texts:
Sometimes I'll look at registers in asm or when debugging a C output. What exactly is a register? In my understanding, it seems like it would consist of, for example 16 D-type flip-flops connected to the same clock signal (for a 16 bit reigster). But then other times it will be referred to as something like an "8 bit latch" and not a series of flip flops.

What then would be an example of a register? And is it any different than some flip-flops of a predetermined width connected to the same clock signal?


texts: HC-05 Bluetooth module not recognized by mobile phone

texts:
What is happening with the bluetooth module is a bit weird. It apparently works perfectly, it gets recognized by my desktop computer and my laptop, but never gets listed on my mobile phone.

I've configured it in many ways, and it's always the same: it gets listed everywhere, but not in the mobile phone.

I know for sure that the mobile phone works, because I can connect it with other computers, and other devices get listed there too.

My configuration steps are:

AT
AT+ORGL
AT+RESET
AT+NAME=TEST
AT+ROLE=0
AT+POLAR=1,0
AT+RESET
AT+INIT
AT+INQ

I set the original from fabric just in case, and reset the device. Then configure it to set the name, slave role, invert the status pin so it goes low when is paired, and reset again to start with the new config.

Then I init the module and start inquiring.

What could be happening? Am I missing something?


texts: What is a suggested portable power source for 100w Arduino project?

texts:
I purchased one of these LED strips. The 16.4 ft, 60 LEDs per meter one.

They are connected to my Arduino Uno. I’ve been powering my Arduino through my laptop, but would now like to make it portable.

The description says 18W per meter. So that seems roughly to be 18W * 5meter = 90W.

What kind of batteries / setup can I use to portably power this?


texts: Get motor ratings from unknown DC motors

texts:
I've purchased bulk cheap DC motors for a robot problem. But I don't know their ratings.

Is there a way for me to find out?

For instance, I would like to know their max DC voltage input using basic tool like a multimeter.


texts:
What is the purpose of faraday shields in a transformer?
What is the interest of insering a Faraday shield between the primary winding and the secondary winding in a halve of transformer windings ?
Is it for reducing leakage inductance ?

Compare this picture (where we only see half of the total transformer winding) from "Eddy Current Losses in Transformer Windings and Circuit Wiring" by Lloyd H. Dixon, Jr:


texts: Two stage Amplifier CC-CE with high voltage gain

texts:
I want to design a two stage amplifier with the following parameters: Av = 300, Zi = 1M, VCC = +12V. I have tried deriving the parameters to use but have not been successful as my lecturer always said I'm wrong. He said it has to be CC-CE which I'm a little bit confused.
I would be grateful if someone could help me in any way you can. Thank you.


texts:
I have simulated an damped sine wave generator in ltspice. Since I couldn't find a model for single pole double throw relay, I used two switch. It is very basic circuit first charges capacitor and with simultaneous switching oscilates with inductor.
For frequencies up to 10Mhz it works well. But for 100Mhz wave shape got distorted.
As it seen in the picture First cycle is smaller than the second one. This is in LTspice. In real life it is much more weird: For first 3 consecutive cycle voltage goes up. After 4th or 5th cycle it oscilates as normal damped sine wave as I would expect it to be.
When I double the value of inductor and half the value of capacitor signal gets better. But this time Q(it should be at least 10) factor decreases.
My purpose is to have a normal 100MHz damped sine wave. Not like in the picture(in the picture it goes up and then down).
How to deal with this problem?.


texts: Why can the total connected load be equal to system capacity ? what does "maximum demand of the entire system" really mean?

texts:
I read some factor in the power transmission ,and there are something i don't really understand

Question 1

demand factor \$ = \frac{maximum \ demand}{total  \ connected \  load }=\frac{maximum \ demand}{system \ capacity }\$,why can the total  connected   load \$\$= system capacity?

Because i think the total load means how much power does my total load consume,and system capacity means how much maximum power can the system provide to the load ,they should be different,why can them be equal?

Question 2

Diversity factor  \$ = \frac{sum \   individual  \  maximum  \  demands}{ maximum  \  demand  \ of   \ the   \ entire   \ system}\$,

I want to ask what does the " maximum  demand   of   the   entire   system" really mean?

Does it mean that The maximum demand of entire system can provide to the user? if yes,we all know that the diversity factor is always \$\ge 1\$, so it means that the "sum individual maximum demands" is always greater or equal than "maximum demand of the entire system".and we will increase the diversity factor to reduce the cost of generation of power.

i think it doesn't make sense ,because that means ,take this for example,three children need 5 dollars for each,but i only have 10 dollars,obviously,i don't have enough money to give every kid 5 dollars,but if we increase the diversity factor,which means i should have the littler money in the begining (\$< 10\$ dollars), or i should give every kid more than 5 dollars so why  will we say it is better to  increase the diversity factor?

Or does it mean that the maximum demand that entire system needed? but why does the system needed? i think the system  should provide something to the user,not the user provide something to  the system.

So what does the " maximum  demand   of   the   entire   system" really mean?


texts:
the title actually quite sums up my question, How to extends Arduino Mega to 250 I/O pin ? I will use it to drive 250 12 V relays (if a direct ic/chip that are 12V capable (max 50 mA per pin will be used) solution is available i would prefer it.

Currently, im thinking on using a daisy chain of a high power shift register(im still not sure of? need recommendation on it too(12V,max 50 mA),the next problem is will it be fine to daisy chain all of those from one data pin? is there any other solution?

Thx!

+UPDATE:
ater some times i found this ic http://www.ti.com/lit/ds/symlink/tpic6a596.pdf will it works? Daisy Chained to 30 of them?


texts: Charging a supercapacitor with a zener diode

texts:
I have a dc source which gives 5.5V and I want to know how to give only 2.7V to the supercapacitor for charging.
I'm thinking about this circuit :
What are the limitations of the circuit?                                                How can I improve the circuit ?

Will it work ?

Thanks for your help.


texts: Cannot get Active-HDL to run in Lattice Diamond

texts:
I have the latest version of Lattice Diamond installed and a freshly generated Free license. However, when I try to run a simulation, I get an a window that says "FLEXlm not initialized.".

After about two hours of mucking around on the next, I have not yet found a solution. Can anyone help?


texts: 24v Power supplies - input and output power

texts:
I have been reading your articles on power supply in readiness for starting to build a home automation system using Loxone equipment.

I feel confident in the project but the power supply situation leaves me a bit perplexed.

I am intending to use 8 TDK Lambda (DRF240-24-1) power packs to drive the 24V DC LED lighting in my new house.

Each power pack has a rated input of 100 – 240 VAC 2.7A.
The output is 24 – 28 V DC 10 – 8.6A.

So that is a power requirement of 648W for an output of 240W.

My first question is where is the missing 408W?  I realise that the pack itself will require some energy to work, but I would have thought that would be around 20% of the input.

Secondly; if the input is rated at 2.7A x 8 power packs then I will need an RCB in the consumer unit rated at over 21.6A, - or more likely several lower rated RCBs to split the load into zones.

Am I missing something here?

From the 8 Power packs there is a total power available at 24V DC x 80 A  =  almost 2,000W whereas to provide this I have to supply 21.6A x 240VAC = over 5,000W.  Am I going wrong somewhere?

Any observations would be appreciated especially if I am completely failing to understand this issue.

Thanks in anticipation.


texts: Do you need a wiper blade for a crystal radio?

texts:
If you don't use a wiper blade, can you still adjust the received frequency if you have a variable capacitor?
Thanks


texts: What is standard coding practice for a non-blocking assignment to a large register array with variable part select in Verilog?

texts:
I couldn't find anything in the Verilog-2001 standard about this. For example,  the following code works (Xilinx ISE):
reg r1;
always @(posedge clk or posedge rst) begin
    if (rst) begin
        r1 <= 0;
    end else begin
        r1 <= r1;
        if (cond1) begin
            r1 <= 1'b1;
        end
    end
end

In this case, r1 is updated to 1'b1 when cond1 is nonzero (@ posedge of clk), otherwise it retains its value (as intended). Similarly:
1 reg [1023:0] a_reg;
2 always @(posedge trigger or posedge rst) begin
3     if (rst) begin
4         a_reg <= 0;
5     end else begin
6         a_reg <= a_reg; // required?
7         a_reg[i*2 +: 2] <= input;
8     end
9 end

Is line 6 required? What is considered acceptable practice for FPGA and ASIC design? I would imagine line 6 is not required (as per the definition of a register, it should hold its value between assignments). Or does it depend on the compiler / synthesis tool (DC Compiler, Xilinx ISE/Vivado, Altera Quartus, etc)? Is there something in the standard that sheds light on this?


texts: AC leaks to laptop, cellphone surface. Feel by finger!

texts:
I've accidentaly discovered that several mains+battery-powered devices with metallic casing like cellphones, laptops and mp3 players, exhibit a special kind of friction when stroked with a finger. But only as long as the device is connected to mains for recharging! Once running from battery power only, it's smooth again! It's like stroking glass with a wet finger (stick-slip-stick-slip), but more subtle (and doesn't make the noise).

The stick-slip rate appears to be always the same, no matter how light or firm touch you make (unlike with glass&wet finger). I guess it is 50 Hz - AC!

Looks like some charge leaks to the surface of the devices from the power adapter despite proper isolation. Friction ceofficient might be sensitive to the alternating surface charge, hence the stick-slip...

Question: Is this a known effect? Does it have a name? Any details?

More info:

The devices were not faulty. They include Macbook Air and a Cowon mp3 player, among others. I encounter this effect everywhere I go
You might need to try different parts of your hand to get the stick-slip. Finger pads don't always work for me, finger joints work best. I guess it has to do with sweat.
If I remember correctly, if I ground myself with my other hand, the effect is gone.


texts: Why PINxn with pullup reads zero when nothing is connected to it?

texts:
Consider the following C-program:

#include <avr/io.h>
int main(void)
{
  DDRB |= 1 << PB0; /* LED */
  PORTB |= 1 << PB5; /* pullup */
  if (!(PINB & 1 << PB5))
    PORTB |= 1 << PB0; /* turn on LED */
  while (1) ;
}

There are two situations:

connect a 10cm wire to PB5 pin (the other end of the wire is in the air): the result is that sometimes after poweron the led is on, sometimes the led is not on.
do not connect anything to PB5 pin: the result is that after poweron led is never on.

In datasheet in section 10.2.4 "Reading the Pin Value" nothing applies to this case.

The question is: what causes PINB & 1 << PB5 to read zero value, in spite of the fact that it is pulled up; and how to solve this issue?

If I add a 10ms delay after pulling up, led is never on after poweron. Why? Where is it described?

#include <avr/io.h>
#define F_CPU 16000000UL
#include <util/delay.h>
int main(void)
{
  DDRB |= 1 << PB0; /* LED */
  PORTB |= 1 << PB5; /* pullup */
  _delay_ms(10);
  if (!(PINB & 1 << PB5))
    PORTB |= 1 << PB0; /* turn on LED */
  while (1) ;
}

But this delay is just to show that there is something wrong - I do not want to use the delay to solve this issue - I want to know the cause (and the proper fix).

(Note: in my project this wire hanging in the air is one end of a button switch, and micro controller sometimes detects that a button was pressed (while it was not), which is a big problem.)

EDIT

The "synchronizer" does not help. In the following example some instructions are executed after enabling pullup. But the behavior is the same as originally described.

#include <avr/io.h>
int main(void)
{
  PORTB |= 1 << PB5; /* pullup */
  DDRB |= 1 << PB0; /* LED */
  if (!(PINB & 1 << PB5))
    PORTB |= 1 << PB0; /* turn on LED */
  while (1) ;
}

EDIT2 See also this answer.


texts:
Guess I should know the answer, but I can't come up with a good explanation.

I always have to remember which sign cos and sin have after integration/differentiation. I usually do this by thinking of a diagram like the one in this post.

Today I thought I should memorize this, since it's so useful. You just need to draw the two axis with +- sin cos. The only thing to memorize would then be which direction is integration and which direction is differentiation.

But this is the part which I just realized is counter intuitive. From control theory one would expect to be an integrator a rotation of -90° (Phase shift of an integrator).

What's wrong? Why can't I use this to memorize this?

EDIT 1:

I might ask in another way. A integrator is a "1/s block" in control theory and a differentiator a "s block". "s" corresponds to jw. Multiplication by jw is a 90° rotation counter clock wise.
Why is the rotation direction in the diagram on the other post not the same?

At least the end up in the same result. A phase shift of -90° is a shift to the right. This makes a sin a -cos.


texts: Why is voltage across LED filament bulb slowly decreasing?

texts:
I'm trying to power this LED filament bulb with a 12V - 2A DC wall adapter.

LED specs:

rated at 4W
12 to 24V input

I'm pretty new to this, but if I get it right:

Calculus

the LED bulb will draw E/V = 4/12 = 0.33A if power source is at 12V.
by measuring voltage drop across LED bulb, I get a reading of 3V.
to control current flowing in my circuit, I'm using 1W-rated resistors. I know voltage across resistors will be 12-3 = 9V.
So I can deduct that resistors should generate a total resistance of V/I = 9/0.33 = 27 ohms.
to do this, I wired 3 groups of resistors in parallel, each group being made of 4 20-ohm resistors in series. That way, I should get a 80-ohm resistance per group, and 80/3 = 26.6 ohms of total resistance. And this setup allows me to have I/V = 0.33/3 * 9/4 = 0.25W crossing each resistor, largely below their 1W rating.

Results

When I power this circuit, the LED turns on and current crossing it is measured at 0.32V, but after a few seconds:
- the voltage keeps dropping across LED
- voltage increases across resistors
- current increases across resistors
- resistors get warm
- LED slowly dims down

I assume that the generated heat from the resistors decreases their resistance, hence an increase in current and voltage crossing the resistors, leaving less and less current to LED. But I'm not sure, and if I'm right, I have no idea how to prevent that. I tried different resistor combinations, always trying to stay way below the resistors' 1W max rating, but it always ended up with voltage slowly decreasing through LED.

Any idea on how to fix that? Thanks in advance!


texts: How to guarantee "grid-looping clock" is running when dynamically driving VFD tubes

texts:
I'm driving old Soviet VFD tubes using Atmel AVR8 processors (e.g. ATmega328 and ATmega1284) and VFD driver chips Microchip HV518/HV5812/HV6810. Some of these tubes can only be driven dynamically, i.e. looping over the grids (e.g. IV-27M). However, the voltage for dynamically driving these tubes are typically twice as high as the voltages for driving them statically, e.g. 25V and 50V.

So I'm trying to solve the problem of these tubes being ruined by 50V when the processor for whatever reason stops running and there is 50V statically on the segments that are lightened at that moment (depending on the bit string currently in the VFD driver chip).

There are two "solutions" to improve the situation that come to mind:

use a "non-maskable interrupt" to make sure the grid loop keeps running, but I don't think such a thing exists on AVR8, as there is no interrupt hierarchy and all interrupt service routines themselves run uninterrupted (except when their ISR_NOBLOCK flag is set)
make sure that the high-voltage output lines of the VFD driver chip are disabled when the MCU power is gone by using an AND port on the driver chips' enable input

But what I really need to make sure (I think) is something that verifies that all the high-voltage output lines of the VFD driver chip to the grids are flashing rather than being stuck at 1.

(although I'm using old-school tubes and driver chips, I assume this issue is the same for all dynamically-driven VFD tubes/drivers, so I didn't include these specifics in the title)

Thanks! So here is what I'll do:

as suggested use the internal watchdog in Interrupt and System Reset mode: I'll use the ISR to write out a string of 0's to the driver chips, and after latching them to the output lines, I'll activate the DISABLE line of the driver chips; then I'll go into RESET; after such a RESET, the system will come up in maintenance mode
from the HV518 datasheet (i.e. the 'Input and Output Equivalent Circuits' section) I understand that data out = 0 when the 5V power (Vdd) is lost, which means the high-voltage output will be blocked when Vdd is lost and Vpp is still there; so an external (voltage) watchdog won't be necessary here
I'll use some additional logic to connect the RESET line to the DISABLE line of the VFD driver
I could add an external watchdog that simply checks whether there is still a bitstream coming from the MCU; since the grid loop always addresses one of the grids, there will always be 1's in there even when all segments are off; are there watchdog chips that trigger on "logic silence" rather than voltages? or would this require adding and programming a tiny MCU?


texts: How to find connectors for Densitron TFT displays

texts:
I'm having a hard time to find information about the connectors for a TFT display I just bought from Densitron. The cable is physically similar to FFC/FPC, but the terminals are not straight, so I can't use normal FFC/FPC connectors.

The measures are in mm, and this particular connector has 39 pos. Does anyone knows if there's a specific name I should search for at Digikey/Avnet/etc.?


texts:
This is probably an easy question for many of you. I am newbie, so just asking this question.

I am creating a workbench power supply for my projects. I have not created the circuit myself. Instead used a ready-to-use 1.3v-32v 10 Amp DC-DC Buck Converter module. My transformer is 12-0-12 4 Amp rated. So, my buck converter always finds enough opportunity to remain cool :)

Unfortunately the buck converter module has 2 POTs to control the output voltage. But there is no built in Current Limiter. However I want to limit the max output current of the device.

I am trying to use the following circuit to achieve this.

simulate this circuit – Schematic created using CircuitLab

My questions are:
1. Will this circuit work?
2. Is the position of transistor based Current Controller unit correct? Or should it be placed between Bridge Rectifier and the Buck Converter module?
3. Is 1 Watt POT safe to use at transistor base to control current (max allowed upto 4Amp).


texts: The equivalent inductance of a RLC in parallel

texts:
When studying a system that has the same behavior of an RLC parallel circuit, the slope of the impedance before the resonance corresponds to the value of the equivalent inductance, the slope after the resonance to the value of the equivalent capacitance and the value of the impedance at the resonance frequency to that of the resistance (phase = 0).
My question is, let's say we study an RLC circuit in real life -instead of modeling the studied system with RLC parallel circuit with constant values-, the parameters R, L and C are frequency dependent (R(f), L(f) and C(f)), then to what value of inductance (what frequency) exactly does the slope before the resonance correspond to (same for the slope after the resonance aka the capacitance)?
Thanks in advance


texts: I wonder if the STM32F4 CubeMX peripheral HAL libraries saves the internal state of the peripherals OR if they are stateless? I am concerned about this because I want to know the possibility and safety of mixing the use of HAL libraries with direct register accesses at places where time-saving is more critical.


texts: How to build a transmitter using a VCO module

texts:
this question is the consequence of my previous questions, since I am learning how RF transmitters works. In past I have also built some oscillators (using little transistors and a bunch of components), but now I wish to use a VCO module.

Please also consider that obviously I follow and respect the jurisdiction about the power of these transmitters, firstly because I don't wanna infringe the laws (where I live, in Italy, we can however quietly use low-power transmitters) and last but not least, because I don't need to transmit high power. I also bought a spectrum analyzer and I have fun to learn and see that the circuits that I build are able to give me a signal that I can practically see with this new instrument.

Well, I am interested to build an RF transmitter using a VCO module (this one): for now, for me will be enough and satisfying just to measure and check the output using the spectrum analyzer: I don't want modulate any kind of input signal (eg audio or voice). Looking at the datasheet I can see the pinout: 3,4,5,6,7 to  ground, 1 is for VCC, 8 for V-TUNE and 2 is the output.

My plans, for now, are to buy this VCO module and solder it on a common matrix board: then, using some wires, make the connections (grounds, VCC, V-TUNE and another piece of wire as antenna): in this simple way I can expect to see something on my spectrum analyzer? Or I will need some external components? (eg a capacitor to filter the power supply - However I plan to use a battery). And what about the power/distance? The POS-150 claims a power output of about 9 - 9.5dBm. I will also need a particular antenna or a simple piece of wire will be enough? Eg I know that the length of the antenna is related to the frequency that I aim to transmit, and if I go higher with the frequency, there will be the need for short connections on the board, right? And I will also see some harmonics?

Consider that I am a novice and I wish to learn; so would be fine give me a detailed answer for every point (If will be enough make simple connections with wire on the matrix board, using or not extra components, which kind/length of the antenna, which distance of transmitting I can expect and if I will see some harmonics) and obviously any explanation/consideration/advice/tricks.

Many thanks.


texts: Limiting starting current of a small DC motor

texts:
I have 4 12 V DC motors and I am using 11.2 V 2200 mAh LiPo batteries to drive them. They are part of an RF robot which depend on differential drive for turning hence I don't want to compromise on torque.

Actually the problem is my LiPo pack has no current limiter, so when shorted it delivers huge current. Hence, while starting my motor sparks occur at the connecting terminals. Moreover, if the circuit is switched on-off within a short duration, the circuits gets really hot.

Can anyone please suggest a way to control the starting current electronically. Presently my motors are relay controlled.


texts:
This is very quick question.

What is this silver type thing connected with PCB?


texts: BC337 transistor appears to be in active mode, but has too small Vbe

texts:
I've stumbled onto something that I don't understand.

I've wired up a phase shift oscillator using a BC337 transistor (datasheet here). According to the datasheet, \$V_{BE(on)}=1.2\ V\$
However, using my multimeter (and after doing the theoretical calculations), I have found that my \$V_{BE}\$ is about 0.6V, which should apparently force the transistor into cutoff.

Here is my circuit:

simulate this circuit – Schematic created using CircuitLab

The oscillator is functioning, producing a slightly distorted sine wave of about 1.5 V peak-to-peak and at about 560 Hz. I measured \$I_E\$ to be around 7 mA, but couldn't measure \$I_B\$ without my multimeter ruining the output of the circuit.

As far as I know, this output should indicate that the transistor is in active mode, but if \$V_{BE}\$ is that small, shouldn't it be in cutoff?


texts: Non ideal behavior from single-supply rrio op amps

texts:
I'm starting to work with single-supply op-amps for low voltage applications, and have the following, non-inverting setup:

The circuit behaves well with both op amps so long as the predicted output voltage is below ~2.5 V:

I settled on these two op amps because they are affordable, work with V < 5 V, are single supply and, at least in the case of the MCP601, are rail-to-rail.  It's clear, however, that there is something funky going on as we approach the positive rail.  If I switch R1 and R2 in my circuit, the op-amps behave as predicted, although I don't think this is surprising since the maximum predicted voltage under these conditions is 1.86 V.

I'm still not certain if my application requires a full 3 V range (my intention is to replace the variable resistor with a photoresistor) but I am curious if (a) is it obvious that this circuit should not behave ideally close to the positive rail and (b) what, if anything, in the datasheet warns me of this behavior?


texts: Can I make a circuit that work on either 220VAC or 12VDC from the same input?

texts:
I want to make a sort of protection circuit that if someone plugged a 12V DC lamp into 220VAC it will still work.
Is this possible?


texts: How does this circuit protect against reverse polarity?

texts:
I'm looking at the datasheet for the VND7004AY high side automotive switch. The diagram below shows the internal structure of the device and claims it is protected against reverse polarity.

I have 2 questions:

How exactly does this circuit protect against reverse polarity?
The protection resistors in series with MCU I/O pins - I understand that they will prevent latch up in the event that a pin is pulled a diode drop above VCC or below ground. In this scenario, why are they needed?


texts:
I am new to electronics and i want to get about what do the symbols encircled in red signify?
Can anyone tell me what is happening in the diagram. Please help me.
Regards

.png


texts: Is there a good physical model for what happens when a light bulb suddenly goes out?

texts: Sometimes a light bulb just stops working and goes dark for seemingly no reason. Can  Dirac δ impulse to a light bulb serve as a mathematical model for what happens so we can assume that the electric current for the light bulb or the component itself had a sudden spike that caused the light bulb to go dark? Is there some other good explanation or should we assume that the component fails randomly in time according to a Poisson distribution if we want to model electronic circuitry's reason for failing?


texts: Right way to handle input in critical applications?

texts:
could someone please explain what would be propper way to handle user button on critical system like operator remote controller. Are there any documents related to safety when buttons are concern.

In our case we have two options which were discussed:

Have max debouncer chip connected to uC and handle inside interrupt.
Have the button connected to pin , do software debouncing and handling of button presses in polling inside while.


texts: Calculating R, C & maximum input current of Oscillator Circuit

texts:
I have been trying all day to understand how either one of the values C1, Rs2 or the maximum input current can be initially calculated. I have worked out the equations however it seems that there is no obvious starting point, every equation needs a value of either Rs2, C1 or the maximum input current. What value can be determined first? I think it might be the maximum input current, but again I can't seem to find a solution. I have read on a few forums that the audio range oscillates typically around 0.25uF to 0.25mA in a standard oscillator. So I could use 0.25mA, but that isn't a very accurate design method, since surely the maximum current is dependant to the circuit design. Any ideas? would it have something to the with the TL084 data sheet ?

Design Specs:
Frequency Range: 20Hz - 2000Hz
Voltage range of V7: 0v - 5V


texts:
Simple question, I have to make a Kelvin probe. We need to find how to make one on the internet.

However, I don't know if there are other terminology, or if I'm searching in a wrong way, but I can't seem to find how to make one.

What would be a proper way to find models for this?


texts: Outdoor versus indoor amourphous silicon solar cells

texts:
I've read in a few articles that amorphous silicon (a-Si) based solar cells have a greater spectral response for indoor light conditions here. If this is the case, then why manufacturers emphasize that their a-Si cells are for outdoor conditions and not for indoor or vice versa? It is of course understandable that in indoor you get less voltage and/or current.

My second question, according to this, protection and durability are the main difference between outdoor and indoor cells. If that's the case, then wouldn't it be more reasonable to go for outdoor cells if the final product is being used indoor AND outdoor?

Thanks


texts: What does the fermi-level increase in reverse-bias?

texts:
Fermi-level tells us the probability of finding an electron at 50%. When you look at an energy band diagram in reverse-bias you can see the Fermi-level increases in the p-type semi-conductor. Why does this occur?
My second question is why does the energy of the valence band increase? Shouldn't it be less because it has a lot of holes?


texts: Is this IR LED driver circuit with a transistor OK?

texts:
I am making a custom IR array board with a custom Arduino (only ATMEGA328 and necessary components.) So please tell me will this be fine or if I need to make some changes.

IR LED = 940nm, continuous forward current is 100mA, the forward voltage is 1.4.
         Current forward = 20mA with 1.2 forward voltage.

simulate this circuit – Schematic created using CircuitLab

Please do suggest will it work with IRFz44N?

So instead of if I use any NPN transistor with this parallel circuit, it will work fine, right? So please let me know if this is right or wrong.


texts: charging capacitors in series discharging in parallel

texts: If you charge two capacitors \$C_1, C_2\$in series with some voltage \$V_0\$  and then discharge them in parallel to find an output voltage \$V_1\$, how would you do so? Right now I know the total charge on the capacitors is \$Q = C_1C_2/(C_1 + C_2) V_0\$ but I'm not sure how to relate the total charge to an output voltage if they are discharging in parallel.


texts: What is a typical reverse recovery time for a zener diode, or is reverse recovery time not applicable to zener diodes?

texts:
A little background.. I'm trying to understand how zener diodes respond to high voltage transients. I stumbled across discussions of reverse recovery time  and I'm curious how it applies specifically to zeners.

I understand that zener diodes aren't typically used in a forward biased mode, which might be the reason manufacturers don't seem to publish the value of reverse recovery time on their data sheets, but I'm still curious about typical values. I found this brief table on Digi-Key, but it doesn't provide any actual values, it only suggests that the reverse recovery time is long compared to schottky diodes.

Thanks!


texts: Consider this circuit, this is a gyrator and acts like an inductor. Why when we analysis this circuit do we use assume negative feedback (i.e. the voltage at each input is the same). I thought that we only use negative feedback when the output is connected to only the inverting input, however in this circuit, we have both positive and negative feedback, as the output is connected to both the negative and positive inputs. So why do we only assume negative feedback takes place?


texts:
I have a question regarding the data during the BUSY state in a AHB bus. Consider the following example of an AHB master writing data onto an AHB slave:

TIME:        T1        T2        T3        T4
HTRANS:     NSEQ      BUSY      SEQ       IDLE
HADDR:      0x01      0x02      0x03      OxO4
HWDATA:     dataA     dataB     dataC     dataD
HREADY:       1         1         1         1
HBURST:     INCR      INCR      INCR      INCR

In the above case will the data written be as follows:

ADDR        DATA
----        ----
0x01        dataB
0x02        XXXX
0x03        dataD
0x04        XXXX
0x05        XXXX

Or will the data written be as follows:

ADDR        DATA
----        ----
0x01        dataC
0x02        XXXX
0x03        dataD
0x04        XXXX
0x05        XXXX

Or is it in some other way the data is written.

Thanks in advance.


texts: Level shifter using LM324 Op Amp for ADC reading

texts:
I'm want to digitize an +/- 2.5 V signal using an ADS1256. Since the IC can't take negative voltages I designed a level shifter with a LM324 to translate the +/-2.5 V signal to 0 - 5 V but I was only able to translate up to 3.4 V since the LM324 isn't rail-to-rail. I also realized that the input signal (+/-2.5V) and output signal (0-3V) have different phases. I would like to know if I'm losing resolution or accuracy reading designing the level shifter with a LM324 instead of a rail-to-rail Op-Amp. The frequency range of the signal is 1 to 10 Hz.

The circuit I used is from this website: https://vidnyankendra.org/2017/02/17/level-shifter-using-op-amp/


texts: How to wire latching SPDT relay using proximity switches without relay hanging

texts:
I have a hydraulic-driven piston pump that I designed and built.

I need a way for the pump to automaticlly go up and down.

I wired it using a SPDT relay and a 3 wire PNP NC (normally closed) and PNP NO (normally open) proxy switches. The NO proxy powers the relay then the NC proxy latches the relay until the nc proxy sensor switches breaking the latching current which will kill the relay untill the NO proxy switches starting the proces again..

My problem:

The NC has too much current leak which causes the relay to hang.

How do i get around this?

Or is there a better way of doing it?

Thanks for any input. This has me stumped.


texts: I’m trying to make power selection circuit with 9V and 3V. When I open 9V, it’s leaking to 3V side. I’m using fets and bjts. How can I make this circuit clear?


texts: Choosing a capacitor capacitance for a quartz resonator (ATMEGA328P)

texts:
I am designing a controller based on an ATMEGA328P-AU chip.

For the chip, I provided an external crystal oscillator at a frequency of 16MHz.

As a resonator I use YSX321SL

His description refers to load capacitors whose capacitance is equal to 12pF and ESR 60Ω (Max).
I plan to use two load SMD capacitors with a capacity of 22pF each.
The question is, did I choose the right capacity? Or is it worth reducing?


texts: Where is the Eagle component library for 0.1" breakaway headers?

texts:
I want to put some breakaway headers into my Eagle CAD file. By that, I mean these:

Does Eagle come packaged with a library for these? If so, what is the part called, and which library is it in?


texts: For AC equivalent circuits, it is written that, in the case of small input signals the emitter diode does not rectify, instead it offers a resistance called AC resistance. Why is this so? Why doesn't it rectify?


texts: Building a furnace with more than one thermocouple for accurate temperature measurement

texts:
I am a mechanical engineering student. I am in the process of making a special purpose heating equipment. It could be considered as a 3 phase electrical resistance furnace.
I want the temperature in the chamber to be uniform, so I want to place three K-type thermocouples to feed to a temperature controller-contactor set up to control the temperature.
I have previously built an electrical resistance furnace of 2 kW but with a single thermocouple and controller-contactor setup.
How can I have more than one thermocouple to control the temperature in the machine?
Edit 1. The purpose is to heat metal. Based on my calculation it would consume 36 kW of electricity. Based on the comments and answers, I am planning to split the heating coils into three separate sections with independent thermocouples and controller setup, where each section would be wired as an independent 3 phase heater.
Would this design work?


texts: Converting 2.1V RMS DAC output to instrument level 6.35mm jack

texts:
I'm not quite sure how level and impedance bridging works so I am hoping for an illuminating answer!

I'm generating audio with a PCM5102A DAC. The datasheet of the chip specifies a 2.1V RMS output signal at full volume, and a minimum "load impedance" of 1kΩ.

My questions are:

For equipment designed to take instrument level inputs (e.g guitar amps, DI's etc) what RMS voltage level and input impedance is expected? I.E how high is instrument level as opposed to line level, mic level, etc?
What are my options for converting the DAC output into an instrument level input? This is for an audiophile application, so sound quality is a high priority. It's also battery powered, so power efficiency is important too. Is a high quality transformer the way to go? If so, how do I do the maths to pick the right transformer?

Thanks!


texts: Are there any free or open source synthesis tools available that can convert Verilog RTL into a generic gate netlist?  (composed of generic NAND, NOR, XOR, D-flops/registers, etc.  Optimization not required.). If not for the full language, how about for a "useful" subset of RTL (beyond merely a Verilog gate level netlist)?


texts: Processing NTSC video feed for SPI display

texts:
I have recently started a project where I want to use this small camera and and have it relay the live video to a very small color LCD, like this one through an Arduino.

Unfortunately the camera has a NTSC output and the LCD has a SPI input, is there any way I can get the footage from the camera to display on the LCD or will I have to use a different screen?


texts: lab PSU based on a single power amplifier?

texts:
OPA548 op amp is a power amplifier capable of delivering 3 A at the output and limiting the current. at page 14 of the datasheet (figure 16) shows the schematic of a variable power supply based on OPA548.

I've never seen any commercial power supply based on a single power amplifier, while it makes sense to build such power supply to keep the cost low.

What are the disadvantages of building such power supply? why it isn't used in commercial PSUs?


texts: FTDI + Arduino mini on a custom board. Not able to program via FTDI & also directly via a blank arduino UNO

texts:
I have a custom board with an I2C sensor & FTDI + Arduino mini (powered from 3.3 Volt from FTDI IC which also powers the sensor).
Am not able to program via FTDI & also directly via a blank arduino UNO. But if I disconnect the arduino mini from the custom board I am able to program it (though with disfficulty, is reset an issue?)
Can some one help what might .


texts: Short circuit or disconnect to bypass a compressor

texts:
I have an Altec Lansing ATP3 2.1 audio system PCB which I reverse-engineered, and I would like to bypass the JFET compressor that's on it. Its active components are a JFET and four op-amps. I will connect the input to the output so it gets forwarded to the next stage.

My question is: should I disconnect the input and output from the compressor (in that case should I remove power supply as well, which would be very annoying), or can I leave it connected but short-circuited?

The block I want to short-circuit is the pink one on the left.

I realize the image is very small. The sound comes in on the right, in the green box. In the middle yellow box there's some trebble/volume/bass control. The small green box on its left merges the left and right channels to forward it to the subwoofer section, which is the complete left half of this diagram (except the red box on the left, which is just power). Signal then goes through a low-pass, a small equalizer and a compressor (the big purple box). It finally gets amplified in the brown power amp.


texts: How does spread spectrum VCXO (voltage controlled oscillator improve EMI on your board?

texts: I have seen people adding spread spectrum voltage controlled oscillator to EMI on the board, How is EMI affected by single spectrum crystal and with spread spectrum crystal.


texts: Why do real LC oscillating circuits not oscillate at the resonance frequency?

texts:
Consider these two simple LC oscillators with ideal op-amps:

simulate this circuit – Schematic created using CircuitLab

The resonance frequency is for both circuits about 159 kHz, however neither of the two will oscillate at that frequency in both the simulations and the real application. Why is that?

For instance, the first circuit, when tested, oscillates with a frequency of about 132 kHz and 156 kHz in the LTspice simulation. Ok, components are not perfect, but here we are significantly off the expected value. Furthermore, taking into account the internal resistance of the capacitor and inductor, if you consider a dumped RLC circuit with dumped oscillations, the frequency should still be the resonance frequency.

In many other (more complex circuits) I often read that the LC couple will oscillate at the resonance frequency $$\frac{1}{2\pi\sqrt{LC}}$$. However, this is almost never the case, and the frequency is far off that value (again, why?).


texts: what is the difference between time domain and frequency domain components? How do these domains differ from each other?


texts: My cable to charge my iPad has recently exposed some metal wire (due to the plastic insulating splitting). How dangerous is such a wire? If I was to touch the wire when plugged in to the mains, what would be the likely outcome?


texts: Does a constant current source add to existing current?

texts:
If I have a circuit where one branch contains a constant current source (e.g. 2A), does the current leading out of the current source equal the current leading into it (e.g. 4A) plus the current of the current source? That is, is the current leading out of the current source 2A+4A = 6A?

Or does the current source simply ensure that the current along the entire branch is equal to its value, e.g. if the constant current source was 2A the current along the entire branch would be 2A.

EDIT: Here is a diagram; I'm asking if \$I_A = I_B = 5A\$ or if \$I_B = I_A + 5A\$. Apologies for my poor MS paint skills


texts: CMOS inverter with capacitive load design

texts: I have been tasked with making a CMOS inverter with a range of capacitive load between 1pF to 1uF, with the TN0704 and TP0604. I am not really sure how to account for the range of capacitances. Should I find the mean and design a circuit based on that, or do I have to do something else?


texts: Noise and flickering first LED (APA 102)

texts:
I'm designing a circuit board to distribute power and data to 8 APA102 strips using a Teensy 3.2. While the first version of my board mostly works, I'm having some issues I'd like to solve for a second revision. The setup is as follows:
Pic 1:

Pic 2:

There are 8 radial LED outputs around the edge of a circular card (these are on sub-boards with card edge sockets, see Pic 1). High current 5V power for the strips comes from a secondary board (currently just a different power supply) through header pins as close to the outputs as possible. The Teensy is powered by a small 5V regulator and recommended capacitors from the datasheet. Next to each LED output is a NL27WZ16 buffer chip that boosts the 3.3V Teensy signals to 5V for the LEDs. The Vcc for the buffers comes from the same 5V supply as the Teensy and the top layer is a ground pour.
The problem
The issue is that the first LED in the strip flickers. I'm currently testing only 1 strip. Probing around there seems to be noise in the 5V, data, and clock lines at the input of the strip. But only when the clock signal is active. This is what I see on my scope:
Pic 3

Yellow is the power and the noise is about 1V pk-pk. Blue is the clock signal and purple is the data. It looks like the noise is imposed on the clock and data signals and I believe this is likely the cause of the flicker. Since APA102's retransmit data to the next LED, the signals look much cleaner a short distance down the strip. (This is supported by the fact that the second and third LEDs do flicker a tiny bit but not nearly as much as the first). The noise also appears at the input of the Teensy and in the 3.3V output of data.
The power supplies on their own look clean. The Teensy (on its own) outputs clean data. But when it's all hooked up (with or without the strip) the noise shows up.
I've tried adding capacitors in various places, but have had no luck in filtering out the noise.
Two hypotheses of mine:

The 5V lines to the buffers are 10 mil traces that run alongside the clock and data lines heading to that same buffer. You can see the 5V and data lines in Pic 2. The clock also runs in parallel, but on a hidden layer. The 5V traces measure around 6 ohms. I have a feeling these might be too thin and also that it's a bad idea to run them alongside the clock/data.
I did not put any decoupling capacitors with the buffers. Although it would seem from reading online that they aren't necessarily needed for buffers (and the Vcc/Gnd pins are in the middle of the footprint, making a minimum-distance capacitor difficult).

I plan to change the 5V lines to a whole power plane for rev 2, as well as add decoupling capacitors for the buffers. However I'd like to know if I'm on the right path, before I spend more money and wait 3 weeks to find out I didn't solve the problem...
I also have a small card-edge adapter board that solders to the end of the strip (See Pic 1) where I could put the buffers to get it as close to the strip as possible. However the Vcc would need to come from the 5V feeding the strip rather than the 5V feeding the Teensy. I have no idea if this would be better or worse.


texts: Why feedback resistor be at least 10 times of the input resistance?

texts:
Figure below is an integrator with reduced output offset due to the 10R shunted at the capacitor. It was written on the book that:

One way to reduce the effect of input offset voltage is to decrease the voltage gain at zero frequency(DC) by inserting a resistor in parallel with the capacitor, as shown in figure below. This resistor should be at least 10 times larger than the input resistor

Why should the resistor be at least 10 times of the input resistor?
Why not use the same resistance on the input for the feedback resistance so that the input offset voltage will only be amplified by 1 instead of 10 when using 10R?


texts:
I researched online and came across a code given here for PWM source in LTSPICE.
When I save this .asc and try to open the same, I get the following error:

  Aborting:

  Unknown schematic syntax:

  SHEET 1 880 680

How do I solve such an error?


texts: Model for Diode Shows Voltage Increase not Drop

texts:
It's well-known that if a diode is forward biased at a sufficient voltage, there is a voltage drop across the diode, i.e. it dissipates power.

However, I was reading Wikipedia's article on the depletion region of the diode (aka PN junction), and it occurred to me the electric field, E, as labeled below, is set up by immobilized ions and causes the voltage, V, as indicated to be positive:

I've also drawn the symbol of the diode in the above.

This result is definitely what I would expect, because if a battery (and resistor) is connected to the diode in the usual, forward-biased way, there should be voltage drop across the diode and the voltage V (as labeled) should be negative.

Where did I go wrong?


texts:
I am trying to communicate with external flash via quadspi but this time with cubemx and hal libraries. Everything seems to be working fine unless I write something bigger than 0x03 to address register. When I write address 0x04 or bigger, program just stuck. I debugged and after this line

if(((HAL_GetTick() - Tickstart) > Timeout) || (Timeout == 0U))
  {
    hqspi->State     = HAL_QSPI_STATE_ERROR;        // it doesnt get in
    hqspi->ErrorCode |= HAL_QSPI_ERROR_TIMEOUT;     // this function.
                                                    // loops without entering
    return HAL_ERROR;
  }

it goes to

__weak uint32_t HAL_GetTick(void)
{
   return uwTick;
}

and loops back .

This is the part of my code where this error occurs

static void quadspi_getFeature(void){
    getFeature.InstructionMode              =   QSPI_INSTRUCTION_1_LINE;
    getFeature.Instruction                  =   GET_FEATURE;
    getFeature.AddressMode                  =   QSPI_ADDRESS_1_LINE;
    getFeature.AddressSize                  =   QSPI_ADDRESS_8_BITS;
    getFeature.AlternateByteMode            =   QSPI_ALTERNATE_BYTES_NONE;
    getFeature.DataMode                     =   QSPI_DATA_NONE;
    getFeature.DummyCycles                  =   16;
    getFeature.Address                      =   STATUS_ADDRESS;
    getFeature.DdrMode                      =   QSPI_DDR_MODE_DISABLE;
    getFeature.SIOOMode                     =   QSPI_SIOO_INST_EVERY_CMD;
    getFeature.NbData                       =   0;
    HAL_QSPI_Command(&hqspi, &getFeature, 1000);
}

I tried changing the value of TimeOut in HAL_QSPI_Transmit command but nothing changed.


texts: Potentiostat circuit biased with three independent sources

texts:
How might a potentiostat circuit be designed such that it is biased with three independent AC sources, the reference electrode is biased at $$\varepsilon = 2sin(\omega t) + 3sin(\omega t) + 4sin(2\omega t)$$

and

$$Rref = 1k\Omega$$

Note: the solution returned for the problem only mentions which electrodes are capped, circled or arrowed: AE, WE, and RE respectively.


texts: How to pick voltage rating for capacitors

texts: Will using a 20V MLCC capacitor on a 3.3V signal make any difference compared to using say a 6.3V capacitor?


texts:
I recently got a batch of old microcontrollers (8052 and Z8671) and I just want to get a minimum working set up for them.

Since these microcontrollers already have most everything baked into them (BASIC, RAM, ROM, Serial Ports), it seems like it'd be a simple matter of plugging them in to an FTDI chip and going about myself.

Looking at the Intel 8052 datasheet, it seems like all I need is a power source, crystal oscillator, and a serial port. Since the FTDI FT232RL is a very common and readily accessible chip, I'm using that for both power and serial I/O.

Here is what I'm using as a schematic.

With all that in place, and trying to use both minicom and picocom, I get no response from the chip at all.

What is it that I'm missing? I've tried using a similar set up for the Z8671 and haven't gotten a response as well.

For reference, here is the pinout of the 8052


texts: Each of the pins is a discrete channel/line and I would like to plug this into a breadboard - does anyone know what type of connector would let me split these out please? I know I could make a breakout board but a cable would be nice.


texts: What are the male pin ends on stranded jumper wires called?

texts:
I have a pile of stranded breadboard wires, but need to buy or make more. The red one on the left have a solid metal pin, a molded plastic barrel, and stranded wire, and was purchased at Amazon. Most of the stranded jumper wire sets appear to be more or less identical to that.

The blue one on the right also has a solid metal pin, but the black part seems like heat-shrink tubing.

I'm having a hard time sourcing the metal pins. It is easy enough to find square pins intended for various connector systems, but I don't know how to search for the round ones.

My end goal is to build a small quantity (dozens) of jumpers for my own use. I can fall back on buying more from Amazon, but the molded plastic smells terrible, even after weeks of outgassing.

Edit: Related question. The closest answer to my question is a suggestion for Molex crimp-on pins. Those are close, but not quite what I'm looking for.


texts: ICE-electric transmission drivetrain parameters

texts:
Pardon me if this question covers too many elements; also, originally I posted this in Engineering stack-exchange but it may be more relevant here.
Basically I do not fully comprehend what would be the important parameters which must be matched for a system to work which is based on:
an internal combustion petrol engine, whose output shaft drives a BLDC generator, which in turn generates power for a BLDC motor
Essentially, what is confusing is that I find information regarding BLDCs that they are actually (perhaps only some of them; but the ones I was looking at) 3-phase AC motors which then have rectifiers to change AC to DC (if a generator), or a converter to transform DC input power to 3-phase AC, if used as a motor. Also, as far as I understood, to power the correct sequence of coils, if using a DC power from a battery, an ESC electronic speed controller is necessary.
So, would a Petrol>Generator>Motor setup be possible without such power conversion (directly 3-phase AC from the generator to the motor) and without electronic speed controllers?
[That is, if the petrol engine has a throttle, would that be sufficient as a means of controlling how much power the generator is providing to the electrical motor, therefore directly controlling the electrical motor power output, by the speed of the petrol engine? Or do the generator and motor have to be identical for that to work, that is, which parameters need to be matched between them? The kV of the electric generator and motor (RPM/V)? or maybe their rated RPM, or pole numbers, need to be the same?
I was trying to understand this setup with the following example parameters:
Engine: 2-stroke petrol
•   35kW @ 6000 RPM
Generator: BLDC permanent magnet synchronous motor (PMSM), axial flux, sinusoidal three-phase, out-runner
•   33kW @ 6000 RPM, 120V
Motor: BLDC PMSM, in-runner
•   33kW @ 8400 RPM, 120V
the generator efficiency at the mentioned RPM is 90-96% depending on torque, but let’s ignore the efficiency for the sake of clarity.
So, what I would be very grateful to understand, is what are the requirements for this system to work properly when starting the petrol engine & changing its speed/power?
Thank you


texts:
I need to replace the capacitors on a blower motor, they heated and leaked. I couldn't find much capacitors that are compatible with the casing and has the same rating as the old ones. I however managed to find this one on Digikey.
https://www.digikey.ca/short/z2jwbb
The original ones are two 'All Earth 50uf 250vac 60/50' connected in parallel acting as one capacitor.
The one I found on Digikey has 4 terminals, 2 on each side, while the old one only has 2, 1 on each side.
I tried reading the datasheet but couldn't find much information about the terminals connection. Why is there 4 terminals on the one I found and will it work if I replace the old ones with this one.
I have attached two images of the old ones.


texts: Viability for thermoelectric cooling in a computer setting

texts: I have a very powerful server computer that needs to be running 24/7, and the twin watercooled (with multiple fans) CPU is still overheating largely because the room it's stored in gets quite hot in the summertime. Is thermoelectric cooling a viable method to help cool the radiators faster, or is refrigeration the only way to improve the setup without completely changing the environment?


texts:
Is anyone aware of some website that keeps an up to date list of running hardware, electronics or electrical design competitions/challenges/contests? I am looking for the types of things that a hobbyist would enter - not something where university researchers compete for large funding.

An example would be something like the AVR Hero contest.


texts: USB type-c power supply (up to 20V 5A) from DC source

texts:
I have a custom made 5s power bank (30 x 18650 cells) and I want to make a power supply to charge my laptop using this power bank. It's not a big deal to make a 5V charger because I just have to hard wire a 5V step down regulator and it will work, but what about higher voltages?

Of course, I can use a standard AC power supply and connect it using a car power inverter, but efficiency in this case will be quite low. I tried to find such power supply/controller on aliexpress or ebay, but it looks like only 5V versions are available. What is the best/easiest way to do it?

Thank you!


texts: How to measure power consumed by mains device

texts:
I would like to measure the power consumed by a mains device. I have heard that it's not as trivial as simply measuring the average current, as the device may be resistive, capacitive or inductive, and these things will measure differently.

Is there a reliable way for an MCU to measure the power used by a mains device if you don't know in advance if it will be a resistive, capacitive or inductive load? (Even if it involves measuring the instantaneous current and voltage at a high rate and using the MCU to keep track of the power consumed during each 50Hz cycle).


texts: Is it possible to build laptop power adapters that are considerably smaller and lighter?

texts:
I am considering an alternative to the well know 85W Apple power adapter (or lets call it a brick, as it is big and heavy).

I am wondering if there is any technology for producing smaller power adaptors of the same power that that would be much much smaller and lighter? graphene maybe?


texts: draw dotted/dashed rectangles in Eagle schematic

texts:
I'm trying to draw some dashed/dotted rectangles in Eagle schematic to annotate functional groups like in this link

I tried to draw rectangle and switch it to different types e.g. symbol, net, info... all failed so far


texts: Applying Thevenin's theorem between 3 points

texts: I'm studying about transistor polarisation and got confused by this application of Thevenin's theorem, can someone please explain why eT is between B and M and why Vcc stayed even though it's not removed when finding eT? I'm not familiar with using Thevenin's theorem to a charge that's connected to the circuit via 3 points.


texts: Is it possible to change the size and look of blocks/symbols in Quartus Schematic Editor

texts:
I want to change shapes of and resize blocks/symbols to make the schematic tidier. For example, I want to make my multiplexers the shape of a trapezoid (like commonly drawn on paper) and make them smaller so they will be not as big as, for example, a CPU I have designed.

This is a problem because sometimes a multiplexer has to be added as an input to every pin of another block, then the whole design looks like a great big mess.

Is there a way to do those in Quartus Prime Lite.


texts: PCB design using code instead of clicking a mouse?

texts: I'm just getting into PCB design and I generally have trouble learning how to use GUIs with menus and mouse clicking. Do some engineers use something more like code to generate PCBs?


texts: Trouble splitting off LFO signal to drive LED

texts:
Background: I am trying to build a very simple noise box that doesn't need to be tuned to 1V/Oct or anything special.  It simply has one VCO, two LFOs, and a VCA.  The circuit is powered off of a dual 9V power supply.  The LFOs can affect either the VCO or VCA or both.  The LFOs and VCOs are all built using LM741 circuits and the VCA us built using an LM13700 Operational Transconductance Amplifier (OTA).  I have a very basic idea of how the 741s work to do their jobs, but the OTA VCA circuit pulled from the datasheet is completely over my head, partly because I'm weak in understanding the concepts of current based op amps.  I've gotten all the parts of the circuit working and would like to start adding some LED effects to the oscillators.  I located the part in the circuit where the LFO signal comes out of its final stage of amplification and into a summer amplifier that feeds the VCO.  At that point, I split the signal off into a voltage follower op amp.  The output of that op amp simply feeds an LED -> current limiting resistor -> negative supply voltage.

Problem: One of the LFO signals cooperates with the buffer and the LED works perfectly, however the other LFO signal suddenly drops to a fixed voltage when run through the buffer (about -5v) and remains there.  It seems to disregard the input signal all together.  It makes absolutely no sense to me why this might happen and I have checked all the buffer connections to make sure there aren't any open circuits.  I have as best as possible mapped out the circuit to all the points where current might be introduced.  Can anyone tell me if something looks wrong here and why I might see one buffer properly buffer the signal while the other buffer seems to ignore the signal and fix the output to -5V constantly (no oscillating) when the input signal oscillated from -5V to +5V?

What I've tried/voltage tests at nodes:

Voltage at non-inverting input side of R18 = LFO1 Signal (-5V to +5V) [Expected]
Voltage at non-inverting input side of R20 = LFO2 Signal (-5V to +5V) [Expected]
Voltage at output of LED buffer for LFO2 = (-5V to 5V) [Expected]
Voltage at output of LED buffer for LFO1 = (-5V Constant) [Not Expected]
Troubleshooting Attempt: I disconnected the VCO -> VCA Gain inputs (that's Pin 1) all together in case there may have been some current sinking going on but it didn't appear to change anything.
Troubleshooting Attempt: for both VCOs, I bypassed the buffers all together and connected the LEDs directly to R10 and R11.  This seems to work on both LFOs, but I don't want to do this because I think it really would draw current away from the signal, whereas I understand a buffer to keep the input side protected from current sinks due to the high impedance input.  Is that right?

Below is the Schematic I drew out from what is on my breadboard.  The schematic goes as far out as I thought necessary to identify any nodes where things might affect my LED buffer.  Beyond that though it didn't appear there would be any disruption to other areas.  For example, the lm13700 circuit shows only pin 1 connected.  The actual schematic follows that of the VCA example on the data sheet.  From that, it appeared that the current going to the Gain pin was independent of the other parts of that circuit.  Please let me know if this is an incorrect assumption or if additional info is needed.  Thanks all for reading this.

simulate this circuit – Schematic created using CircuitLab


texts: Multiple Ultrasonic Rangefinder Question

texts:
I've been doing some research on ultrasonic range finders as sensors for robotics. I've seen them being attached to servos and pivoted to effectively "look" in front of the robot and make sure the path is clear.

While this approach is very effective for the most part, I am hoping it can be improved. What I need to know is if it is possible to use several ultrasonic transducers (lets say 4) at the same time by having each one emit and listen for a different frequency?

Here's a picture of what I mean:

In this picture, the green box represents my robot. The tiny blue box represents a panel with 4 separately angled ultrasonic transducers. The rays emitting from the blue box represent the angle at which each transducer is aimed. The different colors of the rays represent different frequencies. Say, for example: 34KHz, 36KHz, 38KHz, and 40KHz.

If this is possible, how would I go about getting ultrasonic transducers that produce different frequencies, most of them seem to come with 40KHz. Can I just regulate the frequency of them through my Arduino board somehow?

edit
Furthermore, is it possible to use one ultrasonic transducer to produce the full range of frequencies? IE: I rotate the servo 4 times as fast, ping 4 times as fest, but step up a frequency interval after each ping? Can a single transducer listen for variable frequencies?


texts: Indutor and capacitor selection for DC-DC convertor

texts:
Assummed that I got some value from calculation to meet required Voltage ripple and current comsumption at specific switching frequency (says 100kHz).
For capacitor.
As real capacitor don't behave like ideal one. How to select multiple capacitor type, value to paralel to meet requirement above. Also we can't make Ideal frequency response. which reponse is okay in this application? How we can pick real capacitor to make the circuit?
For Inductor.
Based on maximum inductor current how to select copper wire size? (take skin effect into account)
For Example
I used adafruit boost calculator with requirement below.

And I got this component value.

How I pick real component from this value?
Also for inductor I might made by my self. How to select copper wire size?


texts: Comunication Xbee S1 Coordinator to End Device

texts:
I am new in the Xbee world, I have 4 Xbee S1 802.15.4, that 3 are end device and one a coordinator.

The end devices transmit good to coordinator.The coordinator is connect to Raspberry Pi via USB with a Xbee USB Explorer. The communication is through serial and can see the data for the end devices, use python.

How can send a signal from the coordinator to each end device for wait to start the transmission?

In this moment I have the configuration in API Mode.


texts: Detect if coil is near steel piece using MCU

texts: How to detect inductance change using MCU (lowest power methods preferred). I want to detect if the coil touches steel piece (higher inductance) and when it does not (lower inductance). Basically I need to compare inductances at two positions and compare the values. Then I will derive a threshold value to detect when the coil is away from the steel piece.


texts: How to measure the saturation current of a diode

texts: Just wondering how with DC measurements you could measure a diodes saturation current and the Emission coefficient factor N. I was thinking a basic DC circuit varying the voltage taking voltage measurements, then plot the V-I and then try fit the diode equation to the graph?


texts: I need explanation on some digital multimeter (DMM) specifications

texts:
What is digital multimeter (DMM) ranges reading; resistance : 400 ohm - 40 Mohm supposed to mean?
would it mean the DMM cannot measure a material resistive property of less than 400 ohm ?
And what does tolerance 1% rdg. indicate which followed by: 5 dgt mean ?
Thanks in advance


texts: Wall mount Rotary Dimmer installed on lamp cord?

texts:
Could I do something like the diagram below, or is this a technically bad idea?

I like the feel of this rotary dimmer and was wondering if it was safe to install it on the cord between the outlet and the lamp.

On top of that, I would then like to install a touch On/Off so that I can simply tap the lamp to turn off the light at the defined dimness. Then when I touch the lamp again to turn it on, the dimness would be at what it was when the lamp turned off.

Thanks for you help.


texts:
I'm working on a linear 5 V power supply for the first time. I'm using the L78S05C as I was hoping for a little elbow room on the amperage over the standard 1.5 A version.
Circuit tested perfectly on the bread board, so had at it. Completely done, it would not power up my device (needing 5 V). I tore it down to find the transformer (Hammond 166N6) 6.3+0+6.3, while reading over 12 V using a multimeter, is really NOT the RMS voltage. I don't remember exactly, but barely getting 8.5 V RMS using my oscilloscope.
I'm guessing the lower voltage, voltage drop from the full-wave rectifier and then again the 2 V drop from the L78S05 was my issue.
Moving on, to be sure I send 15 V to the L78S05 using my adjustable DC voltage regulator and the output of L78 is only 4.8 volts.
I added two 100 uF capacitors, one on Vi and one on Vo to ground, besides the recommended 0.33 uF and 0.1 uF (see Figure 17 from the datasheet below).

I figured instead of aimlessly de-soldering the additional caps, trial and error, I should ask here why the voltage is so low.


texts: I've made a board with two Ethernet ports on it and so far when testing it for EMC I've been connecting them together with a single cable. My assumption was that since there are constant keepalive packets being transmitted the cable will always radiate and thus simulate normal usage EM emissions. Are there any flaws in this logic? Is there a better approach to simulating real life emissions from the Ethernet cables and Ethernet-enabled devices?


texts: Can a USB device have a low bandwidth because of poor connection?

texts:
I found in the garbage an old USB webcam with an OV 518 chip. The USB cable that was going out of it, however, wasn't there. There were just some remains of the tiny red/white/green/black wires that are usually inside the USB cable. I do not know why, but there are two copies of the black wire.

Therefore I made a very quick contact (without tin, just by doing some knots) with a USB cable that I had cut in half. You can see it in the following picture:

.

The camera is recognized by my computer (I use Mac OS X and macam ), but it complains that it has "not enough bandwith" and cannot do any acquisition.

Now, my question.

I do not know anything about the camera and it might well be that it is faulty for its own reasons, in which case I would return it to the garbage. But could it be that the bandwidth is low because of the horrible, handmade, connection? I do not know the USB standard so I do not know if the bandwidth depends on the quality of the connection. Is there a way, such as a software utility, to check the quality of a USB connection? If this is the case, I guess I could try to do a better connection and make it work.

EDIT: Now I have soldered the wires, so I made a stronger connection. The problem persists exactly as before


texts: Ground loop- Why would current flow between 2 earth grounds when signal return path offers the least impedance?

texts:
Lets say I have 2 ICs- C1 and C2 acting as driver and receiver for the digital signal. The signal is transmitted through a conductor/cable ( 2 wires) as shown below. I have 2 doubts

1. What would be the direction of current flow through GND wire? Will it be alternating? From my limited knowledge in semiconductors, I think when the signal is high, it would charge the internal capacitor of receiver and discharge the same cap when the signal is low. Hence I expect an alternating ( +ve and -ve) current through the cable. Is it correct?

2. Now why would the return current choose the alternate return path? The current would choose the least impedance path, and for an alternating current it is obviously the gnd return path through cable (least inductance path). If any dc component is there it may divide and flow through alternate return path as well.

3. Now what is the problem if at all some dc current flows through alternate return path? There is no EMI issues caused by a dc current.

Now lets say a small fraction of ac current flows through earth return path.  Is it correct to consider it as a current loop since both the return currents are flowing in the same direction and not really circulating?

So much is written on this which I need to  research more . I will proceed after getting clarity on atleast 1st two questions


texts:
I am using an Arduino to read a keypad and open an electric strike upon keypad PIN entry. For this sketch I wanted to use some sort of lightweight encryption to store the PINs in EEProm.
Does anyone know of such a library? I have heard it may be possible using TwoFish.


texts: How do I prevent my BMS from tripping when solenoid is connected?

texts:
I am working on a project that is effectively just a battery powered reticulation system. It is charged through a solar array and cheap MPPT charger, which connects into the battery via the BMS. The BMS output goes into voltage regulators (in series, 5v and 12v respectively) to power an Arduino and a solenoid valve.
My issue is that when I connect the valve to my output wires (from the voltage regulator) it turns on for less than half a second, then snaps back shut. I then have to reset the BMS (by connecting the battery + to the BMS out +) in order to have power again. If I bypass the BMS, this does not happen and the solenoid stays open whilst it is connected. Why is this happening?
Notes:
This is the BMS: https://www.ebay.com.au/itm/1S-2S-3S-4S-5S-6S-BMS-PCB-Protection-Board-For-18650-Li-ion-Lithium-Battery-Cell/142415496988 (the 4s 20A option)
The battery pack is salvaged from an old laptop (conveniently already assembled how I needed it)
The wire I am using is a combination of 26AWG (yes I know that is very thin, but it is plenty for the max current this will have to handle) and 9AWG wire. No length of wire (in the relevant area) is longer than 5cm. The BMS is directly on top of the battery pack (separated by some thin plastic).
The solenoid I am using is 12V and 7W (0.58A)/(0.44A at the 16V battery once converted)
I am just manually connecting the valve when I test this setup, it will eventually be used with a MOSFET. It also has a reverse biased diode connected, if that is at all relevant.
EDIT: Sorry for the (really long) delay, I've been busy.
Here is the (rough and messy, I tried to not overlap wires and failed, sorry) schematic for the system, the cells represent the batteries and BMS whilst the voltage source represents the solar panels and charger:

The batteries are connected to the BMS like this:

I've also done a few tests very recently and found some very confusing things:

Occasionally (once every few tries), it will work fine, but when I come back a few minutes later to test it again it has the issue mentioned above
Using some resistors, I've confirmed that the BMS can supply the required amount of current (more than the solenoid draws)
I know the solenoid works as it functions properly on other power sources
The battery pack powers other things just fine such as a 12v 0.2A fan

Could my BMS be broken or am I doing something wrong?


texts: Voltage regulation: I need 2x12V DC from 25V DC

texts:
I have this problem: i have an op amp, that is powered with +12v and -12v dc. Also, there is a ground connection at 0v.

Yet, my power source has around 25v dc and the voltage point 'in the middle' is missing.

I want to turn these 25V into 2x12V supply power. I expect a maximum current flow of 2A.

Now my question: Do you know a voltage regulator part or whatever circuit that can do this?


texts:
I'm using SIM900A mini v3.8.2 GSM/GPRS board to make a phone call on certain condition. I have connected the module through CH340 USB to TTL converter to PC (Windows 10) for testing. All Connections are OK. I'm using 5V 2A power supply so no power issues. Connection LED blinks after every 3 seconds means network is connected. Power LED is on without any blinking.

And I'm using AT Command Tester software for testing SIM900A functionality.

Issues:
1st issue is that when I call on a number it simply says NO CARRIER or  NO Carrier: Call dis-connected.
2nd issue is that it does not send or receive any SMS/Voice Calls.

Note: I have sufficient tariff/balance for SMS and voice calling. And SIM is unlocked.

Different AT commands responses are as follows:

But When I try to make a phone call its response is this:

And when I send a SMS, SIM900A response is as follows:

Now where is the problem..? I also tested AT commands for voice calling in Arduino Terminal manually but problem is same... Is there any 1st time settings or configuration has to be set for successful communication..? like APN , SIM provider settings etc...? or something else...?
Please help me about this...Thanks...!


texts: Power Supply Issue, Voltage Drop Under Load

texts:
I have the Ardupilot Mega flight control board (APM), which outputs 4.8V. I want to power CC3200 MCU with it, which needs at least 3V for stable operation. I power APM using a power module connected to an adequate power source and can output up to 2Amps for APM and all the peripheral devices connected to it. That's way more than enough. When CC3200 is operative under full stress, it can draw up to 200mA.

I'm doing a level shifting on the 4.8V line, dropping it to 3.3V using two resistors 220Ohm and 100Ohm connecting them appropriately to form a voltage divider. 3.3V is the perfect voltage input for the MCU, which under full load should drop the voltage by maybe 0.1-0.2 Volts which is understandable.

However, when i make this voltage divider using the resistors i measure the voltage on the CC3200 and it's 0.3V, instead of ~3.1V! I've tried 2.2kOhm + 1kOhm with same results. Tried an other module (WiFi bluetooth module) the voltage there goes to 2V, kind of better, but still this is 1.3 voltage drop! I also tried powering led's and other stuff from the APM, but in all cases the voltage drops heavily when a load is connected to it when using a voltage divider for level translator. Nothing's wrong with CC3200, normally i power it using 2 AA batteries. But i would much rather power it from the APM.

But, if i power say the WiFi Bluetooth module without level shifting (it can handle up to 6V) the voltage remains almost perfectly stable to ~4.8Volts!

This issue has been troubling me. Is there not enough current to power the external device when using resistors as voltage divider (unfortunately i don't have another level translator device to test this theory)? Not much else comes to mind, but i don't know how to make sure. I need the help of more experienced and knowledgeable people. What could be the reason? What is wrong? What am i missing? Thanks in advance!


texts: Relationship between harmonic's amplitude and square wave's Tr and Pw

texts:
I started reading this TI guide on high speed layout guidelines and had some question on the theory of clock signals (pages 2 and 3).

From the image below it's clear that the amplitude of the first odd harmonic (3) is inversely proportional to the rise time of the signal, in that, a longer rise time leads to a smaller harmonic magnitude.

My questions are:

1) If the amplitude of harmonic (3) is 1/πTr what is the formula for computing the amplitude of the 5th, 7th harmonic etc.

2) What does the 1/πPw indicate? Is it the amplitude of the fundamental frequency?

3) Why does the graph start off horizontally, then drop at a random point with a 20dB/decade slope until the 3rd harmonic and then shift to a 40dB/decade slope. How should I interpret this graph?


texts:
I have seen many schematics using 22 ohm resistor in series with digital signal lines.
I was wondering is this always a MUST or there are there some special scenarios where we don't need them since they lower the signal's bandwidth.

For instance, are they needed on 48MHz signal line which is cca. 2cm long?

Is this somehow connected to STM32 output speed capabilities (low, high, ultra high speed, etc.)?


texts: I have a board that has a gyro and a 3-axis mems accelerometer.  Is it possible to measure constant velocity using accelerometer/Gyro. I find velocity by integrating (summing) acceleration over time.  Now if the body is moving with constant velocity, acceleration will be zero, and so velocity will come out 0 (falsely, since it might be some other constant also). What do I do, what is the alternate method I can use?


texts: Help with Piezo conditioning circuit schematic

texts:
I have the below schematic that uses a piezo sensor as input and relays that information to an Arduino board for processing. The schematic came from a few folks over at MIT that built a ping pong table that senses hits via 8 peizo sensors (4 per side of table).

As it states in their write up (found here section II.) the circuit is designed to filter, amplify, rectify and threshold the waveforms from the Piezo. The op-amps can share the same bias point and the comparators can share the same threshold.

My questions are:

The left-most highlighted square (my highlight) shows a symbol I've never seen before, there are two of them in fact in this diagram. What does this symbol mean? Is it a connection to something?
Of the right two highlights, the top seems to be digital ground (connected to Arduino?) and the bottom is earth ground (connected to grounded metal table?). Am I correct in this? The two lined ground is making me think it might be something else instead.
Is the right most circle at the end of the circuit connected to the I/O pin on the Arduino?
The left most earth ground symbol, shouldn't this be connected to Arduino ground instead? I have never wired a ground connection from an Arduino to an earth ground, typically using the ground pin on the Arduino board instead.
"The op-amps can share the same bias point", what does this mean exactly?
"The comparators can share the same threshold", what does this mean? Just that they can all be connected to a single Arduino?

For more insight, check out the PPPP page from MIT

Much appreciated for any help as I am decently versed in Arduino but not more advanced EE or reading schematics.


texts: How to diagnose powering damages and protect again surges?

texts:
I wanted to operate remotely a motor which is controlled by a manual key switch (still in place in case the automated way fails - which happened).

The switch:

I though by replacing it by basics relay commanded by wifi would have suit the need. I used sonoff 4ch pro r2 board with the following relays:

Even if the rating is different I thought I would give it a try - at worst the relay die and I change it to suits the same rating as the initial key switch.

However the replacement did not failed where I expected it initially.

Again, the idea was to mimic the work of the manual key switch.

The motor board has (4 inputs: +24VDC, GND, CMD CW clockwise, CMD CCW counterclockwise) CMD CW and CMD CCW are set to +24VDC to instruct the motor. The relays (RLY1 & RLY2) of the sonoff card is sending the +24VDC to the right CMD. Hardware exclusion makes it impossible to have CMD CW and CMD CCW up at the same time:

I powered the board with the same line as the motor. I knew it was risky because the voltage on this line has a motor on it. But still, it worked quite well for a long time.

I was just finishing to pair the sonoff with a rf433 when I started to test the motor and the C23 starting to fumes.

From my basic understanding: C23 (45uF 35V) is there to absorb small voltage fluctuation.
It burned A: because the voltage was too high or B: voltage was negative.

Q1: Is there a chance that only the C23 is to replace ? Or should I start to think to change voltage regulator MP2307DN too ? This is SOC so I think it will be quite difficult for my level of soldering.

Q2: Should I think to change the capacitor and the regulator by something different to ensure protection or how can I protect the circuit from surges and ensure this will never happen again ?

Sonoff 4ch pro schematic

MP2307DN voltage regulator datasheet


texts:
I am building a billboard with a moving part. The movement is an ore cart, rolling on a track. I have installed a chain loop below the cart to move it from one end of the sign to the other, then back again. It takes about 40 seconds to travel the 30 feet across the sign.
Problem: How do I get the reversible DC motor to switch directions as the cart nears the end of the track and make it cycle back?
I have plenty of 12v power, solar and stored. The motor has two leads, and is reversible, so all I need to do is to figure out how to reverse the polarity each time the cart nears an end of the track.
I'm thinking DPDT timer, set to change every 40 seconds, fine-tuned to how long it actually takes to traverse the track.


texts:
I want to obtain the inductance value from a coil. To do so i'm using a basic RL circuit as follows. The function generator has a 50 Ω internal resistance and the coil resistance is 87 Ω. The coil has a small sticker with it's value (6,24 mH) supposedly provided by the manufacturer. I would like to prove it experimentally to be sure that it's correct.

simulate this circuit – Schematic created using CircuitLab

As we know the voltage that goes through the coil tends to 0 following this expression: \$V_{L}(t)\$=V·\$e^{-t/τ}\$, where $$τ=\frac{L_{1}}{R}$$
What I was doing with the oscilloscope was taking the difference of time between the signal rising start and the moment where the exponential is the 36.79% of the initial value. Then considering this number τ and knowing R value I calculated L1 (L1=R·τ). The result is not the expected and I firmly believe that this method is not correct at all.

What I tried next was similar, taking two points but this time the first one is a little bit after the maximum voltage and the second the 36.79% of the first one. Now with the time and voltage difference between the two instants and the expression seen before I calculated $$L_{1}=\frac{-(t_{2}-t_{1})·R}{ln(\frac{V_{L}(t_{2}-t_{1})}{V})}$$
Again the result is not correct.

I would like to know what i'm doing wrong.

Anyway if you know a different and simple way to measure the inductance experimentally i'm open to sugestions.

Thanks!


texts: How to make a bidirectional power switch for negative supply rail controlled from logic level MCU

texts:
I'm looking to build a bidirectional power switch for a negative power rail. I have a +12V, +5V, +3V3 and -5V supply to switch. For the positive supplies, I'm using two P-channel mosfets in a common source configuration, which can be controlled directly from a logic level (0-5V) microcontroller:

I am struggling what is the easiest (low component count) solution for the -5V supply rail. My first thought was to use the same circuit, but then I need a negative gate source voltage to turn the fets on, meaning I would need to put roughly -7V on the gates (-5V + Vgs,th), which makes it complicated.

Another thought was to switch to two N-channel fets connected as common source, but then I would need -5V on the gates to keep them off, which I could do using a pulldown, but the ESD diodes of the IO pin of the MCU would pull the gate signal back up to 0V, turning the fets on.

My initial conclusion is therefore that I would probably need another FET to make it work, but I can't yet figure out how. Any ideas?


texts:
I have a circuit which has an exponential function as shown in the figure. I tried to put an anti-log opamp with the diode and BJT transistor, but did not get what I wanted.

I think the whole problem is in the "exp" part.

THE INTITIAL VALUES ARE a=2 , b=4 & c=6

Desire outputs


texts: PWM Control 24V Circuit with 3.3V ESP8266 NodeMCU

texts:
I want to control some white led lights (datasheet) with PWM.
The Leds are in a parallel-series circuit with 3 leds per series and multiple of those in parallel. (See Image below) The Leds itself are rated 3.4V, but because I am already using a 24V 6.25A Power Supply with some other stuff, I am running 24V lines and use a 155 Ohm resistor infront of each series.
How would I control all those leds with a 3.3V PWM signal? I saw some circuits using Mosfets but I have never used one of those so I am not sure what I am looking for if I would use one. The Mosfet would also have to be infront of the load, due to the Ground beeing shared with the other parts of the circuit.


texts: I'm doing my DIY project as an FM transmitter. When finding somewhere to buy a winding inductor, I found another type of inductor called 'axial inductor'. It's very strange to me; if it's an inductor, it seems more convenient than winding an inductor. Should I buy it instead of winding my own inductor?


texts:
Previously, i say sorry for my bad english grammar.

I have a project on stm32 with sim module 7500e (because i need post https)
The program works properly. But, after my board was successfully sent post https in 40 or 41 times, the program gets stucked (cannot send post https again), cause I was monitoring the program by using serial terminal.
For anticipate it, i press the reset button and the program can send post https again.

My question is how to reset board without press the reset button (or automatically in program) ?

Thank you very much.


texts:
I have no answer for this strange opamp behavior. The circuit shown is from a typical nonisolated ,Non grid-tie inverter product (imagine H bridge Inverter). which has a common -ve high power circuit and isolated low-voltage 24V and 3.3V. DC Bus and Battery share the same common -ve.

The battery voltage sensing opamp shows wrong output i.e 3.1V saturated voltage. whereas the DC Bus voltage opamp works well in all condition.
     Upon inspection of voltages i observe below voltage,
a) Following are the reading across various nodes of OPAMP (Opamp LMV931MGX/NOPB):
Bat- R104 to GND= -122
BAT+ R108 to GND= -16.9
Battery voltage 105.3
BAT U25 -ve IP (3) (R105)= 0.372V (note +ve sign)
BAT U25 +ve IP (1)(R110)= -0.385V (note -Ve sign)

DC link sensing U23 gain 0.004799
DC link sensing U23 Pin 3 (R95)=1.622
DC link sensing U23 Pin 1 (R102)=1.622

My question :

Why is the voltage on inverting and non-inverting pin are not the same? how can i make it work properly? also note that i assume Opamp is saturating because it is seeing (-ve) -0.0.385V at its +ve non inverting pin. How can i fix this? Note the 3.3V is isolated from HV (battery and DC bus) voltage it is reading differentially.
Both circuits are same in nature DC Bus sensing opamp has no issue and Battery sensing opamp throws wrong reading.
i have tried replacing opamp with equivalent part# but still, the issue is the same. I don't think this is noise related issue as i didn't see any sign of noise.

Edit: We have AC sensing in the same way as this. now noticed that when the AC sensing is in circuit we see this DC battery wrong reading issue , when we have AC sensing out of circuit. battery sensing circuit works fine (remember its non isolated H bridge inverter)


texts: security camera power by solar regulator

texts: i have a solar panel with regulator to run a a light as well as charge a battery. i want to add a security camera which uses a power supply of 9 volt dc and 600ma. instead of using an inverter and camera power supply would it not be more effiiceint to simply stepdown the 12 volt to 9 volt? i found a dc stepdown from 12 v to output of 9V with 2Amps. will this be okay and not damage camera?


texts: How could I add ~ 1 GHz frequency voltage noise of random intensity to a circuit?

texts:
I'm a chemist working in battery development, we don't have an electrical engineer on the team which is a bit of a pain.

Anyway, we want to add 1 GHz voltage noise of random intensity to our battery as it charges, in an attempt to suppress dendrites.

Can anyone advise? I know how to solder bits together if there's a certain type of circuit that does this.


texts: Adding filtering to an opamp feedback loop

texts:
I am simulating a circuit based on the OPA3355 opamp using TINA-TI.  Obvious warnings about simulation should be heeded but this is a TI amp in a TI program, so I'm hoping the results are largely accurate.

The schematic below is based on the most simple circuit from "Demystifying Single Supply Opamp Design" (as detailed in the article, there are improvements I could make to the single supply design).

Transient analysis looks good with high gain as expected, the input signal is 5Mhz and the output is nicely centred around mid-supply.

With the capacitor in the feedback loop however I get some interesting results from the a plot of the AC transfer characteristics.  I started by choosing R2 for the desired gain, then set C1 to a standard value to get a peak around 5Mhz.

By constructing the feedback loop in this way and applying maximum gain to only the frequency of interest, is this a good way to build some filtering into the amplification circuit?  Or have I magically simulated something that is a bad design for real life?


texts: Powering a microcontroller inductively from mains wire

texts:
I am in the process of making a mains power monitor using a SCT-013-000 CT clamp and an arduino mini, running on batteries. Even though I should be able to get many months of operation from two small AA batteries, would it be possible to use the clamp to harvest power to run the unit forever?

If I'm doing the maths correctly, two 10F 2.7v capacitors in series would keep a unit drawing an average of ~0.1mA, 5.4v->2.7v running for a couple of days even if there is no power usage on the mains wire?


texts: In a tristate buffer which transition time should be larger

texts:
I was having a doubt related to tristate buffers. I know that a tristate buffer allows an output port to assume a high impedance state in addition to the 0 and 1 logic levels, effectively removing the output from the circuit.

But does don't understand which transition time High impedance to conducting or vice-versa when connected on a bus should be larger for the tristate buffer

It will be helpful if you provide me with a circuit of tristate buffer with transistors or gates


texts: Correctly initialize a shift register (Verilog)

texts:
I've been struggling with a very simple Verilog program. It's a 4 bit shift register that gets rotated at every clock cycle and drives four LEDs. (As you can tell I'm new to FPAGs and HDLs.)

The problem: Below code synthesises without warnings and is successfully programmed into the FPGA. Then, upon start, nothing happens, the LEDs stay dark. The i_Switch_1 input was added to make something happen at all and indeed when I push the switch the LEDs start rotating.

Here's the Verilog code:

Version 1 (fail)

module top
   (input i_Clk,
    input i_Switch_1,
    output o_LED_1,
    output o_LED_2,
    output o_LED_3,
    output o_LED_4
   );

     reg [3:0]shift_reg;

     initial
         shift_reg = 4'b0001;   // has no effect

     always @(posedge i_Clk)
     begin
         shift_reg <= i_Switch_1 ? 4'b0001 : {shift_reg[2:0], shift_reg[3]};
     end

     assign o_LED_1 = shift_reg[0];
     assign o_LED_2 = shift_reg[1];
     assign o_LED_3 = shift_reg[2];
     assign o_LED_4 = shift_reg[3];

 endmodule

Assessment: My conclusion so far is that shift_reg is not initialised to 1. The RTL view below shows that no initialisation is synthesized.

I read in many places that the initial block is synthesizable, so I'm really puzzled, now.

Question 1: Is my assessment correct?

Question 2: Assuming my assessment is correct, what is the remedy? I've tried various things and none of them work:

Route in the reset pin, but that doesn't seem to be allowed.
Use a shift_reg==0 comparison (version 2 below)
Use a is_init flag (version 3 below)

I'm beginning to believe that I'm getting something fundamentally wrong. What is going on??

Version 2 (fail)

shift_reg <= (shift_reg==0 || i_Switch_1) ? 1 : {shift_reg[2:0], shift_reg[3]}

Version 3 (fail)

reg is_init;
initial
    is_init = 0;   // Must have this or else the is_init gets optimized out!

always @(posedge i_Clk)
begin
    if(~is_init || i_Switch_1) begin
        is_init <= 1;
        shift_reg <= 4'b0001;
    end
    else begin
        is_init <= 1;
        shift_reg <= {shift_reg[2:0], shift_reg[3]};
    end
end

Setup: LatticeSemi iCE40HX1K (nandland go board) using iCEcube2, synthesis tool is Synplify Pro.

--

Update

This here works:

Version 4 (success)

reg [3:0]shift_reg = 0;

always @(posedge i_Clk)
begin
    case(shift_reg)
    1: shift_reg <= 2;
    2: shift_reg <= 4;
    4: shift_reg <= 8;
    8: shift_reg <= 1;
    default:
        shift_reg <= 1;
    endcase
end

But the synthesis result is somewhat bloated:


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texts: Increase Measurement Distance of a Capacitive Proximity Sensor - Arduino Project

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So I am working on a project that I found online at (https://makezine.com/projects/a-touchless-3d-tracking-interface/).

However, instead of using my hand to track, I want to track an aluminum ball with 2cm radius, which is connected to ground. I am also using thin metal aluminum plates instead of the foil.
I cannot get the distance that I need, which is about 35cm.
My question is, how do I increase the measuring distance of the plate to reach the 35cm at least?

This is the circuit

Looking forward for all suggestions and help!!!

Thanks a lot in advance!


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Given the following circuit, how can I use terminal 3 to detect when the button has been pushed?

Everything right of the 3 pin terminal is a manufactured device- the Aiphone LE-D.
(Also note it's possible I got the capacitor polarity incorrect. I do have audio coming out from the speaker.)

I know there's no ground on the amp's negative terminal (makes sense) so I can't sink current from the microcontroller through terminal 3.

Can I tie the amp negative to ground without hurting the amplifier so that I can sink current through the push button?