texts: NAK in CAN when programming stm32f407vg uC

texts:
I am getting NAK error in CAN communication. Not really sure why, also frame itself is quite strange as in program I am sending different things. I have got two devices and therefore I monitor 4 logical pins:

Device first (first and second logical view) CAN1 Tx(1) and Rx(2)
Device second CAN2 Tx(3) and CAN2 Rx(4)

A screenshot from saleae of two frames is shown below:

First frame in zoom looks like:

It's the first frame in zoom. I get error as CAN2 keeps high state all the time.

Second frame (and all later) in zoom looks like:

The thing in last on CAN1 Tx is NAK and on CAN1 Rx and CAN2 Rx is ACK. In zoom:

what I want to do in fact is:

Run CAN at 100kB/s
CAN1 and 2 sends the same message (CAN2 in fact does not send anything as    CAN1 and CAN2 sends the same thing)
I want to send/receive 8 bytes of data(for the time being it can be anything)

And the code responsible for setting the CAN is :

CAN_InitTypeDef canInit;
RCC_APB1PeriphClockCmd(CAN_CLK, ENABLE); //enable clock

CAN_DeInit(CANx);

/* CAN cell init */
canInit.CAN_TTCM = DISABLE;
canInit.CAN_ABOM = DISABLE;
canInit.CAN_AWUM = DISABLE;
canInit.CAN_NART = DISABLE; //retransmission
canInit.CAN_RFLM = DISABLE;
canInit.CAN_TXFP = DISABLE;
canInit.CAN_Mode = CAN_Mode_Normal;
canInit.CAN_SJW = CAN_SJW_1tq;

/* CAN Baudrate = 100 kBps (CAN clocked at 42 MHz(168MHz / 4)) */
canInit.CAN_BS1 = CAN_BS1_11tq;
canInit.CAN_BS2 = CAN_BS2_8tq;
canInit.CAN_Prescaler = 21; // 42MHz/21 | 2MHz/(11+8+1)
CAN_Init(CANx, &canInit); //CANx == CAN2

/* CAN filter init */
CAN_FilterInitTypeDef  canFilterInit;
canFilterInit.CAN_FilterNumber = 0;
canFilterInit.CAN_FilterMode = CAN_FilterMode_IdMask;
canFilterInit.CAN_FilterScale = CAN_FilterScale_32bit;
canFilterInit.CAN_FilterIdHigh = 0x0000;
canFilterInit.CAN_FilterIdLow = 0x0000;
canFilterInit.CAN_FilterMaskIdHigh = 0x0000;
canFilterInit.CAN_FilterMaskIdLow = 0x0000;
canFilterInit.CAN_FilterFIFOAssignment = 0;
canFilterInit.CAN_FilterActivation = DISABLE; //do not use filter at all
CAN_FilterInit(&canFilterInit);

/* Enable FIFO 0 message pending Interrupt */
CAN_ITConfig(CANx, CAN_IT_FMP0, ENABLE);

Frame is as follows:

sendMessage.StdId = 0x7FF;
sendMessage.ExtId = 0x1FFFFFFF;
sendMessage.RTR = CAN_RTR_Data;
sendMessage.IDE = CAN_Id_Extended;
sendMessage.DLC = 8;

for(int dataByte=0; dataByte<8; dataByte++){
  sendMessage.Data[dataByte] = 0xFF;
}

strongDelay();

while(1){
    CAN_Transmit(CAN2, &sendMessage);
}

I do not know what kind of information should else be provided, but what I see:

Id is completely different from the one, that I want to send
Frame is interpreted as RTR, but should be as DATA frame
Some of the bits are wrong as you can see them crossed out in the program
Frequency is just like the one I wanted (so it's not random thing, that is being send)
It rather is not caused by noise in connections (pseudo analog view seems ok)
transciever and other stuff should be ok, because it was bought as ready to go CAN boards.

Any help would be apprecieated, as I am running out of ideas what should I change.


texts:
I am using a MOSFET to control the average voltage to a device by varying the duty cycle to the base as shown in the diagram below. My question is what is the best circuit to use in the "filter box" in order to "smooth" the PWM into its analogue equivalent. I have been told i can use a choke for this purpose, however is this the best approach.

Please note I want to smooth the PWM as the load is a peltier device and hence should not be driven by PWM. Further more there will be about 8A of current drawn by the peltier.


texts:
Suppose \$R_{1}\$ and \$R_{2}\$ are replaced by resistors of unknown values which are different from those assumed in part (a).

Using a variable external voltage source, a student applies \$+1.5V\$ between terminals a and b (a is positive relative to b) and measures a current \$i_{0}\$ of \$-0.1A\$. When the external voltage is \$+3V\$, the external voltage source  generates power and \$i_{0}\$ is \$+0.2A\$.

Recalculate the Thevenin voltage and  resistance in this case, assuming all  sources are ideal.

I am not sure how to approach this.


texts:
I hate to be asking this, but I just don't understand the operation. I've been reading various resources, mostly this: http://services.eng.uts.edu.au/~venkat/pe_html/ch07s1/ch07s1p1.htm though. From what I understand, when the voltage source is connected to the circuit, current flows through the circuit like so:

When this is happening, presumably the capacitor is being charged as well. But even at this point I seem to be misunderstanding: surely the load receives the input voltage as well? So even if you wanted the load to receive say 20V stepped down from 120V, when the source was connected at least, there would be 120V across it. Surely this could damage components rated for 20V? I suppose with PWM you could minimise the time that the load was exposed directly to the input voltage to negligible times, but I'm not sure. I'd just really appreciate it if someone could clear up my confusion about this.

In terms of general operation: one way I can think of the buck converter working is if the capacitor is charged to the 'Output' voltage and then the inductor is used to keep the capacitor near this voltage during the presumably much longer off cycles?


texts: Voltage drop, direction of current, extra voltage source

texts:
This is a branch from a network, and -40mA flowing through it (direction shown below). Textbook says the voltage drop on the 45 ohm resistor is -3.18V. But I don't understand it.
Do I need to add that extra 2 Volts from the extra source or substitute it?
So the question (in short): how do you calculate the -3.18V here exactly? (and why that way)

Full schematic from link provided by the OP in the comments:


texts:
As an exercise, I am trying to design an implementation of Conway's Game of Life in simple digital logic. I could do the whole thing by minimizing a 9-Variable function, but I imagine that will still be fairly large. One of the core elements of the algorithm is determining how many of your 8 neighbors are 'alive'.

Given 8 inputs, what is the easiest way to determine how many are set? Particularly I need an output that is high when 2 are set, and an output that is high when 3 are set.

My main idea now consists of a PISO shift register, a counter, and a 3:8 decoder, but I pretty much need a microcontroller to drive all of that. It does not seem like that complicated of a function. Maybe a 256x2 ROM would work as well, but my searches haven't turned up any of that kind of part.

I know that any pic with 10 IO could do this trivially, but I want to implement it in as minimal a way as reasonably possible.


texts: Looking for an inexpensive Smoke Detection Sensor

texts:
As the title says, I am looking for a smoke detection sensor. Took a look from SparkFun to Mouser and did not find anything. Is there a part you would recommend? I would prefer something that interfaces with the ATMEGA168/ATMEGA328 via a single wire or two wire interface. Would prefer to avoid a SPI or Serial interface as my circuit already utilizes those pins.

Bumped into a few sensors on Ebay but they were $15+. Is this normal? Is there a cheaper alternative that works great? Should I just buy a cheap smoke alarm and extract the sensor that way?

Thanks in advance for your help.


texts: How to decide about master or slave mode in I²S (I2S)?

texts:
Participants in I²S can be in master or slave mode. The master has to provide the clock and the slave has to accept the clock.

I would like to know how under what considerations this decision is made.


texts:
I have started to research about electrical motors and batteries.

I have learned physics in high school and I understand electricity. My question is whether an engine's power depends on its RPM or not. Let's say the specification says its 1V at 1 Amp, does it give me 1 watt at any operating RPM or a constant force, which gives 1 watt at maximal RPM? Maybe the resistance depends on RPM?

Because if it gives a constant force, the power is P=VF and I need gears if I want dynamic acceleration (like in cars, the acceleration starts high and is reduced with speed), and if the power is constant then the force starts high and is reduced, giving me optimal acceleration and force at any time. I think that its constant power, because electrical cars are single-speed (only one gear ratio). (contrary to internal combustion engines which its power varies by the RPM).


texts: I am just starting off with hobby electronics and can't get hold of the concept of Load. Do electrical appliances also "Draw" current. An air conditioner upon start dims the light. My point is that if the voltage difference is not enough to move whatever machinery is in there then the air conditioner should stay off or not work. How come it "draws" electricity upon start?


texts: Altium .CMPLib advantages over .SVNDBLib

texts: My team and I have been tasked with overhauling our library management system for components within our Altium Designer tool set. I am trying to understand the advantage (if any) of adopting the CMPLib paradigm over the SVNDBLib paradigm. We currently have most of our components in MSAccess databases or SQL databases in .DBLib format. As I understand it CMPLib allows for version control at the component level just as a SVNDBLib, however allows for a level of abstraction between a component and the associated Manufacturer Part Number and Supplier Part Number information. Can anyone elaborate on the advantage of this system over every component linking to a single MPN and SPN?


texts:
Using Xilinx, I need to compare a 'variable' called 'row', defined as:

variable row   : std_logic_vector(2 * n - 1 downto 0);

This line was given to me, now I need an if statement that will execute if row is = 1.

I have tried:

if (row = "1") then

but the IDE warns me that this condition will always result in false? which should not happen.

If I try if (row = '1') then or if (row = 1) then then I get the error:

found '0' definitions of operator "="

Googling this, the only suggestion is to include libraries that I have already included:

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;


texts: Any reliable site where *hardware* engineers can be hired for small (work-from-home/telecommute) projects?

texts:
For software hackers/developers there are many.

However, I need a hardware guy (or girl?) for a relatively small project.

Is there a site where I can search for people and see ranks, recommendation, etc.?


texts: Close range ultrasonic fluid proximity level sensor

texts:
I'm looking for a way to sense a fluid's level from above, in a small package, with a relatively low dead zone. Most commonly available ultrasonic sensors (which I would see as the best option) have dead zone's of at least 5 inches/13 cm like this one.

What I'm wondering is if that dead zone of around 13 cm comes from the IC's used in the package, or the physical limit of the transducer.

In the first case, are there packages out there that do overcome this, or would it be an option to purchase an individual transducer and hook it up to my own circuitry, optimized for a very low dead zone, and if so, any examples out there on how to go about building such a sensor out of a transducer?

OR

In the second case, are there any alternatives to a ultrasonic sensor that would help me achieve this goal? The liquid in the container or the container itself may in this application not be affected.


texts:
I have a VBus of 12VDC. I would like to take 14 discrete inputs and Light a single LED for each input that is active.

I was planning on just doing a simple current limiting resistor and having a common anode and allowing the inputs to switch ground.

A new requirement was added: If any of the inputs are active they want to switch on a 500mA load on. (ie a buzzer or light). I would most likely do this with a NFET.

I would like to try and do this as cheaply as possible.

If i use a micro then I need to generate 5v. I could probably do a micro / powersupply / and either optos or resistor divider for the inputs this would cost around $8.00 per board.

Can anyone suggest any easier / cheaper way to mux the LED inputs together?


texts: I am quite new, lets say green at this whole electrical game. Now that you know that, I have built a mini wind turbine that is powering a salvaged dc motor from a Kodak printer, and a green LED attached to the wires of the motor. The motor will turn on the led with a certain thrust of my fingers or if I roll the motors gear on the floor it will power the led, but wont turn the led on with a normal rotation of wind. I have a positive feeling that one of you could help me and I was wondering if there was anything I could run in between the dc motor and LED to keep a more constant flow of electricity rather than needing a high initial thrust. the led is powered by the other smaller motors I salvaged as well and this dc motor is about twice their size so I know there is more than enough potential to figure this out. Thanks to anyone of assistance. :)


texts: monitoring voltage and amperage on Raspberry Pi USB ports

texts:
Question:
Is there a way to get the Pi to tell me the instantaneous voltage and amperage on the USB port that I could write to a data file?
Why I am trying to do this:
I am trying to monitor rapidly changing Amperage and Voltage on my USB port of my Raspberry Pi 400, to understand what is happening when I am trying to poll all the devices on that port, and why not all of them are responding to the poll. I believe it might be power related, and if I can determine that, I might be able to find a way to spread the power demand, or provide auxiliary power to an underpowered USB device. This problem is described in more detail in a separate Stack Exchange post.
Effort to date:
I put a USB multimeter in stream on that port and I can see it change rapidly.  I am currently filming the changing display and then keying in the data to a spreadsheet for analysis and graphing.  But this is really tedious and error prone.
My meter doesn't record or log these changes, so I can't get it to provide me an automatic list,  but I know that using the gpiozero library I can get the pi to access the values of gpio pins and write them to a data file.
Is there a way to get the Pi to tell me the instantaneous voltage and amperage on the USB ports itself that it could write to a data file?


texts:
I am designing a board based on the Atmega328P microcontroller. For this controller there is an ISP connector for programming.
This connector has the following pins: MOSI / MISO / RST / SCK.

There is a task to protect this tire from electrostatic discharges.

To protect IO / I2C / UART, I use NUP4114.

Scheme:

It is designed to protect several IOs simultaneously.

Question: Is using the NUP4144 in the circuit above suitable for ISP / SPI line?


texts: How to package an ultrasonic transducer so it can be submerged?

texts:
I'm looking for a way to package an ultrasonic transducer without losing too much power in the process, which will also be an easy to make it so my transducer can be submerged.

My system is supposed to produce audible sound from the non linear interaction of ultrasonic waves in the medium (air/water), so power consumption is critical.

Any suggestions or known ways to do so?


texts: Driving 48 LEDs with 1 Single Current Source

texts:
I need to drive 48 UV LEDs for UV paint curing system. (LED: 3.5V, 20mA)

I found a simple current source, modified it, set the current to 20mA. The voltage on 3 leds is 10.50V (3 x 3.5V, exactly what I need).

When I add another 3 LEDs in parallel to existing 3 (having 6 LEDs total), the current stays same but the voltage across each line drops slightly. When I finally have 18 LEDs (6 parallel lines), the current was still ~20mA but the voltage across each parallel line dropped to 9.5V. Somehow it must be okey for the LEDs because they did not lose their brightness.

My questions;

When I finally add all 48 LEDs current source will keep the current at 20mA and the voltage will drop more. Will that drop on the voltage be OK for the LEDs?
Adding new LEDs does not change the current drawn from the power source, so is safe to drive 48 LEDs with one single current source or it will burn down things (LEDs, transistor or power supply) in long run?

simulate this circuit – Schematic created using CircuitLab


texts:
EDIT: I ran an i2c bus scanning program and it detected a device at 0x70 (the mux).   I connected the device I am trying to interface with directly to the i2c bus and ran this code and it worked exactly as expected.   But still when I run this code with the device attached to one of the mux channels, it does not work.   I'm stumped!

I am trying to control an I²C device via a multiplexer on an ESP8266.   Below is the circuit I'm using and the code. This exact code works if I change the device to be connected directly to SDA and SCL (bypassing the multiplexer). Unfortunately, if connected via the multiplexer, the code outputs "No TCS34725 found." I have tried this on two distinct boards with the same results on both.

Multiplexer datasheet

Reset (N$5) is pulled up to 3.3v via a 10k resistor.

#include <Wire.h>

#include <Adafruit_TCS34725.h>

#define TCAADDR 0x70

uint16_t clear, red, green, blue;

Adafruit_TCS34725 tcs = Adafruit_TCS34725(TCS34725_INTEGRATIONTIME_2_4MS, TCS34725_GAIN_1X);

void setup() {

  Wire.begin();
  Serial.begin(115200);
  delay(10);
  Serial.println("\r\n");

   tcaselect(6);
  if (tcs.begin()) {
    Serial.println("Found sensor");
  } else {
    Serial.println("No TCS34725 found ... check your connections");
    while (1); // halt!
  }
}

void tcaselect(uint8_t i) {
  if (i > 7) return;

  Wire.beginTransmission(TCAADDR);
  Wire.write(1 << i);
  Wire.endTransmission();
}

Any ideas on why this isn't working?


texts: Bluetooth 4 and Wifi direct chip development board

texts:
I'm trying to create a device which uses bluetooth 4 or Wifi Direct to send gyroscope readings from my device to a PC.

I know nothing of bluetooth and wifi chips and protocols, but I was thinking of using a Broadcom BCM4330 chip, yet I can't find any development boards or any way to purchase the chip so I can test it.

What would you recommend I buy in order to make a prototype device with a bluetooth chip, and a USB receiver dongle for the PC? Could you guide me in the right direction to learn more about these things?


texts: Charging capacitor in parallel and discharging in series

texts:
I wanted to use multiple capacitors to step up the voltage in a circuit. A little bit of google searching told me that it is called a Charge Pump. I figured out the charging each capacitor individually in parallel and then discharging them in series should result in the same capacitance and same voltage. Since charging capacitor in parallel will allow each capacitor to charge upto its rated capacitance(ideally!) and then discharging in series will add their voltages to give me Higher voltage without having to bargain with capacitance. Also I found there is a circuit called Marx Generator which uses the same principal,

Q1) Is my understanding correct? (which I think is)

Now If my understanding happens to be correct, I take four 50 volt capacitors and put them in series after charging them in parallel at say 36 volts. Then the output voltage from the capacitors should be approximately $$36v*4=144 v$$ .

Q2) Will the overall voltage damage the capacitors as it exceeds their individual ratings? (which I don't think will happen, but obviously need some experts help)

Now if I connect this output to two 200 volt capacitors in parallel and then put them in series. The resultant voltage should be 288 volts. Same as above followed and in theory I should end up with 288 volts approximately.

Q3) I think I have the circuit figured out but it will use a lot of switches to change the capacitor from parallel to series, Do you guys have a better way to do so?


texts: Can you safely use the telephone during a lightning storm?

texts:
Everyone's heard the lecture on how you shouldn't use the telephone in a storm unless it's an emergency, due to a risk of electrical shock. My understanding is this is true and numerous people have died from lightning striking the telephone wires and electrocuting telephone users. Most reports say lightning enters through one's ear.

How exactly would this work? Most telephone receivers are plastic and plastic does not conduct electricity as well as metal or water. The copper wire from the PSTN connects to the telephone, but the only part of the telephone that you would touch is made out of plastic.

So how exactly can using the telephone be dangerous? Can lightning travel into the plastic part of a receiver and through the air into someone's ear? Is there a way to be safe when using a landline telephone or prevent this from happening?

For example, if you have a speakerphone connected to the line, does that reduce the risk? If you hold the receiver away from your ear, are you safe? If you put metal or water near the telephone, will the lightning strike that instead of your ear?

*If you haven't figured it out, I'm talking about normal landline telephones, not the crazy alternatives that people try using nowadays.


texts:
I have a Panasonic PIR sensor (EKMC1603111) and am measuring the voltage between the output pin and ground pin.

On the green multimeter I read 0v when there is no motion and 3.3v when there is motion (as expected)
On my new yellow multimeter I read 3.05v when there is no motion and 3.3v when there is motion.

The yellow multimeter has auto-range, the green multimeter does not. To prevent other factors I left the ends of the leads clamped to the PIR sensor and just plugged the leads out off one multimeter and then into the other. The results with different PIR sensors and different (3.3v and 5v) power sources were the same.
Possibly related: I started this debugging process because I connect the PIR sensor to a Wemos D1 Mini board and the GPIO input put read a constant digital HIGH. This was unexpected behavior but made more sense when I measured that the sensor only switches between 3v en 3.3v during motion. It did not make sense anymore when the green multimeter did show it switches between 0v and 3.3v during motion.
Is one of the multimeters wrong? Is it phantom voltage? Is it related to the permanent digital high reading by the ESP8266 board's digital input pin?


texts: Trouble with instrumentation and simulation of the common-mode response of a filter

texts:
I have been struggling to obtain the Bode plot of common-mode response of a filter. I first simulated it using LTspice, then I used a USB network analyzer. Both do not match each other and to the given plot of the filter.

Here is the general datasheet of the filter. The specific model I have is called FN2060-10-06. Below is the components parameters for this model:

[left-click to view larger]

And below shows the circuit diagram of this filter and the frequency response plots:

First I want to show how I simulated this circuit in LTspice and what Bode plots I have obtained:

Secondly, I used a USB network analyzer where it has the following pin-outs:

Above 1+ and 1- are differential input terminals for channel 1;  2+ and 2- are differential input terminals for channel 2. W1 is one of the signal generator output.

So I set Ch1 as the reference channel using this software and made the wiring between the filter and this USB network analyzer as below where 220 Ohm is to limit the current:

And the network analyzer plotted the following between 1Hz to 30 MegHz:

[left-click to view larger]

So something I'm doing is not correct because neither the simulation nor the network analyzer results do not match the datasheet at all. All I wanted was to find a simple method to obtain the common mode response of this filter. Does anybody have experience with such setup? If wrong, how can I correct the simulation and/or the network analyzer setup?


texts: Quick simple car lighting circuit question

texts:
I have wired up the below circuit in my car and would just like to ask if there are any issues with this circuit.
The lighting in this circuit is tapped into three wires from the car's ceiling light. These three wires are as follows:

+12v feed
GND constant
GND only when car doors open

The front LEDs are functioning properly whether the switch is set to "GND constant" or "GND only when doors open."
But the right and left side LEDs are not functioning at all. I have them wired into "GND only when doors open" as I do not want them constantly on and only want them to come on when a car door is open.

Thank you so much for looking and I appreciate any help.


texts: Is it important to keep components and traces on a PCB aligned to a grid?

texts: As in the title. I've just noticed in one of my PCB designs the components are not aligned to a grid and neither are the traces. It passes DRC, but I'm wondering if it will cause further problems. I'll be using standard PCB houses like PCBcart, SeeedStudio etc.


texts: Which kind of component uses an "EM" symbol prefix, has a value, and three pins?

texts:
While perusing the schematic for the Sega Genesis model 2, I spotted these "EM1", "EM2", etc. components near the joystick inputs and video/audio outputs.

Looking at a photograph of the board, the components themselves remind me of the older-style package for inductors, though it's a little hard to tell what's going on from above:

The same schematic also has several inductors, all using the usual "L" symbol prefix.  (L2 is visible in the photo.)  So these "EM" parts are presumably something different.  The prefix itself suggests something like a ferrite bead, but do those usually have a value ("101" in the schematic) associated with them?
Worst of all: they're labeled as using pins 1 and 3 (where some unused pin 2 can just barely be made out under EM3 in the photograph) and I've never heard of a triple pin ferrite bead.
I can imagine they're almost certainly for some sort of protection or isolation or filtering, but I haven't been able to find anything about the symbol prefix or the components themselves.  Could someone please help shed some light?  Thanks!


texts: How temperature difference does not affect transistors in CPUs?

texts:
Recently I learned about semi-conductors and some devices.
Today I watched a video on youtube about a guy overclocking a cpu to 7.0 ghz, while cooling it with liquid nitrogen to -192 celsius degrees. This range of temperatures is vast and iam having a difficulty to understand how the silicon does not reach freeze out zone and does not act like an insulator, or when reaching high temperatures (for example in gaming) the thermal generation does not mess things up and crash the whole system.
For example if the thermal generation was high on a ( in a MOS transistor) will it cause free charges to pass through the pipe and turn it from 0 to 1 even though we are still in low voltage (V gate < V threshold) ..?
How do they overcome those things?
Thank you very much in advance.


texts: Unable to enter in Programming mode (AT_Studio)

texts:
I've a board with the SAML21E17B uC, when I want to connect/ program it  using JLink(edu) and Atmel Studio I get and error message, that the IDE is unable to enter the programming mode

any idea what's the problem and how may I solve it ?

UPDATE

after Wossname answer I've resoldered the uC and double chekced the board, and could find and shortcut, and I still can get an access to the board , here's the part of schematic where the programmer  is connected, maybe I've made a mistake here :

and yes I've place the capacitor and the induktivity near to uC as mentioned in the datasheet.  And I've also set the programmer frequency to 32khz


texts: How to mount the PCB in a watertight die cast aluminium enclosure?

texts:
I would like to know how to secure the PCB into a watertight die cast aluminium enclosure that has no visible mounting posts. There are plenty of those on the Hammond website, and I don't understand how they are meant to be used.

It has to be IP65, and reasonably vibration resistant for mounting on top of a high tower, and resist about -10°C to 75°C inside.

An example is the Hammond 1590W Series.


texts: How can electromagnetic interference from a USB charger cause a capacitive touchscreen to malfunction?

texts:
Electromagnetic interference from a USB charger can cause a touchscreen on a mobile device to malfunction, with symptoms such as reduced sensitivity or spurious touches. As an example, see http://forum.xda-developers.com/showthread.php?t=1784773.

From an electrical standpoint, how can EMI from a USB charger cause a capacitive touchscreen to malfunction? I can understand how EMI can cause radio communications to fail, but I don't understand how it would cause a touchscreen to malfunction.


texts: Inconsistent behavior from circuit on breadboard

texts: Recently I started building circuits on bread boards.  Nothing advanced, mostly stuff like full adders, ripple counter, etc.  I am noticing some interesting behavior from the circuit though.  I'll get different behavior from my circuit without changing any of the circuitry.  For example I built a ripple counter with a 555 timer the other day and it was working fine.  Today when I turned it on it wasn't working the same (all the LEDS were lit up at the same time).  I turned the power supply on and off a couple of times and pushed all the pieces firmly into place and it started working the way I wanted again.  What I am wondering is what may cause this?  Is it common for circuits to require fiddling with to get them working (even when they were working previously and you didn't change any of the circuity)?  All the parts I bought were the cheapest ones I could find on Ebay so I am wondering if maybe my breadboard or ICs have problems.  Is there any way to check that?


texts: How to properly use ESD protection wristbands

texts:
I've looked at other articles on EE stack exchange about ESD precautions.

I would like to use a wristband for precaution with microcontrollers. Where am I grounding my wristband to?

Do I ground myself to the table I am working on? Or do I ground myself to the ground of the circuit I am building?

I seen in To avoid ESD when you are working on computers, what should you attach your wristband to? the answer explains to ground to the table. Should the circuit, table and myself share the same potential?


texts: How do I add STM32F4 support to GDB client for watchpoints?

texts: I have been trying to debug my code and realized that my watchpoints for variable never execute.  When I looked into this problem online, I encountered similar situations and the response they received was their microcontroller may not be supported.  I have an STM32F4 and I am using GDB on Ubuntu with st-util.  Breakpoints currently work but watchpoints don't.  How can I add support for it?


texts: What are the files types used for Xilinx Vivado simulation

texts:
I see lots of files, not all of which have obvious purpose.

Where is a list of file types, especially those for simulation?
Specifically, what are these files for?
Which needs to be in source
control, and which are outputs? Specifically which might I edit and
which are created by the tools?

Specific files in question are:

.dir
.pb
.ini

I have asked Xilinx on their forums here and will put anything I hear back as an answer.


texts: what is the difference between D and D/L flip-flops?

texts:
I'm trying to understand how a DDR receive circuit works. I'm reading the MachXO2 Family Data Sheet, page 22:

http://www.latticesemi.com/view_document?document_id=38834

What I don't get is this: there are some flip-flops labeled D and some labeled D/L. What difference is the document trying to indicate by labeling some of them D and others D/L?


texts: Testing the accuracy of a PLC current input module - economical approach?

texts:
I don’t want to suggest a particular brand or model so to discourage a good universal approach. But let’s say the DUT here would be your typical industrial PLC module, a typical 4-20mA SAR ADC based, single-input/common ground module.
My plan so far is to find a tight tolerance set of resistors to test the current reported against a “known” current. I will only use resistors no better than the level of uncertainty documented in the module specifications when factoring gain and range error. If I go about it this way, my plan would be to deduct the observed (added) resistance from the resistors that these modules typically use on their channels (~150 ohm) that create the input voltage going into their mux. Is this a good approach, or are there better ways for reasonably cheap?
Thanks


texts: Why Trickle Charge a Deeply Depleted Li-Ion Battery?

texts:
I'm looking a this to write my own charging algorithm (really not looking to re-invent the wheel here) and have been referencing this article: http://powerelectronics.com/site-files/powerelectronics.com/files/archive/powerelectronics.com/mag/504PET23.pdf

It'd be easier in this situation if I just jump straight to stage 2, constant-current charging at 0.2/h*C to 0.7/h*C which makes me wonder just how important that first stage is and what its purpose is in terms of the battery chemistry.


texts: Why does shorting/putting heavy load on a motor slow it/stop it?

texts:
I am doing a simple circuit which includes using a motor in theory (I am using a stepper-motor) as a break. One of the random fun-facts that I have known for a long time is how shorting a stepper motor (or putting very high load ) will cause high current and slower rotation (or sometimes stopping rotations all together).

However I do not understand how it works from an electrical/electromagnetic point of view. Where does that force come from?


texts: Why do MCU crystal oscillators not fry the crystals?

texts:
I am trying to better understand crystal oscillators. I have been reading ST's AN2867, where they explain that, depending on the crystal, a series resistor (R2 in the diagram below) on the output side should be included to limit the current through the crystal.

This resistor is not something I have seen in most circuits I have encountered. Usually, the crystal, properly loaded, is just directly connected to the oscillator.

So I fired up a simulation, to try and get a feeling for what effects this resistor really has. I modelled the crystal with the usual lumped elements.
(I did not choose the values for a specific crystal, I just chose round values, such that the overall performance reasonably matches real-world 8MHz crystals.)

The source V1 has an amplitude of 2.5V, which I assume is reasonable for a 5V CMOS oscillator (is it not?). R2 is swept from 100 Ohm to 10 kOhm by factors of 2.

Top panel shows the current sourced by the oscillator. Middle panel is the power through R1, which (I think) should match the power dissipated in the crystal.

What's bothering me is the fact that unless R2 is chosen fairly high (>5k) the power can easily exceed the safe drive level of SMD crystals (100 uW).

At the same time, section 3.5.3 of the app note above suggests that you cannot increase R2 past ~100x R1 without exhausting the gain margin (for the ST oscillators with a transconducatnce of ~10mA/V).

EDIT: (new) The bottom panel shows the phase at the Vout node. @andy-aka mentioned in the comments that the actual oscillations (if any) will occur at the frequency where this phase shift is 180°, which is marked by the solid black line.   Clearly, this intercept occurs very close to the parallel resonance frequency (as I should have known). Here the power dissipated in R1 is much lower than at the peak value, but it can still be significant.

What am I missing here? Why do so many circuits omit R2 completely (or choose a low value, <1k), yet do not fry the crystal? For instance in the AVR datasheets, Atmel never mentioned such a resistor. The ST Discovery boards sometimes include a 390 Ohm resistor, sometimes none at all.

Is the output resistance of the inverter sufficient? How can one design for this, other than trial and error?

If it is really that hard to gauge correctly, why don't manufacturers provide better guidance?

I have read many other posts on this site. Two questions in particular are focussed on the series resistor of oscillator circuits. This one focusses on 32 kHz crystals, which are a very different can of worms.
'Selecting a damping resistor for crystal oscillator circuit' has some very interesting answers, but does not address my point of why we see the resistors omitted so often.
Please reconsider before marking this as duplicate of either one.


texts: which type of motor is best choice for rotating screw with 1 deg accuracy and under 1kgfcm torque?

texts:
I'd like to apply electric motor with small size.

My application is rotating screw with 1 deg accuracy and under 1kgfcm torque.

Which type of motor is best choice?


texts: What is the need to do a dV/dI measurement instead of numerical differentiation?

texts: In the semiconductor industry many measurements are performed as dV/dI versus applied voltage V. Here, dV/dI donates a differential resistance measurement. What I do not understand is the need for such measurements while you can always do a numerical differentiation of standard V-I measurement. So what am I missing?


texts: why output of RC low pass filter is ramping up when square wave is applied?

texts:
Why am I getting ramping-up voltage at the output of the given circuit below? I should be getting saw-tooth waves right. What am I missing?

Output waveforms are like these in LTSpice!

Did I chose a wrong value or set wrong transition period?


texts: Trickle charging a Li battery from motorcycle battery?

texts:
Sorry if this doesn't belong in the forum, however I'm unsure of where to start and am rather clueless with electronics, but keen to learn more.

Essentially I would like to charge this GPS device from a Motorcycle battery such as this, without it draining flat between rides, or draining the bike battery. It can be wired in so it charges only while the engine is running or all the time.

Charging while bike is running:

How long would it last off the internal battery?
Would it be possible to include an additional mobile battery to increase capacity?

Wired into the motorcycle battery:

How long would it roughly take to drain the motorcycle battery?
Would it be possible to trickle charge? If so how?

Device Details

All the details I can find for the GPS device are:

Internal Battery: 3.7V 500mAh Polymer Li-Battery
Charging Consumption: 100 mA
General Consumption: 50 mA

Motorcycle battery capacity

3Ah

All and any advice is very much appreciated!


texts: Understanding PCB footprint for ESD321DPYR

texts:
Looking at the datasheet for component ESD321DPYR, the PCB footprint looks something like this (copy and paste from page 16):

However, the footprint I downloaded from Library Loader here, a trusted and reputable website is quite different and looks like this:

The pins in the footprint they provided extend way beyond the outline and appear too big. I also compared against Library Expert Pro to confirm (based on dimensions I inputted from the TI datasheet) and it looks similar to the TI datasheet not the footprint supplied by Library Loader. I'm a novice at this so not sure if I'm missing something or misunderstanding things. I did send an email about this to SamacSys, the company behind Library Loader. Any help is appreciated!

UPDATES/ADDITIONS:

Thanks all for the info. I guess I didn’t make the distinction that the “mechanical data” section is sperate and has a different purpose from the “land  pattern” data section. I’ve uploaded annotated images to get some clarity.

If I understand correctly, the mechanical data provide dimensions for the IC package itself and the pins on the IC. While the land pattern data provide info for the PCB pads. Is this  correct?
In the first new image I just added, is it correct that the arrows point to the pads and the outer perimeter of the package? Is this outer perimeter supposed to match the 1.1x0.7 size in the second new image attached, from the mechanical data section?
In the second new image attached, the arrows in red point to the pins and not the pads? The distance between the center of the pins is max of 0.7, while the pins are max size of 0.3 by 0.55? The outer package perimeter has a max size of 1.1x 0.7?
In the third new image, the arrows point to the pads , which have size of 0.6x0.5 and center to center spacing of 1?

Thanks!


texts: I have a problem again with an Arduino Mega 2560 board (SainSmart). The IDE gets stuck at the "Uploading to I/O board..." message. The bargraph shows around 95% but then there is no further progress. I tried this with Windows 7 64bit and Win XP, with 101 and 0023. Uploading is impossible. Board type and COM port are correctly set in the IDE. Any ideas to solve the problem?


texts:
I know that thumb wheel potentiometers are an outdated technology, everything is moving to rotary encoders. The problem I have is that my company has a large number of legacy products. We have designed rotary encoders into most of our designs but have a few very low volume products that wouldn't be worth a complete redesign. Here is the datasheet for the component currently used(its the 3rd on the datasheet). If anyone knows where to find something similar that would be great. I am also open to other alternatives and ideas anyone may have that would not require a complete redesign. I would like to simply be able to just update the footprint on the PCB to fit a new potentiometer

Note: I proposed the possibility of a knob protruding from the side of the product to control volume but that idea didn't go over very well, the thumb wheel is preferred.

Note: some specs are 10k, single turn, about 12.7mm (0.5") diameter

Discontinuation Notice


texts: Why is the 2.2k resistor needed in an MT3608 module?

texts:
I am trying to implement an MT3608 module on my PCB. I went through its schematic which clearly describes the module.
I see they have used 2.2k ohm resistor in addition to a potentiometer. From what I read in datasheet of MT3608 is that it needs 0.6V on the FB pin. There voltage divider for that. I don't understand why there is an extra 2.2k resistor used in the module. Is it for safety? Does anyone know the reason for that resistor?
Also I am planning to use a fixed value resistor (no potentiometer) as my output voltage is fixed to 12V.
Do I have to consider this extra resistor ?
Does nyone know a locally available resistor combination that gives R1/R2 ratio 19? I need it for 12V output.


texts:
I have a project that requires me to control a set of relays (up-to 24 of them). The current setup is using Wago Speedway 767 field-bus modules. I'm just ramping up so I have to either figure out how to communicate with the Wgo modules or I need to find a better alternative.

The Wago modules are really nice, but overly complex for this project. I was hoping for something that I could control via USB or Ethernet since I'm controlling everything with a Raspberry Pi and are limited on GPIO's. The relays will run 24v AC. The benefit of using the Wago was that you didn't need 24 individual signal wires coming from the controller to get the job done.

What is the simplest alternative to the Wago setup that will accomplish what I need to do?


texts: Where are the tutorial files for ISE WebPack?

texts:
I've been trying to learn to use the ISE WebPack and the link they give in their documentation( http://bit.ly/fsy8iD page 11) points to http://www.xilinx.com/support/documentation/dt_ise12-3_tutorials.htm

On that page I do not see any zip files or any tutorial files at all except for PDF files. Where do you get these files?


texts: What can be the cause for the servo to jitter continuously while powered?

texts:
I'm using an HS-785HB servo (https://www.robotshop.com/media/files/pdf/hs-785hb.pdf) for my project.

I'm working on the Mbed platform and it uses C++.

The servo library I use is Servo.h and I'm programming an STM32 microcontroller.

The issue I'm facing is that the servo keeps jittering while it is been powered. I'm supplying 6V to the servo from a relay and my application requires to not turn off the relay until the process is complete, i.e. I need to continuously power my servo so it can hold onto its position.

The command I use is Servo.Enable(position, speed) and Servo.SetPosition(position, speed).

There are a total of 3 servos in my project and all the 3 servos have shown jittering. I have also tried to connect a capacitor across its power lines if that could rectify the noise AC signals from the DC supply, however, this method didn't prove effective.

What can I do to resolve this issue?

Update:

I just discovered that due to a stepper motor, I was having those jitters in the servo. To confirm this, I disconnected the Stepper power line to the driver and ran the machine, the servos worked without any jitter. But I still don't understand how or why would this happen? The stepper runs from a separate 24V SMPS and the servos run from a different 12V SMPS w/ DC-DC Converter.


texts: Basics of battery charging and discharging

texts:
I am trying to understand batteries.

1) If I have a rechargable battery of 1.2 V 1000mAh, it means I can draw 1A at 1.2 V for one hour and the battery is said to be discharged ? Does "discharged" mean 0 volts and so I can't draw anymore current from it ?

2) Can I recharge this battery by simply applying a constant voltage of 1.2 V across it terminals ? Or it should be charged by some constant current ?

3) Can the battery be considered fully charged, right when its voltage reaches 1.2 V ?

4) What differentiates a non-ideal battery from ideal battery in these cases ?

I don't know whether there is a generic theoretical answer to these. If there is, it would be helpful.


texts: How to properly layout an external antenna seating and on board antenna at the same time?

texts:
I want my board to have the ability to opt for either an onboard antenna or an external one, with a 0R chip resistor, naturally.

This is my initial setup:

But then I am told that this is flawed and better go with this one:

You see, 2 & 3 should connect together and with 2 and if I had to go for onboard antenna, I need to solder the 0R at 0R in the picture, and at the same time, a capacitor in the CAP footprint shown in the pic, in order to avoid interference. You see if I keep the seating soldered on the antenna track at all time, like picture 1, the antenna is actually emitting, in other words, I will have two competing feeds (I hope the terminologies are correct), and I have to say that I agree.

Problem is, is the 2nd pic overthinking? Isn't two "de facto" antennas better than one?


texts: I would like to make a PCB that sends a specific byte of information through a usb connection. I need the PCB to be as small and simple as possible to fit into a nice thin housing. Simply put there would be a push button that would send a byte of information identifying it had been pushed, without a micro-controller. Is there a way to specify a sequence of on-off 1-0 within the circuitry on the PCB? namely a byte. I've searched EVERYWHERE and haven't found anything relevant.


texts: Interleaving in litz wire transformer - to be or not to be?

texts:
i am designing a transformer for 2-switch forward converter. For now, primary is wound as 5 wires of 0,5mm diameter (34 turns, 3 layers), the secondary is wound as 3 wires of 1,32mm diameter (17 turns, 2 layers). The frequency of smps is 83khz. The idea is to use litz wire in primary and secondary and increase frequency to 100khz.
So, the primary would be wound as litz wire (0,1mm diameter, 120 strands) in 2 layers. The secondary would be litz too (0,071mm diameter, 1076 strands) in 2 layers too. So, the skin effect must be elliminated completely. But what about a coupling? I have read a lot of books on winding interleaving technique, but all the cases if wire radius is more or less greater than the skin depth.
So, it is easy to do interleaving on this litz wire transformer (1 layer primary, 1 layer secondary, 2 layer primary, 2 layer secondary). So guys, will it worth it? I hope there must be some benefits like increased coupling between windings and reduced proximity losses... But i am not sure about that.
So - is it good idea to use winding interleaving on litz wire windings? Will i get better coupling between windings and decreased leakage inductance?
Thanks for your response. It is easy to do interleaving, but harder than just wound windings as 1P,2P,1S,2S.
I will post results of my experiments most likely.


texts:
I'd like to better understand how to calculate the voltage drop between the Drain and the Source of a FET.

As an example, say we have a MDD1902 N-channel FET. How would I determine the maximum voltage drop that can occur over Vds if the max drain current is 5A, max temperature is 75C, and Vgs is typically 12V?


texts: Beginner 8051 microcontroller kit recommendation?

texts:
I'm reposting this from stackoverflow, as the question is better suited here.

I'm a first year Computer Science student looking to get started with development for micro-controllers. I'd like to use the 8051, as it's common as dirt, and is used frequently in the real world.

During my junior or senior year, I'll be taking a PIC micro-controller based embedded design class, so I'd rather not do PIC now; otherwise, I'll be fairly bored during that course.

Most commercial kits I see are for the AVR or PIC series of microprocessors. I'm just looking for something with decent development tools, documentation, and enough add-ons to keep my novice self occupied for the summer.

Any recommendations for an 8051 family kit? Thanks!

I should have added, that I'd like to keep the price at $150 or less ideally. I'm pretty much just looking to learn -- not do anything too serious. I'm looking for more of a projects based kit.

UPDATE:

I ended up going with a SiLabs MCUNIVERSITY Kit, on recommendation from svec on stackoverflow. The tools and documentation look superb; there are also a set of exercises and labs. Plus, for less than $50, it's an excellent price. Thanks everyone.


texts:
I have a project that I've been thinking about for a little while, and I've come to the realization that at some point during its development, I'm going to need an oscilloscope. Okay, not a problem.

Instead of purchasing an oscilloscope, I've decided that I'd like to -- at the very least -- design my own, and hopefully build the result. To make things simpler, I'm thinking about using a Raspberry Pi to do all the fun calculations and visualizations (I don't feel like implementing the FFT on an AVR, thank you very much).

The more I read about oscilloscopes, the more confused I am, to be honest. Why isn't an oscilloscope just an ADC? If I were to hook up something like this (with appropriate over-voltage protection and pre-amplification) to a circuit on one end, and an appropriately-programmed CPU on the other, wouldn't that be an oscilloscope?

[In the past I've only worked with simple digital circuits -- I'm mainly a theoretical computer scientist! -- and so I'm trying to wrap my head around analog electronics right now. As such, I apologize if the answer to this is extremely obvious...]


texts: how to regulate parallel port pin output voltage to 5V

texts:
simulate this circuit – Schematic created using CircuitLab

Parallel port ideally gives TTL logic 0(low) and 5V (high). But my port gives 3.3V high. I have designed my controlcircuit assuming the high to be 5V? Is there a way to regulate the 3.3V to 5.0V so that I can still use the existing control circuit?

thanks in advance


texts: Why are capacitors with large values are manufactured polarized?

texts:
I couldn't find a duplicate-like of this question. I'm also not sure whether this is an electrical engineering question or a physics question.

As most of you noticed when one needs to use larger capacitor values the type of capacitors available to use are polarized capacitors such as tantalum or electrolytic capacitors.

What is the relation between large capacitance and being manufactured polarized?
is that the same reason: if we ask why are capacitors with small values are manufactured non-polarized?


texts: Relay Specification regarding switching speed

texts:
Newbie here, just wanted to ask some clarification regarding reading datasheet since i don't quite find a standard way to determine switching speed. I already had surf and the closest one was the question by Glavić What does CPM unit mean in relay specification?. This means its maximum operation is 1 cycle every 10 seconds.

I have a school project where I need my relay to have a switching frequency of at least 1 cycle a second and my current relay that i have is this: https://www.digikey.com.au/products/en?keywords=alf1p05. Upon reading its datasheet, i find a max. operating speed 20 times/minutes (does this mean 1 time = 1 cycle = 1 on & off operation?? meaning 1 cycle every 3 seconds?)

then i find this other relay https://media.digikey.com/pdf/Data%20Sheets/Panasonic%20Electric%20Works%20PDFs/jm.pdf having a max.operating speed of 180cpm. (does this mean 180 on & off operation every minute? 1 cycle every 33ms?)

I hope you can help me at least understand this one clearly, sorry if I'm somewhat indecisive with this one.

edited: i canvas all relays on digikey, mouser, etc and every relay detasheet don't have this 'max.operating speed' spec info like this one https://www.mouser.com/ds/2/418/NG_DS_RT1_1014-729126.pdf, how can i determine the speed of this relay or other relays w/o relying on the max.operating speed spec info?


texts:
I am trying to connect my PIC to RTC. The RTC I am using is DS1302 with only one pin for both (Input and Output). I am trying to simulate it using PROTEUS. The problem I am facing is how can I connect PIC two pins i.e. SDO and SDI to one pin (I/O) of RTC?

ScreenShot is here

Edit: I Have read the datasheet of 16fxxxx and couldn't find the configuration for 3 wire system.


texts: PCM1789 DAC direct connection to TPA6138A2 headphone amplifier?

texts:
Is it possible to directly connect PCM1789 DAC to TPA6138A2 headphone amplifier?

According to datasheet PCM1789 output are differential outputs and the input of TPA6138A2 is also differential inputs. The PCM1789 datasheet suggest putting LPF/Differential to single ended circuit. I wanted to know whether this LPF/Differential to single ended circuit can be avoided and make a direct connection.

It's my first time for all this so I needed some guidance.

pcm1789: http://www.ti.com/lit/ds/symlink/pcm1789.pdf
tpa6138a2: http://www.ti.com/lit/ds/symlink/tpa6138a2.pdf


texts: Good volts and amps but phone still charging slowly

texts: I am really new to the EE game and am still tinkering. I have built my own portable DC power source similar to a Minty Boost from scratch and plugged it into the USB port of my Galaxy S3 and it charges the phone but soooo slowly. I measured 5.02V DC and 650mA on the output, but the charge rate is abysmal and it nearly depletes the minty boost. Any thoughts as to why the charge rate is so bad?  Should I check the power quality with an oscilloscope? What am I missing?


texts: Is it possible to power AVR micro project with just one coin cell battery?

texts:
My current project setup is:

ATmega328P micro with 32 LEDS driven by 4 8-bit shift registers.

System without LEDs draws 20mA of current continuously. With all LEDs lit at the same time, it draws 85mA.

Since the whole device is tiny (SMD), I didn't want to put any large batteries like AAA. But coin cell batteries have a maximum pulse drain @ 15mA and continuous drain @ 0.19mA!? Example of CR2032

I wonder if there are any optimization techniques for circuits to get a better battery life? Or workarounds? Or coin batteries with the same specs as AAA batteries for instance?


texts: Functional role of element within power op-amp circuit

texts:
I came across this op-amp circuit on an applications page for driving piezo transducers, and I am not certain of the purpose of R5 and C5 in the schematic.

My understanding of the circuit is that it is that the voltage swing seen at Vout is double the voltage input swing (assuming R1=R2=R3=R4) due to 180 degree out-of phase relationship of the output between the two inverting amplifiers.

My guess is that the benefit to this circuit is that you get twice the voltage swing at the output with half input voltage rail. However, what purpose do R5 and C5 serve in the circuit?

If this helps:

The original circuit was a general outline of a circuit and the grounds were placed there by me. If placement of ground in the schematic makes this circuit nonsensical, this would be helpful to know.
The op-amps eluded to in the aforementioned sketch are power op-amps designed to drive high voltage/current.


texts: Simple resistance based water sensor works in stagnant water but blows out in running water, under faucet

texts:
The circuit is intended to flash an LED every 7 seconds when
there is no water and to flash it very rapidly (time period less than 1 second) when it "senses" water. It all worked well when tested with stagnant water in a plastic mug. But however keeping the probes under running water from a faucet doesn't change the frequency of the LED and moreover damages the Mosfet which makes it not work with even stagnant water in the same mug anymore. I swapped the mosfet with CD4069 ( CMOS Hex inverter ic) and it works fine with stagnant as well as running water. What could be causing the problem. The water comes from an overhead tank and it doesn't carry any stray voltage.


texts: Comparator: What is appropriate for comparing ranges of about 50-100 mVs? Can I use an LM741 op amp?

texts: I am attempting to create a high voltage signal when the voltage from a sensor I am using drops below a certain threshold, which will be between .05 and .1 Volts. I was trying to use an LM741 op amp to do this, but I could not get it to work as a comparator for these small voltages.  Can anyone recommend a component or suggest a way to get an LM741 to work for comparing such small voltages?


texts: Can a conductor retain charge in vacuum/if it is insulated?

texts: Does a charged conductor always lose charge even if it is in vacuum/insulated?


texts: Relay with contact resistance less than 10mohm

texts: I'm updating an old design whitch uses a manual rotary switch to a new one with relay. A small contact resistance is important for me. The rotary switch version has a contact resistance about 3mohm. But I never seen a mechanical relay specified with such small values. Usually, they only give a maximum value such as '< 30mohm', '< 50mohm', '< 100mohm', etc. The working frequency is 50Hz. The current may as low as 1 micro-amp. So, can I safely replace the rotary switch with a relay? Or, there are other better choices?


texts:
So, I know that vacuum tubes only work because they're, well, a vacuum, and gas-filled tubes have a hysteretic effect relating to gas ionization.

My question, however, is this: Would an open-air 'tube' be a viable device in any situation? Of course, a cold-cathode version of such a device is just a spark gap, but could a spark gap with one side heated (assume, for the moment, that the oxidation of the electrode isn't a problem. Obviously this would be a concern if one was to actually try to make one of these.) act as a crude latching rectifier? Would it be at all usable, assuming actual sealed tubes and semiconductors aren't an option? Could you add a grid, to make an open-air thyratron?

If not, well, I also know that gas-filled tubes are typically (always?) filled with low pressure gas. Would it be possible to make one work at atmospheric pressure in a gas that has the appropriate properties? This would be more practical than the above because an inert gas could be used.

This is a purely academic question, just a strange thought I had. Obviously, this is horribly impractical and unsafe; I'm more concerned as to whether such a device would do anything at all that could make it useful, even if it's much less useful than the obvious alternatives.


texts: MIPS: MARS editor not showing correct value for ASCII string?

texts:
I'm using the MARS simulator to explore the MIPS cpu.  I have a simple assembly program:
.data
ascii1: .asciiz "8C@2"

I expect the value in the memory address for ascii1 to be  0x38434032 (the hex equivalent for the ascii bit pattern for "8C@2").  But it's not.  Here's a screenshot of what MARS shows:
http://img442.imageshack.us/i/mars1.jpg/
Can someone explain why the value in 0x1001000 is not 0x38434032.


texts:
I am learning to draw electronics circuits and trying to identify the voltage and current behavior at different points of the circuit.
When learning from the internet I find simple to complex electronic circuits. Some circuits are purely using analog components and some use both analog components plus microcontroller.
What is the best simulation software where I can draw myself those circuits and learn from simulation?
I might want to draw the whole circuit.


texts: Is there another Arduino ethernet module besides the "Arduino Ethernet Shield"?

texts: On the official Arduino website only the Arduino Ethernet Shield is referenced for Ethernet programming. Are there any other modules for Ethernet on the Arduino?


texts: Is it possible to use mobile phone as sensor for measuring conductivity of a medium? My aim is to avoid any external hardware. The two input channels can be used as 3.5mm microphone jack or USB.


texts: Are these 12v power supplies worth using? Is additional circuitry needed to drop voltage to meet USB standards?

texts:
I have these two power bricks I want to convert one of them to power a Banana Pi and 3.5 HDD.
https://imgur.com/a/qJn1q
I want to determine if either is safe and the needed circuit modifications to do so. This whole thing is a curiosity and not needed from a functional stand point, but I'd like to understand why they have been working for other electronics.
The first one has a molex IDE HDD connector, I will call "Fineness" (rated at 2A for each 12v and 5v from the label photo), seems the most questionable to me because of what I would call overvoltage. Right after I connect wall power to the brick, the 12v circuit reads 16.25v. I connected a 12v fan with a label stating it draws 0.41A. Initially that circuit reads 15.8v with the fan then the voltage increased slowly. A few minutes later the voltage stabilized at 16.4v with the fan connected. Right after I removed the fan, the 12v circuit read 17.5v. The 5v circuit stablizes at 7.2v after slowly climbing. I don't have the knowledge to know if this acceptable with the small amp draw of Banana PI and the hard drive. I've seen forum post photos showing the BPi using as little as 200 mah at 5v USB and then contrasting that with the supposed manufacturer USB power rating of 2A: http://www.bananapi.org/p/product.html. My guess is the voltage sag would be minimal and the incoming voltage would still be far too much for a HDD and above the max of 5.25v max for the USB standard. This power brick originally came as part of a USB to SATA/IDE kit. About a year or more back I successfully used this to power a 3.5 HDD.

My results from testing the molex connectors from the top down:

slot 1 is +12v
slot 2 actually empty, would be Gnd 1, but instead is a plastic stand-in to provide a firm fit???
slot 3 is Gnd 2
slot 4 is +5v

Circuits

slot 3 connected to slot 1 reads up to 17v
slot 4 connected to slot 3 reads up to 7.2v

Is it worth making changes or even necessary to lower the voltage on this Fineness' power brink before I can trust it will not break the Banana Pi and a  3.5 HDD?

So if the Fineness brick is not an option, I could work on this one instead:
Second power brick (see second photo on the imgur link above) has a barrel connector and is rated at 12v up to 6A. When I initially power it reads 16.5v and continues up to 17.75v over a few mintues. I had used this to power a cheap china made audio amplifier with no problem over several months of use and then stopped having a use for it several years back.
I have the same question for this brick about safe voltage. What is needed to create a voltage drop circuit to safely supply 5.25v - 5.0v to a USB plug on the Banana Pi and also 12v and 5v to the HDD?

To me it seems a problem for both of these power bricks to have voltages so far outside of the rated 12v and 5v ranges. There has to be room for a little voltage sag as a load is applied.
Is it actually important to stay within 5.25v for USB? If not, what is acceptable above 5.25v without being damaging?
Is it just by chance that these power bricks have not broken something in the past and they are just too low quality to spend time on correcting?
Do my voltage measurements with no load or a 12v fan not mean much without a more significant load such as 1A or 2A to see how the voltage sags/stabilizes?

Currently, I am using a USB charger for the BPi and the original power brick that came with the external HDD. I'm looking to learn and then apply that by laying out, testing, and then soldering the changes. I'd also like to power the 3.5 HDD without the enclosure's USB adapter which is presently obstructing connecting the HDD to the BPi through SATA directly.
Thanks for your help and consideration.


texts: How do I balance the output from a wheatstone bridge. The 4 resistances are strain gauges of 1000ohms each and the bridge excitation voltage is 10V. Since the strain gauges are pasted to measure load on a mettalic surface, I do not get zero in NO LOAD condition (may be owing to imperfection in the structure/strain gauges). Can you please guide how do I get ZERO when no load is applied. Secondly, How do I adjust the milli volt output at the full load (for e.g I need 3mV/V at 20Kg load)?


texts:
I'm using STM32L4R5 for my project and this is my first time designing a clock source and using an ST microcontroller.
I'm trying to figure out the clocking hardware configuration by reading the clock tree.
I'm planning to use the HSE by adding a crystal.
So for example, if I add a 4MHz crystal at HSE, how do I make the output to Cortex system to 120MHz?
What I understand from the Clock Tree is the HSE signal can be routed to PLL and we can use the Boost mode to boost to 120MHz, but at the output of the SYSCLK, there's a "AHB PRESC", what is "AHB PRESC" and what's the function? And there's a "/8" as well before the Cortex system timer, does it mean my frequency will get divided by 8?
Thank you.
Datasheet - https://www.st.com/resource/en/datasheet/stm32l4r5vi.pdf


texts: Can I use outdoor directional antenna for cellular network indoors

texts:
There are some pretty cellular Yagi-Uda antennas in the market, but absolute majority of it is outdoor type.

Given I have directional antenna with higher gain than omnidirectional antenna X, and I can direct it to the base station, and mount it indoors, will it perform better than omnidirectional antenna X?


texts:
I am trying to replicate project Jasper of raspberry pi. Currently I am using a USB to audio converter (shown in image below) and a regular PC mic. However the audio reception range is very small. So, I am planning to make my custom mic with opamp to amplify the sound signal.

This is the wiring of the mic (which confused me actually):

Pins labelled '1' are GND. However 2 and 3 tend to produce similar output. (I was assuming GND, VCC, Analog OUT kind of stuff so that I could replace the mic with the red modules shown in the bottom left part. They are ADMP-401 MEMS mics along with an op-amp).

Here are the waveforms that I got after randomly shouting at the mic while connected to laptop. I took the readings from Pin 2 and 3.

This is what I want to do:

Use the breakout board to be the mic and that USB to audio converter module (because raspberry pi doesn't have a mic-in) to provide a audio-input to the raspberry pi. The reason I want to use the breakout board rather than regular mic is "lack of good audio reception range".

This is what I think I should do to get it working:

1) Connect GND of breakout board to Pin - 1.

2) Connect VCC to USB 5V supply after using a 3v3 voltage regulator.

3) Connect AUD to pin 2 or 3 whichever tends to work.

One more discovery that I should share:

Before plugging in the mic, the voltages at pin 2 and 3 float around 4.8V but as soon as I plug the mic in, the voltage drops down to 3.7V.

Any suggestions from you guys will be quite helpful.

Thanks for reading.


texts: How does the current know how much to flow, before having seen the resistor?

texts:
With the following circuits as examples :

and

How will the current I know how much to flow?
Would any other wave travel first in the circuit and then come back
and say so much current should flow?


texts: How does the definition of electrical power follow from the chain rule?

texts:
Just a small question for clarification.

Here's what I know:

current I is defined by \$I = \frac{dq}{dt}\$ where q is charge and t is time
voltage V is defined by \$V = \frac{dw}{dq}\$ where w is energy
the chain rule is \$f'(g(x))\cdot g'(x)\$

But I don't see how the definition of power \$P = \frac{dw}{dt}\$  follows from this. How do you use the chain rule on to show that power is just the product of current and voltage?


texts: What connectors can I use that are relatively small and low cost but rated at 30A?

texts:
I was going to use Molex Microfit connectors, which use a convenient "latch
& catch" locking system, but they are not rated at the 30A power level I need.

I noticed the Molex "Fit" series has a "Megafit", but that's still only 23A.

What relatively small and not too expensive connectors can you recommend with a 30A rating?

Ideally I'd like something that is considered "high power, high density".

It's a "wire to board" situation - I need a connector for the board and a connector for a cable.


texts: Does a bridge rectifier care that much for AC frequency?

texts:
As I understand it, a bridge rectifier is a set of diodes that play a trick of logic that keeps the polarity positive.

So, within the context of a household DC transformer does it matter what the frequency of the AC wave is?

I guess it does to a point, since the DC output has a ripple and the smoothing needs to make-up the dips, so I imagine there is some kind of acceptable range, probably dictated by the reservoir capacitor.


texts: Help needed for understanding placement of flexible PCB GSM antenna

texts:
I am using flexible GSM Antenna for my application.I am sticking the antenna on top of my FR4 based PCB board as shown in the below figure. Note that the PCB, on top side (One towards antenna) has GSM module. So effectively, I am sticking the Antenna on top of the module itself with a simple DST acting as boundary between them.
The antenna is connected to PCB via UFL connector through co-axial cable.

I have some questions:
 1. Does folding the PCB the way I have mentioned (In the middle) affect the performance due to any interference in the radiating arm?

Should I use rigid PCB antenna instead of flexible one? Are there any important factors I should consider here in making my design decision?
Does keeping the antenna on top of RF module itself with around 0.8 mm separation lead to destructive interference? If yes, how can I tune the physical placement of the antenna for least interference?

P.S - Here is the link to Antenna Datasheet


texts: Quantization error in ADCs and sampling speed

texts:
Assertion: The noise due to quantization error for an ideal 12-bit ADC gives a signal to noise ratio of 74dB, assuming a signal with full dynamic range at the input.

Suppose I was using an ideal ADC to sample a noiseless analogue signal (i.e. analogue circuitry did not introduce any additional noise to the original input signal). And suppose I was using a low pass filter such that signal attenuation at 1kHz was -74dB. Is it true to say that sampling at greater than 2kHz is called oversampling, and that oversampling will not improve the SNR?

Edit1: 'Low pass filter' is an analogue filter in the above question

Edit2: Bode plot added. fs=2kHz, fa=50Hz.


texts: Registering IOT products across Europe based on NodeMCU

texts:
We've been designing some smart home devices and softwares in past few years and they've been sold in some countries in middle-east. Basically, they were combination of ESP, Arduino and NodeMCU boards which we've added some relay board to them and make them a product since they came with a UI and web service we had provided.

At the moment, I am planning a company in Poland to start my own IOT service and my goal is to sell some NodeMCU based devices with a hosted software, such as temperature control or GPS tracking services.
I would like to import relay boards and temperature sensors and so on from Aliexpress dealers, directly from China to Poland and Estonia.

What I am aware of, at least in paper work level I do need certifications from someone to cover my ass when I am selling these products, since they can make problems if they are overheated or higher current provided to them.

The question here remains is, which certifications the new product that I am designing must pass, in order to be installed on premises legally. Just in case, these devices make a fire, explosion or anything, what would be my escape goat, so I can say I have passed all tests before selling them to customers.


texts: What is rom.txt in quartus prime? What does it do? How do you change it and implement?I’m building a 8 bit alu. Thanks


texts:
I am making a circuit board to test the polarity of the batteries. The batteries will have different voltages from 1V to 60V. I want to detect the polarity with two LEDs. See below circuit diagram I drew. It works, but when nothing is connected still one LED turns on.

Solution by @Unimportant in comments:
I followed the Unimportant solution and built the circuit and it worked fine.


texts: Long distance required between photodetector and TIA

texts:
I have a circuit that incorporates a 40 channel InGaAs (IR) photodetector array (https://www.hamamatsu.com/eu/en/product/type/G8909-01/index.html). I have a TIA design using a LTC6268-10 first stage. However, because I require 40 of these, it is impossible to position all of the op-amps close to the photodetector.
The application potentially delivers quite low light input to the photodetector; I'm estimating ~1uA of photocurrent minimum. Fortunately, InGaAs photodiodes are less noisy than Si, but I'm concerned about noise pick-up on the traces from the wire-bond pads to the amplifier inputs.
As the Photodiode array is common-cathode, I can't connect the anode and cathode across the input terminals of the op-amps, which I believe would aid in reducing common-mode noise.
I'm wondering if I can lay the PCB traces to provide a coax-cable like performance, but I'm not sure how to go about achieving this.
Can anybody suggest some 'expert tips & tricks' that may help to retain my SNR?


texts: How much surge protection do external power supplies provide?

texts:
This weekend a very close lightning strike took out several devices in my house. Among the casualties were:

2 TVs
1 cable modem
1 cable box
1 garage door opener

One of the TVs, the cable modem, and the cable box were all plugged into power supplies that reduced 120 VAC line voltage to 12 VDC (or similar). I tested all the transformers and they are all fried (none of them produce anywhere near their rated output now).

I replaced the cable modem and cable box, but the TV is an expensive item I'd like to salvage if possible. I can replace the power supply for about $15. Is there any chance that the supply "took the hit" and provided enough protection to save the TV? I don't have an easy way of testing it without just buying the replacement supply.

As a more general question, how much protection do consumer grade power supplies provide against voltage fluctuations? I know there's nothing consumer grade that will stop a direct lightning strike, but do they provide effective protection against voltage spikes and drops caused by other disturbances?

EDIT: As it turns out, the $15 power supply did "take the hit" and protect the TV.


texts:
I am trying to drive a 3 pin fan using my MCU.

The 3 pins of the fan are 1- Gnd, 2- Vdd, 3- Open drain RPM output

The fan can draw up to 0.5 Amp.

My initial idea was to use a Darlington transistor, something like the circuit below.

The problem was however that this would mess up the RPM output.

Net idea was to use a RC low pass filter and a Power Op Amp, but I think an Op Amp rated 0.5+A would be too expensive.

Any better ideas/suggestions?

simulate this circuit – Schematic created using CircuitLab


texts: Running NodeMCU ESP8266 on 3s 18650 battery pack powered by solar panel

texts:
I am making a circuit which controls a 12V analog mechanical device using microcontroller (NodeMCU ESP) GPIO.
The Node MCU uses AMS 1117 to step down voltage to 5V (& another one to 3.3V), but since they are clones, the AMS 1117 (for 5V) used allows for a max of 12 Volts. A lot of literature on net is amass with references to how people burnt their circuit due to 12.5 volt input.
I'm using 3s 18650 battery pack with BMS to power the circuit (The battery pack itself is charged by solar panels). The max voltage is capped at 12.6 Volt, which is enough to kill the chip.
So I've some 'alternatives' in my mind, which I'm not sure what their fallacy be:

Take out power between 2 of 11860 batteries, which would give voltage range of 6-8.4 Volts. Good enough to power up the NodeMCU
Put a diode to reduce the voltage by 0.7 volts, good enough to keep the input voltage to NodeMCU to 12V max.

I don't understand the implications to any of these from battery's charge perspective. Since this entire thing will work on battery pack, I'd want minimum wastage of energy ideally.
Can someone please suggest if I'm on the right track, OR what may be the right way to go about this?


texts: In Inductive Position Sensor the air gap between the metal target and coil changes the position value?

texts:
I am trying to design the inductive position sensor with the inductive sensor IC ZMID5201.

I am trying to optimize the air gap betweeen sensor coil and metal target. As per the datasheet its mentioned the output signal remains stable even if the gap between sensor coils and target is varied.
can anyone explain the theroy behind this constant output signal ?
i have attached the Data sheet file with this mail.
thank you


texts:
I am using a small circuit which needs 5V DC input and total current consumption of the circuit is 300mA. I have been using the small size ac to dc converter modules, but now i am searching for a small size IC which will do the AC To DC conversion.
I have been looking all over internet i have found LNK586xx IC but due to lack of Electronics knowledge i could not find the usage circuit for it and unable to understand the usage.

My question is , Is there are other IC which does the required thing.
I am looking for a guidance on this issue. My basic requirement is to make the power circuit most compact than what i am using right now. I am using HLK-2M05 Hilink module.
Link to device which i am currently using .
https://datasheet.lcsc.com/szlcsc/1912111437_HI-LINK-HLK-2M05_C209909.pdf


texts: Poor power factor value through energy meter on maximum solar power exported to grid

texts:
We installed a couple of 100kW grid tied rooftop solar PV plants in factories  which worked without flaw for quite sometime thereby contributing to electricity consumption and reducing the overall utility bills. Noted power factor was always in the range of .95 to .98 lagging, energy meters are bi-directional.
For reasons beyond their control, some of these factories had to shut down for a good part of the month. At this time solar plants were fully operational so majority of kWh was exported and only about 10-15% of total load (lighting, air-conditioning, fans, etc.) was catered to during this period.
To the horror of factory owners, electricity bill for this period carried around 70% penalty for low overall pf, around 0.25 lagging. No change in method of pf calculation, which is, accumulated kWh divided by accumulated kVAh for the duration. Capacitor banks were intact and operational.
Analysis showed that if the solar plants were shut down, all other conditions remaining same, the power factor improved to .91 lagging. Why? To the best of my knowledge, solar power is supplied at unity power factor and GT inverters are not power factor controllers. So it boiled down to 'some' issue with the bi-dir energy meter. But this happened at 3-4 factories so not all meters were defective.
Utility answered that this problem will get resolved on installation of Netmeter. What's the difference - bi-dir vs. Netmeter? How will it resolve the pf issue? Answers are welcome.


texts: Need help controlling a relay using a dimming light

texts:
TL; DR: Trying to control a relay using a dimming light. When the light is fading on and off, it causes the relay to switch on and off very quickly.

Hi all, I am trying to control a relay with the dome light of my car, however the light has a dimming function that I cannot easily remove (built into the Body Control Module of the car).  The light turns off shortly after all doors are closed or the car is locked and turns on when the car is unlocked.

Whenever the light turns on or off, the change in the light is gradual.  When the all doors are closed, the light dims (voltage drops to +8v from ~+12v).  The switch of the dome light is between the negative terminal and the ground.

What I have tried so far:

Wiring a relay between the ground of the light and +12v (parallel with the light), however this causes the relay to switch on and off very quickly when the dome light is dimming, which causes another light (which the relay is controlling) to flash on and off as well.  I do not want this.
Wiring the relay in series with the light, however there is not enough voltage over the relay in this configuration and it does not switch at all.

On the off chance that someone has succeeded in this with the same/similar car, it is a MY07 (though the circuitry should be in the same from 03-09) Subaru Liberty (Legacy in the rest of the world).

Basically I need some way of keeping the voltage controlling the relay at +12 or 0, instead of the gradual change from the dimming function.

If you can think of anything that could control the relay, your input would be highly appreciated.  (I've read up a bit on the 555 IC and delay relays, but I am not sure if they're the right way to go.)

Or if there is something else I could use instead of the relay, that would also be fine.  It just has to function in the same way as the changeover relay I am currently trying to use; 2 position, 3 way switch that can be remotely operated.
 Or if there is something I can tap into that can do that same thing, I'd be happy to attempt that as well.

Here are a few circuit diagrams from the manual showing how the car is connected:

1. Connection between the dome light ("Room Lamp") and the BCM (Body Integrated Unit)

Using the "door" setting on the light so that it is controlled by the door switches.

2. Connection between the BCM and the door switches which control the dome light

The light in the dome light is a LED panel.  All interior lighting has been changed to LEDs (from incandescent bulbs), if that helps somehow.

The relay I am using is the "Tridon Micro Relay - 20/10 Amp, 5 Pin".  Can't link because I do not have enough rep :(

Sorry if it is a bit confusing, I've tried to be as detailed as I can.  If you need any further info or need to clear something up, feel free to ask.

Thanks in advance and good on you for making it this far :)


texts: Help! Regarding solar panel to supercaps to battery charger

texts:
I am looking for some advice on how to improve my current system. In brief, I live off grid but am a keen drone enthusiast. As such, I am constantly having to charge these 0.9 amp, 7.4 volt, 2 cell Lithium Potassium batteries.

A friend helped me to rig up a little system with a 45 watt solar panel and a supercap bank featuring 6x 2.7 volt, 500 F units.

This system is excellent, being very much offgrid, and allows me to charge the batteries very easily. However, there is one catch. I have to be careful to unplug the solar panel so that the voltage coming through does not exceed 16.2 volts (and blow up). This means that I am constantly having to march back and forth to check & plug/unplug the system. Also means that I can never leave the house and go to work to come home to fully charged batteries.

I have included photos of the set up below.

My question:

I would like to put in some sort of resistance between the supercaps and the solar panel so as to limit the voltage coming in from the solar panel to 16.2 volts. But as am not a very tech-lingual, I have no idea what the part I need is called. So can someone advise me on the component I would need? I gather it would be either some sort of DC voltage stabilizer but I am not really sure...

Help!! :D

edit: could not post all the photos as have 0 rep being a new user. Posted the ones I felt were most useful.


texts:
I need help to identify these BM 64 diodes, I can't see any polarity band, D4,5,6 written on PCB. Could they be DIACs?
Seems the designed to protect data lines between ethernet connector & display touch screen ( the White connector.
I measured with Fluke @ 'Diode' they all show 'O.L' both directions.
3× suspected MB64 diodes


texts:
Consider a USB 2.0 device that can be powered either from the bus, from an external power supply, or from both simultaneously. The source of power can be switched at run time while USB is operating. The maximum current consumption is known and does not exceed the 500 mA limited by USB 2.0.

Should such a device report itself to the host as self-powered or bus-powered?


texts: How to find exact datasheet of an Op-Amp from the IC markings?

texts:
I'm trying to understand Op-Amps and reading datasheets. I have an Op-Amp which has the following marked on the IC:

741D
JRC
8001

When I search on the web for 741D I find many different variants such as 741. Is 741D and 741 is the same? Is JRC the manufacturer name? What does 8001 stand for?

Is anything with 741 the same regardless of A B C D at the end of it and manufacturer?


texts: How does the power station compensates for the current that flows down to earth due to domestic body-current faults?

texts:
I know current flows in a loop and energy is used to move it in a loop. Now suppose we get a single phase AC (220/120V) electricity supply for our home and we have earth connection to prevent shocks from the current that leaks on to the metal body of our appliances.

So we have a circuit loop in which current (electron present in the wire) flows from station to house and back to the station (the direction of electron is opposite to that of conventional current flow). Also there are fixed number of free electrons present in this circuit loop.

Now consider a situation where somehow current leaks to the body of a appliance and goes to ground instead of returning back to the power station( due to earthing).

How is this lost current compensated by the power station which never receives it back ?

I was talking about conventional current  so if you talk about electrons I can reframe the question as how does the power station deal with the extra electrons that flows from ground(earth) back to the loop?

Note: I know in the real scenario there are three-phase wires from the power station and a local step down transformer steps it down and provides us with 1 or 2 phases which forms a micro loop between the transformer and the house so the situation remains the same (wouldn't it?), although contained to the move loop instead of the giant loop.


texts: How to connect the GND with the metal case of the robot

texts:
I have a PCB design inside a metal case of the robot. The robot is mobile, it moves on wheels.
The problem is how to connect the GND with the metal case of the robot. Direct connection is not safe, the robot has static voltage after the long use and it is dangerous for circuits.
I found some solution - the connection through parallel R and C, but I’m not sure of the correctness of it.


texts: Analog multiplier using log and antilog amplifier

texts: What should I add here to make it work? The output should be 3 * 5 = 15V.


texts:
I want to get some measurements from a soil using a simple soil moisture sensor like this one:

It has an analog output proportional to soil moisture.

The goal is to send the measurements through Sub-1GHz to a gateway.

In order to avoid an overcrowded band due to number of transmitters-sensors I thought that would be better to connect over than one sensor to a single transmitter. But, it may be a case that a sensor would be more than 20m away.

And the questions is:
What is the proper wired communication protocol to send data in that distance? Just analog value (0-3.3V)? 4-20mA? I2C?


texts: EL wire and Raspi- is it safe and possible?

texts:
sorry for all of these questions, but I just want to check before I break anything accidentally :P
I want to connect EL wire to my raspberry pi and control it via GPIO, but was wondering about the safety of this setup. My main concern is that EL wire uses AC current, but the raspberry pi supplies DC. The wire I plan on using here has an inverter built into the battery pack, so I think I should be fine there. I was planning on connecting power from the pi to the + lead in the battery pack leading out, and a ground to the - lead of the returning wire. The power from the pi will be 3.3v, which should be sufficient to power the wire, but is slightly over. Another thing I was worried about is how fast I can turn the wire on/off quickly to make it appear dimmer. So my questions are these-

Is it safe to connect the lead to the battery pack, or am I inadvertently bypassing any safety features in the battery pack?

Is 3.3v a safe voltage? I've heard it will decrease the overall life of the EL wire, but by how much? Is it worth buying a step down converter to save it?

The converter is built into the battery pack, so I think it should work fine by connecting the pi to the battery leads, but will the extra power hurt it in any way?

How fast can I turn the EL wire on/off per second? Will this reduce the life or overall brightness of the wire? (I know if you blink an LED fast enough, it appears dimmer, and I'm assuming EL wire functions the same way)


texts: Help reading DP4T slide switch schematic

texts:
I am having trouble reading the schematic for the C&K L204011MS02Q DP4T slide switch (datasheet here). In particular, I am trying to identify the "common" pins so that I can wire this switch up correctly on my PCB.

Looking at the schematic for the L202 DPDT switch in the same datasheet, I can see that pins 2 and 5 are the "common" pins - in each of the two available slide switch positions, the switch is connecting pins 2 and 5 to other pins (pins 1 and 4 or pins 3 and 6, respectively).

In the schematic shown in this datasheet for another DP4T switch, the C&K SS-24E06-TG 5 (P), I can see that the center pins of each row are the "common" pins - in each of the four available slide switch positions, these center pins are connected to other pins.

Returning to the L204 DP4T switch, which pins would be the "common" pins? Many thanks for any help - I have searched far and wide on the internet and consulted with two coworkers and still can't seem to figure this schematic out. Also, I don't currently have access to the switch to buzz the pinout manually.


texts: I want to create a step-down transformer from 230V to 115V. This will give us 2:1 turns ratio. So this means 2 turns in primary for every 1 turn in secondary should work. But if the 230 Vac supply given to 2 turns of copper wire, it will burn the wire. So at minimum, how many turns in primary side are needed not to burn the wire. Please explain with maths.


texts:
It is used to harvest kinetic energy from a switch to power an MCU for a short period of time which drives an RF transmitter. Looks like a linear regulator but I am unable to trace it back to the exact manufacturer and part number. Has anyone any vague idea? Thank you

I have taken a broader view photo of the PCB:

Unfortunately what Phil G has suggested could not be possible because the MCU is not fast enough to wake up and transmit an RF signal.

Googling around, the circuit on this PCB is very similar to what is described in this article, reason why I believe the sot23-5 is more like a regulator/buck that's powered up by the tantalum cap charged by the kinetic energy. Looks like the diode rectifier bridge as originally designed has been replaced with a half wave rectifier instead.


texts: How to get 8MHz square signal out a pic18f45

texts:
I am using a Pic18F45K40 to control an ST7590 power line networking
chip which requires an 8MHz clock signal to function. I read the datasheet and it looks like a 16MHz signal can be generated from the 64MHz microchip.

I set up the Reference Clock Output Module as follows:

#pragma config CLKOUTEN = ON

and

#define oCLK_INIT()      CLKRCLKbits.CLK=1; \
                         CLKRCONbits.EN=0;  \
                         CLKRCONbits.DC=2;  \
                         CLKRCONbits.DIV=3; \
                         SCANTRIGbits.TSEL=1;
                         //OSCCON1bits.NOSC=6;
#define oCLK_EN_ON()       CLKRCONbits.EN=1;

and used PPS to pin RB4 by setting

  RB4PPS=0b10100;        /* B4=CLKR 8MHz      */ \

I do get an 8MHz signal out but it looks like this:

This is more sinusoidal than square and might be the reason why I am not able to talk to the ST7590 chip via UART.
Can anyone explain what is happening?

EDIT: Result of changing slew rate.


texts:
On a demo board I have, USB 5V rail is connected via a resistor divider to one of the GPIO's of MSP. MSP itself is powered from PCIE 3v3AUX rail.

In one of the cases when the board is not connected in the PCIE slot but it is connected to USB, I see that the GPIO pin is set as 3.3V. Also, when I measured the Vcc pin of MSP, I measure 0.7V.

I as assuming that the ESD clamp diode is turning on, but do not understand why there is 0.7V on Vcc pin of MSP. I am expecting that the drop across the diode will be 0.7V, so Vcc pin should be ~ 2.6V. Is my theory incorrect??

Can you help me understand what can cause 0.7V at MSP power pins?


texts:
i have made a function called _MY_Delay() which use 16bit timer/counter1 in ATMEGA16
, and used this function to blink a LED . the problem is i didn't work and i don't know the reason , here is my code :

 #define  F_CPU 1000000
 #include <avr/io.h>
 #include <avr/interrupt.h>

 void _MY_Delay(int delay){
 int n = (delay*F_CPU)/(1000*64) ; // number of counts required for the given delay
 OCR1BL = n;                    // n =T(overflow time)*F_cpu / 64
 OCR1BH = n >> 8 ;
 while (!(TIFR & 1<<OCF1B));
 }

 int main(void)
 {
 DDRA = 0x00;
 DDRA |= 0x01;
 TCCR1B = (1<<CS10)|(1<<CS11); //divide by 64 (prescaler)
 sei();
 TIMSK |= 1<< OCIE1B ;
 WDTCR = 0x00; // disable watchdog timer
 while(1)
 {
    PORTA |= 0x01 ;
    _MY_Delay(100);
    PORTA &= ~(0x01);
    _MY_Delay(100);
 }
 }


texts: Possibly using a latching relay on a device test circuit

texts:
I'm a materials reliability scientist, not an electrical/electronics engineer, so I could use some help.  I am running an experiment where I pass between 0.5 and 5A through 50 DOT's and measure a voltage drop across the devices w.r.t. time, up to 500 hours.

At some time, a device will fail, causing an open circuit.  If this happens during a weekend, I am not near the equipment to short around the device that failed, so that the other DOT's resume current testing.  There are two issues with this:

Lost test time when the whole circuit is open, and
Possible partial recovery of the remaining devices. The voltage across the failed device is 42V, but I can adjust the current source to a lower maximum voltage.

I think adding a small circuit that will short out the failed device, so that the remaining devices continue to be exposed to the test current, might be possible.  Including a simple mechanical switch and an indicator LED would be nice. Because I would need 50 of these circuits, they would need to be small and inexpensive.

I have looked at latching relay circuits on this forum, and they are all connected to ground.  I don't think this is possible with what I want to do.

Here is a sketch of my test:

Any help would be appreciated.

Thanks for the helpful replies.  Here is another sketch, is something like this do-able?


texts: Why does my multimeter show a wrong voltage over a large resistor?

texts:
I am having a hard time answering one particular question about our experiment.. In our experiment, R1 and R2 were set to 1Meg each and later to 10k... I understand the need for R1 and R2 a bit. Without R1 and R2, the voltage sharing wouldn't exactly be 50-50 for both D1 and D2 because no two diodes are completely identical. D1 and D2 will both have the same leakage currents (without R1 and R2) since they are just in series. However, they probably will have non-identical IV curves, so this particular leakage current will result to V@D1 /= V@D2.

The question I am having a hard time is that, why is V@R1 + V@R2 /= 10v when R1 = R2 = 1Meg?... One the other hand, those two voltages add up (to 10v) when R1 = R2 = 10k... I included the 60 ohm source resistance in my diagram for completeness. However, as I can see, both D1 and D2 are reversed biased and thus, they offer a very large (reverse resistance) which should be much greater than the 60 ohms. Even with the parallel combination of 1Meg and D1 reverse resistance, it should still be much greater than the 60 ohms. I tried thinking of an answer in terms of the RD1reverse//R1 = Req1 and RD2reverse//R2 = Req2. Req1 + Req2 (series) should still be much more than 60ohms and I thought that the 10v should still show up at the node of D1 cathode. Yet in our experiment, V@R1 + V@R1 < 10v.

Can anyone point me out if I am thinking this in a wrong way? Some tips/first step hint would really be appreciated

Edit: question answered thanks to @CL. Assuming D1 and D2 are open during reverse bias for simplicity and noting that Rmultimeter = 10Meg, V@R2 (shown on multimeter) = 10v * (1Meg//10Meg)/((1Meg//10Meg)+1Meg+60) = 4.76v measured.