texts: Suppressing sparks when powering motor controller

texts:
When I connect a 36V Li-Ion battery source to a cheap eBay DC motor controller, there's a significant spark on the wire, regardless of connected components.

Should I:

1) Add capacitors to the input wires? If so, what farad and voltages are appropriate?

2) Create inductance by running a battery wire around an iron core?

3) Ignore it and live with my sparkanoia?

4) Something else?


texts: Solenoid Actuation Circuit for Hocky Robot - High speed, Maximum force

texts:
I am working with students designing and building small competition robots.
We have done quite well but I am having trouble with the design of a circuit to actuate a solenoid to quickly launch a 4 inch hockey puck. We are currently using an ESP to provide 24 vdc to the solenoid, but I would like to find an appropriate circuit to interface the RC receiver output to control the solenoid.
The solenoid has a 1.25" stroke and rated at 12V. The coil measurements are 1.25mH at 1.6 ohms.
The utimate goal would be to use 12 vdc for the system and get the absolute maximum speed and force from the solenoid (without letting the smoke out of the components). An explanation of the functional aspect of the circuit would also be valuable to the students,and me, as well.
I have seen some examples that use a capacitor in a circuit, but I am open to any suggestions.
Thanks, in advance, to all for your help! This is my first post!


texts: Eagle, drillegend-stack.ulp - difference between holes and vias

texts:
I was just using drillegend-stack.ulp to generate the drill info table for our manufacturer. At the end, this ulp throws three different layers (144, 145, 146) and I usually just make them all "144 DrillLegend".
The question is, is there a reson for Eagle (or this ulp) making holes as if they'd go throught "01-20" and vias "01-16"?
It's just a 4-layers PCB and I am not using any burried or blind vias, so everything should be throughout entire board...


texts:
Is it possible if i connect one side of this sensor to hot surface and another one to a heat sink or something cold after that it gives current?
I have a very hot surface about 300 (C) and want to recharge a battery or use it to supply my circuit in emergency time. Maybe i should use more than 10 tec1 sensor to receive enough current.


texts: Capacitor charging curve when using a voltage regulator with current limiting?

texts:
Most voltage regulators have output impedance in the low mOhm range, some also have internal current limiting circuits.
I want to know what the charging curve of a large capacitor might look like when connected to a voltage regulator output with current limiting, if that makes sense.
The inrush current would likely trigger the current limit in reg for a spilt second, as if the capacitor was being fed from higher impedance source, as cap's current draw tapers off and falls below the current limit the remaining charge would be filled up quickly because of the regulators low output impedance.
Seems to me that the charging curve of the cap if measured in this instance would be very different to the typical RC curve.
Is this correct?


texts: Solder jumper wire to the pin of a mounted chip

texts:
I have a USB serial device from Sparkfun.

https://www.sparkfun.com/products/15096

Unfortunately, I need access to the RTS pin (to, connect to an ESP8266) but this module does not pin it out. I have found and manually tested the correct pin on the chip itself. Is it possible to solder a jumper directly to the chip's pin, and use that? Are there good tutorials on this? Googling didn't reveal anything relevant.


texts:
i want to hook up upto 5 lighting bulbs, 12watt each from a 12v battery. These lighting bulbs will be feed directly from a 12v battery without any inverter etc.
The main question is that for a 100 yards or about 300 feet distance
 what gauge wire should I use to avoid extra waste/loss of power from the battery.
Thanks


texts:
Is there a way to measure or predict how much a 10.5 microns Aluminum foil attenuates EMF radiation? And at what frequencies?

Is it enough to use as  Faraday shield?


texts: Please help me understand this bjt set up works

texts:
This is part of an automotive timer (NOT a 555!) that we have at work. Because I'm extremely bored I'm challenging myself to understand how this one operates. I've spent about 1.5 weeks with tutorials, brushing up on my transistors, flip flops, electrostatics and such. My area is RF not power and this is extremely difficult for me. I tried as best as I could and it's keeping me up at night.

I know that a BJT needs to have a base voltage to turn on but this one's base is connected to the inputs of a NAND gate as featured in the pin out of the IC. (a CD 4011BC)
There are a number of other connections but I haven't drawn them here to keep things simple. The emitter is connected directly to a relay coil and the approx measured voltages are listed on the paper. The collector gets +12V in and the base is connected to pins 13 and 12 which are inputs into a NAND gate on the IC.

I do not understand how this device is able to run. I don't have all the pin-outs drawn on this picture but I do have it elsewhere. I wanted to focus on how the bjt can even turn on if there's no (what I assume to be at least) base voltage or current. It does run though, and times correctly. From what I have learned it's in the active region of operation.
Please help!

Editing to add another picture. Note that the drawing differs slightly from the picture due to connections running under the IC. The dot on the IC is at the top left, so the 1-7 pins are on the left side. I drew it the way I did to make it easier to visualize as, of course, traces are all over. I can redraw this if necessary. Also, the stuff on the caps is melted rubber band goo, not exploding cap goo.


texts:
Why are OR gates used with shorted inverted inputs, effectively acting as NOT gates in this circuit? (Page 9 of this datasheet.)
What's the difference with directly putting a NOT gate, other than having a bigger capacitive load due to the transistors gates? Is it to have a bigger delay?
Why does the inverter between 14 and 15 has its inverting bubble drawn at the input and not at the output?
Also I guess the output inverters are put in parallel in order to increase the driving capability, i.e. to lower the output resistance.


texts: What's the name of the force that opposes the movement of magnet trough a coil?

texts:
I am trying to make an experiment that looks like this:

I am using this source https://physicshandson.wordpress.com/2019/02/04/damped-oscillations-in-mechanics-and-electromagnetic-induction/ as a piece of evidence that when a magnet passes the coil, which is connected to resistor some force opposes the movement of the magnet, therefore damped oscillations occur.

Few questions.

Is 100 turns of copper wire enough for this kind of experiment? I have fairly strong magnets.
As I understand the damped oscillations occur when the coil is connected to a resistor, however, the article mentions "Then we short-circuited the coil. The induced current created a magnetic field that, according to the Lenz Law, has the same effect on the magnet as a paper plate on a simple mass. Magnetic force worked exactly the same as a force of air resistance." So the question is: is the coil short-circuited or connected to the resistor?


texts:
I am helping my sister make a LED poster for a concert she is going to. I am using a foam board with some letters she placed on there. I am then going to add LED's on top of the letters to spell them out so you can read them from a distance.

The LED's I have on hand are:

Light Color : White;Forward Voltage : 3.2 - 3.4V

Luminous Intensity : 10000 - 12000MCD;Main Color : Silver Tone, Clear

There will be a total of about 60 LED's on the sign. My questions are, what type of circuit do I need for this? I currently have a battery pack that take 3 double A batteries but not sure if that will be enough.

Any thoughts on the best way to go about doing this? I estimate the sign will be on for ~2 hours. She can take another set of batteries with her if needed.

Thanks for any advice you can provide!

EDIT: Here is a link to the LED's that I have. http://www.amazon.com/gp/product/B0087ZT06U?psc=1&redirect=true&ref_=od_aui_detailpages01

UPDATE 2

Here are some images of the Power box I have:

This is the only pack of resistors I can find in the house. This is a last minute project and a lot of radio shacks have closed near me. Not sure If I can do anything with this :/


texts:
I'm trying to find how i can test a schottky diode to check it's state but can only find info on 2 pin diodes. The particular diode is this: http://pdf.dzsc.com/2017/20161120/20161120081219688637.pdf

Am i correct in putting positive lead from multimeter to anode (pin 1) and negative lead to cathode (middle pin)....if i get a beep, it's working fine. i get no beeps, so is this diode dead?

the diode is part of a speed controller which isn't turning on.

if it's dead, is there any way I can bypass it to make sure the rest of the controller is actually working?

thanks,
sal


texts: Is there a potentiometer model for LTspice?

texts:
I started designing a model for a three-terminal potentiometer in LTspice, since none are included and it's such a common component. Drawing the .asy symbol and the wiper terminal, it dawned on me that this was going to be more complicated than it appeared. How would the various tapers be modeled? How would this taper be "controled" during simulation? It looks like a subcircuit and library at least, is in order.

Before I reinvent the wheel, has anyone done this already? Thank you.


texts: How are SMD microcontrollers preloaded with code?

texts: Often when you buy an SMD microcontroller (say AVR) or a PCB with an SMD microcontroller it comes preloaded with whatever program that board uses to run. I was wondering how it is preloaded - I guess DIP ICs could be programmed using DIP sockets, so are there special SMD sockets?


texts: Water Sensor to detect backed up drain pipe?

texts:
Trying to detect when a drain pipe, filled with water from a washing machine pump, starts to get backed up.

Since the water is being pumped through, a simple water detector is not enough. And since the water is being pumped and draining, but slowly (Too much water volume for the pipe in a small amount of time), I don't know if a float sensor will work (downward movement from pump, upward movement from backing up).

Also, the pipe is about 2.5" in diameter. The sensor should interface to a 3.3v or 5v level, or simply open drain, but I can figure it out from there if I need to level shift. It should be water tight to prevent shorts or anything (Though I don't know the proper safety method for this).

Is there any standard way of doing this? The microcontroller (a msp430) will not be submerged or anything, just the sensor.

Edit: Picture/Diagram as requested.

Setup is essentially exactly the same. Pumped water goes down "standpipe", as does the backflow up. My main access is only at the section marked "Indirect Connection, a 2~3" diameter pipe. The Waste Stack is probably 4~5" diameter.
There is a sink that is in parallel with the washer machine, and water sometimes backflows out of there instead of the "indirect connection", as it is a few inches lower.

Ideally, the sensor could fit and work right above the trap in the diagram, without clogging the pipe itself. I might be able to add a t-pipe between the trap and waste pipe, but I want to avoid that if I can.


texts:
Can an electrolytic capacitor discharge through its top?
Is it potentially dangerous to touch a large electrolytic capacitor on the top if fully charged?


texts:
How do I find two's complement for hex F3A1?

First I converted the number to binary 1111 0011 1010 0001 and then I found two's complement 0000 1100 0101 1111 givin' as result 0C5F which differs from the answer in the book: 0A57

What I'm doing wrong?


texts: SN754410 output supply current - heating

texts:
I am experiencing excessive heating problem with SN754410NE (SN754410). I know that I can use heat sink, but I want to be sure that I am not doing something wrong.

I am using SN754410NE to drive a bipolar stepper motor. My circuit is similar to schematic below. The current rating of the stepper motor is about 0.6 A and since continuous output current is given as 1.1A in the data sheet, I don't expect excessive heat.

However, the other issue is output supply current is given as 70mA in the data sheet. So, for example, if I energize one solenoid of motor output current of '1out' pin will be 0.6 A (which is below rating) however '2out' pin supply current will be also 0.6 A (which is above rating). Am I correct? Can this cause excessive heat?

SN754410NE data sheet: http://www.ti.com/lit/ds/symlink/sn754410.pdf

(source: g9toengineering.com)

Thanks in advance.


texts:
I bought a 5m LED strip from Ebay and connected it to 12V 1.5Amps. I am a starter in engineering.

What kind of potentiometer do I need to use to lower or increase the brightness? How many Ohms do I need for it? PS: if there is a formula I`d like to hear it also :D


texts: How to connect Li-ion batteries with thermistor pin in parallel?

texts:
I have a Li-ion charger with 3 contacts: (+) (-) and (TH), based on TP4056 chip. I also have several batteries with corresponding contacts, and the charger does a good job charging them.

Now I would like to increase the capacity by connecting a stack of batteries in parallel. TP4056 is able to handle the increased load (according to the datasheet it can even handle a continuous short in the load circuit) and I don't mind the increased charge time. I'm taking all the precautions I can think of before connecting the batteries together, like only using similar batteries and charging them to the same level before connecting.

While connecting (+) and (-) terminals of all batteries in parallel is obvious, I don't quite understand what to do with (TH) terminals. Should I connect them in parallel as well, or should I only connect a terminal of one battery (supposedly somewhere in the middle of the stack) to report the temperature to TP4056?


texts: Advice on Bulk Current Injection Testing

texts:
I am having trouble getting a new product I'm working on to pass Bulk Current Injection Testing. I had trouble on the 50mA test at around 30MHz where the Ethernet link was not functional.
I have a 6 pin M8 connector on my PCB. It has 2 Ethernet twisted pairs and PWR and GND. The cable feeding my PCB has a shield. The housing of the PCB itself is mainly plastic but there is an aluminum frame inside which the PCB attaches to.
During the BCI test the shield was connected to GND before the current injection clamp went around the cable. The shield on the device under test side was left floating.
Is there any use in me connecting the shield of the cable to the aluminum frame which is in turn connected to my PCB GND?
I already have common mode chokes on the Ethernet pairs but I do not have on PWR GND, is this worth a test?
Do you have any other tips on how I can pass this BCI test?


texts:
I want to convert this device from 240v to american 110v
I noticed on the bottom of the photo i have a blue wire going to 240v input.
Can i simply move the blue to 117 to make it work in US?
or do I have to change the transformer as well? (41305H0000 / TB-60)


texts: Why do we have four instructions in IT block for Cortex M4 processor? Is it related to the fact that we have three pipelines for ARM assembly instructions?


texts: So, in a single wire transmission system, the earth acts as the return path for current to "flow back to source". Would this work for anywhere on earth, say, if we transmit current on a single wire from Paris to Los Angeles, ignoring the voltage drop on the long transmission wire.


texts: Question about production of computer USB peripheral

texts:
I have a game controller. This controller have USB cable and when connected it is instantly recognized by the computer.  I wanted to know what it made of so I opened the case and found "STM32F103C8T6" chip. I googled and found : http://datasheetz.com/data/Integrated%20Circuits%20(ICs)/Microcontrollers/497-6063-datasheetz.html

At first I thought inside must have a kind of stock "joystick chip" or something but this is actually a general purpose computer. (Probably with custom program loaded in it?) So the ability to interface with computer depends solely on the program loaded in this MCU?
Does other computer gadgets (Mouse, Keyboard, MIDI controller, etc.) all have this kind of computer inside?
If I wanted to produce a computer goods too, where should I begin to get the complete circuit board in the end? The chip looks like it is not removable from the board and the connection around it is very small. I guess it have to be assembled by precision automatic machine from factory only. (Not the one you can buy separately and assemble like ATMEGA on Arduino. That one is much bigger and you can actually count all the pins with your eye)
How can the maker (who? factory?) program into it in the first place?
I found several "discovery board" that have this chip and also USB port so you can program into them. So does it means I can also program back into this STM chip on my game controller? Because after all I am using a USB connection to use the controller, and this USB connects to the MCU. I think this same USB should be able to do "using" and "programming".


texts:
I know 9600, 19200, 38400, 57600, 115200 and 1.8432 Mbaud, but no others. Why are these values used, and is it simply doubling each time or is there something more complex going on (for example, 38400 quadrupled is not 115200 baud?)

The reason I ask this question is I'm designing something which may have to interact with a variety of different baud rates. It will initialise in 9600, and then switch to a specific baud rate. But I can't support arbitrary rates because the dsPIC33F I am using does not support arbitrary rates as it is limited to a 16-bit BRG down counter. It's similar in this regard to many other processors.


texts: Overvoltage Protection for Battery Charger

texts:
I'm trying to come up with some form of precise overvoltage protection between battery chargers and batteries between 12V and 48V batteries. I have 12 and 24 sorted using different methods: crowbar circuit, voltage monitoring relay, even Arduino and some voltage monitoring devices off of Adafruit.

However, 48V overvoltage protection is giving me a lot of grief. My crowbar circuit is way too imprecise and has too much tolerance... for VRLA batteries, the charging voltage is around 53.6V and I need the protection to trigger at 56.4V. Unfortunately, I cannot find a Zener diode with the required ratings, nor do voltage comparators like TL431 go up to that value. Industrial voltage monitoring relays are way too expensive. And I cannot find a solution using an Arduino because of the ratings. Keeping in mind, 48V battery charger supplies up to 250A (2500AH capacity batteries).

I'm having a bit of a mental block here. I am really hoping someone can point me to a standard configurable overvoltage protection device for the required rating.

Thanks.


texts: PID-controller and Ziegler-Nichols Method: How to get oscillation period?

texts:
I'm a bit confused about how to measure the oscillation period of a quasi-stable system when using the Ziegler-Nichols method to get the correct PID configuration. The factor of the oscillation period is used in the rule for the I and D terms, but in what unit? seconds, milliseconds, minutes? Does it have something to do with the sampling time of my digital PID controller?

Pcr is used here for describing the critical period (at the critical gain Kcr setting)


texts: How does the Miller effect affect a JFET-amplifier stage with tuned-circuit input?

texts:
I'm trying to build a simple JFET amplifier of MW signals (500kHz-1.5MHz) using a ferrite antenna and a variable capacitor to tune the desired station. The schematics is pretty obvious, as seen in the following figure:

While designing it, I wondered if Miller effect has any impact here, as it will lead to a capacitance between JFET's gate and source and, with source grounded at AC due to \$C_s\$, Miller capacitance will appear in parallel with tuning capacitor \$C_t\$ so, apart of modifying the tuning range (which I can compensate adjusting the self-made coil) I don't see any other obvious harm here. Am I right?


texts: Does the diameter of the coil in a motor determine the amount of volts needed to run it?

texts:
I am making a DC motor and i got coil from a transformer and the coil is a lot thicker than the coil in your usual DC motor, i want to ensure that the motor runs on 9 volts, the coil is about 1 mm in diameter.

So my question is:

Will it run on more than 9 volts?


texts:
Tried to change baudrate of the esp8266 with At command "AT+IPR=9600".
After reset, blue led on the ESP8266 was constatly on and could not communicate with the device using AT commands.Before changing the baudrate I could communicate with ESP8266 with At commands.After abit of search on the net, decided to flash the device with new firmware.

Downloaded the lastet firmware version: esp8266_nonos_sdk_v2.0.0_16_08_10 from Espressif official website.I Followed intructions according to the readme file in the folder(esp8266_nonos_sdk_v2.0.0_16_08_10). which bin file goes/flashed where. Using nodemcu flasher and it was a success according to the log file of the flasher.The problem am encountering is that I still can`t communicate with the esp8266 with AT commands.using Arduino serial monitor to communicate with the device mentioned.

firmware ver when I bought the chip
SDK version: 1.3.0
Build:1.3.0.2


texts: Is there a way to measure distance to a surface of a liquid (water for example) using the V6180 time of flight sensor?

texts:
I'm using the Vl6180 time of flight sensor to measure a distance to a surface.
This surface is a liquid, water for example. In my setup, the sensor doesn't detect the surface, the pulses from the laser goes right through. It seems there is not enough reflection at the surface.
Putting something on the surface that will reflect is not a solution in my case.


texts: what's the correct way to add counter inside flip-flop?

texts:
I want to count number of "clock enable" signal inside flip flop.

I learn from tutorials that the output value should be assigned for all combinations of input.

However I don't know how to add counter that counter should be updated only if clk_enable = 1.

Please advise.

module count_ce (
  input logic reset_n,
  input logic clk,
  input logic clk_enable,
  output logic[63:0] counter
);

always_ff @(posedge clk or negedge reset_n) begin
  if (!reset_n) begin
    counter <= 64'd0;
  end else begin
    if (clk_enable) begin
      counter <= counter + 1;
    end else begin
      //counter <= counter; // ?
      counter <= 64'd0; // have to assign counter for else-case otherwise infer latch?
    end
  end
end

endmodule


texts: How to design DDR3 PCB without any termination resistor in processor and RAM connection

texts:
As I'm going to design my first high-speed PCB, I'm confused with some mismatches between what i see in high-speed PCB design tutorials and what i see in real world designs. in the PCB handbook named "RIGHT THE FIRST TIME" by "LEE W. RITCHEY", it's discussed that the transmission lines higher than 1/4 TEL will fail from reflection. In some boards like raspberry pi 3 and banana pi BPI-M64, i don't see any termination resistor between Processor and RAM IC(s). As the frequency of the Allwinner A64 and 4 512 DDR3 RAMS in BPI-M64 is about 800MHz i think 1/4 TEL is less than 1 Centimeter but in the board I see the routes are longer than 2 on 3 Cm without any termination. the The question is:

Is it realy possible to do such designs without termination resistors or I am calculating in a wrong way?


texts: Differential op-amp vs non-inverting op-amp

texts:
Suppose you have to amplify a signal with a gain of 2 .
The signal is referenced to ground, which means V1 is zero.
Is there any reason why one would use this circuit below instead of a normal non-inverting amplifier.

Picture obtained from https://www.electronicshub.org/differential-amplifier/

So in that case what is the difference between this circuit and the "normal" non-inverting amplifier were R2=zero and R4= removed.
The only difference I see, is that with the differential amplifier you are able to achieve a gain less than 1.
Are there any more reasons?accuracy?etc


texts: Why solvent cleaning of clean wafers includes de-ionized (DI) water?

texts:
Solvent (or solution) cleaning of clean wafers includes acetone wash, isopropyl alcohol (IPA) wash and de-ionized (DI) water wash, followed by drying in nitrogen.

What's the purpose of using DI water? Isn't it increases the overall (undesired) humidity on the wafer?


texts: Connecting laptop webcam 04081 to USB cable

texts:
After seeing some youtube videos, I wanted to reuse an old laptop webcam and solder it to a USB cable.

This one comes from an ASUS X301A and looks like this:

AFAIK, The USB cable needs 4 wirings: VCC, ground, data+, and data-.

This webcam shows 5 wires, which I tried to identify. Red and brown wires were twisted together. I believe that I can guess data+ and data-, with no major risk for the camera, but VCC and ground should be strictly identified.

I will refer to 3 components:

the ground ring
the 4-pins component on top of it (A)
the 2-pins component with plus and minus signs (B)

With a multimeter on beep mode, here are the wirings that I identified:

Both orange and yellow wires are connected to ground
A pins top-right and bottom-right, and of course B-, are connected to the ground
The brown wire is connected to top-left A pin
The red wire is connected to bottom-left A pin

My problem is that I could not identify any pin connected to the black wire or to B+. Moreover, the fact that 2 wires are connected to the ground looks a bit strange to me (why use 2 wires?).

Therefore, I am very confused about which wire to connect to the USB cable.

Based on this, is there a way I could identify which is which?

EDIT

As @Justme said in comments, beep mode is not sufficient, so here are the actual resistance values (2k ohms):

Multimeter's red on component, black on wire:

+--------+--------+------+------+------+------+------+
|        | ground |  A+  | Btl  | Btr  | Bbl  | Bbr  |
+--------+--------+------+------+------+------+------+
| black  |   0,42 | 0,89 | 0,47 | 0,47 | 0,47 | 0,47 |
| brown  |   0,42 | inf  | 0    | 0,64 | inf  | 0,64 |
| red    |    0,6 | inf  | inf  | 0,64 | 0    | 0,64 |
| orange |      0 | inf  | 0,85 |    0 | 1,5  |    0 |
| yellow |      0 | inf  | 0,85 |    0 | 1,5  |    0 |
+--------+--------+------+------+------+------+------+

Multimeter's black on component, red on wire:

+--------+--------+-------+------+------+------+------+
|        | ground |  A+   | Btl  | Btr  | Bbl  | Bbr  |
+--------+--------+-------+------+------+------+------+
| black  |    1,1 | inf   | inf  | 1,08 | inf  | 1,08 |
| brown  |   1,46 | inf   | 0    | 1,46 | 1,66 | 1,46 |
| red    |    1,5 | inf   | 1,67 | 1,46 | 0    | 1,46 |
| orange |      0 | 0,878 | 0,64 |    0 | 0,64 |    0 |
| yellow |      0 | 0,878 | 0,64 |    0 | 0,64 |    0 |
+--------+--------+-------+------+------+------+------+


texts: SysTick Timer in ARM arch - Mazidi book part

texts:
In mazidi book ARM arch. , using the sysTick Counter... i read this part

  Program 5-1 loads the initial value to the maximum and dumps the
  current value of the SysTick on LEDs of PORTF as it counts down. On TI
  ARM LaunchPad, we cannot see the lower 16 bits since it is counting
  down every 62.5 nsec (1/16MHz=62.5). It takes the lower 16-bits 65536
  x 62.5ns= 0.4096 ms to overflow to the upper 8-bits. That is the
  reason we shift it right 20 times.

and here is the code

#include "TM4C123GH6PM.h"
int main (void)
{
int x;
/* enable clock to GPIOF at clock gating control register */
SYSCTL->RCGCGPIO |= 0x20;
/* enable the GPIO pins for the LED (PF3, 2 1) as output */
GPIOF->DIR = 0x0E;
/* enable the GPIO pins for digital function */
GPIOF->DEN = 0x0E;
/* Configure SysTick */
SysTick->LOAD = 0xFFFFFF; /* reload reg. with max value */
SysTick->CTRL = 5; /* enable it, no interrupt, use system clock */
while (1)
{
x = SysTick->VAL; /* read current value of down counter */
x = x >> 20; /* shift right to slow down the rate */
GPIOF->DATA = x; /* dump it to the LEDs */
}
}
/* This function is called by the startup assembly code to perform system specific
initialization tasks. */
void SystemInit(void)
{
__disable_irq(); /* disable all IRQs */
/* Grant coprocessor access */
/* This is required since TM4C123G has a floating point coprocessor */
SCB->CPACR |= 0x00F00000;
}

My question is regarding the part inside the while(1)
I still cannot see how does shifting right x = x >> 20; can slow the rate so we can see the LEDs" ??
and why did he exactly choose to shift 20 times ?!


texts: UHF Band-pass Filter - Is it bidirectional? SMA connector convention?

texts:
I have this 1090MHz Band-pass SMA Filter.  It did not ship with a datasheet.

Is such a device bidirectional? i.e. is there an in and out?  Is there a directional convention using SMA male and female connectors?

I have a collection of SMA adapters and am confused with the combinations of male and female barrels each with both male or female cores.

Thank you.


texts: I wanted to create a square wave that alternates between positive and negative voltage with a full cycle time of 8ms and a 50% duty cycle. So is there a way I could make a circuit that takes in 0V and a voltage V_in (roughly in the voltage range of 1V-7V), and that outputs the square wave as well as the inverse of the square wave. The load I'm going to put on the signal is very minimal (below 10 mA).


texts: Switch on time limiter for a solenoid - will this circuit work?

texts:
Here is the problem i have: there is an electromechanical door chime (just a solenoid with a rod inside, which hits one brass pipe when switched on, and, propelled backwards by a spring, another when power is turned off). The problem is that it does not have any protective circuit preventing the solenoid from being turned on for too long, which, in worst case, may cause it's overheating and setting on fire. I actually found out that i'm not the only person being aware of such scenario, there is an article (in Russian) on it, they also provide a simple circuit to resolve this problem

Hovewer, i tested it on lower voltage components and was not satisfied with the fact that it still lets some current through solenoid and it's "reset time" is relatively great, if you press the button actively. So, i've designed my own solution below.

It works as expected when simulated in Proteus, hovewer, i understand that simulation sometimes may be far from reality, so, given the fact that i'm a total newbie in analogue circuits, could anybody point out on any design mistakes i made?

(just in case, L1 represents the solenoid, RV2 is used to change switch on time).
Thank you!


texts:
I'm completely new to the world of FPGAs, and would like to get a sense of what is possible to achieve, and since I happen to have an interest in convolution reverb algorithms, I will use that example.

So given a room response of 10 seconds (i.e ~500000 samples at 44.1kHz), is it realistic to expect that the FPGA could handle the brute-force algorithm (which is basically a FIR filter with 500000 coefficients, running at 44.1kHz, in double precision floating point)?

An fft-based implementation would need less multiplications / additions, but since it's more complex, I'd like to begin with a simple example first!

It would be nice if in your answers you could describe the FIR-filter implementation, and produce a back of the envelope calculation, with the numbers for a specific FPGA so that I can follow your reasonning.

Thank you very much!


texts: Is there any way to differentiate the sound of blowing air from normal sound through phone microphone?

texts:
I have been working on an Android app that takes input from microphone when user blows into it. I am using FFT based sound analysis and converting the values in frequency by using a zero crossing method.

I am still unsatisfied with the results. What I want is, it should only detect the "air-blow" and should generate a unique value, so that i can ignore all other sounds. I have been searching for the same on Google a lot but was not able to get any clear answers. I hope I will get some solution out here.

EDIT: Now, I did not really get enough time to research on the solutions provided. Also, I think I will have to take the formulas and create my own classes in JAVA and it's going to take time. But I would like to share the link for the application that I published. It is not the most efficient as I mentioned in my question but it works. The link for my app is:

Appy Birthday on Play Store

I would like Android users to try it and provide me feedback as well.


texts: Tiny wi-fi module on one board with ALU and memory?

texts:
I am looking for small and cheap wi-fi modules and I want to know, what are the current best results in this area. Also, I would like to know, if it is possible to seamlessly integrate such modules on one board with ALU and memory (to make it sort of "fundamental" thing, playing vital role in small device's functioning).

Sorry for kind of stupid question and thanks for your answers!


texts:
I am trying to simulate a comparator in pspice capture student version. The problem that I am facing is that circuit is not working for higher frequencies because the opamp I am using is not ideal.

I downloaded opamp.olb and opamp.lib from this link http://robustdesignconcepts.com/files/pspice/pmindex.htm  and tried many opamp modals from this library.

I have searched some other libraries from this page too but I cant find an ideal opamp modal.

Can anyone share any pspice libraries which has ideal opamp or guide me how to build one.


texts:
I am trying to interface an RS422 to the UART on my MCU. Now, RS422 is differential. So, I understand that I need to have a differential to single ended converter IC.
This is followed by a voltage level shifter to match Voh,Vol,Vih and Vil voltage levels of the MCU UART.

Other than this do I need any buffers or protocol convertyers ?
The data is sent at standard baud rates of 460800, 230400, 115200, 57600, 38400, 19200, 9600, 4800 bps.
Also, the UART standard rates are in baud, right ?
How will it impact the bps. Because baud means symbols. For eg 9600baud = 9600x8bps.


texts:
Solution
This issue was caused by the choice of SOT-23 symbol when creating my PCB in KiCAD.
As you can see in the picture below, there are a number of symbols associated with transistors in the KiCAD default library:

When mocking up my circuit I chose the first option 'Q_NPN_BCE'. The key elements here are the last three letters which define the pinout in KiCAD. What I didn't know at the time, but know now, is most common SMD transistors have a 'BEC' pinout rather than 'BCE' (or 'CBE', 'CEB, etc...).
If you are running into a similar issue, you can verify which pinout your transistor is by referring to the datasheet.
The pinout of a SOT-23 package is counted from the first of the two pins going in a clockwise motion:

To determine which symbol you should pick in KiCAD, just read out the pins in the same order.

In my case it's Base, Emitter, & Collector, or 'BEC'. So when choosing the symbol from the KiCAD library, I should choose the 'Q_NPN_BEC' option.
Hopefully this can help someone having a similar issue in their circuit design!
Original Post
I guess I should preface this with the fact that I'm definitely a beginner when it comes to electronics and circuit design/debugging. Thanks for the help!
I recently developed a circuit board for use with my Raspberry Pi 3 A+. The purpose of the board is to accept various inputs, but also toggle some relays (two solid state, and two regular). My current issue is that I can't seem to turn relays C and D on. I'd hoping someone could help me find out where I went wrong.
Here's a snippet of my schematic for reference:

This is what I know so far:

All the outputs on the pi are working properly (I can see ~3.3v at R2 - R5 when I toggle the respective pins on).
All channels of the optocoupler are working properly (I can see ~5v at R6 - R9 when I toggle the respective pins on).
I'm unsure of exactly how to tell if a transistor is doing it's job with a multimeter, but if I plug a resistor and led into J8 or J9 I can verify those channels are working as the led lights up when I toggle the respective pin on.
I can say it's not the protection diode installed wrong, as removing it had no effect.
If I run a wire from GND to pin 2 of either of the relays, they click.

My best guess right now is that I chose the values for R6 - R9 incorrectly for the application.
Datasheets:

https://www.vishay.com/docs/83512/tcmt1600.pdf
https://www.diodes.com/assets/Datasheets/ds30036.pdf
http://www.smc-diodes.com/propdf/1N4148WS%20N0572%20REV.B.pdf
https://datasheetspdf.com/datasheet/SRD-05VDC-SL-C.html

Update
It was brought to my attention that the collector and emitter of my transistor may be flip-flopped. After reviewing my design and the datasheet I'm inclined to agree. Here's a picture for reference:


texts: How does TTBCR affect low addresses in ARMv8-A?

texts:
While reading about translation tables in ARMv8-A, I came across the following:

  Depending on the size of the possible VA range, there can be even
  fewer levels. With a 4KB granule, for example, if the TTBCR is set so
  that low addresses span only 1GB, then levels 0 and 1 are not required
  and the translation starts at level 2, going down to level 3 for 4KB
  pages.

TTBCR selects if translation table walk is allowed and whether TTBR0 or TTBR1 is used. How does it affect the range of low addresses?


texts: I custom board with STM32F429IGT6 ST-Link v3 using the ST-Link Utility. "No target detected"

texts:
I did my own board with STM32F429IGT6, and connect the ST-Link v3 using the ST-Link Utility. "No target detected".
Previously I had made my own boards, and the minimum connection is Vcaps to 2.2uF capacitors, nRst with 10k pull-up, and Boot to ground.The boards worked fine.
The device is not detected by the programmer. Already checked supply voltages and grounds. Also SWDIO and SWCLK wires.

PIN 124  (TMS_SWDIO) -> PA13
PIN 137  (TCK_SWCLK) -> PA14


texts:
I'm trying to write a zeros and ones counter in assembly with the AVR ATmega328P.

To choose between the ones and zeros, I have a switch in PC5.

For the input there are 8 switches connected to PORTB and one to a pin in PORTC.

The bits are like this:

PC1(Most significant bit)
PB7
... PB0(least significant bit)

For the output, I have to send the zeros or the ones count to a 7-segment display.

I am trying reading PORTB, use a mask(ANDI) to get the least significant bit, compare if it is one or lower(zero), add one to one register dependig if its zero or one to another register if its one, shift the entry(LSR) to keep checking and so on.

Reading the control switch and printing the display are no problem, but I found some circunstances where it gets a little bit complicated. For example, how to concatenate in a register the value of PORTB and the pin in PORTC?

Im trying to use a cicle and at some point I would have to check if I have already the 9 bits and them send the count out, should I use a counter?

I had made a reaserch of easier ways to implement this problem but no relevant info found.

Begin:
    IN R23, PINB
Jump:
    ANDI R23, 0x01
    CPI R23,0x01
    BRLO Zero
    BREQ One
Shift:
    IN R23, PINB
    LSR R23
    RJMP Jump
Zero:
    INC R18
    INC R16 //counter??
    RJMP Shift
One:
    INC R17
    INC R16//counter??
    RJMP Shift

The counter idea is not completed, just an example where the actualization would be. For the counter(INC R16), I'm also missing the bit in PC0. I could manage to read after reading PORTB, but I was trying to use a more elgant implementation. I know I have to check the counter at the beginning to see if it's done, and send the output if it is.

Thanks a lot for the help. (:


texts: **Specifically, the "Tprint" I am asking about is the one shown below, in the syntax explanation part, I tried finding out the function of this parameter by changing its value, but from my graph I didn't spot any change for telling.


texts:
I'd like to build a simple AM radio (so simple it will only receive a single AM channel).

What is the simplest way to build a single channel AM radio that will output to an 8ohm speaker? (e.g. 1030 AM)

My current thinking is along the following somewhat vague lines, but I'm hoping to make them more concrete.

use a piece of wire as an antenna
create an LC circuit to tune input from antenna to the desired frequency
amplify the signal
connect amplified signal to speaker

Aside from the antenna, I would prefer to use "discrete" off the shelf components such as capacitors and inductors of particular values that I could plug into my breadboard.


texts:
I am fairly new to pcb design and I just created a mpu6050 chip that will work with an Arduino microprocessor. I want to make sure the hookup is all correct before I start work on the other parts, as this is the most complicated. It will be using standard i2c communication with scl and sda with the default (low) address being selected. The datasheet can be found here: https://datasheet.lcsc.com/szlcsc/TDK-InvenSense-MPU-6050_C24112.pdf

-Thanks!


texts: Possibility of using 5A 5-220VDC Solid State Relay for switching 120VAC String Lights

texts:
I have purchased this Relay Board http://www.sainsmart.com/sainsmart-8-ch-ssr-5a-dc-dc-5v-220v-solid-state-relay.html

This board uses a mager GJ-5FA-L relay with input ranging from 3-32VDC and a coil switching range of 5-220VDC at 5A.

I have done some research and have found relay power ratings - AC vs DC stating:

  ...relays are allowed to switch only a fraction of the AC power if DC. It's not uncommon to see 250V AC relays only rated for 30V DC....

This would seem to reason that since this relay can handle a maximum load of 220VDC that it would easily handle 120VAC. But what concerns me is a comment on the product page on amazon https://www.amazon.com/SainSmart-DC-DC-5V-220V-Solid-State/dp/B00TEUEW0G stating:

  Note that the load is only switched in one direction. If you reverse the + and - on the load connection, current will flow even with no voltage applied to the input circuit.

I know that AC is alternating current and flows in both directions, does this mean that if this relay is applied a 120VAC current that it will fail?

My application is using raspberryPi GPIO pins to switch on and off Christmas Lights that are string 120VAC.

Reference Materials:

https://forum.arduino.cc/index.php?topic=231045.0
Arduino SSR 5V DC (Mager GJ-3FA-L)


texts:
So I have a simple circuit with a 24VDC input, a 2200ohm resistor, an LED, a solid state relay, and a float switch controlling when the LED (and SSR) are turned on.

I'm curious if running the resistor and LED directly inline like this on the 24V is going to harm the resistor over a long time. The SSR and float switch are behaving as expected and being able to run the LED, which is just simply a visible marker that the SSR is connected, in series like this instead of parallel works a lot better with my current setup.


texts: use of diodes and resistors in a push-pull amplifier

texts:
I am a beginner in electronics facing a bit more difficult problem.

what might be the function of the two resistors(R4,R5) and diodes(D1,D2)? in the circuit below?


texts: Digital filter implementation in C (embedded)

texts:
I am a recent grad and my new project at work deals with taking the signal from an electret microphone and getting SPL values for 10 standard frequency bands.

The analog amplification/conditioning is completed so I am now trying to figure out what do in terms of sampling/filtering. My frequency bands are:

31.5, 63, 125, 250, 500, 1000, 2000, 4000, 8000, and 16000 Hz

I decided that I should be able to use a 160kHz sampling rate (apparently 5-10 * Nyquist rate is recommended according to my old notes) and use 10 2nd order Butterworth bandpass filters that were designed using mkfilter. After this point I am unsure how to proceed.

Would I simply use the 16kHz filter every sample, the 8kHz filter every 2 samples, the 4kHz filter every 4 samples and so on? ( I am getting these numbers by using 5*Nyquist rate for each band, e.g. 1/(8000Hz*2*5)/(1/160000Hz) ) ? Then I would then convert the values to a pressure and do the math necessary for a SPL measurement. Is there a better way to approach this? Is my understanding correct?

The hardware I am working with has a 48MHz clock and 32kB of flash and 4kB of RAM.


texts: Can I use a lithium charge module on NiMh batteries? The charge module has 2 led, one for charging and one for full that I would really like to use with my NiMh batteries.


texts: Why have both a Schottky Diode and a MOSFET for reverse voltage protection?

texts:
I was looking at this open-source power supply circuit for an automotive CANBus device. I am wondering it would include both a Schottky Diode (D1) and a MOSFET (Q1) on the power supply line. My understanding is that both of these are to provide reverse-voltage protection.
Is redundancy of two reverse-voltage devices just that, to have a failsafe? Or do these two devices have different characteristics that make it desirable to have both?

Edit: Here is a link to the schematic: https://github.com/macchina/m2-hardware/blob/master/M2/Interface%20Board/Interface%20Board%20Schematic.pdf
It is from the open-source Macchina M2 CAN Bus network analyzer.


texts: How does Powerline cope with line fluctuations

texts: I have a powerline (Ethernet over power) between two sockets in the house. And it seems to work even when I turn some heavy load (ie hairdryer, washer, etc) to the point even the lights dim for a second... And the powerline does not skip a beat. How does it do that?


texts:
I come from a computer background, and apologies if this question sounds elementary. While designing a dynamo, I came across a problem of how to calculate the the strength of the magnetic field, and to be used to find the electrical current generated by the dynamo. The magnet design called for a rotating ring, and an inner fixed stator mounted on the inner side of the rotating magnetic ring. The problem was to calculate the Webers at distance 4mm from the inner side of the ring.

So, to do so I assumed the gauss strength of the magnet to be 8000-10000 gauss for a small lab sized magnet with dimensions, Outer Ring radius (8cm), Inner Ring radius (5cm), so the ring has width of 3cm. The ring thickness is 2cm. The distance from which we measure the gauss to get the magnets' strength is 4mm from the inner side of the ring. I have two questions:

Are my assumptions about the magnet correct? i.e. regarding the gauss strength, for a lab magnet with the dimensions specified? Are lab magnets stronger? Typically, industrial magnets can go up to 100000 gauss.
I get a -ve (something like -900 gauss) answer for the gauss field strength at the distance from the ring, how is this to be accounted for, and how to I convert this gauss strength to Webers (so as to find out the electricity generated)?


texts: I've tried to repair a headset, but I cannot identify the chipset because they used something that looked like QR code but smaller (wikipedia states that it's micro QR) and I have no solution to read it (cheap if possible, but i can spend money for quality).


texts:
Accordion to this question , i am searching for AC/Dc power supply part, so i found this video. For AC/DC part of that system used this :

made like this:

to  using as AC/DC part of this component:

So like to know what is this kind of AC?Dc power supply name and how could increase the output current to 5A to use all capacity of XL4015 DC/DC Converter.

Also if possible say about this part (AC/DC part) of that video ( the operation mechanism).

Thanks.


texts: Why are BJT operating modes named the way they are?

texts:
I know that a Bipolar Junction Transistor has four operating modes dictated by the base-collector junction and the base emitter junction's biasing:

What I can't seem to find is the reasoning behind the naming, as in why they are named that way. I have a feeling it has something to do w/ the diode model of the BJT:

and I know the basic operation of the diode, but can't make sense of this for some reason, and can't seem to find it on the 'net.


texts: What does linux need to be on a microcontroller?

texts:
I am going to put linux on a microcontroller, attach an LED to the microcontroller, a battery and hope that the LED blinks. But before I do that I need to put Linux on a microcontroller. And to put linux on a microcontroller I need to know what kind of microcontroller linux can be loaded on.

So my question is this:

What kind of microcontroller can linux be put on (ex. mmu? ARM Cortex A0? max number of timers? max core size?)?


texts: Determine best capacitor for inductive load

texts:
If I know the Watts, the Power factor, the VA, or anything the standard Kill-A-Watt meter can measure, how can I determine the best capacitor to use for a heavily inductive load?

I have some Microwave Oven transformers I am using and I am hoping to make the power factor better. Once I have a good power factor, what changes would one expect? Would the MOTs have a higher power ability? Or will it just cause the power bill to increase because I am actually pulling a power that the company measures?


texts: What would happen to the magnetic fields of a solenoid if it were wrapped around a hollow ferromagnetic core?

texts: I'm well aware that a solenoid wrapped around a solid ferromagnetic core produces a stronger magnetic field, but what about a hollow ferromagnetic core? Would the fields farther from the center near the hollow ferromagnetic core become more powerful, or would the middle of the field become more powerful? If something else happens do say so! I'm seeking to understand the fields produced by such a setup.


texts: Is there software with CAS to solve drawn electrical circuit in form of differential equations which describes that electrical circuit?

texts: Is there any software with Computer Algebra System to solve drawn electrical circuit in the form of differential equations which describe that electrical circuit? Or to write symbolic solution (matrices) of state space equation?


texts: Can I use a solid state relay to control a DC current?

texts:
Can I use an AC solid state relay to control a DC current as long as the DC voltage doesn't exceed the rated AC voltages?

I want to control a solenoid but I'm concerned about the inductance problem of the device. Will a solid state relay survive the back EMF of the solenoid when turned off by  itself?


texts: Where to get PSPICE models of ceramic resonators?

texts: I wish to design and simulate IF filters using ceramic resonators and crystal oscillators in OrCAD Capture or LT SPICE. The default libraries don't have any ceramics, so anyone know where to download libraries?


texts: Reducing solar panel voltage (30V) where DC to DC regulator switches off at 28 V or above

texts:
I have purchased a flexible solar panel to charge my caravan batteries via a DC to DC charger/regulator which turns off when the voltage gets above 28.2 V. The panel is rated 28.5 Vopen circuit, 200 W, max power volts 23.2 V, [9.1 amps].

In bright sun my volt meter reads 30-31 V and this causes my regulator to shut down. The adviser for the regulator manufacturer suggested putting a load across the + & -, aglobe 24 V. These have been popping.

Is there a better way with out sacrificing too much power for charging?
thanks in anticipation, Pete Moonta


texts: Alternatives to a hardware configuration of an input pin for uC

texts:
I'm trying to figure out how to read-in a configuration to the small ATtiny10 microcontroller.
I want to find out 5 or 6 different configurations, adjustable by hardware into one IO using the same firmware to make settings in the program. At the moment there are 3 DIP-switches used for this, and as you expect we need full 3 IOs. This corresponds to 8 different configurations. Can this be reduced to only using one IO? So I can switch over to an ATtiny10...

Of course I could also use the internal ADC and attach a voltage divider. Maybe it could also be purely digital.
Internal Pull-Up (software switchable) has according to data sheet 20 kΩ to 50 kΩ.
I come up with different possibilities to use an IO as configuration input:

(a) Pull-Up (high impedance) e.g. 470kΩ to VCC/VDD,
(b) Pull-Down (high impedance) e.g. 470kΩ to GND/VSS,
(c) Pull-Down (low impedance) e.g. 1kΩ to GND/VSS, if the internal pull-up resistor is on, it will be overridden during a read-in with internal pull-up set,
(d) Using an RC-element, see schematics,
(e) RC-element using another configuration.

simulate this circuit – Schematic created using CircuitLab

My idea and procedure (for instance):

Set IO to input, internal pull-up on, wait a minimum of 500 ms,
Read input: High on a), b), d), e) ; LOW on c) -> case (c) detected;
Internal pull-up off, no wait;
Read input: High on a) d) e) ; LOW on b) c) -> case (b) detected;
Wait 1 ms,
Read input: High on a) e) ; LOW on b) c) d) -> case (d) detected;
Wait 500 ms,
Read input: High on a) ; LOW on b) c) d) e) -> case (e) detected; and case (a) also detected.
If d) or e) was detected set output pin to GND, else keep it as input.

In these cases, I therefore only need to mount two components on the circuit board in three designated places: (a) 0R + 470k (b) 0R + 470k (c) 0R + 1k (d) 100k + 1n (e) 470k + 100n; with all the same component size (e.g. 0603)

I hope that you can support me with further ideas?


texts:
simulate this circuit – Schematic created using CircuitLab

From my analysis, and applying circuit theory, I find that Load(A) will have current flowing equal to 0.1Amps due to the PS, and the induced V1&V2 cancel out, without the use of a diode. However, there cannot be any induced-current from the induced-voltage source correct? They cancel out before that happens?


texts: Current Shunt Vs Current Clamp Meter - 15% difference Which one is right?

texts:
I have a variable AC power supply. 0-12V 0-1800A 60hz.

I have always been told to trust the current shunts and not current clamps when measuring current. The current clamps are supposed to accurate to less then 2%. Our current clamps have always been about 5-15% different then the current shunts though. I want to know  why, and which one I should believe.

My boss wants me to prove to him that the shunts are more accurate than the clamps but I don't know where to begin.

All items are calibrated annually.

Fluke 353 (1.5% accurate)
Ideal 61-746 (1.7% accurate)
Current shunt 500A 50mV (10:1 ratio) (Empro)
Current shunt 3000A 50mV (60:1 ratio) (Ram Meters)
Current shunt 2000A 50mV (40:1 ratio) (Empro) (EDIT: Added)

mV meters for the shunts are fluke 45 and Fluke 289 both read the same

I adjusted the power supply based on the current shunts.

    500A shunt - first Iteration
           Shunt         Fluke  Ideal
Target  mV      Current
50      5.5     55       48     49     13%  11%
100     10.5    105      91     92     13%  12%
200     20.1    201      178    182    11%  9%
300     30.1    301      263    269    13%  11%

    3000A shunt - first Iteration
           Shunt        Fluke   Ideal
Target  mV      Current
100     1.716   102.96  98.3    100.3   5%  3%
200     3.345   200.7   190.7   194.7   5%  3%
300     5.023   301.38  284.8   292.1   6%  3%
400     6.695   401.7   379.4   389.1   6%  3%
500     8.356   501.36  471     484     6%  3%

    500A shunt - second Iteration
           Shunt        Fluke   Ideal
Target  mV      Current
50      5.125   51.25   45.3    46.5    12% 9%
100     10.304  103.04  91.9    93.5    11% 9%
200     20.3    203     181.2   185.1   11% 9%
300     30.225  302.25  269.3   275.8   11% 9%
400     40.21   402.1   357     366.2   11% 9%

    2000A shunt - first Iteration (Fluke 45)
            Shunt       Fluke   Ideal
Target  mV      Current
50      1.21    48.4    37.17   38      23% 21%
100     2.44    97.6    84.7    86.4    13% 11%
200     5.02    200.8   181.9   186.3   9%  7%
300     6.31    252.4   230.5   235.8   9%  7%
400     10.09   403.6   360.2   372.2   11% 8%
500     11.31   452.4   405     415     10% 8%

    2000A shunt - second Iteration (Fluke 45)
             Shunt      Fluke   Ideal
Target  mV      Current
50      1.26    50.4    29.33   29.5    42% 41%
100     2.48    99.2    65.7    65.5    34% 34%
200     5.14    205.6   141.3   144.1   31% 30%
300     7.46    298.4   207     211.5   31% 29%
400     9.89    395.6   284.4   290.6   28% 27%
500     12.5    500     355.3   362.6   29% 27%

    2000A shunt - third Iteration (Fluke 289)
            Shunt       Fluke   Ideal
Target  mV      Current
50      1.21    48.4    37.2    37.4    23% 23%
100     2.51    100.4   76.6    77.3    24% 23%
200     5.14    205.6   165.5   168.8   20% 18%
300     7.58    303.2   252.6   257.8   17% 15%
400     10.11   404.4   344.6   351.7   15% 13%
500     12.49   499.6   418     426     16% 15%

EDIT:
After I calculated the error rates it looks my 500A is off more than the 3kA. I am going to try it with a 3rd shunt tomorrow.

EDIT2:

200A 50mV Shunt

Fluke 353 Clamp Meter

Fluke 45


texts: Connect pins with same pin designator in Altium footprint

texts:
I've made a relay's footprint in Altium. The relay's two contact terminal are three pads each, as below.

And the schematic symbol is as below:

In my schematic, I don't give the two terminals any net, and they are floating (connect nothing). In the PCB editor, I want connect the three pads together using tracks, such as the three pads with the designator "87", but the Altium PCB editor prevent me doing this, the pads can't be connected!

I tried give a net to the terminal "87", then I can connect the three pads using tracks. I want to know what's the "strategy" behind this? I think if I give the pads same designator, they should be treated as just one pad, and should be "connectable". Right? Is there other easier method to make them connectable (I have 24 such relays, and it will be a hard work to give nets to the terminals)?


texts: How does the position of the gound influences the node voltages?

texts:
Here is the circuit which caused a long sleepless night and I would like to explain why:

I have seen similar schema in this question (How to calculate time constant for RC circuit with more than one resistor), however, the author was concerned about the Thévenin resistance. My question is about the Thévenin voltage. It is known that the capacitor can be represented as open circuit in DC conditions. I remove the capacitor from the circuit and obtain two voltage sources in series and two resistors in series. Then the voltage on the capacitor terminals is

V = (15 + 7.5) - (15 + 7.5) * 2/(2+6) = 16.875 V

However, the correct answer is 9.375 V which is calculated in the following manner. We assume that the ground is in the bottom of the schema. Then we assume that the capacitor node is still there and there are 3 currents: from 15 V source, fvrom 7.5 source and into capacitor. And then we write the equation for the capacitor node:

(Vc - 15)/2 + (Vc + 7.5)/6 = 0    ; 0 because no current flows through the capacitor

Vc = 9.375 V

Here is the simulation in LTSpice:

And here is the question: why should I assume that the ground is in the bottom of the schema? If I will ground the circuit just after the second resistor, I will got the value I calculated from the very beginning:


texts: What's the low voltage displayed by a voltmeter when only one of its probes is connected?

texts:
Recently I was toying with a digital multimeter and observed the following. The multimeter was set to measuring AC voltage with the upper limit of 750 volts. It has two probes which I will call "red" and "black" to better illustrate what happened. Both probes were connected to the multimeter and I didn't alter their connection to the multimeter.

I inserted both probes into mains (220 volts in my region) outlet - one probe per outlet hole - and it showed something around 220 volts. Now I unplugged the "red" probe from the outlet while leaving the "black" probe plugged into the outlet - the multimeter displayed zero. I plugged the "black" probe back into the outlet and unplugged the "red" probe from the outlet - the multimeter displayed about 7 volts.

So again, one probe was connected to the multimeter and the outlet terminal and the other was only connected to the multimeter with one end and the other end of the second probe was pointing in the air - not in contact with anything. The multimeter displayed 7 volts.

Why did the multimeter behave that way? Where do those 7 volts come from?


texts: Powering the Raspberry Pi zero from printer PCB

texts: I want to convert my simple printer into a network printer with CUPS on Raspberry Pi. I tested everything with Raspberry Pi 4 and it worked perfectly. Now, I want to fit my Raspberry Pi zero inside the printer. My plan is to connect D+ and D- of the printer's USB directly to the D+ and D- of Raspberry Pi's USB port and find some 5V pad on the printer's PCB to power the Raspberry Pi from that. After testing some pads with the multimeter, I found both 3.3V and 5V on the printer's PCB. First I connected 5V and GND pads to the Raspberry but it the Pi didn't boot. When I checked the voltage across Pi's power line, it was not stable and kept changing from 2.5V to 4.2V, I disconnected the 5V and GND from Raspberry Pi and measured it again, but it was stable 5V this time. As soon as I connect it to the 5V pin of Raspberry Pi, it starts changing. Then I connected 3.3V pad on the printer's PCB to the 5V pin of Raspberry Pi. A similar thing happened again. The 3.3V pad on printer's PCB was stable before connecting it to the Pi, but as soon as I connected it to the Pi, it dropped to 1.9V, Please let me know what what's the issue. Thanks.


texts: Burn a HEX file into Brenner8 using linux

texts:
I have got a version of Brenner8 called AEI when I try to burn my HEX file into
PIC16f877a using command

 usburn -w -s40 -F16 -Ifilename.X.production.hex

I got this output

usburn V 0.4 (16.05.2010) by sprut (www.sprut.de)

search for Brenner8/9:   Brenner8 detected, Fw: 15

check firmware

no calibration data

supported:  PIC10F , PIC16F , PIC18F , dsPIC30F , PIC18FxxK ,

Database detected V.24 (06/05/2010)

PIC-Type: unknown


texts:
I am trying to count pulses from a waveform generator using an Arduino Uno. The waveform generator is set at the following settings:

Waveform Type: Pulse
Freq: 20 Hz (50ms)
Amplitude: 3.0 Vpp
Offset: 0V
Width = 5ms

So far I get only 0s displayed on my serial monitor.

Here is what I have tried so far:

1) Using pulseIn() and pulseInLong() --> no success

2) Check wiring connections --> Used multimeter to check and they are properly connected.

3) Hookup an oscilloscope to see if the waveform is being generated --> The waveform is being generated as shown in pictures below.

Note: The waveform generator is part of the oscilloscope:

My code is shown below:

volatile int IRQcount;
int pin = 2;
int pin_irq = 0; //IRQ that matches to pin 2
int result = 0;

void setup() {
  // put your setup code here, to run once:
  Serial.begin (115200);
  pinMode(2, INPUT);
  attachInterrupt(pin_irq, IRQcounter, FALLING);
}

void IRQcounter() {
  IRQcount++;
}

void loop() {
  // put your main code here, to run repeatedly:

  cli();//disable interrupts
  IRQcount = 0;
  sei();//enable interrupts

  delay(500);

  cli();//disable interrupts
  result = IRQcount;
  sei();//enable interrupts

  Serial.print(F("Counted = "));
  Serial.println(result);
}


texts: Decoupling Capacitors: What happens to the DC on the cap once noise is introduced and it shorts?

texts:
simulate this circuit – Schematic created using CircuitLab

I've been using decoupling caps for a while now and I understand their purpose in keeping DC signals clean since capacitors allow high frequency signals through that get passed into ground and don't show up on the capacitor as built up charge in DC form, so they don't disturb the signal on the load.

What I've been wondering for a while is, if a random noise spike is introduced into the system from the power source or from an external source through capacitive coupling, what happens to the charge already stored on the capacitor? If the capacitor is fully charged to 1v as shown in the schematic, and it then instantaneously acts as a short to bypass the high frequency noise into ground, would a short show up on the load? Would the load have 0 volts applied to it in that instant? If this is the case, would the load not be disturbed in operation for that nanosecond in which the capacitor shorts? I'm just having a hard time understanding exactly how the capacitor can bypass charge and act as a short while still maintaining its charge built up from the DC source.

It's been explained to me in school that caps block DC but pass AC, but I feel like that on its own doesn't explain decoupling well enough. Thanks for your time.


texts: How to wire a GSM module to my alarm system

texts:
I have an alarm system that has been installed by an alarm dude ;)

I want to add a GSM module to the alarm system, so that I'm notified when the alarm is triggered. Before I purchase the module I need to understand where to wire it into my alarm control panel.

I have studied the control panel, but I'm unsure where to connect the output of the control panel to the input on a GSM module. Do I need to use a multimeter to measure voltages and currents while the alarm is triggered to figure this out?

UPDATE: I'm providing some more information as requested by Rocketmagnet.

The alarm system is Swedish manufactured and I have read through the manual (image comes from it), but there is no information on wiring a GSM module.

I didn't want to complicate this question, so I left out the details of the GSM module. I plan on creating this module with an Arduino uno, GSM shield etc. This is my first electronics project and I've already found the necessary resources on the arduino, gsm bit.

My concern at the moment is figuring out how to get the necessary output/ trigger from my alarm system which I'll then use as input to my arduino project.

I hope this helps somewhat.

UPDATE 2: First I'd like to thank everyone who has provided lots of good information and advice. I took a photo of the real control panel as a few of you have been asking about the model and make.

I will attempt to take some measurements today (see UPDATE 4 below).

UPDATE 3: As request by Cybergibbons here's an additional diagram from the manual showing how to wire a keypad. Note that I do not have a keypad, but a simple turnkey lock in the front door that activates the alarm.

UPDATE 4: I finally got a chance to take some measurements. I was quite apprehensive at first and worried I'd f*** up the alarm or myself :P

I did as tyblu suggested and put the black probe on the negative terminal of the backup battery and the red probe inside each of the positive outputs: BL, S1 and S2.

When the alarm is unarmed & armed there is no voltage at the outputs which I guess is to be expected or the sirens would sound all the time.

When the alarm is armed and I set it off by walking in a room with a detector, I get the following readings:

 BL 13.16V (DC) 28.5V (AC)
 S1 13.16V (DC) 28.5V (AC)
 S2 13.16V (DC) 28.5V (AC)

After chatting with Cybergibbons it seems that my multimeter is not behaving and the readings above are wrong.


texts: Foster's Reactance Theorem - Reactance Increasing with Frequency?

texts:
I'm currently reading a text on analog filters (Zverev) that discusses Foster's Reactance Theorem in relation to passive circuits and I was thrown a little by the text that says: "Physically, this signifies that the impedance or admittance of the reactive network always increases in value when the frequency is increasing" (Pg 37 for those with the book).

Then the description of the theorem on wikipedia (wikipedia entry) has a similar line: "It is easily seen that the reactances of inductors and capacitors individually increase with frequency and from that basis a proof for passive lossless networks generally can be constructed".

I'm obviously missing something, but I always thought that the reactance of a
capacitor decreased with increasing frequency.  What don't I understand?


texts: How can 4 resistors of 30ohms each be connected so you end up with a resistance of 18ohms?

texts: An association of 4 resistors of 30ohms each, how can one assemble them so you get a resistance equivalent of 18ohms?


texts: is the battery line on an OBD2 plug always on?

texts: I'm looking at building a circuit that's powered by the OBD2 plug on a car. I can't seem to find if there are any specs around what the battery voltage pin does when the key is removed from ignition. It's entirely possible that the answer is "it depends on the car," but I'm looking to see if anyone knows for sure / can point me to some specs.


texts:
I am trying to interface a ADXL345 to 8051 - AT89C51RC2 through SPI interface.

I have used the below code taken from here:

 include "Init.h"

 define SS_ADXL P1_0;

 void SPI_interr_routine(void);

 char serial_data;

 char data_example;

 char data_save;

 char transmit_completed;

void main(void)
{

    // Insert code
    Hardware_init();
    transmit_completed = 0;
    data_example=0x55;
    data_save = 0;
    printf("\n\r1111111111111");
    SPCON |= 0x10; /* Master mode */
    P1_1=1; /* enable master */
    SPCON |= 0x82; /* Fclk Periph/128 */
    SPCON &= ~0x08; /* CPOL=0; transmit mode example */
    SPCON |= 0x04; /* CPHA=1; transmit mode example */
    IEN1 |= 0x04; /* enable spi interrupt */
    SPCON |= 0x40; /* run spi */
    P1_1 = 0;
    EA=1; /* enable interrupts */
    //while(1) /* endless */
    //{
        SS_ADXL = 0;
        SPDAT= (0x32 | 0x80); /* send an example data */ //
        while(!transmit_completed);/* wait end of transmition */
        transmit_completed = 0; /* clear software transfert flag */

        SPDAT=0x00; /* data is send to generate SCK signal */
        while(!transmit_completed);/* wait end of transmition */
        transmit_completed = 0; /* clear software transfert flag */
        data_save = serial_data; /* save receive data */
        SS_ADXL = 1;
    //}

    printf("\n\r%c data_save = " , data_save);
}

void it_SPI(void) __interrupt (9)
{

   SPI_interr_routine();

   return;

}

void SPI_interr_routine(void)
{

    if((SPSTA & 0x80) == 1)
    {
        serial_data = SPDAT;
        transmit_completed=1;
    }

    return;
}

Hardware Connections :

I have used this logic level converter  to connect the 8051 to ADXL345.

P1.1 (SS) pin of 8051 is unconnected and I am enabling it in software by setting P1.1 to 1.

The CS pin of ADXL345 is connected to a GPIO of 8051 and I am selecting the slave (ADXL345) by setting the GPIO pin to low before writing / reading and then setting it high.
I am using the inbuilt SPI module in 8051.

When I run the above code, the SPIF bit is not getting set.

please let me know if anything is wrong with the hardware connection or the code.

Thanks


texts:
I made a toy program on Arduino to write "Hello, World!" to the display using delays after every command.
Now I was wondering if I could get rid of the delays if I read the busy bit.
This is the current program
enum pins {
    RS,
    RW,
    E,
    D0,
    D1,
    D2,
    D3,
    D4,
    D5,
    D6,
    D7
};

const int NPINS = 11;
int busy = 1;

void setup() {
    for (int i = 0; i < NPINS; i++)
        pinMode(i, OUTPUT);

    // clear display
    pin_set(0, 0, 0, 0, 0, 0, 0, 0, 0, 1);
    pin_send();
    delay(2);

    // function set (8 bit mode)
    pin_set(0, 0, 0, 0, 1, 1, 0, 0, 0, 0);
    pin_send();
    delayMicroseconds(37);

    // display on
    pin_set(0, 0, 0, 0, 0, 0, 1, 1, 1, 0);
    pin_send();
    delayMicroseconds(37);

    // entry mode
    pin_set(0, 0, 0, 0, 0, 0, 0, 1, 1, 0);
    pin_send();
    delayMicroseconds(37);

    // write data
    pin_set(1, 0, 0, 1, 0, 0, 1, 0, 0, 0); // H
    pin_send();
    delayMicroseconds(37);

    /* this keeps going */
}

void pin_set(int rs, int rw, int d7, int d6, int d5, int d4, int d3, int d2, int d1, int d0) {
    digitalWrite(RS, rs);
    digitalWrite(RW, rw);
    digitalWrite(D7, d7);
    digitalWrite(D6, d6);
    digitalWrite(D5, d5);
    digitalWrite(D4, d4);
    digitalWrite(D3, d3);
    digitalWrite(D2, d2);
    digitalWrite(D1, d1);
    digitalWrite(D0, d0);
}

void pin_send() {
    digitalWrite(E, HIGH);
    digitalWrite(E, LOW);
}

As a test I tried to replace the first delay with this function that waits for the busy bit to be 0.
void waitFree() {
    pin_set(0, 0, 0, 0, 0, 0, 0, 0, 0, 0); // reset pins

    for (int i = D0; i < NPINS; i++) // set all data pins to input mode
        pinMode(i, INPUT);
    digitalWrite(RW, HIGH); // set read/write pin to read
    pin_send();

    while(busy)
        busy = isBusy();

    digitalWrite(RW, LOW); // set read/write pin to write
    for (int i = D0; i < NPINS; i++) // set all data pins to output mode
        pinMode(i, OUTPUT);

}

int isBusy() {
    return digitalRead(D7);
}

But this outputs 1 every time I read pin D7, I'm very new to this and I'm lost to what I might be doing wrong.
Thanks in advance!
EDIT:
I changed the function to set the E pin high instead of pulsing high and low but I still get 1 when I read pin D7.
void waitFree() {
    pin_set(0, 0, 0, 0, 0, 0, 0, 0, 0, 0); // reset pins

    for (int i = D0; i < NPINS; i++) // set all data pins to input mode
        pinMode(i, INPUT);
    digitalWrite(RW, HIGH); // set read/write pin to read
    digitalWrite(E, HIGH); // <--- EDITED

    while(busy)
        busy = isBusy();

    digitalWrite(E, LOW); // <--- EDITED
    digitalWrite(RW, LOW); // set read/write pin to write
    for (int i = D0; i < NPINS; i++) // set all data pins to output mode
        pinMode(i, OUTPUT);

}


texts: why high frequency are blocked by walls but allowing low frequency?

texts: I recently came across the idea that walls block high frequency signal but it allows low frequency signal. Could anyone explain what is the frequency response of walls and what factor in wall modifies the frequency?


texts: What kind of JST connector will fit this stepper motor?

texts:
I'm not familiar with JST connectors so please bear with me. According to the datasheet (here) this stepper uses a JST S11B-ZR female connector.

1) I'm confused since based on my understanding, S11B refers to the number of leads (11), but this stepper requires only 6. Is the male part also 11 leads but with just the 6 relevant leads connected?

2) Are there complete JST connector+cable assemblies for sale that I can just plug and play without needing to crimp my own?

3) Failing that, isit possible to simply hookup standard 2.54mm pitch jumper wires to the stepper JST connector?

Thanks!


texts: arduino + optotriac based ac dimmer blinking severely

texts:
I try to build a dimmer with arduino phase control and triac.
I followed the schematic from

http://www.instructables.com/id/Arduino-controlled-light-dimmer-The-circuit.

Now I used the software provided in the instructable link, but it is not working as it should.
The light is simply blinking instead of dimming.
So I used the following software to just glow the bulb without dimming:

unsigned int i=1;
void setup() {
    Serial.begin(9600);
    pinMode(AC_pin, OUTPUT);
    pinMode(11, OUTPUT);
    attachInterrupt(0, light, RISING);
}

void light(){
    i++;
    digitalWrite(11, LOW);
    delayMicroseconds(10);
    digitalWrite(11, HIGH);
}

void loop(){
    if(i%100==0){
    Serial.println("100");
    i=1;
    }
}

Following are the results:
In the above code I am testing the zero crossing circuit just by counting upto 100, and printing a value (100) when it turns hundred. When i run the system without load (pin 11 is not connected to opto triac) it gives me almost perfect print rate of 1 per second (visibly) and steady. Now if i connect pin 11 to opto triac 3021, the output load bulb starts blinking (not steady at all), and also the output of optocoupler (4n25) gets randomized; Visibily i can see it is not giving output at every 1 second, rather it is somewhat random.
Please note instead of MOC3021 i am using EL3021, and in place of TIC206 triac i used bt 136. I am not using any snubber right now.
I also tried the software from http://wiki.dxarts.washington.edu/groups/general/wiki/4dd69/AC_Dimmer_Circuit.html. Still with no luck however their schematic is little bit different in terms of biasing but i am using exact values from the schematic attached.
Please help me sorting out this problem.

Thanks in advance.
Debojit


texts:
In a board which incorporates a Sub-1GHz transceiver (CC1310) I want to add a chip antenna. I found out that this anntena suits very much to my chip.

https://www.johansontechnology.com/datasheets/antennas/0900AT43A0070.pdf

I scrutinized the datasheet but I wasn't able to find in what rules the antenna's tail trace must be routed. There's a recommendation layout at the page 2 of 8 and an alternative of it at page 7 of 8. But, regarding theirs shape, I can't spot any relation between them. Besides that, the length doesn't seem to be the same.

Although, I searched a lot through the internet, I haven't found anything regarding that "tail trace". How am I suppose to re-route that tail in my board if I can't afford the space to make it looks exactly like the datasheet?

Has anyone ever seen similar design like this?


texts: Power consumption of Inductive Capacitive load?

texts:
I came across the concept of Apparent Reactive and Real power. It says ideal inductive and capacitive circuits do not consume any power.
So my question is - Do inductive motors consume any power at all? Of course they do .. Then how is that true?


texts: Why are switchers more efficient than linear regulators?

texts:
It is well-know that switching regulators are more efficient then linear regulators.  I also know that linear regulator have to dissipate the difference between the input voltage and output voltage times the current as heat.

But why does this not apply to switching regulators with the same conditions: same input voltage and output voltage and current?

I know switchers can get hot; I have one on a board that gets so hot you can barely touch it, but then again it's only 2 1/2 millimeters on each side and looks like an ant compared to a through-hole 7805 with its heat sink.


texts: Looking for ideas. We have a product that has a 4 hole, 0.1" pitch standard through hole pads (normally for a 0.1" pin strip) however, we need to make a cable up for it, that, in most cases wont use it hence the pin strip is non fit. My question is does anyone know of a "male" 0.1" pitch, 4 way 'plug' that could snap into those holes. Like a debug fitment, like pogo pins but self retaining, and cheap. Essentially a connector that has a standard 4x0.1" pin strip throughhole footprint as its mating connection.


texts: Did I ruin my multimeter with a current measurement?

texts:
I am trying to do a current measurement.

Probably I accidentally put it it parallel instead of in series.

What I tried before/after that (cannot remember exactly putting it parallel but might have happened likely) :

Used both connection with 10A and normal output on the multimeter.
Use all settings for current (200 mA, 20 mA, 2 mA, 200 uA)

I put it in series with a LED. When using the normal output the LED is off (open circuit), when using the 10A output the LED is on (closed circuit).

I get always 0.000 A (even when the LED is on and put it in series).
Did I ruin my multimeter?

The ohmmeter and voltmeter still works.

Below a picture of my multimeter (found on internet, exactly similar):


texts: Very long PCB trace causing microcontroller to wakeup?

texts:
I have a design where I'm using an ESP32 as the device's main controller. The system is battery powered, so the ESP is in deep-sleep a lot. It can be woken up with a simple button push (detecting for a falling edge, on one of it's "RTC GPIO").

The circuit for the button is pretty standard:

Pull-up for valid state, and an RC filter for debouncing. The RC filter is after the pull-up, as to ensure there isn't a voltage divider formed between the pull-up and the filter resistor to the button ground side when the button is pushed.

However, something weird has been happening. I've noticed a few times my device is randomly waking up. I've had a google and I can't seem to see any complaints on ESP forums about the deep-sleep being unreliable and randomly waking up after X amount of time, so it must be something unique to my design.

The PCB trace for the button is essentially a stub (the pull-up and RC filter are located right at the button), and the trace itself is over 150mm long. I'm no EMI expert, but my inkling is telling me there's a chance this is picking up noise (capacitively, inductively, or even as a far-field antenna) and potentially causing the ESP to wake-up. Is this a crazy thought to have? It is a four layer board with top and bottom ground fills as well, so I would have thought the trace is somewhat "shielded" and with decent parasitic capacitance to GND - but maybe not.

After I had this inkling I moved the devices from my work bench (plenty of Wi-Fi, 50Hz, and AC-DC wall adapter switching stuff around even with bench-top devices turned off) into my room for the day while I was out of the house. Just sitting there laying on my bed. And, lo and behold, in 8 hours none of them turned on. This could be total coincidence though - that's why I just wanted to get a second opinion.

Thanks! :)


texts: Understanding this part of an automotive wiring schematic

texts:
I'm trying to figure out this part of a wiring schematic for a car's rear wiper assembly, but I am confused by the circled part that shows two prongs sticking out and a dash line going to their top. What is this and how does this work?

Voltage at terminal C is always 12V, voltage at B is always 0V. While the wiper relay is open and the motor is not working, the voltage at A is 0V. It goes to 12V when the motor is spinning.


texts:
I have a custom PCB (based heavily on the Nucleo board) using the STM32F767II. I am using Atollic TrueStudio on Windows 10 and programming it through the ST-LINK on the Nucleo board (header CN6). I have set all the jumpers and connected my PCB to the Nucleo.

I was testing some minor firmware changes and re-programming the board three or four times successfully before I suddenly just got the error "USB communication error". I have double-checked that my wiring is the same as on the previous successful times. I get this error in Atollic TrueStudio and when I try to connect to the board from ST-LINK Utility.

To my knowledge I followed the same procedure for programming the board on all my attempts, so I am confused as to why it suddenly fails now. Are there debug settings or configurations in Atollic TrueStudio that could prevent me from being able to reprogram a chip? Is it possible to recover the chip?

I am also powering my board separately from the programming interface, so would it matter if I connect the Nucleo to the board before I power the board? Could I damage it by doing that?

Thanks!


texts: Digital Potentiometer as PWM Control Input

texts:
I'm a programmer who's been put in charge of some motor control problems and I need your help, apologies in advance for the very professional drawing.

Anyway, what i have is a PWM control board controlled by a 10K MCP-41X1 digital potentiometer with a 75 ohm wiper resistance. A mechanical 10K pot works fine (although the behavior is more on/off either/or 0 or 12V rather than continuously varying the speed, which is what I want to do) but the digital pot doesn't seem to have much effect at all -- in fact, at its lowest setting, the PWM output stays at 12V and doesn't drop at all.

Assuming that I verified that my setup was correct and that the digital pot/Arduino setup was operating properly, I would like some insight as to why the mechanical pot at least was able to turn the DMM reading down to 0V while the digital pot was not.

Any assistance in this matter is much appreciated in advance!


texts: Thevenin Equivalent does not seem equivalent for me

texts:
The application of Thévenin theorem should give a equivalent circuit in terms of current and voltage of any linear circuit consisting of independent sources and resistances.

Given this sample circuit:

The voltage drop between A and B is \$50 V\$. We calculate the Thévenin equivalent between those ports:

\$V_{th}\$ is \$50 V\$, the same voltage drop that we had between A and B in the initial circuit.

Given that in the second circuit we also have a resistance with more than 0 ohms the voltage drop between A and B will not be \$50 V\$, being not equivalent.

What I am doing wrong? Which concept is escaping to my mind?


texts:
I'm helping my dad build a model railway and unfortunately he doesn't have the space to build a full oval for his trains to run around, so we've built a u-shaped track for them to run end to end.
I figured out a way to stop and reverse the trains automatically using a couple of relays and I've wrote a simple arduino code to control it with timing delays.
This works fine but it's not the most accurate thing and its difficult to set it up so that they start and stop from the same positions. I have a couple of the HC-SR04 sensors and was wondering if anyone had any suggestions for using two of these to start and reverse the trains from either end in the same way.
I've programmed a single sensor before but I'm unsure how to incorporate multiple sensors in order to change outputs like that.

Thanks in advance

My timing code:

int relayPin1 = 8;
int relayPin2 = 7;
int relayPin3 = 6;
int relayPin4 = 5;

void setup() {
  // put your setup code here, to run once:
pinMode(relayPin1, OUTPUT);
pinMode(relayPin2, OUTPUT);
pinMode(relayPin3, OUTPUT);
pinMode(relayPin4, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:

digitalWrite(relayPin1, LOW);
digitalWrite(relayPin2, LOW);
digitalWrite(relayPin3, LOW);
digitalWrite(relayPin4, LOW);
delay(2000);
digitalWrite(relayPin4, HIGH); //direction relays changed
digitalWrite(relayPin3, HIGH);
delay(2000);
digitalWrite(relayPin1, HIGH); //power relays set, train moves forward
digitalWrite(relayPin2, HIGH);
delay(10000);
digitalWrite(relayPin1, LOW); //power relays reset, train stops
digitalWrite(relayPin2, LOW);
delay(2000);
digitalWrite(relayPin3, LOW); //direction relays changed
digitalWrite(relayPin4, LOW);
delay(2000);
digitalWrite(relayPin1, HIGH); //power relays set train moves in reverse
digitalWrite(relayPin2, HIGH);
delay(10000);
digitalWrite(relayPin1, LOW); //power relays reset train stops
digitalWrite(relayPin2, LOW);

}


texts:
I've recently picked up a head unit for my car and I am trying to get a HDMI signal to it. I've taken it apart and had a look at the hardware, and it seems to be using a single ribbon cable to drive everything.

I then managed to find the schematics online for it, and it's using LVDS to drive it.

The part number of the LCD screen seems to be YA101B6042-C6.
Can anyone suggest a driver board that would be suitable for me to use? Of course, I will most likely need to build my own breakout PCB so I can route the FPC ribbon to the correct pins as well as design a switching circuit so I can switch between the HDMI input and original car head unit input, but for getting this project underway a driver board would be good for a place to start.
Thanks.


texts: How to Modify LED panel’s power board to turn it on/off using Arduino pro mini

texts:
I’m a software developer and beginner in electronics.

My objective:

I want to modify,
https://www.amazon.com/Ulanzi-Ultra-Bright-Video-Light/dp/B0757KCWGW

LED panel product in a way so that the on/off function(Physical Switch present at the top right corner) is controlled by arduino pro mini 3.5V version.
By the way, this LED panel is powered by 4xAA battery too.

I also want to power the arduino pro mini (3.v) from same battery source.
Please consider that I want to add a Bluetooth module to this arduino later to control from a phone camera app to use the LED panel as camera flash
(I have tested this step in another project already and no issues).

What is the best way to turn the this LED panel on/off considering my requirements above?


texts:
I'm trying to understand how the auto bi-directional voltage translators work.

Background:

I have to choose a part that can translate signals in both directions between 1.8 and 3.3 volts. However, there is a wide selection of components that does this and perhaps anyone would work. But I want to understand how they work, so I was watching this TI video where they use at least 3 different methods with Only Push-Pull, Open-Drain and PP. Later in the video they state that Only PP (i.e. the TXB series)  may not always work.

What are the use cases/scenarios when it would not work?

I believe that understanding the PP vs. OD, and how the bi-directional properties are determined, would help me understand what I really need. So my question is:

How does an auto bidirectional voltage translator work?

I've also looked at the following SE-EE post, but did not find it helpful in my case.

How does a bidirectional level shifter work?

(It doesn't seem to explain how the direction is determined.)


texts: blinking LEDs with PIC16LF1829 with frequency of 1 second in Assembly Code

texts:
New learner on Microchip. I'm now trying to make the PIC16LF1829 to make the four LEDs blink in a frequency of 1 time/second. My intention was modify the oscillator frequency at different positions of the code with fixed amount of instruction cycles to approximate that '1 scond'.

At first, all I have is the command with 197,376 instruction cycles. Since those amount of cycles running in 500KHz of oscillation freq would last four about 1.5 seconds, I intended to use several higher frequencies such as 1MHz and 4MHz to approximate that '1 second'.

This makes me to modify the oscillator frequency at different positions of the code. However things turned out that when adding the same command like:

    movlw   0x5A
    movwf   OSCCON

the LEDs takes twice as long as before.

Can anyone help me figure out what's wrong with this?

Below is the code I have:

#include <p16f1829.inc>
 __CONFIG _CONFIG1, (_FOSC_INTOSC & _WDTE_OFF & _PWRTE_OFF & _MCLRE_OFF & _CP_OFF & _CPD_OFF & _BOREN_ON & _CLKOUTEN_OFF & _IESO_OFF & _FCMEN_OFF);
 __CONFIG _CONFIG2, (_WRT_OFF & _PLLEN_OFF & _STVREN_OFF & _LVP_OFF);
    ORG     0
    errorlevel -302     ; suppress the 'not in bank0' warning
    cblock  0x70
      Delay1
      Delay2
      Count
    endc

Start:
    banksel OSCCON      ; Select bank1
    movlw   0x5A        ; running at 1MHz
;   movlw   b'00111000' ; set CPU clock speed
    movwf   OSCCON      ; set the clock frequency of 2MHz
    bcf     TRISC,0
    bcf     TRISC,1
    bcf     TRISC,2
    bcf     TRISC,3
    banksel LATC
    clrf    LATC        ; set all the LEDs off
Timelag1:
    movlw   0x5A
    movwf   OSCCON
    decfsz  Dleay1,F
    bra     Timelag1
    decfsz  Dleay2,F
    bra     Timelag1
Timelag2:
    movlw   0x6A        ; 4M
    movwf   OSCCON
    decfsz  Dleay1,F
    bra     Timelag2
    decfsz  Dleay2,F
    bra     Timelag2
Main:
    bsf     LATC,0      ; turn on the LED-0,with 4MHz
    bcf     LATC,1
    bcf     LATC,2
    bcf     LATC,3
    decfsz  Dleay1,F
    bra     Main
    decfsz  Dleay2,F
    bra     Main
Main_1:
    movlw   0x5A        ; 1M
    movwf   OSCCON
    decfsz  Dleay1,F    ; prolong the time with another 1MHz
    bra     Main_1
    decfsz  Dleay2,F
    bra     Main_1
    end

Best Regards,

Simon


texts:
I'm hoping that you friendly and knowledgeable folk can help me finally figure out how I should be wiring up my LEDs in my panels.

Just a short history...

Many years ago I took over a panel building department which was in a dire state. I have managed to turn it around now having correct wiring diagrams, CE conformity, etc, etc.

I build 3 phase panels for use in the chain hoist industry and each panel has a 'handset' which controls the hoists. Each 'channel' on the handset has a toggle switch and bi-colour LED to show the direction chosen, green for up and red for down. Now ever since the dawn of time, we have fitted an AC transformer in the panel which sends 24v AC and a 0v down to the handset which goes to the toggle switches and also the LEDs.

On each toggle switch, we solder a resistor which then feeds both legs of the LED.

Now my question....

As far as I am aware it's unusual to power LEDs with an AC supply.  Primarily they prefer DC. I am assuming the use of the AC power supply was because of the very long distances these handsets have been used in (some over 100 meters) and thus the AC works better.

I wish to ditch the AC transformer and fit a DIN mounted 5amp DC unit.

My question is though, will I still have to fit the resistors? I know they should be needed to smooth out the current going to each LED but just wanted to check.

Below are links to the LEDs and resistors I use in case anyone wants to check the specs.

LEDs

Resistors

I hope you can help me gain more of an understanding of LEDs.


texts:
How is the loop bandwidth of a PLL calculated?
Is it the area under the Transfer Function vs. Frequency plot?


texts: Inverse Laplace transform of double pole

texts:
Given the simple transfer function of a double pole:

$$
H(s)=\frac{1}{(1+as)^2}=\frac{1}{1+s2a + s^2 a^2} = \frac{1}{1+s k_1 + s^2 k_2}
$$

Its inverse Laplace transform is (e.g. [1]):

$$
h(t) = -\frac{\cdots}{\sqrt{k_1^2 - 4 k_2}}
$$

The expression in the root becomes zero and hence h(t) undefined.
The system is perfectly stable and legit.

I thought maybe there are multiple expressions going to undefined values such that I need to invoke de l'Hopital. However this is not the case.

What am I missing?

[1] http://www.wolframalpha.com/input/?i=inverse+laplace+transform&rawformassumption=%7B%22F%22,+%22InverseLaplaceTransformCalculator%22,+%22transformfunction%22%7D+-%3E%221%2F(1+%2B+s*k1+%2B+s%5E2*k2)%22&rawformassumption=%7B%22F%22,+%22InverseLaplaceTransformCalculator%22,+%22variable1%22%7D+-%3E%22s%22&rawformassumption=%7B%22F%22,+%22InverseLaplaceTransformCalculator%22,+%22variable2%22%7D+-%3E%22t%22&rawformassumption=%7B%22C%22,+%22inverse+laplace+transform%22%7D+-%3E+%7B%22Calculator%22%7D


texts:
In a typical ASIC design cycle, how much time is taken by an EDA tool to complete the routing?
Assume a fairly complex chip (like the Ivy Bridge). I've heard the entire chip design cycle is typically an year or so, what I want to know is the time taken for the routing (or placement & routing). I was told that it is of the order of several weeks, so I wanted to verify with someone who has some industry knowledge. :)


texts: Does a solenoid valve allow continuous run-time for very long durations?

texts:
I have a bunch of A4F010-06-BS-DC24V solenoid relays.

Can I use them on a continuous duty-cycle like certain relays or are they meant to be used only for certain duration at a time?

I'm worried about burning out the solenoid coils.

The original data sheet seems to be Japanese.

  I have one more question which could be slightly off topic. I tried removing the solenoid connection part which were held by two screws. All I could see apart from the two screw holes was small 3 holes. I thought these solenoid valves actually had some "valves" that opened under magnetic field when activated. I was quite surprised when I noticed the inside with the solenoid to just have 3 holes and how does it control. When I tried connecting to a 24V DC I didn't see any visible movement apart from the click. Do you have any idea how it might be working?

The part with the red circle shows the tiny 2 or 3 holes I was talking about.


texts: MOSFET as a switch failed after 200k cycles - root cause?

texts:
The following is a schematic for a solenoid that failed after ~200k cycles.
I found that the MOSFET drain to source failed short. I am getting~ 26 ohms resistance.
The way this circuit works is as follow:
SW1 is a microswitch that gets cycled mechanically (one cycle is when the switch moves from NC to NO then to NC) when that happens, the solenoid turns off after ~45 ms delay it then turns on again.
I have removed the dead MOSFET and simulated a ground removal (MOSFET turning off). The scope screen shot is captured below. You could see a very fast pulse of almost 84 V with a 54 ns rise time.
The MOSFET drain-source max rating is 100 V.
What could have caused the MOSFET failure specially after so many cycles and how I could make this circuit more robust?
Mosfet datasheet link:
https://www.diodes.com/assets/Datasheets/DMT10H009LK3.pdf
Looking forward to your feedback. Thank you in advance.
TVS1 Datasheet
TVS2 Datasheet link:

Updating the MOSFET Turn off time scope shot
It takes about 7ms to turn off the mosfet.

SOA
The Solenoid initial draw is ~ 1.5A


texts: What is the purpose of the resistor between the Vcc and discharge pins in the astable 555 timer?

texts:
In a standard astable configuration of the 555 timer, we have two resistors R1 and R2. The capacitor charges through both resistors but only discharges through R2, consequently, the high interval is longer than the low interval.

I am having trouble understanding the purpose of R1 here, won't removing it make the charge and discharge times equal, effectively making it a 50% duty cycle?

I tried following this question, but the answers there is not comprehensive enough. Moreover, other resources I came across states that the resistor is essential and can't be removed. Other than changing the ratio between the low and high interval, why is R1 essential?


texts: Can Silkscreen Go Directly Onto Copper PCB Layer? (No SolderMask)

texts: Hi I am wondering if a PCB silkscreen layer can be printed directly onto a copper layer without a solder mask. I don't see this often but I have a design for which this would be useful. Has anyone done this?


texts: Find current and VAB with Superposition Theorem

texts:
Struggling to solve the following circuit with superposition theorem...

I know I need to examine the circuit with each battery in isolation but I am confused how to treat all the resistors as they are all in parallel. Thanks.