texts: Choice of solder influencing quartz crystal?

texts:
I had problems with DS1307 based real time clocks, the culprit seems to be the solder we used. Let me explain.

We were using an Adafruit DS1307 based RTC I2C module on a stock Raspberry Pi. The clocks were built - and found to be communicating ok (eg. I2C was good), but not "ticking", eg. the second was not advancing. Building them on a breadboard (not soldering) led to working clocks, so the module itself was out of the question.
Also the electrical connection between crystal and IC, as tested by a simple multimeter, passed on all units.

Further investigation and narrowing things down with my trusted bus pirate (a god sent device for us without heavy testing equipment!) lead me to re-solder the connections with my own (ie. what I use at home) solder - and voilà, they worked. Further narrowing down showed that I actually only had to clean and re-solder the connections of the crystal quartz, not even the IC side had to be re soldered.

Does anyone know or have an idea or explanation why
S-Pb60Sn40 does not,
S-Sn60Pb36Cu1 does work in connecting the crystal quartz to the PCB well, eg. in a way that the DS1307 starts ticking?
The large difference between the solder used seems to be in approximately swapped proportions of lead and tin used, but maybe the 1% copper does it's job somehow?
My further guess would be this has something to do with the choice of solder somehow damping the oscillator, but the "how" of it still leaves me baffled.

For the statistics: We have soldered 87 units with the "bad" solder, none of them working (eg. "ticking"). I have manually re-soldered 53 of them now, all working. For 48 of those I only de-, the re-soldered the crystal oscillator connections.

Edit 1 - Cleaning the solder pads
As proposed by some of you, I manually cleaned a number of PCBs with 70% isopropyl alcohol and/or pure water - no avail, the clocks still did not "tick" away. Only de-, then re-soldering the two crystal connectors makes them start ticking.

Edit 2 - The type of solder I used
The solder that did not work is this product from Stannol, the one that does work is this product from Felder Löttechnik GmbH (pdf in german, sorry, they don't seem to have an english version online).

Edit 3 - The flux that is in the solder (aka. getting closer...)
The non-working Stannol solder uses flux of type 2.1.2.A - that is, according to wikipedia an organic, water-soluble liquid (?? this seems to be wrong!) flux with halides. The working solder from Felder uses flux of type 1.1.2.B, that is resin, rosin based solid flux with halides.
\$\Longrightarrow\$ The culprit could either be the unknown "organic, water soluble" flux from Stannol or the different solder formula with added copper from Felder.


texts: Bad synchronous description error in VHDL

texts:
The process should react on both rising and falling edges of the MainClk. The only difference is it can also reset variables if the rising clock conditions are met. Since I handle all possible clock conditions separately, why does it give me an error -

ERROR:Xst:827 - "D:/Projects/Xilinx/blincker/blinker_mod.vhd" line 47: Signal PixlCounter cannot be synthesized, bad synchronous description. The description style you are using to describe a synchronous element (register, memory, etc.) is not supported in the current software release.

Here's the script:

COUNT4: PROCESS(MainClk)
BEGIN
    IF RISING_EDGE(MainClk) THEN
        IF  Stop = '1' OR SLEEP = '1' THEN
                FastCounter :=(OTHERS => '0');
                PixlCounter :=(OTHERS => '0');
        ELSIF (MainCounter >= 35) THEN
                IF FastCounter >= 3 THEN
                    FastCounter := (OTHERS => '0');
                    PixlCounter :=  PixlCounter + 1;
                ELSE FastCounter := FastCounter + 1;
                END IF;
        ELSE NULL;
        END IF;

    ELSIF FALLING_EDGE(MainClk) THEN
        IF (MainCounter >= 35) THEN
            IF FastCounter >= 3 THEN
                FastCounter := (OTHERS => '0');
                PixlCounter :=  PixlCounter + 1;
            ELSE FastCounter := FastCounter + 1;
            END IF;
        ELSE NULL;
        END IF;
    ELSE NULL;
    END IF;
END PROCESS COUNT4;

EDIT

Since the process occurs on the change of the MainClk (weather it's rising or falling), why is it not practical to simply check if it is rising or falling by if MainClk = '1' or = '0':

    COUNT4: PROCESS(MainClk)
BEGIN
    IF MainClk = '1' THEN
        IF  Stop = '1' OR Sleep = '1' THEN
                FastCounter :=(OTHERS => '0');
                PixlCounter :=(OTHERS => '0');
        ELSIF (MainCounter >= 35) THEN
                IF FastCounter >= 3 THEN
                    FastCounter := (OTHERS => '0');
                    PixlCounter :=  PixlCounter + 1;
                ELSE FastCounter := FastCounter + 1;
                END IF;
        ELSE NULL;
        END IF;

    ELSE
        IF (MainCounter >= 35) THEN
            IF FastCounter >= 3 THEN
                FastCounter := (OTHERS => '0');
                PixlCounter :=  PixlCounter + 1;
            ELSE FastCounter := FastCounter + 1;
            END IF;
        ELSE NULL;
        END IF;
    END IF;
END PROCESS COUNT4;


texts:
What is the difference between normal stepper motor (bipolar/unipolar) and 3 phase stepper motor?
I have found most of CNC cutting machine using 3 phase stepper motor. Is there any special reason for that?


texts: I have made a full wave rectifier circuit to obtain 5VDC, 9VDC and -9VDC. To prevent the ripple, i have selected C1 and C2 as 4uF which were shown below. I will use a 12V, 6W transformer to get AC input signals. Do you have a suggestion related to values of these capacitors to avoid the ripple or should i choose bigger capacitances like 100uF? Boxes are 7809, 7909 and 7805 regulators. Thank you so much.


texts: Switch LED with Solid state relay (PhotoMOS)

texts:
The SSR is a PhotoMOS AQY211EHAX rated to drive 1 amp. I seem to be shorting the output side of the SSR.

Is a pull down resistor normally required on the output side or am I missing something fundamental?


texts:
I get the following error when I try and upload code

Error in initializing ST-LINK device.
Reason: No device found on target.

The voltage is across VCAP1 is 0 which I find a bit odd.

I have alligned the chip as per the data sheet which can be seen in the following photo.

I am quite lost any help would much appreciated. I would think it is a power issue seeing as there is no voltage across VCAP 1? I dont belive I have fried the chip as this is the second attempt and I used anti static bags during transport and earth mat when soldering and assembling.


texts: Can you determine needed input voltage from just looking at this circuitboard?

texts:
Question poster's level of knowledge: BEGINNER/NOVICE/MENTALLY CHALLENGED

Device:

A stage lighting pan/tilt motor, for one axis. Used in sets of two to provide remotely controlled X and Y movement of a spotlight.

Function:

It has been designed to be controlled indirectly THROUGH a followspot light fixture, which itself is DMX controlled. The DMX movement instructions sent to the light are sent to the LIGHT, and then are 'forwarded' to each of two motors over Cat5 cable by the light. The Cat5 is 'daisy-chained' such that the connections look like this: DMX_CABLE_INPUT_TO_LIGHT>LIGHT>Cat5CABLE1>MOTOR1>Cat5CABLE2>MOTOR2

Goal:

Use motor control devices without having a light fixture
translating and forwarding the commands to the motor controller.

Reason for goal:

I have many of these motor units, but do not own the light fixture they are controlled by. I want to use the motors for the same purpose, but on different objects (Eg - a different model of follow-spot and/or other lighting).

Issue:

I have made magic smoke come out one as I attempted to figure out what it's power requirements are. 5v makes it smoke. I don't want to ruin any more by guessing and hoping, because I actually want to use these, not just experiment with them.

NOTE:

J1 on the RJ45 input board connects to BOTH J2 and J3 on the main board. The two pins on J1 closest to the "J1" label connect to J3 on the main board, and these seem to me to be the power input pins for the board as well as the motor.

ANOTHER NOTE:

I am working under the assumption that if I can supply power to the boards properly, I can then begin to explore how to address it using the DMX protocol, since the DMX protocol is 'knowable' via Google and it's voltages/signal are searchable. The boards, it seems, are not Google-able.

Also - Forgive me for my awful diagram.

QUESTION, IN THREE PARTS:

1) Can the power needs of the board be determined by visual inspection?

2) If the answer to number 1) is 'yes': What is that power need?

3) If the answer to number 1) is 'yes': How was this determined, in terms a novice might understand?


texts:
I am trying to read a serial string which comes through as "R0123" for example then I need the 0123 to be in an int. to send out through another method

Here is my code it is not working the way that I think it should

void loop()
{
  if(Serial.available())
  {
    delay(100);
    if(Serial.read() == 'R')
      {
        int r1 = Serial.read();
        int r2 = Serial.read();
        int r3 = Serial.read();
        int r4 = Serial.read();
        int red = ((int)r1 * 1000) + ((int)r2 * 100) + ((int)r3 * 10) + (int)r4;

        sb.sendColour(red,0,0);

        Serial.print(r1,0);
        Serial.print(r2,0);
        Serial.print(r3,0);
        Serial.print(r4,0);
        Serial.print(red);
      }
  }
}

`


texts: Preventing Altium via stitching on the designators

texts: In Altium, I want to add via stitching on the ground pours. But the vias sometimes are placed on the designators. I don't want to adjust the designators on silk every time after stitching. So, is there any way to tell Altium not to do stitching on my designators, even on any object on my silkscreen?


texts: Problems building simple traffic light circuit on a breadboard

texts:
I'm new to breadboarding and am trying to take this simple traffic light circuit and build it on a breadboard.
I'm trying to figure out where I went wrong but can't find the error. How can I fix this?
Tinkercad Link


texts: LTspice: Vary a capacitor's value over time

texts: I want to vary a capacitor's value over time.  A previous question (LTspice: Vary a resistor's value over time)  asked how to vary a resistor's value over time.  One of the answers was to use a time variable in the resistor's value e.g. R=11-100*time.  I tried this for a resistor and sure enough it worked. I thought I could use a similar approach for a capacitor e.g. C=11-100*time, but it doesn't work and I get an error message "Can't find definition of model 'C' ".  I'm far from being an LTspice guru and would appreciate some help.  Thanks.


texts: It's enough to connect the screen of a transformer only at GND and not to earth?

texts: A have a transformer with a screen between the primary and secondary windings and I want to power an audio amplifier with it. My amplifier has no connection to earth, it is powered only by two wires. If I connect the screen only to GND of the power supply (between the filter capacitors) the garbage from the primary will pass to secondary ?


texts:
Is there any problem with the below circuit for controlling power supply (as a load switch)?

Hi,
I am using this circuit to switch power supply to a load. I have gone through the datasheets and this looks likes it is okay. But, could someone please confirm if the the circuit used is alright?
The load current does not exceed 10A. The load can be a resistive load or a power supply to another module (not an inductive load).
(I know the MOSFET I used is rated for very high currents).
There is no strict requirement on the switching frequency (less than 1Hz) .
The supply voltage is 9V-12.6V. The control voltage is 3.3V.
EDIT: [pdf datasheet links]
https://www.diodes.com/assets/Datasheets/DMG6602SVTQ.pdf
https://www.mouser.in/datasheet/2/308/FDD8896_F085-D-1806946.pdf


texts:
I am trying to make a datalogger with an Arduino, that should measure the voltage and current comming out of a small solar panel. When I measure the voltage and current using a multimeter, I get a result of around 3.4 volts, and a current of around 122 microamperes.
An acquaintance told mee that, since I want to measure both values at once, I could just connect a resistance in series with the solar panel, so that I can measure the voltage and then use ohm's law to find the current, since I know the resistance.

In this case I am using a 10 ohm resistance, but that means that when I measure the voltage and get a value of 3.4 volts I should be reading a current of 0.34 Amperes. However, my multimeter reads 124 microamperes. What am I doing wrong? How can I fix this?

Edit: As suggested, I tried measuring in parallel. When I connected the setup shown below, I measured 1,5 v and about 3 microamperes without the resistance, and as soon as I connected it, it dropped to 0. What did  I do wrong? I tried to connect as suggested.


texts:
Please help me with this problem I have been set.

So, I have successfully used Kirchhoff's Voltage law to determine the voltages and currents across each of the resistors in question (R2 and R3). However, when I attempt to use Thevenin's Theorem, I don't really know where to start. I understand the logic of Thevenin's theorem, but when I remove 'R2' (changing it to A-B), I'm not sure how to handle the loop to the right, as it isn't your standard 'two voltage-source' network meeting to go through the 'R2' wire, it has an additional branch. This has completely thrown me and I can't seem to get any of my answers to match the answers I got when calculating them using Kirchhoff's laws. I verified my original answers by simulating the circuit on Multi-sim and measuring the current and voltages across R2 and R3, so I know they are correct, however, everything I seem to try using Thevenin's method doesn't match. Please give me some guidance on this. I appreciate your time.

My calculations using Kirchhoff's laws show that R2 has a voltage of 3.012V and a current of 0.00151A. They also show that R3 has a voltage of 3.012V also and a current of 0.0012A.


texts: Can I power a MOSFET from my uC in this way?

texts:
The uC is a PIC10F220, which if I read the datasheet correctly can supply 25mA absolute maximum on its pins. The MOSFET that drives the load is actually 4 pcs NCE0140KA in parallell, but drawn as one for simplicity. The combined capacitance of the MOSFET's is 13.6 nF. I have selected the values of R1 and R2 so that the transistor gate will charge and discharge as quickly as possible, in order to minimize the transition time when the the transistors will be half-open. I am doing this because this circuit will be potted, so I'm trying to minimize heat dissipation.

By my calculations the current drawn from the uC output should peak at around 20mA the moment the output is activated and stabilize at 10mA. The peak will be close to the absolute maximum of the pin, but I figure it will be OK since the peak will be very short: Time constant of the R1-M1 RC circuit is 250 * 13.6e-9 = 3.4 us.

The circuit will be used as a pwm control and the switching frequency will be around 2 kHz.

Have I got this right? What would you do differently?


texts: What are some ways to improve a voltage multiplier?

texts:
I am working on a Nixie power supply, but I would like to improve it.

I have 4x9V batteries in series for a total of 36V to be switched across a multiplier.
A (TTL) 555 timer is running astable from only the first 9V battery to generate a 8.5-ish volt square wave, 10kHz (or any frequency you want, I guess),  approx. 50% duty.
The 555 output drives the gate of an N-channel BS170 MOSFET.
The MOSFET drain is connected up to 36V through an approx 1.2kΩ resistor. This resistance needs to be as low as possible to push current into:
a 6-stage Cockcroft-Walton multiplier, which produces a nice ~220VDC output under no load. Unfortunately, it sags to about 155VDC when loaded by a 47kΩ resistor in series with the tube.

Things I like about this circuit:

It Works™
It can be built by extremely common parts I'm likely to have on-hand, e.g.:
It requires no inductors.
It requires no specialized IC's such as boost converters.
It requires only capacitors and diodes with voltage ratings to handle each stage, not the full shebang.
It crashes Multisim.

Things I don't like about this circuit:

The output voltage sags to ~155VDC under only ~600μA load.
I'm too stupid to think of a better way to switch 36V across the multiplier:
While the 555 timer output is high, I'm wasting over 1W across the drain resistor just to drive the multiplier.
The multiplier input voltage is hampered by the drain resistor.

How can I:

make improvements that can enable ~10mA to be sourced with less than 40V drop in supply output?

I have tried:

Replacing the MOSFET driver section with something like this:

simulate this circuit – Schematic created using CircuitLab

I toasted quite a few transistors trying this inverter. As shown, the gates of the inverter are pulled up to 36V by the 10kΩ resistor. Is it possible that the gate charge time is what destroyed the transistors?

EDIT: I just realized that the maximum ratings for gate-source voltage on both inverter FETs is ±20V. That would explain why they fried. Hmm, maybe instead of a single 10kΩ, I could make a voltage divider to drive each gate separately?

reading the Wikipedia article regarding improvement methods:

  For these reasons, CW multipliers with large number of stages are used only where relatively low output current is required. These effects can be partially compensated by increasing the capacitance in the lower stages, by increasing the frequency of the input power and by using an AC power source with a square or triangular waveform.

studying other popular Nixie power supply designs, such as these.

I suspect that switching the 36V across the multiplier more efficiently would go a long way toward improving the performance.

EDIT/SUMMARY: Switching the 36V across the multiplier more efficiently went a long way toward improving the performance. As several people suggested, something called "push-pull" was a quick fix here. A CMOS inverter with separately-driven gates makes the charge pump much more effective:

The supply now stands at ~216VDC when loaded with two tubes, a huge improvement:


texts:
When analyzing simple circuits to understand the theory of their operation, we often make use of the Heaviside step function, \$u(t)\$.

When we calculate a convolution integral, we must understand the time-reversed and delayed function \$u(t-\tau)\$.

How do we plot \$u(t−τ) \$ ?

What is the range of \$\tau\$ for which the value of \$u(t−τ)\$ is 1.

\$u(t−τ)\$=\$u(−(τ-t))\$.


texts: Is it possible to desolder the bond wires by overheating a chip?

texts:
I was trying to solder some VQFN packaged chips for the first time using a hot air gun, because that's all I have. I set the temperature to rougly < 350°C and startet the process. Sometimes it wouldn't workout perfectly from the beginning on so I had to hold it for a bit longer (up to 30-50 seconds) or make some corrections using a solder iron. A lot of these chips were not working properly.  Later on I figured out how to do it faster and manged to get two of them to work.

Now I started to wonder if I really destroyed these chips by overheating them. I really don't think the silicon or any other material was damaged by this. But what about the bond wires? Is it possible that they desoldered/detached?


texts: Why is it suggested to keep 2cm between the chip and the remote antenna in TESEO-LIV3F?

texts:
I am reading the TESEO-LIV3F hardware reference manual.
In the remote antenna subsection (9.3, page 24), it explicitly suggest to keep a couple of centimeters between the chip and the remote antenna.
I am curious to understand the reason behind this recommendation, I always thought that the RF-track should be kept as short as possible. In my case I have a direct track going from the chip to an SMA connector.
Do you have other good recommendations about RF tracks routing?


texts:
I'm designing a microcontoller wherein I want to use conventional chargers or draw power from USB port so I used a type C micro USB.

In my initial design, I'm assuming that I only need the Supply line from the USB and ground. so what I did was I connect the Supply line to a regulator via a bypass cap, then I'd shorted all the other pins to ground.

I've found that that is wrong (got my line smoking) and I'm now changing my design.

Can I ask what is the best way to draw power from USB? I mean what should I do on the D-, D+ and ID lines? A Google search shows different circuits like voltage dividers for D- and D+ or shorting them as a Dedicated Charging Port.

However, most of the circuits I'm finding involves having another chip to manage this. I'm not making something like a charger, just want to use the USB to power my device.

Is there any possible way to draw power from USB without any sophisticated circuitry? Will shorting the D- and D+ lines and leaving the ID line hanging work?

My last resort would be to just use a DC jack. But that's a shame since micro USB is almost everywhere.


texts: How to check broken Surge Protection Device

texts: I have this type of SPD,  how can i test if this device still in good condition?


texts:
Unfortunately, while in transport, my capacitor's terminal leads have snapped right to the bottom. What can I do? Can I solder something in their place, so it can work?

Many thanks.


texts:
I would like to interface several LTC6915 instrumentation amplifiers with a microcontroller. I have a schematic which looks something like below image:

What I figured out is that the two amplifiers are connected in parallel with each other and gain can be set simultaneously for both the amplifiers from microcontroller's GPIO.

Below is the image from datasheet which shows how to set gain.

What I understand is if I set D3, D2, D1 = 0 and D0 = 1 from GPIO of microcontroller, I would set gain 1. Is that correct? If I set different gain values, how can I interpret that what I have set is correct?

Also I would like to know what will happen if I set gain as 0. I read that gain increases the amplitude of the signal. So does gain 0 means it won't amplify the signal?


texts: Generator Output at different frequencies

texts: If a three phase generator is stated as 200kVA, 440V, 60Hz therefore a current output of 262A. If said generator is changed to deliver 50Hz power at 440V, would that reduce the power available? so the 200kVA generator would effectively be 166kVA ?


texts: Verilog: Instantiation of lpm_dff failed. The design unit was not found

texts:
I want to use lpm_dff components in my design. I can compile the code without problem in modelsim, But when i try to simulate my test bench i receive this error. I also add lpm library when i simulate the test bench.

Can someone help me fix the problem?


texts: A practical integrator that does not behave like a low-pass filter?

texts:
Op-amp integrators and some common integrators actually are low-pass filters in practice. So if a signal is DC, then it does not integrate but only multiplies by some amount plus some transient response.

Now of course integration over DC cannot be done for a long period of time, as this would definitely break the circuit. But for a limited time, is there any integrator that does proper integration for DC and some range of frequencies?


texts: Is JTAG faster than SWD for debugging on an STM32F with STLINK-V3SET programmer?

texts:
There is a new STLINK-V3SET programmer that someone dropped off on my desk today. It supports USB 2.0. My thinking is that if SWD is the bandwidth limiter in the signal chain then a new programmer isn't very useful.

Is SWD or JTAG faster with ST-link programmers and what are those speeds?

Do I get any benefit in speed from the new STLINK-V3SET programmer?

Edit:

My targets are STM32F4, STM32H7 and STM32F2


texts: Computer architecture why is MemRead used?

texts:
Why is a control signal MemRead needed for the Data Memory element if whenever the output Read Data is not desired it will be multiplexed out via MemtoReg?

Wouldn't having MemRead always enabled just cause Read Data to always output whatever is currently stored at targeted address, making it readily available to be used if required, or ignored if not required via the multiplexer?

Does Data Memory, being sequential, only execute on a clock edge and cannot complete two tasks at once like this? Isn't it true that combinational elements such as the ALU always output f(input1, input2) regardless of clock edge?


texts: Filtering the output of the "cheap MCU voltage inverter"

texts:
This is the circuit I have to create a negative rail for a local op-amp which needs the rail in order to manage to get low on the output rail. I've tried running a single supply but that did not perform well enough. The circuit works and with my diodes I get an output of -4.4V from 5V positive which is enough for my needs.

The problem is that the output is a bit noisy and I can see some low freq. pickup as well. How can I filter the output of the circuit? I've tried to increase the C4 capacitor which reduced the noise however the did not change the low freq. pickup.

The circuit will supply an op-amp used in analog circuit so low noise is important.

UPDATE: The schematic was wrong (did it in a hurry before leaving duh), however the circuit was hooked up correctly.

simulate this circuit – Schematic created using CircuitLab


texts: In an LED the electric circuit causes the electrons and holes in the P-N Junction to neutralize each other to produce light energy. Whereas in a rectifier diode, if I am not wrong, the electric circuit does not cause the electrons and holes to neutralize each other. Why is this so? Also, do the electrons in a circuit flow through the diode? If they do, why dont the electrons neutralize the hole?


texts: I've read various posts regarding differential voltage measurements.  I'm confused as to why it seems virtually impossible to measure differential voltages that are high relative to ground (like differential between 251V vs 249V) and feed that value to a microcontroller.  The challenge appears to be due to the fact that the A/D chips have limits of the voltage you can apply relative to the Vcc.  It becomes more complicated if you want to multiplex various differential measurements to the microcontroller. I've seen various discussions on this topic and no compelling methods, but every handheld battery powered digital multimeter appears capable of performing the function with the exception of the data transfer to the microcontroller.  Does anyone know how the multimeters acheive this?


texts: Doesn't High Voltage Lead to More Power Loss

texts:
In India we use electric supply at 230 volts / 50 Hz whereas in US it is 110 V / 60 Hz.
Since power loss in an equipment (say resistive heating element) is directly proportional to the voltage, therefore use of 230 V should be less energy sufficient. Why isn't so?


texts: Why drive a relay with a transistor switch?

texts:
It appears most people drive relays through a transistor rather than directly from a digital output pin on an Arduino.  I had wired the output pin directly to my relay before realizing this and it worked fine.  What's the transistor for?

Is it to protect the output pin from exceeding the max current if the relay coil has too low a resistance?

Or, is it to conserve energy taking advantage of the common emitter amplification?

To produce less heat perhaps?


texts: If there is a branch and the two paths lead back to the same ground, will they both recieve power?

texts:
I'm using an online circuit simulator found here.

When I have a single path through both LEDs, they each illuminate:

However, when I add a wire to create a cycle, one of the LEDs loses power:

Why does this happen?  If I were to write my own simulator, I would check to see if a particular path leads to ground.  If it leads to ground, it gets power, if doesn't lead to ground, it doesn't complete the circuit and doesn't get power.

In this case, I would say both paths lead to ground, and thus they should both get power.  I thought the simulation might be correct if "electricity takes the path of least resistance".

But then I read that this is not true.

Is the simulation correct?
Would only one LED light up in real life?


texts: So how should I go about cleaning a soldering tip sponge?


texts: Custom PCB with ADC for monitoring Lifepo4 battery bank voltages

texts:
I designed a custom PCB board to allow me to monitor the individual battery cell voltages in my Lifepo4 48v battery bank.
Here is a schematic of the PCB:

Basically I'm using a molex micro fit junior connector to get leads from each of the battery cells positive terminal, each lead gets connected to 1 of 2 high voltage 8 channel multiplexer's, the output of the mulitplexers goes through a voltage divider then to A0 of the ADS1115.
I'm using this as a hat for a raspberry pi 4
there are 2 voltage regulators - 1 that outputs 5v for the pi and ADS1115 and 1 that outputs 15v for the mux
The problem I am running into is when I run the following program to monitor voltage and set the corresponding gpio pins high for any of the cells, I get the same reading (~0.116v - ~0.119v) no matter what channel the mux is on. When the mux is set to low, I get 0v as expected.
Here is the program I'm using to monitor voltage for the ADS1115:
import time
import board
import busio
import adafruit_ads1x15.ads1115 as ADS
from adafruit_ads1x15.analog_in import AnalogIn

i2c = busio.I2C(board.SCL, board.SDA)

ads = ADS.ADS1115(i2c)
#ads.gain = 16

chan = AnalogIn(ads, ADS.P0)

print("{:>5}\t{:>5}".format('raw', 'v'))

while True:
    print("{:>5}\t{:>5.3f}".format(chan.value, chan.voltage))
    time.sleep(0.5)

I've tried adding a 10k pull-up resistor from scl to 3.3v on the pi header as well as sda but am getting the same results.
I'm super stumped here and would appreciate any help on this one!


texts: Changing DAC output how far, how fast, how to tell

texts: If I had say a 100MHz DAC I can't just change the output from 0V to max V in 10ns, at least I think I remember you can't do that in real life.  How do you understand what you can do from a datasheet?  I feel like I remember reading about this once but I don't remember what it's called.  I assume it's load dependent as well and I'm thinking of this in the context of having a 50 Ohm piece of coax connected to the output both source and end terminated.


texts: Modulated IR for optical transmission of encoder data (TSOP 4840)

texts:
Some background: I am a mechatronics engineer and I have just recently started my first job out of university as an electrical engineer. I feel a little out of my depth but I wasn't going to turn the job down. My first project at work requires me to design a system to wirelessly transmit encoder data to drive a slave conveyor table.

I'm required to use IR light to transmit the data over fairly small distances (<1m, probably 20cm or so). Using IR light is a hard requirement set by my boss.

I am currently using the following systems:

For transmission, I am using what I believe is a Pierce crystal oscillator circuit to generate the 40khz pulses, which has been tested, oscilloscoped and known to work:
To hook this to the encoder, I have powered the encoder, then hooked up channel A to the power pin (labeled 14 on the schematic) of the hex inverter in the signal generator, such that when the A channel is driven high by rotation of the motor, the signal generator is powered and switching the IR LED on and off at 40khz. I have tested this and can confirm that it functions.

The encoder is 500 pulses/rev and is expected to be driven at 0.682 rev/s, making for 341 pulses/s (Hz)

For receiving, I am using a TSOP4840 IR receiver.
I know that it is receiving, as I can see the LED indicator I've hooked up turning on an off SOMEWHAT as expected. Turning the encoder does have some effect on the LED indicator.

The conveyor the encoder is to control is to be driven by a single pulse train in a single direction, hence the use of only one encoder channel.

My idea is to transmit these pulses optically using the system described, such that as the encoder turns it's pulse is modulated at 40khz, sent to the receiver, then demodulated at the receiver circuit, and output as an individual pulse to the VSD of the motor. Some latency is of course expected, but is expected to be insignificant.

What I want to know is if the concept is sound and worth continuing pursuit of, what type of receiver circuit I should use instead of the TSOP4840 based receiver, since I'm pretty sure it's simply not good for my application, and what other changes you feel may be necessary.

I'm enjoying my new workplace and would like to really nail this project to secure my spot here. I absolutely appreciate any help this community is willing to provide me.

If there's any information I've forgotten to include, please let me know.


texts: Automatic parameter search for a given output in LTSpice

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I am simulating a circuit on LTSpice and was wondering if there is a way to set output parameters for LT to aim for by adjusting values of other components. I have used some software in the past that does this but i cannot remember if it was LTSpice or something else.

Thanks in advance


texts: Triac connected CFL or Incandescent bulb or Electronic ballast tubelight FLASHES

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I am building a triac based dimming circuit.

Everything is working fine.

The problem which I am facing is when I turn on or off any appliance (NOT CONNECTED TO TRIAC) in my any other room, the CFL connected to my triac flashes in its off state., also flashes if I try to generate sparks in mains line.

Earlier I was using MOC3021 which was producing far more false triggers, and cannot use opto snubber as it leaks some current and connect appliance flashes every second.


texts: Low Pass Current to Voltage Amplifier with 2 Op-Amps

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let's consider this two Op-Amp amplifier:

From what I can understand, it consists of two amplifiers:

A current to voltage low pass filter (at left)
A non-inverting amplifier (at right)

Well, there are some things I can't understand:

Why is there a feedback resistor R1? From my analysis (see next), the circuit behaviour would be the similar without it (it would be always a current to voltage low pass filter followed by a non-inverting amplifier)?

What is the role of the DC voltage Vs? From my analysis, it seems it's unuseful since it doesn't affect the neither first amplifier (the current I1 depends only on Vout) nor the second one.

MY ANALYSIS:
Let's evaluate the transfer function (transimpedance Vout/Iin) in the frequency domain.
Such an amplifier consists of two amplifying blocks which cannot be analyzed as totally indipendent circuits since there is a feedback resistor R1 that connects them.
For the first block, one can say that:
• The negative feedback provides 0V at - input pin (virtual short).
• By KCL, current on the parallel impedance Ra//Ca is equal to $$I_{a}=I_{IN}-I_{1}=I_{IN}+\frac{V_{OUT}}{R_{1}}$$
• By KVL and Ohm's Law, the output voltage of the first op-amp is equal to $$V_{a}=-I_{a}Z_{a}=-\frac{R_{a}}{1+j\omega C_{a}R_{a}}\left(I_{IN}+\frac{V_{OUT}}{R_{1}}\right)$$
For the second block:
• The negative feedback provides Va at - input pin (virtual short).
• By KVL and Ohm's Law, the final output voltage is equal to $$V_{OUT}=V_{a}\left(1+\frac{R_{3}}{R_{2}}\right)$$
Therefore:
\begin{cases}
V_{a} & =-\frac{R_{a}}{1+j\omega C_{a}R_{a}}\left(I_{IN}+\frac{V_{OUT}}{R_{1}}\right)\\
V_{OUT} & =V_{a}\left(1+\frac{R_{3}}{R_{2}}\right)
\end{cases}
So, by putting the first equation inside the second one:
$$V_{OUT}=-\frac{R_{a}}{1+j\omega C_{a}R_{a}}\left(I_{IN}+\frac{V_{OUT}}{R_{1}}\right)\left(1+\frac{R_{3}}{R_{2}}\right)$$ that means $$V_{OUT}+\frac{R_{a}}{1+j\omega C_{a}R_{a}}\frac{V_{OUT}}{R_{1}}\left(1+\frac{R_{3}}{R_{2}}\right)=-\frac{R_{a}}{1+j\omega C_{a}R_{a}}I_{IN}\left(1+\frac{R_{3}}{R_{2}}\right)$$ that means$$ \frac{V_{OUT}}{I_{IN}}(j\omega)=\frac{-\frac{R_{a}}{1+j\omega C_{a}R_{a}}\left(1+\frac{R_{3}}{R_{2}}\right)}{1+\frac{R_{a}}{R_{1}\left(1+j\omega C_{a}R_{a}\right)}\left(1+\frac{R_{3}}{R_{2}}\right)}=-\frac{\frac{R_{a}\left(1+\frac{R_{3}}{R_{2}}\right)}{1+\frac{R_{a}}{R_{1}}\left(1+\frac{R_{3}}{R_{2}}\right)}}{1+j\omega\frac{C_{a}R_{a}}{1+\frac{R_{a}}{R_{1}}\left(1+\frac{R_{3}}{R_{2}}\right)}}$$
that is the final transimpedance transfer function of this amplifier, which behaves as a first order low-pass filter. If, as written at the beginning, R1=10k, R2=3k, R3=5k, R4=1k, R1=10k, the resulting transfer function will be:$$\frac{V_{OUT}}{I_{IN}}(j\omega)=-\frac{\frac{R_{a}\frac{8}{3}}{1+\frac{R_{a}}{10k\Omega}\frac{8}{3}}}{1+j\omega\frac{C_{a}R_{a}}{1+\frac{R_{a}}{10k\Omega}\frac{8}{3}}}$$
You may see that, if I'm not wrong:

R1 doesn't change so much the transfer function. If it were infinite (i.e. no R1), the circuit would again represent a low pass filter/amplifier. What is its purpose?

I don't see any role in Vs. It's absent in the transfer function and I can't understand why it is included in the circuit (together with R4).


texts: Unsure how arduino is interpreting RS232 signal

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Disclaimer: I am a novice.

I have an RS232 connection with an RFID tag reader which I am monitoring via software on a desktop computer as well as an Arduino. The device is configured with 8E1 parity. The arduino is (to the best of my knowledge) set up for 8N1 parity. Both the computer and arduino connect directly to the reader, and receive the exact same signal.

The arduino is reading a tag as follows:

10 00 62 00 10 29 C0 0F 00 39 12 C0 56 00 8D 0A

The computer is reading the same tag as follows:

30 00 E2 00 30 69 80 0F 00 59 12 80 96 00 0D 0A

With my (limited) understanding of parity, I can't figure out the conversion here.
How is the arduino interpreting these bits to obtain those values?


texts:
If a power inductor is rated for frequencies of 50 and 400Hz, can you use it for the frequency range [50Hz;400Hz], i.e. also for frequencies like 333Hz that are not multiple of 50? I thought so until recently when I overheard someone say that such an inductor should only be used for integer multiples of 50Hz.

Is there something true to it, and if yes, why? I didn't find much info on that topic so far, so I was hoping you guys could help out


texts: i have a small question about interference. Do active RFID (860 MHz) interfere with NFC cards (13.56 Mhz) when placed on top of eachother? (NFC above RFID tag for example). Thanks!


texts: Best practice to switch on 4 power supplies from one single source

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First of all, I am a self taught maker with a passion for LED lights. So far I have built a few display signs for indoor applications, where one microcontroller is connected to a number of RGB Led Matrices (not more than 10) and these are then connected to a few power supplies. In each of those displays, I ended up having to connect each power supply to mains. So far this has worked out pretty well. However all power supplies individually provided 5v and not more than 10A, for a total of 20A, depending on the number of Led panels. Something I was able to handle easily indoors.

This time, I need to build a much bigger display for outdoors, made out of 32 LED RGB panels like these ones. They will be divided in 4 groups, each with 8 RGB panels, each powered by an individual power supply (5v/60A each), like these ones. I have been guaranteed that each power supply is enough to power 8 panels.

When the project will be finished, I will have 4 independent power supplies, each connected to 8 panels; in theory I will have to connect each one of them to a power source, located near the install. Is there a way to power all supplies at once from one single source? Should I connect them in series and then connect the first one to mains? Also, as each power supply will provide up to 60A, are they safe to be connected to a socket, the type of which one can find in a UK household or office space?

I am still developing the design, I am planning to position the 4 power supplies on the back of the display. Cables connecting each power supply to the LED matrices will be 40-50cm long. I would like the display to be movable, and it will never be positioned more than 5 meters away from a power source.

Datasheet for the above mentioned power supplies are:

Output power: 300W Max
Leakage current: <1mA (Vin: 230)
Working temperature: -30 ° C ~ 50 ° C
Cooling method: air cooling
Storage temperature: -40~80°C
Input voltage: 110/220Vac (manual dialing), 47-63Hz
Insulation voltage: I/P-O/P: 3.0KVac; I/P-FG: 1.5KVac; O/P-FG: 0.5KVac
Safety standards: GB4943, EN60950
Protection function: input undervoltage, overload protection, short circuit protection
Power factor: 0.50@230Vac
Size: length × width × height = 217mm × 117mm × 30mm


texts: Did I do this circuit diagram correctly?

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I just need some feedback on the circuit diagram I made (it's my first time):

This is for a mini-car. There are two battery packs, one connected to an Arduino UNO, and the other connected to two motors. Both battery packs have a SPST switch.

The battery pack connected to the motors has a 6V regulator, and an electromagnet connected to the Arduino (digital pin 8) has a 5V regulator.

Any feedback would be fantastic!

EDIT:

Okay, I changed some stuff around. Instead of connecting the motors/electromagnet directly to the digital pins (stupidly), I added MOSFET transistors to control the motors/electromagnet from the Arduino. The motors have a diode and capacitor. I hope this is a step in the right direction.

*the 6V regulator I mentioned earlier is not in here; I need to read more about it later and will add it in

EDIT2:

Okay, hopefully this is finalized circuit.


texts: Discharge risk of an LED fade-in circuit

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The simplest incarnation of the fade-in circuit I have planned is

simulate this circuit – Schematic created using CircuitLab
This gets a time constant of ~2.7s before taking into account the dynamic resistance of the amber LED with Vf=2.1V. It's to only fade in once on power-up and doesn't need additional control.
My question is: when the power is turned off and C1 discharges through D1, will I risk damage to the LED?
This graph from the specsheet:

suggests that if the capacitor had charged to 2.1V, on discharge it will momentarily be at the very top of the LED's rated current, 20mA. Adding a resistor inline with C1 would mitigate this risk but may interfere with the fade-in effect, as there would be an initial voltage over the diode at t=0. If I added this second resistor, I guess I could just choose it so that in voltage divider configuration it works out to well below the forward voltage drop of the diode?


texts: May I use two 16 gauge insulated wire in lieu of one 14 gauge wire for the speakers of a home theater system? Thicker wire is better for the quality of sound (or so do they say). So do two 16 gauge insulated wires provide the same quality of sound as one 14 gauge wire?


texts: Using an old eBike battery to power an electric trolling motor

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I have a couple of old 36v eBike batteries lying around. I also have a Minn Kota Endura C2 30 electric trolling motor for my small boat which needs a battery. My previous experience with a large lead acid car battery for the boat motor was really negative (it was so heavy to carry to the boat and then it leaked some acid as well). This makes me wonder if I could use my old, useless but powerful lithium ion bike batteries to power the trolling motor instead? I imagine powering an eBike motor might need a roughly  similar amount of power as a trolling motor.
The batteries are 36v and the motor is 12v though. Would it be possible to use a device like this buck converter to bring the battery voltage down to 12v and then just hook it up to the motor?
https://www.ato.com/dc-dc-buck-converter-36v-to-12v
What other considerations should I make before possibly attempting this?


texts:
I am trying to read a map sensor with an ads1232 ADC.
The Map sensor requires 0v(ground) and 5v+ and outputs 2.5v fluctuating +-2.5v depending on the pressure. The ads1232 can read +-2.5v but without the 2.5v DC offset. Has anyone got any simple ideas or can lead me in the right direction on how to shift the 2.5v back to ground.

Thanks


texts: Electric brushed motor for electric car project

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I am using a 24v 11amp 5700 rpm motor for a single seater car project.
The problem is that when i am connecting the motor directly to the batteries without any throttle or control the vehicle shaft moves a little and wires starts to burn out
On checking in clamp meter it is giving 143Amp
Now can any one tell whats the problem here?


texts:
It doesn't say on the data-sheet, but I'm curious where i can find if Microchip uses IEC or SI as standard for there memory sizes.

For example:

http://ww1.microchip.com/downloads/en/DeviceDoc/21754M.pdf

  The Microchip Technology Inc. 24AA512/24LC512/ 24FC512 (24XX512*) is a
  64K x 8 (512 Kbit) Serial Electrically Erasable PROM, capable of
  operation across a broad voltage range (1.7V to 5.5V)….

My question is:

By IEC (binary) its

(512*1024)/8 = 65.536 bytes

but according to SI its

(512*1000)/8 = 64.000 bytes

Anyone?


texts: What happens if we run 415V 3 phase motor running on full load on to a 240V 3 phase supply?

texts: I have a 415V 3 phase motor, but during emergency situation a 110V DC to 220VAC 3 Phase inverter comes into place. What will be the effects on the motor


texts: What do you actually mean by DC voltage gain and AC voltage gain? I know their formulas but I do not understand what they actually are? That is, I do not understand their significance is and for what they stand for.  So basically please help me understand what DC voltage gain and AC voltage gain actually are, not just their definition.


texts:
I am looking at the datasheet for a motor. This is an AC induction motor designed for use in electric vehicles. It includes the statement [my emphasis]:

  The motors are designed for installation in electrically driven
   vehicles. and are characterized by their high power density, ruggedness, long lifetime, and overall reliability. The variable-speed three-phase motors are operated from a frequency converter. The direct connection to the three-phase line supply is not permissible.

The AC specifications are never listed (I assume the inverter uses some frequency other than 50/60Hz, and you'd have to calculate the appropriate AC voltage/current requirements based on the DC requirements) so is that the only reason this wouldn't be allowed? Is this statement based on physical limitations, or is this just business?


texts: If I connect 8 batteries in series and two of the batteries are fully charged, while the others are partially charged, do the batteries eventually reach some sort of equilibrium?


texts: Building a RGB art project. Having a hard time with finding the right, Switch fuction

texts: Is there push button switch, always "ON" to circuit #1. Then when pushed "MOM" circuit #1 is off, circuit #2 is "ON"


texts: Does the continuous power-to-weight ratio of electric motors decrease with size?

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Background: According to the DEP overview section of this NASA paper, aviation companies are interested in distributed electric propulsion (DEP) because the scale-agnostic power-to-weight ratio of electric motors enables aerodynamic advantages from distributed propulsion.

However, I'm struggling to make sense of that claim in the context of commercially available electric motors. Small air-cooled Hobby motors, supposedly have continuous power/weight ratios of >7 kW/kg while Siemens' aerospace-optimized AC motor has a "record-breaking" 5 kW/kg ratio with liquid cooling.

What gives?!

Question: Does the power-to-weight ratio of electric motors not change with size, or does power/weight vs size just not change as quickly compared to combustion engines?

EDITS/Understanding thus far: According to Neil_UK, Brian Drummond, and Charles Cowie, a motor's ability to dissipate heat is proportional to surface area (\$Q \sim DL\$) while its peak power is proportional to volume (\$P_{max} = T_{max}\omega \sim(D^2L)\omega\$). Assuming weight is linearly proportional to volume (\$W \sim D^2L\$), then the continuous power/weight ratio of electric motors actually decreases with size because

\$ P_{cont}/W \sim DL/D^2L \sim 1/D \$

Correct?


texts: Steel vs iron for linear solenoid plunger

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How much more force would an iron plunger provide than a steel plunger? From what I’ve read it seems like it would be much better, but I have no idea where to buy an iron rod.

Also, how much of an effect does the material of the frame of the solenoid have on the force?


texts: Is there a Certification requirement for device using mains power in/around water

texts: Is there a device certification requirement when using mains power (60hz / 120V) in/around water? I'd like to market a custom fish-tank with integrated lightbulb and pump. The lightbulb won't be submerged, but the product will place mains power and water in near proximity.


texts: measuring the current for battery monitoring project

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I have to build up a battery cell(single) monitoring system which can calculate the cell's (single) efficiency which should be atleast 0.1% - 0.5% accurate. The cell would be charged over a couple of hours (nominal rating 12V - 15A), and then discharged during a specified time. At the end i have to calculate the total energy delivered to and obtained from the battery by measuring the current and voltage.
The sensed current would range in from few milli Amps to a maximum of 50 Amps. I read alot about current sensing online and i came accross a very famous opinion of using series shunt to measure the current if you require a high accuracy. I also came to know about high side sensing and low side sensing.
Now my question is would it be possible for me to measure the current with the help of shunt, as to me, my range seems a bit large (few mA to 50A), so would a 0.01ohms shunt for e.g would be able to cover the whole range (resulting voltage would be in between 0.01mV (for 1mA) - 500mV (for 50A) ) ? What i mean is that after amplifying my resulting voltage across the shunt before feeding it to the ADC, would i be able to measure the current accurately keeping in mind if i am using some AVR contorller for e.g which has a 10 bit resolution ADC, with a reference voltage of 5 V ?
Or if there exists any other solution, other than measuring(with high accuracy) via shunt resistor, please tell !
Thanks !


texts: Wi-Fi vs Bluetooth communications to android phone

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I am interesting in getting a device, (bare metal micro-controller with sensors), to communicate to an android phone.

The device is not wearable and the power difference between Bluetooth and wifi as a consequence is of no import.

The range only needs to be a maximum of 3m with a low data rate (<2.1 Mbit/s), so bluetooth would be ideal and something I would just select.  However, I am being questioned, why not WiFi?

What are the major advantages for WiFi versus Bluetooth for such an application?

e.g Are there any cost or regulatory implications for choosing one technology over the other?


texts:
I have built an H bridge to control a coil but I've got issues ...

I built my H bridge with 4 darlington transistor : Tip122 (datasheet : https://www.onsemi.com/pub/Collateral/TIP120-D.PDF) and I control it with an arduino MEGA.

I made a program that sends a square wave signal of 5V through the pin 7 & 6, and it works when I observe it on an oscilloscope.  However I can't have more than 0.3V at the level of the coil. I need roughly 3-4V and 3A for my coil(the resistance of my coil is 1.4Ω).

I put 1K resistor and the TIP122 have a gain of 1000 so it should be satured.

I have try everything but it still not work... I read on internet that with this type of circuit I will not have more 4 V at the level of the coil but I only have 0.3V, wich is clearly not suffisant.


texts: How to recognize the type of analog filter given its topology?

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Having trouble to tell what kind of filter (Low-Pass, High-Pass, Band-Pass, Band-Reject(Notch) are present given a topology in cascade.

In the following picture I see 3 stages, is this ok? (2 active stages, 1 passive stage) but cannot tell if LP, HP, BP, or Notch filter is which one and why.

/!\Note: the values of resistors and capacitors showed are of no importance right now and are the values by default in circuit lab.


texts: interfacing MOC3021 with high current back to back scr

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I want to drive two back to back thyristor with moc3021 for soft starter.Here is the circuit:

This circuit works for medium power SCR such as BT152,But I want to drive a couple of disk thyristor that need about 300mA for gate triggering current that MOC3021 can not deleiver.What advice do you have?
Thanks.


texts:
So I'm using the LMR16006 DC/DC converter which is suggesting to place a Schottky diode from the SW pin to ground with a voltage rating 25% higher than my input voltage, which is 50V. Hence, the voltage rating should be at least 62.5V.
Datasheet: https://www.ti.com/lit/ds/symlink/lmr16006.pdf
How much would it matter if I would take, for instance, a 60V diode?
Then, I'm struggling with the current rating.
For instance, I'm looking at components at DigiKey at this moment and I've made a list like this:
https://www.digikey.nl/products/en/discrete-semiconductor-products/diodes-rectifiers-single/280?k=schottky+diod&k=&pkeyword=schottky+diod&sv=0&pv914=119750&pv914=167594&sf=0&FV=-8%7C280%2Cmu70V%7C2071&quantity=&ColumnSort=0&page=1&stock=1&cad=1&pageSize=25
The datasheet tells me: ", the current rating for the diode should be equal or greater to the maximum output current for best reliability in most applications". Does this comply with the "Current - Average Rectified (Io)" in the list I obtained above? What does a higher or lower current mean in the application?
I assume an output current of 700mA in my system.
As I'm learning, I truly like some explanations on value choices
I've included a schematic in which D1 is the diode I'm talking about.


texts: Can the Arduino Leonardo act as a keyboard, mouse, and serial port at the same time?

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I am doing a project that requires me to control both a mouse/keyboard combination and a serial port to activate it. (I know, it can prevent me from using my computer, etc. but I have precautions already in place.) However, can the Arduino Leonardo be two devices (or technically three) at once without any additional hardware? I know Arduino has example on how to use both the keyboard and mouse at once, but is it possible for the Leonardo to compute the "triathlon of serial communications?"

I know there is one output that goes to the USB and one that can go to the TX/RX, so I could technically buy a serial to USB converter and hook it up for the serial side, but that can get pricey and hog two USB ports instead of one (very valuable on a laptop and a hub is not economical when you add shipping and the price for the UART module, and it is more fun figuring this out.


texts: MOSFET triode and linear region difference

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I am currently reading about MOSFET curves. I thought that the linear region and the triode region are the same , but I suspect I was wrong. my questions are briefly :

Whether ohmic and linear region are the same.
What is exactly the triode region and how it is different from ohmic/linear region?


texts: amplifier for 10V LED dimmer control using Raspberry Pi

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My problem is I need to have an amplifier circuit design - schematic + components BOM with specific model information that is able to provide a dimmable output signal (Vout) 0.2-10V <0.8A for a set of 8x LED drivers using Raspberry Pi PWM GPIO pin which is able to provide input signal (VG) of 0-3.3V <16 mA.

My understanding is that this can be achieved using MOSFET amplifier circuit.  I hired an LED vendor to design such a circuit and when he tested in the workshop he was unable to lower the Vout to <1 V, and consequently his circuit was unable to switch off the LED lights.  The MOSFET he selected was a D882 P33.  The LED lights need to have a low signal of 0-0.25A in order to turn OFF.  A negative signal will turn the lights back ON again.

I did some workshop testing using a circuit similar to the one below obtained from an online course from ECE UCSB, and reproduced the same problem.  I replaced the RBPI using a universal AC adapter 3V 500mA to not damage the RBPI during testing.

During my testing there were four problems I encountered

1) I was also unsuccessful to lower the Vout to <1A using two MOSFET models BF506 and 2N3906.  I believe that this requires a MOSFET with RDSON of <0.15Ohms and I couldnt find this value on the datasheet specifications for these models.

2) I was unsuccessful to establish a minimum drain voltage using R1, R2 resistors and was confused by the capacitor in the VG front end of the circuit.  When I connected a 100k Ohm resistor for R1 and a tiny resistance <100Ohms for R2 and the VCC connected to the VG front-end circuit, I was unable to control the voltage VG and the voltage would shoot up to >4V. I then removed the R1, R2 and the VCC connections and was then able to control the voltage.

3) I was not able to use the circuit when the capacitor was connected. Again the voltage VG would shoot up to 3.3V and I could not adjust at all, so I removed the capacitor.

4) The behavior of the VG and Vout was inverted from what was expected. When I provided a 0.9V signal VG, I received a 2.05V Vout, and for a 3.3V VG --> 4.32V out.  This is opposite to what was expected which is for the higher VG voltage to produce a low output signal Vout.

I'm adding a photo of the LED drivers. The vendor provided two types of models in the system. I realize in the original problem description I described for a single LED driver, but actually the system is 8x drivers connected in parallel.  Of the 8x drivers there are at least 2x different models, I have not opened to inspect for the other 6x.


texts: Altium: what layers these parts in this picture are?

texts: I'm going to create foot print of D-sub sdf-us91-95. in its datasheet this picture of holes is shown. but what are the layers of others and generally what are they?


texts: How can I determine PD for given impulse, based on transient thermal impedance for BJT?

texts:
I have (selected) a BJT to work with rectified mains application.
Transistor is PBHV9560Z (600 V, 0.5 A PNP)
https://assets.nexperia.com/documents/data-sheet/PBHV9560Z.pdf
Under normal operation conditions, this BJT can dissipate 0.5W without heatsink. Maximum current should be 0.5A.
One thing is not clear to me, I have a pulse of 9.64W (average) for about 100ms. Current is well in range but due to VCE of 260V, power reaches this level.

I'm not sure this is OK or not because datasheet don't specify a digested SOA (like for MOSFETs or other BJTs).
How can I estimate maximum allowable PD based on given transient thermal impedance for my case of 100ms?
Thanks in advance.


texts: Power consumption of TDA8029 USIM controller for 3V/5V cards

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we are using TDA8029 in one of our application board.
Just a summary of the circuit.

TDA8029 in our board connects a USIM card and reads the data and sends on UART.

In our board, 2 supply inputs of TDA8029 VDD, VDCIN are connected to 3.3V and we have support for 3V and 5V cards.

We need to find the TDA8029 current consumption for below 2 cases

VDD=VDCIN=3.3V and 3V card
VDD=VDCIN=3.3V and 5V card

Below picture shows current consumption for other cases.

There is no support from manufacturer currently. How to interpolate/approximate the current for the above 2 cases.

One more thing, as Card power is driven from controller after detecting the card, for table shared above in picture.

for VDD=2.7V 5V card Idd = 250mA but card current is 65mA --> Actual TDA8029 current consumption is 250-65= 185mA

For VDD=2.7, 3V card  TDA8029 alone current 125-50 = 75mA (excluding card current)

For VDD=5V, 3V card TDA8029 alone current 65-50 = 15mA

All these 3 situations are giving 3 different values of current consumption for TDA8029, which i couldn't able to interpret correctly. What could be wrong. please help.

There are similar controllers from other manufacturers with 80C51 core like SEC1120/SEC1100 or 73S1209F - These controllers have very less current consumption in 10-30mA.

Is there any issue with datasheet or my interpretation.?


texts: LED driver operation vs boost converter operation

texts:
I am having this A80604 - LED Driver IC for driving a string of 9 LEDs. Each LED has a forward voltage drop of 3.1V and a forward current of 300mA through each LED. So, I need to generate a maximum of 30V for this LED string with forward current of 300mA. My input voltage range is 10V to 16V
I tried to search in google but unable to find. I want to understand - What is the operational difference between this LED driver and a general boost converter?
How does this LED driver help to output the 30V for the LED string when my input is 12V? Is its operation similar to a boost converter?
I have read that for LEDs, we drive the required current through it, and then the appropriate forward voltage appears across the LED. So, does this LED driver work by producing the 300mA and the output voltage of 30V would increase/decrease according to the LED forward voltage drop?
Please let me know on how an LED driver operates and how is it different and advantageous from a normal boost converter IC.


texts: Are there any rules of thumb when computing pulse current ratings for PCB traces?

texts: Say I have a surface PCB trace, 4 oz, 50 mils. That trace should be able to carry around 15 amps continuous, according a calculator I'm using. (Obviously your trace ampacity estimates may vary with calculators, but that shouldn't matter for the purposes of this question.) So if a trace can carry 15A continuous, how much could it do for ten seconds? Two seconds? Half a second? Are there any rules for determining the pulse current rating of a trace as compared to its continuous rating?


texts: Is current draw the same when powering a device directly from batteries or from a dc-buck converter?

texts:
I’m having a strange problem here:

When I use two AAA batteries to supply a small slave flash, it charges in 10 seconds, with 1.4A instant draw for the first second and smoothly reducing current draw until 10mA, when fully charged, at the tenth second.

I have these three small dc-dc buck voltage regulators, to lower from a bigger voltage Li battery at 8.4V to 3V, to supply my flash at 3V.

The weird thing is that, when I connect the output of any of these regulators to the flash supply contacts, it works, but it draws much less current, at 200-300mA, alhough these dc-dc regulators are rated at 3A max, 1.5A continuous.

So my flash is taking forever to charge, maybe 30 seconds.

For testing reasons, i’m using protoboard wires, don’t know if it makes any difference just to test it.

Is there any reason these different units would perform The same (be able to supply less current than they should)?

These are the ebay links of them: I don’t have a rank to post pictures yet...q

The first one is the smallest and it’s called Mini 360, and it’s based on the MP2307. Input 4.75-23V, 3A peak, 1.8A sustained

The second one is slightly bigger, nas an enable pin, and it’s based on the RT8727. Input 4.75-24V, 2A max

The third one is similar to the previous, with no enable pin, and it’s based on the MP1584EN. Input 4.5-28V 3A peak, 1.5A

ebay link for the first one

ebay link for the second one

ebay link for the third one

Edit: I may have had some bad connections. I rewired all of then I managed to measure the outputs voltages of all three regulators, when charging the flash unit.

All of them performed similar, charging to full in close to 15 seconds. The first and second regulators had some 0.1V, 0.2V voltage drop, from 2.98v to 2.85v more or less but in the end of the charging they got back to they’re normal voltages.

The third one as the charging begins it raises the voltage from 2.99V to 3.05, as to compensate for the load, and at the end of the charging it gets back to nominal voltage.  It seems faster to charge, maybe a sec faster.

If I lower the output voltages of all three of them to 2.6V than it takes a much longer time to charge the flash to full..

But still, why when using two rechargeable NI-MH AAA batteries, at 2.6V (1.3V each) the flash still charges faster than all of these regulators at 2.99V?

Edit 2: I have another flash unit that uses 2 AA batteries. In this unit, when using any of the three voltage regulators I have, the voltage drops from 3V to 1V, leaving no time for the flash to charge and the voltage get back to normal. It turns itself off. If I increase the voltage to 3.2v it drops to 2V and the flash manages to keep on until it charges and the regulator gets back to it’s normal voltage. So, in this particular case, how could I prevent this voltage drop in these small units? Adding an electrolytic capacitor in parallel to the output?


texts: Since Iron has a skin depth of 220 micrometres at 60 Hz, and much lower at higher frequencies, how well would it perform as a DC power filter? Would there be any electrical downsides to using it as such (apart from DC resistance)? (I'm sure there are probably mechanical downsides, so this is more of a hypothetical)


texts: STM32F103 - Single-channel continuous conversion mode

texts:
I am currently trying to use continuous conversion mode on a single channel of STM32F103RB's ADC (ADC1, Channel_10 on GPIOC pin0) like described here on page 6.

Here is my configuration function for the ADC. I just took the configuration function for single conversion mode and changed it for "ContinuousConvMode = ENABLE;"

void vHIL_ADC_Configuration(void)
{
    int n;
    ADC_InitTypeDef  ADC_InitStructure;
    GPIO_InitTypeDef GPIO_InitStructure;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC, ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);

    GPIO_InitStructure.GPIO_Pin = PIN_ADC;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;
    GPIO_Init(GPIOC, &GPIO_InitStructure);

    //ADC1 Config

    ADC_InitStructure.ADC_Mode = ADC_Mode_Independent;
    ADC_InitStructure.ADC_ScanConvMode = DISABLE;
    ADC_InitStructure.ADC_ContinuousConvMode = ENABLE;
    ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_None;
    ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
    ADC_InitStructure.ADC_NbrOfChannel = 1;

    ADC_Init(ADC1, &ADC_InitStructure);
    ADC_Cmd(ADC1, ENABLE);
    ADC_RegularChannelConfig(ADC1, ADC_Channel_10, 1, ADC_SampleTime_1Cycles5);

    // Calibrate ADC before start
    ADC_ResetCalibration(ADC1);
    while(ADC_GetResetCalibrationStatus(ADC1));
    ADC_StartCalibration(ADC1);
    while(ADC_GetCalibrationStatus(ADC1));

    // Buffer init

    for(n=0;n<CURRENT_BUFFER_LENGTH; n++)
    {
        f32_CurrentBuffer[n]=0.0 ;
    }
}

How can I get the last ADC value without using DMA ? (Since I can't just use the same function as single conversion mode like below)

void vHIL_ADC_readADC1(void)
{
    int i ;
    static int BufferCounter = 0 ;
    static int CurrentBufferOldVal = 0 ;
    static float f32_readCurrent = 0.0 ;

    ADC_RegularChannelConfig(ADC1, ADC_Channel_10, 1, ADC_SampleTime_28Cycles5);
    // Start the conversion
    ADC_SoftwareStartConvCmd(ADC1, ENABLE);
    // Wait for EOC
    while(ADC_GetFlagStatus(ADC1, ADC_FLAG_EOC) == RESET);
    // Get the conversion value
    f32_readCurrent=(((5.0*(float)ADC_GetConversionValue(ADC1)/4096.0)));

    if(BufferCounter < CURRENT_BUFFER_LENGTH)
    {
        f32_CurrentBuffer[BufferCounter]=f32_readCurrent ;
        BufferCounter++ ;
        f32_CurrentMean = 0.0 ;
        for(i=0;i<BufferCounter;i++)
        {
            f32_CurrentMean += f32_CurrentBuffer[i] ;
        }
        f32_CurrentMean=f32_CurrentMean/BufferCounter ;
    }
    else
    {
        f32_CurrentMean=(f32_CurrentMean+(f32_readCurrent-f32_CurrentBuffer[CurrentBufferOldVal])/10.0) ;
        f32_CurrentBuffer[CurrentBufferOldVal] = f32_readCurrent;
        CurrentBufferOldVal++ ;
        if (CurrentBufferOldVal>=CURRENT_BUFFER_LENGTH)
        {
            CurrentBufferOldVal=0 ;
        }
        f32_CurrentMean=f32_CurrentMean/(float)CURRENT_BUFFER_LENGTH ;
    }
}

Thank you in advance.


texts:
I have often seen decoupling capacitors "hugging" the IC that they're protecting - but that's on '80s era through-hole boards, and things have changed.
It also doesn't help that the design of ICs, for some reason, puts Vcc and GND on diagonally opposite pins!
I know that decoupling capacitors should be "as close as possible" to their ICs, but I assume that the Vcc pin is more important? With (two layer) circuit board designs often having large ground areas, it implies that any ground is a good ground, and you can get better track layouts if you mount the cap perpendicular to the power pin, with the ground side "hanging in the breeze" on a convenient ground pad. I assume that running a specific ground rail to the IC's ground pin(s) is not necessary?
EDIT
OK, there seems to be some confusion (perhaps on my side!). Assume a one layer board, with an IC and capacitor with the following pinout:
14 13 12 11 10  9  8
                  V+       O Decoupling
V-                         O capacitor
 1  2  3  4  5  6  7

I can either do this (option 1):
14 13 12 11 10  9  8
                   +--O
 +--------------------O
 1  2  3  4  5  6  7

or this (option 2):
   14 13 12 11 10  9  8
 O--------------------+
 O--+
    1  2  3  4  5  6  7

or this (option 3):
14 12 12 11 10  9  8
                   +--O
                      O----(some adjacent ground path)
 1  2  3  4  5  6  7

I am inferring that #3 is a bad idea?
EDIT #2
Or maybe, since the decoupling is so important, I could do this (for a huge DIP40 chip)?
+-- (some convenient Vcc path)
|
|   40 39 38 37 36 ... 22 21
O                          +--O
O---+                         O----(some convenient ground path)
    1   2   3   4  ... 19 20


texts: 501 watt EIRP 2.4GHz RF system. What precautions I should take?

texts:
I am working with a system which has EIRP of 501 watts. The ERP for it is 300-310 watts. I am using a parabolic directional antenna. What precautions do I need to take?

Though the Wifi amplifier in it is just 20W 43dBm and antenna is 24dBi which effectively gives me 67dBi EIRP which corresponds to 501 watts. How far should I stand away from the antenna to prevent any health effects? And how does the power decrease with distance? Now I am not using an omnidirectional antenna. So in case of parabolic antenna, how does EIRP or ERP work?


texts: Is it possible to rewrite a Flash page after an interrupted write?

texts:
Suppose you have a Flash chip (NOR flash) which you are using for example for data logging, performing sequential writes regularly on it.

The question is what if the power goes off during a page write: Is it possible to "fix" the page by rewriting the same contents over it?

By my knowledge of Flash devices this should be possible as writes turn cells from 1 to 0, so an incomplete write I think should only drive cells more or less towards zero (so retrying the same pattern again later should only reinforce it).

The exact design is a data logging device which has a large NOR flash array for data storage and FRAM for intermediate storage (small, but supports immediate writes, so data isn't in danger of being lost during periods when the Flash can not accept it).

I can not do a complete erase + rewrite cycle when detecting such a condition (interrupted write) since I have no room to store a complete erase sector which is significantly larger than a write page (64Kbytes versus 256 bytes), so the most straightforward thing to do would be attempting a write again if the previous power off left behind an unfinished page write.

(Detecting the unfinished write is done by polling the chip's status, and maintaining a related state machine in the FRAM, so not by comparing data which might falsely indicate a succesful, but "weak" write due to a later power off during the page write)


texts: How do you choose a PWM Frequency to drive a DC motor?

texts:
I can clock the PWM to drive motors at most any reasonable frequency, but is there a "best" PWM frequency for motor control?

What must be considered when choosing a PWM Hz?
Is there a most efficient Hz per motor?

If so, is there a way to calculate that based on measured motor characteristics such as L, C, and R?

(This is the Lego motor we are using to drive an antenna rotor.)


texts: What is the meaning of ripple voltage? and How to calculate a rectifier capacitor?

texts:
What is ripple voltage?

I think it is the voltage difference of the two red arrows... Is that correct?

My second question: If I need to use a voltage regulator LM7805CV. What would be the value of smoothing capacitor?

The application is a cell phone charger. It uses a bulk transformer. The output of the transformer is connected to a rectifier circuit then a voltage regulator.
I need the final output of the charger to be 5v and the ripples are less than 10mV.

Thank you very much,


texts: Digital Magnitude Comparator: LSb first or MSb first

texts:
Most of the comparator designs/algorithms are based on MSb first approach (i.e, starting the comparison from MSb of the two numbers), which seems to be effective approach intuitively.
I was just curious to know, where might we find LSb based comparison to be more suited as compared to a MSb first.


texts:
I'm simulating a non-ideal inductor. For this, I use the equivalent circuit implemented on LTspice which models the parasitic components (Rp, Cp and Rs).

I tried to calculate from the data sheet the parameter of the SRR6028-102Y inductor (model available on LTspice).
The SRR6028-102Y inductor model LTspice is characterized by

L0 = 1mH
Peak current = 0.17 A
Rdc = 4.5 Ohms
Rp = 1.50139e+007 Ohms
Cp = 0 F

I used the following datasheet - https://www.mouser.fr/datasheet/2/54/srr6028-1391281.pdf and the formulas in this document - http://www.intusoft.com/articles/inductor.pdf to determine the Rp.
Q=Rp/(2πf0*L0) where f0 = resonance frequency.
So, Rp=Q2πf0L0
Rp=322π7e61e-3=1407433.509 Ohms, which is 10 times less than the 1.5e7 Ohms of the LTspice model.
Do you know where this difference between the LTspice model and my calculations come from?
Thank you,
Florian


texts:
Can anyone identify a part number for this capacitor?  It was removed from a Wells-Gardner 19K6101 X-Y color monitor deflection board, c. 1981.  Notice that there are 3 leads, with the middle lead marked NC.  The opposite side has "CE 85º C 17 (U)(V) JAPAN".  I can't find anything like it on the ELAN web site.  The only 3-lead cap this size I can find at all is a Nichicon ULB1H472M at tedss.com, but there's no info on the lead layout, and Nichicon doesn't list this part number on their website.

Is this part still available?  Or do you know of a suitable replacement with the same lead layout?

update: [In response to Tom] looks like hot glue might be the way to go.  There are some big holes next to the lead holes.


texts: I have a few p-channel mosfets (IRLML6401) on PCB's, and it seems like the resistance between the gate and the source varies from 600 to 1100ohms. Obviously this resistance should be in the megaohms range, so I was wondering what could be causing this. They function otherwise, could it be a breakdown in the oxide barrier from ESD? The boards were assembled in china, so it's possible that this factory (we've had QC issues with other stuff) might not be using proper protection?


texts: Wrong Multimeter connection / floating ground

texts:
What does happen if you connect a multimeter without COMmon ground?

Like in this question (Why does a permanent, non-moving magnet, stuck to a long piece of metal generate a voltage?) How would a multimeter react if you connect the leads to the current and the volt measure inputs.

Just "in the air", so not connected to anything
if measuring DC/AC voltage

(second one beeing probably more destructive)

Is there a fuse to prevent disaster?
I'm especially interested in what components are responsible for the output (the chip, the circuit board, etc.)


texts: Alkaline batteries used in Ni-Cd battery rechargable power outage LED emergency light

texts:
I have a Vector Rechargeable Power Outage LED Emergency Light that plugs into the wall. When the electricity goes off, it comes on. The instructions state to use three AAA Ni-Cd batteries and I only have alkaline batteries. Hurricane Irma is headed my way and I was unable to find Ni-Cd batteries anywhere.
Is is safe for me to use alkaline batteries instead?


texts: Do we need to use two clock source for TM4C123GH6PM?

texts:
Do need two separate crystal if hibernation mode is used ?
I was referring the Tiva-C LaunchPad evaluation board schematic.
Following is the screenshot I have noted from this file:

From ti-datasheet, oscillator input description is noted as follows:

So the question is:
Do we have to always use an external crystal as well for the use of hibernation mode?
Is this a common trait for most microcontrollers?


texts: Will VFD provide enough startup current for induction motor under full load?

texts:
I have a a 3-phase AC induction motor with the following ratings:

rated power: 0.75kW
rated current: 1.65A
rated voltage: 3x400V
rated torque: 5Nm
supply freq: 50Hz
start/rated current: 7.0

Will a VFD with a rated current of 4.3 A be sufficient to start the motor at full load?


texts: grounded emitter or common collector circuit or something else?

texts:
first of all, I'm sorry if I did not use the technical correct symbols for the circuit diagram, but I think it will do.
I've multiple questions. Maybe someone can give me a hint.

I'd like to control two diffrent types of high power LEDs with an Arduino UNO.
The 24V power supply is just as an example. There is ofcourse the option to use a smaller one.

1st: I'm not quite shure what kind of other schematics might be usefull. I know there should be at least a resistor before the transistor on the side of the Arduino as well as on the side of the power source, but when I'm looking at some information (http://www.elektronik-kompendium.de/sites/slt/0204302.htm sorry, its in german) it quickly gets complicated and I become insecure what I should do. Same goes for the kind of schematics for the transistor --> 2nd question

2nd: Grounded emitter circuit or common collector circuit? What might be more suitable? Or something completely different?

3rd: The four LEDs in line or better parallel with idividual resistors? What would be the advantage?


texts: How is pouring water addressed in high-voltage electric transport systems?

texts:
An electric train is typically powered with something like 1.5 kilovolts of direct current of something like 25 kilovolts of alternating current. In my experience electric device manufacturers charge a fortune for even 220-volts (mains voltage in many regions) appliances that can be used outdoors, so atmospheric moisture is a huge problem for electrical devices.

Yet an electric train will move under the heaviest rain with its pantograph contacting a bare overhead wire and no short-circuiting happens.

How is that achieved?


texts:
back at it again trying to use your genius brains.

I have been trying to teach myself audio amplifier design. The big road block I am getting into is the control theory part of it, meaning how does the feedback loop affect the op-amp characteristics such as adding a Zobel network, or a capacitor compensation in the feedback.

I would love to understand and workout the math of how to model op-amp and understand how the poles and zeroes are.

For example here is what I have been working with:

How do I approach this trying to figure out the feedback loop transfer function?

Do I assume in DC or AC? or do I need miller capacitance model.

My end goal is trying to figure out how does the Zobel network and other things affect the performance of the audio op amp. :)

Cheers.


texts:
I'm writing a new Arduino project that uses an 16x2 LCD Crystal Display with a KeyShield. I would like to construct a menu structure in which the user can navigate using the buttons.

I'm new to Arduino but I do have 5 yrs experience in C#. What I would like to do is the following:

Define an interface called Screen and inherit each Screen from it such as LanguageScreen, TurnOffAfterScreen, MainScreen, etc. Each specialized Screen implements a method called drawScreen that will take care of the screen content.

Now I would like to have a class named ScreenController that handles the navigation between the Screens. In this class I'd like to store the screens in an array Screen screens[3].

When user presses the Select button on the KeyShield the Controller would call the next Screen's drawScreen method something like this:

void showNextScreen()
{
   currentScreen++;
   screens[currentScreen]->drawScreen();
}

Is this possible to do in an Arduino project? Am I expecting too much? :)


texts: Minimum Effort to Run a 1100W Hot Air Brush from America to Japan?

texts:
I'm entertaining an idea of making a small power supply to get a certain hot air brush (For hair styling) to function on the Japanese power grid.

I like this hot air brush that runs only on 120V/60Hz and would like to use it on a study abroad trip coming up in June to Mishima, Japan (Which has a 100V/50Hz mains voltage/frequency in the place I'll be staying.)

What would be a reasonable solution to running a 1100W hot air brush like this that on the 100V/50Hz?

I had an idea of using either a full bridge rectifier (With capacitors (Although I haven't run the formulas for sizing)) or an 18650 battery bank -> 1500W inverter.

Are there other practical solutions that I missed?

EDIT 0:
The hot air brush is a Revlon One-Step Volumizer (https://www.amazon.com/Revlon-One-Step-Hair-Dryer-Volumizer/dp/B01LSUQSB0/ref=sr_1_1?keywords=revlon+ht+air+brush&qid=1553485451&s=gateway&sr=8-1-spell)


texts: I noticed that the input impedance of an op Amp is extremely high. Why is that so?


texts: USB differential data lines pulled up to 5 V

texts:
My design uses the compute module 3+ board from the raspberry pi foundation. I used the FSUSB42MUX schematic from the CMIO board to have a slave/host USB port. My problem is the D+ and D- lines are not being pulled up to 3.3 V, they have been pulled up to 5 V.  I am attaching both the PCB and schematic design incase anyone can see any easily visible issues that I can not. HDMI output is working fine, as well as the SD card lines. All USB traces have been routed as 90 Ohm differential pairs.
Please let me know if more information is required.


texts:
I'm currently converting an old MP3-player (a Creative Zen Stone) to a standalone music player for my children. One of the things I'd like to do is to add an LED which shows whether the device is powered on or off.

Due to how the MP3-player is built, the only place where I can easily modify the circuit is between the battery and the device itself. Therefore, my idea was to place the LED in parallel to the device and use a transistor to switch it on whenever there's a current flowing through the player.

simulate this circuit – Schematic created using CircuitLab

The battery says that it delivers 3.7V. The green LED needs 20mA at a forward voltage of 2.1V, so given the 3.7V from the battery it needs an 80Ω resistor. I'm currently using a 100Ω one, because that's the closest that I got.

This design somewhat works, in the sense that when I power on the MP3-player the LED lights up. However, it seems the player doesn't get enough voltage now, because it doesn't work properly (which it does without the additional elements attached). The base-emitter saturation voltage of my transistor is around 0.7V (accordingly, I'm measuring that the player only gets 3.0V).

How can I resolve this problem? Is there a different circuit design that I can use or should I start looking for a transistor with a very low base-emitter saturation voltage instead (assuming those exist)?


texts: How did they calculate the input variable's fuzzy set in this Wikipedia article?

texts:
I am looking to understand the fuzzy logic controller ,so I can design an adaptive fuzzy PID controller for an AC/DC converter.
Wikipedia "Fuzzy control system" article.
Here we see the table that represents the input variable's fuzzy set.

How did they calculate the numbers 0, 0.3. 0.7 and 1 and placed in that specific axes?


texts: Why the use of resistors when pulling something up or down?

texts: When pulling something up or down why is a resistor used and it not just connected straight to the +V or 0V rail?


texts:
I'm replicating the function of millis() for the PSoC4 in order to store the timestamp of a signal's maximum amplitude.
For this, I'm using a timer with a 1kHz to feed the count terminal so it counts up each millisecond but I don't understand what clock should I use on the clock input.

Reading the timer component's datasheet didn't help me much


texts: My LG monitor (25UM65-P) has original adapter (19V, 1.7Amp), can I use a different adapter (14V, 2.14Amp) for it? Has this any side effects or negative points?


texts:
I am using an npn transistor in TO-220 package, and its collector is electrically connected to the metal part on it. I have checked it via a multimeter. I use a heatsink for that transistor, with isolator. So after mounting it to heatsink with isolators, it is no longor electricaly connected, I have checked again. However, when I inspect the signals in the circuit via oscilloscope, I see there is some noise on waveforms, while trying to understand where it comes from, I have touched the heatsink with a metal, to be precise with the tip of the following instrument:

It becomes much smooter. I didn't understand how touching it would affect the stability. After some reading on the web, I saw some say that heatsink itself should also be grounded. I wanted to have your thoughts on this.

By the way, transistors(npn&pnp) are used in a class B audio amplifier.

p.s : This doesn't answer my question.


texts: The cheapest and smallest way of converting 3 V to 3.3 V

texts:
My microcontroller operates at 3.3 V, but all the CR2032 bateries are rated at 3 V. Is it safe to drive my microcontroller using this 3 V? Will it operate correctly?

I don't have to draw too much current, so the current is not an issue. If not, do I have to use something like NCP1450 to actually step up the voltage? Given that I have to reduce size, what is the cheapest way to achieve this?


texts: Source generator for Satellite Tuner input

texts:
I need to design a source generator for a TV factory. They want to automatize the functional tests by applying a test module to the TV's at the end of the production line. All the peripherals of the TV (USB HDMI Satellite Terrestrial etc) will be plugged into the test module and will be monitored if the TV operates fully functional.

There will be 500 TV's on the line tested simultaneously so the module has to be cost effective. So I will use Raspberry pi module for USB and HDMI tests but for satellite and terrestrial I am having trouble to find a solution.

I was thinking of using this type of solution for the satellite and terrestrial source input:

Can I use this DAC&Modulator structure to steam a video over satellite cable? For example, I want to send the video in the settings below:

If I convert a video to .ts (transport stream) format and directly feed into the DAC's input will I be able to see the video on TV? Lets say I will send the video data in 30MB/s into the DAC's input (to satisfy 30MS/s symbol rate) and set the Local Oscillator frequency to 1450-30=1420 MHz I think I will be satisfying the RF requirements. However, I still don't know how to set coding rate to 9/10 and to set constellation to 8PSK. I need help from experienced engineers in satellite commnication.


texts: Real life output impedance of a Unity-Gain OpAmp Buffer circuit

texts:
How can I estimate the output impedance of a unity-gain opamp buffer circuit?

With an ideal opamp the impedance would be \$0 \Omega\$, but we don't have ideal parts. E.g. the datasheet of the AD8226 instrumentation amplifier recommends a source impedance below of \$2 \Omega\$ as voltage reference. The example uses the OP1177 opamp to realize a buffer circuit. How do I know that the choosen opamp fulfills the design constraint or how would I choose a suitable opamp?


texts: Confusion about filter transfer function

texts:
Today I got confused about Low pass filter transfer function.
Let's assume we have a simple low pass RC filter . It is well known that at f=fc we expect -3dB (0.707) drop in Vin.

Everyone knows a LPF transfer function is:

On the other hand we know that :

Which results in :

If we set f=fc  we will have:

But I expected 1/√2 =0.707  !  I am sure I am missing something but can not find that because this differs from the formula that I knew:

.


texts: Does the power supply needs to be isolated from the earth for this circuit?

texts:
The following circuit is a discrete topology I have implemented on a strip-board to obtain +/-12V split supply from a regulated 24V single supply(V1 in the schematics):

Now V1 is not battery but a power supply SMPS or most likely a lab power supply. I want to observe the split voltages +V and -V by using a scope.

My question is does this way of split supply requires any precaution? Does V1's negative terminal needs to be isolated from the earth ground? In my case both the lab supply(V1) and the scope will be earth grounded. Am I violating something here? It seems to me V1 should not be earth grounded. Is there any other precautions for this circuitry?


texts: LTSpice: When running a linear AC simulation, how to view the voltage ratio between two voltages?

texts: For example, how would I see the ratio between Vi and Vo for a linear AC simulation?


texts: Is this a 3.3V to 5V logic level converter?

texts:
I am trying to interface an optical mouse sensor (OM10B) with an Arduino Uno. The sensor is 3.3V and the Arduino runs at 5V, but also has the 3.3V source. I found this very detailed homepage , where someone has done this and I am trying to follow it. However he is not using an Arduino and I do not understand the final circuit well. Since he does not write at which voltage he is operating his ATMega (3.3V or 5V), I am unsure whether I can follow his instrcutions without modifications. Here is the circuit diagram from that homepage:

I don't understand the usage of the Zener diodes at the bottom in combination with the 150 Ohm resistors for the SPI interface. Is this a logic level converter to connect it to an ATMega at 5V or what purpose does it serve? If it is not, how could I go about to connect it to my Arduino Uno?


texts: Encrypting/Decrypting messages with Elliptic Curves in Arduino

texts:
Is there any possibility to encrypt/decrypt messages using only Elliptic Curves Algorithms? I found this library ECC Arduino library but it only generates numbers, there is no function for encrypting/decrypting.

I am thinking, maybe it is not possible to encrypt/decrypt messages with only using ECC? Maybe I need AES or any other encryption library too? I don't know. That is why I am asking this here.

I compiled the test code of this library:

#include <uECC.h>

extern "C"
{
    int RNG(uint8_t *dest, unsigned size)
    {
        // Use the least-significant bits from the ADC for an unconnected pin (or connected to a source of
        // random noise). This can take a long time to generate random data if the result of analogRead(0)
        // doesn't change very frequently.
        while (size)
        {
            uint8_t val = 0;
            for (unsigned i = 0; i < 8; ++i)
            {
                int init = analogRead(0);
                int count = 0;
                while (analogRead(0) == init)
                {
                    ++count;
                }
                if (count == 0)
                {
                    val = (val << 1) | (init & 0x01);
                }
                else
                {
                    val = (val << 1) | (count & 0x01);
                }
            }
            *dest = val;
            ++dest;
            --size;
        }
        // NOTE: it would be a good idea to hash the resulting random data using SHA-256 or similar.
        return 1;
    }
}  // extern "C"

void setup()
{
    Serial.begin(115200);
    Serial.print("Testing ecc\n");
    uECC_set_rng(&RNG);
}

void loop()
{
    const struct uECC_Curve_t * curve = uECC_secp160r1();
    uint8_t private1[21];
    uint8_t private2[21];

    uint8_t public1[40];
    uint8_t public2[40];

    uint8_t secret1[20];
    uint8_t secret2[20];

    unsigned long a = millis();
    uECC_make_key(public1, private1, curve);
    unsigned long b = millis();

    Serial.print("Made key 1 in "); Serial.println(b-a);
    a = millis();
    uECC_make_key(public2, private2, curve);
    b = millis();
    Serial.print("Made key 2 in "); Serial.println(b-a);

    a = millis();
    int r = uECC_shared_secret(public2, private1, secret1, curve);
    b = millis();
    Serial.print("Shared secret 1 in "); Serial.println(b-a);
    if (!r)
    {
        Serial.print("shared_secret() failed (1)\n");
        return;
    }

    a = millis();
    r = uECC_shared_secret(public1, private2, secret2, curve);
    b = millis();
    Serial.print("Shared secret 2 in "); Serial.println(b-a);
    if (!r)
    {
        Serial.print("shared_secret() failed (2)\n");
        return;
    }

    if (memcmp(secret1, secret2, 20) != 0)
    {
        Serial.print("Shared secrets are not identical!\n");
    }
    else
    {
        Serial.print("Shared secrets are identical\n");
    }
}

It gives me this output:

Testing ecc
Made key 1 in 1108
Made key 2 in 1107
Shared secret 1 in 1096
Shared secret 2 in 1101
Shared secrets are identical

and the RAM it uses is 566 bytes (6%) and 9846 bytes (3%) of flash, running on Arduino MEGA 2560 R3

Thank you


texts:
I want to make a stage box (with light in it) so when the guitarist or singer steps on it, it lights up. In the box I want to use a 12W (or maybe later 2) LED lights (which have a normal EU power plug).

I want to make initially two means of turning them on:

By stepping on the box (on a plateau)
By pressing a foot pedal

The reason is that I don't know if I can make option 1 very reliable, so option 2 is a backup.

Also since both options might fail, I want to use rocker toggle switches to bypass both options (meaning if both rocker switches are ON/bypass, the light should always light up).

I changed the answer to use a relay (instead of using mains, as of the comment of MrGerber below).

I had the following circuit in mind, but I wonder:

If it is a good way to bypass this way
If for the foot bypass switch, I really need a DPDT switch (I couldn't find any other way).
If I need another way as the relay.

(actually the 12W Led lamp is inserted with a normal power EU 220V plug, but I couldn't find a symbol for this).


texts: LiPo battery capacity valid at what discharge current?

texts: I would like to know for which discharge current the given capacity of a LiPo battery is valid. Let's say a battery is sold by the manufacturer as 400mAh capacity. Is there a standard discharge current to verify this capacity? Like 1/2C which would be 200mA?


texts: Verilog: Check for two negedges in always block

texts:
i try to do something like this:

always @ (negedge speed_dec or negedge speed_inc)
 begin
  do something
 end

This doesn't work as checking for 2 negative edges is to demanding and results in only checking for the clock.

I tried do do the check manually:

    reg old_key0;
always @ (KEY[0])
begin
    if(KEY[0] == 1  & old_key0 == 0)
            do something
    old_key0 = KEY[0];
    end

But now it completely stops working. Can anyone spot the error?


texts: Are magnetic sensors able to pick up the electromagnetic field inside toroids?

texts:
From my understanding, correct me if I'm wrong, the electromagnetic field outside a toroid is 0, but it has a EM field within the shell itself. So my question is can a magnetic sensor pick up on this field still? or would it only be picking up the weak field around it since real life toroids are not ideal? I'm assuming no?

I ask because I've been trying to use a 3D magnetic sensor for a contactless position system for quite some time now, but if the same pole is not facing the sensor at the exact same angle, or the the magnet is flipped relative to the sensor, the data becomes completely scrambled. I was thinking that because a toroid magnetic field, if detectable, since in theory has infinite/no poles, the data from the sensor would be constant or at least more stable and not easily affected by the rotation/orientation of the toroid in relation to the sensor?

I wasn't terrific in Physics, so if I'm completely off here, please let me know.


texts: In what condition,we can have \$P_{\Delta}=P_{Y}\$,not \$P_Y=\frac{1}{3}P_{\Delta} \$

texts:
The power consumption of three phase circuit, which is connected  with \$ \Delta\$ type, is \$3000W\$,now if we modified it with \$ Y\$ type,what is the power consumption of this circuit?

The answer is 1000W,because when we have the same impedance for each three wire,we can have  \$P_Y=\frac{1}{3}P_{\Delta} \$

But now i am confused that in what condition,we can have  the same power of \$ \Delta\$ type and \$ Y\$ type ,I mean,\$P_{\Delta}=P_{Y}\$,obviously if the impedance are the same between  the \$ Y\$ type connection and \$ P_{\Delta}\$ type connection,the \$P_{\Delta  }\neq P_{Y}\$

So in what condition,we can have \$P_{\Delta}=P_{Y}\$,just like the formula below:

\$P_{\Delta}=3\times \frac{V_L}{\sqrt{3}}\times I_Lcos\theta=\sqrt{3}V_LI_Lcos\theta\$

\$P_{Y}=3\times V_L\times \frac{I_L}{\sqrt{3}}cos\theta=\sqrt{3}V_LI_Lcos\theta\$

\$V_L\$ means line voltage,\$I_L\$ means line current

\$V_P\$ means phase voltage,\$I_P\$ means phase current

In the \$ Y\$ type,\$\sqrt{3}V_P=V_L\$,\$I_L=I_P\$

In the \$ \Delta\$ type,\$V_P=V_L\$,\$I_L=\sqrt{3}I_P\$