texts: How much current is a powered-down ATtiny84 supposed to take?

texts:
I know this sounds like a stupid question, but I'm wondering if the datasheet has an error or something.

I have an ATtiny84 connected to my bench power supply set for 3 volts. It's fused for the internal 8 MHz RC oscillator and a divide-by-8 clock. No watchdog, no brown-out detector.

8 of the I/O pins are hooked to LED anodes, with the cathodes grounded through 0 ohm resistors (yes, the duty cycle is low. Fear not). One of them is connected to a button with the other side grounded. Two of them (shared with MOSI and SCK of the ISP) are not connected (other than to the ISP which is itself disconnected for this test).

setup:

void setup() {

  power_adc_disable();
  power_usi_disable();
  power_timer1_disable();
  ACSR = _BV(ACD);
  set_sleep_mode(SLEEP_MODE_PWR_DOWN);

  pinMode(BUTTON_PIN, INPUT_PULLUP);
  pinMode(UNUSED_1, OUTPUT);
  digitalWrite(UNUSED_1, LOW);
  pinMode(UNUSED_2, OUTPUT);
  digitalWrite(UNUSED_2, LOW);
  for(int i = 0; i < 8; i++) {
    pinMode(LED_PINS[i], OUTPUT);
    digitalWrite(LED_PINS[i], LOW);
  }
  while(1) sleep_mode();
}

The result is 240 µA of current draw. This is measured with a µCurrent Gold, so I have some confidence in the accuracy.

The datasheet (figure 21-1) says that powered down at 25°C the chip should take more like 100 nA.

WTF?

For reference, here's the actual sleep function used by the code (but not part of this test):

void sleepNow() {
  // All LEDs off
  for(int i = 0; i < 8; i++) {
    digitalWrite(LED_PINS[i], LOW);
  }
  cli();
  power_timer0_disable();
  PCMSK0 |= _BV(PCINT5);
  GIMSK |= _BV(PCIE0);
  sleep_enable();
  sei();
  sleep_cpu();
  sleep_disable();
  PCMSK0 &= 0xff ^ _BV(PCINT5);
  GIMSK &= 0xff ^ _BV(PCIE0);
  power_timer0_enable();
  button_debounce_time = millis();
  ignoring_button = 1;
  place_in_pattern = -1;
  milli_of_next_act = 0;
}

It yields the same current consumption, which is why I reduced this test down to just putting the chip to sleep in as little code as possible.

The schematic:

For this test, the battery is absent and 3.00 volts is being fed in to the Vcc and GND pins of the ISP header. No other ISP pins are connected.

I've repeated this experiment with an ATTiny85 on a breadboard. I programmed it with this:

#include <avr/sleep.h>
#include <avr/power.h>

void setup() {
  PRR = 0xff;
  set_sleep_mode(SLEEP_MODE_PWR_DOWN);

  pinMode(0, OUTPUT);
  digitalWrite(0, LOW);
  pinMode(1, OUTPUT);
  digitalWrite(1, LOW);
  pinMode(2, OUTPUT);
  digitalWrite(2, LOW);
  pinMode(3, OUTPUT);
  digitalWrite(3, LOW);
  pinMode(4, OUTPUT);
  digitalWrite(4, LOW);
  while(1) { sleep_mode(); digitalWrite(2, HIGH); }
}

void loop() {}

I then fused it for a 1 MHz internal clock, and then disconnected everything but power and ground. The result: 240 µA.

Now, all of this would be explained if the graph in figure 22-11 (this is the ATTiny85 datasheet now) had the axis mislabeled and was actually in mA rather than µA. The power down current vs Vcc and temperature that I'm using lines right up with the graph 3 orders of magnitude higher.

Has anyone gotten an ATTiny to draw less than a micro-amp (other than just disconnecting power)? Can someone write a sketch that will make an ATTiny do nothing but just go permanently to sleep consuming as little power as possible with nothing connected except power and ground? That's what I've been trying to do, and there clearly is something that I'm missing and I'll be damned if I can figure out what it is.


texts: Detecting static objects in view using RADAR

texts:
Why is it difficult to detect static objects using a 24 GHz RADAR system in cars particularly at high speeds ? static objects could be a stationary vehicle, a police barrier, a animal on the road or a dead end like a wall or tree etc...
It is easier to detect a moving vehicle than the static object. Why is that so ?
Considering both moving and stationary object will reflect back RADAR pulses.
The RADAR system is a Front Collision Warning System installed in the front of the car.


texts:
I have noticed that when, for example, \$cos(t)\$ is in-phase (I) component of the modulated signal, we can determine the phase from the constellation diagram measured counterclockwise from the horizontal axis.

However, when, for example, \$sin(t)\$ is an I component of the modulated signal, we can no longer determine the phase as described above. How can we determine the phase from the constellation diagram in such case? Or am I missing something?


texts: Theoretical question: Could an incandescent light bulb be used as a temperature sensor?

texts:
Let's assume a plain old incandescent light bulb.
It runs on a fixed (assuming an ideal supply grid) voltage and will regulate the current going through it as its resistance raises with the temperature until it reaches some kind of equilibrium.
Then we could assume the external temperature would affect the bulb, and its filament, which would in turn affect the current going through the bulb, to keep things in balance.
Therefore, I question if we could measure the outside temperature by measuring the current going through the bulb?
This is a theoretical question that piqued my curiosity.


texts: Brushless motor specs to maximize stall torque

texts:
I'm interested in a brushless motor having a high stall torque (not much in RPM).

What specifications of a BL motor would give a fair indication of its stall torque, provided that

voltage is fixed ( 12V )
current is also fixed ( say 10A max )

I'd like to identify quickly from a list of motor specs (found on the Net) what to expect from a torque point of view.
For instance, number of poles, kv, weight, diameter, length...


texts: Why do we need a ramp for stepper motor?

texts:
I am a newbie and trying to understand how i can run a stepper motor. The concept i had in mind was that steppers need digital pulses to run, and i tried it out too. I was able to run the stepper i am using very easily. But lately I came across a link where they have used a ramp for starting a stepper justifying it by saying that

"if we try to start the stepper motor with fast pulses then it just sits there and hums away not turning, We need to start the stepper off slowly and gradually increase the speed of the steps (ramping up)."
Source:http://www.societyofrobots.com/member_tutorials/book/export/html/314

My question is why does the stepper then starts up with regular square pulses? Why do we need a ramp? All the other forums and tutorial always talk about providing digital pulses to the stepper for starting it up, why is the concept of ramp generation not discussed there? Is it a bad practice to run stepper with digital pulses?


texts: Output port is becoming "uninitialized" in GLS (VHDL '93)

texts:
I have a block inside a top_block, and it's output is connected to the output port of the top_block. Both have a data type of std_ulogic_vector(15 downto 0).
In RTL simulation, the output port of the top_block is getting the correct values. But in GLS, that output port is becoming "uninitialized"... So I tried to do some experiment and changed the data type to std_logic_vector and the issue has been solved.

Now, I don't know what happened. I'm not sure if this is the correct solution to the problem since I can't explain why it is working. So, kindly help me to analyze what happened here and if this is the correct solution to the problem. What is happening during GLS that causes this issue?

Take note that it is just simply connecting the output port of the sub-block to the output port of the top block. The output port of the sub-block is working fine but the wire connecting it to the output port of the top block is "unitialized".


texts: Extracting speaker, microphone and hook signals from a two-line telephone

texts:
My aim

I'd like to use a 'normal' telephone as an audio and switch interface for a project. I want to design a circuit that has the telephone A and B wires on one side (ie. an RJ-11 socket) and has four connections for my other work on the other:

Receive a high/low signal as to whether the phone is on or off the hook
Receive the audio being spoken into the phone's microphone (only needed when the phone is off the hook)
Send an audio signal which will be delivered through the phone's speaker (only needed when the phone is off the hook)
Send a high/low signal for whether the phone should ring (only needed when the phone is on the hook)

I've been reading some old usenet posts but my electronics engineering days are a long way in my past, I can't quite decipher what I should be building. Can anyone help?

I've put a representative schematic below.

simulate this circuit – Schematic created using CircuitLab

What I think I know

The speaker/mic

I think I can split out the speaker/mic signals like this

simulate this circuit

The ring

I think I'm also going to need an inverter in this circuit, to generate the 75vRMS 25Hz AC signal to power the ringer (UK ring is 0.4s on, 0.2s off, 0.4s on, 2 sec off).

I still need to digest this inverter circuit, but I can probably figure out the components I'd need for the above (though I'd probably have difficulty isolating it properly)

The off-hook detection

I don't know if I need to generate the 50V base voltage that a telephone network usually provides — I imagine this requirement will come from being able to detect if the phone is off the hook or not.

Where I need your help:

I don't know how I'd stop the ringer signal from impacting the mic/speaker setup
I don't know if anything above is very wrong

Does anyone have any advice?


texts: Using a battery charger instead of a battery?

texts:
I have built a simple circuit with two diodes that light up intermittently. It requires 9V DC voltage to run.

I don't have a DC source at home, and would like to avoid buying 9V batteries repeatedly to power my future projects, as portability is not necessary.

I however have a battery charger (wall adapter with battery slots), which can also recharge 9V batteries. I thought that battery powered devices are often able to run plugged in without the battery, so this should be the case here, too.

So I tried to connect the wires where the 9V battery to-be-recharged would normally fit, but it's not working as expected: D2 stays on indefinitely, while D1 flashes for a brief moment about once a second.

Note: The charger has a led indicating whether the battery in the respective compartment is charging. It does NOT light up when the circuit is connected.

Normally, they are supposed to flash intermittently, about one second each.

(The circuit works correctly, tested with a 9V alkaline battery).

I don't understand why this happens, and would greatly appreciate some help!


texts: How to derive voltage applied to an antenna, where transmitter power is known & identical tx/rx antennas are used with known gain/impedance?

texts:
Question:

Imagine a transmitter + transmitter antenna with the following characteristics:

433Mhz transmitter transmitting 10dBm
Into an impedance matched (50 ohms) antenna, omni-directional, 3dBi gain

And a receiver:

50 ohm impedance antenna, receiver circuitry presents 50 ohms
Receiving antenna is an identical 3dBi omni-directional antenna.

How would I go about calculating the voltage the receiver circuitry would see? I'm trying to learn RF electronics by building a detector for a constant 433.92Mhz carrier, and I can't predict how my diode will behave without knowing the voltage applied across it.

My attempt from first principles:

10 dBm is 10mW of power, 3dBi of gain means 10mW X 2 = 20mW radiated from the antenna under ideal conditions.

Based on the inverse square law, we get:

$$
P = { 0.02 \over 4 \Pi r ^2 }
$$

$$
P = { 0.02 \over 4 \Pi 40 ^2 }
$$

$$
P = { 0.02 \over 4 \Pi 40 ^2 }
$$

$$
P = 9.94718394^{-7}
$$

Yipes that seems small.

This is the bit where I get stuck. Can I just multiply it by the receiving gain (3dBi, basically 2x) and sub it into ohms law (with the impedance of the antenna, 50 ohms) combined with the power formula (P = IV)?

$$
P =  ({V \over R})  V
$$

$$
2 \times 9.94718394^{-7} =  ({V \over 50})  V
$$

After doubling the power (because the receiving antenna gives me 3dBi gain) and plugging this formula into Wolfram Alpha to solve, I get ~10mV.

This seems low and I'm not confident with the logic of my derivation. Is this correct?


texts:
I'm inserting new footprint in kicad. I'm not good in mechanics as I should be. When I learned mechanics in school, no one told me how to interpret something like this:

  Number - (Diameter-sign) Number

I want to use dimensions from:

On the right side of picture there are PTH pads with this kind of dimension.

How should I interpret that dimension?


texts: Can I replace a NUP2105L voltage suppressor with a NUP3105L?

texts:
Someone gifted me a device to read electronic control units from cars and trucks. They gave it to me because they don't use it and they have also removed some components from it to fix another device.

I am trying to rebuild it but theres a missing component I am having troubles getting locally (I can't import it because of strict import rules we have where I live will make it hard and expensive to get) is a little smd component marked 27E and it looks like a transistor.

After some googling I found it is a dual bidirectional voltage suppressor NUP2105L. I have no idea what that means, my knowledge in electronics is very basic.

The place where I went to buy it told me they don't have it, but I could replace it with a NUP3105L that they do have. But I decided to do some research to make sure.

So I tried looking at the datasheets (which I barely understand) and the first thing that makes me doubt if it will be a good substitution is that the symbol of each component looks like 4 schottky diodes, but they are pointing in opposite directions.

My question is, would the NUP3105L be a good substitution for a NUP2105L?

If not, is there another replacement I could use to just solder in place of the NUP2105L, without having to modify anything else?


texts:
Using stm32L451 with a Sim7600.
I am trying to post data to a Ubitdots dashboard using HTTP post and the response is 204 which means no data is load but a connection was made to the server, I have managed to post data using this method using the sim800.
This is my method:
AT+CREG?
AT+CGREG?
AT+HTTPINIT
AT+HTTPPARA="URL","https://xxxxx"
AT+HTTPPARA="CONTENT","application/json"
AT+HTTPDATA=284,4000
I send the following data once download appears*
{"Battery" : 10,"Signal" : 45,"HR" : 0, "Panic": 0,"GPS" : {"value": 1,"context":{"lat":-34.0004802,"lng":22.4305863}},"Unit" : {"value": 1,"context":{"value":"Taking asda"}},"Next-Location" : {"value": 1,"context":{"value":"B4"}},"Guard" : {"value": 1,"context":{"value":"Tasdsad"}}
AT+HTTPACTION=1
And from here I am receiving the 204 error. It seems that the sim7600 module is not acknowledging the data I send through.
What am I missing?


texts: strange output of analog amplification stage

texts:
This is supposed to be an amplification stage for a piezo microphone connected on J1.

The "ANLG_PWR" is at 3.0 volts. When probing the output (TP1) the DC output is at 3V.

I figured I had too much amplification and so reduced R6 from its original 1Mohm value to 200Kohm. That did improve the situation and got the output voltage down to 1.84V. When probing both inputs of U2 i get 1.48V.

Why is the DC output voltage not centered around 1.5V like I designed it to be?

I do need the original amplification (about 1:500) but need the DC output to be 1.5V.


texts: 'Dielectric Strength' parameter meaning for cheap inductior coils

texts:
Initially I need an inductor to be used in cheap low-power AC-DC power supply. I'd like to use LNK304 solution:

When I reached 1mH coil I found Bourns 77F coils: very cheap (only 8 cents at some quantities), quite small (11 mm in length). But I need to take into account that this coil should withstand peak AC voltage which can be as great as 350 V (if I consider +10% ACV tolerance). There is a Dielectric Strength parameter in it's specification which is rated for 500 Vrms.

However there are dedicated high voltage solutions like Wurth Electronics HV series. But it is bigger and significantly more expensive (about 2 USD).

Main question: Can I be sure that this cheap coil will have a long and happy live in my schematic?


texts: What is the STM32 "timestamp" feature designed for?

texts:
While browsing the stm32f051xx datasheet I came across this section (p23, section 3.15, Real-time clock (RTC) and backup registers)

  timestamp feature which can be used to save the calendar content. This function can
  be triggered by an event on the timestamp pin, or by a tamper event. The MCU can be
  woken up from Stop and Standby modes on timestamp event detection

As I understand it, this allows you to take a snapshot of the date and time that a pin change occurs either with or without waking up. However, there is no further explanation of this feature, even in the RTC application notes.

I could see obvious uses for this feature if you could save multiple timestamps, or it had sub-second accuracy. However, none of that is available. I assume this feature must be commonly useful to be included, so I'm curious what kind of use-cases this feature was designed in mind with.


texts: How to produce sound when a certain condition is met in proteus?

texts:
I've made a 6-bit counter with 6 JK flip-flops that can count from 1 to 33. After it reaches 33, the circuit will go back to zero. I want the circuit to produce a sound when the counter reaches 33. I tried using SPEAKER and AUDIO SIGNAL GENERATOR but they don't seem to work with logic gates. Is there any way to solve this without using Arduino and scripting stuff?
Here is the circuit:


texts: Have I missed something when connecting this stepper motor?

texts:
I have an Arduino which I am using to control this stepper motor using a breadboard with this layout. I have the Arduino connected to my Mac and it successfully runs, but the "force" of the motor seems to be extremely weak. I have tried running the motor with different speeds but if I hold on to the wheel when its running, it does not manage to run around until I let go of it.

L293D datasheet

Have I missed something in the schematics or when connecting the motor, or is this kind of stepper motor just very weak when it comes to thrust? Should stepper motors that are 100% working give more thrust than just barely touching it with my hand, it does not manage to spin?

When I test the current using a multimeter from the 5V on the Arduino it shows around 640 on the multimeter screen.


texts: How can you read out the serial number of an XMEGA chip in a batch file during programming?

texts:
Each time I download the firmware into an XMEGA I would also like to save the chip's serial number to a batch file so I can keep track of which chips got which version of the firmware.

Is there an easy way to do this?


texts:
I'm using a Matsusada HV Power supply up to 20 kV. The manual mentioned that the ground terminal of the chassis should be connected to earth. And I had a few questions

What are the best, or at least acceptable, ways to make this connection. Would it be OK to connect it to the earth ground in the power outlet? If so, is there some sort of adapter or tool that makes it safe to access the earth ground from the power outlet? I'm wary of poking around outlets.
Is there a reason why the user manual instructs the users to make the earth ground connection? Doesn't the instrument have access to earth ground through the power outlet via the AC power cord? The only reason I can think of is that they don't trust all buildings to be connected properly.

Thanks


texts: Difficulty in reading values Modbus application in Python(Pyserial) On Energy meter (EM6400)

texts:
I am trying to read energy meter(EM6400) voltage values in python by using modbus protocol.
But there are issues when I am reading values. I think the issue is with,
I am not reading values in proper way
i.e. in the line ----->

buf = ser.read(11) # reading 11 bytes from energy meter

Here is detailed of my implementation :

Request:

01 03 0F56 0002 270F
01: Slave address
03: Function code for read holding registers
0F56: Data Address of the first requested register (address for voltage phase1 to neutral)
(0F56 hex = 3927, +40001 offset = 43928)
0002: Total number of registers requested
270F: CRC (Cyclic Redundancy Check) for error checking (LSB first)

Response:

01 03 04 2921 4373 D2B0
01: Slave address
03: Function code for read holding registers
04: Total number of bytes read
2921: Data in 1st requested register
4373: Data in 2st requested register
D2B0: CRC for error checking (LSB first)

Values in required register are 43732921 in hex (since obtained values are being read in little endian format) which is 243.16 when converted to floating point using IEEE 754 norms. Obtained value is a voltage (phase1 to neutral) which is 243.16 Volts.

Here is the code for the same:

import os
import sys
cwd=os.getcwd()
(setpath,Examples)=os.path.split(cwd)
print setpath
sys.path.append(setpath)

from PyArduino import *

import struct

port=locateport()
ser = serial.Serial(port, 9600)

ser.write("\x01\x03\x15\x86\x00\x02\x39\x15")
buf=ser.read(11)

b1=b2=b3=b4=0

a1=buf[3]

if (a1<16):
    b1=1
    a1=int(a1,16)
if (b1):
    a1='0'+str(a1)

a2=buf[4]
if (a2<16):
    b2=1
    a2=int(a2,16)
if (b2):
    a2='0'+str(a2)

a3=buf[5]
if (a3<16):
    b3=1
    a3=int(a3,16)
if (b3):
    a3='0'+str(a3)

a4=buf[6]
if (a4<16):
    b4=1
    a4=int(a4,16)
if (b4):
    a4='0'+str(a4)

a5=[a3,a4,a1,a2];
a6=''.join(a5)

print struct.unpack('!f', a6.decode('hex'))[0]


texts: Transimpedance AMP, Active HPF, phototransistor

texts:
So this is the part where I would like the phototransistor (TEMT6000X01) to be able to clearly capture an LED with a frequency flashing on and off at 1kHz. So what I have here is a transimpedance amplifier (AD823) with Rf at 100k because the typical collector light current for high illumination is 50uA V = 50uA * 100k giving 5V. Would the capacitor be okay for this?

Second I have a high pass filter allowing frequencies from around 995Hz upwards. Does it seem correct?

Thirdly, since the maximum output from the TIA is 5V, is it necessary to have a non inverting amplifier (AD823) to amplify the signal?

Once passed the peak detector, the output will be connected to the Arduino.

What are your thoughts?

Datasheet for TEMT6000X01: https://docs-emea.rs-online.com/webdocs/112b/0900766b8112bb21.pdf

Datasheet for AD823: https://www.analog.com/media/en/technical-documentation/data-sheets/AD823.pdf


texts: Using transistor as switch in the "middle" of the circuit

texts:
I have an rather complex circuit with button micro-switch in the middle (actually, it's RF remote control with 3 buttons).

I would like to be able to simulate the micro-switch click on it with one of the pins from my micro-controller.

To do so, I decided to install transistor in parallel manner. The problem is, micro-switch is neither the last nor the first element in circuit. And as I recall transistor needs to be connected to ground (NPN) and not just "somewhere in the middle".

My non-modified circuit with switch in the middle, between two LEDs (they are there just to make a concept of some "black box" before and after the micro-switch):

When I add an NPN transistor and tries to simulate the switch with it, the current is different:

If remove the part of the circuit that is "behind" switch (to GND), it works as switch simulator just fine:

What should I do in such case, when the circuit is already built, and I want to simulate switch "click" without moving the switch from it's place?


texts:
I am a beginner and I am trying to understand the block diagram of a Static RAM. I want to draw a "256x4 bit SRAM" block diagram. According to some information I collected from the internet I managed to draw a block diagram for a "256x8 bit SRAM" which is demonstrated in the following figure (I am not sure if it is correct):

However,I am a bit confused with the way it works. Could you provide an example about reading or writing data? Which signals are activated, which switches and which gates open and close?

In addition to this, what does determine the number of bits I use for the input of the Row Decoder? I know that for n bits in the input we get 2^n bits in the output of the decoder. So here I get 16 bits. But why do I have 4 bits in the input (A4,A5,A6,A7).


texts: Feedback on converting signal from 3.5mm jack to ADC on STM32 Bluepill

texts:
I'd like some feedback on my circuit. My goal is to convert an audio signal coming out of my laptop's 3.5mm jack (using a sin generator at max volume gives me about a ±1.5V wave) to digital using the ADC on my bluepill. From there, I plan on doing an FFT to control some neopixels. Might also implement a digital equalizer and DAC the signal out to another jack (not sure if the blue pill could handle it in real time but that's a problem for future me).
I'm using the TS5A22364 to switch between the left and right channels on the jack, which saves me from having to clamp both channels. I chose the TS5A22364 because it supports a negative voltage swing. The 0.1uF capacitor is there as a bypass capacitor that the datasheet recommends. For the precision clamp, I was planning on using the LT6015 instead of the LT6106. I'm using a reference voltage of 1.65V to shift up the signal to halfway between 0 and 3.3V, the range of the blue pill's ADC. I chose RC values of 330pF and 1.5M Ohms, because I read somewhere the time constant should be at least 10 times the period of the signal going through, which should be around 0.0005 if I'm expecting up to 20kHz. Is this wrong and if so, how should I go about selecting these component values? Is there anything else I'm potentially not taking into account here?


texts: Small DC voltage boost without step-up boost circuit?

texts:
I have a simple DC circuit (Arduino related) with a USB power supply that's giving me 4.9V.

Is there a way, with minimal components and without using an inductor, to boost that voltage to 5.2V?  I have a sensor that starts being stable right around 5.1v.

I'm looking for a current of around 300mA.


texts: Taking an unstable DC voltage, and stabilizing it

texts:
I have a DC motor generator (basically the motor spins, and it powers an LED at the moment), and the output current (mA range) and voltage is very unstable.

For an entire circuit to run on the motor-used-as-generator's power, is it possible to stabilize the voltage and current of the output. The output voltage must be 5V and I am not concerned with current, no matter how low.

My circuit is made of, literally, a motor and a wheel of magnets.

The motor generates spikes up to a miximum of 0.97V and lowest 0.3V. My plan is to attach multiple wheels, then have three of the three wheeled motors, have theses circuits attached to a op-amp, and then simply charge a battery my multimeter broke, so I can't test the three wheels or the current until I get a new one

The project is for a competition and we need to use minimum number of parts, under 100 individual components.


texts: USB device detection problem on a Raspberry Pi

texts:
I have a device constructed from a Raspberry Pi 3 B and an AVR based USB device. The interconnection of these components is depicted in this picture.

When RPI is on, data lines of keyboard will be connected to the USB port of RPI. When RPI is off and a USB cable from PC is connected to the device, then data lines of the USB keyboard will be connected to that USB port.
The problem is that when using Raspbian Buster, the OS doesn't detect the USB keyboard at all. It isn't listed in dmesg logs nor in lsusb output. I know that maybe this is not the standard interconnection, but I can not change the hardware. And more importantly, this setup works great with Raspbian Stretch.
So, although this detection problem may be caused by the connection architecture, but there must be a software solution because as I mentioned, the USB keyboard is detected and working when the OS of RPI is Raspbian Stretch.
I think the problem lies in the RPI firmware changes that happened from Stretch to Buster, but downgrading firmware using rpi-update didn't help.
What can I do to make the Buster firmware detect this USB keyboard as Stretch does? As I mentioned, downgrading the Buster firmware/kernel from 4.19.57-v7+ to 4.9.35-v7+ (the firmware/kernel version of the working stretch release that I have) didn't help.
If it matters, the USB keyboard is an AVR based CDC device.


texts:
From my understanding the bandwidth of an input signal to an ADC is defined as the range of frequencies the signal consists of, which is calculated as the difference between the highest and lowest frequency within the signal band. So ok, but what about a time to digital converter (TDC)? How can one define the bandwidth here?
A TDC takes in two inputs, usually called Start and Stop signals, and measures the time difference between the two. For example, the input stream might be like this

What does input signal bandwidth mean here?
EDIT
What confuses me is this Sigma-Delta TDC paper  for example. It says:

In the MASH Sigma-Delta TDC, there is also a special relation between
the OSR and full scale input range. The bandwidth of the input signal,
BW, is set to 100 kHz in this design. The sampling clock of the TDC
system is then equal to 2 BW OSR. Due to the input signal’s timing
nature, the peak-to-peak full scale input signal amplitude has to be
smaller than one period of the sampling clock.

Now according to this, if OSR=25, the system clock is found to be 5MHz, which means that the PP FS input range has to be smaller than 200ns.So not sure what the physical interpretation of BW is here.
In another paper I found a comparison table which compares different architectures:

The papers indexed 26 and 28 have the same 50MS/s sampling frequency, but the BW in former case is 10 times more. The FS input range in both cases is more or less the same. Anyway, I cannot turn my head over how or in what manner BW could limit system performance?


texts: When I prepare a double layer DIY PCB using Press-n-Peel I have a problem aligning the bottom and top layer so that the holes and vias match on the copper between layers. Can you suggest any easy method that would minimize the wrong alignment?


texts: Industry Practices for Schematic Design?

texts:
As my designs (and PCB designs too) become more complicated, I'm interested if there are best practices or industry standards for schematic design. I know there's a schematic checklist but I'm looking to go further with my designs. I've been following a simple design methodology based on signal inputs & outputs go left to right, with power flowing from top to bottom, which has worked well for simple schematics. Some of the questions I have thought about but can't find an answer:

What's considered the maximum number of parts on a single page?
What to consider when making a schematic multiple pages?
When should I consider putting multiple tracks into a buss?
How should I name busses, netlists, and the references to other pages?
How should I place components to minimize the number of nets?
What kind of comments should I include on a schematic?
Where should I place the designation and value for horizontal and vertical components? Does it matter as long as I stay consistent?
Should I note component packaging & rating on the schematic? Meaning discrete vs SMD or if a specific resistor is high powered?
Should I customize nets in different colors or widths?
How should I version control schematics?
What workflow should a single person use to keep designs organized?

I'm sure there's more to consider on schematic design, this is just what I've run into with my own work. I'd appreciate additional topics on schematic design too.


texts: I have read that usually a gsm module requires a power supply capable to provide up to 2A. But how can 3g modems sticks work properly when they are powered through usb port which provides only up to 1A(?)


texts: How to read high voltages on microcontroller?

texts:
I want to read high voltages, like ~50V, using a microcontroller. I plan to put this as an input into the microcontroller's A/D line. But of course, you shouldn't have voltage that high on the input of a microcontroller or it'll fry.

How might I read high voltages? The main thing is that I need to step down the voltage before reading it. What do I need to consider when stepping down this voltage?

Thanks in advance!

Edit: I noticed in the PIC18 datasheet that it says "The maximum recommended impedance for analog sources is 2.5 kOhms." How does this affect how I step down the voltage, be it with resistive dividers, etc.?


texts:
I have a ts7800 SBC, and I need to communicate over an SPI bus. In their documentation they say that their is no hardware SPI, and they implement in their sample code "software SPI." For me, this works now but when I view the SPI clock on an oscilliscope, it looks uneven(typically the clock stays higher for a longer period of time than it stays low, but sometimes the opposite). I am worried that when I start adding more threads and code into the mix, the problems with the SPI being software controlled will become more apparent. Has anyone dealt with an issue like this before, and what did you do to correct it? Or was it even an issue?

I would rather not use interupts for the SPI bus because I have just as important (if not more important) processes going on in the other threads.

Thank you for your help.


texts:
I recently built this circuit, and could hear a nice full quieting signal on my short-wave  radio with a 7.2 megahertz crystal for the 40 meter band.

What is the simplest way I could Amplitude Modulate this signal with a microphone or computer output port so my Short wave radio could hear this signal and I could potentially make some HAM contacts?

And by the way I do have a license. It is KDØWHB and I have general privileges.


texts: Kaustic Machine's Atari Punk Console: Line Output or Log Pot?

texts:
I'm planning to make a atari punk console for an electronics project,  but i have a question, the original circuit published here: http://compiler.kaustic.net/machines/apc.html has a "line outout". Is this a suitable way to drive headphones as well? Should i remove this resistor array and replace it with a log pot in series with the 556's output? Or how should I modify the circuit to drive headphones and have some kind of volume control?

Also, is line output that important?


texts:
I am trying to make a load using resistor that can bear 12V 4A rated values.
I have calculated a resistance but that has a low resistance and high power rated resistor i.e. 3 ohms 48 Watt resistor. It is impossible to find this so please help me regarding the load resistance.
Thankyou


texts: Keeping NodeMCU operating with a super capacitor

texts:
Awhile back this post asked about providing 3-4 seconds of power to an NodeMCU subsequenst to a loss of its primary power supply.

Prior Post

I have a similar need except I only need a split second of power.  I tried using a 1000uf capacitor but that did not work.  Is a supercapacitor reasonable to try.

FG0H105ZF

I attached a diagram of the set up.  I am not an EE and apologize if the diagram is not proper form.

The context of the application is a model train getting 18V power from the railroad track. The 18V is stepped down to 5V with a regulator and used to supply the NodeMCU at Vin.  The NodeMCU is used to control the train. When the train passes over a track switch it can interrupt the power for a split second, enough to shutdown the NodeMCU.

I do not want to use a battery to cover the interruption and hoping I can simply insert a capacitor.

One other question.  Assuming the super capacitor works, if the regulator was supplying say 9 volts, would  the immediate drop the 5.5 V of the capacitor be a problem. Te NodeMCU has a a regulator on board and I am thinking it could handle this. Again, the disruption is perhaps 1/10th - 2/10ths of second.

Thank you for your replies.

I am using a Rohm linear voltage regulator. BA50DDoT

I will give the 1000uf a try in front of the regulator.

I will also try the code suggestions.

I did some more digging on power consumption.

for those interested, this video is informative. The second half show the NodeMCU.

Your replies greatly increased my understanding of the power issues.

Thank you all.

YouTube on ESP Power Consumption


texts: Does this digital line-encoding/keying scheme have a name?

texts:
"1" is a single low pulse of length T, followed by a single high pulse of length T

"0" is a single low pulse of length 2T, followed by a single high pulse of length 2T

This is similar to BFSK, except that this scheme only has one full cycle per bit, whether that bit is 0 or 1. For BFSK, the "1" bit would get 2 full cycles, and the "0" bit would get only one full cycle.

I can find a usage of this scheme, in digital model railroads and digital slots cars, where power and data are transmitted through the metal rails in the form of square wave AC.

I've searched high and low, and cannot find any name or other usages of this fairly simple, and quite useful looking keying scheme.


texts: FCC Per Unit Factory Test For Intentional Radiators

texts: Can someone clarify if each unit for an intentional radiator must perform factory emission testing or is this only required for a one time tst in an approved test lab?  Is this tied to a specific  part 15 requirement?  I am involved with a 2.5 GHz low power ISM device.


texts: Unable to get the correct k-map for this finite state machine (Crosswalk System)

texts:
I am trying to create a Crosswalk System using a finite state machine. Although I understand how to do it, apparently I am continuously arriving at the wrong equations for my D inputs since my K-maps are incorrect. I am using 2 D-flipflops for this statemachine. I have tried numerous times and re-did my k-maps but I am still arriving at the wrong equations; apparently, there should be 3 groups for both the D1 input and D0 input. I will post the diagram to the state machine and also my work. All I am asking for is the K-map for the state machine. Here is the diagram below along with my k-map, please let me know where I am doing this incorrectly, thanks:

Link to diagram image for higher resolution:
http://i.stack.imgur.com/zyDb9.png


texts: Strange extra frequency in crystal oscillator

texts:
I have inherited a circuit from another designer using a 12.288 MHz crystal as the source for an audio clock. We recently had supply chain issues and I was asked to approve an alternate part with identical specifications. As part of this I compared an FFT of our "golden sample" unit and the new crystal under consideration.

I was surprised to find that the FFT of both units looked like this:

Here you can see two frequency peaks - one at 12.28 MHz (close to the expected 12.288 MHz) - and another with pretty much identical amplitude at 12.72 MHz. This looks like bad news to me - although the audio output sounds fine to my ear.

Does anyone know what the likely cause of this is? Given that this is used to clock a DSP (which uses it as the audio clock source) are there likely to be negative impacts from this sort of behaviour?


texts: Can a Vienna rectifier or an active front end rectifier regulate the voltage down?

texts:
I learn the basics of rectifiers. In particular, Vienna rectifier and active front end recifier.
As I understand it, both types of rectifiers can work in the mode of increasing the output voltage.
But so far it’s not very clear to me whether they can work in the mode of lowering the output voltage.

Vienna rectifier

I see here six diodes that rectify alternating current and are not regulated by anything. But also with them on each phase there are two MOSFET transistors, which, as I understand it, act as additional "regulated" diodes.
Does this rectifier circuit provide the possibility of lowering the voltage below the level obtained from 6 diodes?

Active front end rectifier

In this circuit, there is already complete control of each of the transistors.
Main questions:

Can these types of rectifiers reduce the output voltage?
Can an active front end rectifier increase the output voltage?


texts: LDO in split supply behaving incorrectly when power supply sequence is "wrong"

texts:
I'm powering an op-amp (OPA657) in transimpedance configuration.  I externally supply ±15V, with LDOs to drop to ±5V; here I omit the feedback loop for simplicity:

When I turn on the negative rail (-15V) first, my positive-regulating LDO (LDL1117S50R) somehow gets exposed to what I measured at -0.8V at the output, highlighted in the below image:

When I then turn on the positive rail (+15V), the LDO doesn't regulate the incoming +15V; the output just sits at -0.8V. The only way to get it working is power-cycling, and making sure the positive rail comes on first.

What is happening? I had an older TO-220 regulator there before and it was fine.

I realize I'm inadvertently exposing the LDO beyond its absolute maximum negative voltage at its output (according to the datasheet, it's  -0.3V). How do I prevent this from happening? I don't want to do any complicated power supply sequencing.

For reference I have snipped the negative rail section:


texts:
I have a few external input probes on a device I'm making which are connected to an ADC. Is there an electrical (i.e. non-mechanical) method of detecting whether the ADC input is floating/disconnected/tristate or actually connected to a signal source, without altering the input signal? The signal should be considered analog; not necessarily a digital logic signal.

The purpose is to ascertain whether the ADC data being read is significant or not, so that the gaps when the probe is disconnected can be noted with respect to time.


texts: Do my specific constraints prevent me from using this Zero and Span Amplifier?

texts:
I am interfacing a thermistor with an ADC, and I have found a circuit that, at first glance, appears to suit my needs.  A zero and span circuit using a single op amp.

http://www.ti.com/lit/an/slyt173/slyt173.pdf  (figure 3, page 3)

The thermistor is in a voltage divider, using a 82k resistor as the fixed resistance.  The thermistor's resistance is 3k @ 212F, and 160k at 32F.  With 5V across the full divider, this gives 4.8V across the fixed resistor @ 212F, and 1.7V at 32F.  I'd like to map 4.8V to 4V, and 1.7V to 0V.

To calculate my required offset and gain, I set up two simultaneous y=mx-b equations:

Vout = m * Vin - b

4.0  = m * 4.8 - b

0    = m * 1.7 - b

Solving for m is as easy as (y2 - y1)/(x2 - x1).
plugging m = 1.2903 back into either equation gives you b = 2.1935.

According to the PDF, the equations for the resistors, as they relate to m and b are as follows:

m = (RF + RG)/RG

|b| = (RF/RG) * (R2/(R1+R2))

If m is roughly 4/3, it follows that RF is roughly RG/3, and RF/RG = 1/3.

A little more algebra, and plugging in b = 2.2 makes R2/(R1 + R2) = 2.2 * 3 = 6.6.

There is no combination of R1 and R2 that can make the quotient more than 1.

Does this mean that this circuit can not perform this particular zeroing and spanning?

If so, what are my options to accomplish this?

Thanks.


texts: Does a simple wire antenna need a 50 ohm transmission line?

texts:
I am trying to make a LoRa board with an RFM95W module.
Using the calculator shown in the image below, I designed a 50 ohm impedance transmission line. I added options for both a monopole copper wire antenna and a proper U.Fl antenna. However, after further research I am unclear whether a wire antenna even needs the 50 ohm. Further, I am worried that if I end up going with the U.Fl, the board trace impedance will add with the connector impedance and create 100 ohms.

(There will be copper pour on the red side)

So do wire antennas need a 50 ohm transmission line? Will the impedance of a 50 ohm transmission line and a 50 ohm ufl antenna connector add to make 100 ohms in series?


texts:
simulate this circuit – Schematic created using CircuitLab
For a specific project , I need to create a Voltage-Current controller circuit that will be able to control the flow of Current and the voltage by using 2 different potentiometers for each.
Here is the schematic I have tried....
TIP122 Darlington for increasing and controlling current, till that it is working fine but
the IRFZ44N MOSFET part doesn't work properly for voltage regulating and I am unable to find a way to fix it.
But this doesn't seem to work.
can anyone please point me out where i have made a mistake?
Explanation with circuit schematic will be much preferred and appreciated.
i need one potentiometer to control voltage and another one for controlling current
NB:
I don't want to use any types of IC for this project so please avoid suggesting one till there is another way/ways left.
Thanks for your precious time.


texts: is it problem if the Voltage at home is 270v

texts:
I recently called an boiler technician, and while he was doing his think,
he noted that the electricity in my house is on 270 volts.
I think the standard for my country is 205 to 245 and this is like 10% above the maximum.

Assuming there was no error in the readings, how is this high voltage reflecting my bills,
if I use mainly electric devices:

AC
Boiler
washing machine
old fridge
electric stove
2 desktop PCs
energy saving light bulbs

Is any of this devices in danger ? For one year ago I had to replace all (normal old) light bulbs with energy saving light bulbs ... cose they burned on every 2-3 week.
Also there are constant problem with the Air Conditioning on extreme weather.


texts: Is it possible to overcome a transistor's current limit by running it at lower voltage?

texts:
Let's say I have a transistor which is rated for maximum 800mA current at 50V. Is it possible to have it running at 1000mA & 5V for example?

Edit : please provide me some details in your answer by using the BC337 as sample. Here is its datasheet https://www.onsemi.com/pub/Collateral/BC337-D.PDF


texts: Not sure to as why my simulation values are different to my calculated values for voltage across certain nodes

texts:
For the following circuit i am trying to find the voltages at the top nodes of R2 and C2. The problem im having is that when i model it in ltspice, i dont get the voltages i have calculated. I get 0.54V for VR2 and 0.23V for VC2. The ltspice simulation gets ~600mV and ~300mV. Now the strange thing is that when i ignore the 50kohm input resistance, i get these values. Therefore i was wondering if it was possible that for this lm386 amp the input resistance was forgotten? However the strange thing is that when the cutoff frequencies are checked they get the values they should be when the 50k ohm resistance is included.  (When voltages are referred to they are in amplitude)

Being the values for the answer in this
question:How to find the equivalent resistances for each filter so that the cutoff frequencies can be found?

Then when i try adding the 50k Ohm resistor just to check i get closer to the output voltage (VIN) i calculated but however the cutoff freq for the lowpass filter is 90k  hence i believe the input reistance is actually included in the amp.

Thus my main problem is 1. To check if the way i have calculated these output voltages with actual values are correct and if not please show me what have i done wrong and 2. What could lead to such a difference (especially when the frequency cutoffs are correct when 50k ohm resistance is included but for when 50k ohm resistance is not included for the voltages it is closer to the ltspice simulation?

UPDATE:
Is the input resistance (R_LM) in parallel with C3 or in series with C3?


texts: I need a switch that not only detects open/close, but also sends a pulse to wake up an ESP8266 whenever the (debounced) state changes

texts:
My application is that I'm trying to create a very small, "button battery" powered device to sense the opening and closing of a switch and send state changes via WiFi to another device on the network.  I will be using an ESP8266 (ESP-03) which has a reset (RST) pin and a deep sleep mode.

To my understanding, the deep sleep mode can be initiated by software.  Then the RST pin on the ESP needs to be brought low for at least 100us (but preferably less than 0.1 sec) to wake it up.  At that time it can check one of the GPIO inputs to see if the switch is open (high) or closed (low) and then put it back to sleep until the next open/close event.

To clarify by example, one application would be to send a notification each time a box is opened or closed, which needs to include the current status. For instance, it sits closed on a shelf. When someone opens it the ESP wakes up, sends an "is open" signal, and then goes back to sleep. When the box is closed it wakes up again, sends an "is closed" signal and goes back to sleep. The box may be open or closed for a long time, so we only want the reset pulse signal sent when the state changes.

I've seen some other articles that talk about similar situations but there don't appear to be any "this worked" comments or the cases are slightly different.  The monostable flip flop looks promising (http://www.bowdenshobbycircuits.info/page9.htm), but am I understanding it correctly?  Also, will it drain the battery?

I'm trying to keep this device as small and energy efficient as possible.


texts: Large bulk capacitance after LDO for linear power supply

texts:
I understand that modern L's need output capacitors with very low ESR and ESL for stability (or data sheet recommended values.) Is there any issue with putting a large amount (>=10000 uF) of bulk electrolytic capacitance in addition to the usual tantalum/ceramic capacitors post-LDO (about 10 LDOs in parallel?)
This would be to feed the output of a 250W 10A linear power supply, with potentials for large amounts of load transients.  My thought is that putting more bulk capacitance after would undoubtably smooth the response and ensure stability during heavy peak loads. Low-frequency DC noise is going to ruin the entire supply so I need absolute low-frequency voltage stability <100 kHz.


texts: I have a broken plastic part, disabling the button for the light switch on my cooker hood. Now I can fix it, but I've unhooked both the light switch and the hood switch, and I can't find how to connect it again. Forgot to take pictures unfortunately... I've found this circuit online, can anyone help me out how to connect it? Brown thing is the light switch. Can provide better pictures if necessary. Thanks a million in advance!


texts: How to add a MCU signal to turn off this push button mosfet-based latching circuit?

texts:
I’m using this circuit to turn on and off an Attiny85 and a led driver with the push of a micro switch.

My circuit is powered by 7.4V battery.
In the “load” part of the circuit there’s a voltage regulator to 5V and then the Attiny.
And also a led driver that get’s powered directly from the 7.4V, without going through the voltage regulator.
It works pretty well, but I’d like to be able to, when the batt is at a low state, to use an output pin of the attiny to turn off the whole circuit.
I already have a voltage divider circuit and code to check the batt levels, but I don’t know how to interface an output of the Attiny with this circuit.
What should I change in this circuit (if possible) to be able to, besides using the micro switch to turn on and off, also to be able to turn off it entirely by a signal from the Attiny?
Thanks!


texts:
LM1117-ADJ in question;

Is the output voltage 1.4V? Have I calculated correctly?

121/1000 + 1 = 1.12

1.12 * 1.25 = 1.4


texts: What replaces SD card in industrial applications

texts:
I am using a SOM (something with Zynq 7000) that boots from an SD. While SD provides a lot of storage, i can't use it in industrial applications in a long term- it is not rated for temperature range and can come out because vibrations.
What storage could be used? I want comparable volume (0.5GB at least, the more the better) and preferably something not involving consumer grade connectos.


texts: What exactly gets "worn out" and damaged by heat?

texts:
It's quite common knowledge that heat is bad for electronics. That constantly high temperature decreases the expected lifetime of computer parts even if they are not overheating per se.

If, for example, there's dust insulating a component in a PC, "cutting it off" from the usual airflow. What is it that experiences higher "wear" on higher temperatures? I've seen liquid capacitors mentioned as parts failing faster the higher their operating temperture is, because of pressure building and resulting leaking. Is that correct? But surely, there are many things else? Could you name some?


texts: I have a question regarding \$C_1\$ capacitor - do we really need it in this circuit if we know, that the input signal will have no offset (i.e. \$\overline{V_{IN}}=0V\$)?


texts:
I came across these capacitors in a kit and was wondering what type they are so I can buy more for use in button debouncing circuits. Unless I'm reading them wrong, they are 220 nF and 100 nF respectively.
Thanks,
Travis


texts: Connecting two electret microphones to computer to record stereo sound

texts:
I have two electret microphones. I would like to connect them to my computer to record stereo sound. I've checked a couple videos on YouTube and people there show they connect them "directly": signal from the first mic to the right channel and from the second mic to the left channel. Two "-" wires from two microphones are connected to the ground. Something like this:

simulate this circuit – Schematic created using CircuitLab

But also I've checked Wiki and in the scheme provided there is shown that electret microphone should be connected to some voltage source.

So, now I am a bit confused. I am not sure whether I need voltage source or not. If connection without voltage source is possible what pros and  cons does it have?

So the main question is in the title: How to properly connect two electret microphones to computer to be able to record stereo sound?

UPD: Microphone datasheet


texts:
I am trying to calculate the minimum insulation resistance of two parts (a capacitor and box) that are approximately 0.38mm apart or 0.00038m.

I've tried looking at resistivity of air which some people are giving as 1.3 × 10^16 per meter.

Would the equation 1.3x10^16 x 0.00038 = insulation resistance be accurate?

I am guessing no as I imagine the voltage applied and cross sectional area would also have an impact. I need the insulation resistance to be at least 50MOhms @ 50VDC.

Could you please advise.

Thank you in advance.


texts: getting started with NXP microcontrollers - Programmers/IDEs/Compilers/Eval Boards

texts:
I asked this question ago. (Don't need to read it to answer this one)

out growing 8-bit AVRs, not sure where to move on to

I really liked the answers about the NXP line of microcontrollers. I'm about to invest in some hardware to get started playing with them, and I wanted to run it by this forum to make sure that I'm not paying too much or buying the wrong part.

I'm not interested in the mbed chip. I prefer to have the option to build something from scratch using the full line of micro-controllers. That means I have to buy a programmer.

I'm interested in the ULINK2 from Keil. It is 411 CND on digikey.ca.
http://www.keil.com/ulink2/

It integrates with the Keil Development environment. If it turns out I can't or don't want to use the Keil IDE can I use the ULINK2 with FOSS on Linux? What about on windows without Keil? If I decide now that I don't want to go with Keil, is it worth getting another generic JTAG programmer?

Ultimately the goal is to be able to compile and program

LPC2921/2923/2925  (ARM9)  (this is the least important category for me)
All LPC21/22/23  (ARM7)
All Cortex M0 and M3

I wasn't able to find any instructions on setting up a toolchain and flash/debugger program for NXP microcontrollers, and that is the only reason I'm talking about Keil related products. I would rather just use GCC and some other uploader. I'm used to avrdude for AVRs.

What kind of setup do you guys use for ARM or NXP uCs? What JTAG programmers do you recommend? Any other FOSS toolchain instructions or other software I should know about?


texts:
I'm working on a project that uses 1700VDC provided from a 220V:1200V isolated toroidal transformer, bridge rectifier and filter cap. I have no experience with high voltages, so I'd like to ask you some questions regarding safety. So far, I will:

Use insulating gloves Class 1 + leather protector glove.
Use Emergency button.
Use warning lights
De-energize circuit before taking measurements.

My questions:

Since the transformer is isolated, I don't need to use insulating boots right? Should I be concerned with capacitive coupling that is mentioned here?
Should I ground/earth any part of my circuit? How about the equipment frame metal parts?
Should I use RCD or circuit breaker only?
Am I missing something?


texts: How do i decide the value of \$R\$,\$L\$ and \$K\$ in the bandgap when i want a specific \$V_{ref}\$

texts:
The bandgap schematic is as below,i read books about it,and find that books only teach us how to decide the value of \$R\$,\$L\$,and \$K\$,but doesn't teach us that if we want specific value of \$V_{ref}\$,how do we decide the value of \$R\$,\$L\$ and \$K\$.

So i want ask if i want a \$V_{ref}\$ for 1.98v,how do i decide the value of R,L and K,
according to the formula

\$V_{ref}\$=\$V_{D3}\$+\$L\times n\times lnK\times V_T\$,it seems that we can derived them from this formula ,but the \$V_{D3}\$ has a relation with L and R,so i don't know how to decide the value of  \$R\$,\$L\$ and \$K\$ from this formula


texts: STM32F105 stop executing after 16 seconds

texts:
I'm facing an issue with an STM32F105 microcontroller which with a simple code executing in a while loop it stops after 16 second
here is code which I don't think there is a problem with the code since it runs fine on STM32F103
while (1)
  {
      uint8_t frame[8] = {'H','E','L','L','O','W','O','R'};
      CAN1_TX(0x110110,8,frame);
      HAL_GPIO_TogglePin(GPIOA, GPIO_PIN_1);
      HAL_Delay(500);
      CAN1_TX(0x110110,8,frame);
      HAL_GPIO_TogglePin(GPIOA, GPIO_PIN_2);
      HAL_Delay(500);
  }

void CAN1_TX(uint32_t id,uint32_t dlc,uint8_t frame[8]){
    char msg[50];
    CAN_TxHeaderTypeDef TxHeader;
    uint32_t TxMailbox;
    TxHeader.DLC = dlc;
    TxHeader.ExtId = id;
    TxHeader.IDE = CAN_ID_EXT;
    TxHeader.RTR = CAN_RTR_DATA;
    if(HAL_CAN_AddTxMessage(&hcan1, &TxHeader, frame,&TxMailbox) != HAL_OK){
        Error_Handler();
    }

    while(HAL_CAN_IsTxMessagePending(&hcan1, TxMailbox));
}

The two leds blinks for 16 seconds and then they stop.
When I changed the delay to 500 it blinks now for 8 seconds only.
The problem is from the CAN_TX functions the problem only happens when CAN1_TX or CAN2_TX added
Debugging didn't help after that 8 seconds the debugger don't show any problem or where it is hanging
EDITED**
Now after more digging.I changed the CAN mode to LOOPBACK and the problem disapeared it seems that the problem only happens on normal mode but why ?  when I switch back to normal mode the problem came back
please note that the CAN_TX does not work now while it was sending frames yesterday
here is the clock config in case it has anything to do with this issue


texts: 555 timer as a voltage controlled oscillator, duty cycle query

texts:
I`m trying to create a square wave generator using a 555 timer but i noticed that due to the pulse width modulation as i vary the control voltage, the duty cycle changes so i was wondering if there is a way to ensure the duty cycle stays to 50% regardeless of the control voltage input.
If anyone could point me to the right website or book that would be great.

this is the basic circuit im using:

source : http://www.learningaboutelectronics.com/Articles/Voltage-controlled-oscillator-VCO-circuit-with-a-555-timer.php


texts: Understanding flyback diodes in an H-Bridge

texts:
I am able to understand the use of flyback diodes when a basic low side unidirectional motor switching is done with an N channel MOSFET for example. I also understand the working of H-Bridge configuration. However, I could not understand how those diodes are acting as flyback diodes in this configuration and also why we don't need them while using MOSFETs but do need while using a darlington pair for example.

Here, it is obvious that for Q1 & Q4 are ON(closed) situation, the current will flow in this path:

+12V - Q1 - M - Q4 - GND

And then, when we open(OFF) Q1 & Q4, the path for current flow has been corrupted. However, there is still magnetic energy stored in the inductor of the motor, but, I don't understand with which path it will be discharging and how this will protect the transistors.

Thanks in advance.


texts: Automatic transfer switch VS Using a Reversing Contactor with Circuit Protection

texts:
We have a an industrial control system that utilizes a 480VAC 3 phase 10 Amp service.  For redundancy reasons, we wanted to add an automatic transfer switch to the system to switch between two redundant power sources (each are 480VAC 3 phase).  Automatic Transfer Switches (ATS) are expensive and usually pretty large.  We would like to use the following scenario instead of the ATS:

Use a reversing mechanically/electrically interlocked contactor to switch between the two power sources.
Use two voltage sensing/monitoring relays (3 phase) to sense if the phases and power is good on either power source.  If the primary power source fails, the voltage sensing relay would detect this and energize the coil on the contactor to switch to the redundant power source.
Add circuit protection (most likely breakers) before and after the reversing contactor.

We do this type of setup on a 208VAC single phase system and it works great.  Here is a diagram of that setup:

Other concerns I have is arcflash requirements, phase sync issues, and if UL would be ok with it.

The 480VAC in our system supplies power to a VFD and a 480VAC to 120VAC transfomer.  These would be the piece directly affected from switching from one power source to the other.

Any insights would be greatly appreciated.


texts: Can you help identify the controller of smps

texts:
Found on smps it is probebly the controller - but couldnt find it on google
Looks like it is writen 9202 834p4


texts:
I want to sense brightness via an OSRAM SFH3310 phototransistor by using an ADC (Vref 3.3V - teensy 3.1).

I understand that I need a voltage divider to get a good ADC reading. In the past I simply connected a potentiometer and tried out which resistance value maxed out the ADC value. The best value I figured was 120k.

simulate this circuit – Schematic created using CircuitLab

I would love to understand the datasheet more precisely, to have a more engineered approach :-)

From this diagram, I would derrive, that at 3.3V at 20lux (almost dark), I would have a current flow of around 5uA. According to Ohms law, this would mean a resistance is R=3.3V/0,000005A= 660kOhm? In brightness I read 70uA, R=3.3/0,000070A=4.7kOhm. Do I use these values for R1 in the voltage divider.

I'm not sure if I got the right thinking here.

Thanks a lot for your help.


texts: Altium Designer multi sheet design quad op amp

texts:
I have to design an multi channel sampling device: there is an input stage with some filters, then digitization of them and some supplementary circuit.

To create a filter, I want to use quad op amp, but one channel needs only 1 from the package. And I want to represent my design on subsheets, each sheet contains only 1 channel.

Can anybody help me how can I instruct Altium Designer to recognize that op amps in every four sheet belongs to the same package?


texts: Extra Shottky Flyback Diodes on FET-based BLDC Motor Driver?

texts:
TL;DR: I have a FET-based BLDC motor driver design, and I need to decide whether to add discrete Shottky diodes in parallel with each FET for reliable and long-lived operation in an automotive-like application. Yes? No? What do I need to consider?

Longer version:

I'm going through the details of a 3-phase BLDC (brushless DC) motor driver, and I'm debating whether to include discrete flyback diodes. The circuit looks like this one:

A few other parameters:

It's a 48V, 40A continuous (60A intermittent) driver.
Reliability and toughness are a factor. This will see service as a traction motor driver in an automotive-like environment, for a small vehicle.
The system will see operation in all 4 quadrants.

Since the FETs already have body diodes, there are technically flyback diodes in place already, which means that even if the active components fail, there will still be a path for currents to flow. The question is whether these are enough to handle all of the scenarios that come up during normal (read: abusive) operation in the field.

I've considered adding a discrete Shottky diode in parallel with the FET body diode. In principle, since it has a lower forward voltage curve as well as a faster response time, any flyback currents should shunt through the Shottky instead of the FETs. If the current ever comes along, this is a good thing. But the question is, will there ever be a scenario where the body diodes aren't big enough to handle the heat?

Does anyone have any experience as to whether adding discrete Shottkys in a FET-based motor driver bridge provides any benefit? If so, what do they protect against?


texts: Verilog odd behavior with multiple edge detect

texts:
So I'm a newbie to Verilog.  I decided to purchase a nice board (a Terasic DE0-CV) and teach myself some Verilog.  And I'm seeing some strange behavior that I can't explain.
I lifted some code out of an example that drives the 7-seg LEDs.  And I have them tied to a register.  Whatever the register holds, the LEDs display.
reg [23:0]  mSEG7_DIG;
SEG7_LUT_6          u0  (   .oSEG0(HEX0),
                            .oSEG1(HEX1),
                            .oSEG2(HEX2),
                            .oSEG3(HEX3),
                            .oSEG4(HEX4),
                            .oSEG5(HEX5),
                            .iDIG(mSEG7_DIG) );

I made a simple counter to drive the register, like this:
always @(negedge KEY[3]) begin
    mSEG7_DIG <= mSEG7_DIG + 1;
end

And that works just fine.  Click Key[3] on the board, the counter counts up from zero with each key click.  Works like a charm.  Sees the edge, increments the register, displays on the LEDs.  So next, I wanted to make a way to clear the register to start back from zero.  This is the idea I was thinking of.
always @(negedge KEY[3]) begin
    mSEG7_DIG <= mSEG7_DIG + 1;
end

always @(negedge KEY[2]) begin
    mSEG7_DIG <= 0;
end

This turns out to not be legal, since I have two always blocks trying to drive the same register.  But you get where I'm going with this.
So I figure "Ok, I'll make them into one always block, then check the switch levels to see what we're trying to do, increment or clear."
So I did this to start.
always @(negedge KEY[3], negedge KEY[2]) begin
    mSEG7_DIG <= mSEG7_DIG + 1;
end

For whatever reason when I do this, the counter counts so fast you can't see it.  I've tested it for hardware problems by doing this:
always @(negedge KEY[2]) begin
     mSEG7_DIG <= mSEG7_DIG + 1;
end

And that works fine too.
So what am I missing?  Why does having two edge dependent signals in my always block's dependency list make it seem to be always true?
Edit:  The hint from IanJ - "the synthesis tool doesn't want to make something sensitive to two different edges", and being able to see what synthesis is doing with my code in RTL viewer - this allowed me to solve the problem.
The problem - imagine a CLK line going into a D type flip flop.  And you want two signals to control it.  But I didn't specify HOW.  The synthesis tool would have to be a mind reader to understand my intention.  You have to explicitly say how you're triggering.  This solves the problem.  Full points to IanJ for the tip - that led to this solution.
wire change;

assign change = ~KEY[2] | ~KEY[3];

always @(posedge change) begin
    if(~KEY[2]) begin
        mSEG7_DIG <= mSEG7_DIG + 1;
    end
    else begin
        mSEG7_DIG <= 0;
    end
end


texts: Detecting capacitive touch in low power applications

texts:
Using some kind of ARM, the application has a very low profile of about 30-50uA .
I would like to detect capacitive touch. If I do this with code, I will have to wake and sample, and thats expensive for a coin cell.

Is there a clever way to create some hardware with MOSFet that will create an interrupt to the ARM so the touch will not be in code ?

Yes we can close some mosfet with some gate configuration , but then how would you do double tap and all other things that can be done only by code sampling ?


texts: H-bridge: Augmenting output from an existing IC

texts:
I've got a bunch of these integrated H-bridge & driver IC's in my stock and wish to use them in an upcoming design:

http://www.toshiba.com/taec/components2/Datasheet_Sync/201006/DST_TB6593FNG-TDE_EN_27195.pdf

However, these IC's can only drive 3.2A.  I would like to augment the current handling capability of these existing IC's to be able to drive about 6A through a solenoid.   I do not want to buy new stock of beefier H-bridge/driver IC's, if possible.

The solenoid itself has parameters of R=2ohms, L=1mH

I simulated a proof-of-concept, barebones circuit to augment drive capability consisting of two push-pull pairs that are driven by the H-bridge outputs, and those BJT's then drive the bulk of current through the solenoid.  The H-bridge itself is generic; I simply put it together in LTSpice with some high Ron MOSFETs to simulate the current limitation of the IC, for which a macro model does not exist.   Results are illustrated below:

Questions about this approach:

(1)  Is this a safe way to augment the capability of this IC, or other similar IC's?
(2)  What can I add to augmented circuit above to simulate more accurate real-world behavior?
(3)  Is this approach ever used in industry?  Or is there a better method?
(4)  Are there any pitfalls or "gotchas" with the augmented circuit above?


texts: SIM800: AT-command to get connected sender ids

texts:
I want to roughly estimate where my Arduino currently is. For this, I want to fetch the identification numbers of the stations it is currently connected to, so I can put them into an API which then gives me an estimation based on the phone masts. Sadly I haven't found anything regarding that topic in the datasheet.
 Do you know how I can ask for that info? Furthermore I'm currently looking for some database with all the mast coordinates, if you have any recommendations I would be very thankful for your advice.


texts: Serial to USB adaptors - types and problems

texts:
I have an electronic device (commercially available, which someone else made), which essentially consists of a series of photoelectric cells, going through a black box of electronics, and through to a serial port plug.

In our old computer system, this connected to the serial port, and software onboard would detect when each photoelectric cell was activated.

Now our computers don't have serial ports, so we got a serial to USB adaptor to connect the device to the PC. However, with this setup the software fails to detect the activation of the photoelectric cells.

My question is: Are there any major caveats with using serial to USB adaptors? How do they work? Can they fail to provide correct conversion? Are all different types the same?


texts: Is there an industry standard definition for "load"?

texts:
I come across load meaning either power or energy from time to time in the context of residential loads or load forecasting. As such I was wondering if there is a convention as to whether "load" more often refers to power (kW) or energy (kWh)?

I've recently adopted the language of "demand" for power and "consumption" for energy, as I think they offer a little bit more clarity.


texts:
I am planning to do a near space balloon project with my son. I want to do something special. I don't want to just send up a camera I want to broadcast live video and other metrics.

I have a strong coding background and Arduino background.

What I want to know is

If I can transmit live video feed (maybe 1 - 2 fps) over UHF?
If I cant use UHF what is the proper transmitter for this?
If I can use UHF is there a easy to use Arduino module?

I am estimating the range need at anywhere from 100k - 120kft so 19 - 22 miles give or take.


texts: STM32 interrupts and C++ don't go well together

texts:
I set up TIM3 to fire an interrupt in my project and it just wouldn't work. I tried everything I could and still couldn't find whats the problem. Then I created a clean project and copy/pasted only the code that sets up TIM3 and interrupts and it magically worked.
I literally wasted half a day trying to find what causes the problem and it turns out... interrupts don't like C++.

I wrote my code in C++ because I needed classes in my project so naturally I renamed all my prject .c files to .cpp and also compile with the --cpp directive. Everything worked fine, no problems so far until I decided to use interrupts. So I renamed everything to .c and everything worked, renamed everything back to cpp and it stopped working.

I use Keil uVision5 and my projects are generated with STM32CubeMX (only RCC config).

Anyone had this happen to them? Any workarounds?


texts: What are the appropriate pulse width and PRF for a pulsed Doppler sensor

texts:
I have a raw k-band transceiver, radar-based 24 GHz, motion detector, IPM-165.

and here is the datasheet:
https://www.innosent.de/fileadmin/media/dokumente/DATASHEETS_2016/Datenblatt_IPM-165_V8.5.pdf

I want to design an amplifier with a 50 kHz bandwidth. I want also to run the device in a pulse mode to save power. Probably 20% of duty cycle is fine to save fifth of the consumption.

I have two parameters which I should design.

1) the pulse width.
2) the pulse repetition frequency (PRF).

and I know the sampling frequency should be 2*50 kHz at minimum according to Shanon.

So what are the calculations of these two parameters in order to sample & reconstruct a signal of 50 kHz at maximum?


texts:
I'm experiencing a strange failure of electronics after potting which I'm hoping to get some more insight and explanation to. The device is a custom, rugged USB drive in an Aluminium/Titanium body (see www.viud.net for pictures and more details). I'm potting the USB board (a variety of off-the-shelf boards) in Aremco 526N epoxy and curing in the oven. The USB drives are verified to work fine before potting but after potting I'm getting a high failure rate (17% Aluminum body, 78% Titanium body).

Possible explanations for the failures I've considered are:

Heat - Since I'm curing the devices in the oven I thought that maybe they were getting too hot. The first batch was cured at 90C for 2 hours but after testing I found the oven does get considerably hotter than that. The next batch I did at 55F for 4 hours and confirmed that nothing gets hotter than 80C but the failure rate didn't change.
Epoxy - The Aremco 526N is not technically advertised as a "potting" epoxy although its electrical properties are better or similar to other potting epoxies I've used with no issues.
USB Drive - The failures occurred with 4 different USB boards so it is unlikely related to that.

None of these possibilities explain why the Titanium models have a much higher failure rate than the Aluminium. If it was heat related I would expect the Aluminium models to have a higher failure rate anyways (thermal conductivity of the Al is x36 greater than the Ti).

The only possible cause of the failure I have left is related to internal pressure of the epoxy while it is curing in the oven. The epoxy is essentially sealed completely into the body with only a very small escape through/around the USB connector. Since the epoxy around that area likely sets first the rest of the epoxy in the body is likely under some pressure due to thermal expansion. This also explains why the Titanium models fail more than the Aluminium: the Al conducts the heat faster through the body which means the epoxy sets more evenly reducing the internal pressure.

Unfortunately, I have no way of verifying this theory as to open the drives I have to destroy the USB. I also cannot believe there is enough internal pressure from the epoxy to actually damage the circuit board. I can try curing the epoxy at only room temperature but it then takes weeks to set and the epoxy is not as strong.

Any ideas, theories or comments on my issue are more than welcome.


texts: Need to move a 12v DC, 1.5 ohm resistance circuit (power window motor) into another vehicle with a .8 ohm motor

texts:
In the past, when I have tried to cut down the voltage from a variable solar panel into a DC motor with a 10 watt resistor, the resistor always got too hot.
This case is a somewhat different; a solid 12v DC source and a computer that is apparently looking for 1.5 ohms and all it sees is 0.8 ohms from the new power window motor.
This question arises from a restomod project where I am moving most of the electronics, engine, wiring harness, interior, dash, etc. from a 2014 Camaro into a 1970 Malibu.
How would you fool the computer and still allow the motor to function?

Somehow I missed the below response, mea culpa.
It's the body control module (BCM) in a newer Camaro.

Here's a pic of the semantics in the service manual...


texts: Am I having a power supply issue with my LED lights strips in series, or have I done somethine else wrong?

texts: I bought two LED light strips and connected them together end-to-end using a solderless snap connect. The strips are each 5 meters long, "LEDMO SMD 2835 White Non-waterproof LED Light Strip - DC12V 600LEDs 16.4 Ft 6000K 15Lm/LED High CRI80". Then at one end I connected a remote control reciever "LE® Mini Remote Controller for Single Color LED Strip Lights, RF Dimmer for 12 V DC LED Light Strips, 12A". To that I then connected a power supply adapter that is "12V, 5A Max, 60 Watt Max". It works great for a couple of weeks and then the lights just get dim. It is like they are stuck at half power. I replaced the power supply once and they were bright again for a week or two and then they get dim again. I wonder if I am burning out the power supply because I have something configured wrong?


texts: Was curious if you anyone had information as to why 5GHz wifi is more susceptible to walls and floors in buildings (as compared to 2.4Ghz) but the opposite seems to be true for VHF vs UHF. We tend to use VHF radios outdoors and UHF radios more indoors.  Seems like 5GHz is to UHF (both higher freq) as 2.4GHz is to VHF (both lower freq); and yet seems like the penetrative properties are opposite.


texts: How to calculate pi-type impedance matching circuit?

texts:
The value provided in the first schematic L=2.7nH, C15=2.0pF, C14=2.7pF, how they will get these values. If I want to design an impedance matching circuit for the same (30+j10) ohm, what process I will follow? it's Related to ESP32 antenna.
Sorry for incomplete information.
I want, how to design PI- type impedance matching circuits.

operating frequency: 2.4 GHz
input impedance: (35+j10) ohm
output impedance: 50 ohm


texts: FPGA or Microcontroller for Production Design?

texts:
I have a very simple LED driver circuit connected to a 7 segment display and a couple of buttons. I want to move this design to production, on a scale of +1k units.

I have implemented the design on an FPGA partly because it seemed simpler to hook everything together and because the development board I have already has buttons + a 7 seg display. I'm also under the impression that the synthesized design is more easily "transferred" to a PCB. However, I can't figure out a clear answer.

The design is simple enough that I could make it for an MCU pretty easily. AFAIK, with an MCU, you get all your components and the MCU and solder them onto a PCB (for a prototype), and once the design is final, you could get this PCB assembled by other companies. I don't know what the process would be for the FPGA implementation. so I was wondering what advantages/disadvantages there are with going with an MCU or an FPGA based design?

EDIT: I'm trying to figure out the workflow. I'm using Xilinx ISE and I have synthesized vhdl. How do I convert that to a schematic I could get printed? And does this direction offer any advantage to using an MCU based design


texts:
I've asked a similar question a few months ago, but I have a few more questions.

Background: I plan to chain multiple LED strips to one another (by soldering) to make one, long LED strip that will be hung up along the outline of my room.  I do not currently know whether four LED strips will be enough to surround the entire room, but I purchased five just in case.

LED Strip

Power Supply - Not the exact item, but an identical one rated for 12 V and 25 A.

As you can see, the LED strip is rated at 12 V DC, and consumes 48 W per strip.

I had the opportunity to measure the current drawn from one strip at 12 V, and it reached almost 1 A.

Question: If I were to chain four or five of these strips together, would they be able to handle the amount of current drawn at 12 V?  If not, would connecting wires to ground at each chain prevent too much current being drawn?

Note: I plan to supply each side of the long chain (four or five strips) with 12 V and not just one end.

Thank you!


texts: Working of a current mirror as an active load

texts:
Ordinary resistor as load in a transistor amplifier has a certain short coming…we cant have voltage and current gain simultaneously …..

In this circuit a current mirror is actings as an active load in place of RL …I wonder how this current mirror able to give voltage as well as current gain at same time??


texts: AD725: is it dot crawl - and what to do about it?

texts:
Device's datasheet says

  One well known distortion of composite video images is called dot crawl. It shows up as a moving dot pattern at the interface between two areas of different color. It is caused by the inability of the monitor circuitry to adequately separate the luminance and chrominance signals.

Here's animated GIF I made out of 20 frames of video (original video):

Look at the Ok text in the middle: the dots crawl inside O letter out of its white image two pixels off, and there's clearly one or even two blue pixels in between from both sides.

If I tune frequency of the carrier, the dots stop moving, but they keep hanging in their odd locations.

The effect is seen on all the pixels of the image, the O is the best it is seen with. Image feels like being floated on the wavering water, or another analogy: like you have a fire in front of the image and hot air makes it waving when you look at it.

How can TV I use (40-inch Samsung LCD) have such far away crawling, and what could be the cause?

Is it more problem of encoder, or decoder in the "too clever" TV?

I have used reference circuit for the chip, removed all options like switching standard - having it NTSC with YTRAP set up with 68 uH inductor and 28 pF capacitor. When I had additional diode, cap and resistor tied to standard selection pin I had even worse picture; now I am trying to see if I can have more or less acceptable pic with all the possible fat cut.

Update 1: I disconnected YTRAP circuit from pin 12 completely, and crawling did not change. But I would say overall image quality improved! Now characters on the screen are extremely sharp. If not crawling I would be exceptionally happy.

Update 2: I reconnected RCA connector to the luma wire in hope having precise and beautiful grayscale picture, but got the following instead for white chars on black background:

Do I miss something, and pure luma signal from the S-video set of wires gets into chroma band? Interesting that white chars on blue background are displayed excellently (in grayscale), but when black chars on gray background screen flickers heavily at the top 1/3 of the screen.

Update 3: Took the scope to see what is going on.

Below is luma output

And below is chroma output

And blow is composite output:

I think FSC (279 ns) is hugely affecting both signals.

But I suspect it could be normal as datasheet is having the following pic, showing the same noise on the composite output.


texts: Optocouplers for purposes other than galvanic isolation?

texts:
In the diagram below there are two modules, A and B, which are separated by a physical distance of about 15m. Module A has a 12V DC power input. Module A powers module B (they share a common ground).

There are also a number of signals that are passed between the modules. For each signal there is an optocoupler at both the transmitting and receiving end. One such signal is illustrated below.

I would like to know what the purpose of this optocoupler is? Personally I have only used optocouplers for cases requiring galvanic isolation. This is clearly not the case here, since both modules share a common ground. Any ideas on why the designer might have included these optocouplers?

The only thing I can think of is for level-shifting and noise-rejection. But this could more simply be achieved with ordinary transistors and a passive filter. Do optocouplers offer any advantages here?

simulate this circuit – Schematic created using CircuitLab


texts:
what are the main used ways of how to handle deep sleep of some microcontroller (atmega or a cortex m0/m0+) with waking up periodically?
Right now, I'm building a Sigfox GPS tracker that should send GPS position every ~10 minutes and this interval should be configurable.
I solved this problem in previous projects either by using external RTC IC (temperature compensated for great precision) or counting of 8sec intervals (let's see https://github.com/rocketscream/Low-Power). What are the other ways and their advantages?
My plan is to either stick to the Arduino ecosystem or switch to the STM32 world (maybe with a bit of help of mbed platform).
I really appreciate all your feedback.


texts:
I've got some issues making a SIM800L module to power up correctly through a mosfet.

Parts:

2x LifePO4 batteries in serie (6.4V 1800mAh)
1x LM2596 DC Converter (Converts to 5V and able to peak at 3A)
1x SIM800L (Might has peaks of 2A)
1x IRF540N Mosfet (N-channel enhancement)

The project is powered from DC\DC converter (Converts to 5V from batteries) and SIM800L directly without the mosfet. The SIM800L will power up nicely and connects itself to the network with communication as expected.

But when I am adding the mosfet (which I wanna use to completely turn off the SIM800L) it stops working accordingly. I get power issues. Quick blinking of the LED and never connecting to the network.

I expect that the SIM800 is not drawing enough current to startup the way it is supposed to be. But according to the datasheet of the IRF540N it should be able to draw 10A at 5V. So I am a little bit puzzled why it is not working.

I added a cap. (10uF, Vcc to GND) right next to the SIM800L but that didn't make any difference.

Am I using the wrong mosfet for this kind of setup, or do I miss some theoretical knowledge and parts that inhibit this setup from working? Is the given continuous drain current not as straight away as I think it is?

Datasheet mosfet: https://www.infineon.com/dgdl/irf540n.pdf?fileId=5546d462533600a4015355e396cb199f


texts: I have a light that needs to be powered by battery.  It is a 12V light that draws 4.5 A of current.  If I purchase a SLA battery that is 12V rated 5.0 Ah would that battery be sufficient?  I am confused on the whole Amp/hours rating.  Is a 5.0 Ah battery able to deliver 4.5 A of current?  And for how long?  Will be using deep cycles probably lighting the light for 10 seconds at a time.  Any help appreciated.


texts: Can I connect the LoRa Module pin to SMA Antenna with wire?

texts: I have RFM95W LoRa Module and an antenna with an SMA connector (you can see in the image below). The module does not have an SMA connector. There are just pins. Can I connect the SMA connector with some wire soldering to the LoRa module? Will this make any communication problem?


texts: Suitable connector/wire for 3A output from PSU

texts:
I've searched through the questions that have been asked but none have dealt with this particular problem:

I'm designing a PSU board that will have, among other things, a 12V/3A regulator. I want to transfer this 12V/3A regulator output to a separate motor driver board over a wire/connector.

Can anyone tell me what type of connector/wire I would need to transfer this 12V/3A? I've used an online wire gauge calculator which says that I need a 14 AWG wire for 12V/3A over a length of 0.1 feet, but the wholesaler websites that I've looked at do not specify the current rating/ampacity of the wire.

Cheers,
Tony


texts: Inverter Mosfet Driving with Isolated Totempole Supply

texts:
simulate this circuit – Schematic created using CircuitLab

I'm trying to make an inverter and I'm driving my mosfets with totempole configuration, the thing that confuses my mind is:

Totempole supply voltage is isolated from inverter's input DC, I mean the totempole gnd and inverter's supply gnd is not common due to a isolated power supply that I'm using for converting inverter's 350V input to 12V for gate driving.

I'm not sure it's going to work or not.

Thank you.


texts: Debugging a PIC16F84A interface with a 4N25 optocoupler

texts:
I have a PCB board that I'm trying to repair, the principle of this circuit board is to switch an oven relays one at a time only with a constant rest time, and the switching time is predefined by the oven user.

The PCB is constituted of a PIC16F84A interfaced with 2 multiplexed 7-segment displays, and with two relays, there is also the pin RA4 connected to the collector of the optocoupler 4N25. I bought a new PIC16F84A and burned on it my self made program, and i simulated first the whole PCB circuit on Proteus, in simulation everything is working fine as expected except the optocoupler part which i found weird.

To be clear, i attached a screen-shoot of the Optocooupler part with the PIC16F84A in Proteus.

The Optocoupler play the role of a door logic open/close in an oven represented as a switch in the above simulation, however, some issues have been encountered:

1/ The PIC seems to reset infinitely as you can see the MCLR of the PIC is connected directly to the collector of the PNP transistor B327 which is grounded via the Emitter of the photo-transistor via a resistance R18, is this normal? note that it is not my circuit design, i just made it in Proteus depending on the PCB on hand to test it.

2/ When i connect the MCLR to the +5V with a 10k resistor, the circuit seems to work fine, however, i don't understand the purpose of using Zener Diode on the BC327 Emitter ?

3/ At the input of the 4N25, i found a current limiting resistor equal to R17=33k, and knowing that the 4N25 has a 20% CTR we get low current at the input , and the optocoupler will never get anything at the output ! to resolve this issue, i assumed an If=20ma and changed the R17 = 200 and now the optocoupler started to output the necessary 1 logic to the PIC, i want to know please if there is any purpose to use such high R17 from the designer?


texts:
I want to pour ground under a ESP8266 12-E just for thermal reasons but I don't know if this can affect it somehow or if it's safe to do. The PCB is all under 5V, it's only 2 layers and it would have some signal traces, all on top. I have noted that with ground pour I get some more free space because I don't need GND traces (and would have several of them).

So I have three questions:

1) Does the ground pour affect ESP12-E?

2) Is it safe to have a ground pour with signal traces on it?

3) If it's safe to do 1 and 2, I should pour ground on bottom too, right?


texts:
I don't know if self-contained units like this exist, but I'd like to think they do, and I just don't know what they're called, who makes them, or where to find them.

Please bear with me, for a moment.  Imagine a lamp, a simple On/Off latching switch, and a battery connected in series.  The lamp is powered when the latching switch is in its on position.

Is there another switch-type or device that can be added to the circuit, that if pressed whilst the simple switch is on, opens/breaks the circuit until the simple switch is off. The new device is effectively a latching normally closed switch, but special because it can reset its own state to closed, if the simple switch changes position to off, and current no longer flows.

Ideally, I'd like something with these characteristics:

12V 0.5A
10-30mm diameter or width
panel mountable
LED indicator (not required, but would be nice!)
ideally looks like a latching switch but resets mechanically.

Any help appreciated.


texts: What does two input and one output buffer like gate do?

texts:
Reading through my textbook, I found the circuit of DRAM, and I can't get one part of it. It looks like that in one cell configuration as well.

My question is: what does two input and one output buffer produce? I know that buffer passes the data it got from one end and outputs to the other end without modifications. Am I correct that this is indeed a buffer and not some other gate of the circuit?

P.S. there are some other gates before the read/notwrite, but I decided to omit them, since they don't seem to be relevant.

simulate this circuit – Schematic created using CircuitLab


texts:
I want to connect 12 LEDs with 3 switches.
First switch to turn on 4 LEDs.
Second 8 LEDs.
Third switch to turn on all LEDs.
I don't know what kind of switch to use and the schematic.


texts: Why does CircuitLab have the MOSFET symbols it has?

texts:
CircuitLab has [used to have -- they have changed their symbols since this question was asked] these goofy things:

simulate this circuit – Schematic created using CircuitLab

My eyes are much more accustomed to these:

...with the simpler versions on the right used really only in the context of CMOS ICs.

I don't think I've ever seen CircuitLab's symbols used in the wild. In fact, doing a Google image search for MOSFET seems to turn up just one occurance of CircuitLab's symbols, which appears to be an adaptation of Wikipedia's image.

Am I totally off my rocker here? Are these symbols some crazy European convention I know about or did CircuitLab select them just to annoy me?

The image notes on Wikipedia suggest these symbols come from Sedra and Smith, "Microelectronic Circuits", but not having that book, I don't know what justification it gives, if any, for new symbols. Can anyone shed some light?


texts:
I have built an Amplitude Modulator using Proteus. Here is the schematic and output. The output does not seem to be correct however.

Can anyone point out what is the problem?


texts: Designing schmitt trigger having two positive thresholds

texts:
I have two supplies, V1 and V2. V1 is fix to a certain voltage. V2 is variable and I want to switch the external circuit ON when V2 < V1. For this case I have used OP-AMP as a comparator. But what I want to do next is to put two thresholds (UT and LT; Both positive).

The Output of OP-Amp should be either +Vsat OR Ground.
If I set V(-) at gnd then I can't set the lower threshold i.e. LT. How can i achieve this?

Here is the poor screenshot to give you an idea.

Edited: To correct the labels


texts: Show tracks and via's in 3D view in the latest Altium Designer 20?

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I want to view the tracks and via's in Altium Designer 20 when I am in 3D view (shift+s is not what I want since that will hide the components and only show the tracks and via's).

How can I be in 3D view, leave everything intact, and on top of that show the tracks and vias like the image shown below


texts: How do laser printers produce the positive and negative charges on the paper?

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I understand the general idea of how it works but I am a little confused on the actual details.

For instance I understand that the corona wire positively charges the entire drum and the laser then uncharges or negatively charges the parts of the drum where the text is.

My question is, how specifically does it do that? Is there something special about the composition of the corona wire or the current running through it that shoots off positive charges to the drum?

How does the laser actually discharge or apply negative charge to the drum areas?

How do the toner particles get charged?


texts: Is the current zero on an opened branch using Thevenin's theorem?

texts:
I have this circuit:

Initially it was all on blue. Then I opened the circuit in A and B (on red).
The exercise asks the value of resistor R knowing that there passes a current of 1 A, using the Thevenin's
Theorem.
My question is, when I open the circuit on A and B, I remove the resistor R to the Thevenin's equivalent circuit. So, does the current I2 becomes zero, and I becomes equal to I1 ? It would be, since I'm opening the circuit there. But when ill find Thevenin's equivalent resistor, I can't say the resistor of 2Ohm is in series with the resistor of 6Ohm, so, the node between them keeps dividing the current to terminal A. How come?

If current I2 becomes zero when I open the circuit, that node wouldnt divide current anymore, so the current that passes on the resistor of 2Ohm would be equal to the current that passes on resistor of 6Ohm, so both resistors would be in series.


texts: Pre-amplifier biased to one-half of power source

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There is a schematic of an pre-amplifier that use one-half of voltage source output biasing (T1 emitter is one-half of V1). How the resistive network was calculated to allow one-half output Q-point?

Original link: http://www.zen22142.zen.co.uk/Circuits/Audio/lvpreamp.htm


texts: RFID reader(125kHz) switching between antennas

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My arduino application wants multiple separate cards in multiple separate (nearby) locations to be readable at roughly the same time.

I am using a RDM6300 module, with a multiplexer to switch between antennas, and this is slow. (Power down, switch in an antenna, power up, wait long enough to be sure the card would answer if it was there, power down, switch in the next antenna and so on)

There's an RX pin labeled in addition to the TX pin on RDM6300 module, might it be possible to put these things into a mode where I could be queried on demand, with timing I can control?

Should I use another 125kHz RFID reader to accomplish a faster read? ID-3LA Reader seems to be a better choice. Did anyone use it in a similar case?
Can I use ID-3LA Reader without power down/up when the tags are already available in locations?