texts: PIC12C672 Replacing Upgrading to PIC12F683 RT809F PROGRAMMER

texts:
I'm new to the microchip PIC world but not to electronics. I've been learning chip level PC and laptop mother board repair.
 I have a smart battery charger that uses a PIC12C672 that was destroyed along with a Schottky diode and a MOSFET. I want to replace the PIC12C672 and program it using a file dump from another good working PIC controlled battery charger that I have that is of the same model. I have been made aware that there is a new design PIC, the PIC12F683 and some have said to use the PIC12F675.
 My question is can I take the dump file from the PIC12C672 and write it to either of the other upgraded PIC's ? Will this work without having to modifying the code? Should I just buy another PIC12C672 on Ebay and call it a day. Also I own an RT809F programmer, will this do the job?
Thanks for any help with this.


texts: How to correctly set logical high level on a PS/2 port?

texts:
I'm trying to make a keyboard emulator on ATmega16A. I'm currently implementing logical low as output-zero, and, since the host(?) is supposed to pull up the line, I send logical high state as input mode of my pins. This lets me easily check that inhibit condition hasn't happened while I'm transmitting data, in addition to outputting "1".

But the problem is that in this mode, the time to raise the voltage to 95% VCC appears to be about 25 μs, which is quarter of the maximum allowed clock period (minimum frequency is 10 kHz). So I've now tried to actively drive the pin to VCC, and only then switch it to input mode to check for inhibit condition.

Is this kludge of actively driving the bus high actually legal from the protocol POV? I'm following this document and have failed to find how exactly one should output logical high level.

Should I instead use a lower-resistance pull-up resistor on the keyboard side and leave the pin in input state when trying to output logical high value?


texts:
How does one deal with a situation where a trace has particular clearance spec to other nets, but that clearance spec is not respected by the pads on a component that the net attaches to?
A simple example is attaching a chassis ground line, which can see high voltages during an ESD event, to a high-value bleed-off resistor or a bypass cap attached to ground.  The pads underneath the component are much closer together than the minimum spacing, unless I use a very large footprint part.  Is there a better way?  Or am I overthinking this?


texts:
I am designing the PCB layout but some number of components forming the group.
I can't able to use this component. I am not able to pick a single component.
I have attached the problem image below.
Anybody give me the solution for this problem...?


texts: I'm trying to use 3v LEDs in a 12V circuit, in my car

texts:
I'm trying to make a circuit that will run 1-3 LED in a parallel, powered by a 12V power source. I used a voltage divider calculator and it said to use a 100ohm and 33ohm resistor. when I wire them in correctly, the 100ohm resistor overheats and eventually fails. How would I change this circuit to keep this resistor from overheating??
Both resistors are 1/2 Watt.
LEDs are 3.6v max.


texts: Is it possible to make a non-inverting amplifier with positive feedback?

texts:
The 'classic' non-inverting amplifier configuration uses negative feedback. What happens when the + and - terminals are switched? Based on my pencil-and-paper analysis and a Circuitlab simulation, it seems that the result is the same. Is this correct? Can we make a non-inverting amplifier with positive feedback?

Derivation for the positive feedback non-inverting amplifier: I assume that input impedance is infinite, output impedance is zero, and the output voltage is given by

$$ V_{out} = A(V^{+} - V^{-}) $$

Now using the voltage divider equation,

$$ V^{+} = V_{out} \frac{R_b}{R_a+R_b} $$

and for the negative terminal, we have

$$ V^{-} = V_{in} $$

Substituting into the equation for the output voltage,

$$ V_{out} = A(V^{+} - V^{-}) = AV_{out} \frac{R_b}{R_a + R_b} - AV_{in} $$

$$ V_{out}(1 - A \frac{R_b}{R_a + R_b}) = -AV_{in} $$

$$ V_{out} =  \frac{-AV_{in}}{1 - A \frac{R_b}{R_a + R_b}}$$

If the input frequency is relatively low, and both resistors are of a similar order of magnitude, then

$$ A \frac{R_b}{R_a + R_b} >> 1$$

$$ V_{out} \approx \frac{-AV_{in}}{ - A \frac{R_b}{R_a + R_b}} =
V_{in} \frac{Ra + R_b}{R_b} $$

Which is the formula commonly given for the output of the classic non-inverting amplifier. So is there any difference between these two circuits? If so, where does my analysis fail? What is a more accurate way of analyzing the positive feedback circuit presented below?

EDIT: As suggested by Jasen, the positive feedback circuit I posted is a Schmitt Trigger. The Wikipedia article on Schmitt Triggers explains it fairly well. It turns out that they key to analyzing it is to solve for the voltages at the input terminals and then treat the Op-Amp as a comparator. That is, find equations for V+ and V-, and then ask the question "When does V+ > V- hold?"


texts: Starter circuit for solar module driven pump motor

texts:
I have a 24 V 100 W solar panel and a 24 V DC 50 W pump, which has a resistance of 2 Ω while at 0 rpm. The solar panel is directly connected to the pump motor.

The problem is: While the solar panel can drive the motor when it is running, it mostly fails to provide the break-away current the pump requires, so its motor more often than not fails to start turning.

Therefore I thought of a starter circuit, which stores charge in large caps and and fires (drives the pump) as soon as the voltage over the caps has reached a certain limit. Then the caps would provide more current and help starting the motor.
When the sun is blocked by clouds etc., the pump stops and the circuit should "reset", so that the caps can be charged again.

I thought of triggering a thyristor at a certain voltage, but I fear it would only reset back to non-conduction at night, since the solar panel will provide some current even in low-sun conditions, but not enough to keep the pump running.

So, I think I need kind of a custom starter circuit that "fires" when a certain voltage has accumulated across some caps, and stops conducting when the current falls under a certain limit afterwards, so that the caps can be charged again.

Starting voltage and stopping current limits would need to be adjustable, because I have no means to really measure the minimum voltage/current behavior of the pump.

How do I get a solar powered DC pump motor to start reliably?


texts:
The output impedance (\$R_{out}\$) of this circuit is \$R_{S3}\$?

New circuit:


texts: Effect of 2-terminal and 3-terminal Voltmeters and Arduino Voltage Sensing on Circuit

texts:
I am trying to build a board to sense circuit voltage relative to ground at different points on a breadboard. I would want the board to work regardless of configuration of the circuit. The only exception would be the location of GND, which would be the same always.

There are two ways I was thinking about doing this:

Voltmeter Modules:
My first idea was to get either a 2 terminal or 3 terminal voltmeter. I believe 3 terminal is less invasive to the circuit, but please correct me if I am wrong. My thoughts were that this would need to be powered externally so that it wouldn't effect the voltage within the circuit, whereas the 2 terminal voltmeter is actually using some of the voltage to power itself? Also I was assuming that the 3 terminal voltmeter would not have an effect on the circuit even if it was attached to a common ground within the circuit. Anyways I was wondering if you could verify these assumptions and offer some advice on the best one to use. Or let me know if this is a terrible idea (aside from the fact that is would be space intensive with all the voltmeters) :).

Arduino Voltage Reading
My second idea was to use an Arduino and a multiplexer to sense the voltage within the system. Again I wasn't sure what effect the Arduino would have on the system if any if it is constantly attached and sometimes reading?  The voltage I could sense would be based on the resistors I use. I then could use the Arduino to do something with the signals to make them visible to the user.

If you have any feedback on my questions, the solution you think would be the best, or alternative solutions, I would love to hear it!


texts: How to configure Xbee S2C module(end device) in order to avoid merging of data at another Xbee S2C(coordinator)?

texts:
from India. I am working on a project where multiple xbee s2c devices form a star network, i.e., 1 coordinator and 3 end devices. Each end device attached to the Arduino Uno, coordinator to the NodeMCU.

I am collecting data from all 3 end devices and upload it into my website. But there is a small problem, sometimes the data from 2 or more end devices concatenates.

So 1 way to solve this issue might be write a code in NodeMCU to seperate data before posting it to website.
But (I am an electronics student), I want to know if it is possible to avoid the merging of data at xbee coordinator device itself (maybe, by configuring it with a set of AT commands).
I think a few times, the coordinator receives data from end devices consecutively which is making the serial buffer to perceive the incoming data as single large value. I provided sufficient delays between all 3 end devices, but still sometimes the data is merging.

I read in the datasheet(https://www.digi.com/resources/documentation/digidocs/pdfs/90002002.pdf) that CSMA-CA is implemented in the MAC layer, which means end device wont transmit data till it finds the channel free.

Should I allocate a seperate channel for each end device or should I try increasing baud rates? Your help is greatly appreciated.


texts:
I am trying to analyze the following circuit, in which a photodiode has been replaced by its equivalent circuit:

The circuit has already been analyzed in the document from which I have obtained the above diagram; however, the writing is poor, and so I am forced to trace the steps. In particular, I am trying to compute the feedback factor beta:

Luckily, in the above, there is a hint as to what beta actually is. If we let A be the op amp's open loop gain, then, by definition,
$$ e_o = A(V_+-V_-) $$
Where V_+ and V_- are the voltages at the + and - pins of the op amp, respectively. Since V_+ is at ground, we get that e_o = -AV_-. By rearranging equation (3) in the text, we get, by deductive reasoning, that
$$\beta e_o$$
is simply the voltage at the node joining I_n- and e_n. This implies that \beta is the ratio of the voltage at the output to the voltage at the inverting input.
So I do some circuit analysis to compute this ratio, assuming I_n- is zero. Let V be the voltage at the inverting input. We can simplify our job by solving the following equivalent circuit:

Our goal is then to solve for e_o/V. If we let i be the current through Z_G, then
$$V-e_o=(I-i)Z_F$$
$$V = iZ_G$$
And so
$$\frac{V}{e_o}\left[1+\frac{Z_F}{Z_G}\right]=\frac{IZ_F}{e_o}+1$$
Therefore, beta is dependent on I, the photocurrent through the diode. This is a bizarre result, because in the document, I does not factor in at all into the noise analysis. What have I misunderstood here?


texts: Rx Buffer overflow in MCP2515 CAN controller

texts:
Here is my context: I connect to automobile drivetrain CAN bus (Volkswagen Passat) and sniffer all the traffic.
The problem is that when MCP2515 got a message from CAN and I read it via SPI, the message remains in the buffer. Here is corresponding code snippet (using autowp/arduino-mcp2515 lib with Teensy 3.2):

//loop:
can_frame readMsg = {0};
int status = mcp2515.readMessage(buffer, &readMsg);
if (status == MCP2515::ERROR_OK) {
  ...
}

The code above gets into if always in the loop since we get the first message from CAN. I see in the mcp2515 lib that it runs modifyRegister(MCP_CANINTF, rxb->CANINTF_RXnIF, 0); after the message has been read, so it should clear the buffer, or not?

I also tried couple of other libs - nothing changes. Also tried force cleanup after the message has been read, still with no result:

mcp2515.clearRXnOVR();
mcp2515.clearMERR();
mcp2515.clearInterrupts();

Also tried interrupt mode. In this case all goes well when messages from CAN appear not often, so the microprocessor reads them prior to buffer overflow (ex. with filtering just single ID). But since overflow happened the interrupt stops triggering. Here is corresponding code:

volatile int canMessageQueue = 0;
void canBusInterrupt() {
  canMessageQueue++;
}

// setup:
attachInterrupt(digitalPinToInterrupt(2), canBusInterrupt, FALLING);

// loop:
if (canMessageQueue > 0) {
  uint8_t irq = mcp2515.getInterrupts();
  Serial.println(irq);
  if (irq & MCP2515::CANINTF_ERRIF)
      mcp2515.clearRXnOVR();
  if (irq & MCP2515::CANINTF_RX0IF) {
      CanRead(MCP2515::RXB0);
      canMessageQueue--;
  }
  if (irq & MCP2515::CANINTF_RX1IF) {
      CanRead(MCP2515::RXB1);
      canMessageQueue--;
  }
  if (irq & MCP2515::CANINTF_WAKIF)
      mcp2515.clearInterrupts();
  if (irq & MCP2515::CANINTF_ERRIF)
      mcp2515.clearMERR();
  if (irq & MCP2515::CANINTF_MERRF)
      mcp2515.clearInterrupts();
  if (canMessageQueue > 0) {
      Serial.print("! overflow");
      canMessageQueue = 0;
  }

*The code above taken from CAN Hacker (processInterrupt() in https://github.com/autowp/arduino-canhacker/blob/master/CanHacker.cpp )

Does anybody has any idea why the rx buffer still not getting clear?


texts: Do diode SPICE model parameters affect each other?

texts:
I was modifying a diode spice model to better fit the datasheet parameters (the breakdown voltage on datasheet was 85V, and the model went into breakdown at 65V). I noticed the junction capacitance went from 1.7pF, which was both within datasheet and exactly stated in the model itself (CJO = 1.72pF). After modifying the breakdown voltage the model's junction capacitance went up to 12pF, and lowering the CJO on the model didn't help. Is there any reason that these two parameters would interact with each other? The model is for a BAS116 diode.

Model in question as it's not large:

*SRC=BAS116;DI_BAS116;Diodes;Si;  60.0V  0.215A  3.00us   Diodes Inc.
Switching Diode
.MODEL DI_BAS116 D  ( IS=4.53u RS=0.383 BV=60.0 IBV=5.00n
+ CJO=1.72p  M=0.333 N=4.07 TT=4.32u )


texts: Maximum resistive load on 3 phases 400V, 16 A

texts:
I have several resistive heating element and I want to draw the maximum power from a 400 V, 3 phase, 16 A socket.

If I design the heating elements to connect between phase and null = 230 V RMS * 16 A, I get 3 * 3680 W = 11 kW max Power out of the socket.

If I design the heating elements to connect between two phases I get 400 V RMS, but I can draw less than 16 A * 400 V. How much less?

Is it 12 A per element between two phases?

In which case I can draw 14,4 kW out of the socket.


texts:
ln case of dc shunt motor , how can a field winding produce rotational torque,whose field current is very small when compared to armature current. i mean how can it provide  so much attraction ?
Thanks in advance


texts: Resistance reading on digital multimeter

texts:
I'm working my way through a beginners electronics book (to be specific it's 'Starting Electronics' by Keith Brindley). I've got up to the second chapter which introduces resistors and their colour codes as well as the measurement of a resistance using a multimeter.

I've just gone out and bought my first digital multimeter to attempt some of the experiments detailed in the book. The first involves laying a 10kΩ resistor across a breadboard and using the multimeter to measure the resistance. Its a Tenama 72-2655. The resistance ranges up to 200kΩ  have an accuracy of +- (0.8% reading + 5)

I have put the resistor (brown, black, orange, gold) on the breadboard. Put the black probe into the 'COM' port and the red one into that marked with an Ω symbol and turned the dial to 20kΩ position and turned the device on.

After pressing the probes to either end of the resistor on the breadboard I got a value on the screen of 0.48. My fingers were not in contact with the probes or the resistor. I repeated this again but this time I looped the ends of the resistors around the probes so they weren't touching anything else and tried again here is an image of the result:

The resolution stated in the manual for the 20kΩ reading is 0.01kΩ which I think means the device is telling me the resistance is 0.5kΩ 9.5k less than the stated value of the resistor.

I tried again with other 10kΩ resistors and got the following values:
0.63
1.11
1.12
1.16

When checking the same resistor again the value often changed.
Is my multimeter likely faulty or is there anything obvious i'm doing wrong?

I have updated the question based on the comments and included an image. My initial understanding was based on instructions for an analog meter which I have removed from the question.

Final update on this. Meter was replaced and I can confirm that the original was producing faulty resistance results!


texts: How does a ferromagnetic object entering a solenoid affect the magnetic field?

texts:
So I've been wondering about making a coilgun, and I see that one common thing that has to happen in a coilgun is that a coil has to be rapidly switched on and off, before the iron projectile goes too far and is "stopped" by the electromagnetic field.

I'm trying to figure out how I could control the circuit such that the coil will turn off before the projectile reaches or passe the centre of the magnetic field, and I asked my physics teacher, who said that I should look into using a secondary coil.

His suggestion was that if I were to wrap a secondary around the coil that acts as an electromagnet, when the iron projectile passes through the primary coil (Which is wrapped around a non-conductive PVC pipe), it will affect the magnetic field in a detectable way.

I'm not quite sure how one would go about detecting this change -- hell I'm not even sure what this change is.

Could somebody explain it to me in simpler terms?

Basically, what detectable change would there be on the secondary?

And would it be viable to use this as a method to detect when a projectile enters the coil?


texts:
I am designing a very simple first-order RC band pass filter with cutoff frequencies \$f_l = 0.5 MHz\$ and \$f_h = 4.5MHz\$. I have it pictured below (I'm using 5Spice):

This filter acts the way I want it to. The half power points are around the appropriate cutoff frequencies. For the HPF side of the filter, \$f_h = 1/(2*\pi*100nF*3\Omega)= 0.53MHz\$ and on the LPF side, \$f_l = 1/(2*\pi*1nF*35\Omega)= 4.55MHz \$. Below is the frequency domain plot:

Now, when I change the capacitor and resistance values to something that should yield the same cutoff frequencies, the frequency domain plot looks very different. Here's the modified circuit:

And the cutoff frequencies should be \$f_h = 1/(2*\pi*31.8pF*10K\Omega)= 0.50MHz\$ and on the LPF side, \$f_l = 1/(2*\pi*3.54pF*10K\Omega)= 4.50MHz \$. However, not only does the peak of the signal exist at less than -20 dB:

-3dB from that peak is not at the correct cutoff frequency:

How can these two configurations yield such different results? They both calculate the correct cutoff values, so why are they different in simulation?

Also, in researching this subject I realize that this is a very poor filter and that I should be using a passive RLC band-pass filter or an active one. I'm new to 5Spice, so please suggest any edits to these pictures and I will make them to make this question more readable.


texts: Transformer Line Driver: Avoiding Oscillation

texts:
Summary:

First attempt oscillates, but is somewhat useable anyway.  Does the second attempt:

Actually fix the oscillation?
Present any other potential problems?

Both attempts are described below, with the questions repeated at the end.

Details:

I want to send audio both ways between two rooms using a shielded twisted pair for each direction.  The last time I tried making my own system, it was a bit hacky and both lines insisted on oscillating, sometimes audibly.

Room A had this, with all through-hole parts on isolated perfboard/veroboard:

simulate this circuit – Schematic created using CircuitLab

Room B had this, using Jensen JT-11-FLCF transformers and an Alesis 3630 dual compressor:

simulate this circuit

OutB and InA went to the local sound board.  The 3630's meters (both channels) and the sound board's meters never completely shut off until I unplugged the long cable run from the compressor, and I could sometimes hear a high-pitched drone in addition to the intended sound.  It sounded clean except for the annoying drone, which could be EQ'ed out at the receiving end, but of course that also affected the sound that I wanted as well.

This time around, I want to:

Stop the oscillation
Make both ends identical
Incorporate the compressors directly into the driver circuitry to have one less bulky box

So, I'm thinking about using a THAT4301 "Analog Engine", which includes a VCA, a true-RMS envelope follower, and a couple of opamps, to drive T1 from this app note.  Basically, it's one Jensen JT-DB-E transformer used "normally" to drive the line and a second one used "backwards" to recover a line-level signal from it.

The new project is like this:

This would produce a line-level, isolated output at the receiving end.  Or for an additional listening station, I could just drop a standard mic input directly on the line without a transformer.

The big SMT pads are for C9, to change the "speed" range.  (attack and release times, for those familiar with dynamic range compressors)  The initial value of 10uF is from the datasheet.

Sorry to not have reference designators on the board; it was hard enough just to get all the values on and arranged somewhat sensibly.  I consider that to be more important in case the schematic and BOM disappear.  With a bit of study, you should be able to figure out which is what.

Power is from two 15VDC "wall-warts" wired in series to provide 15-0-15 as required by the 4301, and the entire board is meant to be foam-taped to the two transformers which themselves are foam-taped to a convenient flat spot near the local sound board.

Questions:

Have I actually solved the oscillation problem?
Are there any other potential problems that I haven't addressed?


texts: What prevented widespread adoption of Field-Programmable Analog Arrays?

texts:
I had a lab in which we programmed and measured some basic filters in an FPAA. On paper, these devices seem to be a cool way to process analog signals, and their performance is spot-on with theoretical equations (Which is an exception when doing labs at university ;-) )

Yet, you don't come across these parts very often, if ever, when you take things apart - neither in professional, nor consumer electronics. Why exactly?


texts:
I am sorry if this is inappropriate question, but this little flashlight spiked my curiosity. Sadly I wasn't able to understand it by myself.

Why there is a inductor in there? What allows it to have three modes (on, off, strobe)? What voltage does LED take? Because I tried applying battery to it and it didn't light up.

[1
[
[
[


texts: Do cells phones put out a signal when charged through data out?

texts: Do cells phones put out a signal when fully charged through data out? I am wondering this because there is a competition to see who can build the best and most efficient portable cell phone battery backup


texts: Memory row driver does not have enough driving power

texts:
I am building the row driver of a piece of RRAM. Different from traditional memory, RRAM's cells are composed of resistor-like elements. I tried using a single inverter and a back-to-back inverter design (shown below), but they don't have enough driving power. The row line voltage is only about 25u Volts when connected with a grounded, 200-Ohms resistor. Ideally, the output voltage should be the same as the pumped voltage (VDDP). I am wondering how to achieve this?
Thank in advance for any advice!


texts: Concept of the static keyword from the perspective of embedded C

texts:
static volatile unsigned char   PORTB   @ 0x06;

This is a line of code in a PIC microcontroller header file. The @ operator is used to store the PORTB value inside the address 0x06, which is a register inside the PIC controller that represents PORTB. Up to this point, I have a clear idea.

This line is declared as a global variable inside a header file (.h). So, from what I came to know about the C language, a "static global variable" is not visible to any other file - or, simply, static global variables / functions cannot be used outside of the current file.

Then, how can this keyword PORTB be visible to my main source file and many other header files which I created manually?

On my main source file, I only added the header file #include pic.h Does this have something to do with my question?


texts: Which diagram is better for common mode noise rejection?

texts:
I want to us this sensor(107LN type) as in the following signal chain with differential-input DAQ board and a STP CAT6 cable as below:

Above the GND of the power supply is local/near to the DAQ. Someone told me this will be problem for differential inputs.

So I created a new ground on the sensor X (GND) from B (GND) on the sensor.
Now along the transmission to the DAQ, the ground and the signal is twisted together. See below diagram:

Is the second diagram better for common mode noise rejection? Why?


texts: How much do max current specs matter on VCC and GND?

texts:
I know that each of the output pins on most chips have a specification for the maximum power that can be drawn from that pin.

However, some chips also have a spec for the max. current through VCC and ground, and these specs are less than the sum of all possible output currents for the chip.

So, why do those total current specs exist, and is it okay to exceed them?  (I wouldn't want to exceed the current spec. on a pin that actually does something, but for something passive like VCC, it sounds safe enough...)


texts:
I want to design a chip level circuit to connect USB 3 port to several USB 2 devices. I think the best way is using a Hub like TUSB8041, TI 4 port hub USB 3. As far as I know, the USB 2 and 3 are compatible, then it seems that simply I can connect four USB2 to the USB 3 hub connections, then I have 4xUSB2 is connected to one USB3.
But the problem is that in USB2 Devices we have D+ and D- for data and in the USB3  we have SSRX- SSRX+ SSTX- and SSTX+.
in summary,
1) is it correct to connect 4xUSB2 to one USB3 in a USB3 Hub?
2) how can I connect a 4-pin USB2 device to a 5-pin USB 3?


texts: STM32F103 - internal temperature sensor ADC doesn't change value

texts:
I am currently trying to get the ADC of a STM32F103 running. My first exercise is to read the internal temperature sensor. This is my current approach:

void initADC(){
    RCC->APB2ENR |= (1<<9);      //Enable ADC1 Clock
    RCC->CFGR |= (0b10<<14);     //set ADC Prescaler '6'
    ADC1->CR1 |= (1<<4);         //Input Channel 16
    ADC1->SMPR1 |= (0b100<<18);  //41.5 cycles sample time
    ADC1->CR2 |= (1<<23);        //Enable Temperature Sensor & Vref

    ADC1->CR2 |= (1<<0);         //Enable ADC and start conversion

    ADC1->CR2 |= (1<<3);         //Initialize calibration register
    while(ADC1->CR2 & (1<<3)){   //Wait until calibration register initialized
        ;
    }

    ADC1->CR2 |= (1<<2);         //Enable calibration
    while(ADC1->CR2 & (1<<2)){   //Wait until calibration completed
        ;
    }
}

uint32_t getADCTempValue(){
    ADC1->CR2 |= (1<<0);         //Enable ADC and start conversion
    while(!(ADC1->SR & (1<<1))){ //Wait until end of conversion
        ;
    }
    return ADC1->DR;
}

These are some sample values I get:

  2428 2417 2412 2400 2389 2381 2376 2380 2392 2406 2410

But no matter what I do (touching the controller, blowing at the controller) the value doesn't change significantly.


texts: High speed control loop with high resolution ADC

texts:
I'm designing a digital lab power supply for the sake of learning and also because I need one lol. I'm planning to use a simple 50Hz transformer with a Buck converter (I know this brings switching noise and that a linear solution would be much cleaner in terms of noise but I don't want big heatsinks) so I will be implementing a PID controller with a dsPIC sampling at about 1MSPS.

The dsPIC only has 10 bit ADC which also isn't the best ADC and I would like to have a resolution in the output voltage of 10mV or 5mV so for this I would need a higher resolution and better external ADC like a 16 or 14 bit ADC. The problem with this ADCs is that they are really slow (1 to 10KSPS) so I can't implement my control loop with this.

How is this done on commercial power supplies?

They use a lower resolution and faster ADC to implement the control loop to prevent over-shoot and then when the output is settled read from the high resolution ADC which is also the voltage displayed to the user?
They just use a low speed ADC and the over-shoot/oscillations are compensated with passive components?
The control loop is implemented with analog components and the ADC are only to the display the voltage to the user?
They use an expensive high resolution and fast ADC?


texts: Is there a relativily simple way to determine state of charge (SoC) for LiFePO4 batteries?

texts: I'm searching for information regarding this matter and I can only find academic papers. I am wondering if anyone knows of any (more accurate or less accurate) way to evaluate the state of charge for batteries with LifePo4 chemistry. Prefer something simple that could be implements using a microcontroller.


texts: What type of glue would you use on set potentiometer screws on a PCB?

texts: I want to set my potentiometer screws and then glue them in place so they will not be readjusted by the end user and I have seen green adhesive on them before?  Any suggestions as to what is best to use on this type of application?  Thank you.


texts:
I've recently bought 5V/1A USB power supplies, and since the packaging was slightly damaged (specified in the auction I bought it from), I thought about testing it before connecting to anything sensitive.

Since it's a USB-A receptacle and I have the corresponding socket in my parts supply, I was thinking simply about soldering leads to Pin 1 and 4, connecting those through a resistor, and the connecting a multimeter in series or in parallel to the resistor for measuring current and voltage output. I'll be using 10W resistors to stay on the safe side (with the lowest resistance of 5 Ohms, of course).

My questions is: is there something inherent in the USB standard that will cause problems, or worse, hazards, with this test setup?

Also, a side-question: is it safe to base this type of setup on a typical breadboard and 22 AWG cables?


texts: Error in Practical Electronics for Inventors?

texts:
I’ve been studying this book for digital electronics.

I think that the highlighted values in the operation of the shown AOI gate are not correct and should be 0 instead.


texts:
I have an arduino based home temperature monitoring system using Ambient Weather F007th wireless Thermo-Hygrometers as sensors. I am trying to work out the CRC and add some code to my project to reduce the number of bad readings.

I have 1000s of sample readings and from that have constructed two sample data sets with 1 bit difference. The last byte is the CRC.

FD   45   77   14   80   31   A5
FD   45   77   14   81   31   E6
FD   45   77   14   82   31   23
FD   45   77   14   84   31   98
FD   45   77   14   88   31   DF

FD   45   7B   44   80   30   FD
FD   45   7B   44   81   30   BE
FD   45   7B   44   82   30   7B
FD   45   7B   44   84   30   C0
FD   45   7B   44   88   30   87

Using advice from other sites I have identified that the XOR of the first CRC against the following CRC produces the same sequence for both sets.

A5 ^ E6 = 43
A5 ^ 23 = 86
A5 ^ 98 = 3D
A5 ^ DF = 7A

FD ^ BE = 43
FD ^ 7B = 86
FD ^ C0 = 3D
FD ^ 87 = 7A

I have also established that this sequence represents lines 14 to 17 of the 0x31 CRC-8.

But now I am stuck. I cannot replicate the CRC results with other data.

I would appreciate any ideas. I have thousands of datapoints if anybody wants more


texts: What's the name of this battery connector?

texts:
Been trying to find this "battery bridge" as a spare part to old virtual pets. It's like cell battery connector, but it's individual part connecting two cell batteries (LR44), which has their other plus and minus connectors on circuit board. I have no idea is this something that is still made.
This part usually gets ruined because of corrosion if old batteries are left inside device. Would need replacement ones, but can't find real name for this part.


texts: 18650 pack with many series BMS for faster charging?

texts:
I'm building a 1200W portable stereo system powered by repurposed laptop Li-Ion cells. In order to get a minimum 8 hour play time at maximum volume, as well as provide some external power via an inverter, I've designed a 14S4p battery with appropriate BMS, with the idea to put 3 in parallel to meet my 25A discharge requirements and provide even more capacity. I know this is going to be heavy but I'm not trying to build a toss-in-the-backpack kind of bluetooth speaker here.

A 14s pack charging at 0.5c is going to take well over a day to charge, no good if I want to use the system again tomorrow.  I find my self wondering if it is possible/feasible/advisable to do the following:

Build 3s1p packs, each with their own BMS, and place 5 packs in series for a 55.5-63V output (to feed the amp through a 48V converter), and then parallel 12 of these for a 24Ah capacity. At 0.5c each 3s1p pack would charge in ~6 hours, as massive win over the 14s' 28 hours.


texts: Is there a difference between "voltage supply" and "power supply"?

texts:
A device, circuit, actuator or chemical structure which outputs a fixed voltage level is usually called with one of the following terms.

Voltage Source
Voltage Supply
Power Supply

Is there any technical difference between these terms or do they imply the same thing?


texts: How to adjust inverter for various loads

texts: I am building sine wave inverter (currently in Proteus) and I have a problem with various loads - choosing LC filter for one load doesn't work for other. How should I solve this problem? Should I adjust PWM using PID to achieve sine? What LC should I choose then? For biggest load? - get perfect sine on highest load and then adjusting PWM for lower? Because lower load with higer load's LC gets square wave. Low load LC with high load gets spiky low wave.


texts: Why we use a 2nd order filter to build a higher order filter?

texts:
Why would we use 2nd order filters to build a higher order filter, like a Sallen & Key and others?

Is the oscillation problem in higher order filters?


texts: Confused on MOSFET terms (velocity limited, mobility limited, constant mobility)

texts:
So we're learning about transistors, but we don't much of the physics behind how they work (yet) so these terms are quite strange to me. The models we've used are "velocity limited", "mobility limited", and "constant mobility". In some models, the relation between drain current and gate-source voltage is linear and in others it's based on a square law. What do these terms mean, and where do the square or linear relationships come from?

Here's the equation for velocity-limited characteristics:
\$I_d=V_{sat} C_{ox} W_g (V_{gs}-V_t) (1+\lambda V_{ds})\$

And this is for mobility limited (which they also refer to as constant mobility):
\$I_d=\frac{1}{2} \mu C_{ox} \frac{W_g}{L_g} (V_{gs}-V_t)^2 (1+\lambda V_{ds})\$


texts: Circuit to "zoom in" on mV fluctuations of a DC signal?

texts:
I have a signal that is roughly 0.2V + noise fluctuations of order 0.1-2 mV. Ideally I want to amplify this signal such that the mV fluctuations become about 1V. In other words I want to amplify the signal by about 1000x.

However, if I flat out amplify the signal, the total signal becomes 200V + 1V fluctuations, which I can't reasonably read on some bench top DAQ (0-10V range).

Is there some combination of circuit elements that can take my input 0.2V + 1mV signal and spit out only the amplified fluctuations (i.e. 0V + 1V fluctuations)?

I should say that these fluctuations are controlled by me physically squeezing a pressure gauge, so they aren't necessarily high frequency. Basically the signal rises to 0.202V when I squeeze, and 0.200V when I let go. I want to see that excess 0.002V blown up to 1V, but I may be squeezing and letting go slowly in general.


texts: Can I use op-amp together with PCM5102A?

texts: Is it possible to use op-amp with PCM5102A? In my application the load is much lower than 10k, so as a result I have much lower Vrms than it's defined in the data-sheet (2.1V). Maybe it's possible to use op-amp together with this chip or should I use a different chip for this application then?


texts: Isolate coil from battery using two transistors triggered by Hall sensor

texts:
My current, simplified pulsed electric motor driver circuit is shown in the image below on the left.

The base of the PNP transistor is connected to a A3144E Hall sensor, and this pulses the coil when the rotor magnet passes by the drive coil shown in the circuit.
The incoming rotor magnet also induces a counter EMF in the coil (per Lenz and Faraday), which will create a load on the battery.
This load I want to block by isolating the coil from the battery using a second transistor above the drive coil, until we initiate the pulse.
I tried the circuit on the right, where two PNP transistors are driven from the same Hall sensor signal, but in the simulation this seemed to greatly diminish the power flowing through the coil.
How can I correctly trigger two transistors, one on each end of a coil, from the same Hall sensor signal?
Thanks!
UPDATE
Since some commenters seem to suggest that the single PNP transistor does not work, here is the proof that it actually works very well:
https://youtu.be/X33VJsSbThQ
Also, here is (part of) a circuit someone uses to do exactly what I am trying to do (isolate the coil from the circuit) using two MOSFETS:

I don't fully understand the exact way in which it works, and he seems to use a low side P-channel FET switch.
The difference is that his Hall signal is inverted and so HIGH when a magnet passes.


texts:
I’m trying to ‘hack’ a LED Fire-effect light bulb to work on a 9v battery.

Using a multimeter I can see that the bulb converts mains voltage to 5v.  I’ve got my hands on a 9v-to-5v voltage regulator (spec sheet - https://dm-components.com/eBay%20pdf/AMS1117.pdf) and did some experiments.

When I plug my multimeter into a simple battery circuit I get 7v (the battery I’m using must be a little flat).

However, when I put the multimeter into the voltage-out part of the regulator, I get 6.3v…not the 5v I’m expecting.

What am I missing? And any advice for a newbie to electronics on how to convert 9v battery to 5v?


texts: How do I determine the area of copper needed on a PCB to provide adequate heatsinking for a power SMD MOSFET?

texts:
I am planning to use the IRFR5305PBF Power MOSFET (http://www.irf.com/product-info/datasheets/data/irfr5305pbf.pdf) to switch on a load. I have determined that I need an external heatsink with Rthsa < 29 C/W.

How would I go about determining the area of copper on the PCB required to provide a thermal resistance of < 29 C/W?

I have tried searching on Google and the IEEE database, but the articles do not clearly show me how to calculate this.

edit: I am using a 4 layer PCB with 1 oz copper on the top and bottom, and 0.5oz copper for the inner layers.


texts: Feasibility of introducing RF delay via PCB trace?

texts:
The Background

My main background is embedded software but I have had to debug the analog circuitry myself so I've picked up a little bit here and there, enough so to describe the problem in a coherent way to someone who could give me a solution. At my work, I was on a project where we were developing a hand-held radar transceiver that operated in the single Ghz frequency range. One particularly thorny issue that we never resolved was the antenna connectors we used introduced ringing artifacts in the receive signal. To prove this as a source we would put 50ohm terminators instead of the antennas and would observe a significant decrease in the noise in the signal. We also observed decreasing noise as we introduced progressively longer lengths of cable between the Tx/Rx connector and their respective antennas. So the initial conclusion was to introduce delay between the connectors and their antennas to dissipate the ringing and make our lives easier on the Rx side.

The Problem

So the real problem is how do we implement that delay, preferable 15-20ns worth, where space is our main constraint (the last board we built was two dual-side 10cm x 10cm boards, one for the electronics and the other for the antennas with the aforementioned connectors between the two boards)? I had once suggested drawing out trace paths between the connectors and antennas in the same manner as illustrated in this question except that's for digital signals and my limited experience with analog signals has taught me that analog RF signals are a lot more pickier than digital signals. Never did get to try out my idea and now the project is on hold for lack of funding.

The Question

So if nothing else I'd like an answer to whether using PCB traces for large analog RF delay is a feasible idea and what pitfalls would need to be considered. Is this even a common practice or does the RF world rely on special circuits to do that function? Another project which I was involved in had the same problem and used a gated switch as a solution which worked but added quite a bit more components (guesstimate of 25% extra space required). I'm mostly looking for a general argument about how this problem could be approached but references would also be appreciated (even if its way above my head!). Thanks.


texts: How to connect HY-M285 Solid State Relay?

texts:
I have just bought a HY-M285 SSR that I want to allow a 12V DC signal to control a 240V AC mains signal. I'm using this to let the 12V output from my amplifier switch my active sub-woofer on and off.
The AC side of the relay is trivial - it's just two screw terminals. Unfortunately, the DC side has three terminals, labelled DC+, DC- and CH1. So, my question is: how do I connect the 12V control signal? I've tried across DC+ & DC- with no effect.
Do I need to construct a voltage divider, to push (say) 5V through the CH1 connector, as well as the DC+/- inputs? Or can I get away with something much simpler - e.g. +12V direct to CH1?
Apologies for the lack of detail but the module doesn't include any documentation whatsoever, so I'm hoping that someone here may have prior experience.
Thanks.


texts: Integrator Design for Small Input Signal

texts:
I am designing an integrator circuit using op-amp. The circuit works very well for inputs greater than 7mVACRMS from 10Hz to 2KHz (error is inside 1%). The issue I am having now is when the AC input less than 5mV, the output the integrator has big error. About -15% error when the input is 1mVRMS sine wave.  The following is the circuit I am using now. Does anyone have ideas about how to design an integrator for small input signal with high accuracy? Thanks in advanced!

The circuit is designed for time constant tau=0.0026. So at 61.45Hz, the output equals to the input value. The tau value in the following circuit is 5 times less than 0.0026, So at 61.45Hz, if the input is 1mVACRMS, the output should be 5mVACRMS. But I only measured 4.3mVACRMS. If the input is 30Hz, 1mVACRMS, the output should be 10mVACRMS, but only measured 8.6mVACRMS.

C30(0.022uf) is a 2% film cap and R16(23.7K) is 1% resistor. C33 coupling cap is 20% Tan or ceramic cap. The power for the amp is +-3.3V.


texts: High Frequency, High Power Amplification

texts:
I was wondering if anyone could give me a little information on amplifiers.

What would be the best way to amplifying a small, 1v @ 1mA, very high frequency signal (3-5MHz) to a high power signal? The output signal would also need to be around 3-5MHz and something like 12v @ 1A.

My question is, what amplifier system would preform this task well, or the best? One option is using a class E amplifier with a square wave signal, or just purchasing a direct high power, high frequency OP AMP.

Unfortunately I don't think any of these "OP AMPS" exist, so I'm looking to build my own circuit. Preferably something simple, but anything that works will do.

Has anyone got any suggestions of which amplification system would work the best in this situation?

EDIT:
After some advice, it looks as if the OPA564 chip would be the best fit for this task. What other components are necessary to operate the chip? Or can I just operate it straight out of the box? Basically I'd like some advice on how I can successfully operate the chip.


texts: why my power calculation for this resistor is wrong?

texts:
i encountered a very simple question in a test and i easily calculated the answer
but somehow i am making a mistake because i can not find my answer between the available answers, what am i doing wrong ?
thanks.

Question : Calculate the wasted power on the 6 ohm resistor.

my current answer using KVL :
(i*2) - 16 - (4*i) + 4 + (6 * i) - (3 * (4 * i)) = 0
(- 8 * i) = 12
i = -(12 / 8)  A

now power for 6 ohm resistor
p = vi = i^2 * r
p = ((12 / 8) ^ 2) * 6 = 13.5 w


texts: Most efficient h bridge to run two DC motors in robotics application

texts:
EDIT: I was mistaken about the motors, I actually have a pair of DC motors

I want to construct an h bridge that would allow me to control the servos in a boebot. However, I want to maximize the speed and torque attainable. Two wheeled servo bots are common, so I was wondering if there are any existing robust and efficient designs available for something like this?

to clarify, I need this to not be a packaged hbridge. I have to construct it on a breadboard, and that requires transistors and diodes.

Should I do darlingtons?


texts: Modify the output voltage on a PWM controller to fall within LED driver range

texts:
I'm trying to use a simple PWM controller (this) as a dimmer for a Meanwell LED driver (this).
The driver accepts PWM dimming but needs a voltage range of ~2-8V, and the PWM controller outputs 7-12V when powered by the 12V input I'll be using.
Is there an easy way I can modify the controller to get the voltage down to this range?
Would lowering the input voltage lower the output range too? Or could I simply change the value of the pot/add in a resistor or two, or would that destroy the PWM signal?
I will be repositioning the potentiometer from the controller as space is very limited in my use case, so some soldering is required anyway. However the theory on this is a bit beyond my skill level.
Many thanks for any help on this


texts: I've bought a few metal halide lamps (specifically Osram HCI-TC 70 W/830 WDL PB) and electronic ballasts for them to have really bright light in my room in winter (like this guy). The ballasts' lamp connections are labeled LL and LH for low and high-voltage, and the manufacturer's manual emphasizes the importance of connecting the lamps correctly, but the lamps themselves are not labeled anywhere and I couldn't find how to identify which pin is the high-voltage one (starter). Please help! The lamps look like this:


texts: DIY ammeter for measuring currents as low as 0.1mA

texts:
I want to measure current as small as 0.1mA
I tried looking for current sense amplifiers but I didn't find any which can work at this range.
Please suggest some DIY solution.
Note:

Please don't ask "Why do I need this?", "What is the current source?"
Please don't suggest ready made expensive market ammeters.

Current is DC, 10-15 uA error is tolerable, steps can be as large as 10 uA,  max current will be less than 5mA. Voltage drop of 5% is acceptable (applied biased on my load will vary from 10 V DC to 30V DC)
Budget is not an issue, I want to make it myself. No preference regarding recording.


texts:
For a battery powered circuit, I need a VERY low quiescent current voltage regulator.
Input voltage is 20V lithium battery, output voltage is 5V (or 3.3V, precision not necessary) for a microcontroller circuit.
The max current, when uC is working, should be at least 50 mA.
The quiescent current of the regulator itself (when uC is in sleep mode) should be no more than 10uA.
On the battery terminals, there are transients of 40V to be expected.
Any ideas?
No automotive application, but sort of power tool. The uC, when in "sleep mode", waits for "years" until it detects a "keypressed" by the user, before starting the engine. The whole appliance is very cost sensitive, so the regulator should be in a price range of 0.1..0.2 USD @ 10K pa. If anyone has a cheap 20uA solution: welcome.


texts: Which remote communcation type should I use?

texts:
In my project I have to give only 4-digit number to each device(50+ devices) without any wire. And there will be only one transmitter for all receivers. Which communcation type should I use?

Frequency of requests will be 10 seconds for every device.
Range will be maximum 150 meters.
And power doesnt important, but 1xAA battery will be great
P.S: Cost is imporant for now


texts:
So I built the following circuit to amplify the output from my microphone. I am testing it using a 1KHz sinewave of 10mV peak value. The Mic is biased using a 10k resistor. The signal is input into a common emitter amplifier with a AC gain of around 115. Next to connect the speaker, I used a Common Collector stage to increase the input impedance seen by the first stage.

However, when I connect the speaker, the output is as follows:

I know this is a problem of the low resistance load, but I would like to hear a possible solution for this problem. Do I need to add another stage?


texts:
I'm trying to use a MOSFET, an N-channel (specifically IRLB8721PbF), with a gate controlled by an AVR to power on/off a Raspberry Pi (powered through GPIO), I'm using it on the low side. (Both share the same +5 V rail).

When I measure the Raspberry Pi's current draw, it seems limited, and it doesn't operate properly.

On that MOSFET:

Gate: To AVR digital pin (and pulled low with a 10k resistor)
Drain: To Raspberry Pi GPIO ground
Source: To GND

Naturally, my 5 V from my power supply is directly to the Raspberry Pi GPIO 5 V.

As a kind of experiment control: I just power the Raspberry Pi directly from my power supply 5 V/ground. I measure the current the Raspberry Pi draws through 5 V with a multimeter, and during power up it fluctuates from 0.15 A (up to about 0.45 A) and settles at about 0.35 A.

However, when I measure how much current the Raspberry Pi draws when connected to the MOSFET and when I turn the gate on -- it seems the current is limited and it gets up to about 0.30 A (approx) and never gets higher, and the Raspberry Pi seems to never fully power on.

I'm curious if I'm missing something here with trying to power this on. It is indeed a logic-level MOSFET, but, as an experiment I've tried powering the MOSFET at varying voltages with a bench power supply -- but no noticeable change by using more voltage (up to 10 V I tried.)

Granted, I am more of a programmer and electronics technician -- so I appreciate any electronics engineering input and advice, but, pragmatic solutions are most appreciated. I'm just so puzzled as the MOSFET should be rated up to 60 A, and I would've thought that just applying a logic-level voltage I would've been able to draw more current through the MOSFET.

Here's a diagram of the circuit (please note: I can re-create this situation without the microcontroller at all, and just with the Raspberry Pi + bench power + MOSFET, as diagramed). Note that in this representation the Raspberry Pi GPIO connection is simplified and in this diagram pin 1 on the jumper = 5 V, and pin 2 = GND.

Update: It turns out the voltage drop on the MOSFET is enough to give the Raspberry Pi fits. A friend of mine pointed it out in the data sheet, and here's a screen capture of the exact graph that shows where approximately 0.15 V are dropped, which can be measured on source and drain (as pointed out early on! great eyes guys, I really appreciate). I have decided to instead use a relay.


texts: I have 2.2 volts low impedance AC from a constant source. If I build a transformer to input 2.2v on the primary and output 120v on the secondary can I expect to operate any household appliances, such as a 1000 watt microwave?


texts: Level-triggered mono-stable multi-vibrator running at 12+ volts.

texts: I need a CMOS (preferably dual) level-triggered mono-stable multi-vibrator that runs at least 12V (better at 15~18VDC), perhaps in the CD4000 family. Everything I have found is edge-triggered only or is in the TTL families which won't operate at the voltages I need. Even an edge-triggered with set pin (instead of reset pin) will do as long as it stays in the pulse while the set pin is held active. The circuit must be continuously retriggered by holding the set pin active. The problem with edge-triggered here is that, if the trigger value never returns back to its idle state, the pulse will complete and no edge will come to retrigger it. A power transistor will turn back on and will go up in smoke. This is for a circuit to protect against shorts.


texts:
In altera FPGA documentation they make reference to a "I/O weak pullup" functionality.

I would like to use internal weak pull up instead of external pullups , avoiding a PCB modification.

It seems is possible to activate weak pull up for an I/O in quartus.
But there is no information on how to activate it.

Any hints?


texts: Efficiency or longevity issues when using 2 lamps on a 4-lamp fluorescent ballast?

texts:
To answer this question I guess we need to know the circuit construction details of commercial electronic fluorescent ballasts.  Is there a downside (either power efficiency or ballast longevity) when connecting only 2 lamps to a 4-lamp electronic ballast?
Bonus question:  The ballast is spec'd for T-8 lamps, but I intend to use T-12 lamps, so what is the possible downside of using T-12 lamps in a T-8 spec'd ballast?  (I've been running a 4-lamp fixture in this mode for more than a year with no negative effects seen).
Maybe a more general question is - what exactly changes in terms of electrical excitation / voltage / current draw when a fluorescent tube lamp changes in diameter from 1 inch to 1.5 inches?


texts: If someone wanted to make a barebones dev board, what is needed to get an a9 processor running? Is it reasonable for a school project or will attempting to route the ddr memory and getting it functioning correctly be too difficult a project?


texts: Turning the TV-B-Gone into a universal remote

texts:
Ok, so I don't really want to turn the TV-B-Gone into a universal remote, specifically, but I would like to know/learn how I could go about creating a universal remote (I merely thought that working off of the TV-B-Gone would be a good point to start).

So yeah, anyone have any ideas as to how to go about making a universal remote? (ie: Can change channels, volume, on/off, maybe even the tv source...)


texts:
I have one ideal and one practical differentitiator circuit in Multisim to which I am applying a positive, say 10 V step response. The output I get has a much lower settling time at final value of 0 for practical differentiator whereas the ideal differentiator oscillates which makes perfect sense for me. However, this output (see shape below) seems to start from a random big negative value for both which I do not understand as I expected it to be a positive big value as even under ideal step input the Dirac delta function goes to positive infinity and for s simulated step input the gradient is still likely to be very high rather than low.Both my differentiators are in inverted configuration but I do not think this should affect expected output. Can anyone please point me to a resource where I can study why do I get a negative initial value from my differentiator for a positive step input.
I think it is saturating to the negative rail, why the negative rail and not positive.


texts: Design review - RGB LED color mixer using PWM

texts:
I'm trying to make an RGB color mixer. LED strip runs on 0.5-2A. It has internal resistors. LED Strip needs 5v, has one pin for that, one for red, one for green, and one for blue. Each LED module that you can cut off was about an inch an a half, actually a little less, and there's 5.5' of the strip, I think there's around 40 LEDs in the strip. I found this video online, but this is the exact LED strip I got.
https://www.youtube.com/watch?v=sN5_Hjq_9Jg.

simulate this circuit – Schematic created using CircuitLab

Original schematic.

I will be using a total of 6 volts. i saw a video where a guy made a PWM circuit, https://www.youtube.com/watch?v=x4RmIzUd2lk, and it looked something like this.

simulate this circuit

555-based PWM control.

simulate this circuit

Tidied-up schematic.

I meant for the threshold to connect to the trigger, but I couldn't get it to.
I'm confused on how to pick my resistors, my pot, and my capacitor, because in a different video, it said something like 1.44/(R1+R2+R2)*C1=Frequency. I assume frequency is how fast the LED flickers? In this schematic, there's 2 capacitors, which do I use in the equation? Does higher frequency mean faster flickering? How fast would be too fast for the naked eye? How do I control which I way I turn the pot to make the lights brighter. And how do I know how much current is coming out of the the output? How can I control that so it doesn't burn out my LED?


texts: What kind of Op Amp configuration is this?

texts: I am trying to understand the circuit that is a part of a sensor module. I don't know what exactly it is doing. The Vin signal is an AC signal.


texts: Can the Intel Curie modules be programmed in assembly using the Quark toolchain?

texts:
I've been looking over an Intel Curie module for a project.

From the datasheet it looks like the Curie module contains an Intel Quark D1000 embedded processor along with a lot of other components. I'd like to use those components in my design.

From all of the documentation I can find, it looks like the Curie's toolchain only supports using a higher level toolkit (which only seems to support their real-time Zephyr RTOS).

But the quark has a development environment called Intel System Studio that supports using assembly, C, and can run on Linux and Windows.

If I use the Curie module will I still be able to do development at a low level using the Intel System Studio, upload code and debug it via JTAG tools, or will I not be able to do this?

I'm OK with writing my own stuff for the other modules in the Curie module module. I'm thinking that the higher level things just add some libraries and calling wrappers for those things. If that's the only issue I'm ok with that. I'm just wanting to know if anyone has experience with this and I'll be able to write using the Intel System Studio.


texts:
I'm trying to build a circuit with the following properties:

When a switch (SW1) is pressed continuously, it should supply a particular load with 5V (modeled as R4 and LED D2) after about 20sec
When this switch is released, to preserve battery it should not draw any power

After looking at schematics on the internet I've tried the following circuit, unfortunately without any luck.

I've tried simulating with LTSpice, it seems no matter how I change the values the NPN tranistor doesn't want to turn on.

My circuit is probably seriously flawed, could anyone push me in the right direction?

simulate this circuit – Schematic created using CircuitLab


texts:
How can I generate a 100KHz PWM Signal in Ltspice?
How do I calculate Ton and Tperiode?


texts: Arduino hacked rc car, H bridge, logic voltage overwhelmed

texts:
I have hacked my old rc car like in this tutorial here

I have measured manually the h bridge logic voltage (the voltage that the transceiver send to the h bridge) , which is 3.7volt

in the tutorial, the guy is sending 5v (instead of 3.7) from the output pin of the arduino to the hbridge, isn't that dangerous for the h bridge?
would it be possible to send pwm to control the motor speed, even if the h bridge wasn't constructed for this? (the original car only have 1 speed) (I'm afraid of breaking my h-bridge or my motor if I send pwm...)


texts: Help identify a water level sensor in humidifier

texts:
I have this ultrasonic humidifier that looks like this:

It has a piezoelectric transducer that produces the vapor. It also has a sensor that turns it off when the water runs out. The unit now just switches off once I turn it on and I think its the low water sensor that is giving false readings. Only thing is, I'm not sure how this low water sensor reader works.

It looks like it has some little metal plate suspended on a spring that goes next to the transducer. Can anyone help identify how this is sensing the water level, and potentially how I can 'hack' it to alter the reading.

The chip on the board has no markings on it...


texts: Is it more reliable to connect to both sets of DPDT relay contacts when only SPDT is needed?

texts:
I am adding a socket mounted relay to a PCB and only need one set of contacts (SPDT).
Does it increase the reliability of the component to connect the both sets of contacts?
Are there any other issues this creates? Common practice or bad practice?

Note that I do not intend to exceed the rated current of a single contact.
Just thinking through the failure modes it seems that if a relay fails on or off mechanically it wouldn't make the situation any worse. And it would reduce the odds of failing electrically by 50% since one contact would be the first to make, and the same or different contact would be the last to break.
Thanks!


texts: Does kinking the wire of a psu affect power ouput?

texts: Just like the title says; does kinking the cable from a psu(2.5A 5v) to the socket affect the noticeable peformance of a psu? It is just slightly kinked at multiple places.


texts: ARM7 Memory model (Flash, SRAM, registers. ...)

texts:
I ma newbie in ARM world. I am have basic background working with AVR controllers. AVR has separate physical memory blocks (like EEPROM, FLASH, Data). It is very easy to find a lot of tutorials explaining memory model for AVR.

But I cannot find any good explanation of memory model for ARM (ARM7 in my case).
I want to understand how this memory is located physically.
As I can guess there are two types of memory in ARM - Flash (for firmware) and General Memory for all other data.
ARM is mostly 32bit so it can address up to 4GB of data, but of course ARM SoC has much less amount of memory, but it is possible to attach external devices.

So explain or provide good article where ARM memory model explained and will help to find answers for such questions.
 1. What happens after power on of ARM processor (AFAIK it starts to process RESET interrupt handler) how programm is fetched from MEMORY (where this memory from physical and logical perspective).
 2. I understand that it is single chip, but memory can be located near CPU (like in x86 architecture SRAM caches and so on) other memory can be connected via the bust with CPU.
 3. As I know most ARMs are based on Von Neuman architecture, does is strictly follow this architecture ?

Thank you for help in advance.


texts:
I've got a long run of some LPD8806 driver-based LED strips (which use an SPI connection) that I am controlling via a Raspberry Pi. It controls it just great, but when I have the LEDs all off (not powered down completely, just having told the driver chips to clear the LED) a few of the lights will eventually turn on. It's really weird, just a few will turn on to random colors after they've been sitting for several hours. Usually 4 or 5 in a row and often somewhere in the middle of the strip.

What I can't figure out is how they are they are getting these random signals. Could it be something with my connection to the SPI pins on the Raspberry Pi? I have the SPI Data out and Clock pins running through a level converter from Adafruit to bring the signal level from 3.3V up to the 5V of the strips.

I'm more of a software guy, so I'm probably just missing something silly. Do the signal lines need some sort of filtering cap maybe?

Update: I've got 2 rolls, 5 meters each, connected in one long run. I am injecting power at the very beginning of the run and where the second roll connects to the first (otherwise the very last pixels were browning out).

What I've noticed now is that it's only ever pixels at the very beginning of the second roll that are turning on. Not sure why, but maybe this will give a clue to what's happening?

I'm up for trying a cap across the power lines... but have no idea what value to use. The highest rated 10uF cap I have on hand is rated for 100V but it's still tiny. Can't imagine that could handle 10A (since I'd have to wire in one cap for each separate power run).


texts: What happens to a polarity sensitive capacitor when you feed a square wave through it?

texts:
Consider the following circuit.

simulate this circuit – Schematic created using CircuitLab

The output wave form will look like this

Orange - input signal
Blue - output signal

The Wikipedia entry on Electrolytic capacitors says

  Nevertheless, electrolytic capacitors can withstand for short instants
  a reverse voltage for a limited number of cycles. In detail aluminum
  electrolytic capacitors with non-solid electrolyte can withstand a
  reverse voltage of about 1 V to 1.5 V. This reverse voltage should
  never be used to determine the maximum reverse voltage under which a
  capacitor can be used permanently

It does not specify what a short duration is.

Since polarized capacitors are meant to be used one way, will the falling edge's dv/dt damage the capacitor ?


texts: How to handle large number of analog inputs and outputs

texts:
I am collaborating with a friend on a synthesizer project, but I am very new to embedded systems design. I have a solid background in software engineering but am a greenhorn when it comes to embedded design.

A little description of the project: my friend has built an analog synthesizer that has ~20 potentiometers that control the same amount of synthesis parameters. Being an analog synthesizer, these pots directly control the voltage that goes to the various parameters. We want to put a microcontroller between these pots and their parameters that will enable us to save and recall patches, effectively bypassing the voltage that the pots are set at. The basic flow for one of these pot/parameter combos with a microcontroller involved would look as such:

Potentiometer -> ADC -> Microcontroller -> DAC -> Analog synth parameter

There will effectively be two modes of operation: realtime control (the analog value read in from the pot is outputted to the parameter unmodifed) and recall mode (the user recalls a saved patch, and instead of the potentiometer's value a recalled value would be outputted to the parameter. If the pot is moved, then the pot's value is used.)

I have been able to build a prototype that can demonstrate this functionality on an MSP430 board for one pot/parameter pair, but the problem is that the board has very limited ADCs and DACs. My question is, how do I go about finding a board that can support the number of ADCs and DACs that I need? Would I have to use multiple microcontrollers? Is there such a thing as an ADC/DAC multiplexer? What is the best practice for this type of scenario? This is where the world of embedded systems alludes me.

Another thing to add is that we are also concerned with sampling rate, as anything that is too low might sound too "jagged" when turning the pots, but we figure this is something we will have to test with our ears before settling on a number. We have, however, decided that we want to have at least 10 bit resolution for the ins and outs.

Any advice would be greatly appreciated.


texts: Will PCB assemblers solder wires to the board?

texts: When preparing a medium run prototype, are there any manufacturers out there who will solder wires to you if you ask? For example, I have a device with 6 sensor pins. I'm hoping that a manufacturer, in the US or overseas, would be willing to solder 10 cm wire to each of these pins prior to shipment, to make manufacturing easier. Is this a typical request?


texts: How start running STM32 firmware from IROM2 in Keil Microvision?

texts:
I'm developing an embedded application using Keil MicroVision 4 & STM32F103RE
I've splited Flash memory of device into two areas (IROM1 & IROM2) using IDE target options panel (Target tab, Read only memory areas section) & also setted IROM2 as default & startup, but seems the program does NOT run from specified address.
Should I do anything more than told configurations to start running program from an address rather than FLASH_BASE (0x08000000 in my case)?


texts: Schmitt Trigger: Problems between theory and reality

texts:
I want to say that I am not a native English speaker so you may find some writing errors. Also, I am just learning electronics, so sorry if some questions are poorly formulated.

I am trying to build a proximity alarm. In order to achieve this, I want to compare an electrical signal from a distance measuring sensor unit (you can find its datasheet here: Datasheet). This sensor gives me a signal from 20 to 150 cm, so, what I want to occur is for the alarm to turn on when something is blocking the sensor at approximately 40 cm.

To generate this comparator, I am using a Schmitt Trigger. I set up (experimentally) the resistances in order to give a threshold of 40 cm. Here is the schematic.

simulate this circuit – Schematic created using CircuitLab

I have found the desired output, but with some problems:

The actual thresholds are not equal to the theoretical thresholds.
When I connect a buzzer in parallel with the output, the voltage falls a lot and it sounds very low. How can i fix this?

And the questions are:

Why are the experimental and theoretical thresholds not equal?
How can I couple a simple buzzer?
Is the biasing correct?
If I want to add an LED, how can I connect it?

PD1: The input wave is there just to give a reference because I can't simulate the sensor.

PD2: The calculations of the thresholds:

\$V_{high} = \frac{R3}{R1+R2+R3}V_{CC} - 0.7\text{ V} = 2.3\text{ V}\$
\$V_{low} = \frac{R3}{R1 + R2 + R3 + \frac{R1 \cdot R3}{R5}}V_{CC} + 0.7\text{ V} = 2.78\text{ V}\$


texts:
I am new to FPGA development and to verilog and I am currently working on a project that involves outputting stuff to the screen via VGA port. I only get access to actual FPGA board when I am in class but I like coding when I am at home as well. I was looking for an easy way to test the VGA output but I could not find anything suitable for verilog. Could someone please let me know how can I test my VGA output of my verilog program in simulation?

Thank you.


texts: How do I determine the courtyard for a component footprint?

texts:
I'm using KiCad to lay out PCBs for some projects and often I find I need to develop a new footprint or tweak one that's in the library.

I'm able to determine most things I need by consulting the datasheet and occasional other sources, but I haven't found anything about how to determine the dimensions and positioning of the courtyard. I understand the courtyard is the minimal "reserved" space for the component, such that no two courtyards should overlap. However, I don't see it stated on any of the datasheets so far.

All of my projects so far will be hand-assembled (by me :), so I won't be needing it for pick-and-place machine purposes. However, being an engineer I don't feel comfortable not getting it right while I'm in there editing something. Also I will be submitting any worthy new footprints for inclusion in the official KiCad library, so I want to make sure I get it right.

How does one determine the courtyard for a PCB part footprint?


texts: How to recognize USB to RS232 null modem cable

texts: I have been trying to establish connection between my PC and uC development kit over serial line. There is a standard serial port on the development kit. In oposite there is only USB ports on my laptop. So I have used USB to serial cable for the connection. The problem is that I am not sure whether it is a so called null-modem cable. Can anybody more experienced tell me how to double check it? Thanks in advance.


texts: How do I make use of multipliers to generate a simple adder?

texts:
I'm trying to synthesize an Altera circuit using as few logic elements as possible. Also, embedded multipliers do not count against logic elements, so I should be using them. So far the circuit looks correct in terms of functionality. However, the following module uses a large amount of logic elements. It uses 24 logic elements and I'm not sure why since it should be using 8 + a couple of combinational gates for the case block.

I suspect the adder but I'm not 100% sure. If my suspicion is correct however, is it possible to use multipliers as a simple adder?

module alu #(parameter N = 8)
(
    output logic [N-1:0] alu_res,
    input [N-1:0] a,
    input [N-1:0] b,
    input [1:0] op,
    input clk
);

wire [7:0] dataa, datab;
wire [15:0] result;

// instantiate embedded 8-bit signed multiplier
mult mult8bit (.*);

// assign multiplier operands
assign dataa = a;
assign datab = b;

always_comb
    unique case (op)
        // LW
        2'b00:  alu_res = 8'b0;
        // ADD
        2'b01:  alu_res = a + b;
        // MUL
        2'b10:  alu_res = result[2*N-2:N-1]; // a is a fraction
        // MOV
        2'b11:  alu_res = a;
    endcase

endmodule


texts: Why would you bypass a zener diode in the flyback protection of a relay coil?

texts:
SparkFun sells a relay control kit that you solder together.  On the back of the circuit board there is a pair of metal contacts that are labeled "bridge for zener bypass".  I assume you put a small blob of solder there to bypass the zener diode.

https://www.sparkfun.com/products/13815

My question is, why would you want to bypass the zener diode?  What do you loose and what do you gain when doing so?

Thanks!


texts: What is the relation between the stator current and motor rpm for an AC motor?

texts:
A 3 phase AC motor is rated values are: 970 rpm, 50Hz, 380V delta 47A.

A VFD drives this motor for obtaining a constant wind-speed which rpm is proportional.
The thing is when 885 rpm the stator drives 35A and when at 840 rpm the stator drives 33A.
The wind-speed is not regulated well enough.

Doesn't current supposed to be same in this application for a constant torque?


texts: Overshoot and undershoot on clock signal

texts:
I have created a 50% duty cycle, 8 MHz clock signal on the ATmega32, 0V to 1V.

What I see when measuring this clock signal with the oscilloscope is overshoot and undershoot of about +0.2V on both sides, after every change of voltage level. It is not really a problem for my project, but I am wondering why this happens?

Added: Oscilloscope trace

(Source)


texts: How to select power source for robot actuator with known torque requirement

texts:
I am building a robotic actuator that will be backdrivable, this robot will have pretty low RPM. I will be using brushless DC motors. I am trying to figure out requirements for the power source. I have the motor data sheet, but we would like to run the motors at higher voltages to get more juice out of them. I know the required torque the motors would need to produce. Below is the derivation I used to find the required current and power. When I plug in all the known values, I get numbers that seem inaccurate. For instance, if I say req'd torque = 2.5 N-m, Kv = 473, max RPM = 50, I get current = 123 A and req'd power = 1.6 Watts.

I would really just like to know if I am going about this correctly as far as the calculation of the req'd values. I am also wondering if power required for stall torque would be equal to power required for no-load max RPM?

*The 1.25 is a safety factor recommended on one of the links below. Also Ia = current of the armature. I assumed this was the same as req'd current but I am not sure.

Here are two links I used for my derivation:

https://en.wikipedia.org/wiki/Motor_constants

https://things-in-motion.blogspot.com/2018/12/how-to-select-right-power-source-for.html

This is the data sheet:


texts: How does the Roland TR-909 reset circuit work

texts:
I'm troubleshooting my Roland TR-909 drum machine, which doesn't power on anymore. All of the voltages come up fine, but the reset line stays low. My suspicion is one or more of the components of the reset circuit have failed. Edit: the trace connecting D702 and D701 is highZ and C704 in the same area looks like it's leaked some electrolyte, which probably caused an open on the trace.

My understanding after staring at it for a little while is as follows:

At first I thought D701's purpose in life is to bring the drive voltage of Q701 down below 5V so as not to forward bias it's Vbc, but the excess voltage would still be dropped across R702.

Question 1: What is D701's purpose? (Note the schem was revised from a 6.8V to a 5.6V zener at some point)

Question 2: Why not just drive Q701 from the 7805 directly by removing D701, and connecting the output of the 7805 to where the anode of D701 used to be?

Q701/Q702 and surrounding resistors function as an inverter use output is high when power is applied. When power is not applied, the transistors are off, the 7805 is off, and it's output is low, pulling reset low via R705.

R705 and C701 set an RC time constant such that RESET goes high roughly 30ms (6 time constants) after 5V is up.

Question 2: Why is an inverter needed here? Wouldn't the circuit work easily as well with just R705 and C701?


texts: 5v Signal to 24v Input for CNC Machine Probe

texts:
Background Info
I have a CNC probe which acts just like a NC switch and opens when triggered, I am trying to modify a circuit for use with my CNC machine controller inputs which use a 24v signal to the input pin. However the voltage that this uses is 5v and not the 24v my CNC controller is expecting so will not trigger the signal.
The reason for this circuit is to reduce the current and voltage on the probe contacts to prevent pitting of the contacts over prolonged use.
My question
How can I trigger the 24v input pin with the circuit attached? Is it possible to modify the supply voltage of the circuit to run on 24v or to maybe modify the transistor part to switch the 24v? I also looked at using an optocoupler. The circuit needs to run as fast as possible to detect the probe trigger.
There are 2 versions of the circuit, inverting and non-inverting. I am not 100% sure which one would be better here. I have attached the circuits and controller inputs.
Many thanks for any assistance.
Link to example circuits - https://www.cnczone.com/forums/tormach-personal-cnc-mill/325794-tormach-7.html
CNC Controller Input

Inverting Signal Circuit

Non-Inverting Signal Circuit


texts: Wireless Relay triggered by continuous voltage

texts:
Does anyone know of a wireless relay product that can be triggered by continuous voltage?  Obviously that is how a wired relay works, I just want to add a load to a spot that has 12v already wired but i don't want to have to run a  trigger wire to that spot.
Ideally I would like to simply connect a premade transmitter to a existing switch.  For my current application I have a light on one side of my boat, I want to make another light on the other side go on as well but without running a cable to it.  I just want to put a relay inline and leave its switch on such that the switch on the other side light controls both lights.
I have found almost what i want in the form a of a relay and a small key fob remote, but that is not what i need.  Alternatively I might be better asking how to make a transmitter for the above product that is triggered by applying a constant voltage??? The above light project is my current application, but if I could make/buy something it could be applied all over my boat and be really useful in avoiding the pain and destruction involved in running wires on my boat.


texts: Product design requirements to pass FCC regulations

texts:
I've been spending a lot of time looking at 47 CRF 15, and specifically .231, and I don't understand how these limits are possible for many products. I'm designing a remote control for a product that needs to work from 150-200 feet away. It has 6 buttons and is addressable with DIP switches, so the amount of data being sent is tiny. It's basically a glorified garage door opener.

I have a product that is similar to the one I'm designing, and it has the range I need, but the specs say it outputs 10mW or 10dBm, and if I'm reading the FCC guidelines right, that's 1000 times the limit.

A couple more specs in case it matters: the transmitter is based on the PT2262 chip, and is operating at 315mHz using a 12V battery with an antenna on the circuit board traces.

My question is 1) How can I build something that has 150-200 ft. range and still be within FCC specs? 2) Am I reading something wrong or is there some exception that will let me pass FCC or avoid it? 3) How do other devices, like garage door openers, get away with it?


texts:
I have several tiny connectors ( about 1 mm pitch, various numbers of pins per connector ) that have the letters "MXJ" molded into them.
(I wish I knew what company the are from, or even better the exact part number, but I don't see any other identifying marks on the connector).

What does that "MXJ" mean?

Googling for "MXJ connector" gives me many links to a software package, and some links to pages that talk about a variety of connectors but don't actually have the word "MXJ" on the page.

Edit: My specific electronics design problem is that I have a gadget I want to interface to that uses such connectors, and I hope that I could find a matching connector rather than soldering a bunch of individual wires to the PCB.
While the particular gadget I have may be extremely niche, I suspect closely related connectors are used in other gadgets used around the world for decades, making this question generally applicable to many future visitors worldwide.


texts:
I'm trying to understand why, on this circuit bit, they used pull-ups resistors between logic ICs of the 74LS and CD4000 families. Specifically I'm talking about resistor array RM1 and R1. All the ICs on this circuit are supplied by 5V.
As far as I know, pull-ups are needed when you have open-collector/gate outputs/input, and not for TTL and CMOS devices, am I wrong?


texts:
I have a car equipment with a cable that should be plugged into a cigarette lighter (12v).

I'd like to tweak a bit, and connect it at home to a standard 12V power supply.

However, I can't figure if the connector is standard and, if yes, the kind of connector.

Here is a picture of the cable connector, which is plugged into the device:

Does anyone know how to name this connector (and thus search for buying one)?


texts: Interrupts are firing when touching ground with metallic things

texts:
I'm making a circuit on a breadboard (before SMD design) for a battery-powered device.
When USB is connected to any wall-adapter, the device wakes up when touching any ground wire on the breadboard with another metallic wire using my bare hands.

About the circuit:
On the Atmega328p-PU, an falling Interrupt on INT0 (with internal pullup) wakes it from deep sleep.
Normally, there are other ICs such as an TP5046 envolved, but I removed them all until this simple circuit and the problem still persists.
I wanted to do "Diode-Oring" between the battery and usb power, so the device doesn't use the battery while charging.

Does anyone know whats going on? Or if it's just a software error on the Atmega?

I think it has something to with my body capacitance, like touch sensors work. But even with stronger external pull-Up resistors and low pass filters on INT0, it fires the interrupt and wakes it up.


texts:
Would need to identify this cable for a replacements:

Codes:
PF000624.02

KW 1947 38

Data Matrix Code: 1STHGCW0020P42

Pins: 15

The cable  is from DJI Mavic Mini controller (CE version) ant it connects the main board with contoller buttons.


texts: Voltage across a capacitor variable of integration

texts:
I understand that something that is charged with one coulomb and has a potential difference of one volt across it will have a capacitance of one farad. \$C = \frac{q}{V}\$. I get that because current is the derivative of charge with respect to time, \$I = C\frac{dV}{dt}\$.

This is where I start to get confused. If you divide both sides by \$C\$ and integrate with respect to time, shouldn't that just give you \$V = \frac{q}{C}\$?

What I don't get is how this becomes \$V(t) = \frac{1}{C}\int_{t_{0}}^{t}I(\tau)\, d\tau + V(t_{0})\$.

This is saying that \$q = \int_{t_{0}}^{t}I(\tau)\, d\tau + V(t_{0})\$. I don't get why, though.

Shouldn't \$q = \int I\, dt\$ and that be the end of it? I mean, obviously this isn't the case since my textbook and everything I can find online says otherwise, but I don't get it.


texts: Wien Bridge Oscillator in Multsim Values

texts: I am trying to build a Wien Bridge Oscillator in Multisim that has a frequency of 3.6 kHz. However my graph is very distorted and I'm guessing its because of the op amp component values. Does anyone have any recommendations to fix this?


texts:
Any help would be appreciated as I am new to LED drivers. I have a very basic understanding of electronics and I'm not up to designing my own driver yet.

I have tried to power this LED with a Meanwell LDD-1200 from 5 or 6 lithium batteries but the voltage varies as the batteries discharge and the LDD uses 3V dropping the output voltage.

If someone doesn't mind sould you please design a circuit for me?

If a driver already exists that isn't too expensive or too large (i intend to use this LED for mounting biking, i have only one functioning cochlear and i rely on vision for balance at night)

The short of it:
I am wanting to drive a Cree CXA1512 LED @ 1200ma with a dimming control.

The Long of it:
I would like a Switch Mode (I hear that switch mode produces the least heat)  Constant Current (1200ma) driver with dimming if possible (not necessary but preferable).

The CXA1512 runs at 18V and max current is 1200ma.

Intended battery pack would either be 5 or 6 lithium cells (3.7V 3200ma) in series OR parallel depending on whether a buck or a boost system would be best/easiest.

For dimming I'd like a potentiometer. I'd like to stay away from micro controllers.

Would it also be possible for the design to be scalable? I.E. change a few component values to run a string of 4 cree XML leds, which differ in current and voltage.
Or make the circuit adjustable so one could adjust the CC value and then the voltage to suit.

I was originally trying to fit the circuit into an existing bike LED light shell but I realise that the circuit may need to fit on the battery pack instead, however the smaller the form factor the better.

Thankyou for you time in advance.

Roy


texts:
If a capacitor has a time-varying capacitance, such that C(t) = C_0 + Kt, where K>0 is a constant. Then is charge-voltage relation, Q(t) = C(t)V(t) = (C_0 + Kt)V(t), valid? It should be noted that here the multiplicative relation implies term-by-term multiplication of  C(t) and V(t) at any given time t. This ignores the mutual dependence of  C(t) and V(t) that arises because of the time-varying C(t). A continuously time-varying capacitance changes the charge Q(t) which in turn changes the V(t) across the plates. So the standard relation may not be valid here.
Or should the multiplicative relation should be changed to the convolution one in the time domain as, Q(t) = C(t)*dV(t)dt = (C_0 + Kt)*dV(t)/dt?


texts: Controllable rising edge shifting circuit using CMOS

texts:
I am building a circuit using CMOS transistors (350n technology) in which I have to delay the rising edge of a pulse but not the falling edge. The circuit I made is the following :
And here is the result I obtain:

I have to make the delay controllable by adding an analog input and this delay has to be as linearly dependent on the analog input as possible. My first idea was to add a NMOS transistor between transistors M3 and M8 and therefore control the speed of discharge of the capacitor but this does not make the control linearly dependent.
What is the best way to do this and how can I improve my circuit (to make Vout sharper for example) ?


texts:
I am working on a project using a Virtex-5 FPGA. The small projects that I've worked on with FPGAs has only required me to program the FPGAs on development boards using JTAG or loading the bit file onto the FPGA. However, I have a newly designed board using an FPGA which I don't believe has even been powered on yet.

I was doing a bit of reading about the FPGA requiring to be configured and was also reading the Configuration guide which talks about the internal memory being written with the configuration data. I don't know if I've missed something or if Xilinx ISE automatically does that when I program the FPGA with it. Can someone shed any additional light on this ?

Thanks!


texts:
I think I need a SPST 12V 30 Amp Latching relay.

I would like to fit the circuit to my van for a machine which cannot be run whilst the vehicle is in motion, therefore I will use a micro switch with the clutch pedal, therefore when the clutch pedal is pressed the machine does not work. I will be wiring the micro switch output in to the relay (coil side), then put a negative to the other side of the coil. Then I will have a common from the battery to the relay. Then I will have the output of the relay to the machines on/off switch.

Now my problem is that I would also like a momentary switch in this circuit somewhere, so that even if the clutch is not pressed the machine is not on. I cannot use the normal machine off off switch as it is too far in the back of the van. Where would I put this switch and which exact relay do I need for this setup.


texts:
I have the three-stage amplifier below. I am interested in finding the output resistance of it. Just wanna check if am doing it correctly? Thanks

simulate this circuit – Schematic created using CircuitLab

Analysis:
\begin{equation}
i_o=i_2-i_1\\i_1=i_{b3}+g_{m3}v_{\pi 3}\\i_o=i_2-i_{b3}-g_{m3}v_{\pi 3}\\i_o=\frac{v_o}{2.4k\Omega }-\frac{\left(v_{\pi 3}-v_o\right)}{r_{\pi 3}+5.6k\Omega }-g_{m3}v_{\pi 3}\\v_{\pi }=-v_o\\i_o=\frac{v_o}{2.4k\Omega \:}-\frac{\left(-v_o-v_o\right)}{r_{\pi \:3}+5.6k\Omega \:}-g_{m3}\left(-v_o\right)\\i_o=\frac{v_o}{2.4k\Omega \:}+\frac{\left(2v_o\right)}{r_{\pi \:3}+5.6k\Omega \:}+g_{m3}\left(v_o\right)\\g_{m3}=77.6m\left(\frac{A}{V}\right)\\R_o=\frac{v_o}{i_o}=12.7\Omega
\end{equation}


texts:
I'm a bit confused regarding the stability of a differentiator and an integrator. When an integrator is added to the system it decreases the stability as it adds a pole at origin and bends the root locus of the system transfer function towards right of the plane but adding a differentiator increases the stability as it adds a zero at origin, which bends the root locus of the system transfer function to the left.
When considering the transfer function of a unity feedback system as \$G(s)={1/s}\$, the root locus tends towards the right of the plane..

Hence my question is: What is the stability of the system with transfer function \${1/s}\$?


texts:
If there are multiple bus masters possible in a bus architecture then is it certain that 'Bus arbitration' will take place before a master gets hold of the bus control or is it possible that bus control is handed over to another master without bus arbitration taking place? Theoretically it may be possible but I want to know this with reference to well known practical buses which are in vogue in industry these days, for example, Ethernet, PCI, PCIe, RS422, RS485, SCSI, SPI, I2C, 1553, USB , CAN, Modbus and others.

I am not at all expecting that someone will make a list for these buses. Instead what I expect is that if someone as any knowledge about a specific bus w.r.t its bus-arbitration then it would suffice if he/she can share that here.


texts: 555 Clock Circuit - how to choose resistor value?

texts:
I need to design a 555 clock circuit to output a clock pulse of a specific frequency. The circuit I'm using is this one (from here):

I've used this circuit before and it works fine but the website only shows what resistor value to use for a few predetermined frequencies, which are all far too low for what I need. Is there an equation for working out what value of that resistor I should be using?

edit:

After looking at the datasheet, I'm still struggling to find the solution as the circuit in the sheet is different, though the one I'm using is tried and tested by myself recently. I'm also limited on what ICs I can use as I only have whats provided to me which is why I'm using an NE555.

Can anyone help with what would be a could resistor value to output the highest frequency clock possible for that chip?


texts: Expert advice needed on electric bike battery setup

texts: I'm currently building an electric bike for a competition. I know I want a 15s lithium ion NCM battery (max 4.2 volts/cell), but don't have a battery management system or a balance charger than can handle 15s. I don't want to spend money on a battery management system or a charger either, as I want to use as many parts as I already have. I have a charger than can charge up to 4s, so I'm thinking to physically split the 15s battery into three 4s packs and one 3s pack. So far so good. But then I want to connect them in series to get overall 15s. Will I run into any voltage imbalance issues when discharging? Thinking of using multiple connectors leading into one discharge connector.


texts:
I have modified a schematic for my project with the following image:

Instead of a 20K potentiometer, I use 100K for more precise adjustment.

Do I need to add a disk capacitor of 10nf or 100nf to Pin 5 IC?

Is the resistor of 1K between Pin 3 and Q1 a good choice?

Is it better to use NPN or PNP transistor?

Do you think the modified circuit is good or should I add another component?


texts: For measuring IV curves, could you use a current source and measure the voltage?

texts: I was trying to find other experiments that required getting an IV curve but all of them seem to be applying voltage and measuring the current.


texts: Two way communication between one master and multiple nodes

texts:
I have an architecture like this:

Master - It contains an RF communication chip. All nodes rely on Master to receive and send data to a central unit.

Node - It has some basic GPIO functionality. There can be 4-5 different types of nodes, each requiring a different GPIO count. For the sake of design simplicity, I am planning to throw a cheap microcontroller on each node and handle all GPIO locally. That way I just need a pre-defined control data packet from the master to do any task. Similarly, the node will send a pre-defined packet which the master will understand. The packet definition will contain the node type.

Nodes can change in number and preferably should be hot-swappable. Communication works like this:

Two nodes do not communicate directly.

Master can have a data packet which it wants to send to any particular node.

Any node can have a data packet which it wants to send to the master.

Max distance between a node and master will be less than 50 cm.

After some thought, this is the plan I came up with:

Make all nodes communicate over i2c. 16 nodes per master seems to be a good number so I can put a 4 bit DIP switch to set the i2c address of each node. Basically I will be doing a digital read on 4 gpio and setting the address accordingly.

This will be perfect when master wants to read or write data to the nodes.

For the time when node wants to send data, I need to have an additional GPIO per node which alerts the master that some data is present. Alternatively, I can keep reading all nodes in the loop and keep checking if some data is available.

Is there a better solution to this problem?


texts: LM317 / linear regulator, estimate of heat capacity

texts:
Quick question - what do you think the heat capacity of a LM317 might be? The use case is that I want to ignite e-matches, which requires are short duration high current and would prefer to just use bunch of linear regulators without a heatsink. But I have no idea what the thermal capacity of a LM317 might be, and I don't want to kill the regulators!
I think I would need something like 10-15W of heat dissipation for maybe 100ms.


texts: I know that an op-amp tries to hold the input voltages the same. So, for virtual ground we can connect + node to the ground and we're getting a 0V on the - node. If the op-amp tries to keep the inputs the same, why are we not getting a virtual ground on the + node if we connect - node to ground?


texts:
I am learning Altium designer. In PCB library design window the mechanical position information box is moving with cursor. How do I dock it to the window?

I tired to reset the interface to defaults from preferences. It did not help.


texts:
For an electronics project I am using a Schmitt Trigger relaxation oscillator. The equation for voltage across a capacitor in time t is

$$V_c = V_s(1-e^{\frac{-t}{RC}})$$

My Schmitt Trigger uses a 1mF capacitor and a 5k resistor. The threshold voltages of the chip I am using are 0.9 and 3.6V. Rearranging the equation for t gives

$$t = -RCln(\frac{V_c}{V_s})$$

Inserting values into the equation to see how long it takes to charge the capacitor from 0.9V to 3.6V gives t to be approximately 7 seconds. In experiment however the entire period of the oscillator is only about 2.5 seconds. What have I got wrong in the theory?

Diagram:


texts: What happens when plates of a fully charged capacitor are isolated from each other?

texts:
I'm a mechanical engineering student and I'm working on a project that involves a high voltage capacitor.

I understand that when the separation between the plates  of a charged capacitor is increased, the voltage increases. But I'd really like to know what happens to the plates if  the capacitor is fully charged , disconnected from the charging circuit and then the plates are moved apart from each other by an infinite distance. Will each plate remain charged?


texts: How does a micro interpret high freq rf signals from an antenna

texts: If an antenna is receiving a frequency higher than the clock speed of the cpu, then how is the cpu able to interpret the data being received by its antenna?