searching for a P channel MOSFET to energize the tier by using an output of the 5451 to bias the MOFET on ( it being connected to a external power supply to manage the current draw).

Is this the best approach?

Assuming yes, what would your suggestion be for a good P-chn Mosfet? ( most that I have found that will handle the external voltage/current, require more than a digital 0-5v system can put on the gate).

Thanks in advance for your help..


texts: TRRS connector with iphone circuit board, how to get mic compatible with PC input (Bose Q25)

texts:
I have a Bose Q25 headset, it uses an iphone compatible trrs jack.
It contains stereo input, mic output and the button controls.

I split it into 2xTRS jacks using a commercial splitter, the mic is still disfunctional.
I tried to contact Bose support and asked them how to connect it to the PC.
Their answer:

  Due to the fact that Bose Corporation is a privately held company, we
  consider the information that you have requested to be proprietary in
  nature.

That's absolutely ridiculous, as if the iphone connector standard would be a proprietary secret. There are hundreds of companies making such connectors/headsets.

However, I am not familiar with it.
Does anyone here have any knowledge how the mic is connected, what sort of circuit would be required to get it compatible with PC input? (either line in or active mic)

I have a standard TRRS headset without buttons (just mic and speakers), that one works flawless. So the button circuit board does something that needs to be taken into account.
It can not be a big thing as all the smart phones (Android as well) can interface with it.

Maybe it's just polarity (I don't want to risk damaging the 300€ headset) or some simple circuit I have to apply to the connector to get the mic through.
Anyone ?

P.S.
As I found Boses answer to be very customer disrespectful (I did not ask for a schematic or the DSP programming..) I would like to keep this question updated until I have it solved so other people can benefit from the information.


texts:
I currently have a circuit that the arduino pro mini checks is the button pressed, the relay will be closed to trigger the bell alarm. And a UDP Packet will be also sent to a server to notify me.

Flow chart:

Circuit:

simulate this circuit – Schematic created using CircuitLab

However, it is a unsafe circuit as if the arduino is not working, the bell alarm will no longer triggered.

Is there a way to just detect is the wire containing current?


texts: Where do you put the gate-protection zener diode in an NMOS H-Bridge?

texts:
Do you even include it for an NMOS H-bridge?

Because typically I've only ever seen them in NMOS/PMOS bridges, not full NMOS bridges.

(Inductive load)

The protection zeners would go here right?


texts: While reading this website, I found out tha there is lack of 'determinism' in the Ethernet network bus as compared to some other buses like 1553. What I understand is that Ethernet is a single master full duplex serial data bus. But I cannot understand what is reason for it to be non-deterministic is data communication? If a terminal A wants to send data to terminal B when both are on the same shared Ethernet bus then A can do that without any chance of missing the data. Then why it is called non-deterministic bus?


texts: Is there any way to determine accurate position of WiFi access points. I have come across many ways about estimating user's position by using received RSSI but can we find the actual physical location of the access point itself by using the RSSI ?


texts:
I have a stepper motor and it is rated at 2 amps per phase. I also have a stepper driver which is rated at 750 miliamps per phase. To make matters worse I have a wall wart power supply rated as 9V @ 650miliamps. That power is converted by a voltage regulator PCB down to a usable 3.3 V at an unknown amperage.

My question is, what effect will underpowering the motor have?
Will it affect the speed of the motor or just holding torque?


texts: Control Design: Continuous State Space vs. Digital State Space --> Feedforward Path

texts:
I have a question regarding the state space representation of a model.

I created a continuous model of my plant in Simulink, which does not contain a direct path from input to output, i.e. the D Matrix is zero. The model contains 3 zeros and 5 poles.

For further computations I have to convert this continuous model into a digital model. I use the bilinear transformation to do so.

The digital transfer function in the z domain contains now 5 zeros and 5 poles, which leads to a nonzero feedforward coefficient D in the state space representation.

I am not surprised that the digital model has more zeros than the continuous model, however, I can't see the connection between my digital model and the 'physical' model in Simulink.
What I want to say is that the real machine does not contain a direct path while the digital representation does. How can I create a understandable linkage between those two representations?

Unfortunately I could not find books/papers about this topic, maybe you can give me a hint?

Thanks in advance for your help!

hypn0


texts:
I'm looking to design or find a high-side current limiter which can operate at 9V and has ability to limit current to a level of 1,5A with a maximum voltage drop of 1V - 1,2V. It should also be able to survive and limit the current when a short-circuit occures in the load.

When it comes to designing a circuit of my own, best option this far is circuits similiar to

http://www.electronicdesign.com/sites/electronicdesign.com/files/uploads/2015/02/IFD2634_F2-big.gif

These circuits typically employ MOSFET and a small current-sense resistor with its signal amplified by an OP.

I'm looking for recommendations and advice on selection of IC/design of a circuit as described above.

P.S

A follow-up question is: With proper, high Vgs and 1,5A of circuit flowing through, how large of a current drop can I expect in a typical MOSFET?


texts: Capacitor in the circuit - Bypass capacitor

texts:
I was trying to measure the supply current of a CAN transceiver during fault conditions, one thing which I noticed was that during CANH to GND(when the current consumption is supposed to be the highest), the current was kind of like a sine wave and going negative during '1' bit transmission(recessive state).
Below is the circuit,

R410 was unmounted and current was measured at Vcc. When I unmounted the bypass capacitor C405 (470nF), I noticed that the current waveform as expected, as in was not going negative during '1' bit trasmission.

Waveform with capacitor :The yellow and pink signals are CANH and CANL signals, the green is the TXD signal from the function generator, the blue signal is the current signal and the last signal is the 'CANH-CANL' difference signal.

Waveform without capacitor:The green is the current signal, blue is the CANH signal, pink and blue are RXD and TXD signals respectively.

I understand that the capacitor was trying to filter and hence the waveform was not a square waveform, but could someone please elaborate , I'm trying to understand why the current is going negative ? (the CAN transceiver is being powered by a 5V regulator, CAN supply current going negative means that the current is being sinked to the 5V regulator ?Is that possible? or is the current flowing through the output capacitor of the 5V regulator be a possibility?)

EDIT :
1)Waveform with 100nF bypass capacitor at the supply pin of the CAN transceiver.
  Yellow is the signal from the function generator, blue is CANH, pink is CANL,
  green is the CAN current.

2)Waveform - normal operation(without the short of CANH to GND)
Yellow is the signal from the function generator, blue is CANH, pink is CANL,
  green is the CAN current.


texts:
I am learning the Serial Communication without much EE background:

The article says:

  The start bit is always indicated by an idle data line going from 1 to
  0, while the stop bit(s) will transition back to the idle state by
  holding the line at 1.

My Questions:

Why start bit must turn an idle data line from 1 to 0? Why not from 0 to 1?
How is idle data line defined? 1 or 0? And why define it that way?

(Logically, I have a feeling that this is totally arbitrary, I don't see reason why cannot designate 0 as the idle state voltage. And I guess if 0 is designed as idle flag, all devices will be in low voltage when idle. And maybe that means less power consumption?)


texts: "Could not find Cortex-M device in the JTAG chain!" (TM4C123g)

texts:
The board was working fine but all of the sudden I can't download any code on it from Keil.
Whenever I try to download code on the board, I get

"Could not find Cortex-M device in the JTAG chain!
Please check the JTAG cable and connection devices"

I tried a couple of different cables but didn't work.
What can be causing the problem?


texts:
I have two 7-segment displays (datasheet here). They are common cathode.  The forward voltage for each segment is 2.0 V.  The continuous forward current is 25 mA.  What I'm looking for is a relatively inexpensive ($3-$4 or less) IC that can drive both of these, using a microcontroller to command it over SPI, or something else that uses few I/O pins.  (I've tried looking on digikey.com for a good solution, but I'm not sure what key words to search exactly, and it's difficult to understand the lingo of the datasheets to find out what a particular IC actually does.
does anyone know of a good display driver or even a shift register that will work well with this display? If not, do you know what keywords or search terms are best to find what I'm looking for?
In summary, the IC I need has to:

Have at least 14 outputs (or can multiplex the 2 7-segment digits)
be able to source 25 mA on each output
able to be controlled with SPI or something else that takes few pins
available in DIP, so I can test it easily on breadboard

Since I am new to sourcing electronics parts for my own projects, I would appreciate any tips on how to read datasheets for relevant information, how to find the exact part I need, or what are some good websites to look for parts on.


texts: How does a USB to DB25 parallel cable work?

texts:
I've been searching for technical information to explain how this works but can't find any info, pinouts, technical reference of any form.

I want to program a parallel port to control a USB device but need some sort of details on the tech behind the conversion. I have a 1979 Exidy Sorcerer 8 bit computer with a parallel port. I wanted to find a way to make it talk to a USB flash device.

Here's an example of the many such cables to be found on the net https://www.lindy.com.au/usb-to-parallel-converter-cable-2764


texts: I am trying to control the speed of a DC motor by using H-Bridge and Arduino UNO. The initial supply is 110 AC which with the help of transformer and a full wave rectifier circuit is converted into 12V DC supply. This 12V is given to the H-Bridge. Now with the help of Buck Converter, the 12V is stepped down to 5V. Now my question is that this 5V, should I use the 5V pin or the Vin pin in Arduino?


texts: Would a SIGNAL - GND - SIGNAL - 3.3v PCB stack okay?

texts:
The Typical 4 layer PCB stack up would be

Primary Signal
GND
Vcc
Secondary signal

And i have always used this on my 4 layer projects. On this current project however the Back side of the PCB is visible so i that it would be slightly more neat to look at (especially the texts wont have a slight wave to them) if i placed the secondary signal on layer 3 and Vcc on layer 4. There are no components on layer 4 and other traces as well so it is a solid unbroken plane.
So the stack up would now be

Primary Signal
GND
Secondary Signal
Vcc

All the signal types in my circuit are digital, and the protocols that will pass on the secondary layer are SPI and some LED signals
Would this stackup be okay?


texts: Frequency that quartz crystal can handle

texts: I understand that when an applied voltage signal enters the quartz crystal, it mechanically vibrates. Now, let's say that the voltage is 1 kHz and the quartz crystal is 32.728 kHz, can the quartz crystal handle that? Does it also follow that the frequency of the applied should not surpass that of the quartz crystal? Thanks.


texts: Streaming video from Beaglebone over Xbee module

texts:
I would like to stream a video feed from a camera connected to a Beaglebone Black wirelessly. However, we are talkig distances of over 4Km so I don't think a regular 2.4GHz connection would cut it. I have seen that there are Xbee modules available with an operating frequency of around 900MHz, which would be much more suited for the considered distances.
I have seen people connecting the Xbee to microcontrollers using UART, so I would like to know if using that method the Beaglebone would be able to recognize the Xbee as a "network adapter" and stream video to it, or if I have to use other method.


texts: 2 UART Connections to MCU using the Same RXD and TXD Lines

texts:
I need to connect a GNSS module's RXD and TXD lines to my MCU.  But the problem is I don't have any available UART connections on my MCU.  There are 3 UART connections, one is used by flash, one is used for firmware uploads, and the last is connected to a LTE module.
Because I seldom update the firmware, this UART connection is somewhat wasted and I'd like to use it to connect to a GNSS module.  Is there a way that I could use an array of transistors to only connect the RXD/TXD lines to firmware upload circuit when it is needed?  Like when Vdd is detected at the micro-usb port of the MCU.  The rest of the time the UART lines would be connected to the GNSS module.
Note that unless we are performing a firmware update, a battery is being used so any excessive power consumption is detrimental to the overall design.  Below is the circuit used to upload firmware to the ESP through micro-USB which is then bridged to UART connection.


texts: On-the-fly routing of digital and analog signals using unbuffered analog crosspoint arrays?

texts:
The issue I have is strongly related to a question which was asked over here. Unfortunately I did not find the answer I was looking for. Digging a bit more I've came across a class of IC's named unbuffered analog crosspoint arrays.

What I would like to know is if an unbuffered analog crosspoint array IC would allow for:

bidirectional data flow Xn to Yn
analog signal passthrough with virtually no noise injection up to, let's say, 12-bit resolution
digital signal passthrough compatible with I2C & SPI & UART

The one IC that I came across is ADG2128 but I'm not sure if it fits the criterias listed above.

I'm well aware that the problem might be solvable via a PLD (be it FPGA or CPLD), but I have no experience whatsoever hardware or firmware (VHDL) wise when it comes to such devices. Implementing an I2C slave altogether with a biderectional crosspoint array is no easy task for a beginner. Thus, a ready-to-go, already made IC would be a good kick-start.


texts:
I am struggling with solving this circuit.
The current of drain is 1mA, and input impedance is 500k. and we should determine the value of R1 and R2.
I don't know how to write its KVL using input Impedance. could you solve this as an example?


texts:
I'm a mechanical engineer and a high school teacher that is about to start mechatronics and electronics.
I've built this simple circuit that has the purpose to switching on and off a 12 V / 25 W lamp by means of a MOSFET and an optocoupler:

All works fine, but after a few minutes the temperature of the MOSFET rises to over 90 °C.
Recently I've added a heat sink to the MOSFET, but with poor results.
On the IRF730's datasheet I can read that it can handle more than 7 A. Why is the temperature rise so hard?


texts: Quick jump from component in Schematic to Layout in Eagle

texts:
I always used the German software Target3001 to design my electronic boards, but recently switched to Eagle. There is one feature from Target3001 that seems to be missing in Eagle. I'm using version EAGLE 8.1.0 Premium.

1. The feature in Target3001

When I clicked on a component in the Schematic view, next switch to the Layout view, the corresponding component would be highlighted.

Just imagine how useful this is. I click in my schematic on IC7, then I switch to the layout view. First thing I see is IC7 highlighted there! In just two mouseclicks I find it back :-)

2. How I try doing it in Eagle

In Eagle this is more time-consuming. First I need to look at the name of the component in the schematic view, eg. IC7. Next I switch to Layout view, then click Ctrl+F and type IC7. Then it gets highlighted.

Note: I have assigned to keyboard combination Ctrl+F to run find.ulp. If I wouldn't have done that, the procedure would be even more inefficient.

Please help me to do it more efficiently.

3. The 'eye-button' doesn't work..

Some people advised me to click on the 'eye-button', then click on the component in schematic view and finally switch to layout view. The corresponding component in layout view should get highlighted. Unfortunately, this doesn't happen in EAGLE 8.1.0 Premium.


texts: Will a parallel capacitor short a resistor?

texts:
In the configuration above, SOL_IN is the rectified output of a solar panel (so dc).
What's more important is R1, which is a low resistance sense resistor used to measure the current from the solar panel. I'm concerned that the capacitor will charge to the voltage at SOL_IN and hence short circuit the resistor since there will be no voltage drop across it.
Is this reasoning correct?
(R1 = 0.15 Ohms, C1 = 1 uF)
EDIT: Line is going to load, not GPIO as originally stated.


texts: How to reduce the clock jitter for an ADC?

texts:
I am building a SDR (Software defined radio) and I am trying to clock my 16 bit 130 MS/s ADC. At this speed, the jitter of the clock is very important and a bad jitter can reduce the SNR of my ADC a lot. For instance clocking with a standard Xtal which does not have excellent phase noise characteristics induces a jitter into the clock that adds so much noise in the ADC that its effective SNR is not better that a 14 bit ADC!
The only way to have access to the full range of the ADC is the have a jitter on the clock of around 80 fs. (according to the chosen ADC chip that adds 70fs by itself)

Of course I could buy an OCXO which has an excellent phase noise, but I cannot afford to spend 300$ for an oscillator. Especially if the board could have multiple ADC...

I have read some app notes that explain the usage of PLL to remove the phase noise from a clock. Ok, but then it's the VCO of the PLL that needs to be expensive as far as I understand. And the PLL chip adds phase noise also. Even with a perfect VCO, the jitter induced by the output driver of the PLL is around 100 fs. Thus it doesn't seem to be the solution.

Thus my question is multiple :

How to clean up the clock from a reasonably good oscillator? I thought about using discreet filters, but the phase noise energy that creates the jitter is very close to the oscillator nominal frequency. I would have to use a band pass filter with a bandwidth of ~10khz at 130Mhz! Is it possible to do ? (bellow 200$ otherwise it would be cheaper to buy the OCXO)
If there is no way to achieve this level of jitter of ~80fs (phase noise from 10Hz to 260MHz) by myself, where can I buy oscillators that have this level of performances with reasonable cost?
The problem is that OCXO are extremely stable over time ( years ) and are usually used for that. But here I don't care, it's the phase noise that is relevant to me. Is there oscillators technologies that are very clean, but that drift over years?
How you, amateur radio guy who have a SDR system, or engineers that design high speed ADC, solved the problem?

As you can see, I have spent a LOT of time reading app notes on the subject on the web, thus I have a deep understanding on how it works. I am a bit pessimistic about this and start to believe that there is no way to obtain a low jitter clock without getting a ~100$+ OCXO...


texts: Impedance matching of a transformer and reflected impedance

texts:
Transformers are used to raise or lower the apparent impedance in
  order to achieve maximum power transfer.

Above quote is from a tutorial I encountered with the following example circuit:

For the above circuit, what can we say about the transformer turns ratio or reflected impedance to obtain maximum power transfer? Do we need to know the frequency? What should be the way of thinking?


texts: Can I just T into a CAN bus network if I just want to observe the data?

texts:
Can I just T into a CAN bus network if I simply want to snoop on the data flowing?

I know I have to disable ACK bit sending, but is it just a case of physically splicing into CAN-High and CAN-Low?


texts:
I have a  15V, 150W Quartz Tungsten Halogen  and would like to make it work. So far I have found that it is driven using AC, so I believe I need an AC/AC step down transformer (if 220VAC is used)? If so, do I buy a specific one or do I make one myself? Though, I am not entirely sure if it is the correct approach.

Any relevant information is appreciated.


texts: How about this design of analog comparator?

texts:
These day I design some transistor logic circuit for the high voltage sensing.
I complete other necessary logic gate but, I didn't decide comparator circuit yet.
Are there any improvements to this circuit? I need your opinion.

And if you want see how this circuit working, follow this link.
http://www.falstad.com/circuit/circuitjs.html?ctz=CQAgjCAMB0l3BWcAmWDLMgZgBxmcgCxg4CcSA7KSEoVgFAAuIyOO4AbJCFpp99wC0EQTEIUMkCmVJhC2NshCjoCCtLI5MYXqVLSacegHcefHN17c5hKE3D4WCDvycvrysLEgdCpLTjqFMgUHGpQqugcOAhgYKRwXJA4WOBGzMjObizJ2R6CqGxqCPpYWMEkYUowWCS8YJBqFlx+WC4NkPQATq5goa4WUGnw3TnsfS6Y7IPW8J2mYFwgg1PLAvQASmNr27xD3PI0+xEIJr39i9yr89sT20TrC0shSpcsbHZPVx+rrOw3v2C9w+nR6vx+uTK7mGRgA5rs2rsENU7H1Xo4-g4lFYhhQWNAsEgkAITiAAGoAewANowAIawgCm9DR2UxmRcOO4eNQEGJ+1U5OpdMZoziSnZWPe-xhoNZWQlmNmIwyQLumLuHjEyCwdHQDXIzUWEXEel4dGQ8X8+mGo1WatV-SVIy+t2ehxub1+RG2soItnB7GuMoBH3i4oh-zOq0GOJm9HhOJeZm+0tlOLuiaBTpu6f6xHajvoAA9lkhCejUoTaCxbGSwMWWEtCalMYSXP7a8gG2VbItbIRvYs8R3yWAADoAZwAfJOyV2Ke8QL4hvI9EcYHN9GEOJkhuGePQgA


texts: Connecting a 5 V signal to a 3 V tolerant pin of a PIC

texts:
I have a situation that happened in my case, where i'm putting an AC signal that goes from 0 to about 4,5 V in a 3 V tolerant pin of a PIC.

The pin in question is RE6 of a PIC32MX470F512L.

From the datasheet we see that this pin has a white color while the 5V pin tolerant have a gray color:

The signal is a square wave that goes from 0 to about 4.2V.

My question is, what happens to that input pin of the pic? Does it get damaged?


texts: The Component/Parts placement in PCB for future serviceability

texts:
Is there a specification or "Best Practices" in the PCB design regarding the dimension between Components?
What I need is to minimize the whole PCB board BUT with enough spacing between components (for the installation/replacement of the components, or any activities that will needs soldering/de-soldering)

Note:  I'm looking for an advice for the "manually" placing/soldering


texts:
I have programmable current source in the board.  The circuit blocks in the board is,

Microcontroller => DAC => Amplifier => Output port

I want to measure the current for range of DAC code to verify the circuit is functioning correctly. Its 16 bit DAC. So, i would like to measure current for DAC code 0x0000, 0x1000, 0x2000....0xFFFF. According to schematics the circuit can source up to 100mA.

How to use the multimeter to measure the current at a pin in output port.Should i have to connect load/resistor in series to multimeter?

Output Pin <=> Multimeter <=> Resistor <=> Ground(mounting hole in the board/power ground)

Any help is appreciated.
Thanks


texts: KiCAD: Connections are not the same in schematic and pcbNew

texts:
This is a portion of my schematic:

Now, I try to create the traces in pcbNew.
Here is the portion of pcbNew:

In the schematic:

C4 is connected to pin 1 of U1 and to pin 2 of U1
C1 is connected to pin 5 of U1 and to pin 5 of U2

In pcbNew:

C4 pin 1 is connected to pin 5 of U1  pin 2 is connected to pin 2 of U1
C1 pin 1 is NOT connected, pin 2 is connected to pin 5 of U2

As you can see, pin 1 of both C1 and C4 are not the same in schematic, and pcbNew.
In the first iteration of my PCB (first PCB ever), I trusted the ratsnest, which I failed.
What is the process to create proper traces in pcbNew?
If you want, I can upload the schematic and PCB files.


texts:
Hi I'm currently attempting to write a simple program using the STM32 Nucleo development board, based around the STM32F334R8. The application sets up the GPIO ports A and C and reads the state of the button. If the button is pressed, it turns on the LED. If not, it turns it off.

From ST's documentation (STM Nucleo 64) I've verified that the button is wired to Pin C13 and LED2 is wired to Pin A5.

From the datasheet, I've been reading through the registers for the GPIO (Long STM32F334 Datasheet) and see there are three that seem to be related to the output; ODR, BSRR, and BRR.

When implementing the application mentioned above, my first thought was to write the GPIO pin state for the output LED using ODR, like so:

SET_BIT(GPIOA->ODR, GPIO_ODR_5);
CLEAR_BIT(GPIOA->ODR, GPIO_ODR_5);

This did not appear to work. My button presses were detected, as I could verify this in the debugger by seeing it follow different paths. Here's my setup code for the GPIO:

// set one to input
CLEAR_BIT(GPIOC->MODER, GPIO_MODER_MODER13_0);
CLEAR_BIT(GPIOC->MODER, GPIO_MODER_MODER13_1);
// set another to output
SET_BIT(GPIOA->MODER, GPIO_MODER_MODER5_0);
CLEAR_BIT(GPIOA->MODER, GPIO_MODER_MODER5_1);
// set output to push-pull
CLEAR_BIT(GPIOA->OTYPER, GPIO_OTYPER_OT_5);
// set input with pull-up
SET_BIT(GPIOC->PUPDR, GPIO_PUPDR_PUPDR13_1);
CLEAR_BIT(GPIOC->PUPDR, GPIO_PUPDR_PUPDR13_0);

// enable GPIOA and GPIOC clock
SET_BIT(RCC->AHBENR, RCC_AHBENR_GPIOAEN);
SET_BIT(RCC->AHBENR, RCC_AHBENR_GPIOCEN);

I also saw a piece of example code that worked on my board that uses the BSRR and BRR bits, like so:

// set output high
SET_BIT(GPIOA->BSRR, GPIO_BSRR_BS_5);
// set output low
SET_BIT(GPIOA->BRR, GPIO_BRR_BR_5);

... But this didn't work.

I'm not sure I understand the difference between the three registers and their functions.

What are the use cases for each? Which one is suited to my application?


texts:
This is how S/PDIF to TTL converter usually looks like. I simulated poor quality smoothed out signal with a sine wave.

Can comeone explain how it really works? Inverter with feedback resistor confuses me a bit. My intuitive approach would be to use a voltage divider to bias inverter's input to it's threshold point. On the schematic above it becomes properly biased automatically.


texts: Can anyone help me how to convert 100mV AC to 1.5V DC without using any external power supplies

texts:
I am looking for a CMOS circuit that will help me to convert 100mV of AC to DC and that DC should boosted to 1.5V.
Firstly can anyone suggest me a CMOS circuit to convert 100mV of AC to DC. And DC to DC boosting is 2nd phase of my circuit.


texts: How should I properlly draw on a schematic a shunt going through the center of a toroid coil?

texts:
So I'm trying to reverse engineer the schematic for an Avair AV-200CN SWR bridge. Two toroid coils, used for sensing, are mounted on a shunt, so that the shunt goes through the center of the coils.

I'm not 100% sure how to draw such an arrangement on a schematic. Was initially thinking of drawing it as a transformer with two secondaries, since the shunt acts as a one-turn primary, but I'm not sure if there's a better way to draw it, since I'd like to minimize the amount of thinking needed to understand the schematic.

Here's the picture of the circuit:


texts: Why don't most lab power supply units display the maximum current?

texts:
I don't understand why most modern lab PSUs in constant voltage mode don't explicitly display the maximum authorized current.

You have to set the current with output ON starting from 0 A, passing by a few mA where the device state is blinking/unstable because it is missing energy, up to the maximum driven current, and blindly go a bit higher in case operation requires slightly more current at some point - while I'd like to set voltage and current with output OFF, and then power the circuit.

I really don't get why most lab PSUs don't display the maximum current that you set. It looks the bare minimum to me, just like the set voltage. I've been working with a dozen models, and only one had a "review" button letting you know the voltage and maximum current.

Am I misusing lab PSUs? Or why isn't there a maximum current indicator on all lab PSUs?


texts: STM32 skips UART frames after framing error

texts:
I am currently developing a DMX512 receiver with an STM32F767ZI. DMX512 is basically a protocol transmitting a byte array via RS485. In summary it works like this:

> 92us low signal (called break)
> 8 us high signal (called mark after break / mab)
bytes transmitted one after another with 2 stop bits

To correctly identify the beginning of the array, usually the framing error functionality of USARTs: the break signal will be seen as a framing error (missing stop bits) and then the USART starts reading bytes after the MAB.

Given this basic blueprint, I created the following interrupt handler.

USART_TypeDef *usart = this->USART();

usart->ICR |= USART_ICR_NCF;
usart->ICR |= USART_ICR_ORECF;

// new data
if (usart->ISR & USART_ISR_RXNE) {
  uint8_t data = (uint8_t) usart->RDR;
  this->last_data_timestamp_ = HAL_GetTick();
  if (this->first_ || this->next_byte_ >= 513)
    return;
  uint8_t *buffer_ptr = &this->buffer_[this->next_byte_++];
  if (*buffer_ptr != data)
    this->changed_ = true;
  *buffer_ptr = data;
}

// break condition
if (usart->ISR & USART_ISR_FE) {
  usart->ICR |= USART_ICR_FECF;
  if (!this->first_ && this->callback_ != nullptr && this->next_byte_ != 0) {
    this->callback_(this->parent_, this->buffer_, this->next_byte_,
                    this->changed_, this->callback_param_);
  }

  this->first_ = false;
  this->Clear();
}

However, after a break condition is successfully detected, 14 bytes will be skipped (and nothing will happen) until the first RXNE interrupt is called. Looking at the input signal, I noticed it is not quite to standard (stop bit is around 70us long instead of 8), I don't that this is the issue here, since it correctly identified as such after the first 14 frames. Afterwards everything executes as expected.

Further investigation has also shown, that right before data is received correctly again, the ORE bit will be set.

I have also tried attaching an oscilloscope to the input and to another pin of the STM which is toggled whenever an RXNE interrupt is called. The result looks like this:

The USART is provided with a 16MHz clock signal and its BRR register is set to 64 so that the baud rate is (with OVER8=0) - as required - 250000 kBaud/s

What could be the reason for this? Is the USART unable to identify that data transmission has started again? Why so then or how can I fix that?

EDIT: I have now also had a look at IDLE changes. Using the same method as for the RXNE interrupts, i have gotten these results:

So appareantly the USART is not able to detect a start bit in any of the previous bytes. How so? How do they differ from the 15th byte?


texts:
I am designing a board that has an LCD and msp430fr2433. They both need 5v and 3.3v respectively. So I decided to use TPS560430X3FDBVR and TLV70033DSET to provide 5v and 3.3v. I have attached the schematic and traced the path with a yellow highlighter. I hope this makes it easy to follow.
I followed the circuit recommended by the datasheets of the regulators except for Cboot which is 1uF on the board. Is anything wrong with my schematic?
Problem: I connected the board to a 12V DC power supply. It's pulling 3A. Seems like there is a short but nothing is burning. Not sure why there is a 3A draw when the 5V regulator output current is 0.6A max.
I didn't find any short but the 3.3V regulator and micro pads are underneath the component. I can't see if there's a short.
Analysis: If there is nothing wrong with my schematic, I plan on concluding that there is a short. I just want to get a second opinion about the schematic.
Datasheets:
5v regulator https://www.ti.com/lit/ds/symlink/tps560430.pdf?HQS=TI-null-null-digikeymode-df-pf-null-wwe&ts=1606594508057
3.3v regulator https://www.ti.com/lit/ds/symlink/tlv700.pdf?HQS=TI-null-null-digikeymode-df-pf-null-wwe&ts=1606600030251


texts: Should I use a gate resistor for FQP30N06L if my gate is connected to GPIO 3.3 volt of a Raspberry Pi?

texts:
Do I really need a gate resistor for FQP30N06L if I have connected my gate to a GPIO 0-3.3 volt of a Raspberry Pi and the GPIO is going to PWM about 100-300 Hz.
It feels like if I put a resistor between GPIO and gate, then the resistor is going to create a damping effect. Right? The higher frequency I have, the less voltage is going to attach to the gate pin of the FQP30N06L?
The threshold voltage is between 1.0 to 2.5V for the FQP30N06L.
I'm not talking about connecting a resistor between gate and GND.
https://cdn.sparkfun.com/datasheets/Components/General/FQP30N06L.pdf


texts: Minimum Output Operating Voltage of Solid State Relay

texts:
I'm wondering if someone could explain why a solid state relay has a minimum voltage that it can switch on or off.  For example I'm hoping to use an SSR-10DD (http://www.fotek.com.hk/solid/SSR-3.htm) solid state relay, however the spec sheet mentions a minimum of 5V on the output side.  I was hoping to use it to switch around 3V.  Why would it require a minimum of 5V?

Update:

V_input range = 5V from an Arduino output pin
I_Output current range = Signal only, so less than 10ma
Target load type = Signal
Reason for isolation = want to avoid all possibility of damaging existing circuit

More details about what I'm trying to achive can be found in this question: Connect Arduino to existing circuit with seperate power supply


texts: Which is slow among the two? Latches or Flip-Flops?

texts: I have a question regarding latches and flip-flops. Which of them, is faster? Please explain me this with a suitable reason.


texts: PIC12F509 Switch Debouncing On Press Release Or Both?

texts:
I have a question regarding switch debouncing I'm using a PIC12F509 and the internal RC oscillator operating at 4 MHz.

I'm toggling an LED on and off connected to GP1 (output) via a momentary push button switch on GP3 (input) which is held high via a 10K resistor when the switch is open. I'm using the following macro and the code below to debounce the push button switch. It utilizes timer 0 set to a 1:256 prescale.

It waits until the contacts have remained in the same state (open in this case) for 10 milliseconds before executing the rest of the code. If they bounce (go low) timer 0 gets reset.

DbnceHi     MACRO    port,pin
local       start,wait,DEBOUNCE
variable    DEBOUNCE=.10*.1000/.256 ; debounce count = 10ms/(256us/tick)

    pagesel    $ ; select current page for gotos
    start      clrf TMR0 ; button down, so reset timer (counts "up" time)
    wait       btfss port,pin ; wait for switch to go high (=1)
    goto       start
    movf       TMR0,w ; has switch has been up continuously for
    xorlw      DEBOUNCE ; debounce time?
    btfss      STATUS,Z ; if not, keep checking that it is still up
    goto       wait

    ENDM

main_loop
; wait for button press

wait_dn   btfsc GPIO,3 ; wait until button low
goto      wait_dn

; toggle LED
movf      sGPIO,w
xorlw     b'000010' ; toggle shadow register
movwf     sGPIO
movwf     GPIO ; write to port

; wait for button release
DbnceHi     GPIO,3 ; wait until button high (debounced)

; repeat forever
goto     main_loop

END

Now onto my question up until now I've been debouncing both the button press and release. It's been brought to my attention in the tutorial I'm following that it's not normally necessary to debounce both the press and release of a switch.

I can understand why in theory because after the switch is read as low via the btfsc instruction (even if it's momentarily because the contacts are bouncing). The LED is toggled and the debounce high code will wait until the contacts have opened and stopped bouncing before executing the goto to loop the code from the beginning.

On the positive side this saves program memory. But if something seems too good to be true it usually is what are the potential pitfalls using this method?

Obviously for a simple application like this the code is overkill. But for something more critical like putting the PIC in sleep mode and waking up from a pin change any bounce must be eliminated in order for the micro to enter the leave sleep mode reliably.

What are your opinions on switch debouncing do you debounce the press and release or only one?

My guts telling me to go belt and suspenders and just debounce both to be safe but I have no logical reason for it.


texts: Skin depth calculation for non-sinusoidal currents

texts:
I have some questions regarding the skin depth of wires.
In this forum it was already asked how the skin depth can be determined for a square voltage (e.g. inductor voltage of buck-converters) (link: square wave skin depth). Unfortunately, the question could not be answered. I have an approach and would like to know if it is correct in your opinion.

In general, the skin depth is defined with

$$\delta = \sqrt\frac{\rho_{w}}{\pi\mu_{0}\mu_{R}f}$$

with \$\rho_{w}\$ as the resistivity of the conductor (\$1.72 \cdot 10^{-8}\$ \$\Omega m\$ for copper at room temperature). \$f\$ is the frequency of a sinusoidal current in the winding in \$Hz\$, \$\mu_{0}\$
is the permeability of free space (\$4\pi\cdot10^{-7}\$ \$\frac{H}{m}\$) and \$\mu_{R}\$ is the relative magnetic permeability of the conductor ( for copper it is approx. 1). Now, the only problem in this equation for an inductor of a buck converter is the frequency \$f\$.  For non-sinusoidal currents and combinations of dc and ac current, this equation can be used if the frequency is replaced by the effective frequency (see http://power.thayer.dartmouth.edu/papers/pesc1997a.pdf Appendix C). The effective frequency of a triangular current waveform can be calculated with
$$f_{eff} = \frac{rms(\frac{di_{L}(t)}{dt})}{2\pi\cdot I_{L,RMS}}$$
with \$i_{L}(t)\$ as the inductor current in \$A\$ and \$I_{L,RMS}\$ as the RMS inductor current in \$A\$.
Fortunately, the inductor current is
$$di_{L} = \frac{V_{L}(t)}{L} \cdot dt$$
with \$U_{L}\$ as the inductor voltage in \$V\$ and \$L\$ as conductivity in \$H\$. With this we get
$$f_{eff} = \frac{rms(V_{L}(t))}{2\pi\cdot I_{L,RMS}\cdot L}$$
If we take the buck converter as an example, we get
$$f_{eff} = \frac{(V_{i}-V_{o})\sqrt{D}+V_o\sqrt{(1-D)}}{2\pi\cdot I_{L,RMS}\cdot L}$$
It can be seen that the effective frequency does not depend on the switching frequency and that the maximum results at a duty cycle of 0.5 and maximum output voltage. The minimum effective frequency results at a Example: \$V_{o} = 250\$ \$V\$, \$V_{i} = 500\$ \$V\$, \$L=200\$ \$\mu H\$, \$I_{L,RMS}=113\$ \$A\$, \$D = 0.5\$. For the effective frequency we get
$$f_{eff} = \frac{(500 - 250)\sqrt{0.5}+ 250 \sqrt{0.5}}{2\pi\cdot 113\cdot 0.0002} = 2490Hz$$
Finnaly, the minimum skin depth is
$$\delta = \sqrt\frac{1.72 \cdot 10^{-8}}{\pi\cdot4\pi\cdot10^{-7}\cdot 2490}=1.33mm$$
My questions: Is my approach to calculate skin depth for the indcutor wire in DC-DC converters correct? If it is: Why is the skin depth not depending on my switching frequency?


texts:
What techniques are there for placing the components on a PCB at a desired height? e.g. so that potentiometers and switches can be both panel mounted and board mounted?
For example, are there adapter components designed to lift other components away from the plane of the board?
Reading the answers here I'd guess that nobody has invented such a thing yet, and that instead PCB designers have just had to come up with ways around the problem such as wired connections, actuator extensions, etc.


texts: Sharing ground between devices connected to same power supply

texts:
Several Raspberry Pi projects I've seen, using two modules, have a jumper wire between both GND pins, when a physical connection between one or more pins is needed between both modules.

What is the reasoning behind this? If both modules are connected to the same power supply, don't they already share the same ground?

In general, when should you share the ground? Is this a matter of cable length, distance between components, etc?


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I have Altium 20.0.11.

My rules keep getting deleted when I update from the schematic.
Any rule I set in the PCB gets removed when I perform an update from the schematic.
This the only project I have that does this.

There must be some setting that I am missing.

I do have Altium support but there new system sucks and it can take days (been waiting a week to get a response to another issue) so I figure this is maybe faster.


texts:
I have task that I need to make adapter board which transforms gigabit ethernet connector RJ45 to another connector (not RJ45). I also have power connector to carry power one side to other.

I need to route 100ohm differential pair without GNd I can't find any PCB calculator for parallel routing on one layer. I found this article though.

And there is calculator in Saturn PCb that calculates differential pair which I think what I need. It shows that pairs must be adjecent layers between PCB.

What is the best practice here ?


texts: How to control rise time of output of LTSpice's Voltage Controlled Switch?

texts: I have a RC delay circuit as input into a Voltage Controlled Switch in LTSpice.  It's working the way I want, except I can't figure out how to shorten the rise time of the signal that emerges from the switch once it's triggered on.  This is the "swout" signal in the below schema and it's also shown graphically.  The 10-90% rise time for it is measured as 1.1 microseconds.  Is there a way to get it much lower, on the order of a few nanoseconds?


texts: Is it possible to output voltages in the range of kilovolts and current of atleast >1mA using an input of <10V on a consumer electronics op amp such as IC 741? If not, then why?


texts:
I bought this motor at a scrap yard and would like to wire it up for 120 volt power.

There are 5 wires coming from the motor, a black, white, ground and two yellows. One yellow is numberer "2" and the other is "8".

Inside the motors the terminals seem to be numbered from 1 to 5 with each having two spade connectors except number 5. The black wire is connected to number one and the white wire connects to number 2. A yellow and a purple wire are attached to number 4 and number three and five are empty.

I'm not familiar enough with wiring diagrams on Motors 2 figure out how it relates to the wires I'm seeing in the motor, and searching online didn't bring up any additional information for this particular motor.

Any guidance would be greatly appreciated.


texts: Why is a resistor needed in zener protection circuit?

texts:
I have decided to add zener overvoltage protection to the I2C lines of my device. After some searching I have found that the most used circuit is:

So my question is why do we need R3 and R4? If they are for limiting zener current why are not they connected as:

I have picked SDA and SCL but I think the same is for all other I/O.


texts: Is it normal to have this long fall time with a MOSFET and a LED strip at 100Hz?

texts:
I'm using the following schematic to drive a LED strip (15 LED) with a MOSFET from an arduino PWM :

simulate this circuit – Schematic created using CircuitLab

But when I check the tension at the LED strip (between NODE1 and NODE2) with a 100Hz PWM, I have the following signal :

Do you know what would cause this long fall time ? I've checked the input PWM, the square signal is ok. Is it for the same reason as in this question (ie. the scope probe) : MOSFET fall time too slow ?


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Sometimes I need to take my laptop places and, it doesn't have the greatest battery life, sometimes maybe it only lasts 10 minutes.

So after researching a bit I decided I wanted to build a li-ion S3P5 battery pack like this:

with an added on inverter for ac power. I was planning on using this BMS, I was wondering if I could charge it with an MCP73831 based battery charger (Yes, I do know that it is meant for single cell charging but i'm curious) since the BMS would take care of the balancing.


texts: negative voltage current limit circuit to control LDO enable

texts:
I am looking at the best method to control an LDO enable pin using a negative voltage current limit circuit. The LDO is disabled when the enable pin is 0 to 0.4V. The LDO is enabled when the enable pin is 2 to 10V (max).

The current limit circuit that i am using is below. R3 models the load. Under normal condition the load current is 0.2mA or less. Under fault conditions the load current is 2mA.

The basic idea is that the LDO is disabled (LDO enable pin 0 to 0.4V) when the load current reaches 2mA. Under 2mA the LDO is enabled (LDO enable pin 2 to 10V (max)).

Apart from the -32V input there is also 3.3V.

Look forward to your replies.

Regards Joe


texts: How can I tell what amperage a 12V rated electrical device will run at 5V?

texts:
I am buying a TEC 12706, a thermoelectric Peltier.

It's rating is: 15.4V 6A (maximum voltage and amperage). I want to run this Peltier at 5V and was wondering how I would convert this data to see what amperage the cooler would draw at 5V.

The only reason I ask this is because before I used ratios to convert (15.4/6 = 12/X) and it didn't work out. For example, I bought a Peltier rated at 6V 2A and it ran at 5V 2.2A and I bought a Peltier rated at 12V 5A that ran at 5V 1.3A. Clearly I am converting somewhere wrong, so any help is appreciated.