texts:
If I have two voltage lines, say 5V and 12V, and I want to switch between using these two, is there such a device that can be controlled to connect one line, then connect the other?

I was thinking of using some relays that I have, but realized that would require two relays, one for each line. I could just turn the relays on and off separately. But is there a single device that can do the same thing? Like I could connect both 5V and 10V to two inputs, and also have two outputs, still at 5V and 12V, but have a control capability to switch between output use.


texts: If I increase the number of motors in a parallel circuit, will my current increase?

texts:
I am new to electronics, and am looking to build my own quadcopter. Before I purchase anything, I want to make sure I can get an appropriate battery to power the motors.

The battery I am looking at is a lithium polymer 3s (11.1V), 5200mAh, with a maximum discharge capacity of 30c.

The motors I am looking at are DXW A2212 DC, 3 phase brushless motors. I believe the maximum current load will be no greater than 20 amps, and the max efficiency current is at 10 amps. Assuming that there will be a constant current of 20 amps being drawn, and I add 3 more motors (4 in total), what will happen to the current drawn from the battery?

I know that the current in parallel is split up, so will my overall current drawn increase?

In the example above 2A is split up. If I reverse this, and have 20 amps * 4 (as 4 motors in parallel to each other, each drawing 20 amps), would I be drawing 80 amps from the battery? This would be logical, but I don't know if it is how motors work.

I hope this made some sense.


texts: Understanding execution of sequence of pipeline instructions

texts:
I need help in understanding the solution from solution manual. The question is from the exercise 4.22.2 of chapter 4 in the book Computer Organization and Design by Patterson and Hannessey (4th edition). The question is about branching in instruction pipeline.

  The question
    We assume that the following MIPS code is executed on a pipelined processor
  with a 5-stage pipeline, full forwarding, and a predict-taken branch predictor.
    Consider the instruction sequence:
      Label1: LW R2,0(R2)
      BEQ R2,R0,Label ; Taken once, then not taken
      OR R2,R2,R3
      SW R2,0(R5)
    Draw the pipeline execution diagram for this code, assuming
  there are delay slots and that branches execute in the EX stage.

The solution given is as follows:

  The solution

Doubts

Why there is a stall (highlighted ***) in cycle 7 for LW (4th executed instruction)? I understand that LW reads R2 which is modified by OR ( executed in delay slot after BEQ, before LW). But OR reads it in cycle 6 in the EX stage. So LW should be able to execute EX stage in cycle 7 (since full forwarding is allowed). But why its not shown like that?
Also notice that in cycle (column) 4, for BEQ instruction (2nd instruction), their is a stall (i.e. ***). This is because BEQ reads R2 which is loaded by LW (1 st instruction) in its MEM stage. So BEQ has to wait till LW's MEM completes. However the same situation occurs in instructions 4 and 5. But in this case BEQ (5th instruction) is allowed to execute its EX stage in the same cycle as LW's (3rd instruction's) MEM stage. Shouldn't BEQ (5th instruction) be stalled again to make it wait till LW's (4th instruction's) MEW completes?
Also I noticed, there are two 4th stages. In some instructions, 4th stage is labeled MEM (for example 1st instruction LW, 4th cycle) and in some instructions, its labeled MEB (for example 2nd instruction LW, 6th cycle). What are the differences between MEM and MEB? I searched whole book, but their is no mention of MEB, only in solution manual, its specified. Or may be I might have missed some pages.


texts:
Full disclosure: when it comes to electronics, I'm the type that knows enough to be dangerous. And that's kinda why I'm here - I took an electronics course in high school in 2005, but it's been a while so I've forgotten a lot...

I have two computers hooked up via a KVM switch, but I didn't like how audio was also exclusive when I switched inputs. I came across the Rane note "Why not Wye?" and built a balanced summing box so I could hear both computers at once.

Works great, except that when both computers are on, the output volume attenuates regardless of whether or not either line has sound. I notice this a lot, especially when one computer sleeps and thus cuts the audio and suddenly the music on my running PC is louder.

My circuit is the one on figure 4 of that article:

Is there a way I can make sure the output volume is consistent regardless of whether or not both inputs are present?


texts: What is the main Computer Memory Addressing Mechanism for Semi-Conductor Memory?

texts:
Most semiconductor memory is organized into memory cells or bistable flip-flops, each storing one bit (0 or 1).

How exactly are the needed '1's or '0's taken from Memory? What mechanism or algorithm?


texts: When there are two power supply circuit, the voltage solution problem?

texts:
I am an electronic beginner and I do not understand how Uab solves this circuit.

I know how this value get, but I do not understand why it should be done.

   (1)

I tried to solve it using Kirchhoff's law, but I did not know if this would work.

Please help me, tell me how I can get formula(1).


texts: What is the significance of phase margin in an open loop amplifier?

texts:
I know the importance of phase margin to ensure stability in closed loop systems, but what about in open loop systems?
I am designing a regulated common based LNA IC that operates in open loop.
Can we just ignore the phase response and just focus on the gain and bandwidth?
I ensure all the poles are on the left half plane of the s-plane but two poles are located close to each other so I got the phase is -260deg when the gain is 1V/V.
The phase is that low because the DC gain is high, 9000 V/V.


texts:
If Hartley's law is:

$$ C = 2 B \log_2 M $$

I know this equation is part of calculating the capacity of a channel. I also understand that:

\$C\$ is the digital bandwidth, in bits/second
\$B\$ is the analog bandwidth, in hertz

But I do not understand the meaning of \$M\$. Could someone please explain it?


texts: What is the role of capacitors in DC circuits like motherboard, graphic card etc?

texts: I was just reading in Capacitors in DC Circuits that "Capacitors do not play an important role in DC circuits because it is impossible for a steady current to flow across a capacitor". I think it means that a capacitor doesn't allow current to flow when it's charged. What role does it have in circuits like motherboards, graphics cards, soundboards, etc. which works on DC current?


texts: Confusion of the working principle of Isolated SEPIC converter

texts:
I am a bit confused about the current flowing in the magnetizing inductance L_m when the switch is off.
I am reading a book(Erickson & Maksimovic, Fundamentals of Power Electronics, 2020), explaining the working principle of isolated SEPIC. It is mentioned that the current in the secondary side will be (I_Lm + I_1) / n, however, this will imply I_1 is all flowing into the coupled winding on the primary side and no current is divided by the branch where magnetizing inductance lies. But if so far I've understood properly, why there will be no current flowing in L_m in this phase?
Can someone help explain it to me? Thanks in advance.
Here did I post the topologies of the converter and its current waveform which I referenced from the book.
The topology of an isolated SEPIC converter

The current flow when the switch is off (I indicated my understanding with markers)

Current waveforms on the primary and secondary side

The book text where I am having a question


texts: Understanding a dual op amp integrator circuit

texts:
I've come across this part of a circuit from a precision multi-slope ADC, it is described as a "Dual op amp integrator", but I am left confused as to what U11 accomplishes in this circuit,

This part of the circuit is switched between an external input voltage and either a positive of negative reference voltage at about 50KHz, apparently done to use a much smaller integration capacitor, and have more residue resolution, this is just to give an idea of how it is used.

simulate this circuit – Schematic created using CircuitLab

My goal is working out how each component in this circuit influences the total noise, and what frequency bands of external and internal noise it is susceptible to,

I am very limited when it comes to simulation knowledge, and have so far been deriving the relationship of what the AC gain vs frequency is of each part of the circuit moving forward, however without knowing exactly what this circuit accomplishes, I've been struggling with it.

My first thought was increasing the gain of the circuit, with U11 contributing about x16000, and U2 contributing x1000000 however this seems a little overkill, as U2 on its own could saturate on only 15uV difference across its inputs.

Second thought was some kind of sallen key low pass, that some how relied on parasitic capacitance, but every calculation for that I could find had results far above the gain bandwidth product.

The other thought was to reduce the offset voltage of U2, but in a part of the circuit where noise is critical, it seems odd.


texts:
I am trying to design layout, schematic and symbol, and then using symbol or schematic to test my design.

Here is the schematic:

And here is the layout I designed:

When I run DRC, I get the following warnings, but I hope I can ignore those:

Lastly, the simulation settings and output plot.

As you see, I get 0 no matter what the input voltage is. Am I doing simulation wrong, is there any problem with my design?


texts: Need help with a pulse/counter input circuit on hall effect flow sensor

texts:
I am having trouble wiring up a flow sensor to my pulse/encoder/counter card.

I am using a hall effect flow sensor that works fine when wired to a digital counter display.

However, when I try to connect it to my high-speed counter card, it kills the whole circuit. Here is my wiring diagram:

Troubleshooting steps:

I confirmed I get 5 VDC output from the flow sensor when the magnet rotates around to the line.
I confirmed that the flow sensor works with just the digital counter in the loop. It counts correctly as it flows.
I confirmed that the counter input module works by jumpering 5 VDC across the input

Problem:

When I connect the negative from the 5 V power supply to the "A return" terminal of the counter module, the hall effect flow sensor output drops to 1.44 VDC, and also prevents the digital counter from detecting pulses.
Removing the digital counter from the loop, the problem still remains, 1.44 VDC on the signal wire of the flow sensor.

It seems like either I'm wiring the counter wrongly (wiring it sourcing as opposed to sinking, for example,) but I don't know how else it could be wired, or perhaps the hall sensor can't output enough current to trigger the input on the module.

Any ideas?


texts: SPI not working, ATmega328 only sending 1 byte

texts:
I am trying to get SPI working on an ATmega328. This is my code:

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

#define ACK 0x7E
#define LONG_TIME 10000

//Initialize SPI Master Device
void spi_init_master (void)
{
    DDRB = (1<<PORTB5)|(1<<PORTB3);              //Set MOSI, SCK as Output
    SPCR = (1<<SPE)|(1<<MSTR); //Enable SPI, Set as Master

}

//Function to send and receive data
unsigned char spi_tranceiver (unsigned char data)
{
    PORTC = 1<<PORTC2;
    PORTC = 0<<PORTC2;

    SPDR = data;                       //Load data into the buffer
    while(!(SPSR)&(1<<SPIF));
    return(SPDR);                      //Return received data
}

//Main
int main(void)
{
    DDRC= 0XFF;
    spi_init_master();
    spi_tranceiver(6);
    //spi_tranceiver(6);
    //spi_tranceiver(6);

}

This is the output from the logic analyzer:

Notice those two comment lines. spi_tranceiver(6); If I remove those comments, I should get, from the logic analyzer:

3 times the amount of clock pulses for the blue layer.
3 times the amount of data sent, and;
3 times the amount of PORTC2 pules.

This is not the case. I get the below:

The device I am trying to SPI with isn't configured correctly. Does this matter?


texts: Implementing a very high frame rate (~1Khz) OLED display

texts: I'm interested in developing a very high frame rate OLED display capable of displaying ~1000fps with a resolution of around 1200x800 or so. This obviously has some pretty severe bandwidth requirements, and will likely require the use of an FPGA to implement a custom controller as typical display controllers don't run faster than 60-120Hz. At the risk of really showing my ignorance, with a "raw" OLED display (no controller) should I be able to drive the display at these rates? I'm sure whatever display controller comes with the display will be unhelpful, so I'd be starting from example controller code for the FPGA.


texts: Switch between USB and Bluetooth module TTL

texts:
In my project I have an MCU that I want to communicate with via 5V TTL serial. I have two methods of doing this in my circuit, USB via an FT232R (5V) and Bluetooth via an HC-05 module and level shifter (TXS0102, 3.3V <-> 5V).

In order to switch between the two sources, I have implemented a MAX4525 analogue switch IC which is operated using the 5V supply from the USB on the logic switch but supplied from a different 5V source. Is this a valid design?

EDIT: Relevant parts of the schematic...

Edit: A different approach. Power the FT232R from the internal 5V supply. Use the same 3.3V supplied to the reset pin for switching the MAX4525 chip. I believe this way the MAX4525L will always be within spec?


texts:
Tuning a PMSM Motor
We've been using brushed and induction motors more or less forever, but are now working on converting to PMSM motors.  We're doing a lot of work with the Kinetis KV31 products.  I have MCUxpresso 11.3, FreeMASTER 3.1.1.6, including MCAT, a Tower card with a KV31F120M with the SDK 2.7, the Tower motor driver card, MC-LV3PH and the little motor that comes with it.  And of course I have a stack of ap notes, including  five devoted to MCAT (none of which are all that current, and none tell the whole story).
The set-up with the default motor works fine.  The motor runs in both directions, and stops nicely.  But of course, that motor isn't big enough for our application.  The client gave me a Bohong Motors 80BLDC26011A PMSM motor.  I plugged the motor data into MCAT, and generated the motor parameters.  The motor runs one step forward, one in reverse, one more forward, then stops.  I have triple checked the motor wiring, and am reasonably certain that the motor is wired properly.  I have a scope with a clamp-on current probe.  I am using the same demo program that I used for the kit motor.
Motor parameters: Poles = 12; Voltage = 24V; Power =600W; Torque = 5.2 Nm; Maximum speed = 1100 rpm; Maximum current = 32A; Resistance, line to line = 0.09ohms; Inductance = 0.44 mH (Iq or Id not specified, assumed to be the same); Ke = 8.9 V/Khz; Torque constant =0.162 Nm/A; rotor moment of inertia = 2.7kg-cm2; max radial force 335N; max axial force = 168 N.
Values in MCAT:
Nnom (nominal mechanical speed): 1000 rpm
IsDC (Rs measureing phase current) 0.9A
Freq start (starting measuring frequency)  100Hz
Freq min 400 Hz
Ud inc (voltage increment for Ls measurement) 0.5V
Freq de (frequency decrement for Ls measurement) 100 Hz
pole pairs  6
Rs 0.09 ohms
Ld 0.00044 H
Lq 0.00044 H
Ke 8.9V/Hz
J  0.000027 kg-cm2
Iph nom (nominal phase current)  2A
Uph nom (nominal phase voltage) 24V
Nnom 1000 rpm
Note that the minimum starting frequency is 100 Hz, which means the speed at start is 1000 rpm, only 100 rpm below the maximum value for this motor.  I'd prefer to start the motor at, say, 10rpm, but that's not a choice here.
My question is how do I adjust the motor values to make it run properly?


texts:
Can anyone tell me what the compenents ringed in red are please?  I think they're resistors (The circuit is from 1978) but I can't find any reference to resistors in this form on the internet.  If they are resistors can someone tell me:

1/ How to read the rating.  i think it's top to bottom e.g. the ones on the right are 100K but a couple only seem to have two colours above the white stripe.

2/ How to identify a current equivalent.

3/ Why would the be in this form rather than the cylinder shape used on other parts of the board.

As can be seen from the bank on the right they have pretty much disintegrated; there is one at the front of that bank where the body has detached from the legs completely.

Thanks in advance.


texts: 32 channel analog control of RS485 device over 2-wire

texts:
I'd like to create a hardware switch box using 32 toggle switches to control an RS485 device remotely over 2-wire cable. For example, toggle switch #2 turns on channel 2 on RS485. Toggle #8 activates channel 8, etc.

The remote RS485 device is about 100 feet away and has it's own 12v battery.

I'm guessing there may be a chip available that can do this. However I've been researching a couple of days and have not found anything useful. Can someone help put me on the right track?


texts:
I want identify JTAG pinout on the target board, using the JTAGenum tool.
I have read the JTAGenum code, and want to clarify a few point about user configuration. JTAGenum can identify 4 mandatory pins (TCK,TMS,TDI,TDO), is there method to define the optional pins? (TRST, RST, RTCK)

Can anyone clarify about user configuration part in JTAGenum code: it's required to define the pins[] and pinnames[], and map of pin names to pins to scan with.
Would it be correct to specify settings for 8 pin JTAG header (one pin from which is GND) as follow:

byte      pins[] = { 2, 3, 4, 5, 6, 7, 8 };
char * pinnames[] = { "TCK ", "TMS ", "TDI ", "TDO ", "DIG_6", "DIG_7", "DIG_8" };


texts: Arduino - Log Data to SD Card with Computer

texts: I have an Arduino R3 Uno and I was wondering if I can log data to it using a computer's SD card slot, since I don't have an SD card shield. Any suggestions? Thanks!!!


texts: How to isolate the following relay circuit from mains?

texts: How to isolate the following circuit from mains or safely send a 5V signal from RPi to turn the relay on? I currently have a 5V signal going into the IN pin of the relay board and RPi ground to the GND pin of the relay board and it works. Is it safe even if I remove the 1.2V battery. I’m not very experienced with 220V AC.


texts: Can a lead acid battery charger and the battery be used as a UPS?

texts:
I want to connect some DC devices(< 1.5 A rating) to the output of a 12V/7Ah battery. Will this system work as a UPS if I connect a battery charger to this battery?

i.e the DC devices, Battery and charger will be connected parallely.
Will this work as a UPS?

The charger is auto-cutoff enabled to prevent over-charging.
See : http://www.amazon.in/Battery-charger-12V-1A-Adapter/dp/B01GZRBWLW
Will the auto cut-off be affected for above setup?


texts:
I recently went on a long voyage of self-teaching logic design. The final product of this is a functional 16 bit CPU that works exactly as designed in a simulator. Now I've just started looking into the possibility of putting it into silicon by way of an FPGA. I know that I will have to make a lot of adjustments in the input/output arena (the real world being different to the simulation environment) and have discovered that I did my design entirely in a program that doesn't export netlists or HDL code so all I really have is a schematic.

But, assuming that I somehow get to a point where I do have a netlist or HDL code of my design, what is my next step to get it into silicon? So far from what I've read it looks like FPGA's are my solution, but looking at the Xilinx and Altera websites makes my head spin. Am I barking up the wrong tree? Basically, I'm looking for a plain English description of what the next step is for a guy with a functional schematic of a CPU. Once I know what direction to go in, I can crack the books and figure out all I need to know about how to get there. Also a note, I am on Mac OS X but I have a Window's XP box that I can plug in if I absolutely have to.


texts:
I know that there is a separate excitation dc motor and a series excitation dc motor, but this schematic contains some series and separate coils.
What type is this motor? And what are the coils used for?


texts: Measuring resistivity of dielectric liquid

texts: Is it possible to reliably determine the resistivity of a highly resistive liquid above the breakdown voltage (i.e. after ionising the substance)?


texts: How to program external EEPROM using USBtinyISP or Pocket AVR programmer

texts:
I want to write data into an external EEPROM from my computer using USBtinyISP or Pocket AVR programmer. Is it possible to do that? I know they can be used to program microcontrollers, but not sure if I can use them to program EEPROM.

If they can't, any suggestions?


texts:
There are online designs that use a simple ferrite bolt 50 turn primary and 500 turn seccondary powering one 5 watt CFL. I attempt to customize it with:
Specs: TDK Core

(source)

Vin primary= 6V DC

Core material PC40

Saturation at 380 mT
CFL:

Power output 5,5 Watt

Nominal voltage = 34V

Current nominal = 0.18A

Breakdown voltage: Unknown

Transistors: Arbitrary
Question 1:
Is just taking half of the values, so 26 turns primary and 260 turn seccondary adequate or bad practice for my PC40 material core? Or propper approximation? Is your calculus more efficient?
Because my two seperate calculations innitially yielded 4 and 5 turns for primary.
I thought this can't be right. And the variables have to be estimated guessed,
and I'm pretty bad at that.
Question 2:
Can you come up with a better more efficient design by calculus?
Or is 4 or 5 turns primary pretty close to optimal here or should I go with 26?, or YOUR value?
Can your calculus yield a more efficient N1/N2 for the given specs?
I know that primary inductance leakage plays much less of a role in cfls than in other circuits, but:
Question 3:
Is it the primary inductance leakage which causes the voltage spike on the secondary when the load circuit side opens by a glow starter, or even without a starter, when it's normally closed?
Or what inductance specifially cause the voltage spike to overcome breakdown voltage?
Thanks for taking a look at this community!
I believe together we can solve many electrical problems!


texts: MCP6N11 voltage reference and output problem

texts:
I am currently trying to setup an instrumentation amplifier and I used MCP6N11. Basically I'm just trying to test the instruamp to output a certain voltage gain before I connect it to my actual circuit. I created a wheatstone bridge with an output of 2.54 and 3 volts at each leg. Therefore I have 0.46 volts difference If I input it to the intru amp. I just wanted to amplify the output at around 1 volt, therefore I need a gain of 2.

Alright, I set-up the instru amp using the standard circuit based on the datasheet of mcp6n11. I choose 5k for RF and Rg resistor which is also based on the datasheet to have a gain of 2. Now the problem is I am not getting any valid output that is near on my desired gain..I tried to conect the Vref to ground then the ouput is 0, when in Vdd the output is 5volts, when I try to connect it to a 2.5 voltage then it would just output a 2.5... I cant really figure out what is wrong, can any one help me how to properly setup the circuit, should I just leave the Vref hanging? I also tried to disconnect both Vinputs and I'm getting the same result.  Here is the schematic

https://kg4vlw.bl3302.livefilestore.com/y2pKKagie1d4aOL-3hLpd0Dlehoh4RG8f4qeQSCCL3gAe_bgA4fLAghwMIrlpHeoxoOClvQ3Hv31gPp2NRt4BQY0swEf5RWn1JQg31ou_zbVWZ4p18dxjp1oLS5KvZl1RYYNyRUWcUSGpuvGfJUAHIz-A/schematic.png?psid=1

Note: I read some similar post like this but it wasnt confirmed if the problem was solved or how.

Thank you in advance


texts: A spark coming from phase cutter to control AC Induction Motor using Arduino

texts:
So I have a circuit diagram to phase cut and then controlling speed of AC Induction Motor. With the code from arduino, I am able to know the zero cross and then cut the phase.

It was working well when I dont cut the phase too much, and then after that I try to cut it bigger. And something blew up, when I checked it, from the bottom(the other side of pcb) of 30K resistor there's something black mark in there, so I think it was from the resistor, but the resistors itself are fine, no black mark or some hint that the resistor is blew up. Then I checked it again, I cleaned up the black mark then I see the resistor's pin/feet's solder was not in the shape I was soldered(Its like the lead is blew up).

So was it because I'm soldering it bad? or is it there's a jumping electricity from Phase to Neutral on the pcb?

and this is the code from arduino, I think there's nothing wrong in here but who knows..

int AC_LOAD = 3;    // Output to Opto Triac pin
int dimming = 128;  // Dimming level (0-128)  0 = ON, 128 = OFF

void setup()
{
  pinMode(AC_LOAD, OUTPUT);// Set AC Load pin as output
  attachInterrupt(0, zero_crosss_int, RISING);  // Choose the zero cross interrupt # from the table above
}

//the interrupt function must take no parameters and return nothing
void zero_crosss_int()  //function to be fired at the zero crossing to dim the light
{
  // Firing angle calculation : 1 full 50Hz wave =1/50=20ms
  // Every zerocrossing thus: (50Hz)-> 10ms (1/2 Cycle)
  // For 60Hz => 8.33ms (10.000/120)
  // 10ms=10000us
  // (10000us - 10us) / 128 = 75 (Approx) For 60Hz =>65

  int dimtime = (75*dimming);    // For 60Hz =>65
  delayMicroseconds(dimtime);    // Wait till firing the TRIAC
  digitalWrite(AC_LOAD, HIGH);   // Fire the TRIAC
  delayMicroseconds(10);         // triac On propogation delay (for 60Hz use 8.33)
  digitalWrite(AC_LOAD, LOW);    // No longer trigger the TRIAC (the next zero crossing will swith it off) TRIAC
}

void loop()  {
  i = 90;
    dimming=i;
    delay(10);
}

For the specification, R1, R2, R5, R6, R7 are 1W, R3 and R4 are 1/4 W, all capacitor are 630V, and BR1 is 1A.

simulate this circuit – Schematic created using CircuitLab


texts: Phototelectric smoke sensor with microcontroller

texts:
I am trying to connect a photoelectric smoke sensor with Atmega328. The smoke sensor IC has pin 7 as the I/O pin which gives a 9V when smoke is detected. I have connected this pin to the input pin of the micro-controller through a simple potential divider. But when I connect the sensor to micro it gives false alarm after some time and works fine when independent.
I have kept all the wires short to avoid any capacitive loading and have internally pulled down the pin.
Any leads where I am going wrong?


texts: Reed switch or Hall effect for motorcycle speedometer?

texts:
I'm trying to build a speedometer for my motorcycle using an Arduino and I'm not sure whether to use a reed switch or a Hall sensor. The sensing distance is about 5-10 cm (the distance between the wheel and the sensor / switch).
The only sensor I can get is a 3144 one (that's all the information I got about it...)

Is the distance too great for sensing? It only needs to check if the magnet is around the sensor, nothing more.


texts: Impulse response of a series RLC circuit

texts: Is there any specific impulse response (like there is one for a RC circuit) for a series RLC circuit and a LC circuit with the voltage taken across the capacitor or do we just say that the impulse responses for the 3 cases (under damped, critically damped and over damped) are too complex to be written though they do exist?


texts:
Assume this transfer function. How would you graph \$\omega^2\$?

Apparently, the solution just says you would graph 0.1 by itself for a -20 dB curve. Could someone explain? I also have a screenshot of the magnitude Bode Plots which I am not understanding where w^2 is factored in. Thank you


texts:
I am looking for the correct RFID tag/reader system for my design. The general block diagram of the system is above. The requirements for the system are as follows:

Passive tags of some form and an active reader; the reader will be
interfacing with an Arduino or equivalent.
Up to 50 tags can be located in each zone, with a total across all
zones of up to 70 tags.
No writing of the tags is required or the specific locations of tags; just reading
which tag is in which zone.
No time requirement on the scanning; a number of seconds to find all
the tags is perfectly fine as the tags are stationary for minutes at a time.
A low cost system is preferred.

It seems like the best option would be a mid-range transmitter in the center, but I'm not sure about 1) the best system to get the required range, and 2) a way to determine which zone each tag is in. The other option I was thinking was a large NFC antenna/reader in each zone or one encompassing the entire system, but that probably has its own limitations.


texts: What do chips like ELM327 and STN1110 do?

texts:
What problems are the chips ELM327 and STN1110 solving?

If I connect the necessary interface ICs (I mean dumb ICs, like level shifters, inverters,  etc., not pre-programmed devices like ELM327) between the OBD pins and a suitable micro-controller, can I not read OBD data? I suspect these devices help in simplifying the software. Is that right? If so, what is the big problem they solve?

And if I don't want to use these chips, what do I need to know to start reading data from the port using just the dumb interface ICs and a microcontroller? I really don't wan't to depend on a closed-source product.


texts: Designing a single-board computer and getting it manufactured

texts:
I would like to design something like the Raspberry Pi and chromebox and get a few manufactured as a hobby learning experience.

I come from a background in theoretical computer science and mathematics, absolutely no experience in dealing with hardware. Where do I even begin?


texts: How to get rid of "Invalid opcode 0x002A at PC=0x004" in ISIS Proteus?

texts:
I have used ATmega 8 and have simulated a circuit to use interrupts, when i give an external interrupt i.e. when a push button is pressed all the LEDs connected to PORTB supposed to be lit up, but i am getting this error, What to do?
This is the code i have used

#include<avr/io.h>
#include<avr/interrupt.h>
#include<util/delay.h>
#define F_CPU 4000000UL
#define DataDDR     DDRB

#define DataPort    PORTB
ISR(INT0_vect)
{
    unsigned char i, temp;

    _delay_ms(500); // Software debouncing control

    temp = DataPort;    // Save current value on DataPort

    /* This for loop blink LEDs on Dataport 5 times*/
    for(; ; )
    {

        DataPort = 0xFF;

    }

    DataPort = temp;    //Restore old value to DataPort
}

int main(void)
{
    DDRD = 1<<PD2;      // Set PD2 as input (Using for interupt INT0)
    PORTD = 1<<PD2;     // Enable PD2 pull-up resistor

    DataDDR = 0xFF;     // Configure Dataport as output
    DataPort = 0x01;    // Initialise Dataport to 1

    GICR = 1<<INT0;                 // Enable INT0
    MCUCR = 1<<ISC01 | 1<<ISC00;    // Trigger INT0 on rising edge

    sei();              //Enable Global Interrupt

    while(1)
    {
        if(DataPort >= 0x80)
            DataPort = 1;
        else
            DataPort = DataPort << 1;   // Shift to the left

        _delay_ms(500); // Wait 5 seconds

    }
}


texts:
Good day,

I have duplicated this circuit using a 40106 hex inverter to drive a motor using pwm. The only difference in my design was to switch out the transistor stage for an Irfz34n MOSFET. The motor is a 12v 2amp drill motor. When I tested it, I received decent pwm, adjusting the motor speed a little, however the MOSFET almost burned up immediately. I have bought a heatsink for test #2, however I'm concerned I am missing a crucial variable regarding thermal conductivity. Although MOSFET gate impedence is high, should I have a small resistor to check current along with a pulldown resistor? The invertor going low seems to me would take care of floating charge but I am still learning. I'm also concerned a resistor to the gate would slow the Gate charge time and mess with the pulsed switching speed. Any thoughts would be appreciated.

Edit: I should add, the motor stage is powered independently with a 12v lead acid battery.


texts:
I have bought a motor from amazon. But the problem is no data is provided with it.
Now I want to calculate the torque of the motor. I have measured the current and voltage of the motor.
At 8.57V it consumes 0.05Amps of current. Now I want to calculate its torque.
Size of motor- 1cm dia and 3 cm length 200gms and cylindrical in shape.
The method I used is taking Electrical power= Mechanical power
So the electrical power for the motor is \$ 8.57V\cdot 0.05A=0.4285 W\$
Mechanical power is \$F\cdot v= 0.4285[W]= F\cdot 10[m/s]\$
\$F= 0.04285\ N\$
Now torque \$T=F\cdot r\$
\$T=0.04285\cdot 0.01\$
\$T=0.004285\ Nm \$
So it this calculation correct or not.
Also what does T=0.04285Nm signifies in practical terms for example- it can lift 0.04285N weight for 1 meter vertically.
Also how to calculate how much weight it can carry horizintally.


texts:
I have a summer midterm project due this Thursday.  The assignment is to get this circuit:
http://i.stack.imgur.com/D05wY.jpg

to create this graph of dB vs frequency at the voltage probe point of N1; I am giving it 1 V AC, but 0 V DC as shown
http://i.stack.imgur.com/ir7f8.jpg

it is a Bandpass filter for 0.5 Hz and the program used is B2Spice

I need help choosing the correct values for the resistors and capacitors; I already have the transfer function and component relationships
-- see my comment below for picture

I am not sure how to tackle this problem and my professor didn't help me very much or answer my questions very well.  I need to find the corner frequency and RC time constant? There are 3 poles in the target graph? Any help is appreciated, thank you.


texts: Assembler i8080 proccessor. Dividing two 16bits numbers

texts: I would like to ask you about division algorithm which I can implement in Assembler for i8080 processor. I know the easiest method is dividing by repeated subtraction but it is very slow. I found many division algorithms but many of them are very very difficult. Can someone give me advice?


texts: Capacitor Array calculation to simulate high-voltage Regen in Electric Vehicle

texts:
Good morning group, I was asked something of a puzzle: We currently have an experimental EV car powered by a large nickel-salt battery. With the ignition on and foot off the 'gas', the battery shows 370 volts, with a small draw of 1 amp. While driving, I've seen up to 100 amps delivered to the motor.

I've been asked to simulate a 'regen' system so we can test our Inverter. I need to supply 30 amps of energy back to the battery for a duration of 30 seconds. I have seen high voltage caps out there (and am very much aware of how dangerous this level of energy is), however I'm stumped on calculating exactly which capacitor size I am looking for, or how I would calculate resistance to assure a 30 second delivery time.


texts:
What is difference of between pulse-triggered FF(Flip Flop) and edge-triggered FF.

Let me know please.


texts:
I work at a manufacturing plant (in software engineering) and we have 3rd party hardware and software that monitors industrial machinery (primarily speeds).

For training and testing we need to be able to emulate one of the machines. The 3rd party hardware is based on the Omron CP1L-EM30DT1-D PLC  - (http://datasheet.octopart.com/CP1L-EM30DT1-D-Omron-datasheet-12510914.pdf)

I was going to build something simple using a variable speed DC motor and encoder wheel to generate pulses, but then it dawned on me, can't I just use an arduino and software to send variable frequency pulses? It doesn't need to be very accurate. We'd probably want a range of 1,000 to 60,000 per hour.

I'll admit that I know nothing about PLC's (yet), so I'm looking for guidance.

What would I need to send pulses to this PLC from the arduino (I'm assuming I need 24v DC so would have to switch that via a relay)? I'm trying to get some information from our vendor too. They said I could do something simple with a push button (but I'm trying to get more info). Not sure if this would help determine what I need to do.

Initially, I'll use constants in the sketch to set the speed on startup, but long term, I'd add some kind of speed control using a rotary switch or pot and hard buttons for stop and start.

Thanks in advance

Mark


texts: Control of a coreless DC motor using a PWM and a mosfet

texts:
I'm using 4 Si2302 logic level mosfets to drive 4 coreless dc motors. The speed of the motors is control led by the PWM signal from an Arduino Pro Mini. The power supply for the boards is a 3.7V (4.2V when fully-charged) 500mAh 50C Lipo.

The circuit is setup in the following way:

Source to ground
Gate to PWM pin with a 10KΩ resistor to ground.
Drain to motor terminal 1
Motor terminal 2 to Vcc
Diode placed across the motor terminals

simulate this circuit – Schematic created using CircuitLab

The motor gets its RPM value via a joystick which is connected to an Analog Input on the Arduiuno. This is then converted to a 0-255 value and outputted at the PWM output.

I'm facing the following problems with the circuit:

As soon as I supply power to the circuit the Motors run at full RPM till the Arduino  starts taking data from the joystick. It then settles down to the RPM corresponding to the joystick position. Is there any way to counter this so that the motors remain switched off until the Arduino starts receiving values from the joystick ? (My understanding was that the 10KΩ Rgs resistor would take care of this.)
The second problem is that the mosfet never fully switches off. This happens even when the joystick is at the 0 position. I have also tried switching the pins HIGH and LOW, however there is still movement in the motor. Is there any remedy to this problem?
When I measure the resistance between Gate and Source, the mosfet shows around 6K ohms. Shouldn't this be around 10KΩ since the Rgs resistor is 10KΩ ? Is this a sign that the mosfet is damaged ?


texts: Weak contact on low voltage DC device causing noise. How?

texts:
My laptop's DC power jack has a bad contact. And sometimes when the positions is just right, it makes a weird electrical noise which is about as loud as the laptops relatively quiet fans, clearly audible in a quiet room.

How can this weak/bad contact cause audible noise? Is this common in other scenarios?

Another interesting thing is that when I for example move the mouse, the noise changes pitch. I assume this is because of the increased power draw of the processor.

The noise only occurs when the contact isn't solid enough.

It is DC 19V with 4,7A max current and it has a ferrite ring very close to the DC jack.


texts:
I am trying to control a 12V DC fan with PWM using an IRFZ44N MOSFET.
However somehow the fan is not turning on and off when the gate is pulled to either 0V or 5V (on the power supply). And it is definitively not working using the PWM pins on the Arduino Uno.
Next to that a 2/6/12V battery charger is used to power the fan. It is rated at 600mA, while the fan is only 300mA.

The question is: what is broken in my circuit? Maybe the power supply can't handle the PWM action, or my MOSFET broke (I might have over-voltaged it on accident)?

I connected it exactly as in this video.

Thanks for your time in advance!
Bas


texts: Use Atmel-ICE programmer for other JTAG debugging

texts:
I'm new to electronics and come from the software side of things.

Now we are working on a project and we need to program a MCU. Since it's an Atmel MCU we had to get a programmer. It is the Atmel-ICE debugger.

So now I was reading on the internet about debugging embedded devices by JTAG and I was wondering if I could just use the programmer for other JTAG operations since there is a JTAG connector shipped with it?


texts:
I'm playing around with some CTs for measuring appliances.  I got two of these SCT-013-030 units and hooked them up to a breadboard with a 5V supply using this circuit I found on the internet:

I'm using an LM358 instead, but otherwise built that.  I was playing around with some inputs, etc... and taking measurements and then I left it rolling on the oscilloscope as I went back to take some notes.

A few minutes later, I saw this happen:

There's just a kill-a-watt and a surge protector hooked up on the line through the CT.  It's otherwise just hanging out.  Out of nowhere, I've got huge readings.  My input (channel 2) is going from -48mV (as far down as I could see, it got cut off due to range) and up to 130mV (again, slightly cut off, probably a bit higher).  The signal line (channel 1) went from hanging out at slightly under 0 to a solid 4V.

I'm monitoring for the condition to occur again, but it was quite a surprise.


texts: How to get correct response from UPS HID

texts:
I have a UPS HID device and I'm trying to use LibUSB to get data from it. The response expected is in the format below:

(Input_Volt ^ Fault_Volt ^ Output_Volt ^ Input_Curr ^ Freq ^ Batt_Volt (MMM.M ^ NNN.N ^ PPP.P ^ QQQ ^ RR.R ^ SS.S or S.SS ^ Temp ^ Status<cr> ^ TT.T ^8bit <cr>)

Example:
(229.0 000.0 220.0 000 49.9 2.25 33.0 00000000 <cr>)

At the current moment, I'm not able to get a populated response from the device since it's returning a response like this:
(000.0 000.0 000.0 000 00.0 0.00 00.0 00000000)

Curiosity: If I use the software UPSmart I can see that the UPS is working well. If I stop the UPSmart and try to get the response from the device again using my code, the response returned is the last one that was shown in the UPSmart and it does not change anymore.

Here is the code I'm using:

Context mContext = new Context();
int result = LibUsb.init(mContext);
if (result != LibUsb.SUCCESS)
    throw new RuntimeException(String.format("USB error: Unable to initialize LibUSB. Error %d: %s", result, LibUsb.strError(result)));

DeviceHandle mDeviceHandle = LibUsb.openDeviceWithVidPid(mContext, vendorId, productId);
if (mDeviceHandle == null) {
    throw new Exception("USB error: Device not found or is being used by another process");
}

System.out.println(LibUsb.getStringDescriptor(mDeviceHandle, 0x3));

LibUsb.exit(mContext);

Should I send any other command to tell the UPS it should populate the data?


texts: I am writing a code in vhdl for image processing and I learned that in order to blur a picture, that picture must be lowpass filtered. I know about lowpass filters but I dont know how to apply this idea to the image I am trying to blur. How can I do blur a picture in vhdl using this idea?


texts:
I need a simple circuit, one or two components at most, that will only allow a certain range of voltage to pass. I.e. If a voltage is below a min, I do not want it to pass. If it is above a max, I also do not want it to pass.

I only want a voltage to pass if it is within a certain range, not below or above.

I have researched this using Zeners, Op-Amps, etc, and just have not been able to figure it out. The hard part has been having only a range between a min and a max.


texts:
I'm trying to solve this problem:

A GaAs LED is at \$ 300 K \$ when the current density is 1000 \$A/cm^2\$
. The width of the active region is \$ 1 µm \$. Assume that, for that current, we are in the strong injection regime, and
that the bimolecular coefficient is \$10^{-10} cm^3
/s \$.
Calculate the cut-off frequency for that current density.

I know the answer is 12.5 MHz.
I know that the cut-off frequency relates do the carrier's lifetime.
$$f_c=\frac{1}{2 \pi \tau}$$
Right, so now I need to calculate the carrier's lifetime. I know that since this is strong injection we would have:
$$\tau=\frac{1}{B \Delta n_0}$$
where B is the bimolecular coefficient. So now I need to calculate \$ \Delta n_0 \$.
My question now is how can I use the temperature, the current density and the width of the active region to calculate \$ \Delta n_0 \$? I feel that I might need some parameters of GaAs at 300 K, but I'm having trouble understanding what parameters.


texts: Having an issue connecting two 4-bit Synchronous Up Down counters

texts:
That's a Traffic Light circuit I designed on Multisim. I used 2 74LS191 Counters, 2 74LS47 Decoders, 2 Seven Segment Displays, a 555 timer and a J-K flip-flop as you see.

It should count from 29 down to 00 then the lights switch and the same process repeats again.

The problem I am having is that the bottom counter, which is responsible for showing numbers on the left display, goes like this 0 -> 2 -> 1 -> 0 instead of starting from 2 when I run the simulation for the first time, but after it finishes the first cycle it works correctly. I think the problem is either from the connections or Multisim, but I can't really determine the cause. Can you help me, please?


texts: One single fly-back diode or individual diodes for multiple relays?

texts:
Please see my crude drawing:

My question is this. If I was to have multiple relays powered from the same rail, but have each one sinking via whatever to respective MCU pins, could I use option B as the single fly-back diode, or must I have it like option A with a diode for each coil? (Obviously with a diode capable of handling the job.)

Please note, my question is about the flyback diode config. Not about MCU current capability or power supply, etc.


texts: Why NRF24L01+ modules set RPD bit when detecting a signal above -64 dBm on the channel?

texts:
Why the value -64dBm?

Is it because anything above this value and the receiver is unable to decode any valid packet on the channel?

Does this have anything to do with receiver sensitivity?

Can this be used to scan the spectrum for channels with low interference, free from WiFi transmissions?


texts: Would a DPDT switch work to turn either one or both devices in this circuit?

texts:
I'm doing a replication of vehicle hi/low beam switch in my "lab" and I'm not sure what's the right type of switch for it. It has to have a dedicated on/off switch (the one on the bench power supply doesn't count) so that should be a basic SPST on/off switch that makes or breaks the circuit when PSU is on.
However, there are 2 lights (LEDs) here, one hi beam, one low, and low beam needs to be on by default, and high beam additionally turned on when needed. What is the correct type of switch for this?
The pushbutton is there to flash the light #2.


texts: Standards for vehicular lighting connections

texts:
I am a cyclist and electronics hobbyist, so I am designing an electrical system for my bicycles.

THE QUESTION

"What do I need to know (standards, available components, good practices) so that I can design the proper CONNECTIONS in the system, either the cables leaving the circuit boards, or the external cable connections between components?"

I will use one hub generator on each bike. It produces alternated current at nominal 6V / 3W, this is sort of standard.

My plan is to have an "electrical system" on each bike, whose central unit would be a regulator/rectifier/limiter. This regulator would take the power from the dynamo and provide 6V DC to every other pluggable device in the system.

My concern is that I don't know what electrical and mechanical characteristics are commercially available in order to make connections that are:

Weather resistant;
Mechanically resistant to shock and vibration;
Easily pluggable/unpluggable;
Easily serviceable (disassembling for cleaning and/or substitution of modules);
NOT over-engineered...

Hopefully, I will replace what I have now, which by the way works fine, but leaves a WHOLE lot of room for improvement... (image)


texts:
I designed a PCB with the following audio amplifier on it:
https://eu.mouser.com/datasheet/2/302/TFA9896_SDS-1381317.pdf

According to the data sheet, the amplifier is able to deliver 2.1W RMS into an 8 Ohm speaker at a battery voltage of 3.6V.

For testing the amplifier, I used a 3W speaker with 8 Ohm and played 16 bit wave files with a maximum amplitude of less than 1. When I play these files, there is strong clipping. This can be observed also for other speakers.

The audio amplifier boosts the input voltage to 6.1V and is able to provide a peak current of 2.5A. In my tests, I measure a peak current of 0.5A and an average current of 0.25A during playback.

As I'm lacking experience with audio amplifiers, I wonder how to fix this issue. When lowering the maximum amplitude of the wave files to less than 0.5, the clipping vanishes. However, I would like not to sacrifice for volume as the audio amplifier should be able to provide enough power according to the data sheet.


texts:
I want to build an embedded device which is using a USB-C for debugging purposes and USB 2 functionality.
Now I am not sure whether or not I understood the USB-C Standard correctly.

Is it correct, that if I connect the CC1 and CC2 to pin with a pulldown of 5.1 kOHM to GND that other devices detect the debug accessory mode and therefore is it save for a connecting device that none of the 14 pins are used?

Is it still possible to use the D+/D- pins for USB 2 purposes?

The idea is, that I short-circuit the pairs Axx and Bxx and connect SWD-Signals to the Pins A11,A10,A8, A2,A3 and vice versa for B and connect USB 2 to the D+/D- Pins as well.
3.Is there a tool I am able to detect from a computer in which mode a device is?
Thx for your help


texts: Increasing sensitivity of photodiode amplifier

texts:
I have build a 2-stage amplifier circuit for amplifying the current from an InGaAs photodiode. It uses 2 OPA4350 op-amps. The first stage is a TIA with a feedback resistor = 1MΩ. The 2nd stage is a voltage amp with a feedback of 10kΩ.
It works very well with little DC offset and very good sensitivity (it saturates to 2V with a 5mW uncollimated IR laser located 3m away).

However, the device that we are wanting to measure the light output from is VERY weak. We require a 20ms exposure time on our InGaAs camera to see a pixel illumated to ~150ADC counts (I'm trying to find out what this means in terms of incoming photons).
I know the "correct" answer is "Improve the light output of your device". But we have no easy way of achieving this. We're already using the most powerful laser at our disposal and require a very fine linewidth.
I have considered modifying my circuit to create a charge integration amplifier with a capacitor reset switch to mimic the exposure time of the camera.
Are there any other ideas I could consider to sum up the photocurrent before reading out? If I'm not seeing any instantaneous photocurrent on the output of my 1st stage (or even my 2nd stage), is there any point in modifying the circuit?
I'm open to any suggestions :)

EDIT: Based on some of the great responses (special thankyou to @Matt), I'm going to try the following circuit. Ignore the component values. I've just been playing around. Until I know the photocurrent, I'll experiment with the feedback capacitor and reset timing.
For the switch, I'm considering a TS12A4516.
Does anyone see anything blatantly incorrect with this, or have any ideas for improvements.  I'll also pressure my optics colleagues to find a lens solution.
Thank you all.


texts: DC gain of non-inverting integrator / Derivation of DC results from transfer function

texts:
(The pictured circuit contains a serious mistake, see my answer for more detail. I decided to leave the question in its original form for educational purposes, though.)

Setting

The (sub-)circuit in question looks like this:

(Both OP amps can be considered as ideal.)

simulate this circuit – Schematic created using CircuitLab

It's part of a larger question about an Ackerberg-Mossberg biquad (which looks like this) where one is asked to calculate

a) this subcircuits DC voltage gain \$A_{v,DC}=\frac{V_{out}}{V_{in}}\$, and later

b) its transfer function \$A_v(s)=\frac{V_{out}(s)}{V_{in}(s)}\$.

As I like to derive my answers for DC analysis from the transfer function \$A_v(s)\$, I tried the following:

1) Directly determine the transfer function \$A_v(s)\$, which answers b):
$$A_v(s)=\frac{V_{out}(s)}{V_{in}(s)}=\frac{1}{sR_1C_1}$$

It should be the transfer function of a non-inverting integrator amplifier.

2) Compute the DC gain by using \$\lim\limits_{s \rightarrow 0}{A_v(s)} \$. That is
$$A_{v,DC}=\lim\limits_{s \rightarrow 0}{\left(A_v(s)\right)}=\lim\limits_{s \rightarrow 0}{\left(\frac{1}{sR_1C_1}\right)=\infty}$$

[better use step function here]

But here's the thing: the solution of a) simply says that \$A_{v,DC}=-\infty\$ which contradicts my answer.

Questions

So here's my questions for you:

i) Which answer to a) is correct?

ii) If my answer is wrong, one possible explanation would be that I can't simply use the limit for \$s\rightarrow 0\$ because in reality it's defined as \$s:= \sigma + i\omega\$.
This means that I would have to assume \$\sigma=0\$ and do the limit for \$\omega\rightarrow 0\$ which brings me to
$$A_{v,DC}=\lim\limits_{\omega \rightarrow 0}{\left(A_v(s=0+i\omega)\right)}=\lim\limits_{\omega \rightarrow 0}{\left|\frac{1}{(0+i\omega)R_1C_1}\right|}=\lim\limits_{\omega \rightarrow 0}{\left|\frac{-i}{\omega R_1C_1}\right|}=-\infty$$
Would this be a correct derivation?

[wrong! See @Chu's comment]

iii) If the above doesn't work, why is it so? And is there a way to calculate a) from b)?

DC analysis can become very confusing when one has to deal with open loop amplifiers, especially in bigger circuits. So it would be very nice if one can derive the DC analysis results from the laplace domain transfer function.

iv) To go beyond the exercise question: I'm curious about the bode plot, because the single pole at \$s=0\$ (and no zeros) suggests that the magnitude goes from infinity to zero (with -20dB/decade) as the frequency goes upwards but what happens with the phase?


texts: Are the noise floor and signal to noise ratio same things?

texts:
I have a problem in understanding clearly what noise floor is. The term SNR is more clear which is the ratio of the signal to the noise in dB.

In wiki the term noise floor is explained as:

  In signal theory, the noise floor is the measure of the signal created
  from the sum of all the noise sources and unwanted signals within a
  measurement system, where noise is defined as any signal other than
  the one being monitored.

I still don't understand what it means mathematically or graphically. It says " measure of the signal created from the sum of all the noise sources and unwanted signals within a measurement system,.." I don't get what "measure of" means in this context.

How can noise floor be explained in a more clear way?


texts: LTSpice: How to Add Trace of Two Swept Values

texts:
I'm sure there is a really simple explanation for this but I can't seem to figure it out. I am sweeping the series resistance of the source voltage and I am trying to see the transfer function output. When plotting the V(out) and V(in) plots separately, the different plots are shown for increasing values of series resistance. However, when I "add trace" as V(out)/V(in), only one plot appears. How do I get plots of V(out)/V(in) for all the different values of series resistance?

Alternatively, is there a way I can plot V(out)/V(in) directly rather than going into the waveform viewer and using "add trace"?

Any insight on this problem would be greatly appreciated.


texts: According to the Nyquist criterion this system is stable but when I apply an impulse I get an unstable response, why?

texts: I have this open loop transfer function and I have to study the stability of the closed loop transfer function using the Nyquist criterion. What I got is that the characteristic equation 1+GH(s)=0 has two roots inside the Nyquist contour, the GH(s) transfer function has zero poles in the right hand plane and that the number of loops around -1 in the Nyquist Diagram is 2 so according to the Nyquist criterion, Z=N+P in which I get 2=2. So the system is stable, however the response I get to an impulse is this:


texts: Homemade PMOS LDO again, is a few millivolts of oscillation normal?

texts:
After I walked through datasheets of different op-amps it turned out that I can live without the NMOS as a driver for the pass transistor, using TL084 op amp (or its one unit sibling TL081) if the pullup resistor is large enough, e.g. 20k. Now I ran this in a simulator and I am getting a little bit of oscillation (several millivolts at the output, am I treading noise land if battling this?) is this normal or should I resolve this too?

Here is the circuit diagram, respect part numbers as those are exactly what I used. Google will be your friend in finding datasheets as everything is jellybean parts.

simulate this circuit – Schematic created using CircuitLab

This several millivolts oscillation result is taken from when I simulate with 1kHz 3Vp-p sinusoidal biased by 9V or 15V. Does this spell good regulation? The 10 ohm load seems pretty hard to satisfy.


texts:
I sandwiched my pcb artwork onto my pcb using a photoframe  then placed the frame on top of my leds. I exposed it for like 4mins. I was going to expose for 2 but I over ran abit lol. Anyway bits of it didn't even transfer. When it did transfer I could clearly see the traces but it was faint when I developed it. Admittedly I did staple two copies of my artwork together which meant the artwork wasn't pressed flat aginest the pcb . Does that matter?

Have I even brought the right type of pcb, along with some positive developer?


texts: Multiplex dip switch input to microcontroller

texts:
I have 3 DIP switch packages with 8 switches each, and not enough inputs on my microcontroller. This article (you have to download the pdf to see the schematic) gives an example of what I want to do.

In the comments section, many people say the circuit won't work. I disagree; It looks like those commentators missed the fact that one of the lines is drawn as an 8 pin bus, and the fact that unused RA pins will be set as high impedance inputs. Still, I wanted to get a second opinion from the experts here!

Edit: After reading the many good answers to this question it seems my initial impression was wrong.  This circuit will only work for momentary push buttons, not dip switches.


texts: H-Bridge diode makes the motor go faster

texts:
I am making a little robotics project were my robot spins around a shaft. Since it can't spin a full 360º turn I placed some limits in the software but just to be sure I also placed two limit switches to disconnect the motor in case the robot hits them (thus going beyond it's limits).

In case the robot hits the limit switches, the motor will be disconnected and I will have to turn the motor by hand to release the switches and reconnect the motor to the circuit. To avoid this, I planed to place some diodes that will make the motor only turn in one direction (back to it's operational range) in case the switches were triggered.

When I was testing this, I connected the ESC (Electronic Speed Controller - Basically an H-Bridge) in series with the diode (a 30V 5A schottky diode) and the motor (a regular DC brushed motor with no load) to see how it will behave, and the result was really a surprise to me. The motor at first didn't spin and then after some seconds it started to spin faster and faster, so I disconnected it to be safe. The ESC was programmed to spin the motor at a constant speed (25% of the maximum speed) with a 10KHz PWM.

Can anyone guess what's happening? I looks like the diode is charging the motor, but I can't see how.

PS: Don't mind the direction of the diodes in this drawing, I am not sure about the real position of them. In the test I just connected the diode in such a way it will be in series with the motor so I could test it.

simulate this circuit – Schematic created using CircuitLab


texts: Do we want output resistance of a transistor to be high or low

texts: I have a serious doubt about output resistance of transistors. We say that output resistance of a device must be high, for example in BJTs, because it is actually a norton resistance in parallel with the dependent current source of small signal model. But at the same time, we don't want any other device to affect the device we are using in series to it. So, a lower output resistance is required. So, which one of this correct?


texts: Circuit with Zener-Diode not working (simulation do)

texts:
Hello,

I have the circuit shown above. Its made to measure analogue voltages up to 10V and converting currents up to 20mA to a voltage output.
10V or 20mA = ~3.3V output

Now I want to test the voltage measurement functionality:
Vgate = 0V
V_I_IN = 0V to 10V
The Zener Diode has a nominal Vz=3.6V

The output voltage is linear up to 4V Input, if I go higher the output voltage rises slowly.

Voltage measured at Vgate=0V
at J7 = 0V

There are no mistakes in the pcb layout, checked it very often.

Datasheet Zener

What could be the error?
Here is the simulation result:


texts: A USB 3 to M.2 Reference Design Schematic

texts: I am looking to make a small project where I need to implement a USB3 to M.2 SATA circuit for SSD interface. I am pretty confident I can follow a reference schematic and route the board, I have done this type of thing before. But I don't know where to begin in terms of finding the right components for a USB3 to M.2 SATA SSD board. Is there a place where people post open hardware reference designs? My guess is that companies that make such silicon chips that do the actual conversion would have reference documentation, but I, again, not sure where to start. Could someone point me in the right direction?


texts: Discharging capacitor through potentiometer in ADSR circuit

texts:
I'm trying to build a circuit for generating ADSR envelopes for use in an ananlog synthesizer, and a part of the circuit acting in a way I can't understand. Here is the part of the circuit that is giving me the problem (not the entire circuit):

simulate this circuit – Schematic created using CircuitLab

(If this looks like a strange circuit, remember that this is only the part that is not working, stripped to its most simple form.)

The first op amp is outputting around 7 V DC. The gate voltage of the mosfet is 0 V. My problem is this: as I increase the resistance of R3, the voltage across C1 increases (it very quickly approaches 7 V as R3 is increased to some tens of kiloohms), and this only occurs if the mosfet is connected (gate voltage at 0). If I remove the mosfet from my breadboard, then R3 does not affect the voltage over C1, it simply remains discharged as I want it to.

I really have no idea why this is happening. Is there something I don't know?


texts: Connecting AVR running at 3.3V to a 2.8V I2C bus

texts:
I want to connect an AVR (ATmega48PA) to an I2C bus whose pullups are connected to 2.8V which is the operating voltage for other devices on the bus. The AVR is running at 3.3V.

Since SDA and SCL pins are open drain, the AVR, if connected, isn't going to "push" 3.3V on the bus, so other devices on the bus are safe. Also, as per the electrical characteristics section of the datasheet, the threshold for logic high is 0.6*Vcc which comes to 1.98V for when Vcc is 3.3V. The I2C bus voltage is well above this threshold so I guess I can connect the AVR directly to the bus without any level shifting. Is that correct?

Datasheet
Page 383, Table 33-2 : Common DC Characteristics


texts: How do I exchange LCD display with 7-segment LED's?

texts:
I have bought a cheap radio controlled clock, and I want to make a hack that replaces the existing LCD display with 7-segment LED's.
With my voltmeter in AC mode, I can measure voltages(with respect to battery minus) on the connectors to the LCD of 0.4V(presumably off) 1.4-1.6V(presumably on). I do not know the waveform or frequency of this voltage, but I suppose I can measure it, if I find an oscilloscope somewhere.

How do I convert this AC to a logic signal, that can be used to drive the 7-segment?
Is there any standard regarding LCD drive voltages?
Does there exist a single drive chip for this purpose?
Do I need transistors, op-amps or a chip to make enough current?

UPDATE:
There is absolutely no logic in the display itself - it is just a glass plate(with liquid crystal). I can even make the display turn on shortly with dc. All the connector seen on the picture drives the display directly.

Update
(Wikipedia LCD) says:

  Both the liquid crystal material and the alignment layer material
  contain ionic compounds. If an electric field of one particular
  polarity is applied for a long period of time, this ionic material is
  attracted to the surfaces and degrades the device performance. This is
  avoided either by applying an alternating current or by reversing the
  polarity of the electric field as the device is addressed (the
  response of the liquid crystal layer is identical, regardless of the
  polarity of the applied field). Displays for a small number of
  individual digits and/or fixed symbols (as in digital watches and
  pocket calculators) can be implemented with independent electrodes for
  each segment.


texts: I need advise about LIN bus ESD protection. Here a four LIN connectors on board but only one LIN driver (master), is it mean that ESD protective diodes also must be 4? placed close to each connection? And take into account capacitance of these four ESD diodes?


texts: RLC band stop vs. RC low pass filter for switching noise in DC-DC converter

texts:
I'm working with a DC-DC switching IC that has a fixed switching frequency of 10kHz. I'd like to filter out that switching noise. The load is just an instrumentation amplifier, so the peak current will be under 1mA at ±30V.
Given that I know where the majority noise is likely to be on the frequency spectrum, and that I'll be including the usual decoupling capacitors anyway, are there any benefits in adding an RLC or RC filter to the power path? If so, is there a benefit to using one type over the other, assuming that the series resistance I select is roughly the same (say 3Ω) in both cases? For example, I can see that for similar attenuation at the same fc the capacitor is smaller for the RLC filter, so that'd be a potential cost saving if it weren't for the added inductor.


texts: CMOS transistors for educational purposes

texts:
I am currently teaching my daughters Digital Electronics, ages 9 and 12. In doing so, I wanted to introduce them to CMOS logic, since I feel that a hands-on approach is always better than just doing theory.

I purchased a few NMOS and PMOS through-hole type transistors intending to demonstrate basic logic gates such as NOT (1 NMOS, 1 PMOS), NOR and NAND (2 NMOS and 2 PMOS). That worked great, and they could reason about why the gate worked the way it does.

Next up is XOR and XNOR, but it stumbled me a bit. I know how to make a circuit using nine transistors, but looking online I've seen 6-transistor and even 3-transistor solutions. However, these assume you can change width and length, so these are solutions meant for ASIC designs, not for through-hole components.

So, my question is - is there a way to demonstrate XOR/XNOR gate logic with off-the-shelf CMOS/PMOS transistors using only a few transistors? Six transistors would be all right, eight slightly worse yet doable.

Perhaps I should just skip XOR/XNOR and move on to latches and flip-flops?


texts: Confusion about a basic BJT current mirror

texts:
Below is part of a BJT current mirror:

I marked the specific nodes of the reference transistor on the left as x, y and z.

Many texts claim the following(I tried to summarize):

  Since the collector of this transistor is tied to the base of it(x
  is directly wired to y), so we can say that from collector to the
  emitter we basically have one diode drop. The transistor is operating
  as a diode.

What they say "one diode drop" must be the potential difference between x and z.(?)

So if we write the potential difference between x and z:

Vxz = Vxy + Vyz

I guess they are assuming Vxy = 0, since there is no voltage drop across a single wire right? Is that the reason they conclude Vxz is "one diode drop"?

But if they assume this and if it correct, it leads me to a confusion. Let's focus on this section of transistor:

If we think with KVL, I would say Vxb = Vxy. So that would lead me to think Vxb = 0 because we said Vxy = 0.

Bu we also know that current flows both from x to b; and also from x to y then they both flow all the way down to z.

So at the beginning accepting the transistor in a diode type of connection led me to this paradoxical confusion.

Where am I making a logical mistake here?

Edit:

I'm still trying to understand but the user "horta" could express my confusion the best as follows:

  "Since we treat wires as superconductors in schematics, there's
  current flow from X to Y because the resistance is 0. You can treat
  the internal collector-base junction as having some resistance and
  therefore 0 current. Ohms law states that V=IR. Without voltage how
  can you have current? If R=0 because 0/0 is undefined."

1-) Everybody agreed Vxy = Vxb.

2-) And everybody agreed Vxy = 0 because the wire doesn't drop voltage from x to y.

3-) But since there is resistance across x and b, Vxb is actually non-zero which means Vxb = non-zero.

4-) Now go back to the first assumption and see zero = non-zero.

What is going on?


texts: Why don't USB-C hubs have a full USB-C port with PD and data?

texts: Every USB-C hub I have seen only comes with a USB-C port that either only supports PD or only supports data.  My laptop has USB-C ports which support both PD and data (for example, when sending a video output upstream but charging downstream at the same time).  Ideally, I'd like a hub with a USB-C port that has this same functionality, but I can only find ones that support one or the other - never both.  Is this a design limitation with the USB-C controllers, or something else?  Is this a function only offered by Thunderbolt?


texts:
I built BOOST CONVERTER,
I sample the output voltage with A/D and control it
using RASPBERRY Pi3, I set the switching frequency of the BOOST CONVERTER 70KHz,
and the frequency of the MCP3008 1.35MHz,
is that right? and what is the connection between the switch frequency of the converter
and the frequency of the A/D?


texts: I have been reading datasheet over datasheet and seems to find nothing about this. I know I can use SPI_A for both bootloading and programming the atmega32m1. But can I use UART? And should I go with atmega32m1 at all or just replace it with other micro-controller. I am using this to design an ESC and form factor is important.


texts: How to derive this formula from this schematic?

texts:
This is the voltage multiplier from the paper ,it said the rectiﬁed output voltage is given by

\$ V_{out_i}\$= \$ V_{out_{i-1}}\$ +\$2(V_A-V_{ON})\$,\$V_A\$ is the AC voltage amplitude at the input;\$V_{ON}\$ is the voltage drop by the native NMOS transistor.

I don't know how does the author derive this formula from the schematic,can anyone teach me how to derive this?Please explain more specific,for example,when NMOS turn on/off,the bottom side voltage of first \$C_M\$ is ?V,and why does \$(V_A-V_{ON})\$,not \$(V_A+V_{ON})\$


texts: Is it possible to combine two CFU455IT +/-2kHz (4kHz) ceramic filters to get a +/-1.25kHz bandwith (2.5kHz) filter?

texts:
Can I put two of these cheap (less than 3USD) and common CFU455IT +/-2kHz (4kHz bandwith -6dB ) ceramic filters in series to get a lower bandwidth good for SSB TX? If I'm correct I will get -12dB at +/-2kHz so the bandwidth will be reduced a bit, I can trim the rest by adding a trimmer in parallel to the filters and playing with the loading resistor. What about CFU455HT? They are even more easy to get and cost 1.25USD. It sure beats paying 50USD for a factory made one and I have only so much crystals to put in filters.
When making an SSB superhet RX are lightly loaded (100k ohms) LC resonant circuits and RC lowpass audio filters good on their own or do I really need that filter?
73 de SO9LEK


texts: Cutoff frequency on a CAN bus communication line

texts:
I want to determinate the cutoff frequency of a low-pass filter on CAN bus communication line. I found the following values on the Internet:

R = 100 ohm
C = 560 pF

When I calculate the cutoff frequency of this filter I find out that the  frequency is 2.8 MHz.

In this example I have no idea of the bitrate on the bus. In my application I will use a bitrate of 500 kbits/s.

Now can anybody help me with determining the needed cutoff frequency on my application and explain me why I should take this frequency?

I have no experience at all with this.

SETUP:

As the CAN transceiver I use Microchips MCP2551.


texts: Significant error with unity-gain feedback op-amp

texts:
I used this OP97 op-amp to make a simple unity-gain feedback circuit. I would expect the output in this case to follow the input with very little error, however the output is actually measured at \$ 2.7 \text{ V}\$ rather than \$ \approx 3.1 \text{ V}\$ as expected.
This seems like a fairly large error for this buffer. I checked the data sheet and it appears that I'm operating the device well-within the allowable supply range, so I'm not sure what the error may be.

simulate this circuit – Schematic created using CircuitLab


texts: How to filter out the mains power supply spikes?

texts:
I'm purposely dropping AC from its normal levels (230VAC @50Hz) just to analyse the behaviour of a DC motor drive board that I have.

When the AC mains voltage falls below 180V, the 7 segment display of my board goes off. The circuit derives the 5V for the MCU and 12V for the display driver ULN2003 from a 12V step down transformer, a bridge rectifier and a 7805 regulator circuit. ULN's 12V supply is given from the input pin of 7805.

I'm curious about the display turning off problem when the AC voltage drops. As the display needs 12V only, can't it still find the power from the 180V AC? What would be the better power supply solution for such a noisy mains?


texts:
I'm currently playing around with some load cells in a wheatstone bridge - each cell has 3 wires (sub-1mm thickness). I want to mount these cells onto 2 separate pieces that can be spaced apart to allow them to fit under different sized objects more easily - so I want to connect the 6 wires on one piece over to the other, 30-60cm away.

I'm looking for a 'standard' connector of some kind that can carry 6 wires to connect one piece to the other, so I can mount a socket onto each piece. I'd like to just buy the wires with connectors already attached, and ideally the sockets will come in a form where I can easily attach the wires to them without having to have a custom board made up or require an expensive crimp tool (I'm not sure the load cell wires would be suitable for crimping anyway).

Any suggestions on common connector format that could work here?


texts: Hacking laptop power button: Turn on laptop when AC's back

texts:
I'm using one of my old laptops as a server. I'm running the laptop without battery in case of a need for a hard reset. When I need a hard reset, I want to be able make this happen with a toggle of AC power. The problem is, when AC power lost and come back, the laptop can not be powered on automatically. Unlike desktop computers' BIOS, most laptop's BIOS including mine does not have such power settings and no "wake on lan" option.

So I decided to hack the power button. If I touch a 1 uF capacitor by parallel, laptop powers on. This is good. If I solder this capacitor in the same place, the laptop is not getting up when AC power come back.

Why would it happen?

Edit

The laptop expects power button released in the firs place, and then pressed for a short time. What I did causes "pressing button as soon as the AC power comes" effect. That was why battery led is flashing when I solder the capacitor to the pins of the power switch.

Edit2

Answer is added: https://electronics.stackexchange.com/a/145588/20285


texts: Difference between these counters 74LS196 and 74LS197

texts:
Components data sheet can be confusing sometimes

Can anyone explain to me the difference between these counters 74LS196 and 74LS197 ?
can they replace each other? can the 74LS197 perform better in the place of 74LS196 in case if they do replace each other?
Other thing, I found 74S196 !! so is the LS is different than S version
- all these components are discontinued long ago, so any specific replacement with the same pin out ?

thanks in advance


texts: Effect of emitter capacitor in common-emitter amplifier

texts:
This question is about the common emitter circuit, shown below, concerning the influence that the emitter capacitor (\$C_E\$) has on the gain of the amplifier.

In the book "Transistor Circuit Techniques", by G. J. Ritchie, the author says that the common emitter has the following critical frequencies, due to the influence of capacitor \$C_E\$:

\$f_0=\dfrac{1}{2\pi C_E(r_e\parallel R_E)}\$ is the frequency at
which the voltage gain is 0.707 (\$\sqrt{2}/2\$) times its mid-band
level,
\$f_1=\dfrac{1}{2\pi C_ER_E}\$ is the frequency at which the voltage
gain is 1.414 (\$\sqrt{2}\$) times the DC voltage gain.

He also says that the voltage gain of the emitter follower can be expressed in the following form, which he calls "standard form":

\$ A_v = A_{dc} \dfrac{ 1 + jf/f_1 }{ 1 + jf/f_0 } \$, where \$A_{dc}\$ is the DC voltage gain (that is, the gain for frequencies where \$C_E\$ can be approximated as an open circuit).

I'm trying to understand the author's statements that I outlined above, and would like some insight. Below are my attempts.

First, I drew the AC model:

(In the AC model, since I care about the effect of \$C_E\$'s reactance on the gain, I don't neglect it. However, I assume that the input capacitor \$C_C\$ is a short-circuit for all the frequencies of interest.)

Then, I calculated the gain of the amplifier. Here is what I did:

Calculating \$v_{in}\$ in terms of \$i_b\$:

\$v_{in} = i_b\left (r_\pi + (\beta+1)\left (R_E\parallel \dfrac{1}{j\omega C_E}\right )\right )\$

Calculating \$v_{out}\$ in terms of \$i_b\$:

\$v_{out}=-i_cR_C=-\beta i_bR_C\$

Calculating the gain (\$\dfrac{v_{out}}{v_{in}}\$):

\$A_v=\dfrac{-\beta R_C}{r_\pi + (\beta+1)\left (R_E\parallel \dfrac{1}{j\omega C_E}\right )}=\dfrac{-\beta R_C}{r_\pi + (\beta+1)\dfrac{R_E}{j\omega C_ER_E+1}}\$

Now, in order to express that in the "standard form" given by the book's author, I will find \$A_{dc}\$ (the DC gain). The DC gain can be found by making \$\omega=0\$ in the expression for \$A_v\$:

\$A_{dc}=\dfrac{-\beta R_C}{r_\pi + (\beta+1)R_E}\$

Now, \$A_v\$ can be expressed in tems of \$A_{dc}\$:

\$A_v=A_{dc}\dfrac{j\omega C_ER_E+1}{1+\dfrac{j\omega C_ER_Er_\pi}{r_\pi+(\beta+1)R_E}}\$

\$A_v=A_{dc}\dfrac{1+j\omega C_ER_E}{1+\dfrac{j\omega C_ER_Er_e}{r_e+R_E}}=A_{dc}\dfrac{1+j\omega C_ER_E}{1+j\omega C_E(R_E\parallel r_e)}\$

Comparing this with the standard form, I can see that \$f_1=\dfrac{1}{2\pi C_ER_E}\$ and \$f_0=\dfrac{1}{2\pi C_ER_E\parallel r_e}\$, just as stated by the author.

Now, I can also calculate these frequencies directly from their definition. For example, if calculate \$\omega_1\$  (the angular frequency corresponding to frequency \$f_1\$) by making \$\left | \dfrac{A_v}{A_{dc}} \right | = \sqrt{2}\$, I get:

\$\left | \dfrac{1+j\omega_1 C_ER_E}{1+j\omega_1 C_E(R_E\parallel r_e)} \right |=\sqrt{2}\$

Solving the above for \$\omega_1\$, I get:

\$\dfrac{1+\omega_1^2 (C_ER_E)^2}{1+\omega_1^2 C_E(R_E\parallel r_e)^2}=2\$

\$1+\omega_1^2 (C_ER_E)^2=2+2\omega_1^2 C_E(R_E\parallel r_e)^2\$

\$\omega_1=\dfrac{1}{C_E\sqrt{R_E^2-2(R_E\parallel r_e)^2}}\$

That gives me an \$f_1\$ of: \$f_1=\dfrac{\omega_1}{2\pi}=\dfrac{1}{2\pi C_E\sqrt{R_E^2-2(R_E\parallel r_e)^2}}\$

This is close to the result stated by the author. If I neglect \$r_e\$ as being very small compared to \$R_E\$, I get the exact same result stated by the author (\$f_1=\dfrac{1}{2\pi C_ER_E}\$).

Is my reasoning correct?


texts: Level shifting with a voltage reference of 1.6V

texts:
I am trying to build a level shifting circuit for my project in order to make sure that the input will be appropriate for a 0-3.3V ADC.
I am using two 9V batteries connected in series so my thought is that I have to shift the incoming signal by around 1.6V in order to be in range for ADC.
I have tried two ways to create a voltage reference using 4 1n5818 diodes in series that gave me a reference of around 1.8V and a LM317l voltage regulator giving me around 1.66V.
The problem in my schematic is that the when I connect the reference circuitry to the opamp, it doesn't work as expected. I am not sure what I am doing wrong here.


texts: Recommendation for si4734 external clock source

texts:
The si4734/4735 FM receiver has two options for clock input, one is to use the typical crystal oscillator (a crystal + pair of capacitors to ground), attached to the DCLK+RCLK pins, the other is to feed a "finished" clock source to just the RCLK pin. The first is the most common design, all the examples and app notes I saw use it. But this limits you to use its analog audio outputs, since for digital audio output the DCKL pin is needed.

Has anyone tried the second option? Any recommendations for a good (small+cheap) clock source circuit?

http://www.b-kainka.de/SI4735Srds1.html

http://www.elexs.de/SI4735g.html

http://www.silabs.com/pages/DownloadDoc.aspx?FILEURL=Support%20Documents/TechnicalDocs/Si4734-35-C40.pdf

http://www.silabs.com/products/audiovideo/amfmreceivers/Pages/Si473435.aspx


texts:
A simple current source using a bipolar transistor uses the voltage over an emitter resistor as feedback of the current. The current is given by the base voltage, the \$U_{eb}\$ of the transistor, which is about 0.7V and the voltage over the emitter resistor. The interesting important constant value is \$U_{eb}\$.

Valid XHTML http://files.hottis.de/Stromquelle.JPG.

I'm wondering whether it would be possible to use an IGBT instead of an regular bipolar transistor. Has an IGBT a constant \$U_{eg}\$ as the regular bipolar transistor has a constant \$U_{eb}\$?


texts: Why monitoring power and energy in energy usage meters?

texts:
This time my question about the how power companies monitor usage.
We get electric usage bill in [Kilo watt hour]/Energy.
What should be looked up on for monitoring the usage the instantaneous energy or power?
Or Both?

  I trust it is the second one and why is it necessary to monitor both
  power and energy?

Power is the d/dt of energy.So what change does it make?

And how different will be the result getting from the second method?


texts: Measuring precisely the efficiency of a power converter

texts:
I am trying to measure the efficiency of a DC/DC boost-converter in several operating points as precisely as possible. Right now I am measuring my input-voltage and output-voltage with a multimeter, and the input-current and output-current over a shunt-resistor with a multimeter as well. I think the four multimeters are pretty high quality (Flukes). I then calculate the input power and output power. Unfortunately it seems that my measurements are not precise enough, especially through the multiplication factors of the shunt and the multiplication of voltage and current, the resulting power seem to be off by a couple of percent (determined by repeated measurements of the same operating point).

Is there a better and more precise way to calculate the efficiency of my converter. I would obviously prefer a cheap solution, but if there is no way around it, I could also convince my boss to invest some money.


texts:
I am looking for more info on AI hardware architectures, but I am a bit confused. Here are my questions:

Does it all come down to MACs(Multiply And Accumulate) units?
Do MACs usually integrate into ALU like this:

or the ALU in this case IS MAC like shown here

In case anyone is interested I got this from MIT ISCA 2017 (page 124 and down)presentation.

Thanks!


texts:
I apologise in advance if this is the wrong forum, or I'm not providing enough details.

I'm building a thermostat zone controller on a raspberry pi and I've encountered an issue with the relays in my Nest thermostats - mainly that they are 240v AC relays, which I would like to detect the state of using the GPIO on the raspberry pi (which are DC voltage at either 3.3 or 5v). So - I want to read whether the relay is open or closed (calling for heat or not). The details of the relays are listed as: "They are designed to work with wires with an AC voltage measuring 100-240V at 50-60Hz with a max current rating of 3A or with low voltage (dry contact) systems."

The Nest "Homelink"'s relays are a bit of a black box in that I don't know what specific component they actually are, but if I assume that they are a SSR's, then from what I understand the relay will turn on with dc current across it, but will not be able to turn itself off.

Given this, is it possible to trigger the relay's normal operation by some other method, such as cycling the GPIO on and off, so that there is no current across the relay, or even simulating an AC current via setting analog voltage levels (and swapping the gnd and positive sides at the appropriate time).


texts: Explanation for design choices for snubber / debouncing circuit

texts:
I am looking at a 20 year-old, heavily corroded circuit of a push-button handheld control for a DC motor that I intend to "rebuild".

It consists of two micro switches which are connected to (fairly large) 12Vdc relays that allow for the reversal of the direction for the motor. It is connected to the relay via cable with a length of a few meters.

In parallel to each micro switch two components are connected:

a HEL-7D560K varistor
and a .1J100 capacitor

Can somebody explain the design rationale to me?

Is this a debouncing circuit?
Or a snubber circuit? If so, why is there no resistance as part of the snubber?
Is the varistor primarily intended to protect the capacitor or the micro-switch contacts? Is it a "safety" feature or something that comes into play in normal operation? If it is the latter, will this not degrade the varistor?
Is it possible to say what type of capacitor this is?
If this circuit was designed today, would the same components be used?

Edit 1:

OK, after some further research it seems the ".1J100" capacitor marking signifies a 100nF 100V capacitor... Which would suggest the MOV with a maximum clamping voltage of 110V could be intended to protect the capacitor.


texts: PCB Raspberry Compute Module 4 Carrier Design

texts:
I'm working on a PCB Carrier Design for Raspberry Compute Module 4, I have and question for PSU module. I want to supply it with +5V, 3A, and use the same USB-C Connector to Data Transfer to eMMC for flashing, How I should configure USB C connector? What I should to do with the CC connections?
Thank you so much.


texts: Designing an analog circuit that Fourier Transforms or Laplace Transforms an input signal

texts:
This is currently my pet project but I am a bit stuck on some problems.

First I'll go over my idea for the Fourier Transform:
The Fourier Transform is defined as

\$F(\omega)=\int^{\infty}_{-\infty}d\omega\ e^{i\omega x}f(x)\$

As it is difficult to make a complex exponential signal, I decided to replace the complex exponential via Euler's equation:

\$ e^{i\omega x}=\cos(\omega x)+i\sin(\omega x)\$

The design goes as follows:

I will have two voltage sources (each being a sine and cosine signal respectively) and a third voltage source as the signal I want to transform. I split the third signal in two, and I take the log of each of the four signals but putting them into a log amplifier. From there I add one of the split signals to the sine signal, and the other to a cosine signal. From there I send the two remaining signals into a exponentiation circuit and add the two (thus multiplying the complex exponential and the signal of interest. Then I send it into yet another op amp to integrate it, thus completing my Fourier Transform Circuit.

Well not quite. There are two issues with this (hopefully my above explanation makes sense). The first is that, although I have a cosine and a sine to replace my complex exponential function, I still have to deal with the fact that my sine function should be multiplied by \$i\$ in order for it to be accurate.

The second issue is that, even if I do figure out the first, I am only transforming my input signal under one frequency value. How would I do it for a spectrum of frequencies? In other words, is there a circuit that allows me to continuously change the frequency of a signal?

Now I will go over my Laplace Transform idea:

This is similar to the Fourier Transform, only you integrate half of the real line and you integrate your signal with respect to an exponential decaying function.

\$F(s)=\int^{\infty}_{0}e^{-st}f(t)dt\$

This is all good as I can just have a charged RC circuit and multiply the signal of interest and the RC circuit signal via the same method described above (through logarithmic addition and exponentiation via op amps).

My only problem with this however, is that again, I am only transforming under one S value (under one \$\frac{1}{RC}\$ value). Is there a way to continuously change the capacitance or resistance values that is not mechanical? I am afraid that sticking a potentiometer and changing it mechanically would be unreliable and unreasonable.

Or maybe I am going about this completely the wrong way? What do you guys think?

Note that I am doing this because I know digital solutions exist such as the FFT via an arduino board or something. I would like to do this using analog circuits.


texts: How are trace impedances summed together for a single trace?

texts:
I have been asked to calculate the trace impedance of some routing, I know that impedance is dependent on the Er, trace thickness, trace width and distance from a plane. But the trace changes width as it is routed. And the two different impedance solvers have provided 2 different answers.
In Altium I have impedances of 34.98633726, 32.81547534 and 28.78596208 for traces of 0.305, 0.33 and 0.381mm. But The Saturn PCB Toolkit shows 45.2196, 43.2286 and 39.6915 respectively!

How do I work out the overall impedance of this trace?
Which is the better result?

TraceHeight is 0.05mm
TraceToPlaneDistance is 0.142mm
Er is 4.2
TraceWidths are 0.305mm, 0.33mm and 0.381mm along a single trace (the default should be 0.381mm but there are fine pitch devices nearby and a reduction is required to get the trace into the pad).


texts: How can i get a second PMW signal that ranges from -7V to 0V for this H bridge circuit?

texts:
This is the circuit i built.

The data sheet for U1 and U2: https://www.vishay.com/docs/83666/sfh610a.pdf
Currently when i run the circuit and place the curser on the right side of V1 this is the result i'm getting however i need a second PMW signal that ranges from -7V to 0V.


texts: Which wire should I use as dummy load for this specific PSU

texts:
I'd like to make lab power supply out of my old ATX Power supply. I am beginner in electrical engineering and this project seems pretty straightforward. I've checked many tutorials about it and creators of these instructed, that there should be resistor connected to 5V or 12V wire depending on max output current that they can provide.

Here comes my questions:
Should I put dummy load on 5V or 12V?
Is 24ohm 5W resistor fine for connection?

Thanks in advance :)


texts: Atollic's TrueSTUDIO IDE / SDK displays unbelievable variable values

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While debugging with Atollic's TrueSTUDIO IDE / SDK, variables are reported to contain unbelievable values.  But, if the code is left to run, the code behaves as if the variable values are correct.

Why?

Up until now, I have been using TrueSTUDIO to debug my own code which is called from main().  Up until now the variables in my code have contained the expected values.  Recently, I started to integrate my code with existing USB CDC code.  It is in this new code the values, when inspected using TrueSTUDIO, contain unbelievable values.  (To be clear, during the same debugging session, TrueSTUDIO reports variables in my code with expected values.  However, TrueSTUDIO reports variables in the USB CDC code with unbelievable values.)

If this is not confusing enough.  I switched from using TrueSTUDIO to STMStudio (which is a run-time variables monitoring and visualization tool for STM32 microcontrollers). Now when I inspect the variable in question, their values are as expected.

How can TrueSTUDIO fail & STMStudio work?

Is there a TrueSTUDIO setting I have missed?

-thanks


texts: Is it possible to communicate single SPI slave with Two SPI masters

texts:
I am using two STM8 micro-controllers as SPI masters. Master-1 is configured in full duplex mode. And the Master-2 is configured in Receive-only mode. The CS, MISO, MOSI and SCLK lines of Master-1 are connected to the Slave. The CS, MISO and SCLK lines of Master-2 are connected to the Slave. When Master-1 requests data from the slave. Master-1 and Master-2 should receive the data from slave at the same time. And the data should be same. I configured two masters with same baudrate,CPOL and CPHA.

When I am communicating with single master, I could receive the data correctly from the slave. But When I involve the second master in the communication the received data of both master is corrupted. And in the oscilloscope, I could see the SCLK variations on the slave.

What are the things I need to consider while communicating a slave with two masters at the same time.


texts: Safety considerations when using LED and a comparator

texts: I want to make a simple circuit, it uses two comparators to drive two LEDs, it should turn the LED (green) if the voltage is higher than let's say +2.5V. If is lower then turn the first one off and on a second led (red). But here is the catch, it should be able to accept any voltages in the input signal between let's say +9v to -9v. How to achieve this in order to avoid blown up any component?.


texts:
I recently came across a great project here to build a 4.3 GHz radar ground detection unit for an aircraft.  Interestingly, it uses a very complex looking microstrip matching layout:

What is a common software to use for the design and/or analysis of these types of microstrip layouts that become very relevant at higher frequencies?  I'm trying to locate not just the software that allows for simple things like square pads, but for odd shapes like these.


texts: How to look a 230V ,50 Hz AC power supply via oscilloscope from the switchboard?

texts: I am from India. My household supply is 230V, 50 Hz. Now I want to observe the AC supply from the switch board using oscilloscope.Is it ok ? How to do it?(I mean just a resistor attenuator is sufficient?)What  precautions I need to follow? Does it really look like a sine wave?


texts: PFC - High Frequency Input Capacitor Formula

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I do not understand exactly how the below formula has been found. The formula allows to calcul the high frequency input capacitor (Cin) of a PFC boost converter working in CCM :

I particularly do not understand the factor $$2\pi$$
The formula is coming from here : https://www.infineon.com/dgdl/an-1166.pdf?fileId=5546d462533600a40153559aabdf1128

Thank you very much and have a nice day.


texts:
From my experience all chargers for Li-Ion batteries notably heat up when charging the battery.

Why does that happen? Is the charger acting as a not that efficient power supply or is there any process inside it that is specific to charging that leads to such heating up?


texts: I found this transformer and I am not sure if it is working. I am confused with the multimeter readings. For example: when I am using the buzzer option to check the connectivity it buzzes when I connect any of the 3 top ones (16ohms and 32ohms), but when I try to see the connection between the 665ohms it doesn't buzz, but it does show ohms when I use the 2K ohms option. Is this how it's supposed to work?


texts: What is the advantages, and disadvantages of using neodymium magnets instead of ferrite cores in transformers?  How would the magnetic flux density vary of such a transformer utilizing a neodymium core?


texts: Solder mask resist on extra large through hole pads

texts:
I'm adding extra copper area for more thermal heat on through hole components pads. I now wonder if it's okey to have the solder resist overlapping the edge of this extra large copper area and what the pro and con is?

Best regards


texts: Voltage phasor problem in textbook wrong?

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An example in my textbook gives this problem:

Find the phasor representation of vo = -5cos(2000πt+25°)

Answer: 5<-65°

Shouldn't it be 5<-155°? You subtract/add 180° to get the negative of cosine, not 90.


texts: Current control circuit doesn't work in practice

texts:
A control circuit works in simulation, but don't in real. What is my mistake?

Current through R5 or Mosfet proportional with V1 voltage in linear region. But in practice even when V1=0, the current through R5 is more than 1A !!. Power supply limit the current consumption and the mosfet very hot.

BestRegards

EDIT

I changed the circuit after comments.

This works similar to simulations. But MOSFET very hot even 0.5A through R5.   I can't give exact temperature degree. But it was very hot.
Is this circuit structure ideal? Should I continue here?
I can connect heatsink if this circuit is best.


texts: Suggested exercises for learning with Arduino

texts:
I just got an arduino and have been working through some of the exercises in the tutorials, making good progress.

When I'm learning a new programming language or tool, I usually work through a few steps:

do the tutorials,
modify the tutorial programs, get them to do new stuff, and
solve a problem not covered in the how-to to make myself figure out how to do stuff.

With Arduino, I have a bit of a chicken-and-egg problem. I don't have a good enough idea what I can do with it to come up with interesting problems to solve.

What are some good problems/exercises I can tackle as a beginner to help myself learn more about what Arduino can do and how to do it?

Problem statements only, please. Any instructions for solving them would defeat the purpose (though, it might make sense to point out what hardware is required.)


texts: What is the principle of active voltage balancing/equalizing device?

texts:
I am wondering about active voltage sharing devices. Their purpose is to equally divide voltages on slightly unequal super-capacitors. I found some papers like this, but it is too scientific.

I want to understand the details of how the equalization is happening and why?


texts:
This is a short circuit and overload protector for 220V 50hz.
 Does TRIAC also work on 1MHz sine wave?