texts: How to recharge a bootstrap capacitor on an H-bridge with each transistor controlled with a pwm GPIO?

texts:
I have built an H-bridge using bootstrap. Each MOSFET is controlled by a PWM output of my µc.
Let's say my motor turns clockwise. I set H1 and L2 to a duty cycle α = 0.9, then to recharge H1's cap I would need to close L1 when H1 is off. So L1 has the duty cycle = (1-α).
I use mbed and there is no easy way to control the timers, compare registers etc. How could I set L1 to be the opposite of H1 if I'm going clockwise?
I thought of using a down-counter but it would need to be perfectly synced to the up-counter - right?
Thank you for your help
Here is my source code.
void set_force(float force){
    if(force == 0.0f) {
        L1.write(0.0f);
        H1.write(0.0f);
        L2.write(0.0f);
        H2.write(0.0f);
    } else if (force > 0) {
        L1.write(0.0f);
        H1.write(1.0f); //H1.write(force);
        L2.write(force);
        H2.write(0.0f);
    } else {
        L1.write(1.0f); //L1.write(-1.0f*force)
        H1.write(0.0f);
        L2.write(0.0f);
        H2.write(-1.0f*force);
}}


texts:
Let's consider a CMOS inverter. It is known that its propagation delay depends on supply voltage (VDD) and on output parasitic capacitance Cout (which is due both to its transistors' output intrinsic capacitances and to the input capacitances of the cells eventually connected to the output).

But does it depend also on the inverter input capacitance (that is due to its transistors' gate capacitance)?


texts: LDO with tantalums and circuit with ceramic bypass capacitors

texts:
I'm going to use MIC5205 voltage regulator.
According to the datasheet and many sites and discussions I must use tantalum capacitors for the output. This LDO is unstable with ceramic capacitors (low-ESR caps in general). So I'm pretty aware of that.
But I'm not sure if I can use ceramic capacitors for bypassing in my circuit.

This is my LDO:

This is one of ICs powered by that LDO:

Here it's C26 that concerns me (that is just a sample, there are more ICs that are powered from "+3V3AN" rail). It is ceramic cap and I'm not sure if it will or will not cause a instability in my LDO.

I would assume it depends on the distance between LDO and that ceramic cap.

If this hypothesis is correct I have no idea what distance would be sufficient.

UPDATE:
According to comments, it is a problem.
One solution would be to add a resistor (R7):

Unfortunately that would deteriorate line regulation.


texts:
vacuum cleaner circuit diagram, missing live switch

Attached is a circuit for a vacuum cleaner. Pretty basic, mains, snubber, universal motor. I forgot to draw the switch (spst) on the live wire, before the capacitor junction.

Motor 800W 240V universal

The crimp that connects the wire to the motor (shown with arrow) is dodgy and so is wobbly/not a secure connection. When the vacuum cleaner is turned on, ie switch is closed, immediately with a pop and a flash, the crimp is thrown from the terminal of the motor.

My question is, why would this happen? I am thinking that the spark is ionising the air, and the pop is forcing the crimp off. I also considered that the higher resistance in the bad connection is creating somesort of magnetic flux, perhaps repelling both crimp and terminal from each other, because it uses AC. My last and final idea was the inertia of the spooling motor caused the crimp to flick off.

Maybe it is all three?


texts: Powering 5m of WS2812 LED Strip. Power jack doesn't support 10A

texts:
I want to control 5m of WS2812 LED Strip with my Raspberry Pi. I found this tutorial: http://popoklopsi.github.io/RaspberryPi-LedStrip/#!/ws2812
There it is stated, that one LED consumes a maximum of 60mA, which makes 9A for 150 LEDS on a 5m strip.
I found a 5V 10A Power Supply, but I didn't find a power jack, which supports this much amps. Most support a max of 5A. Maybe there's another way to connect the power supply to the led strip ?

Did anyone build something similar and knows how to power the strip in this case?


texts: Multiple sensors and control with microcontrollor

texts:
I'm hoping that this question doesn't come off as too general/opinion based, and will attempt to focus it.

I recently completed a project for a rocketry competition in which we controlled a pan/tilt camera on the bottom of a lander ejected from a rocket. We had to control the camera to aim at targets on the ground, image them, process the images and identify the targets by color. We used two servos (pan/tilt), a GPS module, and a 10 DOF board(Gyro/Acc/Temp).

The approach we took was to use a Arduino to handle the pan/tilt, the GPS, and the 10DOF board. This was communicating with a raspberry pi via I2C and acted as the master while the Arduino was the slave. The pi handled the image taking and processing.

In doing this, we had issues with the overall memory usage on the microcontroller(the code for the pan/tilt was quite intensive) and being able to get all the needed data from the different sensors and communicate it back to the Pi. We used interrupts and tried to optimize the code as efficiently as possible.

My question is, for projects like this where there are many sensors and a lot of processing, is it in my best interest to make up a custom board with separate atmega328's for each sensor(or at least one for sensors, other for logic)? If so, is I2C the recommended protocol to be used?

As I work on a lot of computer vision type projects where I will need to use a PI or other computer to process the images, and also be able to obtain sensor data and calculate quicker than the Pi can handle, a elegant and fast solution to this would be much appreciated.

Thank you


texts: Inspection/QA Criteria for Selling Electronics?

texts:
I'm a software developer who has recently taken up a penchant for home electronics and personal robotics. I'd like to start building a prototype for a small device that I would sell though a website, and I realized that I am now in very unfamiliar territory.

With programming, there's no "legal" regulatory standard I have to write my software to. If I was a construction contractor, I'd have to make sure my work was inspected by a building inspector. But not in software. In software, you just have happy or unhappy customers, depending on whether your software works or doesn't work. But there are no mandatory inspections, QA checks or laws governing how I write my software.

What about electronics? Believe me, I have no aversion to researching this on my own through Google, but I don't even know where to begin looking! I would imagine that there would be some regulation with electronics devices, because of electrical, fire or general safety hazard potentials. But everything I've searched for so far comes up a cropper.

I ask because I was recently pointed to a website that is selling home-built robotics (called EZ-Robot). I've scanned their site high and low, and the only thing I see is a legal disclaimer saying that you are purchasing their products "as-is" and assume all risks.

So on one hand, I see the argument for regulation, but on that site and others I don't see any evidence of such. Can anybody weigh-in on what the industry regulatory standards are for home/personal electronics/robotics? Or where to find them? Thanks in advance.


texts: Why do capacitors lose capacitance in series?

texts: Unlike rechargeable batteries, capacitors have a lower capacitance in series. Why is this and if I charge each cap separately and then put them in series, will it still be a lower capacitance?


texts:
I'm trying to make a FM transmitter work properly. I built the following circuit :

I can synchronize with 94.8Mhz channel on any FM radio, I know that because the original sound from that radio is eliminated and I start to hear sound (hollow sound) each time I tap the microphone. I can also hear (sharply) any whisper I make close to the microphone.

The problem is: I can't hear normal human sound and words spoken through the mic, they seem not to pass on to modulate the carrier. I tried to replace the mic and electronic 10uF coupling capacitor but that didn't fix it. Any idea why such situation can occur ?

Oh yes, the microphone is an electric mic:


texts: maximum emitter base reverse voltage limiting when driving with op amp?

texts:
This is part of a larger circuit, but problem area is shown below. In simulations (of the larger actual circuit not shown), the base voltage of Q1 drops to about -6.35V. Can this damage Q1 (2N3904)? What if the base voltage drops to -15V? Current flowing through emitter base with base at -6.35V is in pico amperes (~25pA).

If this is a problem, how can I limit base voltage between 0 and -5V, without limiting op amp supply voltages?

PS: This is for a bench power supply. I need a +15V since there is a differential amplifier for voltage sensing and I lose accuracy at low output voltages if op amp +V supply is low. The -15V tracks the +15V, otherwise I lose accuracy at low voltages and current sensing (due to greater offset).


texts: Is TDI shifted on move from SHIFT-IR to EXIT2-IR in JTAG?

texts:
I'm struggeling with analyzing a JTAG signal. You can see the signal below. The state machine starts in RUN-TEST/IDLE (green):

As far as I understand the standard and the trace lines, 00100 should be shifted into IR. However, the decoder (sigrok/PulseView) already shifts TDI into IR on the move from CAPTURE-IR to SHIFT-IR. In addition it does not take into account the last bit which should get shifted into IR when TMS is asserted to move to EXIT1-IR.

While the first bit is not much of a problem (it will just fall off the chain), the last bit (MSB) is actually relevant. What am I missing? I doubt the decoder is wrong as it's widely used.

The following picture illustrates my understanding of JTAG:


texts:
I have to connect a two-wire cable in a continuously extremely humid & warm environment. While there are no safety issues due to low voltages the connection corrodes within a few weeks: the corrosion even creeps a way into the wires.

I am looking for a way to make the connection water- and vapour-tight without making it too bulky or too permanent.

I ruled out classical boxes for electrical installations with seals because they are too bulky (about 10 cm minimum) and self-fusing tape because it is practically impossible to open.

Any suggestions on what to use? I am ok to relax the vapour-tight requirement if good corrosion resistance can be achieved without it.


texts:
I'm working on constructing a do-it-yourself version of the Arduino Uno on a breadboard and then protoboard.

According to the Eagle files available for download here, they use an ATMEGA16U2-MU(R) MCU for the USB to serial interface / programming interface.

Is there a DIP-style Atmega equivalent which would perform the duties of the ATMEGA16U2-MU(R) with no modification to the bootloader provided for the Arduino Uno? If so, what might this be?

Is there another approach I should be taking? Preferably, I'd like to retain the Uno design's capability of being able to burn bootloaders on top of uploading programming.


texts: How fast do tantalum capacitors self-heal?

texts:
I am troubleshooting a design that uses a 47 µF 20 V tantalum SMD cap across a 15 Vdc rail.

While the derating guidelines I follow dictate a 50% voltage derating for tantalum caps, the design I'm looking at slipped through the cracks, and 15 Vdc is applied continuously.

Is it possible that these tantalum caps could short from over-voltage and then self-heal, causing the overall circuit to malfunction for a moment, but upon later inspection appear fine?

These caps are across the rails of a relay driver IC. Supposedly relay contact closures were detected, but no commands from the micro that would result in relays energizing were recorded.

If self-healing tantalum caps are a possible culprit, what is the timescale for the self-healing process? I have not been able to find any data with regard to healing time.


texts: What is the best way to get 7V from a benchtop 10V supply?

texts:
I have a 50 ohm load I am trying to drive at 7V.  I currently have a 10V supply with a 10kohm potentiometer but I am expecting to run into trouble when I connect it as a voltage divider.  I looked online for a 7V supply but I couldn't find much.

What is the easiest way to get 7V that can drive this load? I can purchase some equipment but would like to keep it to a minimum.


texts: In a datasheet of a embedded device (this one in my case) what does it mean that the PCIe bus is conneceted to a socket that says "Full-size Mini-PCIe (colay mSATA)"


texts: Powering a 1 watt LED using a 3 V coin cell

texts:
I was hoping to power a 1 watt LED (would be great if this is capable of powering 2 or 3 watt LEDs) with a 3 volt coin cell.

Will the coin cell be able to output voltages and amperages that are within acceptable levels for the LED's operation? Essentially will the LED or battery fail faster than is considered normal?
If I need to add resistors to the circuit, what kind of heat levels will they produce?

The battery would ideally be a CR 2302 lithium cell, chosen due to a size requirement.
The LED has a forward voltage of 3.2-3.4 volts and a forward current of 350 mA.


texts: Sub 1 GHz communication - long range at 500kbps. Is my range estimate roughly correct?

texts:
When researching long range medium bitrate RF comms I came across the TI range. The TI CC1201 transceiver claims -97dBm sensitivity at 500-1000kbps. If the system is on the 868MHz band which is apparently free to use at transmit levels up to 25mW, a  full system with two 2dBi antennas should have a max range of ~1.8km - based on the Silicon Labs calculator.

Will other losses in the system lead to much worse performance? (i.e. if the design between the transceiver and antenna is 'normal' with usual losses, not badly designed but realistic and compact)

EDIT: here's another potential frequency band, 863-865MHz with no duty cycle limits. The maximum power is only 10mW but this could still be viable?


texts:
I'm building a mesh network with xbees, arduinos and sensors.

Right now I have 2 Xbee routers and 1 coordinator.
Each xbee module has an arduino attached. To communicate from the router to the coordinator, I use the Serial.println() function.
Is it possible that when 2 routers communicates via serial to the coordinator, the data overlaps?
For example if from Router 1 I'm sending "HELLO" and from router 2 "World", is it possible that the coordinator will receive both of them at the same time and will output "HELworlLOd"?
Or does the coordinator just takes 1 "data package" at a time? If so, what happens if the coordinator is receiving some data from router 1, and at the same time router 2 sends a package? Does it get lost? Does the zigbee protocol takes care of that and makes sure that the router sends it again? Do I have to implement this in my code?

Thanks!


texts:
It is known that a coaxial cable needs a balun to provide an optimal supply of a dipole antenna, because of the common mode current that comes back to the transmitter through the external surface of the shield (as some users clearly explained me in my previous question).
Now, I was asking the same thing about a microstrip line.

Can we apply the same logic applied for the coaxial cable analysis? Can we say that:

thanks to skin effect, current normally flows only in the upper part of GND plane.
when the microstrip conductors are connected to a dipole, a reverse current flows in the lower part of GND plane
to avoid this problem, we use a balun

correct?
I was thinking that this reverse current should be present also in the strip. So why is this line unbalanced? Because these two reverse currents are not equal and opposite?

I've seen that sometimes such a kind of balun is used (tapered balun):

Well, I'd say that even in this case there will be reverse currents in both conductors (in the upper part of the upper strip, and in the lower part of the lower strip). Isn't it a problem because both currents are equal and opposite since the two conducting strips are identical?


texts:
I would like to measure the power of a very unusual ac waveform. Please say if this could work...

Construct a black pvc tube with a very sensitive light to voltage converter TSL257 in one end,
and a tiny lamp in the other end, seal both ends.

Drive the lamp with the waveform to be measured and record the lamp intensity voltage from the TSL257.

Drive the lamp again with a battery to the same intensity and calculate the power ( Volts @ Load x Amps )

Would this method be similar to the old "Hotwire" ammeters?
Thanks.


texts: Can you get an infrared remote's signal modulation with an Arduino?

texts:
Let me preface that I am very much an electronics noob. I am decent with programming.

I have an RCA L40FHD41 HDTV that I bought in 2010. I have tried using many universal remote with this TV, but after trying hundreds of codes, nothing works. I bought a cheap replacement remote (RCA 276045 TV Remote Control) but it is hit and miss when it decides to actually work. I was hoping I could use an Arduino with an IR receiver to get all the IR codes for the remote when it is behaving, then try to make an Arduino IR transmitter to control the TV.

I had a piece of code that would basically take a raw IR input, and output it via an IR LED. To test, I pointed the IR LED at my PCs media remote receiver, and pressed some buttons on the PC media remote. That worked. But when I pointed the IR LED at the TV, and hit buttons on the TV remote, nothing happened. I think that the TV uses a difference modulation. I have read that most standard IR uses 38Khz. I want to find out what modulation the TV remote uses. Is there anyway to get that info using an Arduino and a IR receiver?

Edit: Someone said it might be a decode issue. That cannot be the case, cause I used another piece of example code to get the timings and HEX codes for all the buttons, and when I pressed the same button multiple times, it got the same results, consistently. Here is an example of the output of that piece of sample code:
POWER BUTTON

Code      : 6A68351E (32 bits)

Timing[51]:

 +4050, -3400     + 800, -1650     + 800, -1600     + 850, -1600
 + 800, -1600     + 800, - 650     + 800, - 650     + 850, -1600
 + 800, - 650     + 800, -1650     + 750, - 700     + 750, -1650
 + 750, - 750     + 700, - 750     + 750, - 700     + 750, - 700
 + 750, - 750     + 700, -1700     + 700, -1700     + 700, - 750
 + 700, -1750     + 650, - 800     + 600, -1850     + 600, - 850
 + 600, -1800     + 600

unsigned int  rawData[51] = {4050,3400, 800,1650, 800,1600, 850,1600, 800,1600, 800,650, 800,650, 850,1600, 800,650, 800,1650, 750,700, 750,1650, 750,750, 700,750, 750,700, 750,700, 750,750, 700,1700, 700,1700, 700,750, 700,1750, 650,800, 600,1850, 600,850, 600,1800, 600};

EDIT: I got a piece of code working to turn the TV on/off. Not sure what is different between the code that simply took a raw input and broadcast it.


texts: Distortion sine waveform from LT1227 amplifier

texts:
Schematic for the amplifier:

Before connect it to amplifier circuit:

Why the sine wave will distorted? any possible reason? is this due to noise?
blue is the input signal of an amplifier and green is the output signal


texts: Transient response to rectangular impulse of a cascode common source amplifier

texts:
There is a cascode amplifier seen on the picture below. A rectangular pulse with amplitude of 10 mV is sent to the input.

Due to large negative amplification gain of the cascode amplifier, output first decreases (at the left front of the impulse) and then increases (at the right front of the input signal).

What I cannot understand is why settling time at the right front is much larger than settling time for the left front. That is, why does transition of the output from max to min happen quickly, while transition from min to max takes a lot of time? Or in other words, why the output response to the left and right fronts of the input impulse is not symmetrical (long at the right and short at the left).

I used LTSpice for simulation. SPICE Level 3 model was used for long-channel transistors.

Several clues I found out.
1) Settling time at the right front is larger for larger load resistances. The response becomes symmetrical for smaller loads (e.g. 1 MOhm).
2) The effect is related to non-linearity of M2. The response is symmetrical for small amplitude of input signal. E.g. for an amplitude of input impulse of 1 mV, the output is symmetrical (settling times are the same). Note that M2 triodes when the output voltage is low.


texts: In CMOS technology, why does the substrate always have to be p doped? When we need a p-channel MOSFET, we generally create an n-well into it and create p source and drain regions. Why does the balance have to work that way, why not the other way round?


texts: Why does grounding the negative line to the earth eliminate the noise in circuits?

texts:
I'm using an oscilloscope and observing the voltage output of an amplifier.

First case: Osc. is not grounded circuit is not grounded and I see a very distorted signal.

Second case: I ground the negative output of the circuit(which directly goes to the osc. as well) to the earth and the output signal is neat.

My question is, even though it is a well known phenomena, why does grounding to the earth only eliminates the noise and does not affect the original signal? Why does 'only' noise currents flow to the earth?


texts:
I've got my hands on a bunch of old garden lights with solar panels, and of course I disassembled them and found that they use just one 1.5V accumulator cell to light up the LED.

Just for illustration

I've managed to get the schematic from the PCB (I hope it's correct):

R1 ... 10k
R2 ... 100k
R3 ... 5k1
C1 ... 100pF  (marking 101)
L1 ... 150uH  (translated from colors)
L2 ... 410uH  (translated from colors)
T1,T2 ... S8050D
D1 ... 1N5819

I thought I'd replicate it to get a simple and cheap 1.5V -> ~ 3V converter, but I'm not really sure how it works. Also, there's some logic to turn it off during day and on at night, which I'd rather remove.

The R and K wires (red and black) are connected to the 1.5V cell, and B and K (blue and black) wires are connected to the solar cell.

Some ideas, maybe wrong:

I assume the diode prevents current from flowing through the solar cell at night, but I'm not sure about T2's purpose. Could it be that it inhibits the converter when the solar cell is in sunlight?

Then of course the converter is a big enigma to me, but I'll just take it that it works somehow - I'm not really good with transistors.


texts:
My ceiling fan just stopped suddenly today, i took it apart and found a resistor had overheated and fused itself onto the plastic housing. I swapped the entire circuit board of another similar fan and it now works fine. But i needed to replace this faulty one and I thought a replacement of the resistor may do the trick. Thing is I can only tell its a 200 ohm 5% tolerance resistor. Anyone here can tell if its a metal or carbon film one? And the power rating?

Or if cant tell visually, its there anyway to measure them on a working model?

Thank you so much


texts:
I used an IRFZ44N MOSFET to build a switching circuit to light up a bulb from a 12V car battery.
It works but it is not stable.
When the bulb is off, after a while it glows and increases.
When the bulb is on, little by little it goes dim.
First I tested it on Proteus and then I did it with real hardware.
Can anyone tell me how to make it stable?
I want the bulb to extinguish when the push button is pressed.  It should then stay off.
I have a good heat sink for the MOSFET. Can't we use push button?


texts: Can I use a photodiode as a switch for a shift register?

texts:
Let's say I have a photodiode,  a shift register (74HC595) and a 5V source, and I connect these as:

5V source -- photodiode -- shift register data input.
(And other voltages to feed the register clock etc)

Do I need a resistor with the photodiode, or will it suffice to put the photodiode before the shift register?

What I am trying to do here is essentially use the photodiode as a switch which allows the register input to be set to 1 only when light falls on the PD.


texts: PIC18LF24K40 I2C read and write using Polling method

texts:
I'm trying to implement read and write routines using Polling method for a PIC18LF24K40, write seems to work, but not read. I cannot figure out what i am doing wrong.

EDIT: Reading a byte stored in a register on a slave chip:

   void read_LDC_reg(U8 *dest_addr)
   {
      U8 temp=0;

      if( ( check_for_bus_free_iic() == 1) )
      send_start();

      PIR3bits.SSP1IF=0;
      I2C_wait();

      send_address(U8_LDC_I2C_ADDRESS,READ_BIT);

      send_start();
      SSP1CON2bits.RCEN1=1;

      while(SSP1STATbits.BF==0);
      temp=read_from_slave();

      PIR3bits.SSPIF = 0;

      dest_addr =  &temp;

      send_stop();

}

send_start() looks like this:

void send_start()
{
    while(SSP1STATbits.RW);          // wait for write to complete
    SSP1CON2bits.SEN=1;              //set start enable bit

    if(PIR3bits.BCLIF==1)
        PIR3bits.BCLIF =0;  //Clear collision bit in PIR register

    while(SSP1CON2bits.SEN);         //waits to get cleared by hardware
}

I2C_wait looks like this:

void I2C_wait(void)
{
    while( (SSP1STAT & 0x04) | (SSP1CON2 & 0x1F) );

    PIR3bits.BCL1IF=0;

}

send_address() looks like this:

void send_address(unsigned char addr,unsigned char ReadWrite_bit)
{
    unsigned char temp=0;
    temp = ( (addr <<1u ) | (ReadWrite_bit & (unsigned char)0x01) );
    write_to_bus(temp);

}

write_to_bus() looks like this:

void write_to_bus(unsigned char data)
{

    send_start();
    I2C_wait();

    send_byte(data);
    I2C_wait();

    send_stop();
}

read_from_slave() looks like this:

unsigned char read_from_slave(void)
{
    unsigned char rcvd_byte=0;

    rcvd_byte = SSP1BUF;
    return rcvd_byte;
}

I am getting unexpected values from the slave register, i do not know why i believe i have initialised correctly, i can see the SCL and SDA waveforms on Oscilloscope.

EDIT: Hardware is fine, I2C works perfectly when i use the I2C Driver code generated from MCC(MPLAB Code Generator), i want to reduce the overhead caused by MCC in my project, thats the reason im going for I2C using Polling option.


texts: Controlling PWM with an external oscillator and a JFET

texts:
I'd like to control the pulse with modulation of a VCO with an external oscillator (triangle wave). The PWM circuit is a comparator fed with the triangle wave output of the VCO. The VCO schematic is a classic design taken from the datasheet.
I'm trying to control the pulse width using a JFET used as a variable resistor, but the output of the JFET the result is a strange behavior of the CV, a triangle wave followed by a continuous voltage like in the screenshot attached (in yellow the original CV signal and in light blue the output of the JFET).
I don't know how to go on... anyone could help me to resolve the problem? Thanks!


texts: Converting (symmetrical) line to neutral to line to line components

texts:
I have given the unbalanced line to neutral three phase voltages, and I have to find the unbalanced line to line voltages. Therefore I have calculated the line to neutral (symmetrical) components using decomposition, but I am not sure how to convert the line to neutral components into line to line components.
Once I can get the line to line components, I can apply synthesis to obtain the unbalanced line to line voltages(three phase).
Can anyone explain a little bit theory on this topic, please
It would be much appreciated.

Thanks


texts: Capacitor discharging theory vs experiment doesnt match

texts:
I am trying to discharge my 1F capacitor over a 47 ohm resistance which i connected in parallel with the capacitor . İ have calculated the time it would take to discharge from 5V to 4V as 10.55 seconds with the following formula :
 V(t) = V0 * exp(-t/RC). Where V(t) is 4 Volts and V0 is 5 Volts. But whenever i connect the oscilloscope to observe the change in voltage i see this

İt takes exactly 0.2 second from 5v to 4v, any idea that explains why there is a big gap between my anticipated value and the one i measure is appreciated . Have a nice day people :)


texts:
I was thinking about selecting R & C values for an RC filter, so that it consumes less power, in the overall circuit.
Thinking about it, a larger value for R means a larger \$I^2R\$  loss.
But a Larger value for C means requires more current to charge.
Can anyone suggest on how should I go about selecting these?


texts: USB car charger input 10vdc instead of 12 VDC

texts:
I am running a project where I will have a small steam engine turning a dynamo. the dynamo produces 12VDC no load and 10VDC 10 watts under load.
My plan was to buy a car usb charger and connect it up as a fun experiment with my son as an alternative way to charge his iPhone and learn about the industrial revolution.
Trouble is how will a car charger cope with 10VDC instead of 12VDC input?

Thats my question and thanks in advance for your help.


texts: Project of a capacitive finger to test finger Print sensor

texts:
How can I choose the best material to use in a project of a "capacitive finger"?

The capacitive finger will be used to simulate a human finger , and will be used to test Finger Print Sensor or Touch Screen.

I understand that the best probably is the material more similar to our human body in terms of capacitance. Is it correct?


texts: Why do I need a ground when simulating a circuit? I thought voltage was relative between two nodes!

texts:
Electronics is very new to me.

I took the most basic circuit I could think of: A voltage source of 1V and resistor of 1 Ohm

As far a I understand I should get a current of (I = V/R) 1 Ampere. But the simulation does not give a solution and said I should have ground.

Why should I have ground if I have a voltage source that gives potential differences from its two sides?

I attach the circuit:

https://www.circuitlab.com/circuit/839aaj6y5a6t/simplest-circuit/


texts: Over-voltage protection for microcontroller ADC input pin.

texts:
I have a microcontroller with a 3.3v ADC input and I want to protect it from over-voltage.

My microcontroller already has some input protection diodes but I don't want to rely on them alone. This question is not new and I've seen many designs use an additional diode connected to the power rail or a Zener diode. There are a few answers in these forums that already describe these solutions and their pros and cons.

I was wondering why not use a PNP BJT as an over-voltage protection solution like on the illustration below.

This circuit should start acting around 3.3V and will clip any voltage above 3.6V or so. This level can be changed by playing around with R6 and R5 to set the voltage of the base of the transistor taking into account the typical 0.6V base-emitter diode drop.

I saw the suggestion of using a PNP BJT as a voltage limiter in a note from Microchip, but generally not in any design or suggestion in these forums. Any idea why this design does not seem to be used?


texts:
We have a NAND2 gate and we want to find which input leads to the worst case tpHL delay.
I can understand that for input 00 and 11 is the best case to charge and discharge. I also understand that for tpLH delay the worst case is from 11->01 . But what is the worst case for tpHL 01->11 or 10->11 ?

picture for worst case for tpLH


texts:
I have a 5*7 dot matrix in my FPGA, and I need to "walk" a dot. The data is 35 bits long, and only one bit should be 1 (visible). The upper-right dot is (0;0), the lower-left is data[34]. The problem is that I can't figure out how I should shift a '1' to the specified position.

reg [34:0] data;
reg [ 2:0] x, y;

always @ (posedge clk16M) begin
    if (rst) begin
        x    <= 3'b0;
        y    <= 3'b0;
        data <= 35'b1;
    end

    .. calculate x and y ..

end

always @ (*) begin
    data <= 35'b1 << (x * 3'd7 + y);
end

It doesn't move the dot, however, x and y's value are fine. They change when they should.


texts: What is this electronic set up with a red light on top of it?

texts: Anyone can tell me what this is ? Not sure if it exactly pertains here in the electronics forum but I think it does . What is this set up near my house and why is there a really bright red light on top of it https://imgur.com/a/9sYNkCd more pics https://imgur.com/a/VnSxd4t


texts: For what type of signals group delay of a filter should be taken into account?

texts:
Here is an example showing the effect of group delay for different type of filters. And here are some conclusions from the site:

  Bessel: Has essentially zero overshoot. That was one of the design objectives. Has the smallest delay.

  Butterworth: Overshoots about 16% of the transition. Has a larger delay.

  Elliptical: Overshoots 20%. (Note that different elliptical filters will have different overshoots). Has delay about the same as
  the Butterworth but has a slightly different characteristic.

When it comes to group delay always a pulse input and output in time domain is given as an example of the side effects. And overshoot is given as an example to the group delay effect.

If the signal we are measuring is continuous voltage but not a pulse or discontinuous signal, are there also circumstances when group delay should be taken into account?

Let's say we have an analog voltage input coming from a transducer which is not pulse. We can sample this voltage signal through an anti-aliasing filter. In this case can there be any distortion in frequency domain(when we take FFT) depending on the filter type's group delay? In other words does the group delay corrupt frequency domain?


texts: Can we convert a an AC supply which outputs a square wave to a sine wave?  Many uninterruptible power supplies (UPSes) produce square waves.  12V adapters can't bear this square wave, but can handle sinusoids.  How is this conversion possible?


texts:
I am reading lpc1347 manual (GPIO section) and I have seen one sentence which I don't understand. The problem is WORD register which controls pin states. Quotation:

"Each GPIO pin has a word register in this address range. Any byte, balfword or word read in this range will be all zeros if the pin is low or all ones if the pin is high..."

I can access WORD register via

pGPIO->B[0]

It's word access but how can I read it via halfword or byte? Should I make a own pointer and read value from memory? If yes, should I start read from LSB or MSB?


texts: Pick largest of several voltages with analogue comparators

texts:
This is not an XY problem. I have already decided that the best way to handle the actual application is to use a multiplexer and ADC/MCU to measure all the voltages.

However, I am always keen to find a neat new way to hook up opamps or comparators. This is an 'does this configuration exist in a neat way' question? I've not managed to find one yet through the normal search routes.

Inputs - 6 or so positive signals in the 1v to 2v range

Outputs - one amplifier or comparator output per signal, where that corresponding to the largest (or equivalently the smallest) voltage has a unique, perhaps high output, and all the others have a low and similar output, such that they are already logic-usable levels, or can be compared against a simple threshhold to give logic levels.

Ignore input voltage offsets as being insignificant with respect to the input voltages. Hysteresis is optional. Scalable to any (reasonable) number of inputs.

It's relatively easy to output true for all the signals that are above the average of the inputs. Just form the average with an equal resistor network, then use this voltage for the reference input to each comparator.

What I feel should be possible is some sort of diode feedback, like in an absolute value circuit, where the gain of an amplifier reduces the diode drop to insignificance, and the 'winning' amplifier/comparator silences all the others. However, I've not managed to find a simple configuration yet.

What's a simple configuration? One amp per input, with at most two additional shared ones. One diode, or at a stretch two, per amp, with at most 4 resistors per amplifier, and a few extra shared, with as few as possible needing matched values.

Any thoughts?

(edit)

I have the outline of a solution which involves an integrator which controls a common reference level. This level ramps down if no inputs exceed it, and ramps up when any input exceeds it. The level will tend to hunt around the largest level, with the comparator output corresponding to the largest flicking on and off. Replacing the comparators with amplifiers and paying attention to stability may result in a steady output that's suitable.


texts: protection IC stopping battery from charging

texts:
So, I'm using an AP9101C as protection IC and MCP73811 as a charger IC for a single cell lipo like this:

The load works fine and when I connect +VDC (5V), suddenly CO of AP9101C goes to 0 preventing the battery from charging and showing 4.2V on +BATT to GND and 3.6V on the battery itself (0.8V forward on diode of Q4 or 5). If I short Q5, the battery charges normally and CO even goes high, but when I remove the short, it stops again.

If I would connect VSS of the charger IC to -BATT, I would bypass Q5 (and the overcharge protection), but the datasheet of the charge IC specifies to connect charger +Batt and Q5 as I did.

Adding diodes to Q5 (and Q6) will not help I think because it would still cause a forward voltage.
Anyway, what am I doing wrong and how should I fix this? Or can't these two IC's work together?

Any help is highly appreciated, I'm really stuck.

Added a screenshot of the wireless reciever with another capacitor to GND, but this one is a good 5cm away from IC2 and parrallel to the induction coil, so i guess i do need that C4 connected properly:


texts: I2C: How does the Master recognize an ACK from a specific slave?

texts:
I just started learning about serial communication protocols. So I understand there are only two lines connecting a master and many slaves

Master broadcasts the start condition then the slave address with R/W
The slaves compare this address with their inbuilt ones and the addressed slave makes the SDA low.

Question:
How does the master recognise which slave made the SDA low? Is the ACK bit just there to confirm that such a slave exists, doesn't the MASTER  know which slave sent the ACK?


texts: Setting the address of MCP23017 IO Expander when using Multiple

texts:
I'm trying to use the MCP23017 I2C port extender which has 3 addressing pins to be externally biased to set the I2C device address.

How should I connect the 3 addressing pins to select the I2C address that I want? I was not able to identify a table mapping the biasing to the I2C address in its datasheet.

Also, should I be biasing by connecting some address pins to GND, some to 5V of my Raspberry? Diagram below show show I am currently wiring up three MCP23017 to a single Raspberry 3. Does the wiring look ok?

[Link to clearer image]


texts: Voltage divider for a voltage range spanning negative voltages

texts:
We have a sensor giving out a signal between -10 V and +10 V, and a signal acqusition device that only accepts voltages between -2 V and +2 V. So we need to scale down the signal into the smaller range. As possible solutions I have identified:
A. Use a voltage divider
Following the information in this page: https://learn.sparkfun.com/tutorials/voltage-dividers, I could use two resistance, R1 = 5000 Ohm, and R2 = 1200 Ohm.

I am not sure what am I allowed to use a Ground. Both devices (sensor and acqusition) have a ground connection, which are connected to each other. Can I use this common ground as for the ground of the voltage divider ?

The impedance of the signal acquisition device is specified as 1 MegaOhm. Why is this value given at all? Should I include it somehow in my voltage divider calculations ?

B. Buy some off the shell device
I have seen some voltage down regulators, but they appear to only address power applications. I assume they are too noisy to be used for sensor read-out. Furthermore, there appears to be no device offering downscaling negative voltages.

Are there commercial voltage downscaling devices made for sensor reading ? I am not familiar in this area and I might be just ignorant of a family of devices that already does this in a plug an play manner.


texts:
During my current PCB design using Altera FPGA, I happened to come across knowledge that Altera EPCS devices are to be used for FPGA configuration. After further research, I realized the same job can also be done by normal generic Flash-NOR of any make. In fact Cypress has an Application Note to this effect to (let's say) promote their own Flash chips for this purpose.

My question (and this baffles me truly) is that what's so special about the Altera chips that they charge $37 for the same as Cypress and others' chips which cost only 60c? Also does anyone know special cases or applications in which Altera EPCS chips are preferred?


texts: Battery charging and discharging problem

texts:
I have designed a battery charging and discharging circuit. The main purpose of this circuit is to charge the battery and then discharge, one operation at a time. I have also added a hysteresis of 3.4V and 4V.

Battery voltage is compared with the set hysteresis voltage and when the battery voltage reaches 4V, the charging is then stopped and then the battery is discharged to load; this is controlled by MOSFEST as a switch. When the battery voltage reaches 3.4V the switch is then turned off and then charge the battery.

It works in the simulation and it also works when I use power supply as a battery. The problem is when I connect the real battery the following things happens,

When the battery is charging and its voltage is around 3.97 the discharging takes place. At this point it is charging as well as discharging, why doesn't it reach it 4V?
Then I checked the output of the comparator which controls the switch, then I noticed that the output of the comparator is going crazy on and off (5V and 0V).

Why is the hysteresis not working and is there any way I can solve this?

this is my schematic

this is the new schematic, easier to understand :)


texts: Example: Calculating the instantaneous current flow

texts:
Page 9 of Practical Electronics for Inventors, Fourth Edition, by Scherz and Monk, gives the following example:

Example 2: Charge is changing in a circuit with time according to
$$Q(t) = (0.001 C) \sin [(1000/s)t].$$
Calculate the instantaneous current flow.
$$\begin{align} I &= \dfrac{dQ}{dt} = \dfrac{d}{dt} [(0.001 C) \sin(1000/s \cdot t)] = (0.001 C)(1000/s) \cos(1000/s \cdot t) \\ &= (1A)\cos(1000/s \cdot t) \end{align}$$
Answer: If we plug in a specific time within this equation, we get an instantaneous current for that time. For example, if $$t = 1,$$ the current would be $$0.174 A.$$ At $$t = 3 s,$$ the current would be $$-0.5 A,$$ the negative sign indicating that the current is in the opposite direction --- a result of the sinusoidal nature.

The part that I'm not understanding is where the author is plugging in $$t = 1$$ and $$t = 3$$ to get the aforementioned values? If we plug these values into $$I = (1A)\cos(1000/s \cdot t) ,$$ which is our calculated solution for instantaneous current flow, then we do not get the specified values?
I would greatly appreciate it if people could please take the time to clarify this.


texts: What about using LiFePO4 battery as my RV Battery

texts: I saw a battery(CALB CA100 100AH lifepo4 battery cell) on this website that looks good and I plan to build my own battery bank. How about this battery? Is it suitable to replace my lead-acid battery?


texts:
I'm thinking of using an op-amp in a measurement circuitry. The sample will be in series with the op-amp and will be subjected to at most 50V AC (amplitude) at a maximum of 324kHz (although more likely at 60Vpp and 324kHz).

I'm not sure what to look for in my op-amp or if the fact that I'm applying such high voltages and frequencies to my sample will be a factor in choosing an op-amp.

Hope someone can point me in the right direction towards choosing the right op-amp! Thanks.

EDIT: I forgot to mention that it'll be used as current-to-voltage converter.

EDIT: Here is the circuitry that I will be building. The sample here refers to my dielectric sample.


texts:
I am planning to buy these current transformers which I am wanting to use to measure electricity consumption of a device where household power is 220V, 50Hz. I want to use these in combination with a microcontroller's analog-to-digital converter. I think I will need to rectify and smooth the output of these so the signal is acceptable for an ADC. Here is the circuit I've come up with (current transformer is signified as an AC current source:

simulate this circuit – Schematic created using CircuitLab

I have annoted this to try to convey what I was trying to accomplish. I need to be able to sense current between zero and 18A.

Is this design sane? What should I be thinking/worrying about?


texts:
I have some trouble understanding why M1 is in saturation/active mode.

According to Wikipedia a MOSFET is in saturation mode if \$V_{GS} > V_{th}\$ and \$V_{DS} \ge (V_{GS} – V_{th})\$.

However as drain and gate are tied together \$\implies V_{DG} = 0 \implies V_{DS} = V_{GS}\$. Therefore \$V_{DS} \ge (V_{GS} – V_{th})\$ can't be true (\$V_{th} > 0\$)? What am I missing?


texts: Stepper Motor Microstepping with an MCU or Arduino without dedicated Microstepping IC Controller

texts:
I'm trying to make a fully configurable stepper motor controller by directly driving the H-bridges with the MCU, like an Atmel Atmega or other MCU, and use current feedback with the built in ADC, while using the PWM to create a current feedback loop (the ADC would measure across a sense resistor).

I'm trying to get the basics down of what is required to accomplish this. I need to be able to support microstepping as well. I've been looking at the datasheets of the Allegro and TI stepper controller IC's, and have a basic idea of what it needs to do, but the implementation confuses me a bit. I can't find any other projects that accomplish this. It seems that nobody else uses microstepping, or nobody uses a current feedback loop.

Are there any open source projects that accomplish this task? If so, where can I find the source code and schematics of these projects?


texts:
I'm currently trying to change my lamp in my bathroom so I disconnected my current lamp and forgot to write down what the cables were attached to.

There are 3 cables coming out from the ceiling.

-----------------------
      /  |  \
     /   |   \
    /    |    \
   /     |     \
Brown   Blue   Black

Between Brown + Black I get voltage.

Between Brown + Blue I get voltage.

Between Blue + Black I get no voltage.

How can I tell which of these cables are ground (AC 230V)?

Is there any way of measuring resistance/current/voltage to tell what is ground here?

Please let me know if I can provide any more information.

  I'm from Sweden, usually ground is green-yellow here.

  There are two lamps connected to the dimmer so the circuit is split somewhere in the wall.

I ended up connecting blue to neutral and brown to live. Works like a charm.
Read Winny's comment below for more detailed information.


texts: Is it okay to wire an MCU output to an MCU input on the same chip?

texts:
My dsPIC33F does not seem to support routing the comparator to the input capture module. Would it be okay to run a wire from the comparator output to the input capture input?

I'm using a dsPIC33FJ128GP802.


texts:
I have a media center (Pi), where I can control the powering from an Attiny. This is done through a simple powerswitch. What I want to add now is "wake on USB".
I've though of two things that could be neat. One is wake on a simple keyboard press and the other is wake on bluetooth. I have a small BLE dongle that I want to connect to one of the USB ports of the hub and when my phone gets close, it should start the Pi.
This is a conceptual drawing of what I want.

The USB Hub IC (USB2514B) is currently powered from the Pi, meaning that it will be off when the Pi is off. This can be changed. The USB port will have power on all the time.
My idea was to connect one of the downstream data lines from the USB port to one of the ports of the Attiny and simply have the Attiny detect a change in the data lines when the keyboard is pressed.
I think my question is more a matter of the idea being feasible? Is it the right direction i'm going in.
Thanks


texts: averaging circuit when number of inputs is dynamic

texts:
I have sensors that measure the weight of each person in a room and also a sensor to count the number of people(this is an example, my application is similar but not this). I need to find the average weight.
I can use an opamp averager circuit. But the number of people are variable, therefore, I need to change Rf and input branches/resistors (to V-) every time there is a change in number of people. Is there a workaround? Please help !


texts: ESD protection for RS485 with power bus, without earth

texts:
On my board there is a 4-pin connector as follow:

+24V DC (up to 6A)
RS485/A
RS485/B
GND

On the system there is no real earth, because there are no metallic parts (chassis, case, structure, etc...).
I'm going to protect the board as follow:

SM712 between I/O lines and the "virtual" earth (see below)
unidirectional TVS with 24V stand-off voltage between power and "virtual" earth
two Schottky in antiparallel between GND and "virtual" earth

The "virtual" earth is nothing but a large PCB trace that runs along the board edge (where the connectors are placed) and is connected to the actual GND at the power input connector through an inductor.
The idea is to provide an easier way for the spike's current to flow instead of enter inside board.
Here a schematic that summarize:

simulate this circuit – Schematic created using CircuitLab
What do you think about?


texts:
Context: output stage of Class-AB audio power amplifier.

In the example schematic above, the output stage is biased in Class-AB via a bias voltage source. In use, output transistors will heat up depending on signal but the bias voltage generator will only track these temperature changes after a while, since it is usually implemented as a Vbe multiplier using a BJT mounted on the heat sink.

So how much does transient heating of the output transistors upset their Vbe, which upsets bias setting and how much distortion does this generate ? This is complicated to measure, it is simpler to measure the transient thermal impedance of each transistor separately and make a thermal model that can then be used in simulations.

So I want to measure how much the Vbe of these output transistors moves around due to transient thermal effects. The way to do this is usually to make the transistor dissipate a pulse of power then switch to a lower power and record Vbe as it cools down. I've seen setups like that:

However this one has two constant current sources, which begs the question: what is the settling time and transient behavior of these current sources and how will that interfere?

So instead I went for simplicity:

The setup is powered by a bench supply. Q1 (the DUT) is wired as 2 Amp constant current source, its base grounded through a resistor. When MOSFET M1 is OFF, there is about the same voltage drop in R1 and R2 so Q1's Vce is a few volts. With M1 switched ON then Q1's Vce is 32.7V. So Q1's dissipation can be switched between low and high power, and the scope can measure Vbe and also hFe (via voltage on R3).

Current draw from the power supply is constant, so I don't need to worry about its transient behavior (and I can check if the supply voltage stays flat). It seems to give results:

So, is this test setup sane and can it be trusted? The other setups I've found on the net are much more complicated, so it feels like I've overlooked something...


texts:
This is my 1st question here and I'm stumped... I spent all my EE classes on programming and ICs. When it comes to AC and motors, I feel worse than ignorant and spent all day trying to research where to begin researching. I know this is a broad ranging question, but please get me pointed in the direction to get this going.

End goal: to have a multiple speed rotating shaft to test ignition systems.

Question: what are the parts/modules/equipment I need in addition to one of the below motors to make the test bench's shaft (1 pound) spin at 1000, 4000, and 7000 rpm?

I have 2 AC motors. I believe one is a stepper motor:

... and the other is an inductive motor:

For a previous project, I rigged up the inductive motor to work while connected to 115VAC (fused and switched) but it had to be manually spun up to start and had less power than the mass of this all would suggest, making me believe I was doing it incorrectly. It got the job done and didn't get hot, so I ran it.

For my test bench, I'll be using aluminum plate to mount everything and likely employ a belt drive. I have a Rapman and already can see that I could buy an Arduino and hopefully convince it to control the top motor in the same way the Rapman uses servos to drive its axes. Towards that end, I could get a gearbox for the motor (looks like this is compatible) and some kind of controller.

I've got a sig gen, an o'scope, milling machine, lathe, computers, pretty much everything but the practical experience to kick this off. Based on the size of my motors and the size of the ones in the Rapman, I'm confident the motors above have the power and size to accomplish what I'm after. Any help appreciated, thanks.


texts: Controlled impedance and differential pairs over M.2 edge connector

texts: I have a System On Module I'm designing that I'd like to fit inside the M.2 form factor. My issue is the dozen or so high speed traces that need to run over the edge connector to my M.2 connector. The connector from TE I'm considering doesn't provide impedance test results, though most documentation states it'd be the same as PCIE (~85 Ω). Assuming I have 4 90 Ω traces for USB and 8 100 Ω traces for my ethernet MDIO interface - how do I handle these over a card edge connector?


texts: Confusing datasheet for JFET 113: Which value for IDSS applies?

texts:
I am trying to build a small amplifier with a JFET J113 to get a high input impedance. I have a problem with the datasheet:
On page 3 it gives a value of IDSS=2mA for J113. However, on the following pages it shows universal curves for all three JFETs J111, J112 and J113.
On figure 5 you find that all these transistors have at least 18mA at VGS=0V.
Which value should I use? If it is the one from page 3, will I have to calculate my own curve using the general JFET-models or can I still somehow use the graphs?


texts: MOSFET depletion region and diffusion electrons

texts:
As Voltage from Drain-Source increases, this means the Drain voltage increases.
I understand why the depletion region around the Drain increases, since it is more positive minority carriers will fill the holes near the drain creating a region of no charged carrier

If the positive voltage just next to Drain and on the Gate increases, there should be a greater positive charge and therefore more diffusion electrons attracted at that point?


texts: Wondering if I can change a cap value in a design

texts:
I am assembling a circuit from the ESP32 reference design.
Looking at value C1 page 18 https://www.espressif.com/sites/default/files/documentation/esp-wroom-32_datasheet_en.pdf (10uF) but I don't have any of these on hand, I have 4.7uF and 100uF.
Would either of those sizes be an acceptable substitute?


texts: Only using ground fill on RF portion of PCB

texts:
I'm designing a 4-layer PCB that has RF components and digital components. I've decided to use a ground fill only on the portion of the PCB with RF components in order to increase isolation between the microstrip lines. Here's a rendered image of the fully-placed/routed PCB.

In the image, the digital circuitry is on the left and the RF circuitry is on the right. I've used via fences and stitching vias to increase isolation and ensure that I don't get any unintentional antennas. Layers 2 and 3 are unbroken ground planes. The last layer is a signal layer without a ground fill.
I've decided to omit the ground fill from the non-RF portions of the top and bottom layers in order to avoid creating unintentional antennas.
Are there any problems with this layout? I can't think of any, but I haven't seen this done before, so maybe there's a problem I'm not thinking of?


texts: Best way to implement outputs pins with leds in a parallel way

texts:
What is the best way to implement an output but with also a led, so I can use the output for other purpose (for example a GPIO for a PIC, or a lot of logic gates) but with a led indicador that the output is in high? I want to preserve the enough current for the led, and have a nice HIGH (5V, 3.3V..) value
I did 2 circuits, is there a better way?

simulate this circuit – Schematic created using CircuitLab


texts: TINA simulation of TPS3701 Voltage Comparator output wrong

texts:
I am using TINA to design a voltage comparator, starting with the Typical Application of page 16 of the datasheet:

When I run a transient analysis, the results are completely wrong, OUTA doesn't rise at 21.6V and OUTB falls at about 2V instead of 26.4V (and rises again around 1V!):

as compared to the datasheet output:

I'm completely stumped; is there a kind soul who could point out my blunder?


texts: Will a resistor connected in parallel with a high-pass filter affect the filter cut-off freq?

texts:
I have a circuit that adds a DC offset to an AC signal. From what I know, C1 and R2 form a high-pass filter. Since the input signal frequency is 50Hz, I would like to reduce the cut-off frequency of the filter as much as possible.

Ceramic capacitors with high capacitance are difficult to find, so instead I'm using high-valued resistors (with a buffer just before the ADC connected to the output).

I want to know whether R1 will affect the cut-off frequency of the filter. I found this similar question, but the answer doesn't give any explanation.

P.S - I would also appreciate if anyone can give suggestions on what type of capacitor to use, since I read electrolytic capacitors cannot be used with AC voltage.

simulate this circuit – Schematic created using CircuitLab


texts: Need some RF help - integrating with a Xemics DP1203 transceiver

texts:
So there are some devices (timing photogates) that use these chips (DP1203C915) to send data out over RF at 915MHz to a box that performs timing and split-time calculations.  I would like to be able to read the data as well.

I was going to just buy a couple of the chips and play around with them, but am unable to find any domestic sources - they seem to be discontinued.

Any ideas on a contemporary component I could try to use instead to read the data?

I was thinking perhaps a software defined radio module would get me going...but then I currently have no idea how to go about decoding the signals into useful data...

Here is the data sheet: DP1203 – 868 and 915MHz Drop-In RF Transceiver Modules

  Virtually no RF knowledge is required to use this RF
  module. Wireless communication can be obtained
  with just the addition of a suitable antenna and a
  microcontroller. The DP1203 fulfils a wide range of
  application requirements, ranging from basic point-topoint
  communication to more complex multipoint
  process control functions.


texts: why not use integral for averaging inductor current?

texts:
I am watching the video lesson on state space representation for dc-dc converter here (at 56:41).

I am a bit confused about the average inductor current expression there.  Why not using the integral to calculate average instead of the one used in the picture?


texts:
This is with reference to this question and this App Note

In the App note, Page 4, it discusses about the steps for multimaster which I have mentioned it below :

  " The following describes the procedures for the operation of this
  sample task.

  The I2 C bus interface multi-master transfer starts on the input of the low trigger to the IRQ0 pin of the master side.
  The master side transmits 128 bytes of data, which have been prepared in the on-chip ROM in advance, to the onchip RAM on the slave
  side.
  The slave device returns the 128 bytes of data received in step 2 from its on-chip RAM to the on-chip RAM on the master side.
  The master side compares the received data in its on-chip RAM with the data transmitted from its on-chip ROM, and confirms whether the
  two match.
  Based on the results of this comparison and the state of arbitration lost, the master side outputs levels on the PE2 to PE0
  pins that indicate the result of operation.
  From the value of the first byte of received data on the slave side, the slave judges whether the partner in communications is master
  1 or master 2, and outputs levels on pins P15 and P14 that indicate
  the state of operation. "

I was not able to understand point 5 and point 6.

What do they mean by "State of Arbitration Lost" and why do we need to show the result of the operation on Pins PE2-PE0? Are we not wasting pins?

Why don't we just send the I2C Signals once, the point 4 is completed and the comparison is satisfied?


texts: What is the purpose of this transistor in this circuit?

texts:
What is the purpose of the Q1 transistor in this circuit?
I understand that I'm going to have approximately 15V for the Vi positive part, and the Q2 transistor works as a current source.
Also, I know that when the voltage on the capacitor is Vc > Vp the PUT will allow the current go through the 50ohm resistor.
But, how does Q1 affect the charging capacitor?


texts: why does the microcontroller pin driving optocoupler is giving 2V even if it is set?

texts:
I have interfaced pin 1^1 of Atmel AT89S51 to optocoupler MOC3041 IC, I set this pin to logic high.

I have connected 220 ohm resistor and red led and then pin 1 of the optocoupler and after that Triac is connected. Relevant section of schematic:

 (Complete schematic)

I am getting 2V on P1^1, and when I disconnect optocoupler connection then i am getting 5V. I don't understand why this is happening and where I went wrong?


texts: Understanding Undervoltage in LTC2965 - 100V Micropower Single Voltage Monitor?

texts:
The undervoltage specifications for this IC is a bit confusing to me as this is the first time I'm working with these kind of circuits.

Aim : I want to monitor the voltage of a battery pack (consisting of 8 x 14 V batteries) being used to power my house. The voltage monitor must be able to trigger a relay to switch to mains power when the battery pack are below a certain level (96 V in this case). I understand that there are voltage monitors designed for batteries in this case that would come with all the settings but I want to switch the battery over to Mains power supply much before the specified 92 V.

In my case the undervoltage shouldn't really matter as my interested voltage range is from 96 V to 112 V. But this circuit designed for 24 V level monitor specifies a term "24 V Undervoltage" which is puzzling me

The spec sheet for the IC specifies the Undervoltage lockout as 3V under Vin RISING condition. Infact the operating range for the IC is 3.5V to 100V which means to say that the IC will not operate below 3.5V.

What do they actually mean by these terms? Is this kind of circuit well suited to be adapted for my aim? Or would it be better for me measure the voltage of single battery and assume rest of the 7 batteries would be of the same voltage?


texts: AC RMS current measurements with oscilloscope

texts:
I am going to measure the AC current(three phases), with a current probe, of a large machine, with an oscilloscope. The scope I am using has the following two options:

RMS: RMS (Root Mean Square) value of the
voltage of the complete displayed waveform.
AC: RMS value of the AC part of a periodic
signal, calculated over all periods on the
display. The AC result is is derived from
the DC and AC+DC results.

Can someone tell me the differences of the two measuring types?


texts: AND gate between 2 std_logic_vector Isn't working correctly

texts:
I am trying to do a multiplication between 2 std_logic_vector
have the following testbech:

LIBRARY ieee;

USE ieee.numeric_std.ALL;
USE ieee.std_logic_arith.ALL;
use IEEE.STD_LOGIC_1164.ALL;
use ieee.std_logic_unsigned.all;

ENTITY mult_tb IS
END mult_tb;

ARCHITECTURE behavior OF mult_tb IS

    -- Component Declaration for the Unit Under Test (UUT)

    COMPONENT Full_vector_multiplier
    PORT(
         ma : IN  std_logic_vector(23 downto 0);
         mb : IN  std_logic_vector(23 downto 0);
         mr : OUT  std_logic_vector(47 downto 0)
        );
    END COMPONENT;

   --Inputs
   signal ma_tb : std_logic_vector(23 downto 0) := "000000000000000000001111";
   signal mb_tb : std_logic_vector(23 downto 0) := "000000000000000000000111";
   signal mr_tb : std_logic_vector(47 downto 0) ;
   signal u     : std_logic_vector(47 downto 0) := (others => '0');

BEGIN
    u<=ma_tb*mb_tb;

    -- Instantiate the Unit Under Test (UUT)
   uut: Full_vector_multiplier PORT MAP (
          ma => ma_tb,
          mb => mb_tb,
          mr => mr_tb
        );

    -- Stimulus process
    process
    begin
        wait;
    end process;

END;

For testing this multiplication module:

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

entity Full_vector_multiplier is
    generic(msb2 : integer:=23);
    port(
            ma  : in std_logic_vector(msb2 downto 0);
            mb  : in std_logic_vector(msb2 downto 0);
            mr  : out std_logic_vector(msb2*2+1 downto 0)
    );

end Full_vector_multiplier;

architecture Behavioral of Full_vector_multiplier is

COMPONENT full_vector_adder
    generic(msb : integer:=47
    );
    PORT(
         i1     : IN  std_logic_vector(msb downto 0);
         i2     : IN  std_logic_vector(msb downto 0);
         s      : OUT  std_logic_vector(msb downto 0);
         c_out  : OUT  std_logic
        );
    END COMPONENT;

type minimatrix is array(0 to msb2) of std_logic_vector(msb2 downto 0);
type matrix is array(0 to msb2) of std_logic_vector(msb2*2+1 downto 0);
signal x        : matrix:=(others=>(others=>'0'));
signal bt       : matrix:=(others=>(others=>'0'));
signal b1       : minimatrix:=(others=>(others=>'0'));

signal s_c_out : std_logic_vector(msb2 downto 0):=(others=>'0');

begin

mr<=x(x'right);

main : for i in 0 to msb2 generate
    b1(i)(i)<=mb(i);
    bt(i)(msb2+i downto i)<=b1(i) and ma;--line-A
    it0 : if i=0 generate
        x(i)<=bt(i);
    end generate it0;
    itothers : if i>0 generate
        addi : full_vector_adder port map(
                i1=>bt(i),
                i2=>x(i-1),
                s=>x(i),
                c_out=>s_c_out(i)
                );
    end generate itothers;
end generate main;

end Behavioral;

The problem is that I am trying to save or copy the vector ma in the bt array, shited i zeros in each generation of the main loop (line-A), and it(bt) seems to be only a ones diagonal:

the b1 array is successfully filled with \$mb_i\$ in the \$b1_{ii}\$ "position":

So, the question is if what I am doing wrong? It's only "line-A" the problem?
because I need that bt be like:
|0.....ma|
|0...ma 0|
|0..ma 00|
Thanks in advance.


texts:
I have to measure voltage for about 100 different channels in one object and the problems is space for equipment (100 transducers would require lots of space) and price of transducers.
Is there a way to use some kind of relay switch/commutator to change the channels for one sensor? For example it would be great to make 10 measurements by one sensor when using additional device to change the channels (by time or by input from other device..).
All the voltages are almost the same ~220-240V AC and some ~12-24V DC.
All ideas are welcome and very much appreciated.
Here is basic scheme of the measuring devices integration:


texts: Can MOSFET drain current be higher than rated if the drain-source voltage is below rating?

texts:
Sorry, a very noobish question here. I'm trying to understand if MOSFET ratings work on the principle that current and voltage are proportional (like Watts) or whether each rating is separate and shouldn't be combined.

Take for example a 2N7000 MOSFET rated at 60V DS and 0.2A Drain Current.

If I only ever run 30V through it, can it safely pass 0.4A of current? Or is it 0.2A all day?

(application: I want to use a MOSFET in a voltage boosting circuit from 5V to 12V but need up to 6A to flow through and am wondering whether I can use these 2N7000's I have or whether I should source a beefier part).


texts: smd vs toroidal RF filter coils: best choice and for which frequency ranges in receivers

texts:
Is there a preferred choice for receiver RF filter coils between smd vs toroidal ?

If yes, for which reason and is it based on the range of frequencies they have to be used ? For example HF vs UHF ?

Edit: After you design your filter, for example a 5 poles Chebyshev passband centered on 21 MHz and 8 MHz bandwidth, and you get the values of the capacitors and coils, how should you select bewteen SMD and toroidal coils ?

Could you have better behavior from one or the other coil type ?

I'm asking because I had bad performance by an FM bandstop built with SMDs while the same design and coils values performed really better using toroids. The second was actually silencing almost every station while the first showed poor attenuation.


texts: Short circuit protection of a controller for flyback converter

texts:
I would like to have your opinions about this short circuit protection. Here is the schematic associated given into the datasheet.

And you can find into the same datasheet how their short circuit protection works.

Here are my questions:

1 - " When the output of a flyback power supply is shorted, the primary VDD decreases due to the coupling polarity between the aux winding and the secondary winding of a
transformer"

It means that the current flowing through the secondary windings which is high produces a flux (according to the Ampere's theorem) which can cross the inductance of the auxilliary winding and then have an influence on the auxilliary voltage? Theoritically, the mutual inductance between the secondary winding and the auxilliary inductance should be null? I.e. coupling factor = 0? So the datasheet assumes that the transformer is not well designed.

2:nd question:
"However, it is possible that the VDD voltage remains higher than the UVLO level even if the output is shorted. This happens when the coupling between the aux and the primary winding is too good." Is it asking to reduce the mutual inductance between primary and auxilliary, ie to increase the leakage inductance on the primary side? What it really asking is to have a lower coupling between the primary and the aux and a better coupling between the output and the aux. Imagine I follow the instructions, as the current sink by the auxilliary winding is low, even if the coupling factor is poor, the flux which will not be tranfered to the auxilliary side and so will remain to the primary would not be able to produce a high leakage inductance? As Lleakage = remaining_flux/I_primary (I’m not sure of this last definition)


texts: Can I supply more current at lower voltage safely through a variac?

texts:
Here is my setup:

I have a 120V 20A welder that I am fairly certain uses a transformer to drop the voltage which increases the amperage. I have a 120V 20A variac that I want to put in series on the secondary side of that transformer.

Is it safe to push more current through the variac because it's at lower voltage? I believe it should be safe as long as the wattage is the same. The variac is rated for 2000VA (which is the same as Watts).

I know the other way around, higher voltage at lower amperage is NOT necessarily safe. I know components are rated in both WATTS and VOLTAGE, because if you push the volts too high, eventually the resistance of the air between the wires will be lower than the resistance of the circuit and it will arc (short-circuit).

So is higher current at lower voltage safe if the watts are the same?


texts: Effect of electrical arcing on the system voltage

texts: What will be the effect of Electrical arcing (between phases or between phase and neutral) in a 415V three phase system in the downstream voltage... Will it just act as a load ( let's say the arcing was highly resistive and did not trip the system and continued ) or will it cause any increase in system voltage ..? If it causes a rise in system voltage how


texts: Circuit to enable switching between antennas

texts:
I'm trying to build my own portable Wi-Fi router that can switch between small internal PCB based antennas (like this from Aliexpress) and an external directional antenna.

Is there  circuit that I can make that can work as a switch between these two different analogue signal inputs? Something that switches automatically based on whether an external antenna's connected would be ideal but not necessary. Is a signal multiplexer (and demultiplexer) at least part of what I need?

Thanks!


texts:
I´m trying to repair my lock control in my car. And this board seems like the problem, so I want create a new board (exactly the same) based on this. But I facing a challenge:

I cant determine what component are this tree elements that seem like transistors:

1) and 3) The first one and the thrird has a label in the PCB that say: Q1 (like a transistor). In the package device the label say: CIP

2) The second device has a label that say: D3, like a diode (but have 3 terminals). In the package device the label say: A4M

The image of the circuit:

Of course I need to find the correct element reference to put this on my new board.

If someone hear can tell me the reference of this three components, I´ll be grateful.

Thanks in advance


texts: How would I find buttons and switches like would be found on old TVs and radios?

texts:
I am working on a project that is attempting to emulate an old TV and radio. We need a rotary switch that has a very solid detent feel like those old TVs. We also would like to find a set of toggle buttons like you might have found in a car stereo in the 70s/80s. DigiKey has a pretty vast selection of rotary switches, but I'm not sure how to filter it down by feel other than ordering a bunch to test. I have no idea how to even search for the toggle-style buttons.

Any suggestions for how to find sets of switches/buttons that have the most appropriate feel?

P.S. We need to use components that are relatively easy to source as they will see a high amount of usage and will likely need to be replaced several times as they wear out, so scavenging from old equipment is not a very practical solution for us.


texts:
I'm building a Hifi amplifier and I wanted to design a circuit which switches off the power of the amp boards if no music is played for like half a minute. I built it on a demo board but it looks like I made a mistake somewhere, the current is not enough to pull the relay.

Is my design correct at all? The theory is that music (the source is a phone or a laptop output) is fed into the opamp, the R1 (500 ohm)-R2 (10k) amplifies it and the positive half of the signal (which goes through D6) charges the C2 capacitor. If C2 is sufficiently charged, Q4 starts to conduct and closes the relay on J5-J6. Without music, the capacitor discharges, Q4 no longer conducts, the relay opens. Problem is, the voltage on the relay is very low and doesn't pull. I also tried using a mosfet (BS170) for Q4, same thing happens. Is my design flawed or should I search for hardware problems?


texts:
I was running a simulation with: http://www.falstad.com/circuit, this is my circuit: http://pastebin.com/QKZ6gevy.
When I add a capacity, the voltage is not going beyond 50-60V at the end of the flyback transformer. Without it is at ~4 kV.
I thought, the capacity has to adapt to the output voltage the circuit and I thought the equilibrium is 4 kV then.


texts:
I have PWM signal from a computer motherboard to control 2 fans, one of them is rated for 3000 RPM, and the other one is rated for 2000 RPM.

I'm trying to run all of them at the same speed(for example 1500 RPM) but I can only send one PWM signal, if I send PWM signal with 50% duty cycle one fan will run at 1500 RPM and the other will run at 1000 RPM.

So I was wondering if it is possible to take a PWM signal and modify it(Increasing duty cycle) and then feed it to one fan so that they run at the same speed.

Thanks in advance.


texts:
Is it true that a burden lower than the CT rated burden will results in CT measurement inaccuracy that would exceed the CT accuracy class limit.
So, a CT percentage error matches the nameplate CT percentage error ONLY when the actual burden is equal to the CT rated burden.
The total burden on the CT is that of the relays, meters, connecting leads and the burden due to the resistance of the secondary winding of the CT.
In other words, if a CT rated burden is .2 Ω, but, the actual burden was 0.3 Ω OR if the actual burden 0.1 Ω, there will be higher error in its measurement even when the CT is operating at its rated current.
Is this true or not?


texts: ASIC timing constraints via SDC: How to correctly specify a multiplexed clock?

texts:
Introduction

Having found multiple, sometimes conflicting or incomplete information on the internet and in some training classes about how to create timing constraints in SDC format correctly, I'd like to ask the EE community for help with some general clock generating structures I have encountered.

I know that there are differences on how one would implement a certain functionality on an ASIC or FPGA (I have worked with both), but I think there should be a general, correct way to constrain the timing of a given structure, independent of the underlying technology - please let me know if I'm wrong on that.

There are also some differences between different tools for implementation and timing analysis of different vendors (despite Synopsys offering a SDC parser source code), but I hope that they are mainly a syntax issue which can be looked up in the documentation.

Question

This is about the following clock multiplexer structure, which is part of the clkgen module which is again part of a larger design:

While the ext_clk input is assumed to be generated externally to the design (entering through an input pin), the clk0 and clk4 signals are also generated and used by the clkgen module (see my related ripple clock question for details) and have associated clock constraints named baseclk and div4clk, respectively.

The question is how to specify the constraints such that the timing analyser

Treats cpu_clk as a multiplexed clock which can be either one of the source clocks (fast_clk or slow_clk or ext_clk), taking the delays through the different AND and OR gates into account
While at the same time not cutting the paths between the source clocks which are used elsewhere in the design.

While the simplest case of an on-chip clock multiplexer seems to require just the set_clock_groups SDC statement:

set_clock_groups -logically_exclusive -group {baseclk} -group {div4clk} -group {ext_clk}

...in the given structure, this is complicated by the fact that clk0 (via the fast_clk output) and clk4 (via slow_clk) are still used in the design, even if cpu_clk is configured to be ext_clk when only use_ext is asserted.

As described here, the set_clock_groups command as above would cause the following:

  This command is equivalent to calling set_false_path from each clock
  in every group to each clock in every other group and vice versa

...which would be incorrect, since the other clocks are still used elsewhere.

Additional Information

The use_clk0, use_clk4 and use_ext inputs are generated in such a way that only one of them is high at any given time. While this could be used to stop all clocks if all use_* inputs are low, the focus of this question is on the clock multiplexing property of this structure.

The X2 instance (a simple buffer) in the schematic is just a place-holder to highlight the issue of automatic place&route tools being usually free to place buffers anywhere (such as between the and_cpu_1/z and or_cpu1/in2 pins). Ideally, the timing constraints should be unaffected by that.


texts:
I want to build a battery operated low noise audio VCO.

With current knowledge I could use discrete transistors, op-apms, 555, HC4046 ,  or a simple NAND-circuit. Which option would produce least amount of noise?

Update:

The application is a synth. The waveform generator should be discrete electronics. (not MCU-generated).

With noise I mean noise as in white/pink which all semiconductors / resistors produce. (diode noise generator for example). Harmonic overtones are not a problem.


texts:
Suppose we have a type-I PLL whose block diagram is shown below:

Here \$k_{pd}\$ is the average gain of the phase detector producing the control voltage \$V_c\$ which is input to the Voltage Controlled oscillator (VCO). In the feedback path we have a frequency divider which divides its input frequency by N.
Suppose input frequency is given by \$\omega_{ref}  (=2\pi*f_{ref})\$ and output frequency is \$\omega_{out}\$, then in general the phase difference between the input and the fed-back frequency is given by: \$(\omega_{ref} - \omega_{out}/N)t + \Phi_{ref} - \Phi_{out}/N\$.This error signal is input to the phase detector. The steady state phase difference should be given by: \$\Phi_{ref} - \Phi_{out}\$ with \$\omega_{ref}  = \omega_{out}/N\$. Does, this frequency  relationship hold true even if \$ |\Phi_{ref} - \Phi_{out}| \ge 2\pi\$, which is beyond the range where the PLL will get locked?
In other words, does the frequency relationship between input and output   (\$\omega_{ref}  = \omega_{out}/N\$) maintained even if the PLL doesn't get locked? If not, what happens to the output signal (in steady state) if PLL is beyond the lock range (given by \$ |\Phi_{ref} - \Phi_{out}| \ge 2\pi\$)?


texts: When a current flow in an inductor is interrupted, what limits the voltage rise?

texts: When the current flowing in an inductor is interrupted the voltage will rise until (typically) there is a flashover or insulation breakdown in the switch. Assuming extremely good insulation what would limit the voltage rise in practice? I can't really believe it would head into the megavolt region.


texts: Looking for a program that can simulate a Verilog HDL file

texts:
I was wondering whether a program has been made that can simulate the end product of a Verilog HDL design file.

To give some information I am using Quartus 2 (the design file is a verilog HDL file) and compiling it, (and then I would download the design to an Altera DE2 board (Cyclone II). I am asking whether a program exists that would allow me to do this without the physical DE2 board).

For example, a Verilog HDL file that takes switches as inputs and outputs are seven-segment displays.

I hope I have used the correct terminology as I am new to coding in Verilog.

Any suggestions welcome :)


texts: Is It Okay to Run a Single-Ended 5V Pulse Train through One Strand of a Twisted Pair?

texts:
Okay, I have a motion control application that I want to wire up. The motor drives run from single-ended step and direction signals. I am designing a circuit board, and was thinking of using 8-pin RJ45 on my board, then routing the signals out to the motor drivers using Cat5 cable.

My question is: if I run the step signal through pin 1 of the Cat5 cable, and leave the other wire of that particular twisted pair unused and unconnected, are there any potential negative repercussions to that?

What if I ran the step signal through one wire of a pair and the direction signal through the other wire of the same pair? Is there any reason why that would be a bad idea?


texts: How to create a single line model (SLM), multi line model (MLM) and/or IBIS model of an interconnect for simulation?

texts:
I want to create a single line model, multi line model and/or IBIS model of an interconnect for simulation in Hyperlynx software but can't understand how to do it when the manufacturer has given no related parameters whatsoever. The interconnect is this one:

TST shrouded connector (Samtec)


texts: Which low power microcontroller for short active periods at long intervals?

texts:
Regarding this question.

In the question was asked for a solution for monitoring a voltage over a long time. The question contains hints to a microcontroller solution, and a couple of answers also covered that, but the real question didn't need a microcontroller at all.

Now if it would require a microntroller, what are the best choices for low power? Concrete: I need to measure temperature once every 5 minutes and wirelessly transmit the value and go back to sleep. Transmission is <20m, not line-of-sight. Any protocol/frequency. Just two bytes of data to send. I want the battery, a 600mAh CR2450, to last as long as possible. Interval precision better than 0.5% possible (that's 1.5" in 5 minutes)?

edit (by stevenvh)
Federico mentions a home weather station with wireless outdoor thermometer in a comment. I think that could give a good idea of the type of application. The thermometer indeed transmits its data every 5 minutes, and works for more than a year on one set of batteries.

If it makes any difference: how about sampling once every hour?


texts: Datasheet Cross Reference for Old Military Part?

texts:
I am looking for a datasheet for a part labelled 0N088586, but have been unable to find a datasheet. Does anyone know if there is a way to cross-reference the NSN with an equivalent part?

The part is an old "can" IC, and it appears to be some kind of logic circuit (see link)
98230 is printed above the 0N0 number, but I wasn't able to find anything related to it.
The numbers 94 6 48 are etched across the top.


texts: Using regulator capacitor bank for a motor

texts:
I want to use a regulator capacitor bank in a small facility that has a machine so based on the power factor it insert the capacitors.  Each 30 seconds the motor power factor is 0.4 and for 10 seconds is. 77.
Would I have a problem with the contactors(should be AC-6b) because less than a minute it switch 3 time for 24/7?

Also apparently the bank should be out of the circuit before turning off the motor,  how should we do!???


texts:
I have an NXP LPC1769 which features an ARM Cortex M3.

I understand how to program it and have had success building both C and C++ programs for it.

I have some code that I want to port from Windows. The problem is that the code relies heavily on STL features, specifically std::vector. I am aware of the potential overhead introduced by building programs with the STL.

(1) Are there any (free) toolchains that simply support using the STL?

(2) Would it be reasonable to build a small port of the STL (uSTL, for example) for the M3 and then link the port into my program?


texts: What is the actual risk when my 6-month old chews on a USB battery pack?

texts:
I'm asking... err... for a friend, a theoretical friend...

Now, before everyone piles on with "Thats a terrible idea, your child will definitely die", I'm not interested knee-jerk reactions.  I would like to know what is the actual risk - and how can it be mitigated.  For example, there is some chance that the battery will spontaneously combust, but if that chance is more remote than (for example) a baby having a heart attack (1/100000) it's not particularly relevant.

Now, the actual question...

I have created a simple wearable arduino-nano based device to potty-train my 6-month old.  For the device to be really effective it needs to be running 24/7.

The device is powered by a 10000 mhA battery pack and is strapped to his waist.  The drain is miniscule (I badly misjudged requirements there), and he can't get the live ends to his mouth anyway.  However, he has just discovered he can get the other end up, and enjoys chewing it, and babies can make a lot of saliva.

So... what are the risks here? (numbers would be great).  If the moisture makes its way inside the battery casing, could it cause any sort of chemical leakage?  If the ports get wet, could it short the battery and start a fire?  Am I being paranoid or irresponsible here?

would (for example) hot-glue-gunning the ports be a good idea?  I'd rather not - I've already replaced the cables once and the current one is looking pretty mangled already.

-- EDIT -- Battery in question is this one: https://www.amazon.ca/gp/product/B01B5RZOB6/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1


texts: Resistor in the inverting terminal of the op-amp

texts:
I was studying the gain of an op-amp in both inverting and non-inverting configuration. In case of inverting configuration, the resistor is in series with the applied AC voltage. But in case of non-inverting configuration, the resistor is not in series with the applied AC voltage. In other word, the resistor is placed on the inverting terminal for both inverting and non-inverting case. Why is the resistor used in the inverting terminal but not in non-inverting terminal?

simulate this circuit – Schematic created using CircuitLab

The circuit shown above is the copy of one shown in my textbook. The first one is in the inverting configuration with resistor in series with the AC source. The second one has resistor connected to the inverting pin and other side to the ground.

I know the signal is applied to the right pin, but why with resistor in one case and why not with resistor in another case? Thanks in advance..


texts:
Does anyone know where to get information on the 34 pin floppy disk interface? In particular, I want to be able to read and write to floppy drives from my custom embedded board.

Having a hard time finding info about it because it's so old.


texts: What is the predictable difference of the voltage drop between the V+ and V- lines on a shunt resistor?

texts:
I am making an electronic speed controller, and the half-bridge driver I am using has a built-in overcurrent protection feature. In order to utilize this feature, I have to supply the pin (a noninverting input of a comparator) with a voltage higher than 540 mV (which is the typical reference voltage supplied to the inverting input of the comparator). I plan to use this shunt with a value of 0.6 mOhm, so that when 65A (the max current I want to flow) flows across the shunt there is a voltage drop 39 mV. I know that the most accurate way to measure current with a shunt is to subtract two sense lines: V+, V-.

I plan to use the l6390's (the driver) built-in op-amp to subtract V+ and V- to get the accurate voltage drop, my issue arises when attempting to select the gain for the op-amp. It's pretty crucial that the amplified voltage is greater than 540 mV when the current reaches 65A. So I was wondering if anyone could tell me a way to estimate the difference between V+, V-. Essentially, will the voltage drop on the V- be significantly lower than the voltage drop on the V+ sense line? If that's the case, I can just do the calculations using an arbitrarily low value, but if that is not the case, I am not sure about how to do the calculations.

Thanks.


texts: I understand that when the torque is produced in the rotor, it tends to rotate the rotor in the same direction as that of rotation of field, but my concern is that when is the torque produced in the motor?


texts: Which diode to choose to prevent molex PC PSU powered HUB to be damaged or backfeed

texts:
I want to power my cheap, powered USB 2.0 7-port HUB via standard PC PSU (build molex to barrell adaptor). I want to make sure it's not backfeeding into computer. I want to be able to power the hub form computer's USB if it's not connected to the molex, so cutting the power wire in the USB cable is not an option.

I want to use a diode for that purpose. The current which molex outputs is 11A, voltage 5V or 12V (I want to use 5V rather than 12V, the HUB is 5V device). Which diode shall I choose? Is the 11A Schottky diode any good for my purpose or maybe I should rather use a different diode? I should get no more that 500mA for each port, thus use max 3.5A power supply.

In that case is connecting it to the molex which will give me a lot more current on each port a good idea at all? If I connect the HUB to the molex and want to charge my phone's battery up will it get burned by getting 11A form the power source?

How do I prevent backfeed on a circuit (like a hub) into another circuit (like a computer)?


texts: Wireless Communication between microcontroller and PC

texts:
I have a FRDM K64f board that is using the nRF24L01+ as it's wireless transceiver.

I want to communicate between the K64f board and my PC locally.

I am struggling to find the hardware needed on my PC's side.

I had thought of using a USB to TTL adapter and connect a nRF24L01+ on the PC side and communicate this way.

Would this be viable?

Or is there a simpler way?


texts: I am trying to understand the v curve of synchronous machine. Particularly, the point that changing field current can put the machine in leading or lagging mode. I am trying to get an explanation to this, but couldn't find one. Can anyone explain, why over and under excitation of field puts the machine to work in leading and lagging pf respectively. Thanks.


texts: N-channel mosfet (FQP30N06L) will not turn off

texts:
What's wrong with this circuit? The mosfet will turn on just fine with 5v or the gpio 3.3v but i cannot get it to turn off. It will only turn off if I use another external power supply for the Raspberry Pi and connect the GNDs. But with this circuit it just won't turn off. Why is that?

note: there's a 2n3906 pnp transistor between gpio pin and Drain.


texts:
I am trying to use an 12V OEM type power supply to supply 12V to stepper motors through an L293 h bridge in an Arduino powered circuit but my current setup starts burning all the negative wires and almost killed my pc when I plugged the Arduino in the USB port. I am not sure what could be causing this. I have connected my Live, Neutral and Ground wires correctly and I am then using the "adj. +V" pins as my motor voltage supply and I have connected the "-V" to the common rail/ground of my circuit. The power supply does seem to work fine and if I put an LED with a resistor between "adj. +V" and "-V" nothing strange happens and the LED goes on just as normal. I should also mentioned that the circuit where the ground wires fried has been used hundreds of times with a PC power supply and gave no trouble at all.

I am guessing that the OEM setup is probably the problem here. I have found this page http://reprap.org/wiki/RepRapPro_Mendel_power_supply indicating that I should connect the ground on mains to the -V as to earth my circuit. This could possibly explain my trouble as it means that once I plug in the Arduino in it seeks earth through my PC, or is that just absurd? Even if that is the case, following the above tutorial I have come across an issue, in the testing segment they state that there should be no resistance between ground and -V and this is indeed the case once I have done as stated in the beginning of the tutorial and connected ground and -V. The troubling thing is though that there is also almost no resistance between +V and the ground pin, even without me making the aforementioned connection. I know they don't state this as something to test or watch out for but my head tells me this means that +V and -V are then connected and making a short and that that is something very dangerous, I am therefore to afraid to test the power supply after connecting ground and -V.

Do any of you have experience with these power supplies and know if this is normal or have had the issue before and might know of a possible solution?

Here is photo of the terminals without a connection between GND and -V:

EDIT:
I have now removed all the wires and there is still a connection between +V and earth.

EDIT:
The circuit basically entails that firstly all the ground pins meaning the ground on the Arduino and the -V on the power supply and the ground pins of the h bridge are all connected on a common rail. The VCC on the h bridges are then connected to the 5V on the Arduino and the +V on the PSU is only connected to the motor voltage pin on the h bridge. But as I previously said, this circuit works fine with a pc power supply. Also, for some reason only the black wires connecting the ground pins were burned, the 12V and 5V wires are all fine.


texts: So I just started learning about PIC microcontrollers starting with the 8-bit PIC16F84A. I have written a simple code that blinks an LED and I wanted to ask something. Here is a segment of the code that turns on the LED and waits. What I wanted to ask is that in the loop it counts to 255, 255 times. If one instruction takes 1uS to execute then the whole loop takes a time of 255*255*(1E-06)=65ms. But when I simulate the same program in Proteus, it shows that the LED stays on for 198ms and not 65ms. What could I be doing wrong?


texts: Synchronization in digital communication

texts:
I am an undergraduate student and studying digital communication systems.
I am not able to find any good resource where I can self-study about synchronization and it's types (time, frequency and phase synchronization). Can someone explain what exactly synchronization is and why we need it in digital communication systems?
Note: I searched a lot about this in many books and sites but I was not able to clear my concept, all I found are research papers etc.


texts: Sanitizing of electronic items during COVID

texts:
I am considering to purchase a new desktop PC ( components, will assemble myself ). I am worried about the inability to use everyday sanitizers to clean, for example, a motherboard.
Is there any guidance on how to sanitize and decontaminate an electronic item, like a motherboard, CPU, GPU, PSU, RAM, HDD? What can I do to eliminate the risk of microbes on the surface? Any solvents? Just let it dry in the sun? Can I clean it with an antiseptic liquid (water solution) and let it dry off? Or just delay the purchase until everything improves?
Any help will be appreciated!
Thanks!!