texts:
When I was a teen, I joined an electronics club and built a disco board.  I had 5 light bulbs, I painted them different colors.  Then I built a board which was connected to these light bulbs.  I'd connect my stereo to the board and the each light bulb would flash when a specific instrument would play (e.g. green for drums, etc...).

I want to build something similar with my son now, but I totally and utterly forgot how to do this.  Can someone point me in the right direction?


texts: How can I use 2 Tp4056 as protection circuit for diy 2s li ion battery?

texts:
Hi I want to use 2 Tp4056 modules as over-discharge protection circuit for my DIY 2s li ion battery pack.
Those will not be used for charging! hence will not share input! The load is an arduino nano that is going to control a small dc motor and a servo!

Is it a viable option or should I use some other method for the same.


texts: How to calculate input and output impedance of voltage follower operational amplifier?

texts:
While performing simple practical with LM741 IC in voltage follower mode. Connections as shown in the figure below.
I looked online for the input and output impedance calculation and all I got is the calculations for inverting and non-inverting or emitter follower configuration methods.
I am bit stuck here while calculating input and output impedance in buffer or voltage follower configuration.


texts: How to set ATmega88PA fuses in code or HEX file

texts: I'm a Microchip guy, but I'm helping a customer out with an Atmel project using the ATmega88PA project they inherited from another division. I'm using AVR Studio 5 and I would like to compile the fuse selections into the source code and eventually hex file. How do I do this?


texts: Have anyone tried to use massage electrodes for eeg? I believe as they conduct high charges probably using inexpensive metals they are not suitable for measuring tiny voltage changes but I'm not sure.


texts:
After reading the answers of two questions regarding the LM317, the answers made me think about whether I realy understand current source and current limiter.

In this answer it says:

  The LM317 with the single series resistor between output and adjust input is actually a fixed current source, not a current limiter.

In another answer the LM317 is used as a "Precision Current Limiter". It is taken from the datasheet, so the wording should be right(?)

Now when I compare the "Precision Current Limiter" on page 17 and the "1A Current Regulator" on page 16, both have a "single series resistor between output and adjust input". What is the difference here?

From a user perspective my understanding up til now was:

Current limiter: does never supply more current then the limit, but can provide less.
Constant current source: the current sourced(/sinked) stays always the same (at least the regulator tries to do so)

Is my understanding right?


texts: Dosage control through flow meter and valve

texts:
I am trying to make a drinks machine that when a button is pressed, a predetermined amount of liquid (not determined by time) is allowed through a solenoid or other valve, and measured by a flow meter. Ideally the flow meter could be digitally linked but not essential.

I have been trawling the internet for days but I can't seem to find anything that determines by quantity of liquid, and not time dispensed. I would be enormously grateful for any suggestions.


texts: What is meant by average power in AC circuits?

texts:
I read that "The average power is the power averaged over a cycle or number of cycles."

I know that the average value of power for both active and reactive power is a constant number.

Buy I am confused that whether the cycle here means the complete cycles or cycles?

If power is averageed not "over a cycle or number of cycles" but supposes it is averaged over a quatter of cycle or two third of a cycle, will we get the same exact constant for the average power which we get for the average power over a complete cycle or cycles?


texts: Altium 18 multi-board design. How to connect 2 PCB's with a pin header?

texts:
I am trying to use Altium's multi-board design tool to connect 2 PCB's.

The PCB's will be connected with a right angle, male-male pin header (shown in image below).

Bottom PCB: Motherboard                   Top PCB: Daughterboard

My project structure looks like this:

Project.PrjMbd

Source Documents

Project.MbsDoc
Project.MbaDoc

Daughterboard.PrjPCB

Source Documents

Daughterboard.SchDoc
Daughterboard.PcbDoc

Motherboard.PrjPCB

Source Documents

Motherboard.SchDoc
Motherboard.PcbDoc

I intend to join the two boards using only one pin header. The trouble is that both boards need to have the header library component so that the correct pads and nets are connected.

Does Altium have a mechanism for doing this?

EDIT: I do have the System:Connector parameter added to the header library component.


texts: Antenna microstrip feedline discrepancy?

texts:
I've been looking at some reference designs to guide my own design recently, and I noticed some possible discrepancies on one in particular.

This is the reference design:

http://www.ti.com/lit/ug/tidubq7a/tidubq7a.pdf (description)

http://www.ti.com/tool/TIDA-00848?keyMatch=cc1310&tisearch=tidesigns (page and design files)

In section 9.3 it states the feed line was modified to be 50-ohms with the 1mm thick PCB. The design files show a microstrip line width of 24 mils and a spacing of 6 mils from the ground plane on each side. However, doing the maths on these figures as a co-planar waveguide (with Saturn PCB toolkit) the impedance actually comes out more like 56-Ohms.

Is this correct? And if so, is it just a case of the feed line being so short they don't mind it's a bit mismatched?

If it's not correct, how was it calculated? By my calculations the feed line would have to be about 33 mils wide to have the correct impedance.


texts:
I want to create a project that will read playing cards that have integrated RFID. If I put multiple cards  on top of each other will it still be able to determine the stacked cards?
what if the cards are not perfectly stacked on each other? Like for example layed on top of each other but pushed down a little where only the letter appears?
Thanks.


texts:
I'm trying to figure out with E-flite 7.6g Sub-Micro Digital Tail Servo JST my particular one has 1.0mm to male JR connector, so need to be connected with some switch, I have 2 other servos here, which wires layout is (-)(+)(S), but this E-flite servo turns GND wire to the center, not like on on the picture by link from above, which also has usual connector.  Particular device look like this:

For example if I have some limit for server, E-Flite makes unexpected 360 turns against command value, which operates is in limited  0-160 degree  range. if I move  E-Flite fast, start behave this way. I'm not sure how to limit such servo in certain range in case if it must be inside some passable where such freedom will go against physical limit for example

I have cut off this connector, to change it on usual size, it is different, wires from servo comes out same way as usually (-)(+)(S) but connector changes layout to (+)(-)(S), same way as this adapter, I return it to the original layout (-)(+)(S) pin (9), but  I can't turn this servo same way as other servos with using of Arduino Uno, loaded code and C# from desktop control

The motor behaved strangely, this unexpected movement  occurs without any command from loaded code or control application:

Makes very slow sequence of gear steps  about 30 degree range, then stops
Makes one fast movement 0 to 360 and back to 0
Makes sequence of fast movement 0 to 360 and back to 0
Sometimes does not reacts to command from application
Sometimes stops to move until restart the controller
Produces buzzing noise without moving

For example if I want some limit for servos, E-Flite makes unexpected 360 turns against command value, which operates in limited  0-160 degree  range. if I move  E-Flite fast with short movement , unexpectedly motor can make turn 360 degree 3 times, then continuous move by commands. I'm not sure how to limit such servo in certain range, in case if I want locate it inside assembly, where this freedom will go against physical limit

I don't know if behavior of servo comes from the fact that I've cut the wires and put usual size plug without using of adapter like this one E-Flite EFLRA100 Jst-zhr 1.5mm to Universal Adapter

Here is a code, which works without problem with two other regular servos (except some noise):

I'm using Adruino Uno and Due to control 2 servos from C# desktop application, this way:

myport.WriteLine("9");
myport.WriteLine(trackBar1.Value.ToString());

and loaded code:

#include <Servo.h>
Servo servo1;
Servo servo2;
int val;

void setup() {
    Serial.begin(9600);
    servo1.attach(9);
    servo2.attach(11);
}

void loop() {
  val = Serial.parseInt();
  if(val == 9){
    servo1.write(Serial.parseInt());
  }
  else if(val == 11){
    servo2.write(Serial.parseInt());
  }
}

Any advice, guide or example would be helpful


texts:
If I need to wrap an existing, previously top-level VHDL design for an FPGA with INOUT ports in another new top-level entity...  what's the proper way to pass through PART of an INOUT port?

Usually, I'd just remove the INOUT from the non-top layer and replace it with directional ports...  but my client wants to keep that code entirely unchanged (so the HDL supports two different board designs).

Say entity old_top_level has a port SPARE_IO : INOUT std_logic_vector(7 downto 0).  Another entity new_top_level has SPARE_IO_WRAPPED : INOUT std_logic_vector(7 downto 0).

I need to redirect a single element of SPARE_IO.

Will the following work (defined in the body of new_top_level):

SPARE_IO_WRAPPED(6 downto 0) <= SPARE_IO(6 downto 0);
SPARE_IO(6 downto 0) <= SPARE_IO_WRAPPED(6 downto 0);
SPARE_IO(7) <= SOMETHING_ELSE;

It seems to compile, but that's not saying much.

EDIT I edited to clarify the INOUT signal isn't completely passed through so I can't just use the PORT MAP.


texts: How to read a treadmill ear clip pulse sensor

texts:
There are many inexpensive ear clip pulse sensors such as this one available with a standard 1/8" audio jack.  I would like to know how to read this sensor with a microcontroller and calculate heart rate.

I found a Grove kit for an ear clip sensor but I don't see the design files for it anywhere (The link on the wiki for Eagle files only contains an Arduino sketch).

Does anyone know where I can find a pinout for this sensor or an example amplifier circuit?


texts: Choosing an appropriate constant current LED driver

texts:
I am trying to replace a (suspected) constant current LED driver in a plant lamp as it has a terrible plastics smell. I am searching for a more high quality driver. I do not know then forward voltage of the LEDs, and at the moment I do not have a multimeter at hand (I will next week).
Driver to be replaced:

So far I have understood, that I will have to pick a constant current LED driver, which supplies 650mA and which voltage range convers at minimum the entire range of the current driver.
I have found the Mean Well HLG-60H-C700A, which supplies 420 ~ 700mA (adjustable via inbuilt potentiometer) and 50 ~ 100V, which should cover the needed voltage range.
The current driver is dimmable, but I do not really need that functionality. I am fine with setting the driver to some output current, and then leave it there.
I have the following questions:

Will the Mean Well driver be able to replace the current driver (as its max voltage is significantly higher than the current drivers)
Can I adjust the output current to, say, 500mA and by that drive the LEDs at a lower brightness? Will this cause the driver to output significant heat (I could not find out if it is linear).
Assuming I wanted to add dimming functionality (e.g. through an ESP8266 and PWM, using the mean well B model). How would I limit the driver to 650mA? Is this what the AB model achieves?


texts: Mathmatically analizing different voltages in a phase changing circuit

texts:
I am trying to understand a phase shift oscillator from a mathematical perspective, and to begin I simply took the phase-shifting part of the circuit and am now trying to analyze the voltages as a function of time. Essentially, I'm looking for a way to find the voltages across each component. Normally, something like this would be easy to find using basic equations and grouping, but in this specific application, I can't even find a way to group the components together. Here is the circuit:

My best guess on how to solve this is to find the impedance of each capacitor as a relation to time by working left to right. But in order to find this impedance, I also need to know the current through each capacitor as a relation of time. But in order to know that I would think that I would need to know the V-Out voltage. It seems that in whichever way I try to solve this, I end up going in a loop with all the equations. Also, just for informative purposes, I plan on graphing all the voltages on Desmos.

Is there anything that I am missing? I really am stumped here and any help would be appreciated. Also, I have only taken high school physics at this point and haven't had a chance to get into the calculus bits yet, so if its at all possible to answer the question without calculus, that would be appreciated.


texts: Musical Tesla Coil / Slayer Exciter - Electrolytic Capacitor

texts:
Can somebody of you tell me, why the upper capacitance in this musical tesla coil needs to be an electrolytic capacitance?

Tesla Coil audio music player circuit analysis


texts: Arduino Cellular Shield EMC Testing for FCC

texts:
I have designed an Arduino shield that uses an FCC pre-certified and PTCRB cellular module and I'm wondering about EMC testing and FCC compliance. However, the main concern here is that I am  using a different antenna and I read that I have to use the same antenna(e) that the module used during the certification process in order to not have to completely re-certify it for FCC ($10k+ and FCC ID and all that jazz). The weird thing is that Adafruit doesn't certify any of their FONA cellular boards even though they use different antennae from the ones in the module's certification. And how could you possibly get the exact same antenna that was used in the testing anyway? There are so many antenna knock-offs that may or may not even work. Check out this post in which Adafruit explains why they don't have to test their boards. In response to a question why they don't certify their boards Adafruit replies that "Because of our FONA boards, we're officially listed as a cellphone manufacturer" which basically sounds like "because we sell cellular modules we are officially listed as a cellphone manufacturer and therefore we don't have to certify our products" and that simply doesn't make sense to me.

To summarize, my questions are these:

Is it legal to sell these shields without doing EMC testing or by only doing radiated emissions testing, or do I have to get it completely FCC certified with the new antenna?
What about selling the shield to users in other countries? For example, Adafruit sells both an American (SIM5320A) and European (SIM5320A) version of their 3G module. Specifically I'm asking about the case in which the EU module (like SIM5320E) is CE certified. I understand there are specific laws for each country within an overarching region but I also read that you have to pay each country a registration fee? So if you're selling the board all over the world, how on earth would you afford every single country's fee? I notice that Adafruit doesn't mention where to use their product. By not explicitly mentioning specific countries or regions are they getting away with testing?
Can Arduino shields be considered as "subassemblies" like what Sparkfun does to avoid testing? I would be selling the shield as a standalone module and it could be wired externally and not in the sense of a "shield". In fact, as-is it can't even operate on its own without a host, even if you powered it up by itself. I just don't see how doing EMC testing on a complete assembly (host board + shield) could make sense if I don't have control over what host board the user is going to choose. However, the caveat here is that the legal verbage seems to indicate that you can't say it's for Arduino specifically, otherwise it can't be considered a subassembly: "Subassemblies to digital devices are not subject to the technical standards in this part unless they are marketed as part of a system in which case the resulting system must comply with the applicable regulations." So if you say "shield for Arduino" or "works with Arduino Uno, Mega, Leonardo" it's no longer a subassembly? That sounds like rubbish to me and shatters all common sense of the term!

There's so much stuff involved with the certification process, it's driving me insane! Thanks to anyone who can clarify!


texts:
Can someone please clarify me what the rightmost strip of this layout is?

I know the red ones are poly, the squares are contacts, in green the n-well, in brown the p-diffusion and in blue with diagonal lines is metal 1. But what is that rightmost long strip connected to the output of the cell (output of the last inverter). Is it metal too? Why is the texture different?


texts:
I have been stuck in this problem for identify the fault location. Can anyone show me where to start on this? I'm not familiar with reading the curves so please just give me any hint.
Thank you


texts: Semiconductor common emitter configuration

texts: Please could anybody explain the CE configuration, the graphs of \$I_b\$ vs. \$V_{be}\$ and \$I_c\$ vs. \$V_{ce}\$. I can't understand which current remains fixed and how can one regulate \$V_{ce}\$ when we know that \$V_{cc}\$ is the applied voltage on the output side. Please help.


texts: What's wrong with that circuit? IR circuit with a relay and a regulator

texts:
• I want to power up the IR Circuit and the pump with the same powering source, in order to do that I used a 5V Regulator.

• The OUT of the IR circuit is 3.3V.

I have some problem here, when I connect the IR circuit's OUT to relay's coil pin, the I make the IR sensor detect some obstacle I hear some noise from the relay, and it cannot operate the pump.

What did I do wrong here?

NOTE

• I used HK4100F-DC3V-SHG Relay! HK4100F-DC3V-SHG Datasheet

• I made the IR Module myself, and I provided it's diagram.


texts: Can anyone tell me what these parts are and what they do

texts:
On the bottom of this picture there are two boxes. One with what looks like the letter y in a circle and another box which you can turn with a screw driver beside it.
What I want to know is what are these parts and what do they do?

The circuit in the picture is the photographing cell that takes the video (don't know the technical name) from a JVC GR-65 (magnetic tape camcorder)


texts: How to calculate cutoff frequency for a high pass filter in DC biasing circuit

texts:
I would like to DC bias an AC signal using a voltage divider as shown in the following schematic. I realise the bias point would be subject to noise from the power rails, but that is not a concern for this application.

simulate this circuit – Schematic created using CircuitLab

I understand that C1 and R2 (and possibly R1?) would form a passive high pass filter. I am familiar with the calculation for a high or low pass filter  involving a single capacitor and resistor but am unsure how to proceed when two resistors are used as shown.

Assuming only C1 and R2 were present, the cutoff frequency f = 1 / (2 Pi R C) = 159 Hz. Could you give me a hint what to do next when R1 is included? This is NOT a homework question.

Just for your reference, I have already considered answers to these questions:

Adding a DC bias to an AC signal for amplification and measurement

Biasing an AC voltage for input to ADC

How do I bias an AC signal for sampling?

DC biasing audio signal

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

Based on this comment:

"For signals all voltage sources have a resistance of 0 Ohms, so the both resistors are effectively in parallel. – Tom Kuschel 3 mins ago"

would it be correct to redraw the circuit as follows?

simulate this circuit

The parallel resistance (10K || 10K) could then be calculated as 5K.

f = 1 / (2 Pi 5*10^3 100*10^-9) = 318 Hz


texts: Good practice splitting of power and ground nets

texts:
In a design I'm working on I've got a few discrete sections with dedicated purposes, mostly independent of each other but with a few basic interconnects (e.g. SPI / UART).

In order to make testing during fabrication easy I've isolated the power and ground nets for each section with 0R resistors, so that I can easily power up and test each section at a time. Each section also has its own decoupling capacitors with a single connection to ground and power rails at the 0R resistors.

As an example, I've got an Atmel ATMega328P-AU with its own +5V and GND nets, which then has a 0.1uF ceramic for decoupling, before passing through a pair of 0R resistors to the main ground and power planes. I've then got an LED display driver (MAX7219) with the same design, but with 1uF and 10uF reservoir capacitors due to the higher current demands, again with 0R resistors connecting the nets to power and ground. I'm doing the same again for an ESP8266 module.

My design isn't particularly sensitive and isn't going in an environment where people care about RF noise (aside from legal requirements), but I'm trying to be as careful as possible because any maintenance work on them is going to be near impossible after deployment, and I don't want them glitching out. The supply itself is expected to be fairly clean and I'm driving everything off a DI ATP1509-50 buck regulator.

Is this a sensible approach? Are there any guidelines for good practice on when/how to split power and ground nets like this?


texts: What is name of semi-cut headers in KiCAD?

texts:
I'm looking for a "semi-cut headers" footprint in KiCAD.
Saying "semi-cut header" I mean a footprint which you can use either for soldering traditional pins or solder your board on top of other board.
Like on this image:

The questions are:

What is the proper name for them?
Thanks to '@alex.forencich' and '@Tony Stewart Sunnyskyguy EE75' these parts are called castellated edges, castellation, castellation terminal,castellated mounting holes, castellated vias or plated half-holes. I also found good instructions on the dimensions requirements of those here.

Are there any footprints in KiCad for that (and where to find them)?
No, they don't exist as ready-to-go solutions! I did find only general design suggestions here

Thanks!


texts:
I'm making a space-sensitive circuit for a friend that uses an SR Latch to trigger an LED to go on (and then stay on) once a laser hits an IR receiver, with a button to reset. My only problem is, I can't find any 8-pin latch chips in DIP format (So I can put it on a breadboard/veroboard) anywhere! I had the idea of getting a dual NOR gate 8 pin chip and wiring the latch myself, however I cannot find any of these anywhere either. As the enclosure I wish to put this in is very small, I don't believe it would fit a 14-pin quad NOR chip.

Does anyone know how I can combat this?


texts: What is the purpose of the resistor in parallel?

texts:
I'm a beginner in electronics, and I have a rather stupid question.
On the circuit below, why is there a need for the second resistor (2 ohm) in parallel to the 2nd lamp?


texts: Is it safe to externally power a net normally powered by a SMPS (3.3v buck)?

texts:
I have a board which has a microcontroller powered by a 3.3V buck and I need to know if it will harm the buck to power the net that the buck usually powers with a bench-top power supply.

A bit of context: I'm running into this issue because in order for my battery to charge, my microcontroller must contact the battery management board via I2C and tell the board that it's ok to charge the battery from wall power. However, when the battery fully runs down, the microcontroller cannot tell the battery management board to charge the battery because it's not powered (oops). This issue will be fixed in the next iteration of boards and is not the subject of this post, just wanted to provide some context.

So, in order to get the microcontroller to talk to the battery management board, I want to power the net that powers the microcontroller externally with a power supply, which should allow the microcontroller to tell the battery management board to charge the battery and turn on the buck. To prevent two power supplies from powering the 3.3V net simultaneously, I want to use the body diode of a MOSFET between the external power supply and the 3.3V net, so that when the buck kicks in, the potential on the cathode of the body diode will be higher than the anode, and the external power supply will immediately stop providing power. To ensure the potential is greater on the buck side, I'll set my power supply to ~2.9V (my microcontroller accepts voltages as low as 2.0V).

TLDR;

I have a board which has a microcontroller powered by a 3.3V buck and I need to know if it will harm the buck to power the net that the buck usually powers externally. Here is a high-level schematic of the buck:

Will applying external power to the output of this buck harm the buck?


texts: Ideas for precisely moving a small object in 2 dimensions?

texts:
We would like to precisely control the position of a small object in a X-Y plane. The object we are moving contains a LED diode and some optics.
The restrictions are:

The total area is 9mm x 6mm
We'd like to position the object within ±0.1 mm within this area.
We will move stepwise (Move 0.1 mm, wait there a while, move another 0.1mm...)
Expensive components are OK :)
However, we have very limited size - the smaller the solution, the better.
The object we are moving is very light (only a few grams) and can be altered as needed.

Our ideas so far:

1) Building a miniature X-Y table.
We're thinking this could be designed to satisfy the positioning requirements, but the total solution (including stepper motors etc) would probably be larger than we were hoping for.

2) Using electromagnets.
Given that our object is very light, we might be able to control its position using reasonably sized electromagnets.

Can you think of any other way of attacking this problem?

The question is similar to this question, which assumes a much larger scale (30x30 cm).


texts: RFID IC (MFRC522) with 50-Ohm antenna (taoglas fxr.01.A)

texts:
I am trying to make the MFRC522 (https://www.nxp.com/documents/data_sheet/MFRC522.pdf) to work with a taoglas 50-Ohm antenna (http://taoglas.com/images/product_images/original_images/FXR.01.07.0100C.A.pdf)

To start I based my schematic and layout in the arduino RFID board but the problem here is that this board uses a PCB antenna and the circuit is composed with EM filter and impedance matching.

I think that as I am using a 50-Ohm antenna, I don´t need to build the impedance matching part, but the problem is that I can´t find a place I can get a circuit for MFRC522 with a 50-Ohm antenna.

I appreciate all the help!

Thanks!

EDIT:

My question is what is the circuit I need to build between the MFRC522 and the Antenna. And what is the values of the components.


texts:
I need to transmit a video signal from a FPGA. It will be better if this signal is some kind of standard protocol like DVI-D.
There is an article that proposes to use LVDS transmitters for TMDS lines. There are also some articles which state that FPGA LVDS drivers are often too weak to drive TMDS lines because of DC pull-up. So I am trying to find a TMDS transmitter.
I looked at the TFP410. This IC serializes a parallel CMOS to a serial TMDS, but the TFP410 takes quite a lot of FPGA output pins. I also tried to find a LVDS-to-TMDS converter.

A solution from Texas Instruments is deserializing LVDS to CMOS with something like DS90C386, and then serializing CMOS to TMDS with TFP410.

A solution from the Lattice is the same.

These solutions require two ICs and quite a lot of PCB space to parallel CMOS lines. The ITE has a IT6263, LVDS-to-HDMI converter, but it's kind of weird.
There are some single LVDS-to-CML converters (actually, very few) like SN65CML100 and ADCMP606. Unfortunately each of this convertors costs as much as one TFP410.
What is the best method to transmit a DVI-D video signal from a FPGA?


texts: How do I send data over TCP from a SIM5320A?

texts:
NOTE: I have been using this as a reference.

After recently purchasing a SIM5320A breakout board (the board) I have been trying to connect it to a TCP server. After having to connect the board to an Arduino and turn the Arduino into a middle man (Data Mode, wouldn't receive +++ over the USB connection). I have tried using Data Mode (I can receive data, but I can't send anything) and Command Mode (whenever I try to use AT+CIPOPEN=0,"TCP",[IP address in quotes],[port] I get +IP ERROR: Operation not supported).

All I need to be able to do with this is open a stable TCP connection with the server and receive and send data. If sending data from Data Mode is easy enough, I would like hear that solution first, but solutions to get the connection in Command Mode are equally appreciated.


texts: PCB w/ ESP8266 NodeMCU - Multiple SPI modules not working

texts:
I've been working on a project for quite a while now, which involves the
ESP8266 NodeMCU (v1.0), as well as two SPI Modules: ENC28J60, and
RFID-RC522. With that being said, I encountered a problem recently,
which I haven't been able to resolve so far. Working with
micro-controllers and electronics is still a learning experience for me,
so my knowledge here is limited. When I assembled the prototype for my
project on breadboards, everything was working fine in the end. So I
thought I can move on, and design my first PCB (ever).
After doing so, I quickly noticed that something is not working right:
When inspecting the serial output, I found out that only the
Ethernet-module (ENC28J60) has been recognized, whereas the
initialization of the RFID-module (RFID-RC522) didn't work out. My first
guess was, that the RFID-module was broken. After testing only the
module on the breadboard, the initialization of the RFID-module worked
out fine. Also, when only pluging the RFID-module into my PCB, it is
recognized without any problems.
After some research, I found out the problem might stem from the
SPI-lines on my PCB, as they should approximately have the same length
when working with high frequency devices, such as the ESP (
https://resources.pcb.cadence.com/blog/2019-tips-for-optimal-high-speed-spi-layout-routing
). So I designed another PCB, with exactly this condition (+ I also
tried to keep the SPI-routes short). When I soldered my newly designed
PCB, I still got no positive result. The problem stays the same.
Does anyone have an idea, why only one of the SPI-devices is recognized,
during initialization phase? The initialization of all the other devices
works fine. I have attached the schematics of my PCB-design to this
thread.
As a side information: I am using the LM3940 voltage regulator. When
measuring the voltage, I get almost exactly 3.3 V (as required by my
modules).
I would really appreciate any comment and help on this.
Please let me know if some information is missing. I will reply as soon
as I can.


texts: Parallel TRIAC's for greater heat dissipation

texts:
Is it possible to parallel TRIACS to lower heat dissipation per device?

If so, what would be the best strategy to ensure balanced current sharing between devices?

The target application is to switch mains power at up to 20 amps.  The physical location would preclude heat-sinking(very small confined space) and audible clicks are not allowed.  Also, total BOM cannot be more than 3.50-4.50/load being switched.


texts:
I've bought an FPC breakout stick from: Adafruit. In its datasheet, it mentions a "mechanical pad", which is the exposed copper bar near the connection pads. What does it do, and can I utilize it while soldering the FPC cable onto the board?

Here is the picture of the stick:


texts:
Working on a new board, I have to face some requirements to ensure the performance of the whole system once is manufactured.
PCB is a 4-layer one, and it has both analog and digital components. But the main issue is due to power ground because of the need of having to DC converters, one step-down (Buck, red square) and one step-up (boost, pink square).
PCB are divided as:

L1: Power traces & some signal traces.
L2: GND.
L3: Pignal traces.
L4: GND, and one power trace surrounding the PCB (to avoid split the GND plane as much as possible).

Well, the doubts come at ground planes placement. They should be separated planes (analog and power), but at the same time they should be joined at one point near to ICs (DC converters).
Then, which would be the best option to reduce the noise?
I have thought in two different ways.

Power ground planes on L1, surrounded by Analog ground plane. At same time connected between them through IC's thermpad vias array, at L2, L3 & L4 layers.
Power ground planes on L1 & L2, surrounded by Analog gorund plane. And connected to L3 & L4 ground planes through thermpad array.
Best solution proposals are welcome.

Also, design includes a Li-Ion charger plus a fuel gauge which, by the moment, are connected to Analog ground plane.

Taking advantage of this thread, would it be better to add EMI shields for DC converters to reduce radiation?

EDIT:
So, attending at your suggestions the best options is as follows:

Board has an entire ground plane, connected to other layers ground planes with bunch of vias, separated a distance shorter than 2.54mm (< lambda/20).
Noise should be reduced at minimum.
There are digital signals (yellow polygon ) under Analog part. Would they affect adding noise to analog part?
[Sorry, the traces are orange and are not properly shown at picture]
Shaping the plane layers may not be the best option here because I need to separate analog and digital ground planes at both ICs, so due to the actual component placement I will almost split ground plane in two.

Take a look to purple lines, there will be a slot for 'connecting' both ground planes, which could increase the current loops through it. It not seems a smart solution in this case.
What do you consider as the best option?


texts: Can I reposition the induction coil in a Qi charger

texts:
I have recently bought a Qi wireless charging case for my phone as a car mount that I was bought for Christmas had a Qi charger build into it. Both work well, but are the coils are misaligned by about half an inch.

I've taken the charger apart and can see the coil and the circuitry, the PCB cannot be moved, but I could reposition the coil. However the ends of the coils that are soldered onto the PCB are not long enough.

Can I splice in some similar gauge plastic coated wire so that there is enough slack to be able to move the coil, or does it need to be a specific wire type.


texts: Charging appliances with chargers of different amperage (safety & duration)

texts:
Safety

Will the battery or charger be damaged if I use a 1A charger to charge a 2.1A appliance?

Will the battery or charger be damaged if I use a 2.1A charger to charge a 1A appliance?

Duration

I have tried both of the above. What I notice is that when I use the 1A charger to charge the 2.1A appliance, the charging time is extremely long. I understand that because Q = It, a smaller current would take longer to deliver the same amount of charges.

Conversely, when I use the 2.1A charger to charge the 1A appliance, should I expect the charging time to be shorter, or the same as if I used a 1A charger?


texts: Can I adjust the volume of a DAC using PWM?

texts:
Here is a circuit that allegedly converts PWM into a precision voltage reference:

(source: dangerousprototypes.com)

I am thinking about feeding that reference into the reference line on this MCP4921 DAC. My goal is to generate waveforms that use the entire range I need (0-2v) and be able to digitally adjust the volume or max output level without losing the 12-bit precision. An option I hope to avoid is using 1 or 2 digipots on the output. For example, I could generate a 1v sinewave (instead of the maximum 2v), but the wave would not have as high a resolution as if I generated a full sine wave, but with respect to a 1v reference instead of 2.

I'm also hoping this circuit will help me avoid using 1 DAC as the reference to a 2nd DAC.

Question #1:

Is it even acceptable to vary the reference on the DAC, or is it meant to be constant? From what I can see, it seems doable.

Question #2:

Am I totally off track? Is there a better way to solve this problem?

Question #3:

Assuming that this is a possible solution and I'm not totally off track, how would you go about converting the +-2495mV range to a 0-2495mV single supply range? I'd like to be able to adjust this reference as high-res as possible within that range using the PWM from the uC.


texts: Sensing external power switch for internal enable pin

texts:
I am working on the following device:
It has the shape of a AA battery, but includes a small Li-Ion battery, an ESP8285, a MP2109 (dual DC-DC converter) that outputs 3.3V and 1.5V and some MOSFETS that control the power output. Basically, it should behave like a AA battery that has power on/off and PWM control over WiFi.

It should be used for small devices like LEDs or vibration motors that have an additional power switch.

As the ESP8285 consumes quite a lot of power with WiFi on, I'd like the whole device to turn off when the external power switch of the external device is powered off, and when the external switch is turned on, the 3.3V rail should power on, so the ESP8285 can control the power output on the 1.5V rail.

The MP2109 has enable pins for both power rails, that turn on when the voltage on the enable pins is high.

Is there a solution to do this?


texts: Will this circuit suffer from Shoot-Through? and is there a quick fix?

texts:
I'm considering a high-side, low-side driver using the DMG1016UDW COMPLEMENTARY PAIR ENHANCEMENT MODE MOSFET from diodes.

The datasheet says The ON voltage is about 0.5V and ON the delays+rises is about 12ns, the off delays are around 27ns which might mean shoot-through is possible and could last about about 20ns (ignoring the rise time of the mcu signal).

The datasheet indicates solenoid driver as an application.  Is this not the right of driving it then? Or is shoot-through not an issue here?

simulate this circuit – Schematic created using CircuitLab


texts: What is the impact of a pass transistor on power supply noise?

texts:
I am designing an ultra-low noise 5V power supply for a DAC in an audiophile hi-fi application.  I would like to get the noise floor below 5uV lower.  I am looking to use a TPS7A4700 LDO which has a noise floor of 4uV.  This level is good. I intend to plenty of ripple filtering before and after the regulator stage.
However, I need to supply 3A and the TPS7A4700 only drives 1A, tops.  Hence I am considering using the classic pass transistor design (from the National Semiconductor Handbook):

My question is - what is the effect of the pass transistor on the overall noise level?  Also any suggested devices or proven circuits for this task?
Thanks


texts:
Here is all the circuitry I have.

I only found thisdata sheet  which may be for this anemometer: http://www.synchrodan.hu/letoltes/kriwan/kulsoerzekelok/szel/N292_INT10K_69000248_e.pdf

What I don't get is is it pulse output or current output? There is current source sign and a  pulse sign for the same output. I'm confused.


texts: I've been trying to work with the Microsemi SmartFusion FPGA/MCU SOC boards and their "free" toolchain that includes an Eclipse-based "SoftConsole" IDE that appears to be based on the GNU C/C++ compiler chain.  The Actel website claims the compiler supports C and C++ but the FAQ says [warning: pdf] C++ projects are not supported.  Have any of you succeeded in creating simple C++ classes/objects with the tools?


texts: How does gm get that value in the following question?

texts:
I'm not sure how gm got its value.

I do know that it gets the value Id/Vgs.


texts: How can the infinite reactance of either primary or secondary in an ideal transformer draw current?

texts:
Assumption 1:
An "ideal" transformer is said to have very large primary, secondary, and mutual reactance.. (self-inductance/mutual-inductance tending toward infinity), has a unity coupling coefficient (zero leakage flux), High or infinite magnetic permeability, absorbs zero real power (is lossless, 100% efficient).

Assumption 2:
From a pure circuit analytical and mathematical standpoint, and without the "real" model elements, the infinite primary and secondary inductances in the "ideal" transformer will draw current when secondary load is not open, and zero current when the secondary load is open or tends to infinity.

Problem 1: How can the infinite reactance of either primary or secondary draw the current in assumption 2?

Problem 2: The secondary load gets transformed and appears in parallel to the primary inductance, so if the primary reactance is virtually open, why even put it in the circuit? what good does this do?...there are an infinite amount of parallel opens in any given circuit.

Thanks in advance!


texts: Fine wire for breakout board soldering that won't break

texts:
I've been using silicone sheathed stainless steel wire (30 awg) with a 1.27mm breakout board. The wires cannot be secured (it's tight in the thing I'm building), and they easily break off at the point where the sheathing is stripped back. I notice this happens from the wires swaying back and forth. Eventually they wiggle so much that they break.
I can't really use any larger wire. I've noticed the same thing with 28 awg wire, so I don't think that will help either. Is this just because it is stainless? Would I have better luck with copper? Any pointers on how to do this correctly?


texts: Why is ISE / XLS is mapping a signal to the global clock GCK0?

texts:
I've synthesized a design for a Coolrunner II CPLD.  I intend to use the CPLD's internal clock.  I have an input named CLK.  I look at the fitter report and I see this:

** Global Control Resources **

GCK         GSR         GTS         DGE
Used/Tot    Used/Tot    Used/Tot    Used/Tot
1/3         0/1         0/4         0/0

Signal 'CLK' mapped onto global clock net GCK0.

** 16 Inputs **

Signal                                    Bank Loc     Pin   Pin       Pin     I/O      I/O
Name                                                   No.   Type      Use     STD
(snip)
CLK                                       1    FB2_7   43    GCK/I/O   GCK     LVCMOS18 KPR

Of course, CLK is indeed the name of the input I'd like mapped to the clock.  But how did it know to do this?

One 'gimme' is that CLK is a standard name and XST made a good guess.  So I renamed every CLK signal in the design to 'XXX'.

I re-synthesized (?) and now the report says:

Signal 'XXX' mapped onto global clock net GCK0.

So what gives here.  How is this working?

All that being accepted, will XXX now be the hardware clock, or is there some other step I must take?

EDIT: where XXX is used.

always@(posedge foo)    //create 1 and 2 pipe delays of inputs
begin
    aq2 <= aq1;
    aq1 <= aquad;
    bq2 <= bq1;
    bq1 <= bquad;
end

This is in a quadrature decoding module.  XXX is passed as an argument.  foo is XXX here.  Of course, this is just Verilog, I don't know what it's doing under the hood.

Edit 2 - enlightenment has occurred.

I have misunderstood what GCK is.  I thought it was a clock signal generated by and internal to the CPLD.  It is not.  The GC stands for 'Global Control'.  It's an architectural mechanism that allows a signal to be propagated around the CPLD's macrocells at very low cost and low skew.  It's a network, not a clock.  The CoolRunner II does not have an internal clock.  I will have to conjure a clock and connect it to pin #43 (the GCK pin) of my xc2c64a CPLD.


texts: Working with Mentor Graphics xPCB Planner\xPCB Layout and OrCAD

texts:
I'm working with Mentor Graphics xPCB Planner (very similar to xPCB Layout) for placement and OrCAD Capture CIS 16.5 for schematic design.
I'm interested in working with both tools in parallel, where I can select a component in OrCAD and see where it is located in xPCB Planner.
I would appreciate some help.


texts:
I am in need of an intermediate frequency (IF filter) for somewhere around 200 Khz as intermediate frequency. However, I know just the bare minimum of filter design ( learnt all that a couple of days back) and am relying on software tools to give me the circuit and component values.

Needless to say, my expectations are not met. This is the latest design which I have tried :

------->>

[ It is a 6th order active high pass filter ( Butterworth) . The op amps are cascaded, the third one being in the last image ; cutoff being 135 Khz. It would have been attached to a Low pass filter to complete the bandpass if everything was OK ]

From the various articles describing superhet receiver, I believe the IF filter has to be very sharp, else tuning is not proper. However, all the designs so far I have tried of active filters ( I actually started from 2nd order and kept increasing the order), I observe the following :

1) Even in this 6th order design, I am not able to get the required sharp cutoff.

2) The observed output (regular sine) for this high pass type starts to begin from around 200 Khz. There IS an output above 100 Khz, but with the shape of sine distorted. What I believe I need is AN ATTENUATED output, not A DISTORTED output( otherwise wont it create problem in demodulation stage ?), for signals lying outside the passband.

3) Lower order filters, obviously give a more poor performance.

Here are some outputs at different freq :

I also tried ( again using software tools) passive LC filters. However, they tend to heavily distort the signal even in the passband ( although they have very sharp cutoffs).

Now my question is :

1) Is the performance I am getting from this 6th order active filter adequate ( I am not interested in pro level performance; just adequate performance would do) for the purpose of IF filter ?

2) If not, then what is the solution ? (I dont think increasing orders would solve this)

Thank you.


texts: In this project, where does the rectifier go?

texts:
I was a backer of an early Kickstarter project, and now the project leads have dissapeared. Before they left, they offered some advice to fix some of their faulty units. Here's a picture of the project in question:

And the only help I have is "Too much current for the UF4007 to handle; it's only rated for one amp." (The UF4007 is part D1 in the board, above: datasheet) and a link to a new part which looks to be an "8A, 600V STEALTH Rectifier".

I got the replacement parts, and they look like MOSFETs, but are much narrower than the only diode I see (D1). I could bend the legs out, but because they're flat metal, they don't bend easily. What should I do?

Edit:

Like Madmanguruman says below, it's the current that is killing it. Couldn't I just replace the failing diode with one that has a higher rating? How about this UF2007 that is rated for 2A instead of only one?

Edit2:

Here's a link to the original assembly instructions: http://xwl.me/plasmaspeaker/


texts: Transform a 0-10V into 0-5V and use op-amps as buffers?

texts:
I would like to transform a 0-10V into a 0-5V so I can read it with "5V MCU" (like the AVR/Arduinos).

In the most basic case I would just put 2 resistors and do a divider, but since I don't know how that would affect the signal source I figure that I could add a buffer with op-amps since it would be safer.

So I could add a voltage follower on both sides of the divider.

simulate this circuit – Schematic created using CircuitLab

Or I could do a amplifier with amplification with 0.5 and then a voltage follower as a buffer.

simulate this circuit

Is it overkill to add the op-amps? Is it a good idea to do this kind of things, or is there another way?


texts: ATtiny/ATmega programmer board - need a 6 x 1:3 Mux solution

texts:
Hey so I'm trying to create a circuit on perf board that allows me to program three different types of chips using an Arduino Duemilanove as ISP.  Those chips are the ATtiny85, ATtiny84, and ATMega328.

I want to use one 28-pin ZIF socket for all 3 chips, and not have to remember a specific placement for the chip, so I just want each chip to sit at the very top of the ZIF socket for the 8-pin 85 and 14-pin 84.

So I've mapped out all the connections that will need to go into the ZIF socket, and now have come across a switching problem.

Essentially there will be 3 states, one for each type of chip, and there are 6 signals that need to be switched (5V, GND, RST, MOSI, MISO, and SCK).

I've mapped out which pins each signal will need to go to, but now I need an analog switch IC or analog multiplexer to make this happen.

For example, MOSI looks like this:

State 1: MOSI -> 25
State 2: MOSI -> 7
State 3: MOSI -> 17

Since I have 6 signals, and 3 states, ideally a 6 channel 1:3 Demux would be perfect, but I think it's pretty certain those don't exist. It seems like the most practical I can find so far is a dual channel 1:4 demux, so I would need to use 3 of those.

Essentially what I'm here for is 1) Does anybody know of a better way to do this, or 2) Does anybody know of any IC's that can solve this?


texts:
I am working on a PIC24 project, and I went to the project folder and moved a file to another directory inside the project folder, however, I got a makefile error. I created a new project and copied the source codes into the project I still get the same error.
make -f nbproject/Makefile-default.mk SUBPROJECTS= .build-conf
make[1]: Entering directory 'C:/Users/forat/MPLABXProjects/SerialComm_2_Micros_2.X'
make  -f nbproject/Makefile-default.mk dist/default/production/SerialComm_2_Micros_2.X.production.hex
make[2]: Entering directory 'C:/Users/forat/MPLABXProjects/SerialComm_2_Micros_2.X'
make[2]: *** No rule to make target 'build/default/production/System.o', needed by 'dist/default/production/SerialComm_2_Micros_2.X.production.hex'.  Stop.
make[2]: *** Waiting for unfinished jobs....
"C:\Program Files\Microchip\xc16\v1.60\bin\xc16-gcc.exe"   main.c  -o build/default/production/main.o  -c -mcpu=24FJ1024GB610  -MMD -MF "build/default/production/main.o.d"      -mno-eds-warn  -g -omf=elf -DXPRJ_default=default  -legacy-libc    -O0 -msmart-io=1 -Wall -msfr-warn=off    -mdfp="C:/Program Files (x86)/Microchip/MPLABX/v5.40/packs/Microchip/PIC24F-GA-GB_DFP/1.3.109/xc16"
make[1]: *** [.build-conf] Error 2
make: *** [.build-impl] Error 2
make[2]: Leaving directory 'C:/Users/forat/MPLABXProjects/SerialComm_2_Micros_2.X'
nbproject/Makefile-default.mk:91: recipe for target '.build-conf' failed
make[1]: Leaving directory 'C:/Users/forat/MPLABXProjects/SerialComm_2_Micros_2.X'
nbproject/Makefile-impl.mk:39: recipe for target '.build-impl' failed

BUILD FAILED (exit value 2, total time: 1s)

Can someone help me, into why I got this error, I thought since it is not a syntax error, then if I create a new project and copied and pasted the code, I won't have this error.
I created a test project with a simple c code, and it got built successfully without any issues, it is only with my project that I got this error.
Your help is appreciated.
EDIT SOLUTION
Hi guys,
in the error, it mentions the problem is with System.o I deleted the file System.h and created a new one with the same name and copied the code in it, the error disappeared when I build it.
Thank you guys for your help.


texts: How to do a loopback test of a parallel port?

texts:
I have connected pin 2 to pin 3, pin 4 to pin 5, and pin 6 to pin 20.

Can someone please tell me if this is the correct wiring for loopback testing a parallel port?

Ia am using BurnInTest 7.1 Pro by PassMark Software for the test. Is this the right software for this job? This is the error I receive.

  Corruption. Data received didn't match data sent. Check plug is
  connected.

The image above shows the program window 52 seconds into the test.

The image above shows the status window 1 minute and 47 seconds into the test.

As you can tell by the images posted above, there is something wrong. How is it possible to send 40 bytes and recieve 80 bytes? I mean how can you receive twice as much as you send? This makes no sense to me. Does it make sense to you? You can see that the number of errors shown in this window is 39, which is more or less the same amount redundant data that was received.

80-40=40≈39

Can I trust these results? I have used the same program to loopback test a serial port and it did, and after 15 minutes of testing it gave me a big "PASSED" message in green letter. So I know it works for serial port testing. But does that make it trustworthy/reliable for parallal port testing?

Update

A DB25 connector can be used either for parallel communication or for serial communication. A DE9 connector can only be used for serial communciation. My mistake here was that I wired a DB25 connector for serial communication, instead of parallel. After rewiring the loopback test passed flawlessly.

See the answer below for the proper wiring of a DB25 for parallel communication.

Here are some images that show the same test being done with the proper parallel wiring. I have taken these screenshots with respect to the elapsed time of the previous ones, so you can compare them.

Main program window, 52 seconds into the test.

The status window, 1 minute and 47 seconds into the test.

Passing the test...

The test result window.

Main program window showing test duration, number of cycles, operations and result.

The DB25 connector...

Here's a picture of the connector. It's a female connector. This made jumpering harder for me.

I didn't have a proper, insulated wire with the right size. So I used a 1.0 mm diameter brass wire instead. It's a good thing it's sturdy and yet soft enough for easy bending. I made sure not to touch any adjecent conductor. It's hard to find electrical wire with the diameter of 1 mm, they are rare. This 1 mm was a perfect fit. It can be slightly thicker, but not less than that. You can use a paper clip, a.k.a. "paper clip test", but it's a bit sturdier (thicker) and hard to work with.


texts:
BJT Circuit Problem
I have already posted a similar problem in the link above. I am facing the same issue in this circuit. What will be the state of the 2 BJT's Cutoff, Saturated or Active ?
Please suggest me a generalised approach to tackle such problems.


texts: Unclear about fluctuating frequency when using NPN transistor

texts:
I am trying to build a more complex circuit but am having trouble starting off. I am using tone() to generate a frequency on my 5V Arduino Nano on D3. If I measure the frequency directly at D3 to GND, I measure a consistent 123.15hz which is what I'm looking for. Now, If I use an NPN transistor(I have tried a S8050 and BC337) the frequency jumps between 107hz and 123hz when I measure at the emitter. I am using a 1k ohm resistor in between D3 and the base of the NPN.
Any suggestions would be greatly appreciated.
Thank you.


texts:
I am trying to design an audio amplifier based on a digital input chip (TAS6424-Q1 for example) with two, stereo, I2S enabled sources for the input (for example the BM83 Bluetooth module and the Si4688-A10 radio receiver). An MCU would be connected via I2C for control of these devices.
Does the I2S standard allow both these devices to share the same I2S bus connection? If so, how would I select which device is enabled as the input?


texts: In many devboards and reference schematics a couple of identical LDOs (or DC-DC) are used for high load. Is there a reason to use multiple low power LDOs instead of using single high power LDO?


texts: Effect of Changing polling time in hid interrupt transfer

texts: I have interfaced a HID bar-code scanner with LPC2468 using interrupt transfer. The polling interval which i receive(from bar-code) in the Endpoint Descriptor is 10 ms. What will happen if i increase or decrease this polling interval.


texts: 480v motor, running like a bat out of hell.

texts:
I have a 480v motor that is connected to an auger.

When the auger fills up, the torque from the motor continues to drive it and then just snaps the shaft clean in half.

I am looking to build something that decreases power as the amp draw increases. Hopefully preventing the snapping of another shaft.

I’m open to any thoughts and I’m pretty new to  electronics.


texts: Jitter measurement in High speed serial link - Random jitter mean not 0

texts:
I made some jitter measurements of my high speed serial link yesterday. Now i'm analysing the jitter sources, and found out, my random jitter is often not around zero, most time about -1 .. -0.5ps.

What's the reason for a not 0 mean of the random jitter?

The pictures show a plot of the random/periodic jitter and the total jitter.
The scope cannot give a seperate plot for random jitter and periodic jitter, but the second should be similar to a dual dirac function, so symetric around 0. So why is my RJPJ not around 0?

The TJ is a convolution from RJPJ with Data dependend Jitter(DDJ). DDJ is caused from a PRBS-7.

Edit:
I am measuring differential transceiver of a fpga, connected by two skew matched cables. There is no "known" asymmetry in my measurement. If this would be static asymmetry, every measurement would have been an equal RJ, i think. I have a 16Gbit/s NRZ signal, the cables are rated up to 18Ghz, the connectors on the Board 12GHz.


texts: Hard on/off switch RPI with graceful shutdown

texts:
I am building a WiFI solution for a DSLR camera; so after connecting you can view the image via a webbrowser.
For this I gutted a so called battery 'grip', which has buttons with which normally you can take a picture, use the scroll button for ISO etc. See picture

The buttons arre connected to a RPI and I use these to control the image shown in the browser via websockets, this works perfectly.

THe problem is: i want the hard on/off switch (so it is in ON OR OFF postion) to shutdown and startup the RPI.

I have a 3cell li-ion battery (15000mah) connected to a chinese buck converter with 5v in, 5v out and batt out.

So my first idead was: 5v out -> switch -> diode -> capacitor -> rpi.

With this i should get a reading before the diode to GPIO pin to see if the switch is toggled, BUT the diode gives a voltage drop, so this does not work.

There are a lot of examples, but they only use momentary switches AND/OR relays, which i don;t wan't because of the current draw.

So have any one of you any idea on how to solve this?

Thanks in advance!!


texts: Understanding basic behavioural Verilog: simple RAM module

texts:
My interest is more in what the actual synthesized circuit will look like, and what components it will be built from. Here is an example 64x1 RAM module:

module ram64X1 (clk, we, d, addr, q);

   input clk, we, d;
   input [5:0] addr;
   output q;
   reg [63:0] temp;

   always @ (posedge clk)
      if(we)
         temp[addr] <= d;
   assign q = temp[addr];

endmodule

Just to make sure I understand the logic: addr indexes a particular spot in the 64x1 bit array. It takes the value d and places it at that entry, while also returning the old value q that was there before. Is this correct?

My main question is what circuits this will translate into if we synthesize with say, a standard cell library. The reg object seems to be an array of flip-flops clocked by clk. I don't know what logic circuits take addr[5:0] and index into this array. A really wide 64-to-1 mux with addr as the select wire? I'd also be curious as to how those muxes are built typically.


texts: EMI about Y capacitor and common mode noise

texts:
I do not get how the capacitor localized between the input voltage and the earth can help to reduce the common mode noise as the input voltage is at a voltage which is fixed and the earth voltage is also fixed. So there is no variation across the capacitor and no current can flow through it. Can someone can explain how it works?
I completely understand that a current flow through the parasitic capacitor between the drain and the earth as the voltage drain is changing and the voltage earth is fixed.

Thank you very much and have a nice day!


texts: Can a Variac be modified to output higher voltages?

texts:
Since variable transformers can be had quite cheaply these days (under AUD 45 / USD 30 / EUR 27 today for a 500 watt one through eBay from China) they are cheap enough to experiment with.

I bought one of these and took it apart, and I see that one of the wires in the coil at the 220 V point has had its insulation stripped and a wire soldered to it, going to the mains input.  I am guessing therefore that if I move this wire to a different point in the coil, I will be able to change the range of output voltages that the unit can produce.

If I want my Variac to output between 0 V and 415 V (just picking any voltage above the 265 V limit it has now) when fed with a 240 V input, am I correct in assuming that all I would need to do is move the mains input wire to roughly 60% along the coil?  (240 / 415 = 57.8%).

What sort of issues would I have to consider when doing something like this?  The only one I can think of is that the magnet wire used to wind the coil would need to have insulation thick enough to handle the increased voltage, however the variable transformer design suggests that this may not be so important.  Since the arm likely connects two coil loops together anyway, the voltage between any two wires in the coil would be quite small.  This might increase from say 1 V to 2V which I am guessing is unlikely to be a problem.  The other wires all have standard 600 V insulation so it would seem to be an easy enough modification to do.

Have I missed anything?  Would this kind of modification lead to other problems?


texts: Can I use the Netduino USB as a serial port?

texts:
A serial port demo shows how to use GPIOs to communicate through a second USB connection.

But as a Arduino developer I'm used to use the same USB for both programming and runtime communication.

Can I do the same with Netduino?


texts: What is the difference between the forward transfer function and closed-loop transfer function?

texts:
We can define the forward transfer function as
$$l(s)=g(s)r(s)$$
Thus, the closed-loop transfer function is

$$h(s)=\frac{g(s)r(s)}{1+g(s)r(s)}$$

with \$g(s)r(s)\$ the multiplication between all the system transfer functions.
It is obviously the main difference is the definition itself (the formula) but, what does it tell us about the system and about the poles/zeros?


texts: typing error showing on quartus prime lite?

texts:
I am trying for few hours to understand why Quartus Prime Lite keep showing an error when I compile this basic VHDL code, I kept it like this to understand why it is showing an error just by typing!!!.could be my German keyboard or?
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
----------------------------------------

entity spiadc is
port(      i_clk,i_reset, i_read  : in std_logic;
        o_data: out std_logic_vector(11 downto 0) ;

o_sclk: out std_logic );

end spiadc;

----------------------------------------
--          o_sclk                : out std_logic;
--          o_cs                  : out std_logic;
--          i_miso,i_start        : in  std_logic

--       i_clk: in std_logic;

  architecture behv2 of spiadc is
  begin

  o_sclk <= i_clk;

end behv2;


texts: Difficulties with Representation of Half Wave and Full Wave Rectifiers on PartSim

texts:
After tweaking the domains, the run-time duration of the simulation and the location of the probe I discovered that there was no mistake. Below I've attached a picture of the graph blown-up.

Recently I've become interested in self-studying electrical circuits and upon my scholastic quest I've stumbled upon a problem.

To my understanding, a half-wave rectifier is meant to eliminate the "negative portion" when graphed using a sine representation when tested on a simulator, but I don't seem to be getting the same result.

The other problem that I'm facing is trying to run a simulation of a full-wave rectifier.

I'm using PartSim, which is a completely free simulator (Not an expert with it... yet).

I'll attach some pictures of the circuits that I made and also the apparent simulation results.

Thanks in advance!

My Diagram of Half Wave Rect:

Graph of Simulation of Half Wave Rectifier:

Zoomed in Depiction of Graph:

My Diagram of Full Wave Rect:


texts: Component keep-out on particular layer in Altium

texts: I'm making a heat sink footprint for TO220 in Altium. I think route tracks under the heat sink is not a good idea. So I want to give the footprint a keep-out, but the keep-out region on Keep-Out layer applied to both top and bottom layer, though my heat sink sits on the top layer. So any methods to add a keep-out region only applied to the layer where the footprint sit on?


texts:
I recently bought a set of four "light-control sensor switch" from ebay (link). Circuit diagram below.

I put the circuit together (it was a DIY kit) and connected a protected LED at the output. The circuit doesn't work. I admit that I did not look at the diagram before buying these. I have built similar working circuits on my own but the base of Q1 was always connected BETWEEN R1 and the LDR (with a much lower R1 at that).

Can anyone see how this circuit can be activated by light/dark in any circumstance? Please explain it to me if you do.

Thanks.

simulate this circuit – Schematic created using CircuitLab


texts: WiFi Controller system for a motor Relay Output

texts:
I'm trying to use a 12 volt WiFi relay setup to control a 12 volt DC motor. The WiFi relay has eight 10 A SPDT relays in it and the motor is 15 A. I understand how to wire it directly to the two relays that are in the box, but I'm lost after that. Here are my questions:

Since I'm using two 10 A relays at the same time to control the motor (positive through one and ground through the other), does this mean that I have a 20 A capacity with the relays?

How else could I wire this up to increase the relay capacity (or run the signals from the WiFi relays) to other relays and protect the WiFi relay box?

Here's the info on the WiFi relay:


texts: How do light switches with a small LED light indicator work?

texts:
I found this type of switch typically used for residential housing and though it will look good for my project. So basically its a glorified push-button.
I would like to use it with 5v along a 1meter cable for interfacing to my project. But i do not know if will work its rated 110v-220v so i do not know if 5v will work. Its only a contact inside so it should work, but it has a LED indicator inside so it must have some sort of circuit . These wall switches with led indicators are common on households but i could not find a schematic for it.


texts: Raspberry Pi GPIO Output On Startup Safety

texts:
I'm working with a simple circuit using an infrared breakbeam sensor and a Raspberry Pi. Here's my best attempt to diagram how I have the circuit set up.

The Raspberry Pi will also supply both power and ground. I noticed in the Raspberry Pi 2 User Manual I got with the Pi (from Vilros) that there is a short section where it is mentioned that the Pi's GPIO pins can momentarily be set to outputs when the Pi starts up, and that if you have a circuit which connects one of the pins (as an intended input) to ground it could cause a short circuit and damage the Pi if/when the pin gets reset to an output on reboot. They recommend a 300 ohm resistor between the GPIO pin and ground pin. So I'm wondering if I can/should just put a 330 ohm resistor between the black wires (the transmitter and receiver share the same ground pin) and the ground pin to prevent a possible short circuit on startup. I was also wondering if maybe putting a diode on the white wire of the receiver would also prevent this issue.


texts: Picking a voltage regulator for 12V/10A input -> 3V/290mA output

texts:
Am I doing the correctly?

ATSAMD21G17A-AU p.906 - ARM-Based Microcontroller - 7mA

MAX-7Q-0 p.16 - GNSS module (GPS) - 67mA

LPS25H P.8 - Barometer - 25uA

Si7013-A20-IM1 p.4 - Temperature - 180uA

AT24MAC602-STUM-T p.6 - EEPROM - 3mA

XB24-Z7WIT-004 p.2 - ZigBee - 220mA

So total about 290mA current draw. The circuit is running at 3.3V. I'd like it to handle up to 12V/10A input.

Would something like the MIC5219-3.3YM5-TR be OK? I did this search on Mouser. Is there a better choice?


texts: What is the minimum current I need to supply to a Spartan-6 pin in order to register a high signal?

texts:
Digging around in the spartan-6 DC and switching characteristics guide, I can't find what I'm looking for.

Also no absolute max sync/source current ratings for the user IO pins. Looking at the dev board schematic, I know that 2mA is safe based on the resistor values used, but isn't this in a datasheet somewhere?


texts: Current Consumption of CANbus (CANH and CANL)

texts:
I'm looking to use the SN65HVD230 CAN transceiver but had a question about the current consumption.

Datasheet: http://www.ti.com/lit/ds/symlink/sn65hvd230.pdf

In table 8.3 Recommended Operating Conditions, it said the high level output current for the driver is -40mA and the low level output current is 48mA. However in Table 8.5, it is said that the supply current (Icc) has a max recommended current of 17mA. How can the driver current consumption be greater than the overall supply current ?

How do I calculate the overall current consumption of the bus ? The datasheet seems to only talk about the current consumption of the receiver and driver, but not the actual CANH and CANL lines?


texts:
First of all, sorry for my lack of knowledge in the subject. I have a Nidec TA450DC B35502-35 fan which I've installed in a large wooden cabinet where my computer and other electronics sit. This cabinet of course gets hot from all the electronics inside of it. The fan forces air in from the room and goes out through openings in the top of the cabinet. This fan has 4 wires: red (+12v), black (ground), and then blue and yellow. I'm using only red and black to give the fan full 12v power.

Nidec Website

The problem is since it's at max speed, it is way too loud. I have a simple toggle switch to turn it on and off. What I would like to do is replace the toggle switch with a knob to adjust the speed. I don't know how to use the other two wires to control the speed.

What kind of knob do I need to get, and how should I wire it? The minimum setting of the knob should feed the fan with its minimum required power to spin at the lowest speed possible, and the highest setting should spin it at full possible speed.

I don't have any problem with soldering a small circuit board together for this project, I just have no idea what schematic I need to put together. I've played with electronics and their components all my life but don't know nearly enough to even begin understanding how to accomplish this. It should be simple, right? Should I be using one or both of the additional wires for this, or should I use some method of adjusting the voltage?


texts: Why is the load a resistive load, not an inductive load when I measure the current and voltage of the transmission line?

texts:
Question:

Measure the transmission line of a substation. The relation between voltage and current is that the current lags the voltage for 180 degrees, so now I want to ask

Which part of transmission line did I measure, sending end or receiving end?
Is the load an inductive load, a capacitive load or a resistive load?

My answer for 1. and 2.  are as below:

I measure it at the receiving end of the transmission line, because I think everyone will want to know about the characteristic of the thing which we receive, not the characteristic of the thing which someone sends. So I think the answer should be "receiving end."
The question says "current lags the voltage for 180 degree", I think it means that \$\theta_i+180=\theta_v\$, that is ,\$\theta_v-\theta_i>0\$, so the load should be an inductive load.

However, the answers are as below:

Receiving end
Resistive load.  Why is the load a resistive load, not an inductive load? Can someone tell me the reason?


texts: I'm a new student in electrical engineering. I'm trying to make a BFO (Beat Frequency Oscillator) circuit for my university project. I didn't understand the duty of 3rd transistor and capacitors attached to it. When there are 2 oscillation voltage at different frequency, they must be connected to the mixer circuit and filtered through the low pass filter. But I cannot understand how this is done. Please can you help me?


texts:
My passive first order RC circuit is not filtering out the transient response as expected. There's barely any attenuation considering that my cut off frequency is around 2Hz and the frequency of the transient is at around 20MHz. I require a DC voltage with no ripples.

This is the original signal with transients:

This is the filtered output:

This is the circuit diagram used:

I utilized a resistor of 10k and a capacitor of 10uF.


texts: What does the flag formula symbols mean in AVR assembler documentations

texts:
I was reading about something in the assembler documentations of the AVR microcontroller and I usually come across a line used to describe how would an instruction affect specific flag in the status register.

let's take an example from ADD instruction page

  H:
  Rd3 • Rr3 + Rr3 • R3 ¯ + R3 ¯ • Rd3
  set if there was a carry
  from bit 3; cleared otherwise

In this line
Rd3 • Rr3 + Rr3 • R3 ¯ + R3 ¯ • Rd3
How can I read this line, what do those symbols mean?


texts:
Do SMD markings not apply to switches?

Here is a Matsushita switch on a keypad matrix from circa 2008:

The top is stamped with "8", "9", "R", and ":". It has the following measurements:

6.31mm width (body 6.31mm square)
6.90mm length with J-legs
3.6mm total height

Pulling this one was a major pain - pads lifted way too easily. Luckily one of those pads is mechanical only. They will need some TLC (and probably some bonding agent.)

The closest I can find is a Panasonic EVP-BFAC1A000 but this is not an exact match.  Can anyone positively ID this switch?


texts: Why carriers move when Electric field is applied on Haynes-Shockley experiment

texts: I would like to know why excess carriers/minority move when an electric field is applied at the Haynes-Shockley expirement


texts: I want to send and receive data wirelessly from 90 different areas to a central collection site. longest distance is 8.5 miles.

texts: I have 90 pump/lift stations that I would like to send information from to a central collection place (office).  The longest distance is 8.5 miles away.  most of these pump stations are line of sight over a lake.  What is the least expensive way to turn these old stations into a station that can send digital information wirelessly.  We would also need a server? to collect this data.


texts: Is exceeding Opamp Common Mode Voltage safe?

texts: I understand that when you exceed an Opamps Common mode voltage limit that the output will no longer be reliable. And that this limit is often a bit less that the supply rails. But would slightly exceeding this limit to perhaps the supply rail cause the Opamp to blow up or overheat? Or would it just cause the output to be inaccurate?


texts:
I know the basics of self-inductance, and how an inductor creates a voltage/current that opposes the increase or decrease in current.

I can't find anything on how it reacts to/blocks certain frequencies.

Can anyone tell me how inductors select or block certain frequencies?


texts: LM386 audio amplifier with push-pull output

texts:
I am trying to make a simple audio amplifier using an LM386 audio amplifier and a class AB amplifier push-pull output stage. Since I couldn't find something that explicitly combines the two (LM386 for voltage amplification and transistor for supplying the required current), I thought I might give combining the two a shot. The LM386 application was taken from the chip datasheet, and the class AB design from here.
The schematic is here. I couldn't put this on the schematic but pin 7 of the IC is connected to a 100 nF capacitor to ground, and between pins 1 and 8 there is a 10 uF capacitor in series with a 10 k potentiometer in order to set the gain from 20 to 200.
The circuit will run from a single 9V battery.

My questions are

In the LM386 datasheet the electrolytic capacitor on the output has the plus towards the amp, but on the AB amplifier the electrolytic capacitor on the input has the plus towards the transistor, ie in the opposite polarity. Could someone help me understand how these capacitors should go and what should I do here?
I thought since the current might get high, I used resistors rated for 1 W. The question is regarding the 10k pot on the input, is 4W an ok rating? Or if the input signal is too high might it get burnt out? Also, between pins 1 and 8 of the op-amp I used a small vertical potentiometer in series for the capacitor, which is rated for really low power. Is this ok?

Could someone also please verify the overall circuit and tell me if it is Ok and whether it will work or not?

Later edit: Thank you for the answers. I understand that both the LM386 (with an internal push-pull output) and the amplifier together have too much gain so I will have to remove one of them in the final project. I have made the modifications suggested. I only have one question left, whether I should leave the 2 caps back to back from the LM386, or should I just use one with the + towards the LM386 output, and why?
Also, are the modifications correct?


texts: Can gain and phase margins be obtained from step responses?

texts:
We need to comply to specific gain and phase margins requirements whereas the controller has been tuned on-line without knowing the plant transfer function (in order to save time). The response does not exhibit any overshoot, but we need to make sure we have 14dB and 30° of gain and phase margins. Can step responses be used for this?

For information, the controller is a PI type and the plant is a piezo actuator which twists a ring.


texts:
I want to insert a wire into my breadboard for prototyping, however the wire is thin so it folds and frays when I try to push it into an open slot.

Is there a particular type of pin I need to use in order bridge the gap?


texts: Thermistors' colour coding same as the resistors'?

texts:
WARNING: 30V was a mistake -- better to keep voltage down 12V as a beginner! I tested it over a very short time. Got the things hot over a long time with much less voltage -- apparently not enough energy was dissipated to destroy the components.

Thermistors are a type of resistors, according to Wikipedia. Two thermistors black-white (18p written on it) and gold-orange-gold-yellow (no text). If the colour coding is the same to resistors and reading up-to-bottom, the former is 8 Ohms and the last one is 4k Ohms. I tested both with 30V: the former warm, the last not warm, the current 0,0A (not measurable with my equipment).

Sizes are 0.2cm times 0.3cm for both of the components.

Accepted Power Estimate by size(tip): 3.14*(0.025m)^2 = 0.00196... so P ~=10^-3

How to estimate current as it was below 10^-2?
How to read thermistors' colour coding and what does 18p mean, 18 pico Ohms or some change?


texts: TIVA C series launchpads for arduino programmers

texts:
I have bought a Tiva C series Launchpad TM4C1294NCPDT by TI and wish to do a project on face recognition. I will soon get a DSP EVM by TI, but still confused which one to choose (MAY be the one with 32 bit arch.)

Actually, i have quite good experience using arduino boards (and programming them in C and assembly languages).
but shifting from arduino to TIVA C and DSP's is really difficult, please help me, AND GUIDE ME.

Zeek clarified:

Ok, Being Specific these are my problems..

I am not getting the layout of the LaunchPad.
I want to do the face recognition, will the processor and DSP give me enough computational power?
I need to connect a camera (a 5MP camera to DSP) and want to control it using the MCU (TIVA-C series) how should I do it.


texts: Is the peak-to-peak voltage the same as the peak voltage in rectified voltage?

texts:
I have a homework in which in need to calculate the peak-to-peak voltage through a half-wave rectifier, center tapped full wave rectifier, and bridge full wave rectifier. What is confusing is that when we rectify a voltage we basically cut off the negative or the positive cycle of a signal, so basically there is just one peak either in the positive or the negative side, right? So could we say that the peak-to-peak voltage is the same as the peak voltage? Also what about Vrms do we use the formula:
$$V_{\text{rms}}=V_{\text{peak}} / \sqrt{2}$$
or
$$V_{\text{rms}} = \frac{V_{\text{peak-to-peak}}}{2\sqrt{2}}$$


texts: Should a regulator be added to a circuit where the power source voltage matches the ICs?

texts:
I am trying to design a very simple circuit consisting of an accelerometer IC and a Bluetooth IC, all rated at 1.8 up to 4.something volts and thinking to use a single CR2032 cell. Seems like these usually come at 2.8 - 3V and about 250mAh current, depending on manufacturer and other factors.

I have already planned to add required capacitors around each IC, but I am wondering if I should still use a voltage regulator with this circuit?

So far the only good reason I could think of would be to prevent frying the ICs in situations where the user would manage to somehow cram up 2 batteries instead of one in the enclosure, aka making the circuit idiot-proof.


texts: Setup and hold time violation constraints for Xilinx Fifo generator

texts:
I have a problem concerning the Xilinx Fifo generator and timing contraints described in the fifo manual.

I am using the fifo generator version 9.2 (manual ) to generate a fifo.

I would like to insert the timing constraints which are suggested on page 151:

Add the following constraint to your design – this constraint sets a timing constraint to
the synchronization logic by requiring a ma
ximum set of delays. The maximum delays
used is defined by 2x of the slower clock period.
NET
<fifo_instance>
/xst_fifo_generator/gconvfifo.rf/grf.rf/gntv_or_sync_fifo.gcx.clkx/
wr_pntr_gc<0> MAXDELAY = 12 ns;
NET
<fifo_instance>
/xst_fifo_generator/gconvfifo.rf/grf.rf/gntv_or_sync_fifo.gcx.clkx/
wr_pntr_gc<1> MAXDELAY = 12 ns;
...

If I insert these contraints I get the error:

ERROR:ConstraintSystem:59
...
REG_CTRL/dev0_daq_fifo/U0/xst_fifo_generator/gconvfifo.rf/grf.rf/gntv_or_sync_fifo.gcx.clkx/
wr_pntr_gc<1>
NET not found

I expected a spelling error, so I searched for this net with PlanAhead, but I could not find a net with this name. I found a primitive which has a similar name ( rd_pntr_gc_9) but no net.

My question is now, what am I doing wrong?
Why are the nets not existing? Which nets could I use instead to apply the constraints.

I am using ISE 14.2 and a ml605 board with a Virtex 6 FPGA.

Thank you and best regards

Simone

tl;dr I want to insert the suggested timing contraints for a fifo from the manual, but I cannot find the nets which are suggested.

p.s. I have seen the answer record AR# 43210, the nets which are described there are also not existing in my design.

Edit: XST option -keep_hierarchy is set to Yes


texts: NE555P Frequency Drop to 0 after a couple of minutes?

texts:
I'm trying to build a frequency measurement circuit using NE555P and Atmega328P. The circuit is the following :

I use this library https://www.pjrc.com/teensy/td_libs_FreqCount.html

Always, The system works fine at the beginning (3 to 4 minutes) and then the frequency values start to drop until reaching 0.

Does anyone knows what causes this strange behaviour ?
Thanks in advance.


texts:
As I understand, the internal timer clock source on the STM32(F4) microcontrollers can be either APB1 or APB2.
However, I can't find which timers get which clock.

I already found ST AN4013, which explains almost everything about the timers, but not their respective internal clock source.

Does anyone know, or have a source for, exactly which clock each timer uses?


texts:
Everything I read says that the ATmega328 can provide 40mA per pin. However when I've measured the actual current provided by one pin it was showing 80mA. It was the same on every pin I tested. Anyone else noticed this? Or is it just unique to this specific one?

RM: ATMega328 datasheet


texts:
I have two pieces of single-phase fans and they are literally the same, it is ac motor and whenever I rotate it manually it produce voltage about 160-190vac. I just get the idea that it can be an ac generator, but the problem is when I connect it to 110v-220v cellphone charger, the charger is not working, the voltage drops and the generator seems to run from the voltage itself, I search it and the answer is the backfeeding.
I also connect the generator to christmas lights and there is no problem maybe because it has resistors, I also conect Led bulb using an adaptor 110v-220v and the led is blinking(it should not be) and everytime it blinks the generator get a shock, it seems to get backfeed.
The other problem is I connect these 2 ac fans and I rotate it to be a generator(160v-190v each) but they seem to be run from the voltage themselves. I had this idea to use a full rectifier, inverter or somewhat to make them a working generator with a stable of 220vac even if using.
My ideas/plans (in order):

To stop the backfeed of the generator when using. If there is no possible way to do that then using an inverter is the last option.
If ac-dc is the best way then i'll connect dc's from positive to negative, making dc volts step up then convert it to 220v ac. AC-DC-AC in short
If no. 2 didn't work, then i'll suppose to make an inverter for each generator making them ac-dc-ac and avr for each to stabilize their voltage.

Please help me guys, I need to make it possible.
Another thing I recently know, is it possible to put a ground wire to a single-phase generator to stop getting backfeed instead of transfer switch ?
The picture is the single phase motor.


texts: Verowire woes - how to reliably solder it?

texts:
I'm using Verowire (wiring pencil, Road Runner, you name it) quite often to contact test points on my board to make them accessible for measurements (oscilloscope probe, multimeter clamp ...)

Image source: Not a number.

Every now and then it happens, that the insulation will not melt away and make soldering the verowire almost impossible.

I usually have to cut off a piece and start again - which seems odd as some people are creating artworks with Verowire.

What I usually do:

Temperature 350-400 °C
Blob of solder on the iron
Insert the end of the Verowire into the blob (usually melts the insulation and tins the wire)
Solder wire to test point

Any points which I'm doing blatantly wrong in that approach?


texts: I have a PCB with several power ic's. The pcb is connected to an aluminium plate as a heatsink on the back of the PCB. How can I measure how much heat dissipates from the top of the PCB to the air? And much heat is conducted by the heating? I want to know it for the entire PCB and not only for the individual components.


texts: Why does line current equals the total apparent power divided by 3 times the phase voltage?

texts: In this circuit with frequency of 50hz and line to line voltage of 400 V why is the current \$ I_A = S_t/3V_P\$ I don't understand the logic behind since there is one Delta connection, I understand why that formula works for a Star connection but don't for the total of this circuit. The Delta load also has 12,5kw.


texts: A circuit that converts contiuous pulse signal to a stable level signal, and reverse if pulse not present

texts:
I have a 12V 3-pin computer fan that has a tachometer signal output: when the fan is spinning normally, the tacho wire is either floated or shorted to ground periodically. If you connect a pull-up resistor you can get a square wave when the fan is spinning normally, and a stable high or low when the fan blade is stuck.
I also have a piece of equipment that has a 12V fan on it, but that fan has an "alarm" output rather than tacho output, which is that when the fan is spinning normally, the alarm wire is shorted to ground, and when the blade is stuck the alarm wire is floated (or "high", if pull-up resistor is applied).
Now what I wanted to do is to use the first fan to swap out the second fan, which I need to convert that tacho pulse to a stable logic low when the fan is spinning, and when the blade is stuck there is no pulse so I can get a floating (the equipment has pull up built-in). I considered something like a 555 timer wired as monostable, but when the first fan is stuck, it will randomly output stable high (floating) or low depending on the angle of the blade, not exactly which. So what I need to detect exactly is "one or more level change in a period of time", not a specific logic level. I am pretty much stuck here since I don't have much experience in analog circuitry and I don't want a microcontroller for such a simple (or is it?) task. Are there any simple solutions? Thanks.


texts: Adding to a sum variable produces a "reals can't be synthesized" error in verilog

texts:
First, a disclaimer that this is my first time using verilog and I don't really know anything. My code is as follows:

module trapverilog(
    input CLK,
    input SIGNAL,
     input x,
    output reg OUT
    );

reg[1:0] yreg;
real sum = 0;

always @(posedge CLK)
begin
    yreg = SIGNAL; //should shift automatically
    sum = ((yreg[0] + yreg[1])*x/2) + sum; //treats x as plain h, change if treated as h/2
    OUT = sum;
end

endmodule

It produces an error saying that real data types can't be synthesized referring to the sum = ((yreg[0]... line. What does this mean, and how can I fix it?

The intent here is to create an FPGA that can perform the trapezoidal integration method which is just $$A = \frac{(b-a)(y_1+y_2)}{2}$$ In my program I'm taking $$\frac{b-a}{2}$$ as an input x and I'm also talking in a clock signal CLK and a signal to be integrated, SIGNAL.

I create a two spot register, yreg, with and when CLK is high I set yreg = SIGNAL intending to shift the old value into the next slot - that is, I end up with y1 shifting to y2 and the new value goes into y1. Then I calculate the area following the formula given above and add it to sum and set the output, OUT equal to sum. The problem in this case being that sum can't be added to.

There are probably other errors that I don't know about so I apologize for those in advance. Any help would be appreciated.


texts:
I am building a system to automate a vertical farm (specifically watering, lighting, and drying) and am having trouble choosing between a wired or wireless system architecture.

The farm is arranged into a vertical matrix of 'trays' (like drawers in a large cabinet - each tray has one specific type of crop) that is currently ~7x7. Each tray must be independently controlled.

Each tray will need two relays for two solenoid valves (source and drain) and feedback from a float switch for watering, plus an additional two relays for lighting and drying control - meaning 4 digital outputs and one digital input per tray.

The entire system will be controlled form a central computer. For the current farm this would entail 196 outputs and 49 inputs, but I want to design this system such that it can be scaled to any size.

So these are my questions:

For a wired network,

-Can I chain together a (theoretically) infinite number of shift registers to give me the required number of digital outputs to control these simple devises?

-Is there something similar to a shift register that can manage a large number of digital inputs and reduce the number of pins required on the computer board?

In General,

-Between a wired architecture (using something like an Arduino/raspberry pi with shift registers) and a wireless one (using something like a Zigbee mesh network to manage all the devises), will they both have similar reliability?

Thanks in advance!


texts: Legal requirement for measurement equipment calibration in manufacturing

texts:
We have a build approaching but one of our PSU's used in the function tester will be out of calibration in 3 weeks.  Most likely we will complete the build whilst the PSU is still within it's calibration date but if the build overruns there is a danger that the PSU will go out of calibration.

I can send the PSU for calibration now but this will delay the build or hope that we encounter no major issues and the build completes before the calibration expires.

Realistically, calibration is based on probability.  Calibrated now, so probably good for a year.

Extending a day or two past the calibration due date should not really adversely affect the test outcome but I am concerned about the legality.

Does anyone know what the legal impact obligation is during manufacturing with relation to the calibration date of test equipment?


texts:
I am trying to install recessed, dimmable LED lighting in the living room. We're talking about an end solution of maybe 15-20 spot lights. My home has 120V/60Hz.

Currently I am experimenting with a single spot light, a 4 x 1W warm white LED LemonBest 120V AC. Besides the main lamp the device has a small box which is labelled 'LED driver'.

I installed a Leviton slide dimmer in the wall and the spot light into its hole in the ceiling. There is functionality. The light can be turned on and dimmed.

However, the light that is produced has a flicker in it. It is especially noticeable when the light is dimmed. This flicker is not an option. I am trying to get rid of the flicker.

Since this is the 2nd dimmer I am trying I gave up on a solution a la 'just get the right dimmer'. This problem needs to be solved differently.

Measuring the output of the 'LED driver' results in 25V down to 15V DC depending on the setting of the dimmer. Now, I guess that the 'LED driver' contains a rectifier and a resistor. I further guess that the flicker is a result of voltage as a function of time which probably goes like in the image (the resistor is not shown). The LED has probably a minimum voltage that is needed for operation and on a frequency of 120Hz this minimum voltage is not provided. Thus, the flicker.

My question is: Is there an inexpensive, but still professional way to achieve a non-flickering LED light? E.g. would a capacitor added to the wiring at each lamp smoothen the voltage? Or is the only solution to add a 25V DC source to the wall and 'dimm' the DC current (and remove the 'LED driver' at each lamp)?

EDIT:

The LED lamps are designated as 'dimmable' and the dimmer slider I use is designated as for the use of LEDs. As I said, the lights are dimmable and for most use cases it's fine. But in a very ambient setting (low dimmer setting) and when uses as the only light source in the room, one notices the high frequency flicker. (If I fan my finger in front of a book page I see a stroboscope effect). This is annoying and I'd like to solve this before installing ~20 of these lights.

I opened the 'LED driver' and took 2 photos. See below. Not sure what the brown-ish thing is. A capacitor maybe?

EDIT:

And this is the lamp:

And the other side (with the LED driver connected):

For completeness the specs of the lamp (source Amazon):

Specifications:

Power: 4W(4x1W LEDs)
Input Voltage:AC 100-145V
Dimmable: Yes
Material: High Strength Aluminum
Color Temperature:Warm White(2800-3500K)
Luminous Flux:480-650LM
Beam Angle:45 degree
Life Span:50000 hours
LED Working Temperature:-25°C - +65°C
Size:D3.39*H1.65inch
Cut-out:2.68inch (68mm)

EDIT:

I looked up what a PWM is and it basically puts the signal periodically to zero on a high frequency simulating a 'dimming' effect. The signal would look like:

Thus for the dimmable LED lights to have the best result one needs to go for the highest frequency (or fast-acting) PWM. If the frequency is high one should not notice the flicker. But what would be high? As I see it, right now I guess my flicker is at 120 Hz and it is annoying. (Honestly I think it's at 60Hz but technically I can't explain 60Hz, so I say 120Hz, comes from the two zeros per sinus wave). Guessing I need a PWM at at least 240 Hz. Does this make sense?


texts: Formula for non - active power of capacitors connected in a star?

texts:
There is a common question in my coursework that we are asked to :
Let's say we have an inductive 3 - phase load that consumes $$S=15 + j10$$MVA
"If , we connect parallel to this load, 3 capacitors that form a star, compute the capacity of each in order to achieve, unit power factor.  "
I know, there is a formula that says $$Q_c = \omega*C*V^2$$ but I don't know the proof( we were just given the formula right away) and I am not able to identify if I am using it correctly.
If V, is the polar voltage ("line voltage" I think it is in English), then does this $$Q_c$$ represent the non - active power that the whole star produces?
So, I can say (??): $$C=\frac{Q_c^{3ph}}{\omega V^2}$$
What, would change if those capacitors were connected such as to form a triangle?


texts: Is there an insulation compound for exposed leads on a PCB?

texts: The top of the enclosure I am building is going to be the PCB. The PCB has a 7-segment LCD and the leads are somewhat exposed. Is there an insulation material I can brush on or squeeze on that will stick and cover the leads and prevent accidental shorts?


texts: DC component in an integrator circuit using opamp

texts:
While doing this project I ran into a problem.
We are using an opamp in a integrator circuit. However we noticed the existence of a DC component that only apears when the input frequency is high.
I think it is somewhat related to the capacitor being charged, and the opamp offset, but i'm not sure how it occurs.
Does anyone know why this happens?