texts: What is the simplest way to toggle a relay with analog feedback?

texts:
I've been playing with electronics for a long time, but am fairly new to digital electronics, including using Fritzing, so apologizes in advance for that.

I'm attempting a fairly basic 5VDC circuit where I want to use a thermistor to toggle a fan on and off, and to be able to set the point at which the fan toggles.

I know I could use Arduino to read the resistance from the thermistor and the potentiometer and, based on logic, supply high or low to the relay switch - but how would I build the circuit without an Arduino? Would I still need to use an IC for the logic?

I was thinking I could potentially use something like an AND/OR gate with the feedback from the thermistor circuit to control the relay ( thus giving the relay either high/low and not a variable voltage ) but the of course the AND/OR gate is going to get the variable voltage which seems wrong to me ( analog feedback to a digital component ) and so I know I'm missing something - a small I/C that can read the analog voltage would seem to be the "right" thing but it also seems like there may be an easier way to do it with such a simple circuit.

Below are the Schematic and Breadboard views from Fritzing. I know they are incomplete, and that the power supply is 6v instead of 5v, but hopefully it will help convey the basic idea.

screen.png http://img199.imageshack.us/img199/5462/ta07.png

screen 1.png http://img843.imageshack.us/img843/5582/q7yq.png


texts: Why does my Sallen-Key 2nd Order High-Pass filter return a square wave? (Beginner question)

texts:
As part of my Electronics 101 course in college, I was instructed to test a Sallen&Key 2nd order high-pass filter.

After designing the circuit, using an online calculator (can't link because I lack reputation), I confirmed the circuit to have the following characteristics (this also shows the values of the different resistors and capacitors I have chosen):

To this circuit, I will be feeding a 2.5V amplitude sine signal at various frequencies, in order to examine the response of the high-pass filter. I will polarize the operational amplifier using +15V and -15V voltages.

In order to test it out, I downloaded an electronic circuit simulator called LTSpice IV, though I've been able to replicate the same result on other software.

This is how my circuit looks when replicated into the software, plus the faulty output below, where the green line is the input signal (sine 2.5V amplitude 200Hz frequency), and the blue line is the output signal. As you can see, the output signal is a square wave that roughly goes around the polarization values of the operational amplifier.

I get roughly the same output signal for all input frequencies. As far as I know, the circuit is correctly set up. I have tried changing the models of the various resistors/capacitors/operational amplifiers, and it doesn't seem to change the end result.

So far, the most promising thing is that if I remove the resistors R3 and R4, and I connect the output directly to the - input of the operational amplifier, the circuit starts working. This changes the circuit to be a Sallen&Key high-pass filter without gain. However, I'm still curious why the version with gain isn't working.

Here are the contents of the .ASC file that is generated by saving the circuit in LTspice IV:

Version 4
SHEET 1 880 680
WIRE 96 -48 48 -48
WIRE 240 -48 176 -48
WIRE 288 -48 240 -48
WIRE 464 -48 368 -48
WIRE 352 144 352 96
WIRE 240 160 240 -48
WIRE 320 160 240 160
WIRE 464 176 464 -48
WIRE 464 176 384 176
WIRE 512 176 464 176
WIRE -32 192 -144 192
WIRE -16 192 -32 192
WIRE 64 192 32 192
WIRE 128 192 64 192
WIRE 144 192 128 192
WIRE 224 192 192 192
WIRE 320 192 224 192
WIRE 224 224 224 192
WIRE 64 256 64 192
WIRE 352 256 352 208
WIRE 64 432 64 336
WIRE 464 432 464 176
WIRE 464 432 64 432
FLAG 224 304 0
FLAG -224 192 0
FLAG 48 -48 0
FLAG 352 16 0
FLAG 352 336 0
SYMBOL voltage -128 192 R90
WINDOW 0 -32 56 VBottom 2
WINDOW 3 32 56 VTop 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName Vin
SYMATTR Value SINE(0 2.5 200)
SYMBOL res 240 320 R180
WINDOW 0 36 76 Left 2
WINDOW 3 36 40 Left 2
SYMATTR InstName R2
SYMATTR Value 31160
SYMBOL cap 192 176 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C2
SYMATTR Value 0.00000001
SYMBOL Opamps\\LT1012 352 112 R0
SYMATTR InstName U1
SYMBOL res 192 -64 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName Ra
SYMATTR Value 9880
SYMBOL res 384 -64 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName Rb
SYMATTR Value 16240
SYMBOL voltage 352 112 R180
WINDOW 0 24 96 Left 2
WINDOW 3 24 16 Left 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName Vcc+
SYMATTR Value 15
SYMBOL voltage 352 240 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName Vcc-
SYMATTR Value -15
SYMBOL res 80 352 R180
WINDOW 0 36 76 Left 2
WINDOW 3 36 40 Left 2
SYMATTR InstName R1
SYMATTR Value 9880
SYMBOL cap 32 176 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C1
SYMATTR Value 0.00000001
TEXT -578 560 Left 2 !.tran 100ms

Hope someone can help me out on this one. I know that it's probably something dead simple but I've spent hours checking and rechecking the setup, and I can't find any resource that I can understand that tells me why my high-pass filter isn't working. Thank you!


texts: Multiple signals over single RJ-45 cable

texts:
I need to set up a Raspberry Pi system with remote storage, but only have access to a single RJ-45 cable. This limitation is so the system may be replaced in the future, without having to change the cable. There is the need to establish an USB connection, along with a supply line of 5V capable of handling a maximum of 2A. The system topology is presented in the image bellow.

The question is if the use of a single RJ-45 cable for all the signals may result in data loss/interferance on the USB link.

Furthermore, I would like to know if it is possible to suppress one of the supply pairs, by sharing the same line, as show bellow.


texts:
I'm making a protoboard that will include three small sections of wire, around an inch long each, to go:

power source -> relay -> out

power source -> out

When the relay is on the wires will be carrying 12v 1.8amps

How can I determine the correct wire to use?

I've taken a look at the question Choosing the right type of wire? but didn't find info that helped my situation.


texts: Applying KCL to RC circuit and then solving DE for voltage

texts:
When you derive the voltage equation for an RC circuit using KCL, they normally show both resistor current $i_r$ and capacitor current $i_c$ as leaving the same node.  In reality the current is getting sourced from the discharging capacitor and flows in one direction.

However, when I use the later case I get exponential growth instead of exponential decay when i solve the DE for voltage.  Why is that?

Case 1:

$$i_c + i_r = 0$$

$$C\frac{dV}{dt} + \frac{V}{R} = 0$$

$$v~dv = -\frac{1}{RC}~dt$$

$$\int \limits_{v(0)}^{v(t)} \frac{1}{v} ~dv = -\frac{1}{RC}~\int \limits_{0}^{t}d\tau$$

$$ln(v_1/v_0) = \frac{-1}{RC}(t - 0)$$

$$v(t) = v(0)e^{-t/(RC)}$$

exponential delay. good.

Case 2:

$$i_c - i_r = 0$$

$$C\frac{dV}{dt} - \frac{V}{R} = 0$$

$$v~dv = \frac{1}{RC}~dt$$

$$\int \limits_{v(0)}^{v(t)} \frac{1}{v}~dv = \frac{1}{RC}~\int \limits_{0}^{t}d\tau$$

$$ln(v_1/v_0) = \frac{1}{RC}(t - 0)$$

$$v(t) = v(0)e^{t/(RC)}$$

??Exponential growth??  bad.

I remember in school many years ago they said you can assign the current arrows anyway you want, its just the sign comes out minus if you assign the direction wrong, and it corrects itself.

I'm wondering how to make case 2 have exponential delay, the same as case 1.


texts: Equipment required to measure audio line-out voltage peak-to-peak?

texts:
I want to measure the output voltage coming from the line-out of my tape recorder such that the output is 5 to 6 volts peak-to-peak by adjusting the volume control.
I am new to electronics. Can this be done with a basic multimeter or will I need an oscilloscope to view the waveform?
I am trying to follow a guide on loading a program stored on cassette tape onto an old 8-bit microcomputer and this is the recommended setting.


texts:
I bought the Arduino starter kit and in the project book they say that the pin 13 led is an actuator. I thought actuators were a type of motor.

It says:

  "Pin 13 LED. The only actuator build-in to your Arduino Uno. Besides being a handy target for your first blink sketch, this LED is very useful for debugging."

Why is this?


texts:
my goal is to create circuit which would be able to trigger one of 3 +12v relays (only 1 relay could be active at once). Thinking to use 3 switches and mux41 with demux to send encoded signal through 1 wire.

If i'm right, by default output is first input value, if control wires AB(s1.s0) = 01, then output has 2nd input value? So to get AB=01 (s1,s0) I would need to give 0volts to A pin and +12 to the B pin? 0 = no voltage, 1 = voltage if im correct?

Im not gonna be using arduino or rpi.


texts: STM32F103: Can a timer can interfere with uart?

texts:
I have a simple program, which receives data from UART interface and drives a  WS2812b led strip. So, I'm using USART3 to receive data (in IRQ mode) and T3C2 (timer 3, channel 2) to drive LEDs. Here is the code:

https://hastebin.com/rucumovero.cpp

If I use the uart interface without enabling a timer, everything works just perfect, but when I enable the timer I start losing data. For example, here the log if I send 5 similar 32 byte packets [0x41..0x60]

read 29 byte(s): 41 42 43 44 45 46 47 48 49 4A 4B 4C 4D 4E 4F 52 53 54 55 56 57 58 59 5A 5B 5C 5D 5E 5F
read 29 byte(s): 41 42 43 44 45 46 47 48 49 4A 4B 4C 4D 4E 51 52 53 54 55 56 57 58 59 5A 5B 5C 5D 5E 60
read 28 byte(s): 41 42 43 44 45 46 47 48 49 4A 4D 4E 4F 50 51 52 53 54 55 56 57 58 59 5A 5D 5E 5F 60
read 29 byte(s): 41 42 43 44 45 46 47 48 4B 4C 4D 4E 4F 50 51 52 53 54 55 56 57 58 5A 5B 5C 5D 5E 5F 60

every time 3~4 bytes are lost.

I tried to use different baud rate, different usart port - the result is the same. The timer interval is set in line 142:

timer_set_period(TIM3, WSP);

where

#define TICK_NS (1000/72)
#define WSP (1300 / TICK_NS)

If I comment out this line, the problem will disappear, but, of course, I won't be able to drive LEDs without it.

So, it looks like I can't drive WS2812b leds and receive data from UART at the same time. Is it supposed to behave like this? Any idea how can I fix it?


texts: OFDM symbol period and minimum burst durations

texts:
I have been reading about cognitive radio using OFDM and literature on technologies like LTE and 802.11 variants. A useful value in the system analysis is the OFDM symbol period \$T_u\$.

Is it always a minimum number of OFDM symbols that are transmitted in a single burst, or is it a function of something else?

For example, the symbol duration of 802.11a would be \$3.2\mu s\$ and that of 802.11af would be \$22.5\mu s\$ for 8MHz bandwidth operation link. However, the Phy layer PPDU of 802.11af has a frame part length of at least \$225\mu s\$ link. LTE FDD will have a burst of at least one slot (6 or 7 OFDM symbols).

Then, in the actual transmitter of the device, is this always taken as a single chunk and transmitted in burst, or does the transmitter queue up parts and send them according to some link scheduling policy in the random access methods like 802.11?

What I am aiming at is whether a granularity of single OFDM symbol transmission/reception is viable or not for communication? (Assuming LTE like infrastructured networks)


texts:
Using the datasheet UC3842 PWM Controller I have modelled error amplifier in it.

AC analysis of error amplifier matches with the datasheet plot(Figure 3)

 - Since I need to clamp the output voltages(transient) of the error amplifier (COMP) I had placed higher and lower clamps but unfortunately my Aol and behavior of gain and phase change.
 - Clamps are needed during transient behavior

 - Is there any better way to model the error amplifier which I can match both bode plot Aol and transient behavior of the amplifier in PSpice.


texts:
This may look notoriously trivial to ask.
we can see the direction of electron flow as indicated in the picture.
the down side of the arrow must be the positive side of the voltage drop in each resistor, so two positive voltages + v_be=0 it implies v_be is a negative (-0.7 approx.). but in every book it's written that v_be=0.7 volts, is not it incorrect? or they are just talking about the absolute value of v_be?
as indicated in answer section, it is just a matter of convention. now let us see a second picture :
a simple voltage divider JFET. Assuming these authors are following the same conventional current rules in all other circuits, here, the Gate-source voltage should be positive, as just like v_be, but this time it is negative. why?


texts:
In a previous question I posted to the exchange I asked for some instructions on trying to variable speed control a motor. Someone suggested utilizing PWM from my Arduino to open and close a Darlington pair to control speed. I wired it up and ended up frying my darlington pair. I am afraid that I screwed up something with the flyback diode... I am not certain. I am not sure where to trouble shoot what I did wrong. The transistors and flyback diode were very hot to the touch.

What kind of ratings and type of diode should I look for when looking to eliminate flyback voltage from a 18 VDC, 1.5 motor? How would I wire this correctly when using PWM from an Arduino to control a transistor pair?

I am a very new hobbyist and am having trouble wrapping my head around this issue.


texts:
I am using ST's FOC library 4.3. I am able to run my NovoMotec motor as I want, with the Observer + PLL configuration. Often (1 out of 5) during the start -up period, my motor stops, and I get a start-up failure error. I can not solve this problem, so that my motor would start all time (5 out of 5). I dont know, which parameter should I tune:

Speed regulators ( they seem fine, once the motor started)
Start-up parameters. ( These should be tuned maybe. )
I thought that since it is a low inductance motor,maybe it should be started so.
Drive parameters ( since the motor runs, i dont think it's the problem)

Here are pictures of the wb Start-up parameters:

And the motor parameters:


texts: PIC Assembler Bitwise Operator Left Shift

texts:
I am following a tutorial on programming baseline 12F series PICs in assembler.

I have a question regarding bitwise operators specifically the << left shift operator.

Lets use an example the PIC I'm using is a 12F509 so if I wanted to set GP1 and GP0 as outputs and the rest of the I/O pins as inputs I would normally do it like this.

movlw    b'111100' ; Set GP1 and GP0 as outputs
tris     GPIO

If I wanted to use a bitwise operator to achieve the same thing I think I could use << left shift like this.

movlw    0<<1 ; Shift 0 left once to set GP1 and GP0 as outputs
tris     GPIO

I take it after this operation the last 2 bits would be 00. Since << left shift shifts all the bits to the left discards the leftmost bit and sets the bit to the right to 0.

This is my understanding of how the bit shift left operator works. Hopefully it's correct.

Now in the tutorial this bit of code was introduced there was an explanation of what it does but not how it does it.

movlw    ~(1<<1) ; set GP1 as an output
tris     GPIO

I'm going to take a stab at what this code is doing let me know if I've got it right. It's first shifting a binary 1 left once into the GP1 position which leaves a 0 in the GP0 position.

So when the operation in the parenthesis is complete the value would look like this 000010.

Then the ~ is inverting the 1 in the GP1 position to 0 and the 0 in all of the other positions to 1? Leaving the value set to 111101 (GP1 as an output)?

Thanks In Advance.


texts: Off-board SPI communication issue with ADC128S052

texts:
I seem to be having trouble with my board when it is not powered. I have a TI ADC128S02 (datasheet) acting as a slave and communicating with another master board via SPI. There are buffers on the digital lines (Fairchild 74AC541MTC) between the master board and the slave.

My issue is that the master board could potentially be powered without the slave and the ADC being powered. If the master board is powered and sending SPI signals to the unpowered ADC128 then it will damage the ADC's ESD protection circuitry and no longer work correctly.

I'm looking for a way to ground the SPI lines on the slave board when the slave board isn't powered. Once the board is powered the SPI will be operating at 1MHz 5V CMOS logic.

The power analogue and digital power supplies to the ADC need to be isolated and are from different sources, this is to ensure no performance degradation. At the moment when the board is powered off but the SPI is still on this causes V_A = 0.8V and V_D = 1.8V. The datasheet for the ADC states that V_D < (V_A + 0.3V), because this limit is exceeded the device is then damaged.

I was hoping that when the buffer isn't powered the SPI signal wouldn't be seen on the ADC but this is not the case. I thought about using transistor inverters on the SPI lines but I'm worried these will cause signal delays and unnecessary increase in current consumption.

A reduced version of the schematic is included below.

The analogue circuitry of the ADC is powered by ARef. The digital side and the buffer are powered by a seperate 5V. The SPI_MISO line is an output from the ADC to the SPI master and is therefore reversed on the buffer. The other three SPI lines are all from the SPI master. None of the ADC inputs have been shown, nor the rest of the connections on the connector.

Any suggestions as to how I can ground the SPI lines when there is no power on the slave board would be greatly appreciated.


texts: Customized Digital Clock(two power sources)

texts:
I am quite newbie in electronics. Recently I bought a Digital Alarm clock and tried to customize it by adding DC motor wheels . Idea is to set an alarm , when its alarm time apart from sound it should also power few LED's and a DC motors so that it wanders in the room.

Blue and black with header "BUZZ" are powered when its time for alarm.
I have attached few LED's to "Blue" and "black" wires of buzzer and found it to be glowing during alarm time.But the problem is with DC motors.

I have analysed that total power supply to Digital clock 3 v, power sent to buzzer is 1v. Thus it could power LED but not DC motor of 3V.

Any solution to this problem?

I got one solution but don't know how to make it work.I will use a separate 3v battery for DC motor and I need a "AND" condition in a way so that it should power the motor only when there is a current flow from BLUE wire(buzzer).

Is this AND condition possible ??

Thanks


texts: I want to reprograme my wirelss mouse so that it shall generate a nudge if it is on and inactive for 30s, is this possible?

texts:
My problem is that my work computer locks up if there is no activity for only a few minutes. One simple solution is to buy a wireless mouse (or even a wired mouse) that automatically sends a small nudge signal the PC every 30s if the mouse has not been moved for that much time. However, I can't find mouse with such capability built in. I don't know if I can reverse engineer my mouse and reprogram it to do this.

Please let me know if a mouse of this nature (not an expensive USB dongle) exists with this function. And, if it is possible to reverse engineer the code and reprogram the mouse. I have an ET X-08 gaming mouse.

Thanks.

EDIT:
I should have used the term "locked" instead of "locks up". Basically the computer goes back to the log-in screen and requires me the enter the very long password again.


texts: How to know if a flyback converter is working in CCM or DCM

texts:
I m studying a flyback converter. The flyback converter is already made. I m just trying to understand how it works. I m actually focusing on the flyback transformer. And in order to better understand how it is designed I need to know if it is working in Continuous Current Mode or in Discontinuous Current Mode. It is a flyback transformer with fractionnal turns. Here is the formula that I used for knowing if it working in CCM or DCM, the formula is not the best ... It is obtained by doing the approximation that the the transformer is ideal... If you have a better formula it would be really nice to hear it !

In the above formula I know each of the parameters, except Vs which is the output voltage of a transformer with one input and one output. Ve is the rectified input from a RMS 230V.

My transformer has several outputs. How can I know Vs ? What I have done : I estimated the power and the current of each output. Then I sum all of this for having the total output power and the total output current for having the "average" output voltage. What do you think about this method ? Do you have any advice ?

The result is a current which is very low (about 30 mA) where as the ouput power is about 40 W and the total current drawn is around 2A5. The primary inductance is about 1.5 mH. The frequency is around 75 KHz. I am relatively surprised that the limit between CCM and DCM is so low ...

Here is what I called a fractionnal transformer (the windings are fractionned in several outputs) (This is not the transformer that I m studying) :

Thank you very much :)


texts: DFT: Designing a Schematic / PCB to allow measuring resistor values

texts:
Is there a standard method of schematic design to allow measuring individual resistor values on a PCB? Useful for general debugging, validating a new PCB shop, etc.

Because, if part of your circuit looks something like this:

simulate this circuit – Schematic created using CircuitLab

And you try to measure R1 on the PCB with a DMM, you are actually measuring R1 in parallel with (R2 + R3 + (R6 + R5 + R4 || R9 + R8 + R7)). You could remove the resistor from the PCB, measure, and resolder but this is time-intensive and not scaleable.

My 2 ideas:

Add a removable jumper on each branch; maybe applicable on a small scale, not so much on a large scale, so the resulting circuit looks like:

simulate this circuit

Now by disconnecting JMP123, you can measure R1, R2 or R3... Disconnect JMP456 for R4, R5, R6 etc.

Add a sense resistor in line, perform calculations on live circuit using voltage measurements:

simulate this circuit

If, somehow, you are able to know with certainty the resistance of RS123, RS456, RS789, you can measure the voltage across them, divide by their resistance to get the individual branch current, then measure the voltage across your desired resistor and divide by the current... However this assumes you know + trust the values given for the sense resistors (RS***)... Alternatively, you could carefully design the pcb trace for a given resistance and measure those 2 points to act as the sense resistor instead.

Interested to see others ideas for accomplishing this.

Related, tangentially: How to measure resistance of resistor in PCB?


texts:
I have a big battery (11.1V, 10c, 1300mAh), a load of about 0.319 Ohms, and a TIP120 transistor. Now I've heard about the wonders of the TIP120 before (and complaints too) on various Arduino forums. I'm not very knowledgeable in EE, as I've been mostly focused on low-level physics & math, but from looking at the datasheet, I don't believe the TIP120 is capable of being a switching mechanism here. In fact, I feel like it may melt and/or burst into flames if I tried it.

Is my intuition correct here? (Will it blow out the TIP120 if I use it as a switch in this situation?)


texts:
I'm looking into developing a device that will be installed in a PCIe slot but not communicate with the CPU. It will be a standalone device using either the 3v3 or 12v supplies at fairly low current(~150mA).

Does the PCIe 1x slot provide any power when the system is shutdown?


texts: 3 phase AC motor speed control using inverter drive

texts:
as per the subject i had taken a small project of re-modification of a production machine called (Flanging machine) especially used for the cutting and bending of buffle type sheet.

know the motor rating is 3 phase 380V 7.5KW star connected .
constant speed,
know the re-modification to this motor is as follows;-
1) motor driven speed should be control
is it possible to reduce the speed driven by motor


texts: Optical audio transmitter can't handle speech

texts:
This is a question relating to my project on an optical audio transmitter.

I wired up a very simple device in which I use an audio signal transformer (EI14) to modulate the intensity of a laser beam (a cheap 650nm, 5mW diode) according to the audio output of my phone. The laser is then received by a photo-resistor (G5528 A205) wired up to the microphone socket of my laptop. With this setup I can transmit audio between the two devices.

I then upgraded the setup, replacing the photo resistor with a photo transistor in order to improve the response time to the change in the intensity of light (12us rather than 20ms).

The quality has improved significantly; it's still not great and I never expected it to be as there's much to improve. But there is one particularly baffling property of this setup. It transmits audio just fine, but it can't handle speech. Not that it transmits it badly, it's more that it doesn't transmit it at all. In this recording, the audio is captured but the vocal that should be in full swing after around 50s is just not there. If you listen really carefully and know what to look out for, there is the slightest of remnants of the original vocal.

I thought that it's drowned out by the music and tried recording a voice message and transmitting that instead. Same result - the receiver sees nothing, the received amplitude sketch won't even twitch. Same with an audio book recording.

Any ideas about as to how such discrepancy between music and speech could arise?


texts: Why does an overcompensated oscilloscope probe give spikes higher than the input voltage?

texts:
Does anyone knows why an over compensated probe gives voltage spikes bigger than the maximum voltage of the input signal (or bigger Vpeaks?)
These spikes looks to me like a parasitic inductance but I read that the only reason that the variable capacitor is placed on a probe is to compensate the 9Mohm resistor which creates a low pass filter with the input capacitance of the oscilloscope.
These spikes look like a voltage that comes from a resonance frequency between the capacitors and maybe the parasitic inductance which is formed through the probe's cable.
If the probe is under compensated then we have low pass filter which cuts the high frequencies so why there is a ramp shape at the transitions of the signal?


texts: ModelSim VHDL - Nested 'for' loops behaviour

texts:
I've now been a couple years working with VHDL in college and I've been using ModelSim to simulate my designs. Today, however, I noticed something I couldn't understand about for loops, so I thought I'd ask it here :)

When using two nested for loops with the same variable, such us:

for i in 0 to 9 loop
  for i in 0 to 7 loop
    mySignalVector(i)<=myOtherSignal;
  end loop
report integer'image(i);
end loop

This works perfectly, repeating the "father" loop 10 times (and therefore preserving the i value, so the reported messages are values from 0 to 10). I don't understand this, as it should replace the value for the ones in the nested for loop.

So the question is, how do for loops work in VHDL Testbench to produce this behaviour?

Thanks!


texts: why is \$|V_C|=90\$, not \$70\$? series RLC circuit

texts:
If \$|V_S|=100V\$,\$|V_R|=60V\$,and \$|V_L|=10V\$,then what is \$|V_C|\$ ?

simulate this circuit – Schematic created using CircuitLab

My solution

\$100=\sqrt{60^2+(10-V_C)^2}\$,so \$(10-V_C)^2=80^2\$,so \$(10-V_C)=80\$,now we can know\$V_C=10-80=-70V\$,so \$|V_C|=70\$

However ,the book tells me the answer is \$|V_C|=90\$ ,indeed if i replace
\$|V_C|\$ with \$90\$ into \$(10-V_C)^2=80^2\$,the formula does hold,so i want to ask why is \$|V_C|=90\$,not \$70\$,what is the mistake about my calculation?


texts: Why aren't the points to the left and right of \$R_1\$ and \$R_2\$, respectively, nodes?

texts: What I don't get is by the definition of a node -- a point where two or more circuit elements join -- it appears that the dots to the left and right of \$R_1\$ and \$R_2\$ are nodes; both of those points join the dependent voltage source with a resistor, as I understand it.


texts:
I'm trying to build an adjustable active filter for an audio mixer and stumbled upon this design.

I'm completely lost. I understand first order passive filters and Sallen Key's.


texts:
Updated to have organized schematic below, as was suggested. Keeping the original in case of..

simulate this circuit – Schematic created using CircuitLab

I am trying to build a chargepump, where I want to use the second capacitor with doubled voltage as the power supply, detached from Vin.

The first capacitor will have a small capacity, the second will be larger.

Above is my current sketch (forgive me for the shoddy quality, it used to be worse..). I have added two diodes and two transistors. The transistors fire alternating. The capacitors charge, but where the first one is 3v (Vin is 3.3) and the second is a little below that, but not 6v as I would assume.

I have not added a way yet to drain the second capacitor.

I have also tried with optocoupler and was also unsuccessful, but that may be due to other reasons..

I was succesful building the chargepump with an Arduino found here: https://sites.google.com/site/wayneholder/12-volt-charge-pump
However I'm looking to use a 12V or higher Vin with high current.


texts:
I'm planning to make a circuit that lets me switch my keyboard and mouse between 2 computers.
this shows me how to do it.
https://hackaday.com/2016/11/12/diy-kvm-switch-lets-you-use-one-keyboard-and-mouse-with-multiple-computers/

but people were saying it not a good idea to have USB power going back into another pc.
I think I was read you can use a diode. I don't know what cables the diodes need to be connected to.
ty for reading.
this will all so be my first time doing this type of stuff.

any suggestions on changing anything I'm all ears :p.


texts: What's the best way to analyse this potential divider circuit?

texts:
From Andre LaMothe's course on Udemy, I'm trying to figure out how I can ascertain the voltage drops across node 1-2 and node 2-3.
I came up with 2 equations but they aren't enough to solve the problem for me as there are 3 unknowns.
Voltage across node 1-2 is V1, and node 2-3 is V2. Total current is I.
(1) 12 = V1 + V2
and
(2) I = V1/24 + V2/17 + (50*10^-3)
Any help on the thought process for working through this one?

Edit: I just noticed my mistake. Equation (2) is incorrect. Total current I is just the same as V1/24. I.e. current going in to node 2 is the same as current going out of node 2. So eqn 2 becomes the following.
V1/24 = V2/17 + (50*10^-3)
Only 2 unknowns, so can be solved.


texts:
I've recently graduated university with an MEng degree in Electrical and Electronic Engineering. As a third year project, I've used an ST-Microelectronics ARM Cortex-M4 based Nucleo microcontroller board as the basis of a programmable guitar pedal.

I would like to begin designing my own pedals as a hobby, starting with digital effects. To do this, I'm putting together my own 'evaluation' board for prototyping with the following core components:

ADC
Anti-aliasing filter
Microcontroller
Memory
DAC
Re-construction filter
Peripherals (jack connectors, buttons, toggle switches, I2C display etc.)

I would like to keep my designs professional and relatively low cost
(below £100 to prototype).

To produce a device of high quality, I've thought about the following specification:

Sample Rate: 96kHz

This allows maximum frequency of 48kHz to be captured. As the upper limit of human hearing is around 20kHz, this should provide oversampling for greater fidelity.

This also sets the requirements for pre/post filtering, a higher frequency sample rate will also result in simpler filter design.
ADC / DAC Bit depth: 24-bit

Greater bit depth will allow for higher quality (16-bit produces 96dB dynamic range, whereas 24-bit provides 144dB). As there was not much difference in price using an external DAC will increase the dynamic range over the MCU internal DAC / ADC.
Memory requirements 512kB SRAM:

At 96kHz / 24-bit, 1 second of audio requires 96 * 1000 * (24/8) = 288kB therefore 512kB should be suitable, if memory for delay style effects is needed.

As I'm relatively new to this field, I wanted to ask what Microprocessors, ADCs, DACs, Memory would be recommended and does my design approach seem suitable?

So far I've selected the following:

MCU: DSPIC33FJ32GP202-I/SP
ADC: NXP UDA1361TS/N1
DAC: NXP UDA1334ATS/N2
MEMORY: AS6C4008-55PIN

Any advice appreciated.


texts: P-channel MOSFET as high-side switch gets hot

texts:
So I'm trying to control my front lights of my car using an Arduino Nano. In total there are 14 lights (including foglights and blinkers etc.). I'm using two 75HC595 shift registers to control these lights. In my car I also have 14 LEDs so I can see which lights are on. To switch the lights I wanted to use MOSFETs, but because all the lights have a common ground I must use them as a high side switch -> P-channel. I'm using the IRF4905. The lights I'm switching are 55W. At 12V the current thats flowing is around 5A, which should not be a problem, right? The problem is that the MOSFET gets really hot after a short amount of time.

This is the circuit I used to switch one light (all lights would be a huge picture). Transistor is BC547C. Relay is the standard one in my car. Couldn't find lightbulb in Fritzing so I used a Resistor (R6 is lightbulb). The value of R6 is not correct

When the light is on there is about 11.52V across the (+) terminal of the battery and negative side of the light, but there is 10.85V across the light itself. So am I correct if I say there is 0.67V across the MOSFET? I measured the current and it was about 2.58A.

\$0.67V \cdot 2.58A = 1.7W\$ at the MOSFET

\${{0.67V}\over{2.58A}} = 0.26\Omega\$ while \$R_{dson} = 0.02\Omega\$

If I'm doing something wrong in my calculations please tell me.
Is there something wrong with my circuit or do I have a faulty batch of MOSFETs (tried 3 different)?

Edit:
I've already tried to remove the 74HC595 in the circuit but it's still running hot.


texts: How to limit maximum voltage when it's 0.1V too high and the device controller complains?

texts:
I built a retrofit Li-Ion battery pack for a scooter that originally ran on two 12V SLA batteries in series. I measured the voltage of the original SLA charger during the CV phase and it measured 29.3V. Therefore, I built a 7S4P pack, considering that its 29.4V charge voltage is only 0.1V higher.

The problem is that after the Li-Ion is fully charged, when I turn the scooter on, it emits a beep error code which corresponds to "voltage error" in the manual. I measured the battery voltage and it was 29.35V.

The thing is, this is so close to the operating range of the scooter. In fact, if I power on the scooter and QUICKLY start moving, the motor will kick in before the voltage warning happens and I can move around just fine (the load pulls the voltage down just enough), and if I then keep moving for a little while to get that top of the voltage off the batteries and they drop to around 29.3V, then everything is fine. (If I stop too soon, the voltage shoots back up to 29.35, and the voltage alarm goes off and the scooter disables.) It appears the motor controller has a particularly sensitive upper voltage range, since the SLA batteries do read around 29.3V after a full charge, but the 29.35V is enough to cause it to decide the voltage is out of range.

I've considered these options, but I'm at a loss for which option would be easiest to implement, would be the safest with the least amount of inefficiency losses, or just what would even practically work at all.

Put a resistor in series with the battery's terminals so that at full state of charge it only outputs 29.3V, with 0.1V being absorbed by the resistor. Some of the resistors used for current shunting might work. The problem with this is, since the scooter uses the same leads for charging and discharging, this seems like it'd affect charging,  since the charger would not detect the 29.4V it expects at end of charge and will drive the batteries into overcharge (very bad).
Limit the charging voltage to 29.3V. A resistor in series would have the same problem as #1 with the charger detecting end of charge. Using a bench supply would work, but this is inconvenient at best, and I haven't found any good Li-Ion chargers that offer this variability in charge voltage. Also, limiting charge to 29.3V might result in some capacity loss - I'm not sure what batteries do if you switch to CC at a lower voltage than the typical maximum voltage, if you continue charging at a lower voltage with lowering current, does the battery's voltage jump up to 29.4V anyway?
Somehow modify the scooter controller. This is probably the worst option since it would required all sorts of stuff (figuring out how to program the controller, etc.) that is probably too much effort for all of this.

It's particularly annoying that the scooter controller is the thing limiting this upgrade. I know that SLA batteries can actually be charged up to 2.5V (especially in lower temperatures) so putting such a strict top limit on voltage seems a little "overcautious".

What should I do?


texts: Can someone verify the hole diameter is correct?

texts:
I'm looking at this current sensor (datasheet)

I'm a little confused at this notation for hole size.

Pin 5 and 6 have a diameter of 0.6mm while pin 1, 2, 3, 4 have a diameter of 0.25mm ? Is that correct ?

If someone could also explain what this format is "4-0.25x0.5". I've never seen this type of notation before.

Thanks!

edit

I think it could be 0.25mm x 0.5mm (length x width) since the pins look more rectangular vs circular for pins [1,4].


texts:
I am trying to read datasheets of mixers...

For the plots in datasheets, for example Conversion Loss/Gain vs frequency, is that frequency RF or LO?

Analog Devices labels the x-axis as RF frequency clearly
(http://www.analog.com/media/en/technical-documentation/data-sheets/admv1012.pdf),

but some datasheet don't label anything
(http://www.skyworksinc.com/uploads/documents/201017D.pdf)

Can I assume that the x-axis-frequency always refers to RF frequency? Is there any case that LC vs LO frequency is important?


texts: Why isn't RMS called SMR, when it's (linguistically) a square mean root?

texts:
This question falls into the funfact category, but I'm anticipating this question from my next course students and I'd like to have the answer, if there is any. In the spirit of English language, RMS is actually the waveform square mean root. However, the abbreviation RMS stands for root of the mean of the square of the waveform. Is there any answer as to why this form is chosen? I haven't been able to find it on Google.

Similar trivia can be found on Wikipedia for lambda expressions. When asked why lambda, Alonzo Church answered "eeny, meeny, miny, moe". Unfortunately, no trivia for RMS.


texts: How to interface PWM output from a microcontroller with power MOSFET?

texts:
How to interface PWM output from a dsPIC30F6012 microcontroller with power MOSFET TrenchFET like SiE818DF? I want use PWM to control the brightness of the LEDs. Four PWM channels, one PWM per channel.

PWM frequency 244Hz
LED Voltage: 12V
Total operating current: 5A
1W LEDs with working current 350mA (4 banks of LED's)
Overcurrent protection on output of each channel.

Can TrenchFET be connected directly, or some matching IC circuits need be used?


texts:
I have a high voltage system (~5kV) to generate pulsed spark. I was able to detect the spark ignition. It has been shown in the images by the yellow line. This signal will be used to generate another signal with desired width (blue signal). The blue signal eventually will be sent to an instrument to turn the instrument on. The instrument expects a rising edge signal. But as it can be seen, there is a bump at the beginning of the blue signal, which causes error in triggering the instrument. I have been trying to use comparator, ferrite beads and schmitt trigger to reduce that bump. The images are after all the efforts. Can anyone direct me to smooth the initial bump on the blue signal?

Thank you.


texts: What role is this Matched PNP Transistor and MOSFET pair playing in this circuit?

texts:
I'm trying to understand what exactly this power circuit is doing. The schematic below shows 5V in from USB. It is run through a fuse, and then there's some tricky PNP transistor stuff happening I can't sort out with the DMMT5401. I don't understand the interaction it is having with the P-channel MOSFET DMG2305UX.

Since its a ptype MOSFET, then I think the DMMT is cutting off the flow of 5V using C2 under a certain circumstance. I don't know what circumstances can be derived from E1 (the 5V in) and E2 (the 5V destination) though.

Associated datasheets are shared here:
https://drive.google.com/open?id=0B_rZRctloOItU2VFMkx6RHdFSmc

Schematic here:

The 5V eventually runs out to a DC/DC converter PAM2306AYPKE which provides 1V8 and 3V3 to a device.

What I don't understand is the role of the Transistor and MOSFET in the first place. Why not just use the 5V from the fuse? Secondly, since is does exist, how does the transistor work together with the MOSFET?

(My question may derive from a hard time understanding P type devices, and the fact that this is a paired transistor, and it's modulating the performance of yet another P type device.)


texts: Advice needed for a switch controlling 3 switch states at once?

texts:
Above are three switches for an electronic system to operate.
SSR is a sold state relay, and L indicates the hot line for 230VAC which is powering a circuit. Switch 1 is connected to a wire in the circuit.

I need a single-throw switch when ON: switch 1 and switch 2 will be ON and switch 3 will be OFF.
And similarly when OFF: switch 1 and switch 2 will be OFF and switch 3 will be ON.

Is there any type of switch where I can achieve this goal?

edit: States of switches will change as: ON ON OFF ----> OFF OFF ON


texts: Some questions about the emitter resistor added to the fixed bias circuit

texts:
In many texts it is mentioned that the emitter resistor stabilizes the bias circuit. For example particularly for the below example:

Which quantity is aimed to be stabilized initially? Vbe?

And how does adding Re archives this? Can you give an example scenario so we can see that how Re works?


texts:
I have bud earphones, through which I am listening to music.
Air pressure in my ear (after inserting the earphones) is presumably slightly higher than the pressure of the surrounding air outside of my ears.
Based on that observation, is it hypothetically possible to detect (eg. via resistance of the earphones) whether they are in my ears or not? (Assuming there's some sound being played through them.) If so, what would need to be measured / what measuring devices would be needed?

I'm not asking for a interface-specific solution eg. for 3.5mm jack earphones, I'm just curious as to whether there is such possibility in general (for some/any interface).


texts:
I have an OLED display and a high gain op-amp on the same circuit. When OLED is powered on and displaying something, it creates a electrical noise on the output of the opamp. Here is what I tried:

Opamp and OLED power lines are decoupled with closely-positioned 100nf ceramic caps.
The display is mounted directly behind of the said opamp. To determine if noise is not caused by radiated EMI by the display itself, I connected the display away from the PCB by running a wire. No change.
Added an LC filter to op-amp supply (ferrite bead and 100n+10u after). No change.
If I supply the OLED with a seperate power supply, the problem goes away (output looks same as if OLED disconnected).

Here is a scope capture. Please ignore the rising/falling edges.

The OLED driver internally generates ~9V for driving the display. It uses a capacitance multiplier for that and probably that's my problem.

Any help/idea on filtering this supply noise would be appreciated.

Edit 1:

Current draw of the OLED: 10mA@5V
What is opamp doing: It is MCP601 that I'm using as a thermocouple frontend. Output goes to an ADC (no load).
Other noise sources: Circuit is supplied with (clean) 12V, goes through on-board 5V linear regulator (with its input and output caps). Everything (OLED, op-amp and MCU) is on the same supply.
Routing: Two layer PCB with ground pour on each layer. I did not do star grounding though.
Decoupling on OLED: I modded the OLED board with its supply passes through a ferrite+100n, no change.
Ferrite bead: I tried what I have on hand, BLM21PG331SN1D and FBMJ2125HS250NT.


texts: Strategies for mapping an area perimeter with a mobile robot

texts: I'd like to build a bot that when placed in an area would have the ability to find the perimeter of the area and map the obstacles present.  Later it should be able to navigate to different parts of the area on demand (e.g. navigate to the NW corner or continually monitor the entire area or return to a specific point in the area).  What hardware/software would be necessary to make this happen?  I've considered using IR to detect the obstacles & wall but it seems like the resolution may be a bit low for these purposes (could IR recognize an area is just large enough for the bot to fit into?).  What prior work is available on these subjects, what sensors might I consider to get started?


texts: What happened to the open bench logic sniffer?

texts:
Around 2015 the Open Bench Logic Sniffer looked like a really promising logic sniffer/analyzer at a price a hobbyist could tolerate. These were available assembled from Seeed (and others?) There's no sign of it today that I can find. Is there a successor that obsoleted this? Is there a competitively priced commercial offering that is a good substitute?

Not that I really want to build one, but I can't find board layout files (KiCAD or other) or gerbers, even though the project is described as open source. The code files are there, but not schematics and board layout.


texts: Can tranformerless inverter topology be used in UPS with a regular battery (12V 7Ah)?

texts: While searching for transformerless inverters in the IEEE site, most of them seem to be about grid connected Photovoltaic inverters. Removing transformers will increase the efficiency at the cost of galvanic non-isolation between the ac and dc parts which might cause dangerous dc injection currents. Is this why battery inverters do not have transformerless topologies?


texts: CAN Bus Off when operating with two nodes

texts:
I have two nodes A and B operating on a CAN bus. I have cut the bus off and Node A reached the error passive state due to the lack of ack from Node B (because I removed the bus).

What I noticed is that the Node A shall never reach the  bus off state regardless of the fact that the TEC value is constantly increasing.

My question: Is that happening because there is no actually a real bus?


texts: I am trying to solve this circuit and am getting confused by how the input impedance of the base of the transistor is calculated. I am confused how this is done? What are the general rules for figuring out the input impedances when looking into the base, emitter or collector? Do I need to rely on small signal models?


texts: Dave Jones' uCurrent Gold - trace to shunt resistors has no soldermask

texts:
I was going through the uCurrent project and noticed something that seemed unusual to me. In the image, the trace connecting R1 to the input jack is (a) of differing trace widths, and (b) has no solder mask for a small portion.

Does anyone know if there's a reason for a small portion of the trace to be different from the rest? I can't think of an electrical reason, except maybe controlling the trace impedance with a different trace width but that doesn't explain why there's no solder mask. Is the exposed trace meant to help during testing?


texts: Which group do the Proximity sensors belong to?

texts:
I was actually doing some research about motion/gesture sensors. well there are different types of motion sensors like : Passive Infrared (PIR), Area reflection type, Ultrasonic, and etc.

Well, I know that even proximity sensors are widely used as motion sensors. Since it doesn't emit the rays can i consider proximity sensors as PIR sensors?

1. Does it belong to PIR group?

on the other hand, there are some proximity detectors which they combine proximity sensor and the LED.

2. Are these proximity detectors simply behave like Rx/Tx pair sensors?

Thank you!


texts:
Can anyone tell me what this component is?
This is a hall effect ignition pickup on a lawn mower engine (Onan P220).
Thanks


texts: Does the classical 5V <--> 3.3V bidirectional MOSFET interfacing solution exist as a DIP package? Or is the commopn way to place discrete MOSFETs in your circuit? In that case, what are some common low cost through-hole devices that you can recommend for this application? I realize this question has been asked in a few variations already, but I'm looking for practical implementation guidance here.


texts: I was searching for some IC to amplify a signal (like a RF frontend before an antenna) to have a stronger RF signal. I come across 2 terms and I don't really understand the difference between them. What is the difference between a gain block and a power amplifier?


texts:
I have a 7.4V battery supply which will gradually discharge and reduce until at about 5V I won't have enough power for my device anymore.

Ideally, I need to maintain a 7V (+/- 0.5V) supply rail throughout this time so I've been looking at the MC34064A.

I've used this tool to generate the component values I need.

Simulating the design in Proteus off the 7.4V supply gives me 6.8V with about 100mV of ripple. However, if I then try and run it off 5V this drops dramatically.

So either I've designed my schematic wrong or I'm misunderstanding the function of this IC. Either way could you please advise on how I can obtain a steady 7V rail from a supply that varies from 7.4V to 5V?


texts: As we know that in steady state capacitor acts as OC and inductor acts as SC. But in steady state AC we deal with term like jXL or -jXC and uses phasor and other stuffs to determine circuit parameters like current and voltage. How it can happen when already all the values impedance values are either zero(in inductor) and infinite(in capacitor) ?


texts: 240v ac to 12v dc transformer voltage drop under load

texts:
I have a 12v air pump, on manual it says current is 9A. So I bought this 240ac to 12v dc transformer it has: 12V 150W 12.5A so I thought the transformer can provide enough current.
This is the transformer I bought:
https://www.ebay.com.au/itm/DC-12V-24V-Waterproof-Power-Supply-Transformer-Adapter-LED-Driver-36-250W-/371937953390

But when I plug the air pump to the output of the transformer, the voltage dropps to 3.6V which the air pump couldn't keep working. This is a video I took:
https://obanau-my.sharepoint.com/:v:/g/personal/todd_liang_obansolutions_com_au/EVljWVMZoytGje_Y-86fKGYBdMTBr3bKtOFa4yBB9FQ9GA?e=YPqaZK

The air pump is working perfectly fine if I use a 12v battery so it has to be the transformer issue, so what could be the reason? Why the voltage dropped so much?

Update: here is the pump

Update2
I also bought a 120W transformer from the same seller and oddly enough the 120W transformer is working perfectly fine, only this 150W (which suppose to be more powerful) doesn't work. I reported this issue to the ebay seller and they sent me a replacement. Today I received the new transformer but it has the same issue.


texts: CMRR test methodology and effect of open loop gain

texts:
I am trying to test the CMRR of opamp and so measuring offset variation across Common mode range in unity gain mode. I have gone through many articles on CMRR measurement. All those are suggesting a differential configuration of Opamp for testing CMRR.

Why shouldnt I test for offset across Vcm in Unity gain mode for CMRR ? In unity gain mode, varying the common mode voltage and measuring the offset as the difference of output and input, CMRR can be measured.

If I have to measure in differential mode, there will be 4 resistors besides opamp. The accuracy of these resistors will effect my measurement across Vcm, Vdd and Temperature.

Someone stated that the infinite open loop gain will effect the offset in unity gain mode across common mode range and give pessimistic values of offset as compared to differential mode. I tried with math to understand the effect of openloop gain on closed loop gain and found that the effect is the same whether it is unity gain or differential mode.

Please help me understand right methodology.


texts: Would splicing existing wires (from charge controller to battery) to connect an inverter work, and is it safe?

texts:
I'm trying to add an inverter in my travel trailer, but wanted to figure out the best way to do it. Because I'm not that familiar with the electrical setup of the trailer, I was only able to access the electrical components of the charge controller; the rest are wired under the trailer somewhere.

I just want to know if it'd be safe to splice the wires going from the charge controller to the batteries, to hook up the inverter. I know that the ideal way to do this is go straight from the battery to the inverter, and not piggy back on any existing wiring; but the wires from the batteries all go under the trailer, and I'm not sure how it's all wired together.

Apologies for the amateur question(s).


texts:
I've seen a lot of answers referring to track widths but nothing that concentrates on copper planes.

I'm designing a 300mm by 300mm PCB that's 1.6mm thick and using 2oz copper weight. Evenly distributed around the board are 110 APA102 RGB LEDs (similar to WS2812B). Their max current draw is around 60mA. So hypothetically with them all on max the current draw is 6.6A @ 5V.

How can I calculate whether the PCB can handle this, and what the temperature rise will be?


texts: Why do we use closed-loop feedback in buck converters?

texts:
My power electronics professor spent most of his life in the time domain and in application-specific theory (SMPS-only vocabulary).

For me, a buck converter is basically a square wave (generated by a switch) passed through an LC filter.

The square wave's fundamental frequency and its harmonics are filtered out, and all that's left is the DC component. I understand that closed-loop feedback is necessary if the Vin changes - because you'll need to increase or decrease your duty cycle since your square wave's amplitude (ergo DC component) has changed. Is that it?

I also understand that the load impedance might affect the corner frequency of the filter. Is that why we need closed loop feedback? How is this issue mitigated?

Which other components of the (supposedly) DC signal does the control loop eliminate? Ripple? (Isn't this just a matter of filter quality?)


texts: how to trigger another clk in mainclk (verilog)

texts:
I wrote somekind of prescaler in verilog to make sclk_adc signal from clk_i.
by now my code looks like:

always @(posedge clk_i)
begin
//generation of sclk_adc
end

now i wonder is there any probability to load shift registers on pos/negedge of generated clock in always @(posedge clk_i) block?

When i wrote this outside the main always block

always @(negedge sclk_adc)
begin
    transdata = transtmp;
    dataInCh[ch_cnt][15:0] = transdata;
end

always @(posedge sclk_adc)
begin
    dout = shiftOut [ch_cnt] [15];
    shiftOut [ch_cnt][15:0] = { shiftOut[ch_cnt] [14:0], 1'b0};
end

It is simulated well in the GTKwave, but quartus started to complain about multiply reference to dout (my output), deservedly, i think.
So it seems like i have to load them in main always block, but when i add those lines there, shift registers start to load with clk_i, not with the sclk_adc what is logical, but how to avoid this?
Please, provide me any clue, thanks


texts:
I've tried searching through existing topics but haven't found an answer.  I'm a beginner enthusiast.  I have a couple of questions that I would appreciate input for.  My plan is to make a battery pack that can be charged via wall adapter/PC/solar.  I have found information here that helped greatly.

1) I plan to use 2x 18650 batteries in parallel as the power supply.  The only ones I can find are rated at either 35A or 40A.  All others I have found do not list the amp value.

2) Through other questions/answers I have been made aware of voltage boost modules.  My concern is that the ones I have been able to find specify a max input of 4A from the battery source.  Will the batteries I mentioned above fry the circuit?  Will I need to make a step down circuit between the batteries and the voltage boost module to decrease the amps or an I just overthinking this?

3) The modules I found have mini USB connectors for charging the batteries.  Can I tap this circuit with a solar panel (with inline diode) to charge the pack instead of a wall adapter or PC?  Will I still be able to use a wall adapter if I do this?  What is the lowest maH value that would provide a reasonable recharge time?  I realize the charge time would increase due to how many batteries are used.

Thank you for taking the time to read this.


texts: Lengthen a AC to microUSB phone charger cord?

texts: Can I effectively take a 3 ft standard cell phone charger (AC to microUSB, 750 mA at 5V) and lengthen the cord to 6 ft by splicing the cord or am I going to lose something in the mix?  Do I need to account for the length of the cord when they are such short lengths?


texts: PLC Replacement with C++ Embedded System or Application Specific Circuit

texts:
I work for a company that uses PLCs in their products, but lately, we have thought about doing away with our PLCs for application-specific circuits, FPGAs, or some other type of system on a chip that can implement all the features on the PLC.

Does anyone know which route would be best to go for modern control systems? It will require PID controllers, closed feedback loops, and ladder realtime logic - or at least very close to real-time logic. We would need to write the software in C/C++.

Also, are there any C++ frameworks or libraries that could support these control systems in a modular way. We have multiple different products with different control requirements - it would be nice to use the same hardware with all the devices and then load the software per specific product. Having a framework would avoid redoing a lot of work.


texts: AH276 hall effect sensor with microcontroller (sensor already in circuit - brushless fan)

texts:
I'm currently trying to read an AH276 hall effect sensor using an AVR microcontroller. The sensor is built-in in a brushless fan I'm using and it's operating as the fan's controller. The sensor has two output pins which drive the four coils of the fan (two pairs). My guess is that, using one of the two output pins (doesn't matter which one), I can count the RPMs of the fan. Is my guess correct?

If yes, how can I read the RPM without using an external sensor? Should I use a transistor on either AH276's output pin or I can connect it directly to an IO pin of the microcontroller? I have figured out the software part, but I'm stuck on hardware.

Both the microcontroller and the fan run at 5V.


texts:
I built this ZVS driver  to make some big high voltage sparks a while ago. It worked off three voltages 24V, 50V, and 80V and had no issues. The only part of it that got really hot were the 1kohm 3W resistors.

Recently I decided to play around with coil guns so i used it to charge up a capacitor bank as show in the picture. The rectifier diodes are just regular 4007's

The problem I'm having is this. When i charge up the capacitors it doesnt make a high pitched whine like it normally does, it (the transformer, which is a ferrite core from an old TV) makes this really awful chattering sound that starts off really rough sounding and eventually turns into the whine as the capacitor fully charges. Seems like a current issue where its drawing more current at the initial stages of charging and less as the voltage in the cap rises. However, it doesnt do this when i simply shortage secondary and that should draw maximum current.
After a few charges, for the first time ever, the MOSFET's were actually really hot and the chattering sound became random and the MOSFET's failed (due to over heating).

So my questions are:

Does any one know what went wrong?
Why is the transformer chattering and how do i make it stop?

I think i should have used UF4007's for the rectifier and I'm wondering if 1Kohm at 24V input is too high and i should go with the typical 470ohm. Maybe the high resistance is allowing the MOSFET's to stay on too long which might cause poor oscillation and cause the chattering?


texts: Terminology for components found in Kitchen Timer

texts:
Apologies if this is a duplicate, by definition I'm not sure what to search for.
I took apart a kitchen timer and found a few things I'd like to learn about, but couldn't find the right terminology to google for.

There are silicone/rubber (?) buttons used to close switches on the circuit. Are these considered membrane / dome switches? If not, what are they called?

these switches connect to the PCB on what look like surface mount circles with a squiggly nonconductive shape between them - what are these called?

The screen is a 7-segment display with 12 connectors, but it isn't soldered to the board, rather it has a soft rubbery connection (pink/black in pic) that conducts when pressed against the connectors - what is this connector/technique called?


texts: Custom Eagle CAD part for Arduino Pro Mino

texts:
I am trying to create a custom part for Arduino Pro Mini in Eagle 7.6.0 Light. The Arduino Pro Mini has pins A4 and A5 not on the edges but in the middle of the board (see image below).

I am trying to figure out what would be the best approach to create the custom part for these pins? I have put them in the center of the symbol when creating the custom part, but when I am in the Schematic view I only see the name of the pin (i.e. A4 or A5) but not sure where to connect (i.e. cant see red pin output).

Schematic View

Part Symbol View

Arduino Pro Mini (A4 and A5 at top center)


texts: How to calculate capacitor's Power Rating?

texts: How to calculate capacitors power rating (in watts)? or is there any ? i am designing a circuit to filter out noise signals i am not sure about power ratings of capacitor(electrolytic) .


texts:
I'm learning a bit about controlled sources and I'm a bit confused about calculating their power.
I have this circuit.

Link to Falstad Simulation
According to the formula for power P = U * I, I get

PR1 = 1.033W
PR2 = 0.318W
PR3 = 0.204W
PRSum = 1.555W

The voltage source is outputting

Psource = -1.607 W

The controlled voltage source output / takes?

Pcv = (+/-)0.051W?

Normally the the sum of all powers equals to 0
But if I assume the controlled voltage source as a power "provider" it just doesn't add up.
So the controlled voltage source has to be a power sink just like a resistor?
Is this assumption right? If yes why?


texts: LC circuit, bigger L than C, or bigger C than L?

texts:
So if I want my LC circuit to resonate at 20MHz, I just use the formula, \$F=\frac{1} {2\pi\sqrt{LC}}\$. Using available inductor and capacitor values, there are lots of different possible combinations. If L is small, C is big or vice-versa. Or they could be about equal.

Will it make any difference at all in the actual operation of the circuit?

Will one way be less efficient and decay faster?


texts: Issues with HUM on DIY audio signal switcher using a relay

texts:
I am creating a rack mounted system for toggling multiple guitar pedal effects remotely through a footswitch. The idea is that I create a signal chain starting with the output of a guitar and that going through a serial chain of eight relay boards and then into the amplifier. Each relay board will be able to add or remove an effect pedal from the signal chain, adding the effect or bypassing it. Something like a much simpler version of a device such as this one: https://www.boss.info/us/products/es-5/

I now have it built and mostly working except that I am getting a constant hum which sounds like some sort of a ground loop noise when I connect everything together. This is even happening if the device is not connected to power and I only connect the signal through the outer two connectors (see board below). I use a Panasonic TQ2-4.5 DPDT Relay for this.

Also I've uploaded the whole project schematics and designs on github and planning to document it much better when I get it working.

https://github.com/darko1002001/remote-guitar-pedal-controller

Here is the schematic of the relay circuit.


texts: Z80 control pins not reading a defined logic level

texts:
I'm having trouble getting my simple Z80 based project to work. I asked for help here last week, and received an excellent response on troubleshooting the Z80; here is the relevant part:

  There could be many reasons for this malfunction, such as a wiring
  error, faulty chip etc. I would start by checking to see if the CPU
  can work by itself. To do that I would:-

  Remove the VIA and EEPROM. Check all wiring for shorts etc, and make
  sure the power supply and bypass capacitors are connected to the
  correct pins.
  Tie all 8 data lines to ground via resistors (~1k each), to create a NOP instruction.
  Power up the circuit and check that all input signals are correct (/INT, /NMI, /HALT, /BUSRQ, /WAIT, /RESET should all be high)

When I do this, only the /HALT pin is high; the other 5 pins don't read as high or low (as checked with a logic tester).

Does this indicate a bad chip, or could it be something else (e.g. I'm not supplying enough current)? Is there a general explanation when a control pin doesn't read as a stable logic level? I know some pins are tri-state; I don't think these are, although the datasheet states that the /INT and /NMI pins need pull-up resistors in normal operation.

Thanks in advance for any replies.


texts: Having trouble soldering headphone wires

texts:
I was fixing my friend’s headphones today and I’m having trouble soldering the tiny wires. I know they have a tiny coating layer that works as an isolation, I have stripped this layer using a gas burner (not sure if that’s the right word, I’m talking about Dremel Versatip, a kind of a lighter on steroids).

There was one wire that wasn’t isolated and the solder sticks to it perfectly, flowing all over the wire and creating a nice top layer. However the other wires don’t seem to like the solder at all, it’s far away from the situation on the first wire. What am I doing wrong?


texts: Signal Switching Advice/Recommendation needed

texts:
I need to design a switching circuits for this:

A tester device is used to test a controller(lets call it controller A). This controller have both input/ouput(analog and digital for each) which is currently tested by the testing machine.

I have to expand functionality of the tester so that controller B can also be tested(not at the same time). Controller B has same number of pin as controller A, but each pin each assigned different channel type(analog in controller A, digital in controller B, vice versa).

So I will have to make separate wiring harness for controller B, and have to switch back and forth every time.

So I decide to use relays to accomplished switching. There are approximately 35 pins with channel type mismatched, I am thinking about using six 6pole-double throw relay which will switched for desired configuration.  I am using this relays http://www.digikey.com/product-detail/en/te-connectivity-potter-brumfield-relays/R10-E1Z6-V430/PB775-ND/813841. My question is given the situation I just described, are there better way(I may have missed) to accomplish this?

Notes:Another issue is pins are group by connector on both DUT and tester side. And signal that needs to be switched are not necessarily in same connector.


texts: What is the difference between Register Addressing mode and Direct Addressing mode(8051)?

texts:
I find that there is no difference between the Register Addressing mode and the Direct Addressing mode.
Can anyone tell the difference with respect to the 8051 microcontroller ?


texts: Multiple infrared LEDs in parallel or series?

texts:
For a bird camera project, I would like to power 4 infrared LEDs from a Raspberry Pi as the light source for the Pi's NoIR camera.
The IR LEDs (TSHF6410) have a forward voltage of 1.4V and a maximum forward current of 100mA.
I came up with two different circuits: one with all 4 LEDs in parallel, and one with two strings of two LEDs in series.

Which circuit would be the best choice?
In the first circuit, with all LEDs in parallel:

LED current: 77mA = (5V - 1.4V) / 47Ω
Transistor current: 308mA = 4 * 77mA

In the second circuit, with all LEDs in parallel:

LED current: 100mA = (5V - 2 * 1.4V) / 22Ω
Transistor current: 200mA = 2 * 100mA

For the LED current, the second circuit is exactly at the maximum rating for the IR LED. Would that be a problem? Do I risk damaging the LED?
For the transistor current, both circuits are within the limits of the 2N5551 transistor (600mA). For the second circuit a 2N3904 transistor (200mA), might work as well - or is this again too close to the limits?
Does the higher current of the first circuit also mean it consumes more power? So in that regard the second circuit would be the best choice? Are there any other advantages/disadvantages?
PS: I'm not sure whether it matters, but I intend to control the brightness of the LEDs via PWM.


texts:
https://www.youtube.com/watch?time_continue=25&v=d3bF2v056WU

http://i.imgur.com/ipDYgd8.png

I'm going to ask about some names. You could say "they are just names" but if I get some context for the names, its going to going to be a good start to clearing some of my other confusions and understanding the intent of the circuit/ checking if my interpretation of the circuit is actually correct

In what sense is the lenient MUX, "lenient"

My understanding of a MUX: Basically its a truth table. The inputs of S tell you what row of the truth table to go to.

So on what sense does adding a feedback for one output to one row of a truth table (am I wrong about we are feeding back to one row of a truth table) make the MUX "lenient" ?

Also I can't seem to find the term "lenient mux" outside the course's materials

What is meant by "load" and "load signal" ?

http://i.imgur.com/ipDYgd8.png

"the select line of the MUX will become the memory component's load signal"

My interpretation of the circuit in the picture is that S will either tell the device to hold onto its current value Q or accept a new one. So my interpretation of S is like its a key that tells locks or unlocks the path to accept a new value.

In what sense are we "loading" and how is S the load signal? We can only store one value Q at a time it seems so it seems we are not loading but setting a value

Why is S controlled by a gate? Whose gate?


texts:
I have a simple 3 motor robot arm. Without much experience or knowledge, I put together a circuit for controlling it. Circuit is below:

Now the circuit actually works and I can program the Arduino and have it move about as I wish. Here are the issues and questions I have:

I have had several motor drive boards "smoke" and then never turn on again. Is this because the motors may have been stalled when I powered on the circuit? I.e. if my motors have a stall current of 20A, do I need a motor driver that can handle 20A? The reason I went with less (13A drivers) is because I was only planning on operating around 10A, which would be the max power operating point. Do I even have control of how much current is drawn?
Is it advisable to use 1 battery like I am doing? I had to strip the other end of the aligator clips, strip the 3 sets of wires, wrap em around, and apply a lot of solder. I have no idea what the "reasonable" thing to do here is, maybe it's to have 3 batteries for all I know.
I am using AWG wire #16, which is supposed to have a max chassis wiring limit of 22A (http://www.powerstream.com/Wire_Size.htm). Should this be alright? I haven't had any wire melting problems.
Any other suggestions are welcome, I am new to this =)

Thanks for the help, and let me know if you need any additional information.


texts: Edge-mount SMA connector for ~100mil board thickness

texts:
I have a footprint on a ~100mil thick PCB for an SMA edge connector:

I find millions of SMA edge connectors for 62mil board thickness and I found a single one for 32mil (https://www.adafruit.com/product/1864).

However, I found none for ~100mil thickness.

Do they exist? And if not, is there any hack to still install an SMA connector reliably? (Frequency range is up to 3 GHz, RL as good as possible but not critical; price secondary).

It is worth to mention that the PCB is already fabricated with the footprint above. That means I cannot change footprints, holes, thickness etc.


texts: Inductance of toroidal-cylindrical inductor?

texts: If the inductance of a solenoid is \$L_{\text{sol}}=\frac{\mu N^2 A}{l}\$ and the inductance of a toroid is \$L_{\text{tor}}=\frac{\mu N^2 r^2}{D}\$, is it correct to assume that the inductance of a "toroidal-cylindrical" inductor is simply  equal to several toroidal inductors connected in series, \$L_{\text{tor-sol}}=N_1\frac{\mu N_2^2 r^2}{D}\$, or the contribution of the "solenoidal effect" is significant? What would be the total inductance then? Does this type of geometry has any practical use?


texts:
I have a 12v battery that is rated at 220ah.
I have solar panels rated at 500 watts total.
I'm using a MPPT charge controller rated for 12/24 volts

I only have a rudimentary understanding of electricity, so please forgive the elementary nature of these question that I hope you can help me work out:

Assuming we start at zero, and ignoring real-world inefficiencies...

If this is a 12v panel and it produces ~41 amps, would it take roughly 5.3 hours to fill up the battery?
If this is a 24v panel it produces ~21 amps, would it take roughly 11 hours to fill up the battery?

That seems counter-intuitive, but if "amps" = "the amount of electricity" I'm getting lost as to why that isn't true.

Is there any difference in usable power generation between 12 and 24 volt panels as long as they are at the same wattage?
Finally, if I have some amount of "amp hours" I'm trying to replace in a battery (let's say I ran that 220ah battery down to 110ah remaining and I want to recharge it), what's the formula for figuring out how many hours of sunlight I would need, if I have X watts worth of solar panels?


texts: 555 Timer in Bistable Mode - Unexpected Behavior When Removing Power

texts:
I have a question regarding a 555 timer (TLC555CP) in bistable mode. Here is the schematic for the circuit in question.

Now, this circuit works as I expect, when I hit the push button attached to the trigger the led goes on and stays on, and then when I hit the push button attached to the reset the led goes off and stays off. The problem that I have is when I disconnect the 555 timer from power.

If I were to open either S1 or S2, and then close it, the 555 timer does not act like it did before. In this situation, when I hit the trigger the led only goes on while the push button is down and goes off when it is up. Therefore the 555 timer does not act as I would expect. Eventually though, I can make it work again by either removing the capacitor, opening and closing S1 or S2, or a combination of both.

My question is, what is happening that I am not understanding in regards to why the 555 timer seems to lose its bistable functionality when it is cut off from power? Is there anything wrong with my circuit that would make this not happen? Thanks.


texts: How to run new .meas commands without having to rerun the whole ltspice simulation?

texts:
I am trying to analyze a circuits properties over a certain range of component values, e.g. a PWM circuit for various settings of the control pot. For this I create a bunch of .meas statements, and graph them.

Now it happens that I am either making mistakes in the .meas commands or am interested in different properties. What I am currently doing is to add more .meas commands and then rerunning the simulation. For multiple stepped parameters in circuits that run at speeds of a few µs/s over many ms, this takes awfully lots of time.

After running a sim, the data is already there, so in theory it should be possible to just run another .meas on the already existing data. But I can not find any way to do so.

Is there none? Or did I just not find it?


texts:
I am designing an application where I am interfacing SIM900 with PIC18F2520. I am making a call to a number using ATD. Now if the receiver end do not answer the call, or if its busy, or the call cannot be made. So the current call needs to be diverted to another number. Following are the response of ATD

OK         Command Executed
ERROR      Invalid Command
BUSY       Receiving end is currently on other call
NO ANSWER  Connection failed upto time out
NO CARRIER Call failed to connect or disconnected
CONNECT    Connection set up(ATX=0)

So in my condition, I need to check if the receiver end is BUSY or NO ANSWER or NO CARRIER then make another call.

if(
     (strstrrampgm(rxData,(const far rom char *)"NO CARRIER") != NULL) ||
     (strstrrampgm(rxData,(const far rom char *)"BUSY") != NULL) ||
     (strstrrampgm(rxData,(const far rom char *)"NO ANSWER") != NULL)
  )
{
   serialSendString("ATD91xxxxxx78;\r");
}

Now whats happening is when I didnt answer the current call NO ANSWER or BUSY or NO CARRIER so the if condition become true it makes another call. But if I accept the first call, GSM does not send CONNECT response instead while disconnecting the call it send NO CARRIER due to which, the if condition becomes true and second call is made (which is not required). I searched for it and found out the we need to enable ATX using ATX0, then it shows CONNECT response. I tried it but it didn't showed up the CONNECT.

Also I want to know that in which cases NO CARRIER is received. Whenever there is any network issue, it says NO CARRIER. If after connecting the call, we disconnect it, it again shows NO CARRIER. If I cut the call, sometimes it shows BUSY but sometimes (in another SIM) it shows NO CARRIER. What does NO CARRIER actually means. What conditions should I check for in my application.
Please help.!


texts: Small Wireless Gyroscope & Accelerometer

texts:
I'm looking to assemble a very small circuit to transmit data from a gyroscope and/or accelerometer to a computer via wi-fi. It also needs to be self-contained (so should contain a power source).

The circuit should be as small as possible because it needs be mounted to a hula-hoop for used in a performance. As I have zero experience in electronics, it seems like the Arduino boards would be a good start, but they all appear to be too large for my needs.

I can program, so interpreting the data shouldn't be an issue.

Could anybody point me in the right direction?


texts:
Hi guys I saw these window/door alarms https://m.dollartree.com/h5/r/product/Battery-Powered-Window-Alerts/p328789/index.pro at the dollar tree that work off a reed switch. When the magnet bar is separated from the main unit it sounds the alarm.

When they're realigned it turns off. I'm wondering how I could delay the alarm so if the bar magnet and unit are aligned it keeps sounding for a given amount of time (10-30 seconds) instead of instantly turning off as it currently does.

Couldn't find a data sheet for the ic so I did some measurements and found what seems to be the trigger pin. It goes high to battery voltage when alarm sounds and sits low at 0v when off. Could I simply add a capacitor in parallel?


texts: Make shed light come on, if dark outside and door is open (with NPN and hall-effect sensor)

texts:
I recently purchased a new shed with a polycarb roof. At night, when I enter the shed, I'd like a light that comes on (but not during the day!).

I'm trying to find a way for the light to switch on, when 2 conditions are satisfied.

it is dark outside
the shed door is open

I have resistors, 2N3904 NPN transistors, potentiometers and A3144 hall-effect sensors.

I've already constructed a darkness sensor (see picture). I now want to integrate a hall-effect sensor to keep the light off, when the shed door is closed. I have no Arduino or digital controllers. I would like to stick to the components I have, if possible.


texts: Ambient light rejection from photodetecting circuit

texts:
I've built a photodetecting circuit as below:

simulate this circuit – Schematic created using CircuitLab

And with this circuit, I'd like to measure brightness of a blinking LED:

From the left, light pass through 500 nm shortpass filter and hit the photodiode.

A problem is, ambient light reading is too high no matter when the LED is turned on or not (yellow line) as drawn with the blue line:

I have to limit a range of brightness reading from -1.5 to 1.5 V to feed it into another equipment which have a such input range. Thus, I can't replace R1 with a larger one to get a larger voltage difference between LED-ON and LED-OFF state until ambient light is filtered out.

With my little knowledge, it seems that it can be done by placing a pF-capacitor at some point in the circuit.

When I searched for ambient light rejecting circuit, however, they seem very complicated than what I expected.

Is there a way to eliminate DC component of brightness reading and amplify non-DC component of brightness reading?


texts: How to measure voltage drop across a wire?

texts: I need to measure the voltage drop across a short piece of wire (about .25 to .30 inches long). The wire (a fusible link) is permanently attached to a battery which is permanently connected to a system. There is no way to insert an ammeter. No, measuring the voltage of the battery will not satisfy my problem because each battery is one of many in parallel. Would an electrometer (Keithley or whatever) be a useful device to measure the voltage drop across the short piece of wire? I haven't used and electrometer for decades!


texts: EEPROM Write Cycle Time and Write Cycle Endurance

texts:
I have an embedded software application that is copying a buffer from RAM to EEPROM. In this case, the EPROM device is a 28C010 (128K x 8). The copying is done at non-regular intervals, generally in blocks of multiple bytes. I would assume that other (not all) EEPROMs behave like this one, but this is what I have to work with.

The answers to my questions below will help determine the strategy for saving persistent information while doing real time processing.

The EEPROM is accessible just like RAM with some exceptions for writing:

BYTE WRITE: Individual bytes can be written, and the completion of the write cycle can be determined by polling
PAGE WRITE: Contiguous blocks of bytes can be written for bytes within the same 128-byte block, and, as long as each byte write is followed by another byte write in the same block within 150 microseconds, then the benefit of PAGE WRITE are obtained. The benefit is that completion of the page write can be done by polling at the end of the writing of the block. (There are no delays between byte writes, and the completion of the page write cycle is internalized to the EEPROM.)
Write Cycle Endurance: There is a 10,000 write cycle limit. No other details are given.

In both cases, polling is accomplished by reading back the last byte written until the returned value is equal to the value that was written.

There are other ways to determine that a write is complete, including just waiting for the maximum specified Page Write cycle time, which is 10 milliseconds.

I intend to use polling, with the expectation that it will determine completion sooner than the 10 millisecond Page Write cycle time.

I have two questions:

Can I expect my polling time in Page Write mode to be proportional to the number of bytes written (or can I see some benefit from writing a few bytes as opposed to a whole page)?
How does the Write Cycle Endurance work? Is it applied to each byte alone or two a whole page (or to the entire memory as a whole)? In other words, if I write a partial page in one Page Write and later I write the rest of the page in another Page Write cycle, how does that affect my write cycle endurance? Does it count as two write cycles? Can someone elaborate on this?

Since Page Writes to EEPROM are completed internally by the EEPROM after the last write to a page, I can perform the writes in background in most circumstances.

The size of the blocks that are being copied will vary somewhat each time, and they can't be expected to be in multiples of the page size. They can be made to be as small as just over a page size or several pages+, based on a threshold that will be determined later.


texts:
Why do I get a different resonant frequency ( determined by finding maximum voltage @ various frequencies ) with a repeating narrow pulse square wave vs a sine wave?

Thanks Very Much.


texts:
Does anyone have any ideas what this chip is please?  Tried searching but to no avail.

(I think the chip Identifier is the TT617-18-1).

Thanks in advance.


texts: Print a PCB layout several times in the same sheet at once in Proteus

texts:
How can I replicate my layout so I can print several of them in the same sheet without having to do it manually (printing one layout each time and setting its position relative to the previous printing)?

In this layout example, the sheet has room for nine of them.

PS: as the image shows, I'm using Proteus/Ares version 6.9.


texts: what size supercapacitor do i need to replace 4 3.7v 2400mah batteries?

texts:
I have a 5v 2amp external usb battery pack that dis/charges 4 18650 vape style batteries. Each is 3.7v 2500mah.

My Question is, what size supercapacitor would replace the batteries, preferably more than the 10000 mah of the combined batteries? Big enough to hold and discharge over at least 2 hours. Then use solar panel to recharge the supercap. Solar panel also has a usb port but it's not always sunny in Oregon. Should I do away with the battery pack and charge directly from supercap? Phone and tablet are 3000mah and 4000mah respectively. Both charge at 5v 2amp. I'm an ac man learning to live in a dc world. Trying to cheat on Thomas Edison with Nicola Tesla.


texts: LM741 op-amp, converting positive output to negative

texts:
I've got a few LM741 op-amps that I purchased by accident months ago, but now I'm in a situation where I believe they may be useful.

What I want to do is convert a positive voltage to the exact equal output, but as a negative.

So, if my input is +2.2v, I want the output to be -2.2v (actually the ranges are 0-0.237v). I have read quite a bit on how op-amps work, but a lot of the details go quite a bit above my head and quickly go beyond my understanding when I research what I'm trying to achieve.

It looks like I need to wire it as an "inverting amplifier" which I do understand how to do, but I don't know exactly what is required to ensure the output is exactly the same as the input, but reversed polarity.

My question is whether someone could possibly point me in the right direction as to how to achieve what I'm attempting to do (if possible with the chip specified).


texts: STM32H7 32-Bit Counter with Reset, C Language Function

texts:
Need help a simple a 32-Bit counter with reset.
Pseudo code:
int x, value;
int count = 0;

while(count == 0)
{
    x = x + ?;
    osDelay(1000);
    if(x == 2^31 This Also? )
    {
        x = 0;
        break;
    }
}

I want x to count up to 32 bits and then reset with 1 s intervals.


texts: How to disconnect voltage from BeagleBone Black expansion pins?

texts:
I'm trying to create a cape that will safely power my BeagleBone Black from my car's electrical system. The design I am using is based on the one from this answer. The circuit there suggests a simple voltage divider to connect the ignition switch to a GPIO on the Raspberry Pi, which could then detect when the car is turned off.

I believe this should work for the BeagleBone Black as well, except the documentation says very clearly that "NO PINS ARE TO BE DRIVEN UNTIL AFTER THE SYS_RESET LINE GOES HIGH." (p. 95)

Now, I'm relatively new to electronics. I'm doing my best to research, so please bear with me if I'm way off on this.

I did some searching, an it seems what I need is a tri-state buffer to feed the ignition signal through. Am I right about that? And would something like the NL17SZ126 be the best tool for the job? Or should I be doing something completely different?


texts: Existence and uniqueness of solutions to Thévenin circuits

texts:
Suppose I have a circuit composed of ideal resistors, voltage sources and current sources, and Kirchoff's laws hold. The circuit can be solved using a system of linear equations derived from Kirchoff's laws. However, sometimes a solution might not exist. For example, if we short-circuit a voltage source, Kirchoff's voltage law fails on the short circuit.
As a person with a mathematical background, I am wondering the following:

What are the necessary and sufficient conditions for the existence of a solution?
Is the solution always unique?


texts: Has anyone designed a low noise amplifier in the ISM band (24 GHz) using the discrete fet CEL CE3520K3?

texts:
I have been trying to design an LNA in the 24 GHz ISM band using CE3520K3.

The FET is inherently unstable and one cannot use resistor loading at the input, resistive loading at the output, source inductor or drain gate feedback (RLC) circuit to stabilize the FET.

The only way to stabilize it is probably to use a bandpass filter at 24 GHz, with a very low bandwidth.

This filter might be used at its out- or input, but the best way might be to use it at the FET's output to preserve the noise figure.

Another limitation at 24 GHz is that there are no capacitors that behave like capacitors (i.e. the series resonant frequency of the capacitors is much less than 24 GHz). So has anyone designed an LNA using CE3520K3?

I have designed filters at 24 GHz using AWR MWO and Ansys HFSS. I can make the amplifiers stable using a bandpass microstrip filter. Also, I am using interdigital microstrip capacitors for blocking the DC. For dc bias at the gate and the drain, I am using quarterwave microstrip lines  to get an RF open.

I have asked the guys at CEL for an application note or any circuit that they have used to design the LNA. But they do not seem to have any application note or a circuit.

This is the plot of the input and output stability circles. You can see that the pink color plots are the input stability circles and the blue color plots are the output stability circles. These circles are plotted in AWR MWO.


texts:
I'm super rudimentary when it comes to elecrical knowledge.

I have a wireless charging transmitter coil that has the following specs:

Input Current
1.8Amax. @12.0Vdc Full load
Inrush Current(cold)
2.0Amax. @12.0Vdc Full load & Ambient temperature25 °C
Energy Consumption
At 11.5VDC or 12.5VDC, Energy Consumption≤ 0.03A

This component has overcurrent protection and is certified by UL and the Wireless Power Consortium.

It has no power input on the board, I need to add one myself. I want to solder bare wires that run to a usb-c female socket to then run power from a standard wall adapter. I want to use usb-c 3.1 because the spec says it can handle that much current (a.k.a. fast charge), but I don't know if I need something further to make that happen.

Three questions:

1) If I buy a breakout board with a USB C 3.1 socket that has no IC's on it, can I safely assume that it will just pass through whatever power is given to it, and will power the board?

2) Should I use a wall adapter that is 5v 3a, or 12v 1.8a? I keep reading that power supplies supply up to the amount listed but provide less if the receiving device requires less.

3) What size bare wire should I use between the USB C socket and the board? I have been looking all over for wire size charts but all I can find are for much higher loads. I was thinking I'd need to use between 20 and 24 gauge wire but would love some input.

Thanks for whatever help you guys can provide.


texts: Why doesn't a diode or transistor get neutral?

texts:
As we learn that diodes and transistors are made by some materials, and they are called P or N according to having extra electrons or holes.

If there are extra electrons on n-type silicon (doped), why don't they just flow through ground maybe and N part becomes neutral. And same thing is P side as well. Is there anything special about fabrication of them which keeps those holes and electrons in the package and not let them to be neutral?


texts: i would like to Identify an IC with top marking MQ1CE

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I would like to identify an IC named MQ1CE. I hope this is a micro controller.

Searching the internet I have got several answers such as a micro-controller, a knee-slapper (I don't know what that is), a coil serial to SPI converter and similar, etc.

The majority are referring to a micro-controller. I would like to know which one this IC is, and get a datasheet.


texts: can two separate circuits use the one sensor

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I want to monitor the temperature of my washing machine. I was going to connect a raspberry pi up to the thermistor at the bottom of the drum. Would this interfere with how the washing machine measures the temperature, if both the washing machine and pi are using the sensor simultaneously?
The sensor is NTC : K276
The washing machine is Logik L712WM20


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I am trying to understand the principles of a RC charging / discharging circuit however I'm at loss regarding certain aspects of its operation.

I have a square wave generator giving 0v to 5V levels at certain frequency, say 1Khz at 50% duty cycle.  My R = 3.3K and C = 100nf.

My thinking is that if the capacitor charges during the high state of the generator and discharges equally during the low state of the generator. Then it shouldn't have any charge left and should remain at that level(uncharged). However when I try it practically I find that eventually the capacitor charges to some mid level, that is 2V which my mind can't really comprehend.

Does the capacitor charge and discharge and different rates in an RC circuit what exactly is going on over then I can't really explain, can you?


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This is a pretty simple question really and I'll feel embarrassed when I get the solution but its bugging me for now.

The goal is to solve for I going from left to right. No values given for any of the resistors. My instinct was to do mesh current and I came up with this solution.

I'm not using I2 at all and that's bugging me intuitively. The bottom part of the circuit is essentially being ignored and that doesn't seem right. Should I be doing I1 - I2? Is there a better approach to solving this?

Thanks


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I am trying to code a simon Game on my FPGA, and I am a bit stuck at how i should create a pattern and detect it.

simon Game : http://www.freesimon.org/

My idea until now is, I create 99 states (99 because i am implementing 99 stages).
And using a random generator(which is still missing) determine what LED should be lid for each state,

then using a if statement, I check if each state(Each LED are matched to a button) match the button thats being pressed. If they match, it then checks if the next buttompress match the next state and so on.

Everytime it goes to the next state, i compare the state value with the value of stages, and if states

Could this be done smarter in some way??


texts: Y cap between AC ground and DC ground in SMPS

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I have seen in many SMPS there is a Y cap placed between AC ground and DC ground.
What is the need of this Y cap?


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I want to be able to control an external laser diode w/ a digital controller.

The laser diode requires 3V and 130-280ma to turn on.

The digital controller I have is NI USB-6501 (http://sine.ni.com/nips/cds/view/p/lang/en/nid/201630). I am controlling it through my PC using matlab. However, the controller only outputs 8.5mA, far below the diode current threshold.

I was wondering how I could amplify the current. I do not mind using an external power source.

Thanks for all the help!


texts: The gain of two op amps in series at high frequencies

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I have a following circuit with two op amps in series.

What is the gain in dB of this circuit at 13 MHz relative to its DC gain?

The 13MHz is well out of the normal operation region of the op amp.

I believe that the DC gain is
$$ 20\log_{10}\bigg(\frac{24}{180}\bigg)+20\log_{10}\bigg(1+\frac{2.7}{7.5}\bigg) $$
However, I am not quite sure how to find the loss for high frequencies.

I have tried calculating it using following equation
$$BW_{xdB} = BW_{3dB} \sqrt{10^{\frac{x}{10}}-1}$$
\$BW_{xdB}\$ is bandwidth of x dB and \$BW_{3dB}\$ is the 3 dB bandwidth. I have assumed that I could find the loss using this equation in the following form
$$ x = 10\log_{10}\bigg(\Big(\frac{BW_{xdB}}{BW_{3dB}}\Big)^2+1\bigg)$$
but it is wrong.
I have also tried to linear approximation of the loss for high frequencies on the log frequency:
$$ -3\:\mathrm{dB} -20\bigg(\log_{10}(f)-\log_{10}(BW_{3dB})\bigg)\:\mathrm{dB}$$
where the \$-3\:\mathrm{dB}\$ is the loss at the end of the 3dB bandwidth and then the loss is 20 dB per decade. But this was also wrong approach.

The equations above are always only for one amplifier, the total loss should be just sum of individual losses for each amplifier.

The gain at 13MHz relative to the DC gain should be -16 dB, but I do not know how to reach that value.