texts: c2000 microcontroller sensorless speed control implementaion

texts: I want to know some detail about TMS320F28335 TI microcontroller for sensored and sensorless speed control of SPMSM. I have implemented the MATLAB simulation and the model is working well but for microcontroller I am getting problem how to introduce the interrupt.


texts: I was studying for my Design of Analog Circuits course and I have two questions about this ADC. If someone can explain me why in the figure below in the Pipeline Analog to Digital Converter, why Vin is compared with Vref/2 instead of Vref and why after doing the summation, the result is multiplied by a gain of 2? What does that has to be with functionality of the ADC.


texts: how to design a pattern detector state machine in vhdl

texts:
How can I use vhdl to design a sequence detector to find a 32bit sequence with 15 zeros followed by 17 ones by using 2 counters to count ones and zeros that have enable and reset signals.
Can anybody give me some clue or draw a fsm chart.


texts:
ngspice is not capable of performing a DC analysis while sweeping transistor length. I'm trying to do a workaround by creating a vector, looping through it, and altering @m1[l]

Here's a minimal working code:

VA 4 2 DC 0
VSBN 0 3 DC 0
VGSN 1 0 DC 1
VDSN 4 0 DC 1
M1 2 1 0 3 nmos w=200n l=45n

.control
compose length start=100n stop=500n step=1n
foreach l length <-- ??? not sure about this
  alter @m1[l] l <-- ??? not sure about this, too
  dc VGSN 0 1 1m
end
.endc

Is there some way to loop through a vector in ngspice?


texts:
Consider that an SPI has more slaves.

Suppose if more than one Slave wants to communicate with Master simultaneously then How does an SPI react in that situation? by means of priority or any other means?

If it is by Priority means, then it will be done by Hardware or Software and How?

And also, Can SPI (Master) be able to Communicate with more than one slaves simultaneously?

Please do clarify me. I am novice to SPI.


texts:
Does the Arduino chip get wiped of any (uploaded) code when you press the reset button?

and

Can you retrieve the code that is currently on the chip?


texts: What is the physical meaning of negative resistance?

texts:
I am a bit confused about the physical meaning of negative resistance.

Mathematically, a component which has negative resistance shows a decreasing voltage across its terminal when the current inside it grows, and vice versa. But how is this physically possible?

Somewhere I have read that an example of component with negative resistance is a voltage source. But I do not understand this statement, since a voltage source is a component which at most shows a (positive) internal resistance.


texts: Mixing Symfonisk high/low-mid output channels

texts:
So i've been messing with this issue for a couple of months and it's just that my electronics knowledge isn't reaching far enough.

I have a Symfonisk speaker by Ikea, which outputs a low and high/mid signal to two internal speakers which I want to connect to two ceiling speakers.

As said, the DAC (TI PCM5101A) is in a high/low channel setup which outputs two. My first thought was to just cross/combine the channels. But that shorts the DAC and shuts down. Lesson one learned.

After search a bit further i found that i could combine the channels by by-passing the capacitors: https://www.diyaudio.com/forums/digital-line-level/349202-getting-audio-signal-ikea-symfonisk-sonos.html

I tried this method and was surprised to hear a great sound coming out of my speakers. But all until the system tried to deliver some low. The sound gets muffled and a bit numb when there is some bass in the the track. Sounds like side-chain compression. Not sure why.

So my second option would be some sort of passive mixing circuit, where i simply combine the channels in a single mixed output. But I'm not sure how to approach this since 'combining' the channels does make the DAC shutdown.

What would the right approach be?


texts:
I have developed an Android app which talks to an Arduino Mega through USB.

The C code is 1.8kb and will fit on an ATTiny85 chip in order to shrink the circuit to almost nothing. The problem is...

How do I introduce USB to the circuit so I can still talk to it with the Android app?


texts: Sending IR signals to Robosapien using Arduino

texts:
I am trying to send commands to a Robosapien (first generation) using an IR LED hooked up to an Arduino. I have seen web pages on attaching a microcontroller directly to the toy, but what I want to do is just send commands via IR.

I found an article by K. Smith that mentioned that the IR commands sent by the Robosapien remote take the following form:

To send the hex code 85:

  The IRout signal is held high until a signal is sent. Then a string of
  five zeros is sent to signify a command is coming. Then the hex code
  is sent but instead of sending a ‘1’ a ‘1110’ is sent and rather than
  a ‘0’ a ‘10’ is sent. So $85 looks like this:

Binary:     1    0  0  0  0  1    0  1
Robosapien: 1110 10 10 10 10 1110 10 1110

So I tried the code below:

int bitTime=833;
int IROut =  4;

// The setup() method runs once, when the sketch starts

void setup()   {
  // initialize the IR digital pin as an output:
  pinMode(IROut, OUTPUT);

  Serial.begin(9600);
}

void test()
{
  // output high
  digitalWrite(IROut,HIGH);
  delay(1000);

  // 5 zeros
  digitalWrite(IROut,LOW);
  delayMicroseconds(bitTime);
  digitalWrite(IROut,HIGH);
  delayMicroseconds(bitTime);
  digitalWrite(IROut,LOW);
  delayMicroseconds(bitTime);
  digitalWrite(IROut,HIGH);
  delayMicroseconds(bitTime);
  digitalWrite(IROut,LOW);
  delayMicroseconds(bitTime);
  digitalWrite(IROut,HIGH);
  delayMicroseconds(bitTime);
  digitalWrite(IROut,LOW);
  delayMicroseconds(bitTime);
  digitalWrite(IROut,HIGH);
  delayMicroseconds(bitTime);
  digitalWrite(IROut,LOW);
  delayMicroseconds(bitTime);

  // send 1110 10 10 10 1110 10 1110

  // 1110
  digitalWrite(IROut,HIGH);
  delayMicroseconds(3*bitTime);
  digitalWrite(IROut,LOW);
  delayMicroseconds(bitTime);
  // 10
  digitalWrite(IROut,HIGH);
  delayMicroseconds(bitTime);
  digitalWrite(IROut,LOW);
  delayMicroseconds(bitTime);
  // 10
  digitalWrite(IROut,HIGH);
  delayMicroseconds(bitTime);
  digitalWrite(IROut,LOW);
  delayMicroseconds(bitTime);
  // 10
  digitalWrite(IROut,HIGH);
  delayMicroseconds(bitTime);
  digitalWrite(IROut,LOW);
  delayMicroseconds(bitTime);
  // 1110
  digitalWrite(IROut,HIGH);
  delayMicroseconds(3*bitTime);
  digitalWrite(IROut,LOW);
  delayMicroseconds(bitTime);
  // 10
  digitalWrite(IROut,HIGH);
  delayMicroseconds(bitTime);
  digitalWrite(IROut,LOW);
  delayMicroseconds(bitTime);
  // 1110
  digitalWrite(IROut,HIGH);
  delayMicroseconds(3*bitTime);
  digitalWrite(IROut,LOW);
  delayMicroseconds(bitTime);

   // output high
  digitalWrite(IROut,HIGH);
  delay(1000);
}

void loop()
{
  test();
}

But unfortunately I am not getting any response from the Robosapien. What am I doing wrong?


texts: How can I get the graphic of the a resistor-diode circuit's ID-VD graph?

texts: I have tried the following but I am not sure if it is correct or not. How can I be sure?


texts: Definition of the offset voltage for a single-ended op-amp

texts:
Let's consider an op-amp:

The book I'm reading says that, ideally, if the voltage difference between the two inputs is zero (thus vin1=vin2) then the output voltage should be zero. However, because of mismatches in the circuit implementation at the transistor level, even if the input differential input is zero, the output will be different from zero. Thus a voltage, called the offset voltage, must be applied between the two inputs in order to really set the output voltage to zero.

Another book I'm reading considers the following fully differential circuit:

Ideally, if v1=v2, then the output differential voltage vo is zero. In reality however vo is not zero because of mismatches; the book calculates then the value of the offset in order to have the differential output voltage equal to zero.
In every case, the author of the book is consistent with the definition of offset voltage: he wants to set the output differential voltage to zero, accordingly to the definition

Question: if I have a single-ended output voltage, how do we define the offset voltage? Let's consider the following two-stages op-amp:

If I rigorously apply the definition of the offset voltage, I should find that voltage which, applied between the two inputs, sets the voltage of the output node to zero. But this would be meaningless: I must indeed have necessarily a dc voltage different from zero at the output node, otherwise the circuit for sure will not work!


texts: Multi channel isolated barrier: how to tell if inputs are isolated from each other?

texts:
I've been trying to figure out if in multi-channel isolated barriers the inputs are isolated from each other. For instance consider the following 2 channel isolated loop repeater:

http://files.pepperl-fuchs.com/selector_files/navi/productInfo/edb/072149_eng.pdf

The datasheet says nothing about inputs being isolated from each other but there is this image on page 2:

Does this image mean the inputs are isolated from each other (as well as the outputs) or not?


texts: Bluegiga BLE112-A: able to program, but unable run see

texts:
I tried to get Support from Bluegiga directly, but I didn't get an answer (despite the fact that their Zendesk is nearly unusable):

I'm using a BLE112-A on our board:

I've been able to flash my BGScript with the CC Debugger onto the chip, but I can't see it appear in a Bluetooth monitoring app. Flashing the same script onto the development board will show up the chip immediately.

Here's the flash tool's info output from the chip:

I've checked the docs already, but I cannot see the cause. I've tried it with two of my boards. Any ideas?


texts: What is mean by Differential Daisy Chain UART?

texts:
What is mean by differential daisy chain UART? And what is the difference between UART and differential daisy chain UART?

While reading datasheet I come across this concept if anybody knows then I would like to know it.


texts: How can 12ma illuminate 3 LEDs in series as brightly as 48ma can illuminate 3 LEDs in parallel?

texts:
I have a 16ma 9volt current source which I connected 3 LEDs to in series.  I measured the current flowing through the positive terminal and it was 12ma.  Next I connected 3 LEDs to separate 16ma 9volt current source.  I measured the total current and found it to be 48ma.  All the LED brightness were very similar.

I am assuming that the brightness is a function of power (watts) and that as the power increases, either the voltage or the current must go up.  If the voltage stays the same (9 volts) and the current increases by a factor of 3, then the power (total LED brightness) must increase by a factor of 3.  However, this is not the case.  Maybe there is a heat factor that I am not considering.

How can 15ma illuminate 3 LEDs in series as brightly as 36ma can illuminate 3 LEDs in parallel?


texts: Are large electrolytic capacitors necessary in a servo system that doesn't need to be precise

texts:
I have two servos in an autonomous sail boat. One controls the rudder, the other the winch. I try to use both sparingly to minimize power consumption, and so I disconnect each unused servo through an n-MOSFET, and additionally, when neither are in use, I put the power regulator to sleep. Here's the circuit diagram:

I added the large caps based on recommendations from the interwebs to reduce "jitter," but given the fact that keeping a fixed position isn't really important here, are the caps doing anything besides effectively wasting energy? What I see when I scope the system is that when I power down the regulator, the caps discharge within a few seconds, meaning the power is wasted somewhere.


texts:
I recently took an undergrad computer architecture course and had a question about using multiple cores after seeing how dense the field of research is. I am thinking about a general idea of how many cores can be used adaptively to accomplish both very parallelizable and not-really parallelizable tasks without relying on the OS too much.

So my question is: Given they can share the same data and I/O buses and the same registers, could there be an architectural design where multiple processing units go through one set of instructions by switching between units?

For example, assume you had two processing units being fed two different clock signals 180 degrees out of phase. Could one unit process an instruction during its clock high and then the second unit process the next instruction during its clock high (the first unit's clock low)? So unit 1 would do every odd instruction and unit 2 every even.

Here's a rough diagram of what I mean by the two clocks being used together.

Is this doable, or am I missing something? I couldn't really find much about this on the web or SE since I'm not really sure what keywords to use for this question.

I'm basing all of this on my understanding of the LC-3 architecture, though it's a little outdated and may not reflect modern-day architectures.


texts: Why does probe request signal varies significantly in the same second?


texts: Can anybody tell me whether the colour of the Solder Resist on a PCB makes any difference when using AOI equipment to recognise the components placed on it??


texts: Charging battery using computer power supply?

texts:
I have new 600W ATX computer power supply unit.
I have wired green and black together to make power supply turn on when plugged in.
I wanted to charge my 12VDC empty battery, without dealing damage to it "or overheating it using a PSU".
I do know ATX PSU color codes (black = ground/0V, orange = 3.3V, red = 5V, yellow = 12V).
I saw some people used controller to "limit the transmission."
I don't want to damage my battery or either PSU for future use.
Since I don't have multimeter...
EDIT: I forgot to mention that I wired yellow (12V) from PSU to "+" on the battery, and black (ground/0V) from PSU to "-" on the battery.
Question: Have I done it right?


texts: Phasors of power supply Vs1 in one example

texts:
I read one example in my note:

If \$V1=1=+j2\$ and \$V2=12+j12\$, phasor of power supply Vs1 is: \$29+j59\$, but I couldn't get it. I think it's wrong and the solution is \$29+j57\$. Could anyone help me?


texts: How to create a regulated 5V power supply from an unregulated 5V power supply

texts:
I have a project that involves a specific single board computer* and several hundred WS2812B "smart" RGB LEDs*, all running from a 5V supply.

I have a 5 volt 15 amp unregulated power supply. While the LEDs are okay with an unregulated power supply the microcontroller I am using tends to have issues when the voltage is not steady.

Since I want to run it all from one power source I would like to create about 1 amp of regulated 5V power from the unregulated 15A 5V source.

I want to build this power converter onto a PCB, so I am looking for a design I can implement and not a pre-made board. My final design will be a Pi hat, that is it will clip onto the Pi's GPIO ports and sit on top.

This will all be soldered manually(through hole or surface mount) so ideally it will not involve more parts than needed. This is a one off so while cost is a concern I am not trying to save pennies.

What type of power converter circuit could I build onto my board that can do this? Converting only 1 amp will I encounter significant heat issues?

I am not asking anyone to design this for me, rather point me in the correct direction.

*The WS2812B is an 'intelligent' serial data controlled LED RGB light source integrated in a 5050 package. Connections are digital serial in and out plus 5V & ground. pins. It also include a precision internal oscillator and (internally generated ) 12V constant current drive. Devices are series chained (Dout to next Din) allowing up to 1024 devices and a 5 metre long string on a single series connection.
 For more details see the data sheet here

*Raspberry Pi 2 B


texts: How can chassis ground be used for voltage measurements in a device with components of differing voltages?

texts:
The manual for my HV probe tells me to connect my ground clip to the chassis. I can see how this would be good advice for say a 12V car, because the chassis is made the ground and every component uses the same power that's hooked to ground.

However this can't be the case with say a CRT circuit. The way I see it, when I want to check voltage of a specific object (a capacitor, let's say) I need to go to the cap with both probes. I don't know if the chassis is "grounded" with a particular voltage (who cares,) but I've got a 24VDC fan motor inside this scope, and a 2,000VDC capacitor. Neither of these components can share a common ground because each is operating at a different voltage. If I wire the ground wire of a 30VDC LED and the ground wire from a 200VDC motor to a sheet of aluminum and turn it on, things are going to spark.


texts: I am using SIM808 GPS/GSM module. I came across Cold start,Warm start and Hot start in GPS Modules while developing code for a GPRS Tracker for car. I know the difference between them.My question is that if I don't use any start mode then what will be the searching procedure of gps.


texts: How do I detect open-source licence violations by companies?

texts:
Let's say I have an open source project with a license that prohibits commercial uses.  Then comes along a commercial product with striking similarities in functionality/hardware.

How would I go about inspecting the commercial product to see if they are using parts of my source code?

I realize I could do an image dump, but is that really useful, or easily obfuscated?

Are there any simple tricks I could use, such as adding strange corner case behaviors, that would allow me to easily detect if anyone has copied the source verbatim, and are not overly obvious?

Bonus legal question: can I somehow subpoena the source code, if so what do I need to have to present 'reasonable doubt'?


texts: 24 VAC source unable to drive servo motor

texts:
Here's my power supply (schematic except without the transformer since my source is already at 24 V AC and using a 100 uF electrolytic as my smoothing capacitor):

24 VAC rectifier -> 100 uF smoothing cap -> LM317 linear regulator (typical application on page 10 of LM317, running at 3.3V)

And my servo motor is an MG90S. I am feeding it 5V from a boost converter using an AAT1217.

With the servo motor disconnected, I see the servo motor source voltage at 5V and the signal line is giving the pulses required to drive the servo motor. With the servo motor connected, there is a periodic voltage drop to ~1V, causing my MCU to brownout. I hear the servo motor twitching, so it seems like the circuit is trying.

Other stuff I've tried:

Bypassing the 24 VAC and using a 3.3V DC power supply, the servo rotates fine, drawing about 200 mA from the power supply.
Using a 24 VDC source, the servo rotates fine
Using a larger smoothing capacitor (1mF) with 24 VAC, the servo still doesn't work. The voltage drop still occurs and the LM317 gets really hot.

I was thinking that the smoothing capacitance was not large enough so there wasn't enough current going into the servo but (3) disproves that. In addition, using smoothing capacitance calculations (C = (I * t) / dV), it seems like I should not need more than 100 uF. Any ideas what else could be wrong?

So, just to defend the LM317 choice a little,

The servo motor is on no more than 10s per day and not more than a few hundred ms each time.
With that, I was hoping that using a simple linear voltage regulator would be ok in terms of both cost and complexity.


texts:
I have a cheap Bluetooth/FM radio module connected to a TDA7942. Unfortunately it passes all kinds of disturbances it picks up from the power supply to its line out.

I thought to connect an audio isolator to it, but it appears that the line out is not strong enough to drive this; I lose all low frequencies through it. The DC resistance of the audio isolator is 130 Ohm.  If I connect my phone earphone output directly to the audio isolator, there is no discernable loss of quality.

Is there some kind of line driver (circuit) that I can put in-between?


texts: Precise measuring of frequency with high-speed ADC

texts:
Let's say I have precise "reference" clock and I want to measure frequency of some other "target" clock, as precisely (let's say ~12-15 digits) and as fast as possible.

In the simplest case one might just count periods, but solution will converge very slowly...

One might measure rough frequency, use PLL to generate reference clock with almost the same frequency and measure phase difference change with slow, high-resolution ADC.

But is there a way to achieve better results (faster solution convergence) by mixing reference clock and target clock somehow, and measure it with high-speed high-resolution ADC? I.e. is there an approach benefiting from high-speed high-resolution ADC?


texts: How can I get this large value of peak current in half wave rectifier?

texts:
Given values are:

C = 1.4F, V_D = 0.8V, V_P = 4.5V, and 1/T is 60Hz, 0.436ohm load.

I have to find the peak diode current.

I understand when diode is on and delta T starts, the diode current get peak value.

I get ripple voltage V_R = 0.1V and
By following equation I get i_DMAX with approximation

$$i_{DMAX} = \frac{V_p-V_d}{R} + C\cdot V_p\cdot \frac{2\pi}{T}\sqrt{\frac{2V_R}{V_p}} = 483.49A$$

How can this large value can come out from these small given values? Is this instantaneous value? I'm not sure I'm doing right.


texts: Transimpedance amplifier with current amplifier circuit.

texts:
Figure shown above is the current amplifier circuit with the output current feeding into the transimpedance amplifier (I-V amplifier). I'm using a 100mV ac signal and 120 Kohm resistor to produce a 0.833 uA. The current amplifier circuit then amplify this input current by a gain of 10 to 8.33 uA. The output current from the current amplifier circuit is then feed into the I-V amplifier circuit to measure the voltage corresponding to the current. Using the feedback resistor(R4) of 10 ohm, I expected the output voltage to be around 83 uV.
But, the current across R4 resistor is not 8.3 uA, instead it is 20mA. I'm not sure why I'm getting different current value. Also, i'm using the virtual ground IC to produce virtual ground of value 4.5 V.
Could someone help me to understand what is wrong with this circuit?


texts: I have seen that in discrete MOSFET, it is actually symmetrical, then what is the purpose of designating source and drain? if they can be interchanged. Is the designation is for just to indicate the direction of the body diode?


texts: PIC32 receives/transmits improper data on serial port

texts:
I have referred http://microchipdeveloper.com/harmony:example-usart-dynamic-wf32 to configure the UART and send/receive data between PC(Putty) and my PIC32MZ.

The demo program in the link receives the data, adds one to it and transmits it back to putty.

    case APP_STATE_RX:                          // USART receive state
    {
        // if byte received in USART instance pointed to by myUSARTHandle (USART1 in this case)
        if (!DRV_USART_ReceiverBufferIsEmpty(myUSARTHandle))
        {
           appData.rx_byte = DRV_USART_ReadByte(myUSARTHandle); // read received byte
           appData.tx_byte = appData.rx_byte + 1;  // modifying received byte confirms it was received
           appData.state = APP_STATE_TX;           // change state to TX
        }
        break;
    }

    case APP_STATE_TX:                          // USART transmit state
    {
        // make sure the transmit buffer is not full before trying to write byte
        if(!(DRV_USART_TRANSFER_STATUS_TRANSMIT_FULL & DRV_USART_TransferStatus(myUSARTHandle)) )
        {
            DRV_USART_WriteByte(myUSARTHandle, appData.tx_byte);  // send modified byte
            appData.state = APP_STATE_RX;       // change state to RX and wait for next received byte
        }
    }

However, whenever I enter (transmit) any data from Putty to PIC, the PIC reads it as "ý";0xff.

The PIC code adds 1 to 0xff and sends NULL;0x0 back.

The putty screen is always blank.

How can I transmit/receive proper data between my PIC and pc?

Thanks in advance!

Edit:- I double-checked the clock settings for the UART etc, however every-time I send something from puty (characters or numbers) all I receive in UART_Rx buffer is "ý";0xff.


texts:
I don't understand what this part is from my keyboard PCB design. Someone else worked on the design and I can't figure out what it is.Please help!

Here's another image including other parts of the design.


texts:
I have been working on a PCB layout. It's my first time working with Eagle, and my first time prototyping a board. I am using a CC2540. I understand that this uses a RHA package which has a ground pad.

I am not sure how I go about routing this in eagle. I need to connect the ground pad to a ground plane, but I am unfamiliar with how to go about doing this?

Can anyone please help me through this process or direct me to where I can get some more information?


texts: what size cable for powering an LED sculpture?

texts:
I've got four 60 amp 5 volt power supplies, and I'm sending power to a sculpture with 3000 RGB leds. So here's the total power picture we're looking at...

3000 * 5 volts * 3 leds per pixel * .02 amps = 900 watts. At 5v that's 180 amps.

My power supplies are rated for 240 amps, so I'm comfortably within my margins there. Also, my piece will only have around 50% of the lights on at any time, also the lights won't be white, so they will be using less than .02*3 leds of power...

So. What's our safety margin here... something like 500 watts seems like a good normal load, with occasional spikes higher.

(if any of this seems bogus, feel free to point that out)

My main question is this... What size cabling should I use to send power up to the art piece from the power supply box? I was looking at NEC standards and it was saying something like 4 gauge... but it was only asking me about amps used... And I think that's for 120 volts. Does it matter that I'm only sending power at 5 volts?

The cables from the power supply box to the sculpture will be around 20 feet long.

(Oh - and if you want to check out the art piece in progress, I'm posting a lot of it here... https://www.facebook.com/skylightpdx/ )


texts: Interference beetween ADC samples with XBee and photoresistor

texts:
I'm using an XBee serie 2 module for sampling the values of three sensors, a photoresistor (LDR) a moisture sensor and a temperature sensor (LM35). When there is no brightness the photoresistor has the maximum value (1023), but if the environment is very very dark the value is the same 1023, but the other sensors begin to be instable giving values greater than normal. Maybe an XBee ADC sampling problem? or could be a circuit problem?

The XBee module I'm using for sampling, use a cyclic sleep mode: it wakes for 100ms and stay sleep for 3 minutes.. I tried to use a greater wake time like 1s but the problem is always there.

This is the scheme:

simulate this circuit – Schematic created using CircuitLab

This is a picture:
https://dl.dropboxusercontent.com/u/9029111/IMG_4712.JPG

I think it's a power problem, because if I put a 1Kohm resistence near R2 the moisture sensor is ok, and the temperature varies very little to vary the brightness


texts: Half-bridge circuit not working, high side running hot

texts:
As I'm a noob in this field I’m experimenting with a half bridge circuit to run a buck converter to learn about it. First I tested my circuit by putting everything together on a breadboard and it worked great. After soldering it together on a piece of perfboard I ran into a problem. When I apply a voltage to the circuit, the high side MOSFET runs very hot within seconds. I found that the high output of the gate driver doesn´t provide enough voltage to the gate, it outputs around 17V instead of 25V as it does on the breadboard (VCC is 15V). So I think something is wrong with my bootstrap circuit.
PWM is created by an ESP32 and SD is pulled to 5V.

Things I tried so far:

Doubled the bootstrap cap (ceramic) to 200 nF.
Increased C4 from 100 nF to 10 uF (thought 100 nF might not be enough to charge the bootstrap cap).
Tried several PWM frequencies from 20 to 75 kHz and duty cycles from 20 to 80%.
Replaced the gate driver IC and MOSFETs.

Still the high side MOSFET is running hot.
Again, this design runs perfectly fine on the breadboard. I checked the connections on the perfboard more than once and it´s soldered together like in the schematic. I´m happy about any help!
Update: Here the VS and VB pins as requested in the comments, unfortunately I only have a potato China oscilloscope available. But I think what can be observed is that the V_min on the VB pin on the perfboard is way higher than on the breadboard. Can anyone observe what could be wrong with the circuit? Also note that the perfboard has a 1N5817W Schottky diode installed instead of the 1N4007 now.


texts: Transformer secondary winding resistance

texts:
I am struggling to understand how to model a resistance loss of a transformer secondary winding. In a typical flyback converter, if the primary and secondary transformer have a resistance loss, how do we model the the secondary transformer resistor during the second interval (when the mosfet is off and diode conducts). If the turns ratio is 1:n, the current during the second interval would be i/n. So the voltage drop across the secondary winding resistor would be i/n*Rsecondary. As per my understanding, the voltage reflected on the primary winding during the second interval should be -Vload/n - i/n * Rsecondary/n. But this does not seem to be correct. The schematic of a flyback converter is:

Any help/pointer will be appreciated. Thanks


texts: Can I exchange data from a smartphone and in parallel quick charge it with an ic?

texts:
I am trying to exchange data between a smartphone and an microcontroller, also in parallel i would like to quick charge the smartphone with a commercial ic. The usb protocol is 2.0. Can i exchange data simultaneously with the quick charge protocol?
This will be really helpful. Thank you.


texts: Can I use Opto Isolator or Opto Coupler instead of Relay to operate AC Source?

texts: I am designing light control board using micro controller.As I want to make my circuit board smaller, So I am thinking to use Optoisolator or Optocoupler instead of using Relays. So please let me know, is it fair to replace "Relay" with "Optoisolator" or "Optocoupler"? Can Optoisolator work on more Amps?


texts: Burned ST LINK by connecting it to the board

texts:
I have a PCB that is getting powered from mains and is connected to a Hi Link component (HLK-5M05 with 5V output). At the moment it is connected to an extensions with a button, a little bit like this one. When I power it on and start measuring I get the 5V output, 3v3 output, I can see that some components are working accordingly (voltage monitor) and then I went to load my firmware into the st microcontroller.

I disconnected eveything since I don't want to accidentally get shocked, I connect all the pins (gnd to gnd, 3v3 to Vapp, TMS -> TMS, etc). After I connected this I connected the board to the extension and turned on the button. Immediately I heard a loud noise and I noticed the st link wasn't ON anymore (a capacitor exploded) and the circuit breaker activated. Then I went to measure the board and I notice that there is a3v3 short to ground.

I have revised my entire layout and there is no connection between mains and GND in my circuit. The closest to it is the analog circuitry for measuring the voltage, but still, they are not connected. From what I can see everything is connected as it should be according to datasheets, but it still didn't work.

After that I tried connecting and programming my board via the bootloader. I did the required connections and tested my board and everything was working properly. Again I disconnected everything and connected the USB-serial board to my board (GND, TX and RX ... very simple and straight forward). When I connected everything the circuit breaker still activated but fortunately this time it didn't destroy my PCB.

Very distraught I turned off the button and went to disconnect the USB-serial board and got shocked. After that I measured the voltage between the USB connector and my PCB ground and there was 220Vac ... when the extension was turned off and the extension is not grounded (not USA .. incompatibility between different types of plugs ... old everything), but there is 0V when I measure the voltage between them when the extension is powered on.

What could I be doing wrong? I measured other devices (USB chargers and similar) and they all had the same behaviour ... 0V when ON and 220V when OFF. I have compared my schematic to others, such as open energy monitor and many other projects you can find online and I'm not doing anything crazy here (in terms of schematics and connections). Could there be something wrong with my installation? Or is it a PEBKAC (more like between PCB and chair [PEBPAC])?

EDIT:
Adding schematics, just the important part, the rest is all decoupling capacitors, oscillators, etc.


texts: I am not electrically savvy person but I have general idea of what some things are and what they do. I have this nice computer video card that has a broken transistor on the back side and is not working. The reading on it is K1P Z4. I did some googling and some online catalogue searches but that didn't turn anything. There are 2 transistors next to each other and one is broken in half (appears someone has dropped something on top of it) and they are the same size. The broken one is unreadable in the middle but beginning and the Z4 end is same as the other transistor so I assume they are the same. I am hoping any of you can help me identifying it and get a replacement.picture taken with a magnifying glass


texts: Voltage of reverse-biased series diodes?

texts:
Consider the following simple circuit:

In the above circuit, D1 and D2 are not identical. The reverse leakage I of D1 is 0.1 pA and the reverse leakage I of D2 is 5 pA. The voltage V is 3 volts.

It is required to calculate I and V of both diodes.

As the diodes are series, so the current is equal for both of them. And if we assume that 3v is lower than the break-down voltages of the diodes, then we can conclude that I is - 0.1 pA (lowest reverse leakage).

But I have problem with the voltages. How can I calculate voltages of diodes in this circuit? If the diodes were completely identical, then the voltage of each diode was 3/2. But in this case they are different.


texts: I have this circuit for which I have to find the truth table for all imputs whether they are logic 1 (VDD), logic 0 (GROUND) or X unknown. But I am having trouble understanding what I am supposed to do to find the OUTPUT when the imput is unknown..


texts: small signal equivalent circuit with BJT and MOSFET problem

texts:
Here's my problem.

i've been trying to draw the small signal equivalent circuit. And this is what i have

but i feel something's wrong because when i calculate voltage gain i dont have to use gm of the BJT. can you guys show me where did i do wrong?


texts:
I want to implement this truth table (in Figure 1.1) into a circuit using an 8-1 multiplexer. I did the circuit schematic (in Figure 1.2) in Xilinx ISE Design Suite and it does work, but when I try to make the wiring diagram (in Figure 1.3) with a program the circuit does not work. Can you help me identify the error?
Thanks.

                                                      Truth Table (Figure 1.1)

                                                      Circuit Schematic (Figure 1.2)

Wiring Diagram (Figure 1.3)


texts: Is there anything wrong with this simple circuit ? Transistor + LED

texts:
This is my first time posting a question.
So this is a simple circuit that I have on a PCB. A 2 in 1 LEDs with a common anode. As soon as I power my PCB both LEDs turn on even if the base isn't pulled up and even when manually pulled down nothing happen. Do you guys have any suggestion for tests to conduct to understand what's wrong ?
LEDs :SM1204BC-R_G
Transistor : NPN Bipolar Transistor 863-MMBT3416LT3G
Thanks,


texts: Why does this N-channel MOSFET not turn off?

texts:
I was playing around on CircuitLab to see if I can add an overvoltage cutoff to the reverse voltage protection circuit in TIs slva139. Using a zener, I expect OVS to start rising beyond the zener voltage and turn on Q1, and pull PGD to ground. This happens fine. However, M1 does not seem to be turning off, even with PGD < Vn.

simulate this circuit – Schematic created using CircuitLab

Circuitlab Simulation results for DC sweep (-15-+15):

I suspect I'm missing something incredibly stupid, but I can't figure out what. Help would be appreciated, as well on comments about why this is a stupid protection circuit (which I suspect it is, because it seems trivial and yet never used).

For context, I'm only attempting to protect against, say, insertion of 12V in a 5V input, which might fry 5V components connected to the rail.


texts:
I have this stepper motor with unknown back EMF / RPM.  There are 200 steps/rev (i.e. 1.8deg step angle), and 8mH "phase inductance", but I'm not sure if that's enough to calculate back EMF.

I hooked up one of the parallel windings from each phase to an oscilloscope.  (Specifically, red/yellow on one probe, white/orange on the other probe.)

I then manually rotated the shaft and captured the following measurement.  You can see that the time between two signal peaks is ~770Hz and the voltage magnitude is ~33V.

Do those two 90deg-phased peaks correspond to one step each, therefore implying that the RPM at that time was 770(step/sec) / 200(step/rev) * 60(sec/min) = 231RPM?
Does that imply that the back EMF is 33V/231RPM = 143mV/RPM?
If so, how is that reconciled with the specs saying 30VDC is sufficient to drive the stepper at 1500RPM, which would then correspond to ~214V in back EMF?

I'm a bit confused.  If the motor was hooked up in "serial" mode instead, that would result in an even "worse" (double) back EMF/RPM.

Edit: FYI, in case anyone thinks this is because there is no load attached, I applied a 22 Ohm resistor to one of the parallel winding terminals, performed a similar measurement and calculated a similar back EMF constant of 134mV/RPM (compared to 143mV/RPM earlier).  So I don't think it has to do with the terminals being "open circuit" (which they technically wouldn't be anyway, since the scope probe or air has a very large but still not infinite resistance).

Edit 2: This question is similar and seems to support my back emf constant measurement method.  However, that person was also encountering an unexpected value, and no satisfying answer was given.

Edit 3:  I should add, my calculated back EMF / RPM was based on the sinusoidal peak vs the average (which it should be according to this answer).  Therefore, to make my calculated back EMF constant above consistent with the usual definition, it should be multiplied by 2/pi ~= .637.  However, even 64% of the calculated voltage at 1500 RPM is still way above the 30V I was expecting to be able to use.


texts: Need help with LM317 (500 mA) out of 3 volts supply Calculations

texts: Does LM317 regulate a constant current of 500 mA out of 3 volts supply (Vin) ? Need help with its associated calculations please. !


texts: NeoPixel led WS2812B shines the right color only every 2nd time

texts:
I'm trying to create project where I can light up WS2812B whatever color I want and specific RGB color code is delivered through UART. So when I receive the code I'm trying to send data to WS2812B but it seems to be working only every 2nd time when it actually shouldn't and it doesn't work at all when it should.

I'm using Atmel's Atmega328P-PU and its CPU speed is set to 8MHz. This code actually worked fine when I 1st wrote it but I had to change some stuff in UART section so had to compile and flush it again but this time it was done from Linux using avrdude command line tools instead of Windows 7(which was on my friends PC and got deleted).

This is data timing diagram for WS2812B

Everything in code works fine except for sending '1' and '0' to LED and it happens in function set_leds_color. Weird thing is that if I leave the __builtin_avr_delay_cycles(); values as they were before my UART code updates (and as are shown in code) it always sets LED's color to white kind of like it would always send only '1' to led (255,255,255). Even if I set delay for '0' to __builtin_avr_delay_cycles(1) nothing changes - any color is displayed as white. Now the interesting part is that if I remove this delay for '0' so code become like this

//send 0
else{
   DATA_PORT = high_data;
    DATA_PORT = low_data;
}

when I set the same color multiple times in a row - LED actually sets my desired color 1 time but 2nd time sets white again. This goes on. I have no idea what the problem is. I tested that __builtin_avr_delay_cycles() works as expected and my CPU frequency is indeed 8Mhz. I also sent rgb_array[] values from mcu to my PC thought UART and they are fine as well. Can anybody give me some suggestions what might be wrong? Thanks.

Here is my final code

#include <avr/io.h>
#include <util/delay.h>

#define DATA_PORT PORTD
#define DATA_PIN PD2
#define DATA_DDR DDRD

/*
UART stuff
*/

void fill_array(unsigned int* arr, unsigned int color)
{
    for(int i = 0; i < 8; ++i)
    arr[i] = color & (1 << (7 - i));
}

void set_color(unsigned int* arr, unsigned int red, unsigned int green, unsigned int blue)
{
    fill_array(arr, green);
    fill_array(&arr[8], red);
    fill_array(&arr[16], blue);
}

void set_leds_color(unsigned int red, unsigned int green, unsigned int blue)
{
    //prepare 24 color bits to send to LED
    unsigned int rgb_array[24];
    set_color(rgb_array, red, green, blue);

    int high_data = DATA_PORT | (1 << DATA_PIN);
    int low_data = DATA_PORT & (~(1 << DATA_PIN));

    for(int i = 0; i < 24; ++i){
        //send 1
        if(rgb_array[i]){
            DATA_PORT = high_data;
            __builtin_avr_delay_cycles(6);    //1 clock cycle is 0.125us
            DATA_PORT = low_data;
        }
        //send 0
        else{
            DATA_PORT = high_data;
            __builtin_avr_delay_cycles(3);  //1 clock cycle is 0.125us
            DATA_PORT = low_data;
        }
    }
}

int main(void)
{
    DATA_DDR = (1 << DATA_PIN);
    DATA_PORT &= ~(1 << DATA_PIN);

    initialize_UART();

    while(1)
    {
        int color_code[3];
        if(receive_color_from_uart(color_code))
        {
            set_leds_color(color_code[0], color_code[1], color_code[2]);
        }
    }

}


texts: 3 Phase 3 wire delta, current transformers and lots of questions

texts:
I Need to design and make a CT (current transformer) to energize a 3ph relay with sufficient voltage and current from low load to full load. I'm thinking of a toroidal transformer with very few windings of 10 or less since I'm not running anything except a relay

A CT is preferred as it allows (I hope) me to monitor all 3 phases at once and output to a 3 phase relay connected to a shown 3ph MIG wire feeder.

So what I hope will happen is when power is ON but the stick welder is not energized the wire feeder is NOT ON either. When the machine is on and power is going in to the machine the CT energizes the 3ph relay powering on the wire feed unit in a pass through type configuration.

I guess my main questions are if a CT divides amperage, is voltage multiplied by the same factor?

A CT with that is "measuring" no load outputs no current either? so not energized i.e. 3 phase delta, 3 live wire going somewhere but the load is yet to be turned on...

From what little that I know/understand Its like voltage transformer in reverse (voltage increases at the expense of reduced amperage). the opposite could be said about a CT from what I little know/understand, amperage is reduced while voltage if left open circuited can quite quickly rise to unsafe levels.

Will 3 wire Delta pass through a single CT and function as normal, reduced or just not possible at all. Will I need to have 3 CTs wired in series with a relay as load w/ or w/o a resistor?

One last Question googled and what not still couldn't find a definitive answer with a formula and example of how to find the output voltage of a CT, I'm still not sure, answers were all to do with current/amps etc...

simulate this circuit – Schematic created using CircuitLab


texts:
I need to implement the ADC chip MCP3004 in a circuit. The Vref and Vdd are tied to 3V3 rail. According to datasheet of this ic the maximum voltage that an ADC input pin can handle is Vref, so in this case is 3V3.

Because of some things, voltage on any ADC input pin can go as high as 3.5V.
Now, according to datasheet of the device on the "Absolute Maximum Ratings" it is stated that:

All Inputs and Outputs w.r.t. VSS ............– 0.6V to VDD + 0.6V

I understand that the variation of  +-0.6V on input is related to protection series diodes that are tied to the input pin. So in this case the maximum positive voltage on input will be 3.9V and minimum will be -0.6V which it is on my specs.

My questions are:

Will it be safe to apply 3.5V, for a small amount of time?
What will be ADC output?

Thank you in advance for your answer.


texts: What type of energy consumption is indicated with the power rating of a device

texts:
For example, I have a 36W LED unit.

If I needed to measure with a electricity meter, would 36W be active, reactive, or  apparent power consumption?

I would appreciate if you could tell me (if there is any) what International Standard is followed to print out the values and all necessary indications (active, reactive, etc.)


texts:
on my bedroom I want to put two 220V lights on the side of my bed, and I want to control them with 3 switches:

the main switch is beside the door, and will commute both lights on and off.
two secondary switches, one under each light beside the bed, that will control only the light over it.

so, the main switch will turn on/off both lights.
the switch on the right side will control the right light.
the switch on the left side will control the left light.

There is a way to implement this configuration?


texts: Noise from stun-gun based butane torch ignition spark is locking up ATmega328 microcontroller

texts:
I have a stun gun (http://www.amazon.com/VIPERTEK-VTS-989-Heavy-Rechargeable-Flashlight/dp/B00FPE6UN2) which I am using to create a large 1/2" electrical arc through the air to remotely ignite a butane-based torch with a 4ft flame.

The stun gun runs on its own isolated battery, and is optocoupled to an Arduino Pro Mini (with Atmel Atmega328 microcontroller) in order to trigger the stun gun ignitor, as well as open the solenoid flow valve.

My 5V power to the Arduino comes from two switching power supplies diode ORed together through some Schottkys. I have a 2200uF cap I added to the power supply output after the "OR" diodes. There is a dedicated battery for the switching power supplies to the Arduino, separate and not connected in any way to the stun gun's battery.

I have added a 1W 5.1V Zener diode reverse-biased from Arduino Vcc to GND to attempt to clip off unwanted positive and negative voltage spikes that come from the stun gun arc.

However, the power supply is very clean until I fire the stun gun to light the torch. During this period, my O-scope shows transients up to 10+ V and down to -5 or less V, even with the Zener diode in place.

Note that the sparks are occurring at a rate of ~30 sparks/sec, and I'd guess (I'd need to verify via more background research to be more sure) that the voltage at the arc electrodes is 40kV~80kV.

Sometimes my microcontroller completely glitches in very unexpected ways. Ex: stun gun ignitor locks "ON" even when my code has no place where it remains on, LED heartbeat stays "ON" even though I have no place where I command the LED to stay solid and not blink, LED hearbeat keeps blinking indicating it is receiving commands properly but solenoid valve will no longer respond, etc etc. Reset fixes these problems. I think they are EMP-pulse related, or something happening inside the chip with bitflips or something, not code related. I am an experienced coder on these chips, but I am not experienced dealing with large electrical arcs and stun guns, and mitigating EMF and EMP noise.

2 questions:

1) How can I remove/reduce unwanted EMF/EMP noise from this large spark gap/stun gun ignitor? +10 to -5V sounds REALLY bad for the microcontroller, to me, unless it's an artifact of measuring with my oscillocope and is not really present like that on the chip, with the Zener in place.

2) will configuring the Watchdog timer fix my problem and consistently force auto reset during lockups, or is it possible for the watchdog to lock up too? I'll try it regardless, but additional info beyond my knowledge bank is helpful.


texts: Connecting arduino to power another device

texts:
I have an arduino board which I want to use to give power to a device which uses two 1.5V batteries. I think I have to remove the batteries from the device and control the power supply via arduino, but since I have never did this, I'm asking which is the best way to do this.

How would you use arduino to give power to an external, battery powered device?

* Adding details *

I want to power an electro thermoregulator of my house. I have the arduino controlled with a GPRS module, and everything is working fine. The only point left is how to use the arduino to give power to that device.


texts:
If I want to read a (bunch of) 74HC165 chip(s) over an SPI port on a microcontroller, this is simple enough. Connect them through Q7 to DS on each, apply the final Q7 to MISO, notCE to SS and CP to SCK. This works fine.

But now how do I share the SPI bus with other devices that I want to read? The 165's Q7 output is never hi-Z, so I can't share the MISO pin with other devices. I'd need some way to "detach" it - a buffer of some kind.

I know there are 74-series chips that have various buffers that can be made hi-Z (such as a 74HS240) but that's a whole additional chip just to be able to share the shift register. Perhaps some cunning way to put a transistor between the final Q7 and the microcontroller's MISO, controlled by the SS line?

Edit: Alternatively, can someone suggest some other parallel-in serial-out shift register that does have a tristate serial output line, and therefore suitable to use on an SPI bus?


texts: Why does this resistor avoid this oscillation?

texts:
I am learning the effects of diodes going trough ON to OFF (so that I can see the consumption of these kind of power supplies) and, when it comes to simulate the circuit, I dont understand why if I remove the resistor shown at the image, all the circuit gets unstable.

Here is the image of both simulations:

The first one, without resistor. The Voltage and Intensisty oscillates.

At the second one, after adding that resistor, the oscillation disappears

Thanks for helping :) . I still dont know how can I analyse the effect of that resistor (Logic, basis of circuit, Laplace... ) as I am not used to work with coils.


texts: If I used the primary coil as an inductor, does the secondary coil affect it?

texts:
I've read this question. It's about how to obtain the maximum inductance from a transformer:
How do I use a transformer as an inductor?

Now, I would like to use the primary coil only as an inductor to study some basics about inductors. I'm going to build simple LR, RLC filters and other circuits.

If I changed the frequency or the components of the circuit that contains the primary coil, will the secondary coil change the inductance of the primary coil?

I need the primary coil to have a fixed inductance and behave like a normal coil.

The secondary coil is open circuit and not loaded.

I imagine that I can remove the secondary coil out of the core. Will the inductance of the primary coil change? This question will help me understand mutual inductance better.


texts: TX Polling Not Working when setting RX interrupt stm32f103rc

texts:
I was trying USART on STM32F103RC,baud 115200, sysclk 72MHz, 1 stop bit, no parity and i connected my stm with usb to serial to look my output on terminal. At first i did polling of RX and TX and send command from terminal to stm like "led on" to turn on led and "led off" to turn off led and it worked perfectly with the response i have send from stm. rx and tx worked fine

Next what i did was i configured rx as interrupt and tx as polling.when i did that my rx is working fine but my Tx stopped working.

My code looks like this

USART1 IRQ

 /** @breif: USART1 IRQ
     * @param: None
     * @retVal: None
   */
 void USART1_IRQHandler(void)
 {
     if(USART1->SR & USART_SR_RXNE)
     {
            rx_data[datapos] = USART1->DR;
            datapos++;
            if (datapos > 255 )
            {
                datapos = 0;
                Clear_Buffer(rx_data);
            }
   }
 }

USART INITIALIZATION

 void USART_Init()
 {
     /*Enable Clock for USART port and USART1 */
     RCC->APB2ENR |=  RCC_APB2ENR_IOPAEN | RCC_APB2ENR_USART1EN;
     /*Rx,Tx setup GPIOA->CRH = 0x000004B0*/
     GPIOA->CRH |= GPIO_CRH_MODE9;          // Tx Mode- 11: Output mode, max speed 50 MHz.
     GPIOA->CRH |= GPIO_CRH_CNF9_1;         // Tx CNF - 10: Alternate function output Push-pull
     GPIOA->CRH &= ~(GPIO_CRH_MODE10);  // Rx Mode- 00: Input mode (reset state)
     GPIOA->CRH |= GPIO_CRH_CNF10_0;    // Rx CNF - 01: Floating input (reset state)
     /* Baud rate set 72MHz/115200 */
     USART1->BRR = SYSCLK/BAUD;
     /*Enable Rx, Enable Tx, Enable USART*/
     USART1->CR1 = USART_CR1_RE | USART_CR1_TE | USART_CR1_UE;
     USART1->CR1 |= USART_CR1_RXNEIE;  //enable rx interrupt
 }

USART TRANSMIT

 /** @breif: Transmit a String
     * @param: the string to be transmitted
     * @retVal: None
   */
 void Transmit_String(char *str)
 {
     while(*str != '\0')
     {
         Transmit_Char(*str);
         str++;
     }
 }

 /** @breif: Transmit a character
     * @param: the character to be transmitted
     * @retVal: None
   */

void Transmit_Char(char data)
{
    while (!(USART1->SR & USART_SR_TXE));
    USART1->DR = data;
}

MAIN

 int main(void)
 {
     Led_Init();
     USART_Init();
     NVIC_Init();
     datapos = 0;
     while(1)
     {
         if(strstr(rx_data,"led on\r"))
         {
                RESET_GPIO_BIT_PORTD(2);                        //Make Led High
                Transmit_String("\nLED is ON\r\n");
              datapos = 0;
              Clear_Buffer(rx_data);
         }
         else if(strstr(rx_data,"led off\r"))
         {
                SET_GPIO_BIT_PORTD(2);                      //Make Led Low
                Transmit_String("\nLED is OFF\r\n");
              datapos = 0;
              Clear_Buffer(rx_data);
         }
         Delay(1000);
     }
 }

With this code led is turned on and off perfectly but Nothing is transmitted on terminal. I guess it's something with IRQ as IRQ is for USART1 and not mentioned anything about either it's for RX or TX.

But i want to poll for Tx and Take interrupt for Rx and just not getting the correct procedure to do that. Any suggestion would be helpful.

Thanks in advance.

P.S I can provide full source code if required.


texts: NOT another Arduino vs. Raspberry Pi question

texts:
I've developed an interest in electronics, more specifically getting to the very root of how my operating system functions.  My goal over the last few years has been to learn as much as I can about how the OS works so that I might one day contribute to an open-source project, or perhaps begin a project of my own.  However, over the last few months, I've taken an interest in a more bottom-up approach, and I really want to start getting into the hardware side of things.  The problem is that I lack any vocabulary to describe what it is that I'm interested in learning about.

I have quite a bit of experience dealing with microcontrollers from my High School robotics days, but the particular model we used left much to the imagination in regards to more fundamental processes (assembly, dealing with CPU's, etc.)  I learned nothing about capacitors, transistors, resistors, etc.  My aim is to remedy this.

From my understanding, Arduino would be a good starting point, but based on what I've heard, their philosophy is to obscure the more technical details with the intention of streamlining the developing process.  This is of no interest to me.  I've also heard of Rasberry Pi, but the OS layer seems like more of an additional obstacle for what I have in mind.  Is there some sort of all-in-one solution that will expose me to all the most important concepts, but at the same time allow me to make practical use of my projects?

What is a good starting point for someone in my situation?  Is the microcontroller world tangential to my overall goals?  If Arduino and Rasberry Pi aren't my best options, are there any no-bullshit alternatives?  What about virtual alternatives? General tips are welcome!


texts: Charging starter and domestic battery with solar panel

texts:
I have two 12v domestic batteries connected in parallel and one 12v starter battery. Starter and domestic batteries are connected via negative pin to main switch which then connects to engine and appliances. The alternator is connected to LUCAS 33RA SRB600 relay and charges both starter and domestic batteries. There is also solar panel which is connected into regulator with two outputs, each connects to one domestic battery.

Now my question is if there's any point having the regulator connected to each battery? shouldn't be enough to connect it to one and second would be charged because of the parallel connection? If so, I would save one output on the regulator which I'd like to use to charge starting battery. In that case would I need some over-voltage protection to save regulator from high currents on engine startup?


texts:
I have made a bench power supply from an old PSU and added a USB port connected directly to the 5V rail (leaving the data pins disconnected).

When I connected a TP4056 charging board (like this), the TP4056 smoked and blew up.

I am trying to understand if the board was defective (or I messed up with the wiring) or if the USB must not provide more than 1A (the 5V rail of the PSU provides something like 25A).

As far as I know it does not matter how many amps the USB can provide since the connected device always draws what it needs, but I like a confirmation from someone more expert than me :)

Cheers


texts: Is this 400V capacitor rating for DC or AC?

texts:
I am fixing my mom's flat hair iron, I already figured out that problem is in one capacitor which should be 470nF, but currently has only 200nF capacity. It is rated for 400V, but I do not know whether it is DC or AC.

I reverse engineered schematic. That capacitor is marked as C1.
I understand how this circuit works, and why it doesn't work with lower capacity.

Photo of capacitor:

I am confused. I googled that sort of capacitor and somewhere it is described as DC capacitor. But it is used as AC in this case, right?

So, is this capacitor DC or AC? Or what type of capacitor it is? I have to find proper replacement.

ANSWER:
According to comments and answers, this capacitor is polyester (or polypropylene), with rating 400V DC.


texts: Techniques to make art with PCB Silkscreen in Altium

texts:
I am finishing a PCB and I wanted to add some kind of artwork in my PCB, but not just import an image, I was thinking about placing some lines in the silkscreen, but I didnt wanted it to cover the other things in the silkscreen plane. I wanted it to behave like the Polyogn Pour, or even better, like the inverted, were the lines (or a fill) were on top of some text, the text wil invert the colors. Is this even possible? Tips about cool artwork things to do in Altium are welcomed as well.

EDIT:

Example of what I am aiming for, the white stripe is a random image and as it touches the components names, they will still be readable, since their color will automatically change, i.e. the software will remove the silkscreen overlay from the intercepting parts (or maybe make a full rectangle around the names to protect them, which I didnt present in this example but I think its easy to imagine).


texts: check it out guys  ]3]3  the circuits above are both for an electronic dice that is supposed to count from 1 to 6 but none of the LEDS are turning on for the one that is far below, can anyone tell me what I did wrong and the top most one LEDS D9 and D10 aren't coming on as well. Can anyone tell me why and please bear with the quality of the picture and the quality of my english.


texts:
TLDR: The question is about retrofitting a balancer to the Ni-MH battery of an existing appliance (that doesn't trickle charge the battery), preferably in the way that will not require frequent access to the battery. Changing the charge/discharge logic of the appliance doesn't look feasible - this way it would be really better to rework the circuit for Li battery.

While there's a lot of Lithium balancers for every common Li chemistry, Nickel (Ni-MH or Ni-Cd) balancers seems to be nearly non-existent.

I know it's told that Nickel cells would balance if charged with a standard C/10 charge for 16 hours. And in pre-Li era, enthusiasts would make the same C/10 "forming charge" of the pack after assembly, then use it as is, without caring too much about disbalance.

But recently I've run into a situation where it's desirable to have a Ni-MH balancer.

The device (robotic vacuum cleaner) charges 12S Ni-MH 2200mAH battery with ~C/2 current, with dV/dt and dT/dt end-of-charge controls seemingly in place. (And discharges them at ~C/2 when running.)

After few hundred cycles (a year or so of nearly everyday use) the usable capacity of the battery significantly drops.

Cell-by-cell test clearly shows some cells where chronically undercharged, that resulted in polarity inversion during discharge and rapid deterioration of affected cells.

I think that proper balancing could significantly (2 times or so) prolong overall usable battery life (as the healthy cells in the battery still have 80%+ of their initial capacity).

Searching the net resulted in few proposals for Nickel balancer:

1) Very practical and simple voltage limiter: https://www.electroschematics.com/balancing-ni-mh-battery-packs/

A pair of rectifier diodes per cell that will partially shunt the cell once it's nearly full, thus limiting it's charge, and giving runners-up a chance to catch up.

Requires all diodes to be on a common heatsink for temperature equalization, will drain batteries fast if not disconnected, will limit usable capacity of the battery.

While cruder, it looks to be OK for occasional balancing, but it's impossible to integrate such a "balancer" into the battery.

2) Microcontroller-based inductive balancer: http://cache.freescale.com/files/32bit/doc/app_note/AN4428.pdf

Good all-around solution, but it looks like an overkill for the case. The feasibility criteria is the cost of the balancer that should not significantly exceed the cost of cells for a new battery.

3) Simple charge shuttle balancer: https://easyeda.com/Popov_Alex_r/Battery_Balancer_Ni_Cd_Active1-840522a2a4e44fe89bf70d560e4607f9

Looks great for integration with standby current of 80uA (that's 60mAh/month, comparable with self-discharge of 2200mAh Ni-MH cells), but charge shuttles are not particularly effective, and I'm in doubt if it would be able to reach balanced state on a used battery with maximum balancing current of just 10mA.

Looks like none of purpose-built balancing ICs are able to work with Nickel cell voltages, and most are kind of specialized on Li cells with undervoltage protection on ~2.75V.

Any other ideas on Nickel battery balancer that could be integrated into the battery of an existing appliance?


texts: What should be the coil ratio to wirelessely transmit 12V/8A?

texts: I am doing a project on wireless charging of a 40AH battery, for that I used step down transformer of 12V/8A that works fine, But now my concern is to replace transformer with coils which can give me same ratings as 12V/8A.


texts:
In structural VHDL, is it acceptable to use signals declared with the same name in different components?
For example:
Component_1 uses a signal declared Temp_1
Component_2 also uses a signal declared Temp_1
These two components are both instantiated in the same higher top level source code?


texts: How to measure input/output impedance of amplifiers in a simulation?

texts:
What is the most effective way of measuring the input/output impedance of an amplifier in a simulation?

When I know the impedance I want to measure is purely resistive, I usually set up an input signal Vin and a test resistor as a resistive divider with the desired impedance. Then I compare the voltage values of the input/output and work my math to get a number for the impedance.
Is there a better way?

I am using Orcad Capture with PSpice.


texts:
I have a chip that uses SPI for communication and would like to connect it directly to the USB port on my computer. Does anyone have experience with using a USB to SPI converter? How would I design a circuit to convert USB to SPI?
http://www.robotshop.com/devantec-usb-i2c-spi-serial-interface.html

http://www.sparkfun.com/products/9235


texts: I am working on a voltmeter and the tolerance for it is 0.25% ∀ 1 digit. I am not sure what exactly what this means. I am guessing if my value was 19.95 'for all' could mean I have a range of 19.94 and 19.96?


texts: How can I make a USB cable as narrow as possible?

texts:
Background
I'm installing an air quality monitor outside my apartment. I have no power outlet outside, so I have to plug in the power supply inside and run the wire through my wall. The collected data will be shared via wifi. The wall is concrete, and the power supply is pictured below.

Problem
I'll need to drill to route the cable, and I'd like to drill as small a hole as possible. This presents a couple of challenges. In order to fit the head of the USB cable through the hole it'll need to be around 11 or 12 mm, and even larger to fit the ferrite bead. I would like to avoid drilling such a large hole.
Question
In the interest of drilling as small a hole as possible, can I cut the USB cable and solder it back together once it's been threaded through the hole? This would mean that the hole would only need to be a few millimeters wide. Assuming I go this route, must I reconnect all interior parts of the USB cable (the bare copper wire, the foil shield, the red 5V cable, the black ground, and the other two data cables)? Or can I get away with just reconnecting the 5V and ground cables?
Obviously this would mean I would have to cut the cable again if/when I decided to move it. Is there any way to avoid this? Are there other connecters I could use for this sort of purpose? Is there something else I haven't thought of?


texts:
I want to solder a USB A connector to my Trinket m0 instead of using an adaptor cable to plug into my PC.

Can I access Trinket m0 USB through GPIO pins?

I have looked at the description of the pinouts, but I cannot work out if it is a yes or no.

Any ideas?


texts: Phase modulation in the polar transmitter

texts:
In the polar transmitter, after the I and Q signals are converted to amplitude and phase, where the phase is in the range of -pi to pi, the phase is further differenciated to obtain the change in frequency and then fed to an ADPLL.

If the original samples contain a phase change from -pi+0.01 to pi-0.01, then there would be a change in frequency proportional to 2pi-0.02. Is there some way to limit the magnitude of this change? As the two samples are actually relatively close on the IQ-plane.

Another question is, if I wish to upsample the phase signal, the extended version of the type of phase change mentioned above creates an originally non-existent trajectory (as the interpolator does not know modular arithmatic). How should I solve this?

Thank you.


texts: Battery voltage drops when connected to PCB

texts: I have a circuit containing an atmega328p microcontroller with hc-05 bluetooth module. microcontroller is powered via 7805 regulator. When 7805 is supplied the source voltage by a 9V battery, the circuit works fine on a breadboard, but the same circuit fails on a PCB. I have tried two different PCB designs, but they have the same problem. The battery input voltage falls from 9V to less than 1V. I have verified multiple times that the PCB design is the same as the breadboard design. Is that a fundamental rule to PCB designing that i am missing?


texts: transistor toggles an LED, but not a solenoid valve

texts:
I'm working on a hobby project where I'm trying to drive a solenoid valve with an arduino (for some automated plant watering).

The solenoid valve takes 12v, so I've rigged up some smaller batteries in series to supply that 12v. That works - when I plug the solenoid valve directly into the battery, it opens. According to its spec sheet, the valve can draw 500mA. (Although that's a lot, I only need to do it for a few seconds maybe every few hours).
YOu can see the solenoid's specs here: http://www.ebay.com/itm/1-2-Gravity-Feed-Electric-Solenoid-Valve-DDT-CD-12VDC-/290763981675

Next, I made a little circuit that toggles an LED with a transistor - a digital pin from the arduino (5v) is the base input, and the LED is fed by the battery (so battery positive->led->collector->emitter->battery negative). That works too, the light blinks on and off (driven by code). This works whether the power source is the battery or the arduino (although I found I had to give the two circuits a common ground for that to work).

However, when I hook up everything together (all powered by batteries), the LED still toggles, but the solenoid doesn't. Is this a problem with high-side vs. low-side transistor wiring? (I'm kind of hazy on the distinction, but if it works for the LED, then that part of the circuit is correct, right?).

The NPN transistor is an MPS 2222. I think from its fact sheet, it ought to be able to handle this load, right? Am I reading it wrong, and do I need to upgrade to one with a higher current capacity, or better voltage limits: http://www.farnell.com/datasheets/115091.pdf

Also, is it enough to use an LED to protect the circuit from back-emf when the solenoid is turned off?

Thanks! In the photos below, the black cable coming in from the bottom left is the digital signal from the arduino. The yellow wire (and the stuff around it) are an unrelated sensor thing. The two metal tabs at the top are the solenoid valve.


texts: How to fit back-up battery into the controller board?

texts:
I'm newbie in the field of PCB making and I have one relevant question. I have a controller on a PCB which has many resistor dividers and passive components.

I would like to know, if I want to make use of low power mode operations on the controller, how should I make the PCB?

Is it possible to make controller, battery and its power circuits (all Vdd and Vss) on one layer, and the other pins of controller on another layer?

Forgive me if I am asking stupidly.

Or please tell me how someone can crack such a problem.

By backup battery I mean a button cell 200-300 mAh, and controller is an 8-bit AVR/PIC that has low power modes.


texts: Connecting devices with different logic levels

texts:
The following figure is taken from this link, where the author explains how NOT to connect devices having different logic levels

He says that:

  Directly connecting the devices together (see above) will overstress
  the 3.3V device and eventually lead to device failure.

Can somebody explain me why this overstress will happen and what makes the device failure?


texts:
I need to plot the time period of sine wave (wt) in rad. Am using

                         `rad = asin (complex(Vm));`

for getting the angle in rad. While plotting the MATLAB takes 180 deg as 0, 270 deg as -90 and 360 as 0. How can I get the time period within 0 to (2*pi). I have attached the scope output of the above equation.


texts: Can I obtain a new voltage source from outputs of two cascaded linear voltage regulators in practice?

texts:
I have a device which works with 7V. I have a 7812 and 7805 already running in the circuit. Can I use the outputs of this voltage regulators to feed the 7V device?

I know this is possible in theory. But most practical voltage sources can supply current in only one direction. In other words, the device will drain arbitrary amounts of current (\$I_D\$) from the 12V grid, and give it back to the 5V grid. What will happen if the other circuit elements which are connected to the 5V grid drain current less than \$I_D\$? Will it cause the voltage on the 5V grid to rise up and the voltage on the device drop down?

Is this configuration OK in practice?


texts: Hardware test of FPGA, thousands of combinations?

texts:
My colleagues longtime ago have designed an FPGA (using VHDL) for a special purpose.
Another colleague prepared the test scenarios.

Now they want me to test this FPGA board following these written scenarios. The test bench is ready. So I have nothing to do except reading these scenarios, changing the Analog switches placed in the test bench (ADC is used in the test bench) and see the DIGITAL output on a monitor (an application was developed to show the result of FPGA computation on pc monitor)

My question is:

What is the name of this type of testing?

I searched several hours in Amazon book store to find in chapters of books written for FPGA design, something about real way of testing an FPGA with no success.

I have 5 analog inputs and the ADC will create let's say 20 digital variables for the FPGA. These test scenarios specific for this  FPGA test not all the input combination   (2^20=1048576)but at least 1000 combination.

So I should perform 1000 tests manually:

reading the scenario, manually changing the analog switch values, read the digital result on monitor)

But how about FPGA’s that have more inputs? should we test hardwarely all the possible combinations of the inputs?

Please help me. If you know a chapter of a book explaining the way we test physically (hardware) the FPGA or if we use other ways I’ll appreciate.
The keywords help me too


texts: Lighting Fluorescent lamp with plasma ball results in electric shock?

texts:
A friend of mine is a teacher and did an experiment in class. She held a fluorescent light next to a plasma ball and it lights up.

This seems logical, the electrons flow from the plasma ball through the fluorescent tube and the human body to the ground.

However, when she touched the contacts while holding the light next to the plasma ball, she got a small electric shock.

Why did the shock happen?


texts:
I found the question below in a forum and I also have same problem. Unfortunately, there is no answer at all so I will post it here hope someone could make it clear.

A gain relation in a circuit of RCL and dependent sources ends up in an H(s) which is a quotient of polynomials in s. Number of poles is the number of energy storing elements independent of each other (you can assign independent starting conditions) and zeroes depend on the behavior of H(s) when s tends to infinity and the number of poles. Some zeroes and poles can be found by inspection, this is done knowing the above and observing some conditions and values of s so that the gain becomes zero or infinity.

The questions:

s is supposed to be sigma + jw, and sigma arises so that the transform integral converges. However, when constructing bode plots, this is completely ignored. Why? Is there a physical meaning to sigma?
The effects on the bode plot of zeroes and poles are to change the slope in 20dB incrementals (bode magnitude), the gain isn't really infinite on the poles, since s is replaced by jw and if the poles are real, s being complex will never have those real values so that the bode plot goes infinite. What is the meaning of this?
A region of convergence (ROC) for s can be found, which is a range of values for s so that the integrals converge. What is the ROC useful for? What happens when the frequency is outisde the ROC? Textbooks are pretty good in showing how to find these ROCs, but not in making clear what effects they have in your circuit.


texts: High resolution resistor measurement technique

texts:
I'm working on high resolution resistor measurement system. I need to detect %1 and %5 tolerance difference. Now I set the system typologies like pic1 via analog multiplexers.(ADG708, ADG732)

R1 is my referance resistor. This tolerance %0.1 and ADC resolution is 10-bits.
I have 100R,1kR,10kR,100kR,1MR referance resistor. I can change that easly with multiplexers.

This system is must be quite precise but practical is not.

If you suggest a better solution or addition, I would be happy.


texts: Serial communucation rasperberry pi and atmega328p

texts:
I have a design system which is generate data. My system include lidar sensor and atmega328p. Atmega is driving my sensor and generate data. No problem is here.
But my aim is data processing in matlab so ı have to communication matlab and my rasperberry wireless because this project is robotic project.

I am using rasperberry pi. Rasperberry pi is the center of system. All data is gather here. it will be analyze and robot will move with this data.Rasper will send data matlab. Matlab will show graph and information also.This is Description of my project.

My problem is raspberry and atmega serial communication. I can't succeed it. How can ı solve this problem. I am beginner rasper and ı don't understand anything. A lot of people says minicom etc. I install it but ı can't see anything. Everybody says the first step is you must connect rx tx pin to rasper and send rasper ls /dev/tty this command and it will output like this /dev/ttyAMA0 but ı can't see this output also.
 raspberry pi


texts: Why don't people tend to use voltage dividers or zeners in front of linear regulators

texts:
After seeing some students yesterday that tried to use a voltage divider instead of a regulator to provide a sensor with a lower power supply, with predictable results, I started wondering about this question.

When picking a regulator, it seems many look at the required voltage drop and the power dissipation required.  Efficiency aside for the moment, if a linear regulator can drop that power within thermal limits, linear regulators are an option, and if they can't, move on to switching regulators.

If one could figure out the range of current draws, and calculate out a voltage divider that would simultaneously keep the input to a linear regulator high enough to maintain regulation and low enough such that the regulator doesn't burn away too much power across the current draw range, is this a viable approach?

I can think of a number of reasons why this might not be the best approach:  power supply rejection ratio may not be good enough on the regulator; the range of current draws that make this approach feasible might be very small, unless you use small resistors that are likely to exceed their own power ratings; its just more efficient to use a switching regulator; etc.

Also, it might be that people do this all the time, and I just haven't noticed it, or maybe a zener is used instead of the divider.  It just seems that when the power drop is too big, people mostly run to switching regulators.

Anything I'm missing?


texts: Linux Circuit Software To Calculate Power Dissipation

texts:
I am a bit new to this whole circuit simulation software, so I was hoping someone could share their years of experience with me to help me weed through this seeming jungle of software-packages.

I have a simple photo-diode and BJT amplifier circuit, and I want to calculate the power dissipation of each component in the circuit under steady-state operating conditions and look it its transient response at different points in the circuit.

Could someone please point me in the right direction to find a Linux software program that can perform these operations?

edit: I would prefer it if it was freeware.


texts:
I'm trying to build this circuit- the red area is what I'm having problems with:

What is happening is that I have 4.5 volts for like a second then it drops to 3 volts which can't run the op amp.
I did get it to work for a while but then I re-built it on a bigger board and now it drops the voltage too low. what can be the culprit?
Is it the battery or is it the over all design for the circuit that handles the biasing of the voltage?
BTW: I haven't done any electronics in like 6 years so I might have missed something basic.


texts: At which level of voltage is USB device disconnected

texts:
I have to realize a USB switch on my own. For security I have a chip (TPS2052) which has  short - circuit protection and is controlling the current. My problem is:

When I switch from one USB port to another the TPS2052 chip has a delay (ms range) until it goes from 5V to 0V. I have to do some testing with my USB switch circuit. So I have to know exactly when the USB device is disconnected. Can you tell me at which level of voltage the USB device is disconnected?

This shows a diagram. Yellow: Signal that USB device should be disconnected (= Data is also disconnected at this moment) Blue: Supply voltage of the USB port. So can I say when Data is disconnected it doesn't matter that there is still some voltage?


texts: How to debug a precision temperature controller?

texts:
I have an temperature controller which is not functioning as I would expect, as seen in the attached pictures. In addition to the pictures, there is a platinum thermometer attached to the thermometer input. I want to repair and find the issue with this controller, so any advice as to the correct approach is highly appreciated. As a fairly clueless mechanical engineer, I will try to explain my current approach.

To test the functionality of this temperature controller, I have plugged a little electric fan into the output of the controller such that at full power, the fan should turn. Meanwhile, I have plugged the controller into the wall socket. I have observed the following:

At room temperature, neither the fan nor the display of the controller respond until I elevate the temperature set point to nearly 90 C. At this point, the fan may start to buzz, but it doesnt turn. Meanwhile, the heater display turns to nearly 80.
No significant changes in behaviour are observed when placing the temperature probe under cold water.
When heating the probe, the exact temperature at which the temperature set point triggers a response changes a little, maybe 3 or 4 degrees lower. Still, the device is unresponsive at temperatures anywhere near the room temperature.

My thinking is that the temperature probe is the most vulnerable part of the device and is likely the part that has gone bad. So, from what I gather, if I short the thermometer input, then I can at least try to isolate the problem.

I assume that if I short the thermometer input, the device would simply output full power at all times.

I had assumed before looking at the circuitry that there would just be two wires across the temperature input, and I could sodder them. However, there are four as seen in the attached picture. Can I simply sodder them together to achieve the same result? Additionally, if the thermometer probe is not the actual issue, what should my approach be from there?

Any other advice and discussion of how this controller works would be greatly appreciated.

Attached images:


texts: What information Bode plot does NOT present?

texts:
The classic Bode plot (2D Bode) represent value of the transfer function (a complex number) evaluated at \$j\omega\$ (imaginary axis). It provides information on system closed-loop stability margins and also some means to estimate pole/zero of the transfer function, if not available (for experimental data).
Still, given that the classic Bode plot (2D Bode) provides transfer function values only on the \$j\omega\$-axis (i.e. only the Sinusoidal pieces of system characteristics), what information of the system characteristics (as far as modes and stability) are missing by not looking at the 3D Bode plot (Sinusoidal (\$j\omega\$) + Exponential (\$\sigma\$) information)?
In other words, what useful/practical information does the 3D Bode add to the 2D Bode?
Also, found this question useful but not enough to address my question.:
What does a Bode plot represent and what is a pole and zero of a Bode plot?


texts: Do I need to recertify a product if I add a DC to DC converter?

texts:
I have a product that has been FCC verified as an unintentional radiator, I have fixed a problem with the power that required a DC to DC converter that operates in the 100kHz to 300kHz range (added to the product). Would I need to get re-certified? Why or why not? Can you provide an requirement from the FCC?

I have my opinion and so does my supervisor, and we are not on the same page, so I will need concrete evidence to support one way or the other.


texts:
I'm building a specific PCB around the Arduino Mega 2560 platform. Based on the official Mega 2560 schematic, there is two microcontroller; the 16U2 and 2560-15AU. Both of them have their own ICSP pin header.

I plan to load the bootloader with an another Arduino as ISP. Do I just need to do the process with the ICSP pin for the 2560-15AU only or do I also need to do it for the 16U2?


texts: LM2575 switching regulator - ideal inductor and COUT sizes

texts:
I'm developing a PCB in Cadsoft Eagle as seen in the brd and sch files as per the links below:

Eagle schematic file

Eagle board file

See the images below for screenshots of the schematic and the board respectively.

My issue is with feedback I received from my board house regarding the sizes of my inductor and Cout being too small in relation to the switching frequency of my LM2575 switching regulator which as per page 7 of the datasheet is 52 kHz.

For the switching regulator sub-circuit design I carefully utilised the design procedure as per pages 13 to 18 of the LM2575 datasheet.

Based on the provided design guidance within this pages the stand out selection factors in relation to picking an inductor are:

The inductor is rated for operation with a current rating (Irating)
of 1.15 x Iload whereby I load in my case is 0.4A hence Irating
equals 0.46A.
The inductor is rated to operate with the LM2575 switching frequency of 52kHz.

The pages also provide inductor part numbers from three different manufacturers. Selection of the part number is based on the inductor value which in turn is based on the desired LM2575 Vout, maximum input voltage into the LM2575 and Iload. In my case my desired LM2575 Vout is 5V, my maximum input voltage is +24V and my Iload is 0.4A hence the inductor value as per the figure 28 on the LM2575 datasheet is 680uH which as per table 2 on page 16 of the LM2575 datasheet means the following inductors can be used: 67127050 from Schott, PE-52629 from Pulse Eng and RL1950 from Renco.

1st question: What exactly is wrong with the size of my current inductor selection as per my .sch and .brd files or above screenshots? I'm using an inductor of package 0805 as per the eagle package.

2nd question: Does anyone have any idea where I can find the Cadsoft Eagle library files for any of the three inductors? I feel one of these three should be of the right size in relation to the feedback from my boardhouse.

As for the selection of Cout, the design guidance within pages 13 - 18 doesn't mention anything regarding the size of the Cout capcaitor to be used. In my design as per links above, I'm utilising a standard 0805 capacitor which I have used all across my schematic.

3rd question: Any idea which Cout capacitor size I should be selecting?

Note: I would like to stick to using the LM2575 as I've gone quite far with integrating it within my design plus the availability of its Cadsoft Eagle library file.


texts: What does low-impedance mean in the CMOS inverter circuit?

texts:
For the CMOS inverter the text states "once the transients have settled, a path always exists between VDD and the output realizing a high output (“one”), or, alternatively, between VSS and output for a low output (“zero”). This is equivalent to stating that the output node is always a low-impedance node in steady state."

What does the last statement about low impedance mean?


texts: Meaning of + and - in an electronic component's part number

texts: I have search in the internet and I could not really get an answer for this question. "What does \$\mathbf{+}\$ and \$\mathbf{-}\$ mean in an electronic component's part number?"


texts: Where to connect unused pins operational amplifier

texts:
I am using a couple of OPA2227UA op-amps for a analog circuit. Since these are dual-op amps, one of them ended up unconnected. (The +-In/Out B pins shown below):

The datasheet says what can I do for unconnected input offset pins (it says I can let them unconnected), but it does not say what should I do with input/output pins.

Should I connect those three pins somewhere, or let them unconnected? I am worried that the unconnected pins will result in oscillation and will interfere with its neighbor pins/traces.


texts:
simulate this circuit – Schematic created using CircuitLab

If the current flows counterclockwise, the current source becomes invalid but if it flows clockwise the voltage source becomes invalid? So what would happen?


texts: I would like to know how to make a 4 to 1 multiplexer using BC549 transistors also the it has a function wherein I can select which input or output to send HIGH or LOW just like the 4051 multiplexer.


texts: What do you call a relay that self-opens on power loss?

texts:
I'm programming the simulation of some circuitry.
These are relays that will open automatically when they lose power:

Do relays such as this have a particular name?

"power hold relay"?
"single pole relay"?
"self-opening relay"?

I see that its technically a diode, a coil, and a relay, but I was hoping there was a technical name for this kind of relay.


texts: I was going over the equation for current flowing through a capacitor based on voltage and capacitance (i=C*dv/dt).  It makes sense to me in general that you can find current going through a capacitor by multiplying the capacitance by the derivative of the voltage.  From this, a constant voltage would result in zero current flow and a sine wave voltage would result in a cosine pattern.  What confused me is that this would mean a capacitor with more capacitance would seemingly have more current flowing through it, which didn't seem to make sense.  Wouldn't more capacitance mean less current going through a capacitor and more getting stored?  Maybe I'm misinterpreting the formula.  I'd appreciate help on this.


texts: Elusive SR Latch: 74118/19 – Hex SR Latch with common reset

texts:
I am working on a circuit where I need to hold a few signals until my MCU reads them.
Basically the MCU would read these lines at regular intervals (minutes? hours?) and if a line changed state at any stage during this time, it has to be recorded.
I am opting for an SR latch, to be cleared by the MCU once the read has been completed.

In this scenario a common reset channel on the IC would help maximizing the numbers of available latches in the same footprint (and make the circuit more elegant and simple).
I have found a very elusive 74118/19 (possibly NOR vs NAND). However is practically impossible to find good supply of it and even a datasheet.

Question:
Do anybody have an idea of an IC that offers this capability (SR with common Reset)?

Backup question (maybe deserving its own question):
Any suggestion on how to implement this otherwise? Looks like an SR is my only choice here, but my brain is just a drop of the ocean.

Thank you all for your help!

EDIT – to clarify a few points in the design:
CHEAP AND SIMPLE DESIGN
This is meant to be a quick, cheap and low complexity design.
The most complex part (by design) is planned to be the MCU.
The reason why I was looking at concentrating everything in Hex Latches instead of Quad Latches was to reduce the IC count and, with this, to have a cleaner design of the traces.
As far as possible I want to keep it digital and without any high frequency line anywhere (or, better said, well confined in their own "realm": MCU, comms module and voltage regulation sections).

MCU DEEP SLEEP VS INTERRUPTS
I'd rather not give too much confidence at these MCU interrupts management. On top of that, when I will get into power-optimization for the MCU I may end up having to choose between keeping the interrupts alive or saving power.
I want to keep it flexible, both capability and power-usage wise and this requires balance.


texts: How does the Array allocated in the stack?

texts:
I was testing the code below on my STM32 board, but I could't understand how the array was being allocated in the stack.

I'm assuming that there are 200 bytes of memory in STM32.

Here is the code:

void test1()
{
  char data[1000]={0};
}

void test2()
{
  char data[1000];
  data[999] = 50;
  lcdAdjustBacklight(data[999]);//just adjust back light
}

So, when I add test1() into my main() function, the program will crash when run on the MCU. Obviously, the stack is overflow. However, when I add test2() into main(), the MCU processes the program just fine. I wonder how the stack allocation works for an uninitialized array.

Edit: I finally figured it out. I checked the assembly code, in test1 the compiler allocated the memory, indeed. But in test2, the compiler optimized the array, so it does not allocated memory for it.


texts: Resistor in series with primary side of transformer failing

texts:
I was given a Trio CS 1554 Analog oscilloscope. It hasn't been turned on for at least 2 years, but probably a whole lot more.

Today I plugged it in and it turned on. It was usable for approximately 30 minutes. I then noticed that the trace line started to flicker, it then lost focus, finally a crackling sound was heard and it turned off.

I got the service manual from here.  I got to step 2, spot checking, on the trouble shooting flow chart.  I was getting no power out of the transformer.  I then checked the primary side of the transformer.  There is a voltage selection switch that is connected to the power cable.  The relevent part of the schematic is shown here:

On the actual switch there is a 100 ohm resistor between the switch and the transformer.  The resistor is shown here:

I checked the resistor with my multimeter and it was open.  There was also a dark spot in the middle, so it looked like it had failed.

I got a replacement resistor from the local electronics shop and replaced the broken resistor.  The oscilloscope turn on.  10 minutes later, after I had closed it up, I heard a crackling sound and the trace line faded and it turned off again!

I haven't opened it up again but I have a few of questions.

There is no resistor on the schematic.  What is the purpose of the resistor?  Is it just for current protection? Or, is it to reduce voltage to the transformer?  Would it run without the resistor?

Anyone have any tips for dealing with old equipment that hasn't been turned on for years?  I dont have a Variac, so I cant apply a lower voltage.  Are there any typical things that fail?  I guess the electrolytic capacitors, especially around the power supply circuitry.

Thanks


texts: Clarification on adding capacitors in parallel

texts:
I have a 5 metre strand of WS2812B LEDs, at 18W per metre.

I also have a 120V to 5V-30A power supply I plan to connect them to. The data pin will be connected to (for now), a PWM pin on an Arduino Uno R3.

Now, I've found documentation that states:

  Before connecting NeoPixels to any large power source (DC “wall wart” or even a large battery), add a capacitor (1000 µF, 6.3V or higher) across the + and – terminals

You can find that reference in Adafruit's Best Practices.

I don't have any 1000 µF caps. I do have a dozen 470 µF caps rated at 25V.

First question: Can I put two (or more) of these in parallel in order to get the same effect?

Second question: If I connect power to both ends (or even three locations) of the strip, can I run each feed from this single amalgamation of capacitors, or does each feed into the LED strip require its own?

Third question: Will it be safe to use just a single 470 µF cap in place of 1000 µF?


texts: Solid State Relay not working, am I mis-reading the data sheet?

texts:
I purchased several IXYS CPC1017NTR SS relays from Mouser.

I have 1.2v and .5mA of current running over the control input of this relay and the load side isn't connecting.

Here's a diagram of what I'm trying to do roughly (I missed connecting the positive to the load side of the relay in this drawing though)

I've confirmed with my multimeter the 1.2v/.5mA, so I must have read the datasheet wrong.

Any help would be appreciated.  Thanks!

Matt


texts: I2C: BitBanging Read/Write Issue with Pic16f877A ( OSC = 11.0592MHz )

texts:
Referring [This Link] (I2C: Unable to Read Multiple Byte using Bit-Banging method).

I created an I2C BitBanging library for Pic16f877A. But I am unable to Read/Write the EEPROM.

My Pin Configuration are :

SCK : RB0
SDATA_OUT : RB1
SDATA_IN : RB2

Rest code remains the same.

Possibly, The issue could be of the delay function as I am using OSC = 11.0592 MHZ with Pic16f877A.
but tried increasing the delay by 2 times. Issue remains the same.

Also,

#pragma config  FOSC    =   HS

Can any one help me with Possible issues and way to rectify the issue.

Note: Code remains the same as the link says. Only Pin and its required registers are changed for Pic16f877A.


texts: If a power supply is not grounded, what situations could cause electrocution?

texts:
I have a 24V power supply on one of my machines that was not properly grounded from the manufacturer. A loose screw on the board was causing this, but even after that was corrected, other factors resulted in a high resistance reading (6 ohms) from the chassis.

I've since replaced the unit for my own safety, but am curious what types of situations could have caused danger from this? I realize mains voltage can kill me, but I can't figure out how that situation would even occur.

This question is simply for the sake of learning, so any feedback would be appreciated.