texts: Finding current and initial voltages of Inductor, capacitor and resistor

texts:
The switch in the following circuit was in position 'a' for long time , before passing to position b at t=0.

Find the initial current.

Find the initial Voltages of the capacitor , the inductor and the resistors.

What i tried

At t=0- , the circuit will look like this :

Since the switch was closed for a longtime , the current going through the capacitor will become 0 , while the voltage of the inductor will become 0.

Applying KVL : 28 +14I +20=0 , Hence I = -3A = I0

The voltage through the capacitor will be equal to the voltage through the 4K resistor + 28v

vc(t=0) = 4(-(-3))-28=-16V

and finally VL(t=0) = 0 since the inductor is short circuited.

However when the switch passes to the position b , the KVL equation doesn't apply anymore: -16+8(-3)+0+20 is different than zero.

Thanks in advance.


texts: AD7606 PCB Layout - separating Analog and Digital grounds when no dedicated pins are present?

texts:
The AD7606 (and all variants thereof) is an excellent simultaneous-sampling ADC. Simultaneous sampling is necessary for my application. However, this ADC, unlike many others, does not have separate analog and digital power/ground pins. I'm seeing some crosstalk from the digital lines on the analog signals. I'm wondering what the best way to isolate the analog and digital signals is for this chip. Currently I just have one ground plane for the whole system, including the sensors that interface to the ADC.

The sensors are electret microphones amplified by AD8429 In-Amps. The microphones are always powered and so are always gathering, and they're not triggered in any way by the system.

Here's the datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/ad7606_7606-6_7606-4.pdf

And here's the pinout:

The analog inputs are on the north side of the IC, and the digital lines are on the south  and west sides. Should I split the ground planes under the IC and star ground them at pin 2? Pin 26? Pin 47? The datasheet reads as if pin 23, Vdrive, is the digital power supply, but there's no dedicated digital ground. Any guidance is helpful.


texts:
PWM operation of DC relay coils in order to save power while holding is now common.  This is at a frequency that is high enough to avoid chattering or audible noise and low enough to not have to worry about switching losses or exotic circuitry.

The in circuit coil inductance can be measured by looking at coil current and analyzing the slope.  In this case if the PWM frequency is well known like say microprocessor 50% duty cycle at 8KHz and the supply is regulated 24V then you can easily get the coil inductance.

What I actually did was a self osc hysteric scheme which gave a change in frequency for a change in relay coil inductance.  The Idea is that one can tell the position of the relay coil by its inductance.  What I did Vs the orthodox ripple slope approach really comes down to implementation.  It is all the same in that you are detecting inductance change to tell if relay armature is in or out.

I was expecting big changes like more than 3:1 but that was not the case.  Why? Doesn't closing the magnetic circuit raise inductance markedly?

Sure the change was totally adequate to make a reliable decision regime for the firmware guy to do.  The real odd thing was that the pulled in relay exhibited less inductance.  Why would it appear to work back to front?  I didn't put this into production because the big relays were not needed after all but I have concerns about the scheme performing differently on different relays.  Is the concept flawed due to relay peculiarities?  Can it only be used in a specific case?


texts: Measuring 4-20mA current using the 4 20ma R Click module

texts:
I have a 4-20mA Receiver click module hooked up to a 5V Arduino. The goal is to have this system be able to measure 4-20mA current.

I'm using a simple resistor - LED circuit for testing, as well as a 4-20mA tester.

simulate this circuit – Schematic created using CircuitLab

The only time I'm able to measure current is if the circuit is externally powered using a 5V powerbank. I simply hookup the click module in series, and the Arduino can measure the current. However, I notice that without the click module the current is 1.3mA, and with the click module also in the circuit it is about 3.8mA.  (or 8mA vs 21mA if I use a different resistor).
I thought about powering the circuit from the Arduino instead of using an external supply, but the receiver gets really hot, and nothing can be measured. (I'm again putting the click module in series, just like I did with the external battery.
If I use my 4-20mA tester, externally powered at 12V, the receiver also gets really hot, and nothing can be measured

I'm having trouble understanding why these scenarios aren't working.

I'm also having trouble understanding how the 16V output from the TPS61401 step-up converter in this click module plays a role in these scenarios.

This 16V is responsible for "powering the loop", but in all 3 scenarios, isn't the loop already powered by the provided 5v / 12v ?


texts: Can you generate a pure sine wave by mixing a fixed frequency sine wave with a variable frequency square wave?

texts: Let us suppose I don't have a DDS available, and instead I have two square wave clocks with frequencies of my choosing. I have the impression that creating a wide bandwidth (multi-decade) sine wave could from this signal could be done two ways. In the first way, you use only one square wave clock, and you low pass filter through a switched filter bank, with a cutoffs positioned to deal with the odd harmonics (and I suppose whatever even harmonics are generated by parastics). Alternatively, it seems like you could fix the frequency of one square wave, use a crystal filter to get a pure tone, and then mix it down by driving a mixer using the other square wave as a swept frequency LO. As long as the square wave is of high enough frequency, you only deal with harmonics of the LO, which can be trivially filtered. I also understand that a properly designed mixer will suppress harmonics of the output signal... Marki's mixer have excent nlo+nrf figure. This second strategy would seem much easier as it doesn't require a switched filter bank. Have I understood this all correctly?


texts: I'm building a circuit similar as below. The input signal is a current which will be converted to voltage using a burden resistor. The inverted output sine wave will go into an ADC to calculate the RMS value. The signal can be 50/60Hz and it will have a DC offset. I would like to capture the RMS in one cycle so I need to take enough samples. I'm thinking of sampling at 2 kHz. As the signal has a DC offset, can I implement the formula below as explained in https://masteringelectronicsdesign.com/how-to-derive-the-rms-value-of-a-sine-wave-with-a-dc-offset/ ? Also, would I need to invert back the signal from the output of the amplifier?


texts: GPS and Barometer assisted flight on a mountain

texts:
This question is regarding a drone and its GPS/Barometer sensor and may not fit well in this community and if that's the case, please advise if I should move it elsewhere.

So. I have built a DJI F550 Hexacopter along with a:

Naza M V2 + GPS
H3-3D and GoPro
DJI mini iOSD
Boscam 600mw VTX
Skyzone goggles
Futaba 8FGH RX

I live in New Zealand and the ski season starts in the next few weeks. My plan is to take the drone to the ski slopes and do some FPV flying following my mates downslope and in the park with hopes to get some nice footage.

I have a few concerns about it, such as how elevation will play flying in GPS/Atti mode.

Atti mode uses a barometer to maintain altitude and GPS mode uses, well, GPS. In ATTI mode, does anyone know whether the barometer will be accurate enough to keep the quad at more or less the right altitude and aid me in my flight? If the sensor has inaccurate readings, the drone will likely jump up and down erratically.

Likewise, would GPS be reliable on a downward slope and constant changes in elevation? I have used a ski tracker on my iPhone before which used GPS and it seemed pretty accurate but I'm unsure what precisions these GPS units have on mountain slopes.

Anyone with experience or knowledge in this field that can help out would be greatly appreciated.


texts: Amplifier circuit doesn't work (what am I doing wrong?)

texts:
I'm trying to amplify a 0-5V DC signal (created bij a DAC) to a high voltage signal. I'm trying to do this via a Class A amplifying circuit (as advised by others before). For one reason or the other I'm still doing something wrong:

For now I'm using a BC550 transistor (B-E, on voltage: 0.6V, saturation voltage 1.1V). I built the following circuit:

I'm using R3 and R4 to create a voltage of ± 0.6 volt over R4 (to reach the on-voltage), then use R5 and R6 to lower the sine signal to 0- 0.5V (to not go over the saturation value). So if I'm right, the base voltage should alternate between 0.6 and 1.1 and be exactly in the active area of the transistor. So should result on a \$V_{out}\$ sine of 1 - ±19 volt (measured over \$V_{out}\$ - GND).

This is not happening so I'm doing something wrong. But don't know what. Do I not understand the working of this circuit? And what should I change?


texts: How could I transmit data from a device such as a distance sensor or quadrature encoder with an RF transmitter and also transmit a checksum or will I have to use a microcontroller such as the Arduino?


texts: I have a small (1/2"sq.) thin film piezoelectric transducer that I would like to use to test the frequency response of musical instruments. I want to be able to stick it on to any instrument , send a white or pink noise signal into the film thereby exciting the instrument with all frequencies and then record the response of the instrument with a spectrum analyzer. Being a purely capacitive load (high pass filter) obviously the transducer will not supply equal drive power at all frequencies, what would be a good reliable approach to assure that I have equal drive power at all audio frequencies?


texts:
I designed this circuit to scale a sine wave with a +/-5 V swing to scale to 0-5 V.
Also I'd like to be able to attenuate the input.

That's why the potentiometer is there (connected as a variable resistor).
Question: I made a simulation with the potentiometer pin 3 open and a simulation with pin 3 connected to ground. Same result.
I've seen both practices in similar situations.

What is good practice to do?


texts:
This is open collector gate.

I can not find the amount of the leakage current through the input.

Also not clear what output configuration must be to minimize current: leaving it floating - then with what input state? Connecting pull-up resistor - with what input state?

I would consider putting no resistor at the output at all, having output transistor turned on (~ground on the output), thus having input connected to ground (what would be a leakage current?).

Is it correct decision?


texts: I have a 12V 200AH lead acid battery and I want my load be  a power resistor and a bulb. Does the batter draw current based on the load resistance? so meaning the current that will be drawn in this case is 12/(load resistance) ? does a typical bulb require a specific voltage and current?


texts:
When I touch with my bare finger the oscilloscope probe I get a perfect sine ac wave 155V peak to peak!.

This is my first oscilloscope and I don't know if this is a normal glitch.

Do I have a faulty one?


texts: What is a hermaphroditic USB AB receptacle?

texts: Wikipedia's page on USB describes a "hermaphroditic AB receptacle". I cannot find any information on it - No pictures, specs or anything. Is this a single connector? Or have I missed the point?


texts: What's wrong with this casting in C code for AVR?

texts:
I defined two variables:

uint8_t a[2];
uint16_t b;

Next I want to use a as variable of type uint16_t, e. g.

b = (uint16_t)a;

But this is wrong! My programs doesn't works correctly with such code. All is OK when I replace b to uint8_t b[2] and use elementwise operations.

Why?


texts: What's a good sensor for measuring high voltages

texts: I want to do datalogging on solar strings in the 600V range +-100V.  Would prefer accuracy close to 1%.


texts: How to detect whether an audio output jack is connected to a headphone or an aux input?

texts: IS it possible for the source device to detect what's connected to the audio output jack?  Perhaps by exploiting the presence of the headphone's speaker coils and its response to oscillations?


texts:
This is my first design, a 4-Bit stereo DAC with LM386 amplifier.
I'm using it to interface with my FPGA eval board which doesn't have any audio connector. My board uses a 2x6 'PMOD' connector. My purpose is to create a stereo synthesizer which outputs square, triangle, sawtooth, and arbitrary 4-bit samples. Since each PMOD has 8 data pins, this works out great for 2 channels.

Rationale/Explanation:

*All parts are ones I currently own.

*FPGA outputs are 3.3V logic.

Pins 1 and 2 on the connector are VCC pins on the PMOD connector and are left floating as they are unused.
Pins 3 and 4 are ground pins on the PMOD connector.
Pins 5,7,9,11 are LSB to MSB data pins for right channel.
Pins 6,8,10,12 are LSB to MSB data pins for left channel.
I'm using an R-2R DAC for simplicity and availability of components. Since my resistors are 1% tolerance and this is just a 4-bit DAC, small inaccuracies shouldn't cause much trouble.
68 Ohm resistor before LM386 because the maximum recommended input voltage is 400mV. When all bits are high, the output voltage is ~3.10V. Output impedance of R-2R DAC is equal to R. Using a voltage divider, 3.10(68/510+68) = ~360mV. It will run at a constant output with external speakers controlling the volume.
Using standard gain of 20, therefore pins 1,7,8 are floating.
Both amplifiers working with single 9V battery as power source.
47nF capacitor and 10 ohm resistor as snubber circuit to prevent high frequency oscillations.
220uF capacitor to remove any DC component from output.

Thank you!


texts:
I never quite understood the finer details of why a diode is required for turning capacitors into "smoothing" capacitors instead of just low pass filters. The simulations I have done in multisim just seemed to add into the confusion. I realize that capacitors  just adds a phase shift to the current and does nothing to smooth out AC voltages by themselves unless we add a diode in series with the AC signal.
However the question comes when we try "smoothing" DC voltage with added thermal noise.
below is a circuit with diode D1:

and here is the oscilloscope plot :

However when I remove the diode D1 :

the plot becomes :

Now the biggest issues comes when I change the thermal noise frequency to 100hz, now both design without or without the diode are able to perfectly smooth out the noise. The 100hz is chosen at random and not a fixed threshold.
The R and C forms a basic low pass filter with cutoff at around 98Khz and are modeled as ideal components. My question is why is the diode required for the capacitor to perform its "smoothing" operations and why at 100hz it doesn't matter if the diode is there anymore, also why a diode is needed in general in series with an AC signal for capacitor to smooth out AC into DC signals.
Finally does that mean i should add a diode to LDO or buck regulators if I want capacitors to "smooth" out ripples instead of bypassing high-frequency components?
Thanks


texts: Using shielded cable on an ebike hub motor, what ground to use

texts: I have been having strange issues with an ibike that I have built, in that interference keeps being generated from the motors phase wires into the RX/TX lines on the hall sensors. I have been advised to use shielded cable on the hall sensor wires back to the motor. Do I ground the cables' shield to the chassis of the bike which is metal, or to the ground wire on the controller/motor? At present, the motor/controller uses its own common ground and isn't grounded at all on the chassis.


texts: Where to get started in designing a 3 phase motor circuit

texts:
I am required to design a circuit that requires a 3 phase motor which can be spin at a range of desired speeds and times.

I know this will require:
A 3-phase motor
An inverter to convert single phase to 3 phase
A PCB for login and to receive button signals
Some unit for the power

But I don't really know how to go from here. I studied general engineering so I have general idea of basic electronic concepts but I don't know where to go in terms of knowing what component goes with what and how the connect. Are there any resources for this sort of thing?

Thank you


texts: Does ITU govern both spectrum, and applied power?

texts:
I'm really not sure whether EE Stackexchange is the right place to ask. At the same time I'm sure it is the right place to expect a coherent reply.
I am aware of the various bands (C, S, K, X...) that are governed/allocated by the ITU globally, and allocated for utilization. From what I read online at no place is the amount of power to use on a particular band mentioned by the ITU.
I get the impression that ITU merely assigns spectrum; the amount of power to use on any particular band is a state subject. Is this correct?


texts:
Good day ,I need help in understanding a practice problem that my professor gave us.

  A parallel resonant circuit has Q = 20 and is resonant at ωO = 10,000 rad/s. If Zin = 5kΩ at ω = ωO
  what is the width of the frequency band about resonance for which |Zin| ≥ 3kΩ?

I know that in a parallel RLC circuit , the quality factor Q is given by the equation
Q=ω/BW and that the question seems to ask about the bandwidth .
What I don't understand is the relevance of Zin and |Zin| in the question. I know that in resonance,the impedance is purely resistive but I can't  understand what |Zin|≥ 3kΩ means.

Any help would be appreciated.


texts: Reducing LED PWM Noise: Which is the best option?

texts:
Driving an LED with a microcontroller should be easy. But when looking into noise, things can get complex...

As an instantaneous voltage indicator used in a variable power supply (which will be used to simulate a photovoltaic array of a student's designed satellite), I am using some LEDs controlled by PWM (~31 KHz).

simulate this circuit – Schematic created using CircuitLab

After the first revision of the PCB I have realized that each one of the LEDs is generating 200 mVpp in the 5V line:

My question: which is the best way to reduce this noise? Why?

From my (small) design experience I could come with the following possibilities. Which is the most effective, taking into account real-world components (ESR in capacitors etc)? Any other suggestion? A combination of several?

(Note: changing the PWM frequency is not a good option because that same signal drives other devices)

a) Decoupling Capacitor

simulate this circuit

b) Low-pass filter

(The resistor forms an RC low pass filter with the gate capacitance of the MOSFET, removing the high frequency components of the switching)

simulate this circuit

c) Snubber

simulate this circuit


texts: How to simulate bidirectional opto-isolators in Proteus?

texts:
I am making a circuit that uses the H11AA1 (http://www.vishay.com/docs/83608/h11aa1.pdf). This is a bidirectional opto-isolator.

I want to simulate it in Proteus, but in the libraries there are only uni-directional opto-isolators. ¿How can I simulate this device, or something similar?

I am suppose to have something like this:

Thanks in advance


texts: Multi-emitter transistor: does the transistor turn on per-emitter or as a whole?

texts:
In a multi-emitter transistor (like in TTL ICs), does the transistor switch on and conduct through the emitters independently or together? That is, if there's a base current through emitter \$E_1\$, does this result in collector current through just \$E_1\$ or through both \$E_1\$ and \$E_2\$? For example, suppose \$V_{BE_1}\$ is 0.8V but \$V_{BE_2}\$ is 0.1V, so only the first is enough to switch the transistor on.

I looked at this question, and it seems to imply that if the transistor conducts, both emitters get equal current, but I'm not sure I'm interpreting that correctly.

(My question isn't about the operation of TTL, but about multi-emitter transistors in general.)


texts: Why did a 1k resistor at the MOSFET gate solve my problem?

texts:
Why did a 1k resistor solve my problem?

I wanted to control a 3 wire computer fan with PWM(25 kHz 50% duty) from my Arduino NANO pin 10. My Circuit was very simple. I had an IRLB8721F N-Channel MOSFETn a dell HU843-A00(delta ) Chassis fan, a 4148 flyback diode and a pc power supply which I rigged to output 12v. The Arduino was plugged into my computer's USB.

This is the circuit, except I didn't have the 1k resistor in place.

With out the resistor the fan was squealing and wouldn't run, but with the resistor it was quiet and ran successfully.Why did the resistor solve my problem?


texts:
I'm trying to make an mesh network of 3 ESP32 modules. First one should get the sensor data and pass it to the relay node (2nd ESP32), which then gets the data and passes it to the 3rd ESP32, which then uploads it to the cloud via MQTT broker. Every single of modules will be battery powered. Also, they are supposed to go to sleep mode after the exchange of data. I'm finding difficulties describing everything program-wise.
Questions:

Is it possible for the middle ESP32 to simultaneously be GATT_Client with one and GATT_Server with the other one? How is it implemented?

Should data be transffered via Notify? I'm having doubts about passing it via BLE_Beacon function - is it doable and advised?

How to retrieve data from GATT Server and then use it for another transmission?

Update on 3:
Using serial monitor I checked that the data is sent from the server program, but the client part cannot read it. What could be the problem? Snippets below:
Server side (just the part where i set the value, it's done on the example BLE_Server code in arduino ide):
Characteristic_Tx->setValue(txString); //set characteristic value

Characteristic_Tx->notify(); // send value

Serial.println(txString); // here serial monitor shows me the right value

also from the BLE_client example, everything up to this point works according to serial monitor
Client part:
// Read the value of the characteristic.

if(pRemoteCharacteristic->canRead()) {

std::string value = pRemoteCharacteristic->readValue();

Serial.print("The characteristic value was: ");

Serial.println(value.c_str());

}

else Serial.print ("Cannot read the characteristic"); // this line gets printed

Question being: why is client could be unable to read the characteristic if the connection is ok and the characteristic is found and acknowledged?


texts:
I am using  Multimeter Voltcraft M-4650B to measure the voltage in the test point of a high voltage circuit. I want to find out the stray capacitance of my cable and for that I need to find the capacitance of the multimeter. I am unable to find the datasheet of this partcular model and hence am not able to get the capacitance. If anybody knows the value or knows how to calculate the value kindly let me know.

I also had an idea that I can measure the capacitance of the multimeter using a schering bridge. Will that work?

Looking forward to your reply.


texts:
I have different sound systems here. Some of them share the "problem" that they make a "popp" sound when I switch them on or off using the front-panel switch. If I accidentally switch off the socket they are plugged in, it's a very loud "popp" or more a "bang".

I know that some audio systems implement a soft-start circuit to overcome that problem. I can hear some relays click a few seconds after I switch the amplifier on, and from that moment on I can hear the music.

My questions:

1) Does that normal popp after front-panel switching harm the loudspeaker?

2) Does an accidental power-off, which causes that "bang", harm the loudspeaker or some circuits?

3) How should one implement a protective circuit?
Is it sufficient to set up a delay-circuit which controls some relays on the output of the amplifier circuit, or is it better to do it in "stages", e.g. first let the supply start, then give power to the amp and in the end switch on the loudspeaker itself?

Best wishes and thanks for your time in advance.


texts: Why is there a gate-source short on the n-channel mosfet? (circuit attached)

texts:
I am having a problem with the circuit below.

I am trying to use the IRLR8726TRPBF to switch a 24V pump by turning the Gate HIGH and LOW using the Arduino. However, there when I connect power to the board, there is a short between the Gate and the Source of the MOSFET.

Here is my power supply circuit. The GND common everywhere.

Before I noticed the short, I would turn the Gate HIGH and the MOSFET would get really hot quite fast. And it would switch an LED but for long, then it would go off.

What am I doing wrong? Any suggestions on how to solve the problem? Thank you.


texts: How to eliminate electromagnetic interference when counting pulses using a micro controller?

texts:
I have written a pulse counter program for ESP32 micro-controller, the counter counts the pulses correctly when there is no EMI interference but as I turn on the small AC drill machine the counter starts to count incorrectly. This issue was resolved by replacing 2n222 with BS170(N-channel, enhancement-mode MOSFETs used for low-power switching applications) for switching but when I turn on the workbench AC drill machine the counter starts to count and disturbs the results. The plan is to count the pulses correctly from a pulsar, pulse generator, flowmeter, reed, etc without any EMI interference.

Below is the circuit diagram:

The ESP32 VCC is connected to a step-down voltage convertor(5v -
30v).
The pulse frequency is 1khz.

ESP32 Code:

#include <Arduino.h>

#define PULSE_PIN  35

volatile unsigned long count = 0;

void IRAM_ATTR isr() {
    count++;
}

void setup() {
    Serial.begin(115200);

    pinMode(PULSE_PIN, INPUT);

    pinMode(2, OUTPUT);
    digitalWrite(2, HIGH);

    attachInterrupt(digitalPinToInterrupt(PULSE_PIN), isr, FALLING);
}

void loop() {

    Serial.println(count);

    delay(1000);
}

Any help is appreciated.

Thanks


texts:
I do not know how to compensate the DC-offset caused by the Input bias current.

simulate this circuit – Schematic created using CircuitLab

How to compensate the input current bias DC offset? I know the "trivial" method by adding the additional voltage (regulated by the potentiometer) to the OP-AMP input. But when I switch the SW1 the offset will change and it will require the additional calibration. Is there any "automatic" method to archive it?


texts:
I was wondering about anti islanding design.
Using grid tie inverters is usually the best choice when not investing in batteries, but suppose you have batteries and want the confort of grid tie AND get uninterruptible power in case of mains failure ?
if I understand well the current state of design and regulations for grid tie inverters is that anti islanding is compulsory.

Could it be designed better, for instance, in an islanding condition, the GTI could have a supplementary control bus to send a command to a relay / controllable breaker (something in this style :https://www.se.com/ww/en/product-range/60180-acti9-reflex-ic60) to isolate the domestic installation just after the power meter (on user side), plus a bus to sense when power returns between the breaker and the power meter.

When power returns, it can slowly regulate the inverter frequency to slowly bring back the phase into sync, lock it with PLL and switch back the controlled breaker / relay to tie to the grid.

I understand that it add complexity, and the need to sense the mains supply externally and control a breaker (which does not seem to be standardized when it comes to control, unless it is a simple relay), but some GTI already have external sensors or modules (like current sensors for GTI with limiters)

So, Why something this convenient is not yet marketed, (that would be hugely useful in California given the recent power cuts) ?

Is the problem the pulse generated by switching on the mains  ?


texts: Pico-itx motherboard Powered With Battery

texts:
I want to built a portable pc system. I am interested in the Pico511 pico-itx motherboard.

My concern is how to run a system like this on battery.
It's using 12V and for the top configuration it needs 2.5A. So if I have a 10,000mAh (10Ah) battery @ 12V, it will only power it up for 4 hours? (let's pretend there is no display or anything for now..)

Do I need a huge heavy battery? How laptops do this with 2x better cpu's?
Do I need a special "magic" battery? Or to look at some low-power boards?
And the last one, if I need to look at some more power-friendly boards, are there any good ones? (with kaby lake cpu's let's say)

To those who help me, may the force be with you!

-Christos Christou.


texts: Gain compression on an Ids vs Vds curve in Power Amplifiers

texts:
I haven't found a single document that talks about "Gain Compression" in a power amplifier referring to the typical Ids vs Vds curve. Books talk about a sinusoid "clipping" when showing these curves but never use the term "compression".
"Compression" is only used when showing gain vs input power or output power vs input power but is never mentioned when describing the Ids vs Vds curves. Why is that?

Can someone tell me where does compression start to occur on one of these curves and why would gain start to drop at this location?


texts:
I'm trying do design a mini-PCB, replacable half-bridge for motor control applications. The primary application is to use it with my modular inverter/BLDC/BDC controller. The controller design assumes 6 signals going to the bridge: GND, OUT, Low Side EN (optional), PWM, Gate Drive V (12V) and High Voltage (up to 60-70V DC), plus additional connectors for high-current HV and GND (up to several 10s of Amps).

The initial design was made around MIC4102YM, thus the LSEN and only one PWM:

During tests with real hardware, either the MICs or the 5 ohm resistors kept blowing up, even with rather low "HV" of 12V. I thus replaced MIC4102YM with MIC4605-2YM (replaces LSEN with NC) and R1 with a 0.1A 10V linear regulator (78L10). Additionally, I've added another small capacitor between the regulator's GND and OUT legs. I also soldered only 2 out of 6 possible MOSFETs in case my problems were caused by too much gate charge. The MOSFETs are IPD60N10S4L-12.

This time, the tests with 12V input passed flawlessly. The PWM signal was at 10kHz with duty cycle between 0 and 99%. However, when tested with higher voltage (about 50V), "something" blew up and I must say I'm quite out of ideas as to why. The regulator and the resistors seem to be OK, but when testing with 12V again, I'm getting only ~0.5V gate voltage on the high side. The current drawn also seems to be higher than it should, as when PWM is pulled high, the voltage on the OUT leg drops to about 4-5V.

I'm currently ready to re-design the mini-board, but I'm not even sure what went wrong this time. Previously I could blame currents too high for the driver, but it doesn't seem to be the case this time (as it was working just fine with lower voltage on the driven side). Am I missing some crucial filters/safety features?

P.S. I'm open to suggestions regarding using other parts or more/less integrated solutions, as long as they can handle >100A peaks with 60V DC.

Edit: The original PCB layout (bottom layer, top layer contains 2-6 FETs only):

My crude fix w/ 78L10:


texts: Constant Current IC Driving a String of ICs

texts:
I have been having difficulty wrapping my head around the ideas of constant current and constant voltage. Basically I have assembled this circuit with an arduino.

Now, imagine that I wanted to power a different number of LEDs on each pin.

1 LEDs for Q0 |
3 LEDs for Q1 |
5 LEDs for Q2 |
7 LEDs for Q3 and so on...

Now, in the past, I just wired each of the resistors in parallel and then attached their own individual resistor. And that of course worked fine. But I don't want to use so many resistors.

Presently, I have stumbled upon the idea of the constant current LED driver. Such as this one. Now, my question is it is possible to use a Constant Current LED Driver to light different numbers of LEDs on each pin and have them light up with the same brightness. If this is not possible is there some other way that avoiding the use of resistors would be possible? Adding transistors?

Overall, my question is if I can get around using resistors to light up a string of LEDs. My project has quite a few LEDs in it, and being able to eliminate the resistors that go along with them would be a great improvement.


texts: shift register that accepts 3.3V to drive several 5V relays

texts:
I want to switch several (10-20) relays with a raspberry pi.
I will use darlington arrays like the ULN2003 to drive the relays, and a shift register to not use up all of my GPIO pins.

I will use an external 5V power source just to be extra safe, in case I switch all the relays at once.

Since the raspberry uses 3.3V TTL logic, while my relays require 5V, I was looking for a shift register that converts the 3.3V to 5V.
I found the 74HCT595, which works off of 5V and is TTL compatible and can be cascaded. However, it seems noone sells it in a DIP package, and the stores I looked at have none in stock and need months to restock (mouser europe). Also, I'd really prefer a large package.

The 74HC595 (same data sheet, no "T") barely meets the requirements for the 3.3V input, and is available as PDIP. Would that be an alternative, or will I get erratic behaviour?

Another alternative I found is the SN74AHCT595N, which seems viable as well, however I am unsure if I can cascade it. I want to avoid buying the wrong part (again ;-/ ) and since I barely find any information on this part, I need some help ( all searches turn up the information on the parts without "A").

The datasheet mentions cascading, but it is not completely clear to me which pins I should use? Can I just connect  QH' to SER of the subsequent register? (for the other registers there was always some pin called SEROUT or somesuch.
Also, can I both source and sink current using this register, or are there some limitations? And where would I find this information in the datasheet, I don't see it.

Or should I use another shift register altogether?
I'd be happy for any pointers, thanks.

edit:
I checked the datasheet of the mentioned TPIC6x595 (where "X" is "B" or "C") and they seem nice, however now I have more questions. Both mention relay applications. The relays are dual coil latching KMET EA2-5TNJ and have an operating power of 140mW at 5V. The "B" outputs 140mA continous current, so I am covered, but will I still need darlington arrays to take care of the back-action during switching, or can I leave them out?

However, the initial idea was to use the raspberry 3.3V logic.
If I tie the relays to an external 5V and use the "B" driven by 3.3V logic to sink current, then I can switch to 0V just fine, and both coils of the relay will turn on when I want them to (The set voltage of the relays is 3.75V for both coils). While this may work, it doesn't seem proper, since I can never turn the coils off properly. Outputting high on the shift register gives me 3.3V, which means the coils are not active (5V-3.3V = 1.7V < 3.75V), however they aren't completely off either.

So in summary:

Do I need a darlington array with the TPIC6B595?
Should I just use a level shifter and be done with it, or can I make do without?
In case I need a level shifter, which one would be a normal one to use? Would a SN74AHCT245N be okay?


texts:
i am working on some CPLD-controlled SPI devices that will be daisy-chained together. I will be using 74VHCT126AFTTR tri-state buffers to disconnect the SPI and Slave Select lines on the device from the daisy-chaining cable.

I have now a few questions:

The 74VHCT126AFTTR buffer will be powered by a 5V power supply line that is shared with the devices. With this voltage supply, will this buffer a 3.3V logic level SPI signal to a 3.3V logic level on the buffer's output?

When the VCC line on the buffer is set to ground will this affect the input lines of the buffer significantly? Could this make a problem for the SPI communication of other devices on the same BUS?


texts:
I have this circuit using TL064IN OPAMP to amplify a 50Hz signal two times with different gains, the two output signals has to be in phase with each other. The problem is when I did the simulation to figure out the phase shift between two signals and then try to compensate for this phase shift by using capacitors, the LT spice simulation gave me a 38 mili degree when using the capacitors shown on the schematic. But in reality the phase is more than that. Is there any way to know the real phase shift and find the exact values for the capacitors other than try and error?
the graph of Gain VS frequency vs phase is not very useful for accurate calculation.


texts: Will the bright of the bulb increase or still the same in this simple circuit?

texts:
If Lamp2 is disconnected, What will happen to the brightness of the Lamp3?

I think that the brightness will remain the same because Lamp2 is in parallel with the branch that contains Lamp3.

Let's assume that I3 passes in Lamp3. When Lamp2 is disconnected, The total current will be reduced to be equal to I3. So Lamp3 and Lamp4 will not be affected. That's why loads are connected in parallel at home.

This question is in my younger brother's scholar book. The answer was: "The brightness of Lamp3 will increase because the total current will pass through it."

I think I'm missing something but I don't know what it is.

simulate this circuit – Schematic created using CircuitLab


texts:
If a system's output is \$X(z)+X(-z)\$ or \$X(z)-X(-z)\$, what does it do to the input \$X(z)\$?
I know what happens in time-domain, but not pretty sure about the change in frequency-domain.


texts: When should one use a RTOS (real-time OS) over a simple infinite while loop in an embedded system?

texts: The Arduino uses a simple infinite while loop. It works fine for me so far. What are some situations when a more complex RTOS is needed?


texts: How to measure H-Bridge motor voltage using ADC

texts:
I am controlling two motors using a double H-bridge controller.  I would like to measure the voltage at each motor using ADC's on the microcontroller.  The problem is that the motor voltage may be either positive or negative (depending on direction), while the ADC requires only a positive input.  What kind of circuitry is required to obtain a positive output from either a positive or negative input?  Ideally it would be simple and not require a lot of components.

I saw a similar question answered on this board which I have included below.  I built this circuit, but it produces positive readings on one output and negative ones on the other.  Does this actually work?  If so what am I missing?

Original answer (provided by jippie) follows:

When the motor is driven from a full H-bridge and you want your Arduino at the same ground reference as the rest of the car, then you can use the following:

Both outputs range 0 .. 2V4, and you should set Arduino's internal reference voltage to 2V56. By attaching both outputs to their own analog input, you can calculate the motor voltage by subtracting them. The capacitors are there to average PWM signals so it can be measured by the ADC.


texts: Is there a good/standard way to find the equivalent to this part but for a different connector?

texts:
I'm looking for a USB connector part. I've found one part that has the right mount, but it has the wrong USB connector (in this case it is a mini USB).

Is there a good way for me to look for a part that has the same mounting but for micro-USB or for USB-C?  No idea how to do a search either at Digikey or at Molex to do this.

Thanks for any help.


texts: LED board with constant + strobe operation circuit design

texts:
I'm looking for some circuit design tips to design a LED board with a built-in strobe feature, something like this:

16x high power leds (250 mA max, Vf ~ 3.2V)
24V power supply
One 24V input for low power constant operation (let's say 50 mA, total 800 mA)
One 24V input for strobe operation (at the full 250 mA, total 4 A)
Charge rate limitation for the strobe capacitors (let's go with 1 A total input current)

My initial I-dont-really-know-what-I'm-doing kind of thought is just to have two constant current led drivers, each set at the proper current, and just have the inputs drive those. One would have to be driven through a timer to limit the strobe time, maybe a 555 would do the trick?

Stuff I figure I need to consider:

The capacitor stuff for providing the strobe power is not something I really know much about.
The case where the board is in constant operation and charging the caps at the same time. (I guess charge rate for the caps should be 200 mA max)
What happens if both inputs are on? The strobe input probably has to suppress the other input.
And what happens if the strobe gets triggered before the caps are charged?
Do I need to discharge the caps when power is lost?
I've also considered just throwing a small PIC on there.

Lots of fun stuff to consider!

Another possibility might be if I could vary the value of the led driver's sense resistor. Not sure if that's possible or not.

So, as you can see I have no clue about this stuff. I suppose I could just have someone that works with this stuff design it for me, but where's the fun in that! Any suggestions where to start?


texts: I am really not able to understand why, when our personal computer memory is increasing in terms of gigabytes, the microcontroller memory is not increasing at that speed for both flash and RAM? What limitations are we facing for both kinds of memory?


texts: Using salvage power supply, RM1-3490 HP Laserjet

texts:
EDIT: What do I need to do, to hot wire the board to fully turn on?

I have a salvage powersupply from a big printer/copier and have a upcoming project and I'd like to use it.

Problem is I cannot make it power up properly.
I think main power from plug with red and black wires will give me 24v. And by the looks of it it packs quite a punch.

I have made this pinout by tracing the plugs:

>Plug1, main power output?!

>Plug 2

1 - 5v
2 - 5v
3 - GND
4 - 3,5v
5 - GND
6 - Relay, short to ground to close
7 - Opto pin 4, collector, part Q201 next to black relay
8 - NPN base, part pc100 next to green transformer
9 - GND
10 - nc
11 - nc

>Plug 3

Brown - 5v
Yellow -  3,3v
Blue - GND


texts:
I have a device that is powered off of a large battery. This device has peripherial ICs on it that consume power. Right now I have the input voltage through a switching regulator to 5 volts and then to a 3.3 volt linear regulator. This 3.3 volts goes to the entire board.

I also have a 3.3 volt regulator that is supplementary. This regulator is desired to power the MCU while being able to shut off the switching regulator to conserve power by only powering the MCU alone.

The schematic below shows what I am trying to describe. So 3.3_PERIPH_SHUTOFF is able to cut off the 3.3 rail from the rest of the board and turn on the supplementary regulator to power the MCU.

Then uC_PWR_CTRL is able to shut off the main power in.

D801 has been changed to a low ohm resistor.

Ignore the VUSB circuit.

But is this a good solution for a design that is able to sleep when desired, or is there a better way to do low power supply design?

Thank you


texts: Let's say I have a battery with V volts. A conductive material (Material A) is connected only to the battery's positive terminal. Material A is then connected to a second conductive material (Material B) that is not connected to anything. After Material A and Material B touch, they will then be separated. How do I calculate the charge on Material B after the two were separated?


texts: I have been trying to figure out how to custom wire a USB-C to USB-A cable for a while, with no luck.I have tried some different connectors, but wanted to get some outside ideas on what I might be doing wrong. I am not trying to make a high-speed USB-C, so I'm trying to make the connection with just a 4-core wire (GND, D-, D+, VBUS). On a few attempts, I tried pulling the ID pin up with a 56k resistor with no luck.  (On a different kind of connector not shown here).I contacted the manufacturer of one connector style that I have (images below) to get their assistance, but I am still having issues. So my question is:How would y'all wire this connector to a USB-A (2.0) so it works properly? Thank you! (PS: I am told that the connector has a 56k resistor built-in)


texts: Building using single sided PCB proto-board

texts:
I have a prototype board like this one:

Note that mine does not have the arrows/numbers on the side. Looks like a cutout from the middle section.

It only has golden circles on top. So far I'm used to using a prototype breadboard like this one:

I have an Particle Photon board. I assume i put it's pins from the other side but how do I than wire from there. For instance I have few other controllers which should all ground to the Particle Photon GND. How do I wire them to my GND pin ?


texts: How much electricity do voltage stabilizers consume?

texts:
I have recently installed a Voltage Stabilizer of 1000VA. When I got previous month's electricity bill, I was thundered. The bill was 3 times more than what I get usually.

I have not installed any new electrical appliance or device after I have installed the Stabilizer and I am only using the Stabilizer for my Router, PC, Laptop and TV.

I would like to know if I keep the Stabilizer running for 24/7 how much power it can consume ?

P.S. I use the TV as a Laptop's 2nd monitor and not used more than 2 hours a day. The router is on 24/7 and the laptop runs about 14-16 hrs/day.

Any kind of help is appreciated.


texts: Is there a more realistic circuit simulator than Falstad's?

texts:
In real life, the 100mA load in the circuit below will experience a brief, partial loss in current and and a drop in voltage when the 4A load is engaged but this simulator is too basic to show that. I very much like how it visually shows current flow though. Is there something similar but more realistic out there?

circuit example


texts: If greater potential energy is toward pos charge, then why PN energy band diagram show lower energy toward pos charge across depletion region?

texts: If in an electric field, greater potential energy and voltage are toward the positive charge and away from negative charge, then why do PN energy band diagrams indicate lower energies toward the positive charge across the depletion region?


texts: Can a capacitor in a circuit receiving no power regrow a charge?

texts: When working on a tube guitar amp, you need to discharge the filter capacitors in the power supply before doing any work because they can still store energy when the amp is not plugged in.  I understand that much and don't have a problem with it.  But I've read in a few different places (here's one) that even after discharging the caps, if you don't leave a jumper in place to short the terminals, they can regrow a charge.  How can this happen?


texts:
I am getting familiar to SNR, noise calculations, thanks to this forum, however I often come across Bandwidth of the system to calculate resistor noise, to get rms noise from nV/rt-Hz, etc.
I have a pressure sensor (wheatstone) connected to ADC through an Opamp and I have a single RC LPF between Op-amp and ADC.
So should I take cutoff of LPF as bandwidth?
And on what factor should the cutoff of my LPF depend since the sensor is just giving DC differential output.

Op amp I am using is MCP6v07, in its datasheet I see a large spike at 10Khz in noise density graph, should I choose my LPF cutoff to be much lower than 10KHz.

I set my ADC to sample at 19.2KHz since it's datasheet says it to be optimal sampling frequency, Should My LPF cutoff depend on ADC sampling rate.?
Also is it this ADC sampling rate my BANDWIDTH?

I am so confused.
Thanks for any pointers.


texts: How can I communicate the difference between 2 watts of continuous power and a 2 watt capacity?

texts:
I'm trying to understand the difference between a power output in watts and a power capacity in watts, and I'm open to the possibility that I'm thinking about it all wrong.

If I want to charge a battery with a 2 watt-hour capacity, how long is it going to take me if I'm using a power source with a continuous output of 2 watts?


texts: I have no idea what this is and found nothing on google


texts:
I'm reading a spec doc on some CPU and I didn't get what does this mean:

  The CPU core requires only a single clock input at the ECLK rate

What does ECLK abbreviation stand for?
What does ECLK rate mean in a technical sense?


texts: What is semantics behind BJT and MOSFET transistor symbols?

texts: I'm just wondering sometimes - is there any meaning behind the transistor symbols? I can kinda see that an arrow in BJT points to direction of conventional current flow in BJT and a capacitor on mosfet's gate, is it really so or am I halucinating?


texts:
I have an application where the maximum DC current is 160A. However in reality the actual current flow never exceeds 40A. I want to measure the current with an ADC (like one found on the Arduino or a higher resolution ~16 bit ADC). I originally wanted to use a hall effect sensor, specifically the ACS770ECB-200U-PFF-T.

Typically, my application uses around 5A. I am aiming for a .01A resolution. I looked at the sensitivity (mv/A) and thought I could get a higher resolution ADC to get more accurate current sensing. However when I looked at the data sheet it said the following:

  The noise floor is derived from the thermal and shot noise
  observed in Hall elements. Dividing the noise (mV) by the sensitivity
  (mV/A) provides the smallest current that the device is able
  to resolve.

This means that with the typical noise found in the datasheet of 6mv, and the sensitivity being 20mv/A, I would only get a .3A current resolution.

Am I correct? How can I achieve a >.01A current resolution? I can use a shunt resistor if I have to, or a 50A current sensor instead. But the 50U version gives 20mv of typical noise and 80mv/A sensitivity, giving a 0.25A current resolution.

Also, is this noise the ripple voltage of the power supply for the current sensor?

I'm also a little confused as to what the datasheet means by bandwidth

  120 kHz typical bandwidth

As I don't see what is oscillating.

Thank you for your time!


texts: Low-cost phototransistor to MCU interface

texts:
The simple way to connect a phototransistor to an MCU is shown in this question. But it requires a Schmitt trigger input which I won't have on my target platform, i.e. either an STM8 at 5V or an STM32F0 at 3V.

I fear that a direct connection without a Schmitt trigger stage might bias the input somewhere between high and low, causing undesired effects such as increased current consumption, additional losses and eventually damage. I need to keep BOM cost low, so I would like to avoid a Schmitt trigger IC (e.g. a single-gate 74x14) ans use a discrete circuit instead.

Are there any simple transistor circuits that can be used for this application?


texts:
I have an existing device that takes the UART data from the internal CPU and uses an FT232R to present that UART as a USB device. It was designed to be easy to connect to a PC since most have FTDI virtual COM drivers built in now, or at least be easy to install.
For an expansion idea, I'd like to be able to connect a small dongle to that USB device port and read that serial stream back out (for example, to attach a battery-operated Bluetooth radio).
It seems crazy to have a whole dedicated processor to connect to that FTDI device just to get the serial data back out.  The possibilities I have located so far are the FTDI Viniculum (which looks to be completely unsupported and obsolete) and the MAX3421E.  The CH559 looks cheap and interesting but it also looks like something that could just disappear into thin air at any given moment.  It would probably also give our purchasing team a stroke just trying to locate it.
Previous questions on this topic are older than parts like the CH559 and vague about the MAX3421. Is there anything else out there that provides USB Host and does the de-USBization of the FT232R?


texts: Mechanical Relay "Must Operate/Release Voltage" - Confusion Around Terminology

texts:
I have a relay and am confused by its operation.
It is a Potter & Brumfield Relay, model R50-E2-X1-24V
Datasheet: https://www.westfloridacomponents.com/mm5/graphics/ds4/SeriesR50.pdf
My confusion stems from the "Must operate voltage" & "Must release voltage" parameters on the data sheet.
The relay in question has a nominal coil voltage of 24VDC.
The datasheet states this:
Operate Data @ 25°C
Must Operate Voltage: 75% of nominal voltage or less.
Must Release Voltage: 5% of nominal voltage or more.

Based on my interpretation of that block, at 25C, bearing in mind that my relay coil's nominal voltage is 24VDC:
(This does not make sense to me)

the coil will operate at 18DVC or less
the coil will release at 1.2VDC or more

I have been doing some testing with my DC bench power supply, my environment is around 26C.
I am finding that the coil will switch/operate at just below 16VDC, emitting a "small" click noise. (This seems to partially correlate with the "Must Operate Voltage" parameter, 75% of nominal or less 24VDC)
When I turn it up to just above 19VDC, there is a louder click - but nothing appears to change WRT to the coil state, nor resistance of the pole->NO pins (the pole->NC pins as well).
When I have triggered the relay, I have found that the coil will release when I decrease the voltage down to 9VDC; and it will stay released until I bring the input voltage back to above 16VDC.
To me, this does not seem to directly correlate to the "Must Release Voltage" parameter (5% of nominal or more)
My questions/confusion can be summed up in a few points:

What is the significance of the "or [less|more]" in the Operate Data parameters?
For the release voltage, 5% of 24VDC is 1.2VDC, my relay will release consistently at 9VDC. How many grains of salt am I supposed to take with the "5% of nominal voltage or more"?
Based on number 2, "5% or more" would mean, to me, that the coil could release anywhere below 75% (Must operate voltage) - is this a correct interpretation?
For the operate voltage, it says 75% of 24VDC - that is 18VDC, if I am to take the "75% of nominal or less" at face value - the "more|less" seems to be inverted to me. Should I expect it to switch anywhere between 75% or higher? (IE, 18VDC-24VDC) Or should I interpret that as switching anywhere between 5% and 75%+?

Last piece... This may be me misinterpreting the data sheet, but I would like to validate my thinking and verify if I am reading this sheet correctly or not.
I am relatively new to the electronics world, and am picking up knowledge as I go. I've just picked up "The Art of Electronics" by Horowitz & Hill, to try to understand more about this all, but please excuse me if I've misused any terms here.


texts:
how are you all doing?
I have been experimenting with the Colpitts Oscillator and encountered a minor issue that I would like to resolve. Here are the two circuits - the first one is working flawlessly, while the second one isn't. Notice that the BJT biasing is exactly the same for the both of them.
First Circuit (Working)

Second Circuit (Not Working)

It is interesting to note that the circuit is oscillating in the LTSpice simulation.

What is the issue with the second one - as it is a textbook example? I would really like to know, thanks!


texts: Measuring capacitance by using two thresholds

texts:
I want to measure capacitance using a microcontroller. As there are various drawbacks in measuring capacitor voltage from 0V, this resource has it right by counting the time capacitor charges from one voltage to another.

What baffles me is a selection of lower threshold - they are measuring time capacitor charges from 0.17Vcc to 0.5Vcc. They say, it's time of 0.5RC.

I can't get this 0.17 value.

As far as i understand, to get 0.5RC, you have to charge capacitor in voltage ranges that are equivalent to time points 0.2RC to 0.7RC.

$$
t/RC=-ln(1-Vt/Vcc)
$$

if i try to calculate t/RC value at 0.17Vcc they use, i get:

$$
-ln(1-0.17) = 0.186329578
$$

That is far away from 0.2.

if i try to calculate Vt/Vcc ratio at t/RC=0.2 i get:

$$
Vt/Vcc=1-e^{-t/RC}
$$

$$
1-e^{-0.2} = 0.181269247
$$

So, the lower threshold should be 0.18Vcc, not 0.17Vcc. Am i correct or am i missing something?


texts: Sensor to track people sitting still in the room

texts:
I'm currently using a PIR sensor to turn on the light when it detect my hand's motion inside the box. But when my hand stop moving, the light turn off immediately.

Is there any sensor I can add to keep the light on after my hand stop moving?


texts: Stability of op-amps: "Oscillations if phase = 180° and loop gain > 1" question

texts:
I'm trying to understand the stability against oscillations for op-amps in a feedback circuit. A common argument I've seen on many sites goes as follows: The closed-loop gain is given as

$$A_{\text{cl}} = \frac{A_0}{1 + BA_0}\tag{1}$$

where \$A_0\$ is the open-loop gain of the op-amp, and \$B\$ is the fraction fed back to the negative input. Clearly, if the loop gain \$BA_0\$ becomes \$-1\$, then \$A_{\text{cl}}\$ diverges; this is taken to mean that the output is oscillating (a finite output with zero input).

This leads to what appears to be called the "Barkhausen criterion," that an op-amp circuit will oscillate if the magnitude of the loop gain equals 1 when the phase is -180°.

However, it is just as often stated that an circuit will oscillate if, at the frequency at which the phase = -180°, the loop gain is greater than or equal to 1. How is this reconciled with Equation 1? If I let \$BA_0\$ equal, say, 3.0 with phase shift of -180° (or really, any combination of \$|B_A0| > 1\$ and phase < -180°), Equation 1 has a perfectly well-behaved solution. Is this equation not really the whole picture?

I looked at the data sheets for a number of uncompensated op-amps (so that the phase would reach 180° while the gain was still > 1). Their Bode plots look nothing like the textbooks, and none of them had a magical frequency at which the loop gain was 1 and the phase was -180°.


texts:
I have this setup where a PIR sensor (HC-SR501) powers an LED strip with the help of a P2N2222 transistor.

I then manually connected the Transistor base to the 12v rail and it has no problem powering the LED strip. I have also tried changing the 2.2K ohm resistor with a 100 ohm and still the PIR sensor doesn't trigger the transistor.
I have tried powering a 3.4V 8mm LED from the PIR sensors OUT pin and it works fine, so the sensor's OUT pin is giving the 3.3V. Is it not enough for the transistor base?

What am I doing wrong here? Please advice.

Thanks in advance


texts: Have mechanical butler's bell, would like to ring it with push button

texts:
I have been recommended to post here! Basically I have a butler bell
which I'd like to ring from a few floors away with the use of a push button. I have arduinos, ethermegas, spark/particle core, but I wonder if I am over or under thinking things. How would YOU make this work? I have a few electrical parts and I'm not averse to buying a few more. Ideally I'd prefer simple and reliable over complicated and unreliable.


texts:
I need to build a regulated 48VDC ~1amp power supply.

I have two transformers on hand:
One with a 36VAC secondary which would give around 51 volts DC once rectified
The other with a 44VAC secondary which would give around 62 volts DC once rectified

Now, feeding the LM317(HV) with 51 Volts DC doesn't give enough headroom to my taste if we consider the regulator voltage dropout and house voltage variations.

Feeding the LM317(HV) with 62 Volts DC would exceeding regulator's input-to-output max voltage.

While searching the internet for solutions, I found an application note on TI Website about "Maida High Voltage Regulator" (floating regulator).

Now my questions:

On the schematic, Vin is 170Volts.  Can this schematic be used with much lower voltages (let's say 60VDC)
According to the schematic, Output current is 25mA but I need around 1 Amp.  Do I need to modify something to get 1 Amp output ?


texts: signal eye voltage level too high USB 2.0 Upstream near end

texts:
I am using the ‘Allion USB HS Device Electrical Test Fixture’ with a Lecroy oscilloscope (4 GHz, 40 GS/s) in order to make a USB upstream Near-End Signal Eye measurement (for High Speed Measurement).

The fixture connects via two 50 ohm identical coaxial cables, to the oscilloscope terminals.

The problem I am having is the following:

Even when testing with USB-Compliant devices, the voltage level of the device in the signal eye is too high or too distorted. This is not normal, since it should show without any points touching the red area.

An example of the signal eye I am getting is below:

Any help on the matter?


texts:
I have a quiz bell circuit electrically. When one bell is pressed, the LED will light and bell other will not work.

The problem is when bell is pressed simultaneously, then the other LED will also light as well. I've done a simulation by Multisim.

This is the project link
Quiz Bell

Can anyone analyze where the mistakes of this circuit?. Thank you


texts: What is the difference between "normal read" and "fast read" in the flash A25L032

texts:
The Flash A25L032 has a normal read mode and a fast read mode. It also has dual and quad read modes that are self-explanatory. However, the difference between the normal and fast modes is not at all clear.

What makes fast mode fast? since they both use a single MISO of SPI anyway? Their timing diagrams are below:

Fast read:


texts: How to infer pinout and winding ratio of this transformer?

texts:
Hi, I pulled this transformer from an EL wire inverter and am trying to figure out how to infer:

Which pins correspond to the primary and secondary coils
The ratio of the windings
Any other useful information I can glean.

There are only two markings on the top, none on the bottom. The top markings appear to be "45" on one side and, catty-corner to that, an "H". the pins on the bottom are symmetrically aligned, not offset like some transformers I've seen. I checked the resistance between pins and found:

Green-to-green: 70 ohms
White-to-white: 0.4 ohms
Green-to-white (side marked "45"): 1.0 ohms
Green-to-white (side marked "H): 68.6 ohms

...for background, I'm trying to implement the circuits described in Disney Research's "Tesla Touch" and "Revel" works (I can't add links because I don't have enough points). The papers call for a flyback transformer that boosts 3-5v to about 300v, which is significantly less than the voltages needed by other plasma- and arcing-related flyback projects I've seen online.

My understanding was that EL wire takes about 600v at similarly small currents, which is why I pulled the transformer from an EL wire inverter. However, I'm having trouble getting reliable performance from the transformer and am hoping with this question to resolve some fundamental questions I have about the component.

Thanks in advance for any help you can provide!

AKA


texts:
I'm trying to set up a comparator that goes high when the input is above 0V and goes low when the input is below -5V. I've used the datasheet equations to calculate the resistors for a non-inverting comparator dual supply (+/-12V) and -5V as Vref, but when I try to simulate it both in ltspice and circuit I just get a tiny echo of the input at the output. Is something wrong with my circuit?

Pinout of LM393 symbol is 1 = non-inverting input 2 = inverting input 3 = positive supply 4 = negative supply 5 = open collector output


texts: What is the difference between Vss and Vs in a transistor?

texts: I know the difference between Vdd and Vcc and all the other ones, but I can't figure this out. What's the difference between Vss and Vs?


texts: How hot should things be getting when I measure them with an ammeter?

texts: I recently got a little LED voltage and current meter and I've been playing around with it. When I hold down both of the current measuring leads to the battery, the negative terminal heat up significantly - to hot to touch! Since I've been testing lithium based batteries my guess is that the heat is due to the high current, or due to me messing something up, maybe even making a short circuit. Does anyone have any insight into why this could be?


texts: Combining decoupling capacitors for sensitive power requirements in LPDDR

texts:
I've been looking through a bunch of designs I found online on LPDDR2 interfacing.
What's always confused me is the parallel decoupling capacitors. Why have so many vs just combining that to what you want. Also how do you figure out what value you want for the total capcitance?


texts: Charging two lead-acid batteries connected in series, separately (with one solar panel)

texts:
I have 2 sets of 2 lead-acid batteries connected in series to produce 48V. They are powering an audio amplifier.

I'd like to be able to charge them with ONE solar panel. If I connect the output of the solar panel to both charge controllers, a short circuit occurs.

What can be done to make this possible?

I made a drawing to illustrate what I'd like to achieve.


texts:
I put a simple current source on a circuit to drive a UV LED with a constant current.

According to the LTSpice simulation setting 0 V at the signal input results in 0 A through the LED. But when I build up this circuit I get a non-zero current for 0 V. Ergo the LED is glowing. The inputs of the AD8616 are both almost zero (the feedback is a maybe 3 mV higher because of the small current going through the fb resistor). However the AD8616 drives 600 mV at the output. The noise floor on GND is quite high in amplitude (approx. 2 mV).

Can anybody explain this behavior?

EDIT: I replaced the opamp. Now I get a true 0. I can imagine, that if you leave the supply voltage connected, and you set a jumper to a new position (to switch to another input signal), the opamp drives much more than it should and dies.


texts: Motor Driver keeps dying/frying driving a worm gear motor

texts:
I am looking for some consultation about controlling a24VDC worm gear moto. I have blown 4 h bridge motor drivers thus far and while I have been trying to keep my project price tag low I may need to step up in quality but I want to make sure something else may be going wrong. I am a ME by trade but I remembered a smidgen about inductive loads and back EMF wreaking havoc on components. I have been using the following: driver 1 and  driver 2 to control the motor but they keep failing and at random times. This makes me suspect not my wiring but something else and possibly not protecting the components. My most recent board was working, next thing you know the ERR LED light is on and the manual says "ERR LED Indicator - Error LED Indicator, it will illuminate when fault detected in on board MOSFET driver."
I would think a motor driver board would know it would be dealing with inductive loads and protect against this but maybe I am wrong. Do I need to spend more money on someting like the following?
Help a poor ME sticking his toe in the water of electronics!
Thanks in advance!


texts:
I want my led strip lights to turn automatically off after 3 or 5 minutes of turning on.

Please, suggest a very simple circuit using capacitors which would block the circuit and turn off the LEDs continuously after 3 or 5 minutes.

Also, any problems to the capacitors in such case the circuit is blocked by the capacitors for long hours like 2 to 3 hrs.

Thanks in advance.


texts: Error on Uploading Program to ESP8266 via Foca v2.2 (USB to TTL Adapter)

texts:
BACKGROUND

To test the capability of uploading program to ESP8266,  I use an empty program with only a blank setup function and a blank loop function. The result showed me that there are a espcomm_sync error and a espcomm_open error. Any idea to solve this problem?

HARDWARE

PIN CONNECTION

  Foca v2.2 <-> ESP8266
        TXD <-> RXD
        RXD <-> TXD
        DTR <-> RST

Arduino UNO <-> ESP8266
        GND <-> GND
       3.3V <-> Vcc

PIN DIAGRAMS

Foca v2.2

ESP8266

ON LINUX UBUNTU 15.04

ON WINDOWS 10

REFERENCE

Bring IoT to Arduino, together [Getting Started] - http://www.arduinesp.com/getting-started


texts: Is there a female Phone Connector with 15A Contact Rating to match this male?

texts:
I've seen male phone connectors with seemingly very high voltage and contact ratings. For example the Switchcraft 188 which seemingly could operate at 240V with 15A.

Is this just incidental or are there female connectors with matching specs and legitimate use for a connection with those specs?


texts: Question regarding ground when using teensy to control a mosfet switch

texts:
Despite the fact that I'm pretty new to electronics I'm working on a quite ambitious project which is basically a USB-Midi Controller attached to different devices that send different signals. The common power source is a external 24V Battery which powers a pcb with two buck converters (5V 3A) and a USB Power Delivery controller. The latter powers a USB Hub which powers - amongst other devices - a teensy which is attached to and powers a PCB that mainly serves as user interface with different buttons and faders.

There are also two mosfets on this second PCB which are controlled by the Teensy and serve as switches between the 5V supplies and other devices.

I hope the following graphic will make things a little bit clearer:

I was wondering how to build the circuit of the mosfets. In my opinion it's not neccesary to connect Teensy GND and the buck converters ground since basically the minus of the 24V battery is the common reference potential, but people in a Teensy-related forum told me that I have to connect those two because otherwise there would be a chance that the 24V would roast my 3.3V only Teensy.

I don't fully understand this and I'm wondering if connecting them could lead to a ground loop since theyre connected at two points in the project.

I hope you guys can help me to get a deeper understanding of this matter. Thank you in advance!


texts: Derive DC motor formula with drum driving a conveyor belt

texts:
The setup is a DC motor directly connected via its shaft to a drum which drives a horizontal conveyor belt. There is a load of mass, M, on the conveyor belt.
I am stuck on trying to figure out what 'D' in the equation below means.

Title: Pulley, Conveyor Belt & Load system

Description: Load-Inertia to the motor consists of pulley (of radius r) and mass of load (M) on conveyor belt. The load-torque, to be delivered by the motor is given as:

where,

M is the mass of load on the conveyor belt.

r is the drum radius

ω = angular velocity

But i don't know what D means and i cannot figure out how that equation was derived in the first place. Any help would be much appreciated.


texts: Stability at loop gain <1 and 180 degree phase shift

texts:
I'm reading this article about stability of OpAmps: Link to article.

It says: "If Aβ is less than unity at the high frequencies where phase shift reaches 180°, the high-frequency phase-shifted signals will gradually fade away instead of progressively building up into major oscillations." This is depicted in the picture below.

However, I don't understand this. Shouldn't the system also be unstable at a loop gain less than 1? The 180 degree phase shift in the loop plus the subtraction at the summing point results in positive feedback (See figure 2 below).
This means that when a signal is fed into the system (at the control input) it will be attenuated by the loop gain and the phase will be shifted 180 degrees before it arrives back at the summing point. The control signal is still present at the plus input of the summing point so the two signals will be added up resulting in a greater signal than before. When the system keeps doing this the amplitude of the signal will rise to infinity and thus the system will also behave unstable.

My question: Is there an error in my analysis? Why is it that the system is stable at a loop gain < 1 and a phase shift of 180 degrees?

Figure 1

Figure 2


texts: Using polygon pours for small signals in PCB design

texts:
I'm trying to improve my PCB routing skills. When I started out a few years back, I just layed out the components and ran tracks with a fixed width between them. I didn't even know about polygon pours. Then when I started working with switching regulators, I started noticing the nice polygon shaped traces i.e. TI uses in their datasheets for layout recommendations, to optimize for current flow. So I copied that and started working with power and GND planes and/or polygons. So basically most of my power paths in my designs are now built out of polygons instead of traces. It looks kind of neat.

But now in this current design I'm doing I'm starting to wonder why I shouldn't do more or even just all of my connections using polygons. It allows me to make nicer transitions between different pad sizes, keep better control over where my ground pour goes etc. while electrically speaking it probably doesn't have any added value. In wonder if this is good or bad practise from layout and/or manufacturing point of view.

Here's an example. It's a 2-layer board so I don't have the luxury of a power plane. The highlighted trace is my power net which is a big fat polygon. But I also used wide polygons to connect the 4 0402 resistors in the center to the large pads of a WiFi SoM on thew right (ESP). They could be tiny 6 mil traces like RXD and GPIO0 on the right, but somehow it 'feels' better to make the trace as wide as the pads they connect to. What is good practise for low power signals? Or is it just a matter of taste?

This also makes me wonder about the ground pour. Is it a benefit to have ground pours sitting between those pads or would it be better to even make the polygons larger to keep the pour from creeping between my signals polys? And what do I do with the ground pour creeping between the pads of the 4 0402 resistors in the center, is that good or bad?

-- edit--

Updated the layout have less chance of tombstoning. I guess I could also enable thermals on the polygons in places I need big traces in and small traces, out right?


texts:
I am new to VHDL and tried to implement a simple example from a book, what
represents a 2bit register and the testbench.

Compiling the files works well, and signals the stimulate the register (reset, clock and data) are correctly transmitted from the testbench to the register.

But the assignment of internal signals to any value remains without any action, thus there is also no output.

I tried to simulate it with ModelSimPE Student Version and Xilinx Viacom Webpack edition 2014.3 .

In both IDEs I included the files, and they compile without any errors.
q0_s, q0_ns, q1_s, q1_ns will not change their values, and thus there is no output.

Can anyone tell me, what is wrong with my code?

The 2bit register

LIBRARY ieee;
USE ieee.std_logic_1164.all;

ENTITY reg2 IS
    PORT (
        clk : IN  std_logic;
        d0  : IN  std_logic;
        d1  : IN  std_logic;
        load: IN  std_logic;
        res : IN  std_logic;
        q0  : OUT std_logic;
        q1  : OUT std_logic
    );
END reg2;

ARCHITECTURE beh OF reg2 IS
    SIGNAL q0_s, q0_ns, q1_s, q1_ns : std_logic;
BEGIN
    reg : PROCESS (clk, res)
    BEGIN
        IF res = '1' THEN
            q0_s <= '0';
            q1_s <= '0';
        ELSIF clk'event AND clk = '1' THEN
            q0_s <= q0_ns;
            q1_s <= q1_ns;
        END IF;
    END PROCESS reg;

    q0 <= q0_s AFTER 2 ns;
    q1 <= q1_s AFTER 2 ns;

    mux : PROCESS (load, q0_s, q1_s, d0, d1)
        BEGIN
            IF load = '1' THEN
                q0_s <= d0 AFTER 3 ns;
                q1_s <= d1 AFTER 3 ns;
            ELSE
                q0_ns <= q0_s AFTER 4 ns;
                q1_ns <= q1_s AFTER 4 ns;
            END IF;
    END PROCESS mux;

END beh;

Testbench

LIBRARY ieee;
USE ieee.std_logic_1164.all;

ENTITY test_bench IS
END test_bench;

ARCHITECTURE reg2_test OF test_bench IS

    COMPONENT reg2
        PORT (
            clk : IN  std_logic;
            d0  : IN  std_logic;
            d1  : IN  std_logic;
            load: IN  std_logic;
            res : IN  std_logic;
            q0  : OUT std_logic;
            q1  : OUT std_logic
        );
    END COMPONENT;

    -- stimulus signale
    SIGNAL s_clk  : std_logic := '0';
    SIGNAL s_d0   : std_logic := '0';
    SIGNAL s_d1   : std_logic := '0';
    SIGNAL s_load : std_logic := '0';
    SIGNAL s_res  : std_logic := '0';

    -- response signale
    SIGNAL q0_r : std_logic;
    SIGNAL q1_r : std_logic;

    -- Verschaltung des DUV mit den Stimulus/Response signalen
    BEGIN

    u1 : reg2
        PORT MAP ( clk => s_clk, d0 => s_d0, d1 => s_d1, load => s_load,
                res => s_res, q0 => q0_r , q1 => q1_r);
    -- Taktgenerator ( 100MHz )
    s_clk <= NOT s_clk AFTER 5 ns;

    -- Stimuli
    stim : PROCESS
        BEGIN
            s_res <= '1', '0' AFTER 20 ns;
            s_d0 <= '1' AFTER 20 ns;
            s_load <= '1' AFTER 40 ns;
            WAIT;
    END PROCESS stim;

    -- Abbruch der Simulation
    stop_sim: PROCESS
    BEGIN
        WAIT FOR 100 ns;
        ASSERT false  REPORT "simulation stopped" SEVERITY failure;
    END PROCESS stop_sim;
 END reg2_test;


texts: Serial communication between raspberry and laptop not giving right values

texts:
I want to communicate between a Raspberry Pi 3 model B and a laptop using a USB to RS-232 cable and this RS-232 to 3.3V TTL converter via the serial module in Python:

GND is connected to board pin #6
3.3V is connected from board pin #2 to VCC
Rx is connected to board pin #10
Tx is connected to board pin #8

The code I'm executing in the Raspberry is the next one:

port = serial.Serial("/dev/ttyAMA0",\
    baudrate=9600,\
    parity=serial.PARITY_NONE,\
    stopbits=serial.STOPBITS_ONE,\
    bytesize=serial.EIGHTBITS,\
        timeout=3.0)

port.write(b'hello')

And the code I'm executing in the laptop is the next one:

ser = serial.Serial(
    port='COM11',\
    baudrate=9600,\
    parity=serial.PARITY_NONE,\
    stopbits=serial.STOPBITS_ONE,\
    bytesize=serial.EIGHTBITS,\
        timeout=1)

line = ser.read_until()
print(line)

The problem is that in the laptop I receive the next sequence on bytes, and those change depending on an unknown factor:

b'\xd0)\xe1\xd3\xf7'
b'\xd0+\x13\xd7\xf7'
b'\xd0+\xe3\xe1\xf9\xff'
b'\xd0+\xe1\xe1\xf3'

Does anybody have an idea why this is happening? Any help is really appreciated

EDIT: ESD discharge magically solved this issue (I think)
I was checking if I made the right connections in the Raspberry Pi and accidentally touched some of the pins in the board and received a shock. I really feared that this damaged the Raspberry, but everything seemed ok. After this event I run the program once again and received the right bits every time. I think that this is scary, especially because I didn't intended to damage my board with an ESD.
Is this assumption true? I didn't modify anything to any program O_O


texts: Circuit for generating a PWM signal of varying high and low voltage values

texts:
I have a microcontroller that is generating a PWM signal between 0 and 12V of varying frequency. I'm looking to build some sort of circuit that will take this signal and then attenuate the high and low values of that square wave to be anywhere between 0 and Vmax (12V in this case). The trick here is that the low signal may need to be higher than 0V, so it can't just be a voltage divider on the square wave.

I would guess that this would use some sort of potentiometer or maybe even a variable op amp, but I'm a software guy and don't know what I'm doing. :)

Basically I want to be able to generate high and low voltage values of my choice while still retaining the frequency and duty cycle. Ex. 250mV-500mV, 3V-5V, etc.

Any ideas where to start, or what a circuit for this would look like? Please comment if more information is required.


texts:
On my 3D printer(cube)'s cartridge there is a chip with only two pins. The 3D printer can through those 2 pins tell how much plastic it's left in the cartridge.

My question is:
How can a chip power up, recieve, send information with only 2 pins?


texts:
The WM8804 looks like the ideal candidate for a design I'm working on --- this single chip could replace the need for one receiver and one transmitter.  The specific routing requirements are:

I need one of the following two configurations, selectable "on-the-fly", during operation (say, a switch that a microcontroller reads, and the microcontroller uses GPIO pins to control and reconfigure the WM8804):

I2S input → route to SPDIF output
SPDIF input → route to both I2S output and SPDIF output

Table 15 on page 20 and Figure 15 on page 20 of the WM8804 datasheet suggest that it can do that: TXSRC selects the source for the SPDIF transmitter;  the diagram in Figure 15 shows that the output of SPDIF RX goes to both the I2S and the SPDIF transmitter;  if I set, in hardware/standalone mode, CSB = 0  (corresponding to TXSRC = SPDIF RX), the multiplexer will select SPDIF RX as the source for SPDIF TX, but SPDIF RX will also go to the I2S decoder and ultimately DOUT.

I have had enough ugly surprises with datasheets' misinformation (or hidden information, especially about limitations of the device) that I'm paranoid enough and would like to ask:

Anyone out there has tried this or similar configurations with the WM8804 and can confirm that this is the case?

In case this makes a difference: please notice,  although I'll have a microcontroller on the same board, I really, really prefer to use the WM8804 in standalone/hardware mode;  even if the microcontroller will drive the few pins that the WM8804 will read at startup to determine its configuration.


texts:
I'm trying to understand signal resolution, so therefore I am looking for a more clearer explanation.  Primarily signal resolution is linked to an Analog-Digital converter.

Quoting from new electronics, http://www.newelectronics.co.uk/electronics-technology/whats-the-difference-between-resolution-and-accuracy/73740/, states:  “The resolution of an A/D converter is defined as the smallest change in the value of an input signal that changes the value of the digital output by one count.”

In addition, I have read many more unclear definitions.  Specifically, what is signal resolution?


texts: Replacing Lithium batteries with larger ones

texts:
I have some background with electronics, but that was in the "old days", so my knowledge of lithium battery types and charging processes is very limited.

I have a bunch of gadgets with one of those baggie-type lithium batteries. Some of them are size/weght restrained, but with a couple, size is no issue, so i was wondering if I could replace the provided battery with a (lot) larger ones. Those gadgets also have charging circuits (i've read the charging is voltage-controlled, so in theory, the capacity shouldn't matter for the charger, atleast in theory). All batteries are single-cell.

So, is this possible at all, and what should I be extra careful about, when selecting batteries (eg. when ordering cheap large ones from ebay), and what are the limitations?


texts: How to hold a data during N clock cycles using DFFs?

texts:
I want to hold a data during N clock cycles using posedge sensitive DFFs.
The timming diagram would look like:

What will be the equivalent circuit?

Thanks


texts: How do I interpret this thermal curve graph for my heatsink?

texts:
Datasheet of heatsink.

The heatsink says it's thermal resistance is 24K/W.

Let's say my device dissipates 5 Watts. Assume a perfect conduction from the case to the heatsink, and junction to case is 0K/W.

If I use the specified value, the heatsink should rise 120K above ambient. However, from the graph it says it will be about 96K above ambient (unsure which curve is correct).

Further, how do I interpret the effect of forced air cooling according to the graph?


texts: Is there an adjustable voltage converter that could take an input of 18 volts to a 0-18v and handle an amp draw of 20 to 30 amps?

texts: Trying to change a power tool from a 9.6 v 3.3 ah nimh battery to an 18v 5 ah lithium Milwaukee battery


texts:
I was asked to design a FSM for outputting x/3 without the remainder.

This should be implemented using a synchronous system defined as follows:

input: on each clock cycle t, one bit x[t]

output: on each clock cycle t, one bit y[t]

functionality:

let x be a number represented by concatenation of the input bits where x[t] is the LSB

let y be a number represented by concatenation of the output bits where y[t] is the LSB

so y is the result of x/3 (the floor function with x/3 as argument)

e.g.:

t 1 2 3 4

x[t] 1 0 1 0

y[t] 0 0 1 1

I am including two attempts, yet neither is actually yielding the correct result but rather the remainder (i.e. x mod 3), right? They were both intended to yield x/3 and yet it seems they both yield the remainder instead.


texts: How to measure battery voltage from a microcontroller

texts:
Today I had an interview, there they asked me, if given a microcontroller and Battery then how do you measure the voltage level. Write the steps from scratch with pseudo code.

How can this be done?


texts: What is the purpose of diode in parallel with the resistor divider in MOSFET gate driving circuit

texts:
I have built several 200W AC dimmers using Microchip 8-bit CPU and the illustrated back-to-back MOSFET circuit.

I have seen on Internet schematics with the D1 diode in parallel with the R1 resistor, or without.

Assuming it should be a regular diode (tried 1N4148), I connected a diode and compared it on oscilloscope, but did not see any difference.

Can anyone tell me, why to use a diode at that location?

Update: with 200W load of 4 pieces of 50W bulbs, without the diode we often destroy the MOSFET, pretty much immediately after first power-on (transistor becomes short). With the diode, it seems to work even after many hundred power-ons.

simulate this circuit – Schematic created using CircuitLab


texts:
I'am trying to build a drone. Therefore I bought some brushless DC motors

This is the only specs I have for the motors :

- Max Efficiency Current: 4-10A (>75%)
- Current Capacity: 12A/60s
- No Load Current @ 10V: 0.5A
- No. Of Cells: 2-3 Li-Poly
- Motor Dimensions: Φ27.5 x 30mm
- Shaft Diameter: Φ3.17mm
- Weight: 48g

The problem is that when I try to power them, they won't spin.
I'm using a 9V battery.

Any idea why ? I think the battery might be to weak.

Also, I'm a french programmer willing to expend his knowledge, so I have very little skills in electricity and electronics in general. If you could explain like you would to a child that would be a plus. :)


texts: Transmitting audio over variable voltage DC power line?

texts:
I have multiple generators that are producing a variable DC voltage between 0 and 18volts each that are being sent to an inverter for an AC output used to power various devices.

I really need to be able to transmit an audio signal back to each of the generators, and would really like to avoid having to add additional wires. Would it be possible to piggyback an audio signal of a usable quality over these variable DC lines?

I've searched around and suspect this answer might be appropriate, but they're mostly talking about communication signals, and I'm not sure if the required fidelity for an audio signal would be possible. I'm also not sure the effect a highly variable DC voltage would cause.

Thanks


texts: step down 9V AC to 6V AC without transformer

texts:
I've a circuit that I need to supply with an input voltage of 9V AC as well as an input voltage 0f 6V AC. Both are for a regulated power supply with one rail supplying 5V DC (from 9V AC) and the second rail 3.3V (from 6V AC). The load on the 3.3V DC rail is a crystal oscillator.

I've a transformer 220V to 9V AC, wasn't able to find a transformer that has two secondary windings for those exact voltages (yet) and I don't have space in the enclosure to mount a second transformer. Is there a way to derive 6V AC from the 9V AC secondary? What I've been able to find so far applies to stepping down DC voltages or did require a transformer.

TIA!


texts:
I am trying to create a circuit that will be able to detect a touch (with fingertip) on a metal/aluminium surface that it is connected to. Currently I have this circuit (I am sorry for bad drawing...):

My assumptions are probably wrong, but this is what I was thinking of. Due to human skin having some capacitance, when one would touch the plate, there would be some current flow due to change in capacitance. High pass RC filter would get rid off DC offset and the signal would get amplified by LM358. This would then trigger 555 timer in monostable mode.

Any help is greately appreciated!


texts: Question regarding chinese voltmeter ammeter module

texts:
I am new to this forum. I am a Diploma in Electronics from India and a passionate DIY hobbyist too.
I have a question regarding cheap 10 amp ammeter and a voltmeter module I bought off aliexpress.
I am building a variable DC PSU using a 24 volt 10 ampere SMPS as the main power source and feeding its output to a cheap XL4016E1 based buck converter which has CC CV Control. I have done all connections right and the PSU works fine on 230 V AC. Now I want to run the buck converter on external DC input (I have installed protection diodes to prevent clashing of the SMPS output with the external DC input)  and was wondering whether the voltmeter ammeter module will need an isolated DC DC converter module to power it up to prevent damage to it while I run the entire PSU on external DC input, or should I simply think of installing a 9 volt battery to power the voltmeter ammeter separately and activate battery power only when external DC supply is detected at the DC jack by using a relay.
PSU Photo 1
PSU Photo 2


texts: Inrush Surge Limiter [NTC Thermistor] on Primary or Secondary side of Linear Power Supply

texts:
In designing a linear power supply, I understand I need to limit the inrush surge current on cold start, to charge up the large bank of filter capacitors, post-rectifier.
However, my original intent was to connect the transformer directly to the power entry module/fuse/breaker without a PC board in the path. Only the secondary stepped-down side would have a PC board and therefore could accommodate a thermistor.
Does it matter whether the NTC Thermistor for inrush current limiting is connected to the primary mains voltage or secondary winding of the transformer [before rectifiers]? My initial intuition is no, since they are proportional in current anyways, and limiting one winding will naturally limit the other.


texts: This circuit uses a transformer on a rectified DC voltage, what purpose does this serve?

texts:
I am trying to design a USB charger from scratch, and I have come across this schematic in the data sheet of a AC-DC converter that I would like to use (NCP1011):

Unfortunately the circuit does not have any values, but it looks like there is a transformer (with reversed polarity on the output) on the rectified DC output. Page 17 of the datasheet reveals that if you wanted a 12V output with a 120V rectified voltage, then you should use a transformer ratio of 1:0.1. So the transformer ratio is the same as if it were AC. Since I want 5V output, and I am using 240V (Australian mains power), the rectified voltage will be around 240Vdc, so I will use a transformer with a ratio of 1:0.02.

Also, why is the polarity reversed on the transformer? If the transformer is only converting the ripple, then why would you want that to be negative?

EDIT: Just realized a miscalculation. Australian mains will be closer to 339V (240 * sqrt(2)) after it is rectified, so my transformer would be something 1:0.014 (if such a thing exists)


texts: Current sensing at μA accuracy and ADC nonlinearity

texts:
Project context
A battery-operated positioning device sends location information through GSM at regular intervals. Between the fixes, the device is in low-power mode. The battery is supposed to last months or even years, hence the importance of power consumption. I need to design a high-side current monitor to measure the current drawn from the battery and graph it on a computer, so that we can optimize the frequency of fixes vs power consumption.

Measurement requirements
(renegociated after the first draft, which was IMO unrealistic)

range 0 A to 1.5 A
resolution <= 1 μA
accuracy <= 1 μA
output data rate >= 1 kHz

Hardware requirements

high-side current shunt, the voltage across the resistor is measured by an INA
the INA's output voltage is converted by ten 32-bit ADC in parallel, each one sampling at 100 Hz
the ADC data is retrieved by an MCU, which sends the data through USB
the measurement device has its own battery and the USB is isolated
the PCB is supposed to be temperature-regulated, to minimize the thermal effects on the gain and offsets

Hardware selection
The shunt resistor is a four-terminal Vishay 100 mΩ, 1 % tolerance, 1 W. The INA with the best noise performance that I could find is the AD8429. There aren't that may 32-bit ADCs available, so the choice was easy (ADS1262). The power supply for the various components is purely LDO-based (to avoid the switching noise of switching regulators), and again I chose the LDOs with the best accuracy and lowest noise that I could find. The ADC's reference voltage (5 V) is also ultra-low noise.

Test board
I designed a PCB with the 100 mΩ sense resistor, the INA amplifying x28.2 (so output voltage 0 V - 4.25 V) and only one ADC sampling at 100 Hz. Looks like that:

Again, the supply/ground of the DUT and that of the current sensing circuit are isolated (the INA's supply isn't shown for simplicity). The 1 MΩ resistors are here to provide a path for the bias currents, but I'm not sure if the value is adapted.

At first glance, the system works fine, although the requirements aren't met (unsurprisingly). As a first test, I calibrated the INA+ADC chain (offset with shorted inputs, gain with a 1.5 A input current) and generated a current from 0.1 A to 1.5 A by 0.1 A steps through the measurement resistor. This current was also measured by a tabletop DMM (Agilent 3606) as a ground truth. For each current step, I recorded 100 samples of the ADC's output, synchronized with samples from the DMM (oversampled since it doesn't go as fast as the ADC).

Result of the first test
For each current step, for each of the 100 samples, I computed the absolute error \$|I_{DMM}-I_{ADC}|\$. Then took the average error over the 100 samples, to get one error per current step. Results are below.

It's not legible here but the error at 1.5 A is about 40 μA. The farther we get from 1.5 A, i.e. the calibration value, the worse the error. At 0.1 A input, the error is more than 20 % (5.4 mA). I think this is orders of magnitude larger than what could be explained by the ADC's nonlinearities. The INA isn't the problem, I measured its output voltage over the measurement range and the amplification is linear. I have no clue why the ADC becomes linearly less accurate for smaller input currents.

Questions
I have questions about the ADC's behavior but also about the system design in general, which I'm not satisfied with. I read this and I think I'm more or less in the same situation -- insufficient practical experience and unrealistic requirements.

Are the requirements too ambitious?
Is the 32-bit ADC overkill?
I have nearly zero practical experience of PCB design, all I know is
self-taught. Getting a bunch of expensive components, throwing them
on a beginner-level PCB and hoping that it's going to work fine is
bad design practice, right?
Why is the ADC less accurate for smaller
input? I'm starting to wonder if this calculation even makes sense,
but now I'm stuck.


texts: I know what a Reset signal is, but a Set/Reset signal? Isn't that impossible?

texts:
A schematic by Lattice Semiconductor includes the diagrammed D flip-flop. This D flip/flop accepts, among others, a Set/Reset signal.

I would have understood a Set signal. I would have understood a Reset signal. I would even have understood Set and Reset signals on separate lines. I cannot, however, understand a joint Set/Reset signal.

  -------------------
  |                 |
--| D             Q |--
--| CLOCK ENABLE    |
--|>CLOCK           |
  |                 |
  |    SET/RESET    |
  ------------------
           |

QUESTION

What is a Set/Reset signal, please?

ADDITIONAL INFORMATION

For optional reference, here is the data sheet (1.5 MB) in which the D flip-flop appears, in Figure 3.2, page 9. I do not, of course, ask you to go to read a 52-page data sheet for me! (That would be my homework, not yours.) Therefore, the relevant quotes from the data sheet as far as I know are as follows.

  Each logic cell includes ... a D-style flip-flop (DFF), with an optional clock-enable and reset control input.... [Sect. 3.1.1, page 9.]

  ... Signal description [is as follows].

  Function: input.
  Type: control signal.
  Signal name: Set/Reset. (Footnote: if Set/Reset is not used, then the flip-flop is never set/reset, except when cleared immediately after configuration).
  Description: Asynchronous or synchronous local set/reset shared by [a block of eight logic cells, each cell including a flip-flop]. [Table 3.1, page 10.]

One can externally disable the Set/Reset signal, presumably via multiplexing or high-Z pull-down, but I see nothing to decide whether the Set/Reset signal—when not disabled—should set the flip-flop or reset it.

Am I missing something?

If you know what a Set/Reset signal is, would you tell me?