texts:
I have designed the circuit around BQ24133 and in my humble opinion, chose the right components while following the datasheet. I had the PCB made, soldered the components and started testing. The next picture show the schematic from the datasheet:

At first, nothing worked. I knew the reason...an assistant profesor at my college, who has little skill in soldering, told me to tin the pads first, place the ic on the pads, we placed it in the PCB oven and I was sure the chip didn't solder properly on the PCB. I know that this procedure is a legitimate one, but I had the solder paste and didnt't know why he didnt want me to use it...

Anyway, went to another lab, used a hot air soldering station to take the chip off and saw that not all pads on the desoldered IC had solder on them which confirmed my theory. I had cleaned everything and resoldered the chip. Also, before desoldering it and resoldering, I asked this question, because I was afraid desoldering and resoldering might damage the chip.

Also had to desolder one resistor (R6) conected to OPVSET, because originaly I made a mistake connecting it to the VREF and not to the input 12V adapter. I desoldered it and soldered a through hole resistor betwen 12V and OPVSET as seen on this picture. I also soldered a LED to STAT to see everything. You will also see that I used too small footpring for the 10uF caps, but i soldered them anyway and tested them with continuity. All in all, not my best work.

After that, everything worked, but the battery charging.

Input voltage: 12V
Battery: 2S 18650 Li ion 7.4V 2900mAh
VREF: 3.3V
AVCC: 11V
VBAT: 7.13V
OVPSET: 1.1V

OUT was 7.13 when no there was no 12V adapter present, and 12V when there was a 12V adapter present.

I also used NTC thermistor and its voltage was ok.

Every measured voltage was within its limits by the datasheet.

This is my schematic (where I corrected the OPVSET resistors):

The led was on when everything was connected (see page 23, Table 3. STAT Pin Definition in the BQ24133 datasheet). I disconected the thermistor to see if led would blink...and it did. So everything should be ok, battery should charge. but there was no current going in the battery.

Yesterday, I accidentally shorted the Rsr to the GND and burned it. I dont have a replacement. I also bealive I have burned the IC with my fingers because I'm not grounded. The LED dosent work anymore (the LED works, but the STAT pin doesnt). BUT, I still get 3.3V at VREF, I get 7.13V out when adapter is not present, and 12V out when adapter is present.

I'm making another revision of the board and ordering more components, so I would like to know why dosen't my battery charge.

Quesiton: Why dosen't my battery charge? Is there something wrong with my layout or components, do I need to change them?


texts: Oscilloscope Probe - How to measure a sensitive circuit

texts:
Help needed in measuring a tiny piezo actuator.

The circuit bangs the actuator with a voltage ( max 50V ), then senses the ripples after the initial actuation.

How can I measure with an oscilloscope and disturb the circuit the least.

The response frequency of the piezo is between 80-120KHz.

I am actually reversing a circuit, I just need to see the ripples on my scope.

Here's the theoretical circuit

simulate this circuit – Schematic created using CircuitLab


texts: Eliminating ideal voltage source for node analysis

texts:
I have a circuit that I would like to convert into a conductance matrix for the node analysis by inspection method. I have, however, run into a problem. I have this 36V ideal voltage source with no resistance on its branch, which means that I cannot convert it into a current source with the Norton/Thenevin equivalent circuit theorem (or can I?).

I have thought of making the third node connected to the voltage source dependent on the first node connected to the voltage source, i.e. v1 = v1 + 36. I have tried this method, but I do not get the correct values. Am I messing up? Is there no way to handle ideal voltage sources with the node analysis by inspection method?


texts: Single cell lipo over-voltage bleeding IC

texts:
I am currently designing a 12v 10000mah (really 11.1v nominal) lipo battery pack that I am going to use for camping. This will allow me to run 12v appliances from it like fans and car chargers when i'm on the go, something I couldn't do with just a standard 5v charger.

The issue I am coming across now is how do I charge the thing? I know I can charge the battery using a CV/CC fixed 12.6v output, but how am I going to balance the cells. Now, I know the way the hobby chargers work is they attach resistors on each series cell that simply "bleeds" the individual cell down when it reaches 4.2v. I want to design a circuit similar to this.

Here's what i'm thinking of doing. Feeding the battery with a CV/CC 12.6v source then have three individual seperate circuits that I can attach to each individual series cell that will simply bleed the cell down until it reaches 4.2v.

This drawing is absolutely garbage, but it should help to get the point across of what I am trying to do:

I'm thinking of using a comparator that is powered by the cell to maintain isolation that will just switch on a bunch of resistors when the cell reaches 4.2v, does anyone have a suggestion on a way to do this?

Now, you might be wondering why I am trying to build a discrete circuit for this when there are tons of 3S lipo chargers available on ebay and amazon for very cheap. The reason I am doing this is for the learning experience. The other reason I am doing this is because I can build a charger that can actually charge the cells at 4-5 amps. I could use a bigger charger like an imax b6 to charge the pack at 5 amps, but I don't want to carry around a dedicated charger just to charge some lipo cells . I want to just plug in a 12v DC jack and be on my way, and have the charging circuit be built into the device. so no, I am absolutely certain I want to DIY this.


texts: When is a non-polarized electrolytic capacitor inappropriate?

texts:
I am recapping a vintage power supply and I've done similar before but I'm a hobbyist non-expert. My understanding has always been that using a non-polarized cap is acceptable where an polarized capacitor is specified but that, essentially, that's uncommon because the NP/BP cap will be substantially larger and more expensive anyway.

I'm hoping someone can help me understand why it would be that the 250uF/100V part I'm trying to replace is available very inexpensively (and in a reasonable package size) as a non polar electrolytic apparently intended for speaker crossovers ($3.50 currently) but Mouser has nothing at all in that spec for less than like $12 a piece.

This suggests to me that something else is going on here and I'm wary of using the cheaper "spec-compliant" non polar part because I assume I'm missing something. Are caps in speaker crossovers different or special (or worse or unreliable thus cheaper)?

Thanks for any insight. I have framed this as this specific question but if you think this bears as a jumping off point to link to or gently explain other characteristics of capacitors that I'm apparently unaware of, I'm all ears!


texts:
On the datasheet it doesn't mention an input voltage. Must the input voltage be higher than the output voltage or does it increase to 12 V if I input 8 V for example?

If so, what is the current like that it outputs?


texts: Question about cascode amplifier problem

texts:
The Rout in the circuit below is stated by my textbook to be Rout = [1 + gm2(r01||rπ2)]r02 + r01.
However, I thought the equation for Rout was Rout = [1 + gm2(r01||rπ2)]r02 + (r01||rπ2) for a cascode amplifier.
What happened to the rπ2 in parallel with the r01?


texts: Boost 433 MHz receiver module receiving signal (XY-MK-5V)

texts:
I am using some "no-name" (in fact "XY-MK-5V" stands on the board) 433 MHz receiver (and transmitter) on an Arduino project. I can receive the signals sent from my other Arduino very good (it sends with 12 V as mentioned in another question).

The problem is: I want to receive signals from other parts - such as simple power outlets wireless switches, too. When they are sitting next to my Arduino, everything is fine. When they are ~ 3-4 m away, the Arduino gets no signal (or more times doesn't get the right signal).

At that time I am using a simple ~17 cm long wire that is curly to save space soldered to the "antenna port".

What can I change in order to get a better signal?


texts:
I've been trying to implement a simple 8-bit CPU in Logisim, and have put together an ALU, register file and so on, such that manipulating a few control lines for each part allows you to determine its operation. Unfortunately I'm struggling to implement the control unit in order to coordinate the control of these signals.

A lot of the basic CPUs I can find for reference use 16-bit instructions where all of the control logic is part of the opcode itself, such as the Hack architecture specified in The Elements of Computing Systems (which I've previously completed). This makes controlling the CPU a lot easier, but I'm interested in using an 8-bit instruction format, such as that on classic 8-bit micros.

I gather that you could, for example, use a simple look-up table to make sure you output the correct control signals for each instruction (which I understand the principles of), and also that you might use a state machine for something more complex, but none of the information I can find really touches on implementation.

What is generally the simplest way to design a CU for a CPU that may have variable-cycle instructions and an instruction length that cannot directly encode all the control signals? I'm not concerned about using pipelining or any other features that would complicate the CPU's design.

Also, when designing an FSM, I understand you normally construct Karnaugh maps from a truth table in order to design the necessary combinational logic for it, but even with just 16 instructions (4 input bits) and 16 states, surely you'd have too many variables to even create a k-map from? How do you even begin constructing an FSM that complex? Again, all of the examples you can find focus on the simplest case imaginable, which is usually not a particularly useful, "real-world" one. Also, I gather that FSMs are generally not used a great deal in processor design, but for a simple CPU are they necessarily a bad idea?

Basically, I have no clue where to start designing a CU, despite having had minimal difficulty constructing the other basic elements of a CPU.


texts: How does a photodiode behave in saturation?

texts:
In my design, a photo diode is connected in reverse bias with 12V. The LDO (low-dropout) voltage regulator which is used for biasing can deliver a maximum current of 500mA

My configuration:

simulate this circuit – Schematic created using CircuitLab

What I want to know is: If my photo diode gets saturated, how would it behave? Will it behave like a current source generating maximum rated current? or a short circuit allowing 500mA of supply current directly to the TIA (transimpedance amplifier)?

I'm asking because I want to put a protection diode before the TIA, which has maximum rated input current of 100mA.

I want to know the equivalent circuit of a saturated photo diode - is it a closed switch or a regulated current source?


texts:
(I have a feeling that this question may be off-topic here because it is so utterly, enormously basic, and hardly related to engineering at all. Please bear with me...)

My phone came with a power cable that outputs 1 ampere. I have a different cable that outputs 2.1 ampere, which can be plugged in in a car's cigarette lighter socket. Is there a chance of damaging the phone in case I use the second cable? If not, why is this? Is it because an "overdose" in current simply does no harm, or because the difference is too small?


texts: How are this voltage source and resistor (separated from each other by a capacitor) re-imagined as a resistive voltage source?

texts:
I'm trying to implement a wave digital filter from this research paper:
Emulation of Operational Amplifiers and Diodes in Audio Distortion Circuits
R. C. D. de Paiva, S. D Angelo, J. Pakarinen, and V. Välimäki. Emulation of Operational Amplifiers and Diodes in Audio Distortion Circuits. IEEE Trans. Circ. Systems II: Express Briefs, vol. 59, no. 10, pp. 688 692, October 2012.
In Fig. 4(a) on page 3, Vin is shown running through a 1uF capacitor, the other connected to V+ of the op-amp. There is also a 10kΩ resistance between V+ and ground.

In Fig. 5(a) on page 4, the wave digital filter implementation of this circuit used in the paper is given. Here, the positive terminal subcircuit is re-imagined as a 10kΩ resistive voltage source in series with the 1uF capacitor.

I don't see how this transformation is valid - I know I can assume there's no current into the positive terminal of the op-amp, but even still both the voltage source Vin and the 10kΩ resistor are connected to ground.
(When I implemented this myself the results were mostly accurate compared to a SPICE simulation of the original circuit. It could also just be that the DSP math works out for WDF voltage source objects)


texts: Trying to get the 8bit to 10bit ADC Conversion formula right for Arduino with Temperature probe

texts:
I have an Arduino Diecimila and a bunch of old Phidgets 1114 Temperature Sensors.

I want to be able to get a somewhat steady / accurate temperature from these sensors inside my arduino sketches.

The formula from phidgets for the 1114 is tempC = (SensorValue / 4) - 50.

My understanding is that Phidgets have an 8 bit ADC and Arduino has a 10bit ADC.

Also read an old post here describing the use of a formula more like this tempC = (SensorValue * 0.0625) - 50.  Due to the 10bit dac needing to divide by 4 again to get this result on a 10bit ADC.

Using the analoginoutserial example I've come up with this:

const int analogInPin = A5;  // Analog input pin that the potentiometer is attached to
const int analogOutPin = 9; // Analog output pin that the LED is attached to

int sensorValue = 0;        // value read from the pot
int outputValue = 0;        // value output to the PWM (analog out)
float temperature = 0.0;
void setup() {
  // initialize serial communications at 9600 bps:
  Serial.begin(9600);
}

void loop() {
  // read the analog in value:
  sensorValue = analogRead(analogInPin);
  // map it to the range of the analog out:
  outputValue = map(sensorValue, 0, 1023, 0, 255);
  // change the analog out value:
  analogWrite(analogOutPin, outputValue);

  // print the results to the serial monitor:
  Serial.print("sensor = " );
  Serial.print(sensorValue);
  Serial.print("\t Temperature = ");
  temperature = ((float)sensorValue/4) - 50.0;
  Serial.println(temperature);

  // wait 10 milliseconds before the next loop
  // for the analog-to-digital converter to settle
  // after the last reading:
  delay(10);
}

This yields serial monitor output like so:

sensor = 303     Temperature = 25.75
sensor = 305     Temperature = 26.25
sensor = 306     Temperature = 26.50
sensor = 307     Temperature = 26.75
sensor = 303     Temperature = 25.75
sensor = 310     Temperature = 27.50
sensor = 308     Temperature = 27.00
sensor = 305     Temperature = 26.25
sensor = 306     Temperature = 26.50
sensor = 307     Temperature = 26.75
sensor = 303     Temperature = 25.75
sensor = 304     Temperature = 26.00
sensor = 302     Temperature = 25.50
sensor = 305     Temperature = 26.25
sensor = 304     Temperature = 26.00
sensor = 305     Temperature = 26.25
sensor = 307     Temperature = 26.75
sensor = 303     Temperature = 25.75
sensor = 305     Temperature = 26.25
sensor = 306     Temperature = 26.50

Which shows the temperature is about 2-3 degrees C higher than it presently is, I have a separate temp gauge here showing 24.5C

I've tried using the * 0.0625 and that just brings the value to -30, -31 range...


texts:
hi i am trying to find a formula
to reduce 1 watt 1000mw  to 0.5  watt  500mw RF
basically cut the rf power in half using an attenuator
which  kind of resistors  would be best for this

has to be on a so239 socket


texts:
Is the stack executable on the STM32F4 MCU? I want to do this:

 unsigned int buffer[3];
 buffer[0] = 0x10000FA5; //Address: 0x10000FA0
 buffer[1] = 0xA0E1; //Address: 0x10000FA4 NOP
 buffer[2] = 0xA0E1; //Address> 0x10000FA8 NOP
 __asm __volatile__
 (
   "movw R1, #0x0fa0\n"
   "movt R1, #0x1000\n"
   "ldr pc, [r1, #0]\n"
 );

In the assembly code, I fetch the content at address 0x10000fa0 (buffer[0]) to get my new program counter. The new program counter is 0x10000FA5, which is the address of the content of buffer[1]. In buffer[1] there is now an instruction (NOP) saved. Is this possible to execute?

Edit: I tried it out with GDB but I am getting following exception: prvGetRegistersFromStack (pulFaultStackAddress=0x10000f78 ) from FreeRTOS


texts: High power LED's and a computer Power Supply?

texts:
Is it possible to dynamically power a multitude of approximately 1W LED lights via a computer/computer power supply.  Ideally I would like to be able to control these LED's via a USB interface or something of a similar nature.

I know little about electrical engineering but I understand that a computer power supply can output very high wattage and I'm curious of how to most effectively utilize this to control the light via a common programmable perpetual interface and power the lights?


texts:
A little background: I have a 12 VDC "cigarette" socket in my car which is a non-switched circuit (so, always on). I'm in need of a switched socket, whereby power is cut when the car is not running. Rewiring the socket to an existing switched power source in the car is not really an option.

So I'm considering introducing an N-channel MOSFET (like this), where the gate would be driven by a USB line's +5v. There are two standard USB 2.0 ports right next to the 12VDC socket, which are both switched, so the idea is the USB ports go live when the car is started, which will drive the MOSFET to complete the 12VDC circuit. Car is shut off, and the MOSFET switches off. The peripheral hooked into 12VDC socket would only draw about 2A.

USB +5V -> Gate, with pulldown resistor to GND
Socket GND lead -> Drain
Batt GND -> Source

So,

1) Does this plan sound reasonable?

2) As I understand it, with the V(GS) at 0V (the car is off) the Drain-Source connection is essentially an open circuit. Is this accurate, or would the car battery still see a small (even negligible drain) if the peripheral is left connected while the car is off?

3) Any concerns, or better ways to achieve my result? Would a relay be more appropriate than a MOSFET?

Any advice is greatly appreciated.


texts:
I have an Arduino Mega and I'm following this PWM to Analog-Output page to create a constant DC output.

If the max output for the PWM 5 volts, is there a way to put two of these circuits in series to make a DC out that is able to go from 0->10 Volts? If so, what would that look like?


texts: Reduce discrete linear voltage regulator dropout

texts:
I am investigating the following circuit taken from here which works fine in simulation. However, while Vout rising linearly with Vin it shows a ~800mV dropout, which I don't quite understand.

simulate this circuit – Schematic created using CircuitLab


texts: When there are a lot of connections and nets, these rats nest of nets can be a bit troublesome during layout. Does anybody know how to remove/hide the rats nests?


texts: How to switch between two analog outputs with a digital output?

texts:
I have a circuit with a 74ls93 counter and I want to use one of its outputs to switch between two analog output, i.e., when the output of the counter is HIGH, the output of the circuit must be V1 and when is LOW the output must be V2. V1 and V2 are fixed selected voltages between 0 and 5 V. The output of the circuit (V1 or V2) will be one of the inputs of a microcontroller.

What is the easiest and cheapest way to do this?. I think i need something like an analog multiplexer, but i'm not sure.


texts:
I'm trying to learn how to connect an IR Receiver to an Arduino Uno. I got this IR receiver as a gift, and I'm having a hard time finding a spec. sheet anywhere online. The module looks like this:

This brick comes with three pins: an S (which I assume it stands for VSS, a - (GND) and another one that I have no idea if it should be connected to anything.

I was wondering if anybody has some experience with this module. I'm attempting to connect it to the Arduino Uno.
Thanks much.


texts: Input leakage current affect on CMOS multiplexer ( TMUX1208 )

texts:
I am working on a board that operates with the current range up to pico ampere, I am looking to include a mux to provide multiplexing (8:1 multiplexer) between the sensor and the MCU within this current range. Most of the multiplexer datasheet provides the working voltage range, but regarding the current, there is only leakage current information.

Currently, I was looking into (TMUX1208 5-V Bidirectional 8:1, 1-Channel Multiplexer). Again in the features, the supply current is mentioned.

Other than that, leakage current information is mentioned.

Here the input leakage current is mentioned to be of order uA, How does input leakage current affect the output of a CMOS multiplexer. Can anyone please guide me with this or if you have any other suggestion please let me know,


texts: avr python serial communication all data \xff

texts:
I have an ATtiny AVR imicrocontroller connected to HC-05 bluetooth module via USART(TX and RX) of the microcontroller.
The microcontroller is sending constant data (for right now) to the bluetooth module, which I am viewing as serial data using python.

The problem is that i am seeing all data as '\xff' ,or '\xfd' or ...
i.e. the MSB is always f.
I don't see a reason why this should happen.
Somebody please help!

This is my code :

void USART_initialize(int baud_value) {

//int baud_rate = (unsigned int)(((16000000)/(16*baud_value))-1);
UCSRC = ~(1<<UMSEL);                        // MODE OF COMMUNICATION
UBRRH = (unsigned char)(25 >> 8);   // SETTING BAUD
UBRRL = (unsigned char)(25);        // RATE

UCSRC |= (3<<UCSZ0);                         // 8-BIT DATA
UCSRC |= (1<<UPM1);                         // EVEN PARITY
UCSRC &= ~(1<<USBS);                        // 1 STOP BIT

UCSRA &= ~(1<<U2X);                        // NORMAL ASYNCHRONOUS MODE OF COMMUNICATION

UCSRB = (1<<RXEN)|(1<<TXEN);               // ENABLE RECEIVER & TRANSMITTER

}
int main (void) {

DDRB = 0xFF;
DDRA = 0x00;
DDRD = 0xFF;
int8_t data;

USART_initialize(9600);
while(1) {

    while(!(UCSRA & (1<< UDRE)));
    UDR = ('0b00000001');
    data = '\n';

}

return(0);

}


texts:
I tried building a foxhole radio but it didn't work. My razor blade is blued and the antenna is long enough. I don't think my speaker is the problem because I hooked up a voltmeter to it and it showed 0.00 volts.

simulate this circuit – Schematic created using CircuitLab
My coil has 50 turns of copper wire covered with varnish.


texts: Questions about circuit diagram, Lipo charger

texts:
Circuit diagram from here

I've asked couple of questions about PS and Chargers, I keep facing new issues

using the diagram above "an automatic lipo charger, sort of",why would the zener diode conduct when the battery is fully charged, and not before or after? The author says the battery will take all the current, and the zener will only conduct after the battery is charged,  I don't seem to understand the concept of the zener diode "in this circuit", Also, how to choose the voltage of that diode when using a higher or lower battery for the same circuit?

second, D5 would reduce the output voltage of the LM317T it seems, can it be placed before the Vin pin for the LM317?

If not using Zener diode, and Using a CC/CV charger, when the battery reaches full charge, is it safe to leave it plugged in for few hours? Vout (LM317) = Battery voltage (Lipo battery)
(knowing how dangerous lipos are, not talking about actually leaving it for hours, just theoretically for knowledge)


texts: 48v electric forklift battery charger with 240v power source?

texts:
I have 2 electric forklift experts giving me conflicting information and I'd like to clear up the issue. I acquired some 48 volt electric forklifts whose battery banks have a listed capacity of 1100ah @6 hour rate, and the chargers they came with require 3-phase wiring, which is not an available option in my area.  I tried to shop for a compatible charger that can use a 240 volt power source and it's on this subject that the local experts disagree.
"Expert A" told me that his shop sells a 240 volt charger that will work.
"Expert B" said his company doesn't offer such a charger because, while technically possible, it would be unethical to sell because its regular use would shorten the lives of the batteries excessively. Expert A says that his 240 volt charger wouldn't affect the longevity of the batteries. Who is correct? That charger and the batteries are very expensive and heavy so I don't want to make an uninformed decision. Any Clarification would be greatly appreciated.


texts:
I have a device in which I have used 3.7v of the lithium-ion battery for power supply and for charging this battery, I am using a tp4056 module.

when I connect a battery to tp4056, battery fully charges and tp4056 disconnect power to battery and device start run from a battery. when the battery drains approx 30mV, its again start charging until going on full.

My device runs from 3.7v to 4.2v.

Now I want to make it more reliable for my device.  When a battery has fully charged, its disconnected by tp4056 module and stop giving current to the battery and device start to run from the battery and when the battery drains approx 30mV to 50mV, charger module wakes up again and start charing and it will be affected on the life cycle of the battery.

I want when my device is connected to the adapter and if the battery is going full charge then my device should be run from the direct power supply, hence battery charge won't drain until disconnect of power.

please help me and sorry for I am not being to explain my problem as professionally.

thanks in advance.


texts:
SITUATION

Hello All, I have designed a PCB the using a MT3608 to produce 5V from an 18650 Li-Ion battery. This is my second revision of the PCB (the first one worked fine), however this one has different behavior and the only the that changed was the component layout. This circuit is being used to power the following:

an ATMega328P (internal clock 8Mhz)-pulls about 12mA
A wireless transceiver (pulls about 15-16mA)

So my circuit draw about ~30mA total. this should be well within the current range of the MT3608.

PROBLEM

The circuit only outputs ~3.7-3.9V under load. If I remove the wireless transceiver it will then output 5V. Here's the peculiar part; If I use an external DC power supply and connect it to the output of the MT3608 and then raise the MT3608's output to 5V and then disconnected the external 5V source the circuit will happily maintain 5V until I cycle power.

Does anybody have any ideas?

Two things worth mentioning:

The first PCB (that worked well) had all empty space between traces fill with a ground plane.
The second PCB has it's capacitors located physically farther away from the MT3608

Link to MT3608 datasheet


texts: When is a 5mm thick PCB a better choice than solid bus bars?

texts:
I have in my possession a 5mm thick printed circuit board. It comes from a 2000-era Sun Blade server, where it connected 4 redundant 70A power supplies.

I also have a need to assemble some high current electronics - carrying currents of 140A or more. Currently, this is accomplished with laser-cut bus bars.

None of the PCB price calculators I've tried offer 5mm thickness, and none of the trace current calculators will go beyond the 35A performance figures offered by IPC 2221.

What should I expect to spend making such a thick, high-current PCB? And is there guidance available on how to design such a thing, besides extrapolating design rules from other sources that don't address such thick and high-current designs?

I'm aware you can solder bus bars atop your PCB but I'm particularly interested in understanding the design Sun went for.

Thanks for taking the time to read my question!


texts: What is the current gain of this op-amp circuit?

texts:
I just happened to see this circuit in some lecture slides and I thought I could solve it. Unfortunately, I've been trying to check my result with an ideal simulation in LTspice and all my attempts have been wrong.

What is the current gain of this op amp circuit?

$$
I_G = \frac{I_l}{I_1}
$$

where \$I_l\$ is the current through Rl.


texts:
We have planned for design a PCIe add in card which consumes 12V and 10A (120W) minimum power.
As per PCIe specification, the PCIe card edge provides 75W (12V, 5.5A) power. I am planning to use the same power plus remaining power from ATX connector(12V) and enable both the supply.
Hence my add-in card will have two inputs:
1. Power from PCIE edge,75W
2. Power from ATX connector

Now, I am worried about how to add these power supplies to my application board.

How can I add these power inputs so that the board will get 12V and 10A?
Will ORing technique meet my needs? As per my knowledge ORing is used for zero down power application where when one power supply is down the other will run the load.


texts: What will be the Gain if the resistor value tends to infinity?

texts:
Given the circuit above, I need to find the expression for gain if the r_pi tends to infinity.

my question is will v_pi still be v_in?


texts: Can a TTL LS device (low-power Schottky) serve as an input to a basic TTL device?

texts:
A 74121 (One-shot) worked well as a reset to a counter device. There is an enable line using a 7400 NAND gate to allow or disallow the trigger to pass.

While duplicating the circuit, I found that all I have at the moment is a 74LS00. Are the outputs from the low-power Schottky devices compatible with a non-LS input?

simulate this circuit – Schematic created using CircuitLab


texts: Connect RF module to phone to find distance between them

texts:
I would like to know if it is possible to connect an RF(radio frequency) module to my smartphone and find the distance between them with an accuracy of about +/-2 meters. To find distance I believe I have to use RSSI level (Received signal strength indication). I have considered using bluetooth but I would like to find better alternatives because I need more range than bluetooth can provide. I need to measure distances up to 100m/300 feet. I found some module from ebay that transmits 433MHz. Is it possible? Thank you.

Example module:
http://www.ebay.com/itm/433MHz-100-Meters-ASK-Module-Kit-RF-STX882-Transmitter-SRX882-Receiver-Antenna-/401186085838?hash=item5d688ddbce:g:ejIAAOSwAuZX1AMm


texts:
I don't know much about electricity. I live in an old building experiencing bizarre electric phenomenon. The building might have bad wiring, I live near elevators and power distribution for the entire building in a large multi-floor building. I hear a faint humming sound through the wall 24/7 - sounds like electricity buzzing. At first, I somehow thought there was bad wiring or being near the electrical equipment was causing an excessive amount of electricity. But the more I dug into it, I think its a peculiar static electricity problem. I experienced static shocks when touching an old heater or other metal.

I notice small jolts in my bed. My theory is that the air is very dry, carpets are 100% polyester and it is pulling static electricity into my polyester mattress. The bed is now sitting on the ground because the metal frame was worse. Basically, if I place my hands and feet together on the mattress, I feel these tiny jolts in the mattress and I think they are transmission of electrons to the carpet or ground. The sheets attract a ton of lint. I think the static is flowing through the mattress or accumulating in the mattress and it feels like something is pulsating in the mattress. When I add in the humming sound, I wonder if electricity is somehow spreading into the room which then flows to the carpet. Either way, it feels like some electricity is accumulating in the air, being pulled to the polyester carpet/mattress and charging there. Ultimately, this is also being attracted to the polyester in the mattress and accumulating there. So if you lay in it or press really hard, you feel like its being shot through to the floor very gently. Similar to Morse code with small jolts to the ground. Where can static electricity come from and can there be enough to cause a sensation such as that?

Is it even possible for electricity to "spread" from the power distribution, wires or elevator power or be spread out from the power of the elevators or the old wiring through the floor or walls to create this jolting sensation? Where is it all coming from? How would enough electrons be constantly generated 24/7 on a consistent enough basis that you feel the small spasms through the mattress at virtually anytime. Could the described circumstances be caused by static electricity with polyester carpets, polyester mattress (20%) and generally dry air? It's a tiny zap. Like the static is building up in the mattress and then zapping to the carpet through my back or feet when standing on the floor.


texts: Running STP and high-current AC cables together

texts:
I am about to install a backup generator about 40m away from my house. There is no question what cables to run for the AC current (which will be 230V 50Hz up to 30A) — doubled 10AWG (6mm2) to keep resistance at acceptable levels at such distance.

But I do want to run a data cable along the AC cables: this will be needed for remote control of the generator, surveillance camera and what not. Obviously it would struggle to perform side by side with the AC cables so it will need to be shielded (STP, not UTP).

Setting aside any regulations/standards that would prohibit doing this, will STP cable work? Where would be the best place for it in the pack — in the middle (A), at the edge (B), or elsehow?:


texts: Different ways to implement soft start in SPICE modeling?

texts:
I have been modeling DC DC converters in PSpice/ LTSpice I usually use this basic logic to implement soft-start feature sometimes with little modifications, Are there different ways to implement soft-start logic.

Reference Datasheet


texts:
Does any one know why the use if this buffer in the circuit? because I think there is no filter!!

Could anyone explain this please.
Thanks and best regards


texts: Why solder mask are not applied to RF PCBs

texts:
I've gone through some of the RF PCB designs. In which solder masking on the traces are not present. Like this one

Is there a specific reason or performance issue to remove that?


texts: Connect a DC/DC converter to a virtual precision ground in KiCad

texts:
I'm trying to design a circuit which steps up 5V to 12V using a DC/DC converter and then use a virtual precision ground TLE2426 to split the 12v to +/-6V.
I'm using this design in KiCad:

I'm having trouble with the battery part of my circuit. My DC/DC converter looks like this with 12V at the output:

I'm then trying to pass the 12V and GND to the TLE2426 for +/-6V

But looking at the third image, the common pin is tied to ground and -6V. However, KiCad seems to just connect anything else tied to ground to -6V in my PCB schematic. For example, looking at my mounting holes, these are tied to GND in my eeschema but on pcbnew show up as connected to -6V. What am I doing wrong here?


texts: What happens when a microcontroller does continuous read openration on an EEPROM IC?

texts: I am currently doing testing on a product. The pcb consists of an EEPROM IC AT93C46. I connected the Oscilloscope probe to the Chip select pin, Clock, Data In and Data Out. From referring the wave forms with the data sheet, I came to a conclusion that, the Microcontroller accesses the EEPROM IC every 500ms. I read the application notes for the EEPROM IC. It has been mentioned that write operation deteriorates the IC's performance. What about read cycle?


texts: Why doesn't my TL071CP op amp act as a voltage follower?

texts:
I have the TL071CP op-amp, and I am trying to make a simple DC voltage follower, however, I only get a couple hundred milivolts at the output. Usually 200-450mV. Any idea why?

simulate this circuit – Schematic created using CircuitLab


texts: Output capacitor current of boost converter

texts: I am simulating a boost converter. The input voltage is 8 V and the duty ratio is 0.3. The load resistor is 1 ohm. I want to plot the output capacitor current. In DTs time when MOSFET is on, the capacitor current should be negative of load current. But in the simulation it is not coming like this. The simulation is ideal. What is the problem? Please help.


texts: Will this relay handle my current and voltage requirements?

texts:
I have this relay: SONGLE SRA-24vdc-cl

I want to use it to run 240V 11A device.

I can see in the datasheet it can be up to 20A (section 7, line 4-5), but the relay is so small and its legs so thin, so I am asking here before connecting it.

The 240V device should operate for 1 - 1.5 hours with 11 - 12A.

The coil is 24VDC, which I will use MOSFET to give it power (I have 300mA 24VDC adapter), and the gate will be connected to AVR MCU.


texts:
I have a L298N and I want to use it to drive two DC motors. The problem I face is that one motor is working at ~7.2V and the other one at 3.3V (it's a car, the 3.3v motor is used for steering). I will drive it with an Arduino, depedending from the data received from other sensors.

Now, I'm asking you if you can help me with some ideas to design something in order to be able to use both of them with the same L298N.

Thanks !


texts: Powering MCU with capacitor during short power off when MCU VCC comes from LDO?

texts:
I'm trying to create a solution to power an ATtiny85v MCU for maybe two seconds after a power loss to perform some power down tasks, but I don't have much knowledge with electronics. I did some searching but couldn't find an answer to my specific scenario.

The MCU's power is coming from the output of a LDO (Microchip MCP1703T or similar). With my limited knowledge, my idea is to use a capacitor across VCC and GND of the MCU to keep it running for up to two seconds. Powering the MCU with a capacitor has been covered in other questions here, but in my case the capacitor to power the MCU has to be much larger than the specified largest output capacitor of the LDO. Without any components between the MCU's "power off" capacitor and the output capacitor of the LDO, these two capacitors will be parallel connected. Wouldn't that just be the same thing as a single larger capacitor as LDO output capacitor? It would be much larger than the allowed largest output capacitor for the LDO, possibly causing stability issues. How would I go about solving this?

A few notes:
I will be doing this on a 17mm board already populated with components for other things and have very limited space. Also, how to detect power loss and how to run the MCU in low power mode is not of interest for this question unless it is of importance to the solution.


texts: Could not generate linear output analog voltage using MCP4921

texts:
simulate this circuit – Schematic created using CircuitLab

I am using MCP4921's output voltage as a control input to vary the analogue SMPS output voltage. I am able to establish successful SPI communication with the MCP but it doesn't generate expected output voltage as computed using the formulas mentioned in the datasheet. Tried various combinations of DAC configuration bit, most significant change was observed when I set shutdown bit. When set (config used: Gain - 1. Shutdown - 1), DAC output voltage starts at Vref/2 and continues until VDD. but I wish to use the entire range from 0V to VDD. Can you please suggest on how to do the same ?.

Tried the other configuration (Gain - 1, Shutdown - 0), DAC output voltage seems to vary from 0V to VDD but the linearity in the output could not be observed. VDD is generated at 2800 DAC value instead of 4095 DAC value.

Note: To achieve range from 0V to VDD, Vref was set at VDD. LDAC pin is always connected to GND. Tried both buffered/unbuffered input for Vref, didn't observe any significant improvements in the output linearity.
Thanks


texts: Why is the capacitor in this circuit not becoming an open circuit?

texts:
In this circuit you can find an RC circuit and 4A DC current source.

I thought that if we use a DC voltage source instead of a DC current source, this circuit would become open circuit after a while. Because the voltage on the capacitor is equal to the voltage source.

I've applied it the same way and thought about the case as DC current
source. I think the result should be the same open circuit result.

But it's wrong and I don't know the reason.

This is my circuit and ? symbol is my question. Why this spot's current is not zero? I mean open circuit.
This is simulink result and you can find this capacitor's current is still
4A (yellow line)!

Can you tell me why the current source in the RC circuit is not open circuit?


texts:
I'm starting a project using the Realtek RTL8305SC ethernet switch. Does anybody have a good idea of how to use it, some code for it, or even a flow diagram of how it should be used in conjunction with an Ethernet enabled PIC?

Any help would be appreciated! I'm currently wondering what I need to do to get it working with the PIC, specifically the order of events. Do I need to reset the switch before enabling the ethernet in the PIC, or do I enable the ethernet on the PIC while the switch is in reset mode?


texts:
I would like to know if its possible to 'step up' the voltage from two AA batteries (3V for Alkaline and 2.4V for NiMH) to a stable 3.3V ?

I need to find a good power source for a circuit that I'm building which controls a few LEDs with an attiny45 chip running at 3.3V.


texts: Dear all, I was designing a PCB which contains a pot like the one in the picture. I know how to connect the three pins in the left. However, can anyone tell me what are the rest two pins (the small plate in the front and back) used for and how to connect them? Shall I connect them to ground? Thanks a lot


texts: Interfacing microcontroller ,LCD and two push buttons

texts:
Problem :

I'm using PIC16F84A as microcontroller , wh1602a (LCD) [16x2] , and two push buttons.
I want to give the user two options say option 1 and option 2 on the display and the user presses one push button to hover between the options and one push button to confirm one of the options.

My attempt:

I thought about doing it as frames for example initially I start at frame one:

-> Option 1

   Option 2

then once the hover button is pressed I clear the LCD and move to frame 2 which is

    Option 1

 -> Option 2

and so on.

§ Can I move the cursor to any location on the LCD 16x2 map ?

§ How can I keep track of the cursor location ?

The manual of the LCD display is :

  http://aquacontrol.narod.ru/spravka/WH1602A-YGH-CTK.pdf


texts: Storage of electrolytic capacitors - how long?

texts: I have a high voltage (750V) high value electrolytic cap about as big as my forearm. It has been in my storage box for about 20 years. In general, do electrolytics degrade under normal storage conditions ie room temperature over such a time? Not quite sure what type it is, but probably a standard Aluminium foil, not solid state. If they do degrade, what characteristics degrade?


texts:
I am trying to make a module that will work like a queue with 4 slots. It is for an elevator and the currSt is the current state and destination is the first item in queue. 4'b1111 is like NULL. The problem here is that the queue doesn't get the input from the keyboard to be stored in the 4 free places. `

module Queue(
  input clk, slowclk,
  input[3:0] cs,
  output[3:0] currstat, des,
  input[3:0]keycode,
  output reg go
);

reg currSt;
initial currSt = 4'b1;
//1111 = empty place in queue
reg queueItem1 = 4'b1111;
reg queueItem2 = 4'b1111;
reg queueItem3 = 4'b1111;
reg queueItem4 = 4'b1111;

//continuous assignment
assign currstat = currSt;
assign des = (queueItem1 == 4'b1111)?currSt:queueItem1;

always@(posedge clk) begin
    if ((keycode == 4'b0001)
      ||(keycode == 4'b0010)
      ||(keycode == 4'b0100)
      ||(keycode == 4'b1000))
    begin
        if(queueItem1 == 4'b1111)
            queueItem1 = keycode;
        else if(queueItem2 == 4'b1111)
            queueItem2 = keycode;
        else if(queueItem3 == 4'b1111)
            queueItem3 = keycode;
        else if(queueItem4 == 4'b1111)
            queueItem4 = keycode;
        //else do nothing
    end

    //adds new key pressed to queue
    if (keycode == 4'b0001
     || keycode == 4'b0010
     || keycode == 4'b0100
     || keycode == 4'b1000)
    begin
        if (queueItem1 != keycode
         && queueItem2 != keycode
         && queueItem3 != keycode
         && queueItem4 != keycode)
        begin
            if (queueItem1 == 4'b1111
             && queueItem2 == 4'b1111
             && queueItem3 == 4'b1111
             && queueItem4 == 4'b1111)
              queueItem1 = keycode;
            else if (queueItem1 != 4'b1111
                  && queueItem2 == 4'b1111
                  && queueItem3 == 4'b1111
                  && queueItem4 == 4'b1111)
              queueItem2 = keycode;
            else if (queueItem1 != 4'b1111
                  && queueItem2 != 4'b1111
                  && queueItem3 == 4'b1111
                  && queueItem4 == 4'b1111)
              queueItem3 = keycode;
            else if (queueItem1 != 4'b1111
                  && queueItem2 != 4'b1111
                  && queueItem3 != 4'b1111
                  && queueItem4 == 4'b1111)
                queueItem4 = keycode;
            //else don't add the new one in the queue
        end
        //else if any of the slots is equal the keycode then dont add it
    end

    //check if current state matches with the request queue
    if (currSt == 4'b1000
     || currSt == 4'b0100
     || currSt == 4'b0010
     || currSt == 4'b0001)
    begin
        if (queueItem1 == currSt) begin
            queueItem1 = queueItem2;
            queueItem2 = queueItem3;
            queueItem3 = queueItem4;
            queueItem4 = 4'b1111;
            go = 0;
        end else if (queueItem2 == currSt) begin
            queueItem2 = queueItem3;
            queueItem3 = queueItem4;
            queueItem4 = 4'b1111;
            go = 0;
        end else if (queueItem3 == currSt) begin
            queueItem3 = queueItem4;
            queueItem4 = 4'b1111;
            go = 0;
        end else if (queueItem4 == currSt) begin
            queueItem4 = 4'b1111;
            go = 0;
        end

        //if current state is not in the request queue
        else
            go = 1;
    end
end

always@(posedge slowclk)//change current state to new state
    currSt <= cs;

endmodule


texts:
While shopping for perfboard/protoboard, the only products I've found listed as RoHS are brand-name items, costing several times that of the generics.

Is perfboard/protoboard inherently free of lead, etc?  Or should I pay up for the name-brand boards?  (I work on project with my children, hence my desire to avoid lead.)


texts: Designing a Combination Lock FSM: Converting State Diagram to Logic Gates

texts:
I am trying to design a Synchronous combination lock for my digital logic class. I have the state diagram, as I understand how to draw out the logic which I want to follow. However, I am struggling to convert this whole sequence of steps into digital logic. I understand how to create a state table for each of the states and their next states. But how many state tables do I need? After creating these tables how do I output "U". This stuff is all kind of foreign to me, and it is kind of hard to wrap my mind around.
Some clarification for this diagram. I want input "a" to always be activated each time a colored button is pressed (Red, Green or Blue). I chose to adress each input expression as "arg'b'" where as I could have simplified it to simply "ar" to account for a red button press because I wanted to make sure you couldn't just bash all the buttons and be able to brute force the sequence. The sequence I want to program is pressing the buttons [START][R][G][B][R] in that order.
Any help, tips, video links are greatly appreciated. Thank you!


texts:
How do components fail?

General rules with an answer per component type would be valuable.

We can work as a community to build up a single question that holds valuable information about how components fail.


texts: Power dissipation in a Darlington built with an optocoupler and NPN

texts:
I have implemented a PWM control over a relay from an Arduino. To isolate both circuits I have used an optocoupler 4N35 from Vishay. Since it cannot provide enough current flow to drive the relay, I have used a BC548B transistor creating a Darlington structure with the internal output transistor of the 4N35.

The problem is that I have simulated the circuit but then, when I try to calculate the currents in the circuit I am unable to achieve the simulated values. I don't know how to achieve the \$V_{CE(OK3)}\$ neither \$I_F\$.

$$I_{K1} = \frac{+12V_{PS2}-V_{CE(Q4)}}{K1}$$
$$I_{K1}=\frac{I_{C(Q4)}}{\beta _{Q4}}\frac{\beta _{OK3}}{(\beta _{OK3}+1)}+I_{C(Q4)}$$
$$V_{CE(Q4)}=V_{CE(OK3)}+V_{BE(Q4)}$$
$$P_{OK3}=I_FV_D+I_{C(OK3)}V_{CE(OK3)}$$
$$P_{Q4}=I_{C(Q4)}V_{CE(Q4)}$$
I hope you can help me,

SOLUTION: Take the \$V_{CE(OK3)}=0.2V\$ as a standard bjt in saturation region and all the rest came easy. Calculations and simulations matched perfectly.


texts: Make 12v stabilizer for car reverse camera

texts:
i have to mount a reverse camera on my car. The problem is that the car voltage is not stable, probably the engine makes some interferences. Infact when i turn on the car but not the engine it works. When i start the engine instead it doesn't work. I searched online and found something like this filter:
https://www.ebay.com/itm/12V-Car-Camera-Power-Relay-Capacitor-Filter-Rectifiers-for-Audi-BMW-VW/202242499757

I can buy that filter but the shipping time is very long, about two months.

I'm wondering if anyone of you knows how to make it homemade?
I think it's made with a capacitor but what type of capacitor?

Thanks in advance


texts: Can you protect yourself from Tazers by lining your clothes with aluminum foil?

texts: It seems like you could protect yourself from a Tazer by having a conductive metal in your clothing that would complete a circuit between the two prongs with lower resistance than your skin. Since people don't do this I guess it probably doesn't work. Can anyone explain why to someone without much electrical experience?


texts: difference between the LM1117-5 IC packages

texts: I'm using LM1117-5 as a voltage regulator. In the datasheet of it they have mentioned different packages like LM1117DT-5.0/NOPB,LM1117DTX-5.0/NOPB,LM1117IDT-5.0/NOPB, LM1117IDTX-5.0/NOPB , LM1117IMP-5.0/NOPB. what are the differences between this packages ( DT, DTX, IDT, IDTX, IMP, MP etc. ) and which one is suitable in which applications. ?


texts:
Im having trouble getting my head around using two mosfets to pass AC.

I have reduced my schematic to its bare bones to help keep it un-cluttered.
The aim of this circuit is to use PWM to dim a bulb running AC. the PWM circuitry and gate drive is omitted.

I am taking 25V AC rms through a bridge rectifier to allow me to maintain a DC level at the gate through the voltage divider with the aid of a cap.

The above circuit caused my lower fet to fry and also the insulation on the wire from the source to my bridge negative terminal melted.

Any assistance is greatly appreciated!

EDIT:
I have amended the circuit to eliminate the short.

But i am unclear as to how the VGS limit of 20V is not exceeded.
The output of the Divider is around 7V (more than enough for my fet).
So if the top rail initially peaks at 34V and charges the cap, then the cap will hold the gates at 7V relative to the source ( and cathode of the cap).
For the opposing cycle, the lower rail peaks at 34V, or relative to the top rail/capacitor -34V (i believe this is where my logic is incorrect).
When the bottom fet opens up, this -34v potential is passed to the source before travelling through the body diode of the top fet to the load.
if this is true, the VGS potential would be 7V (positive at the gate) + the negative 34V peak at the source passed from the drain = 41V.

I have been told in a forum elsewhere this reasoning is incorrect and a simulation proves the VGS potential to maintain at 7V.

I do not doubt the simulation may be correct, however i am failing to prove to myself either way what is happening.


texts: Procedure for cc430 rf tuning with chip antenna

texts:
I have designed the 433MHz RF PCB with CC430F5137 with ceramic 50 Ohm chip antenna from Johanson Technology. I have also used Balun from Johanson Technology to match the CC430 and 50Ohm Antenna. I have done the basic testing and it is working fine but the RF range is much shorter than expected. I know it is due to bad antenna tuning. I have kept provision of pi filter footprint in the PCB in case if need for future tuning.

Now, what are the steps to do the antenna matching? What equipment I will need to do it? Where should I start from? Is there any tutorial available? Any reference to this procedure would be a great help.


texts: How to Filter High Frequency Noise from the Voltage Source on the Input of Control Electronics of Large Machines?

texts:
Relevant Background Information
As part of my Bachelors Thesis I have to design IOT integrated control Electronics for a Pick-And-Place Machine. This specific machine has modules that can be attached to its Z axis that allows it to do different tasks. Here comes the part relevant to the question. The power supply for these modules come at 48V and have to be reduced to 24V,12V,5V,3.3V inside the module. I am deducing from the large size of the machine and the distance between the power source and the module there should be a lot of parasitic noise induced. I was thinking it would be a good idea to implement high-frequency noise filtering and then regulating the 48V to the respective voltages using buck converters. Here is a block diagram of what I had in mind:

Here comes the first question, does this sort of an implementation make sense?
What sort of a Low-Pass Filter to choose
The second question: What sort of a low pass filter should one choose in such an application? A circuit that I am familiar from Uni and was also recommended here is the RLC Low pass filter:
https://www.electronicdesign.com/power-management/power-supply/article/21808839/3-ways-to-reduce-powersupply-noise#:~:text=Filtering%2C%20bypass%2C%20and%20post%2D,switching%20or%20even%20linear%20converters.

Since R_L is the inner resistance of my circuit it isn't relevant to calculate. However, I have no idea how to choose the cutoff frequency in such an application.
If I am not mistaken the relation of the output AC signal of such an RLC should be like:
U_RL = 1/(1-(w^2)LC)*U_in
How to choose the inductor and capacitor type and values?
Now I don't know the cutoff frequency, I have no idea how to choose the L and C values either so I cant draw a Bode Diagram. I read that I could choose the cutoff frequency anywhere from 7kHz to 5Mhz, but that is an awfully large range. I have no idea on what type of capacitor or inductor to use. So I am stuck. Any help on the matter would be much appreciated, I would love to get some insight from more experienced engineers.


texts: Altium 15 - Cannot see traces in 3D view

texts:
I am new to PCB designing and I've finished creating the my first prototype board. I want to send it to get printed but I'm worried that I haven't done my traces correctly because they do not show up in the 3D viewer. Looking at other renderings from Altium I can see the traces on the top layer. Have I done this incorrectly or is there a setting I need to turn on to see them?

2D View:

3D View:


texts: How does the nRF24L01+ performance degrade with supply voltage?

texts:
I'm looking at building a small handheld unit based on an nRF24L01+ in PRX mode. It needs to be able to receive "continuously" to receive control signals that would cause an attached Atmel ATtiny to indicate some LEDs or make a PWM tone.

Since it will be battery controlled, I am considering the fact that both the nRF and the ATtiny have quite a flexible supply voltage range, I was thinking of powering the device directly from 2 NiMH AAA batteries; having a nominal voltage of 2.4V.

However, since the radio chip is rated for 3.3V typical, how is it going to perform at this lower voltage? Does the range deteriorate, or does it have some sort of internal boost regulator that simply means it'll end up drawing more current?

(See also my additional question of nRF24L01+ RX in pulsed operation to save power?)


texts: Invert or turn Aux Signal mono using Rotary Switch

texts:
Is it possible to use a 3 Pole 4 Position rotary Switch to do the following on the respective positions:

Send the Aux signal through normally
Invert Left and Right
Send the Left Signal to both outputs
Send the Right Signal to both outputs

Please excuse the crude drawing, I was just wondering, if on position one, for example, the left signal then passes through the yellow link into the right channel and cause interference.
If so, how could this be done correctly?


texts: How to get current flowing through the darlington transistor as a switch for a stepper motor?

texts:
I have a 17PM-K307-05VS unipolar stepper motor. I am building the driver for the stepper motor. The exact rated voltage and current are unknown, it seems the motor is old or discontinued, but the measured coil resistance is 6.6 ohms. For this, I am not using an IC, I am using the TIP120 darlington transistor as a switch. The picture will show the circuit of one coil of the stepper motor and the darlington connected.

My problem is when the arduino sends pulses to turn on or off the transistor, no current flows through the darlington when its on. Is this has to do with the low logic voltage? How can I resolve this problem? is there any ideas to improve my circuit or is there something wrong in the circuit?Also I noted when I turn on the circuit the base to emmitter current drops down to .324V, which is low. Any advice will be of great help!


texts: How is opamp gain calculated in this circuit?

texts:
How do I calculate the gain on each stage in this circuit?

I see a feedback but no Rg.

So here's the simulation of the fist stage of the above circuit (Replaced the MAX4477 by a LT1395). Thanks guys, learned a lot about active filters in the past hours.


texts: Why does the AVR Assembler linker think my data table is at the wrong address?

texts:
MCU:  ATmega1284
Programmer:  JTAGICE3
IDE:  Atmel Studio 7.0.2397
Language:  AVR Assembler
I have a constant data table in flash memory.  The linker thinks it is located at address 0x0090, so when I write assembly instructions to try and load the address of the table they load 0x0090.  The problem is that the table is actually located at address 0x0120.  So when I try to access the table I just get garbage.
Why does the linker think that the data table is located at a different address than where its actually being programmed?
Here is the definition of the table.
.cseg
.align 16
  lcd_init_table: .db \
  0xEF , 0x03, 0x03, 0x80, 0x02, \
  0xCF , 0x03, 0x00, 0xC1, 0x30, \
  0xED , 0x04, 0x64, 0x03, 0x12, 0x81, \
  0xE8 , 0x03, 0x85, 0x00, 0x78, \
  0xCB , 0x05, 0x39, 0x2C, 0x00, 0x34, 0x02, \
  0xF7 , 0x01, 0x20, \
  0xEA , 0x02, 0x00, 0x00, \
  0xC0 , 0x01, 0x23, \
  0xC1 , 0x01, 0x10, \
  0xC5 , 0x02, 0x3e, 0x28, \
  0xC7 , 0x01, 0x86, \
  0x36 , 0x01, 0x48, \
  0x37 , 0x01, 0x00, \
  0x3A , 0x01, 0x55, \
  0xB1 , 0x02, 0x00, 0x18, \
  0xB6 , 0x03, 0x08, 0x82, 0x27, \
  0xF2 , 0x01, 0x00, \
  0x26 , 0x01, 0x01, \
  0xE0 , 0x0F, 0x0F, 0x31, 0x2B, 0x0C, 0x0E, 0x08, 0x4E , 0xF1, 0x37, 0x07, 0x10, 0x03, 0x0E, 0x09, 0x00, \
  0xE1 , 0x0F, 0x00, 0x0E, 0x14, 0x03, 0x11, 0x07, 0x31 , 0xC1, 0x48, 0x08, 0x0F, 0x0C, 0x31, 0x36, 0x0F, \
  0x11 , 0x80, \
  0x29 , 0x80, \
  0x00 , 0x00

I want to access the table using the AVR ELPM instruction as follows...
  ;Load Z register with table address
  ldi zh, lcd_init_table >> 8
  ldi zl, lcd_init_table & 0xFF
  clr r16
  out RAMPZ, r16

  lcd_init_loop:
  elpm r16, Z+ ;load command
  tst  r16
  breq lcd_init_done
  call lcd_write_cmd ;write command to LCD
  elpm r16, Z+ ;load wait and num args
  mov  r17, r16
  andi r16, 0x7F ;extract num_args
  breq lcd_init_skip_args
  call lcd_write_bytes_from_mcu_rom ;write rom bytes to LCD
  lcd_init_skip_args:
  andi r17, 0x80   ;extract wait flag
  breq lcd_init_loop ;if wait flag is set...
  ldi  r16, 150 ;wait 150 ms
  call wait_ms
  jmp  lcd_init_loop ;go back to init loop
  lcd_init_done:

The problem is that when i try to load the Z register with the address of lcd_init_table I get the value 0x0090.  The map file confirms that 0x0090 is where the linker thinks the table is located at.
CSEG lcd_init_table 00000090

The problem is that the table isn't really located there.  The hex file shows that it is actually located at 0x0120.  Programming the MCU and looking at the flash using the memory window confirms that the table really is at 0x0120.

If I hard code the address loads based on the location in the hex file, then the code works as intended.  The problem is that I can't really do that, since the table might move as I add/remove code.  I could locate the table at an explicit address using a .org directive, but that's just a band-aid and I would like to solve the actual problem.
  ;Load Z register with table address
  ldi zh, 0x01
  ldi zl, 0x20

The device programmer settings are as follows.

The compiler setting are as follows.


texts:
can you help me identify these components?

I know this is a normal diode:

But what is this: (labelled DW1 on the board - is it a zener?)

And this? (labelled V6 on the board - zeners also look like this)

UPDATE

Came out of a chicago electric flux wire welder. Feed motor control board.
Made in china most likely as it is a harbor freight product. Not known to have any issues.

Pictures of the board front and back below, annotated.

Brown wires - power

Green wires - torch switch

Red/Black wires - motor

M - motor

P - power

SW - switch


texts:
I'm using a BTS7960 module with an Arduino to adjust the voltage for my DC motor.
When I check efficiency there is a problem.  PWM  efficiency is supposedly about 90% but mine is only about 50%.
I have a 7S3P 29V li-ion battery and a 12V DC motor. While I was using it 50% PWM mode, I calculated the efficiency of power consumption and I realized that I almost lost half power in  PWM.
How I measured the efficiency:

I put a clamp meter between the battery and the BTS7960 and I have check voltage "B +" and "B-" terminals. Voltage is 29V and current is 11 amperes so my battery is giving 320 watts.
Then I checked the consumption of the DC motor. I put a clamp meter between the BTS7960 and the DC motor and I measured voltage "M+" to "M-" terminals. Voltage is 13,6 and current is 13,8 amperes so as I understand my DC motor consumes 187 watts.

Either my PWM module efficiency is very bad or I'm doing something wrong.
The BTS7960 module became really hot while testing.
If you ask why I dropped 29 volts to 13 volts and drive the DC motor, it is because I have a 7S3P li-ion battery and I have a 12 volt Dc motor. If I can overcome the problem, I will drive a 24 volt DC motor with a 7S3P battery.
What is the reason for the high power loss?
(edit)Additional information:
My clamp meter is Unit UT210E. Also you can reach datahseet this link:
UT210E English Manual
Also I measured current with multi meter(Unit UT39C)
Lastly I made same circuit with dc-dc convertor. The energy loss in the measurement was very low and I saw this as normal aslo With dc-dc converter, the battery and cables was not very hot, but in pwm modulation, the battery, cables and bts7960 integrated was very hot.


texts:
I want to add noise to some signal. I have the option to add the noise via the software API of the system. But I also have the option to add the noise in the hardware circuit itself so there is no need to manipulate the software layer.

What would be the pros and cons of each approach? The noise is meant to hide some information that I dont want people to easily see in the signal.


texts: What does "DC Current VCC and GND Pins" in ATmega8 datasheet mean?

texts:
I'm using for some DIY project ATmega8-16PU, during the reading of the datasheet

(Datasheet Revision 2486AA–AVR–02/2013 )

I've encountered in section "Electrical Characteristics – TA = -40°C to 85°C" parameter, which is called "DC Current VCC and GND Pins". Value of this parameter is 300mA. I was looking in Internet for some meaningful interpretation of this parameter. What I found was however a lot of confusion on the topic. Here are three possible interpretation of this parameter, can you please tell me, which one is the right one.

300mA is total current into all VCC and out of all GND pins.
300mA is current into all VCC pins and there is 300mA out of all GND
pins
300mA is current into each VCC pin and 300mA is current out of each
GND pin

The most reasonable explanation supporting last interpretation I found under following link:

Allowed current thru AVR devices

Depending on which interpretation is right one, I can e.g. change package type to TQFP in order to increase my current budget.

Please note that I don't want to exceed any Absolut Maximum Ratings, what I want however is to try out exceeding test conditions in datasheet.


texts: Is a 3.3V-5V MCU runnable at "nominal" 3.3V?

texts:
I've got some 5V MCUs whose rating is 3.3V Min to 5.5V Max. My question is whether running them at a "nominal" 3.3V is OK.
I can imagine that a 3.3V source runs typically at ~3.35V, so no problem. And I know that if the voltage drops to 3.29V the MCU won't suddenly quit - probably.
The reason I ask is that I have some 3.3V components that I'd like to interface to it, and they can't handle 5V as well as it can handle 3.3V. Given that most 3.3V components max out at 3.6V, maybe I should run them all at 3.45V (if I can design the non-standard power supply)?
I guess I'm asking whether 'tis better to use a "standard" voltage, or up it a little to satisfy both sides of the equation.
Edit:
As requested: the datasheet. Please see page 423, under "DC Specification (5V MCU)"


texts: Does an LED connected to a C.C. Power Supply require a series resistor?

texts:
For the purpose of creating/repairing a lighting fixture where one or many LEDs are the only component in a circuit driven by a constant current power supply, is there any benefit to using a series resistor with the LED(s) if the forward voltage after the LED(s) is 0V?
Let's say 5 LEDs, given:

Power Supply Vout: 14-20V
Power Supply CC: 350mA
LED Voltage: 3.2 - 3.4V
LED rated current: 280 - 350mA

Since the current is being regulated by the power supply itself, and the voltage will match the necessary voltage for the circuit, can the LED(s) be the only components in the circuit and the series resistor omitted?
Thanks!


texts:
I know that transformer is a constant flux device but there is one point I don't understand.
As you know, when secondary of transformer is connected to a load, current starts to flow. This current produce its own flux (let's say F2) which opposes the main flux (F1). Then E1 (back-EMF primary side) decreases and extra current starts to flow in primary side and this current cancels F2 flux out and the F1 kept constant in transformer. Everything is OK by now but the point I don't understand is when F2 flux is canceled out by extra current in primary side, what happens to E1?

Does it go to beginning value (before secondary side current to flow)? If yes, so current in primary side should also goes to beginning value (by canceling extra current) right?
Or,

E1 stays decreased (at the point after secondary current flux decreases it)? If it is like this how is that possible? I mean there is constant flux in the core but E1 is smaller. Shouldn't it be the same since flux is same?


texts: I want to use an RF12B to communicate over radio with an Arduino, but the transceiver is rated at 3.3 V. I hear I need to use a voltage level shifter, but what do these look like and where can I find a schematic to help me hook it up?


texts: Convert sine wave from NRG Anemometer to square wave

texts:
I am hoping to interface an NRG #40C anemometer to an Arduino. The anemometer outputs a frequency which is linear with the wind speed which equates to 1.711 mph/Hz.
However the output voltage ranges from 80mV p-t-p to approximately 12V p-t-p at 60Hz, which approximates to a wind speed of 100mph. The manufacturer states that the voltage is non-linear with wind speed, so as the wind speed increases so do both the frequency and amplitude, but only the frequency is a linear increase.

I have no design experience but I am quite competent at the construction of projects. I am hoping that someone has, or able to design, a suitable circuit that will convert the variable amplitude sine wave into a square wave suitable to be fed to a digital input pin on an Arduino and then convert the frequency to the wind speed. The software side of this is quite easy

An alternative would be a frequency to voltage converter, but I am still concerned regarding what I see as a massive range of input voltages.


texts: How do I get an output file out of ngspice

texts:
I have this simple netlist

First Circuit
R1 1 2 3k
R2 2 0 6k
R3 2 3 4k
R4 3 0 2k
Vs 1 0 DC 9
Is 3 0 DC 5M
.dc
.End

In the past when running a text based SPICE program I get and output file where it tells me all of the node voltages and other simple DC analysis.  How do I get ngspice to give me these values or create an output file?  I have put

.print dc v(v1)

but I still don't get anything.


texts:
I am creating a small wind turbine, I will be using a stepper as a low-efficiency generator. I have found off-the-shelf "wind charge controllers" but would rather roll my own because I would enjoy the project more.

What is the core principle these "charge controllers" run on? I can't seem to find much information on the mechanics of them other than that they regulate the voltage & current to a battery.

Is it as simple as taking the full range from the generator (say 3-30v) and making sure the output rail is a constant voltage that the batteries can handle for charging (I.E. 12v) or is there more to it than that?


texts: What would happen to the DC bias voltage of the emitter if this capacitor is omitted?

texts: I'm not quite sure what the question means. I need to explain what would happen if I removed the  \$1.0 \mu F\$ blocking capacitor from this circuit. Howver, I'm not sure what the "DC bias voltage of the emitter" is. Is it simply the voltage as measured from base to emitter? This is for a 2N3904 transistor and an emitter-follower setup.


texts: why does current flow thru a mosfet contrary to SPICE results

texts: SPICE simulations with LTSPICE showed no current flows thru drain & source of an enhancement n-channel MOSFET with using its SPICE model - yet hooking up 5v 2A power supply across an actual device (IRLB3034PBF) yields full current flow with nothing hooked up to the gate, another words no voltage into the gate, it was entirely not attached. Is SPICE incorrect about current flow?


texts: Controlling a high voltage fan with microcontroller

texts:
I have a project in which I need to drive 48VDC 90W fan and control it using it's PWM line.

I've found a number of resources including this, which seems to state that I can directly control the fan using a PWM pin from my microcontroller.

My concern however, is due to the much higher voltage of the fan, I feel like it would be unsafe for the fan to share a common ground with the microcontroller (5v).

What should one do to control such a setup safely?


texts: Which microcontrollers that can I buy to learn such an USART, UART, RS232, USB, SPI, I2C, TTL communication?

texts:
I have a high interest in learning such an USART, UART, RS232, USB, SPI, I2C, TTL communication. I find some detail explainations about above communications in this link

And I want to have deep understanding about that by learning it using microcontroller.
There are many types of microcontroller nowadays. And I am very confused which one should I choose to learn that, since I am a newbie in microcontroller.

But I find this link and I think that this arduino starter kit would be enough for me to learn above protocol communications. Am I right? is there any cheaper one? If it is not, please recommend me the right one.

Also, are there any good reference to learn above protocols communications?

Thanks before in advance.


texts:
I want to make a a line of sight sensor. I want to drive a laser diode with constant current and aim it at a photodiode, then using a transimpedence amplifier I will monitor any changes in light intensity. The reason I am using a photodiode and a laser diode is because I want fast response times.

I have in my hands 2 OPV382 laser diodes that I fail even to turn on. I am using an LM317T to provide constant current to my laser diode. In the datasheet it states that the diode starts conducting at less than 2mA and that the maximum continuous current should be 12mA. I decided to try with a low current first just to be on the safe site but nothing happened.

(datasheet: (http://eu.mouser.com/ProductDetail/Optek-TT-Electronics/OPV382/?qs=NVJATC80C48isfMgbQ%2FZnA%3D%3D))

My circuit was a resistor between the adjust and output of the LM317T to set the current and then the laser diode connected to the output and to ground. I used various resistor values from 220 Ohms to about 70(and connected the laser diode only momentarily but still nothing).

I also added another resistor from adjust to ground to set the voltage to 2.2V that is the maximum forward voltage and again nothing. Can you explain to me what I'm doing wrong? The supply voltage is 5V(measured 4.9V)

The only thing I can think of  is the series resistance of the laser diode which is 20-55ohms according to the datasheet, could this be affecting the rest of the circuit?


texts: Adding a battery backup to a circuit with external power supply

texts:
I want to add a LiPo rechargeable battery backup to an existing RTC circuit, but I can't alter the preexisting circuit. Basically, the regulator, D2 and RTC (Existing Circuit) are all fixed and can not be reconfigured. All I have to work with is a power and ground connection which I can get 5V-Vf(diode) from. Obviously a diode, as shown, isn't enough, since the battery will also supply the charger when the supply is off:

simulate this circuit – Schematic created using CircuitLab

I know this can be done with a MOSFET, but unfortunately my theory there is a bit weak still. What type of MOSFET would I need and how would I hook it up? (Or if you have a good idea for which charger IC can feed power back, that would be welcome as well.)

A bit of detail for the curious/if required: This will be attached to a M68HC11EVBU (yes yes, you can stop laughing) on P3 to supply power to the onboard MC68HC68T1. I will put a diode at D3 and cut the trace but solder a wire at D4 so that power can get to the circuit in question. Section 6.4 of the EVBU datasheet has the schematic; the supply is on the first page of figure 6-2 (page 98), and the RTC is on the third page (page 100).


texts: What's the resistance of an electrolytic cap soldered in backwards?

texts:
I'm trying to debug a friend's AMP6 audio amp kit. It seems that an electrolytic smoothing cap on the output of a 5 V regulator has been soldered in backwards. This seems bad, but the component is going to be a little tricky to desolder because of its physical location. Because of this, I'm trying to be certain that this is the problem before attempting the job.

Before it explodes, how does a backwards cap behave? Like a 100 ohm resistor?


texts: RHPZ in converter transfering the energy in a two steps approach -> mathematical model

texts:
Think of a converter transferring the energy in a two-step approach, like a boost or a buck-boost converter: first you store the energy in the inductor during the on-time then transfer it to the load during the off-time. Should a sudden power demand occur, the converter can't immediately react and must go first through another storing-energy phase before answering the demand. This intermediate phase naturally introduces a delay in the response to a change: the current in the inductor has to grow cycle by cycle (it cannot instantaneously jump to the next current setpoint) but this current increase is hampered by the inductor value and the available volt-seconds. The mathematical model of this delay in the response is the familiar RHP zero which appears in the control-to-output transfer functions of the said converters.

Above quote is from user Verbal Kint in this answer on the question: "Effect of right half plane zero on bandwidth of control system"
Why the physical phenomenon describe above by Verbal Kint can be modelized as an RHP Zero ?
Thank you very much and have a nice day !


texts:
A question came up about common failure mode of a transistor.  Searching past posts I actually found varying answers, either open or short.  Maybe it depends on the application, and I'm missing something?

"The output of a TTL NAND gate is being used to drive a relay ON by pulling the source low.  The diode for the relay was installed backwards, effectively shorting the gate's output to the power supply.  Which component has most likely failed?

The gate's output transistor has failed open
The gate's output transistor has failed shorted"

simulate this circuit – Schematic created using CircuitLab

The book provides that 'open' is the correct answer, not 'short', but doesn't explain why.


texts: Is POR Secure Memory/peripherals on ARM common in real hardware just a feature of QEMU?

texts:
I've been implementing firmware for an ARMv8 processor recently and have been studying open-source tools along the way. I looked into the ARM virtual model in QEMU and came across something it refers to as Secure Memory. The code can be found in the memory map definition for the virtual device (defined as VIRT_SECURE_MEM):

https://github.com/qemu/qemu/blob/06e64339555096a2bc2d08c7e012b36a9977062c/hw/arm/virt.c#L114-L143

static const MemMapEntry base_memmap[] = {
    /* Space up to 0x8000000 is reserved for a boot ROM */
    [VIRT_FLASH] =              {          0, 0x08000000 },
    [VIRT_CPUPERIPHS] =         { 0x08000000, 0x00020000 },
    /* GIC distributor and CPU interfaces sit inside the CPU peripheral space */
    [VIRT_GIC_DIST] =           { 0x08000000, 0x00010000 },
    [VIRT_GIC_CPU] =            { 0x08010000, 0x00010000 },
    [VIRT_GIC_V2M] =            { 0x08020000, 0x00001000 },
    [VIRT_GIC_HYP] =            { 0x08030000, 0x00010000 },
    [VIRT_GIC_VCPU] =           { 0x08040000, 0x00010000 },
    /* The space in between here is reserved for GICv3 CPU/vCPU/HYP */
    [VIRT_GIC_ITS] =            { 0x08080000, 0x00020000 },
    /* This redistributor space allows up to 2*64kB*123 CPUs */
    [VIRT_GIC_REDIST] =         { 0x080A0000, 0x00F60000 },
    [VIRT_UART] =               { 0x09000000, 0x00001000 },
    [VIRT_RTC] =                { 0x09010000, 0x00001000 },
    [VIRT_FW_CFG] =             { 0x09020000, 0x00000018 },
    [VIRT_GPIO] =               { 0x09030000, 0x00001000 },
    [VIRT_SECURE_UART] =        { 0x09040000, 0x00001000 },
    [VIRT_SMMU] =               { 0x09050000, 0x00020000 },
    [VIRT_MMIO] =               { 0x0a000000, 0x00000200 },
    /* ...repeating for a total of NUM_VIRTIO_TRANSPORTS, each of that size */
    [VIRT_PLATFORM_BUS] =       { 0x0c000000, 0x02000000 },
    [VIRT_SECURE_MEM] =         { 0x0e000000, 0x01000000 },
    [VIRT_PCIE_MMIO] =          { 0x10000000, 0x2eff0000 },
    [VIRT_PCIE_PIO] =           { 0x3eff0000, 0x00010000 },
    [VIRT_PCIE_ECAM] =          { 0x3f000000, 0x01000000 },
    /* Actual RAM size depends on initial RAM and device memory settings */
    [VIRT_MEM] =                { GiB, LEGACY_RAMLIMIT_BYTES },
};

Note that there is also just VIRT_MEM, which is "regular", presumably non-secure, memory. They also have a VIRT_SECURE_UART.

I know that regions of memory, including MMIO devices, can be reserved for Secure World via setting the appropriate bit in the page mappings. However, this appears to be a totally different thing. What is 'secure memory' as a feature otherwise? Is this common across other devices?

I've searched around a bit and could not find any ARM devices that have any secure memory at reset; they just have regular memory that can be made secure by configuring the platform.

tl;dr
Are there some devices that have 'secure memory' at reset that only the Secure World context can access? Or is this just a one-off feature of QEMU?


texts: Reducing Voltage Ripple in a Switching Converter.

texts:
I used TI's workbench to design a simple 24 to 12V @ 6A. I have it built in a PCB board, but I started doing some power measurements and notice the output voltage ripple is quite high at loads bigger than 1A. According to the WB design, ripple should be around 100mV p-p, but I'm seeing ripples as high as 700mV p-p. Can anyone help?

This is my schematic that I got from TI"s WB:

This is my PCB Layout

And this is what I am seeing on the scope:


texts: I need a 1.95v for a VDDCORE of a microprocessor I'm using, what would be the best way to get 1.95V from 3.3v? or is a regulator the best way.


texts: Does current fundamentally determine the speed or the quantity of electrons in a curcit?

texts:
I am very much a beginner so I apologize for my ignorance. But this has been bothering me for a long time and I found little to no answers.

I know that the definition of Current is charge passing through a point per second measured in A.

My confusion is how the increase in charge passing through a point achieved when we increase the current.

My belief is by increasing the current we increase the speed of charge, thus allowing us to register charges passing through a point more frequently since they are moving in a circle. Would that be true?

I've done lots of googling but this is the only related thread that in a way confirms what i said:
https://physics.stackexchange.com/questions/183482/does-a-resistor-slow-down-the-flow-of-electrons-or-just-let-less-electrons-throu ( i apologize the link I provided the first time was wrong)

The answer does not have upvotes and I found no other proof so I am very not confident that this is true.

Could it be that increasing the current releases more particles from the terminal, thus increasing the quantity, instead of speed?


texts: Connecting ARM cortex m4 to the internet

texts:
So I would like to connect my arm cortex M4 Microcontroller from TI to the internet through the home network. The purpose is so that i can remotely control something, lets just say an LED. Where should i start and what is the cheapest method.
Please note that I am not transmitting large amounts of data nor do i need it to be super secure as security is not an a major issue. Basically I just want to control about six or seven sensors and read their data remotely.
What are your suggestions and where do you think i should start
Thanks every


texts: Does this circuit follow Kirchhoff's current law?

texts:
For the above typical circuit, when the transistor is off many texts show the current directions as shown in pink colour. I also know from basic circuit theory: "The algebraic sum of all currents entering and exiting a node must equal zero"

During the transient when the transistor is off let's stop the time and check the nodes.

I look at node m and node n and try to apply KCL:

at node m Id = I_L

at node n Id = I_L + I_x

which results as Id ≠ Id

Where am I wrong here?

(Is this phenomena similar to this situation?)


texts: if the chassis of  a DC power supply is earth grounded , and lets say I am messing around with my power supply and I touch the positive voltage perhaps through a jumper wire or a component on a breadboard and at the same time i touch the chassis do i get shocked or will current flow throw me? I understand there is no path for the current to return to the source because i did not touch the negative side, so how does the earth ground help on the enclosure ? I am just having a hard time picturing what happens when the positive side of things touches the chassis ground and how it helps... i know what happens when positive and negative touch.


texts: Collector-Base capacitance in simple FM transmitter

texts:
Here is a schematic of a simple FM transmitter. I understand that this work in the following way: the sound picked up by the mic is translated into a voltage at the base of the Q1 transistor. As the internal base-collector capacitance of a BJT depends on the base-collector voltage, the B-C capacitance changes with the sound signal. This internal capacitance forms a resonant circuit with C1, C3 and L1. The resonant frequency of this circuit changes as B-C capacitance changes, and so the signal is FM modulated with the sound signal.

But how do I work out the frequency of the FM signal by reading this schematic? Let's say there is no sound signal. I set VC1 to a known capacitance. I know that C1 is large enough so it offers no impedance for the FM signal and therefore the base is effectively grounded for the FM signal. C3 is even bigger. So therefore we have, in effect, L1 directly parallel with VC1 and B-C capacitance. To get the total capacitance in parallel with L1, I need to add VC1 and B-C capacitance.

But how do I know the capacitance of the B-C junction? Let's say I want to know the base frequency (no sound signal), how much capacitance is there? I don't see C-B capacitance as a function of C-B voltage on datasheets.


texts:
I am trying to set up a Serial Port for a PIC18F2550 Microchip. I am using MPLAB.

In the 18F2550TMPO.ASM Template the statement CONFIG FOSC = XT_XT ;XT oscillator, XT used by USB.

I need to change it, so I am looking for the right statement. I could not find CONFIG FOSC = XT_XT in the MPASM™ Assembler User’s Guide or the PIC18F2455/2550/4455/4550 Datasheet.
 I typed it into google and it did not come up anywhere.

Where would I find this information that follows the same format used in the 18F2550TMPO.ASM Template  provided by Microchip?


texts:
I have a solid state relay which needs at least 3V to activate, and I need to toggle with a 2.3V output from a microcontroller. I've also got a 6V 1A power supply which I can use to power the relay.

I understand I need to use transistors somehow and I've got the basics down, but I don't understand why I need resistors in the circuit for the transistor to work.

So my questions are: why do I need resistors, how do I know which resistor to use, and which transistor is suitable for my needs?

(The solid state relay is a Crouzet 84 134 900)


texts:
I recently stumbled upon a two-in-one NFC key designed by N-O-D-E and was astonished.

Although its original purpose is for security, I love the idea of using tact switch to decide which NFC chip is responding to the reader. So I wanted to build myself a mifare 1k version of it.

But as stated in the description:

  The antenna itself was designed using this useful online generator, and it has enough inductance to run one chip at a time. It's also intentionally tuned just outside of the 13.56MHz NFC standard, for security, so you have to basically place the tag directly on top of the reader for it to work.

This part just gave me headache.
I wanted to make myself one of this is for the convenience of carrying multiple NFC chip in a small package, so I'd like to make it respond to the reader from a reasonable distance.

I have definitely no experience in antenna designing so I did a little research.
Most Mifare tags use thin wire coil as its antenna. Those antennas have large hollow in the middle and as far as I know, if the turns of the coil are same, larger antenna hollow (area) can make the tag respond from greater distance.

But, in N-O-D-E's design, he uses much wider wire and filled the whole antenna.

which makes me really curious.
Most NFC antennas printed on a PCB are wide wire with few turns, why don't they make thinner wire with more turns and larger hollow?

At fist I was wondering if filling antenna area would have negative affect on inductance, but from ST edesign suite I know that filling the middle area may even increase inductance.

The design of on board antenna and coil antenna seems conflicting to me.
I wonder which kind of design is best suited for pcb printing and would like to know the difference between using wide and thin wires for antennas.


texts: What could be the usage of material declaration datasheet for Spartan-6 package?

texts:
I'm starting to work with FPGAs and CPLDs. like other professional EEs when I bought a Spartan-6 board, started to search in the website of manufacture (that was Xilinx) to find everything about my component. well there is a bunch of good articles and stuffs.

One of these articles is Material Declaration datasheet for Spartan-6 package. But the question is that What could be the usage of these datasheet?

How could it help to an EE?

to make it simple for you guys, I converted this datasheet to image and put it here:


texts: How to get current from radio signal circuit

texts: I followed this circuit http://www.saers.com/recorder/craig/TENewsV2/TENews68/RadioWaveEnergy.jpg to harness radiowave and turn it into dc and it seems to generate around 1.4 volts but interestingly enough when i measure the amperage of the current there is zero amp...so i am looking on how to get the amp from the circuit kindly advise


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I'm using a 16 channel digital output module (NI 9375) from National Instruments which routes 24v (from a PSU) to several solenoid controlled pneumatic valves. So a valve is open when 24V is sent to the solenoid and off when not. NI 9375 is plugged into the computer through a USB and everything is controlled by LabView. There is a default state of the valves when the instrument is resting, like valve 1,2,5 is open and 3,4 is closed. My problem is that when the USB connection is lost (i.e. computer restart or failure), all the valves closes but I would like to maintain the default state of the valves. I'm not an engineer so I was hoping if someone could direct me towards a solution. I was thinking about if there exist some kind of voltage source switch with a build in something to sense if the USB is alive or dead. If alive, everything is controlled by LabView as normal, if dead, feed 24V directly to the valves I want to have open.

Optimistic regards
Morgan Ganerød


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I have a Tesla coil driver, designed around a UCC21520 isolated gate driver. It is operating as a fixed 50% duty cycle half bridge switcher. The frequency is varied from 150kHz to 250kHz. It is driving a ~20uH inductor loosely coupled to a Tesla coil secondary.

Issue: Repetitively the high side portion of the gate driver dies, seemingly randomly as I am adjusting frequency.

It has yet to die when it is at resonant frequency of the coil. Only when I'm off resonance, and the effective impedance of the load should be highest. The system is currently only switching +- 30V and is on an isolation transformer, so I can safely measure whatever I need to.

I have examined the following:

Soldered coax directly to each gate/source of the FETs being driven. There is minimal ringing, just ~1Vpp on falling edge. I don't believe 1V below ground is killing the driver...
The power supply and half bridge I added multiple 0.1uF MLCC capacitors added, but regardless there seems to be no ringing there either.
Drive and FETs remain cool. Even immediately after the driver dies, it is cool. I just hear a buzzing sound indicating it has died.

I'm at a loss, any input would be appreciated. I have an analog scope so that is why I have no images of the scope shots. When I get more driver chips, I can try to take some.

I know the schematic shows IGBTs, they were replaced by FETs (IPW50R280CE).

Also, the full schematic in case anyone is interested...


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I have a question about these electric field strength formulas

Why is \$E_1=\frac{F}{q}=\frac{K\frac{Q_1 Q_2}{x^2}}{Q_2}\$, instead of \$=\frac{K\frac{Q_1 Q_2}{x^2}}{Q_1}\$?

\$K\$ is constant \$=9 \times 10^9\$


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In a class AB amplifier, why is the Q point much closer to the cutoff voltage as compared to a Class A amplifier which is at the center. Wouldn't this clip the AC signal if its too close to Vce.

Also, notice -Vcc, would the transistor (TR2) still operate if -Vcc is grounded?


texts: Is designing SDR SDRAM controller a difficult task?

texts:
My book says "Because of many possible modes and options of SDRAM, designing a comprehensiveand robust SDRAM controller is an involved and tedious task". Don't SDR SDRAMs follow some specific standard like all things in the technology world? Why then is does it explicitly say that it is a tedious and involved task?

The book does not name any standard for the SDR SDRAMs. However, I have found that there is something called PC100 that describes it, it is superseded by PC133. However, I have not yet found the documentation that describe them.


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In a 2 pole BLDC motor i can see the net direction of the field flux (coming from north pole and going towards south pole). But in 4 pole BLDC motor what will be the direction of the net field flux? I can only see the 4 pole rotate simultaneously (when motor spins) but what will be the direction of net field flux created by adding the magnetic field of the 4 pole together?

I am asking this question because in FOC we need to know the direction of the field flux. Most people uses encoders but encoders give the position of the rotor with respect to the fixed stator axis. How they uses encoders to know the field flux position with respect to the fixed stator axis??


texts: Safe inverter circuit to power neon indicators

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I bought some neon indicators from eBay.  I want to find a safe way to power them so we can do some experiments on solderless breadboards.

I can obviously power them from mains (120VAC/60HZ USA), but that's not safe for handling on a solderless breadboard. :)

I built the following circuit from parts lying around.  At 12VDC input I get 150V pulses at 140Hz, <1% duty cycle.  Obviously this only causes one electrode in the neon tube to illuminate.

Two questions:

How dangerous would this circuit be in comparison to 120VAC mains?  I realize this unit's maximum current output would be orders of magnitude less than mains...
Is there a simpler, better circuit that doesn't require hard-to-source components like inductors and opamps?  Full-swing AC output would be preferred from a 9VDC battery:  something kids could build without me worrying they would electrocute themselves.

I seem to recall Forrest T. Mims illustrated a simple high voltage output circuit with just a couple components, but I can't find it.

Easily sourceable components for this project include resistors, capacitors and general purpose transistors, as well as diodes, LEDs...  We also have a few wall-wart transformers we could tear apart if needed.

simulate this circuit – Schematic created using CircuitLab


texts: Multiplying twos complement binary numbers

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I have a project where I am developing a basic processing core on a FPGA from logic gates. So of course I have an ALU that I am building out of logic gates. I have no issues with the rest of the ALU functions: add, sub, shift left/right, OR, CMP etc.
However I require to multiply two signed binary numbers using twos complement which may be negative or positive depending on previous calculations. Note I am using 32 bit architecture.
If the numbers were not negative I would have no problem as I could keep adding
(e.g. A*B == A+A+A... B times) or using shift and add method. Also I don't care about processing speed as speed isn't a necessity in this project.
What is the best method for me to look at using when multiplying signed numbers?


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Art of Electronics, 3rd Ed, pg. 179, gives a model for the capacitive coupling between independent channels of an AD7510DI analog switch. The authors ask to calculate the coupling between channels given a 1 MHz signal applied to the input for the four combinations of either channel being on/off. The following figure shows a SPICE simulation of the circuit, where the signal is applied to Channel 1 and the output is taken across R2 on Channel 2, with Channel 2 input grounded (but retaining the 10k implied source impedance). In the figure, the Channel 1 is 'on' (75 Ohms) and Channel 2 is 'off' (1 Meg).

Channel 1, Channel 2 : Coupling

OFF, OFF: -43 dB
OFF, ON : -34 dB
ON, OFF : -29 dB
ON, ON  : -31 dB

It's obvious why there is least coupling when both channels are off. What I don't understand is why there is significantly more coupling when Channel 1 is on and Channel 2 is off (-29 dB) compared to the opposite situation (-34 dB). I would have thought the situations would be quite similar. I'm also confused about why both channels on gives less coupling (-31 dB) than having Channel 2 off (-29 dB).

So, qualitatively speaking, why does the greatest amount of coupling occur when Channel 1 is on and Channel 2 is off rather than both channels being on? And why is the coupling so much greater than the opposite situation when Channel 1 is off and Channel 2 is on?


texts: How do I reuse part of a schematic in multiple projects in KiCad?

texts: I would like to re-use parts of a schematic, say a microcontroller or a voltage regulator, in multiple KiCad projects. Is it possible to copy and paste blocks between eeschema windows or can this be accomplished by another means?


texts: How to stretch 1ns pulse into a 5ns pulse?

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We have a time-tagger device that records the arrival of a LVTTL signal with 0.5ns resolution.  Currently the 5ns LVTTL signal is generated by a separate commercial Avalanche Photon Diode but I would like to replace that with an in-house SiPM (https://www.sensl.com/downloads/ds/DS-MicroCseries.pdf)

The fast output of the SiPM generates a pulse that has a 1ns rise time and 1ns width.  Is there a simple way to convert this to a 5ns, 3.3V pulse?  I was hoping there would be a monostable multivibrator IC that could do the job but I couldn't find anything that fast.

Many thanks for any guidance provided...