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  1. R

    Detecting positive and negative edges

    Hi Steve, Thanks for your help. My idea was to get the edges detected by differentiator, clean edges using Schmitt trigger, then feed this into PIC interrupt to detect high to low edge, start timer, detect low to high edge, stop timer. Calculate the width using timer value and then compare...
  2. R

    Detecting positive and negative edges

    Hi, Thanks for your advice. The sound patterns are totally asynchronous, so I would need a interrupt to capture the first edge. Can I still do this with capture feature? Best regards Rajinder
  3. R

    Detecting positive and negative edges

    Hi, The sound patterns vary in pulse width. So can I connect this straight to an pic I/O port that has interrupt on change. Would I need any circuitry at all? Where does the Schmitt trigger come into this? My idea for the differentiator was to detect edges, clean them up then feed the to I/O...
  4. R

    Detecting positive and negative edges

    Yes, I'm looking at using a interrupt to detect the edge, start timer and then on next edge stop timer. I wasn't sure if the Schmitt trigger would just clean up the edge or if it will give me a small pulse to represent the edge. Any thoughts? Best regards, Raj
  5. R

    Detecting positive and negative edges

    Hi all, I need some advice. I have different sound patterns that are driven from a microcontroller. They vary in pulse width and duration according to the different alarm patterns. They are used to drive a piezo circuit. I need to monitor the sound patterns to determine which alarm occurred...
  6. R

    Understanding if this circuit

    Hi here is the complete diagram. I have shown the output resistor that connects to the input of my CO alarm. I think I can have the drain at 0V, which isore positive than the negative source and the gate is also positive wrt source. Best regards, Rajinder
  7. R

    Understanding if this circuit

    Hi all, Sorry but i will post the complete schematic today. My apologies. Best regards, Rajinder
  8. R

    Understanding if this circuit

    R8 is fed from a inverting opampnwith gain if -1. R7 has various resistors switched in to give me different currents. This is a negative constant current circuit. the inverting amplifier sends a voltage. To the pin of the opamp pin 3, the FET is in the loop and ensures that pin2 of opamp is at...
  9. R

    Understanding if this circuit

    R7 is fed from a inverting stage opamp with gain of -1 using 100k at input and 100k at output stages. The other end of the opamp I switch Different value resistors from 10k to 1m to give different negative currents.
  10. R

    Understanding if this circuit

    Hi, sorry my apologies. The output is the other end of R60 the 10K resistor. Si my thinking was that the opamp keeps inputs the same. Hence the voltage at the top end of R60 will be same as Vin. Therefore I = -Vin/R60. I was not sure of the Drain at 0V and Source at negative. I think it is in...
  11. R

    Understanding if this circuit

    Hi All, I was wondering if somebodycan give me some help in understanding this circuit. The first stage is a inverting amplifier stagevwith gain of -1. If I put in 0.5V I then get -0.5V. This goes into a second stage which the N channel FET is in the feedback loop of the opamp, It is a negative...
  12. R

    Programmable negative constant current source

    Hi Steve, Thanks for your help. My understanding is as below: The inverting amplifier is there to give me a negative output from the input with a gain of -1. So 1V I/p will give me 1V o/p. The feedback sense resistor will feed a voltage back to the opamp input. Because of the virtual earth of...
  13. R

    Led flashing for one second using Mikro c

    Ok, thanks will have a look. I tried just lighting an led in the interrupt, first thing. To see if the interrupt was being serviced, but it didn't light. I think the issue may be that, not sure. I am new to Mikro c.
  14. R

    Led flashing for one second using Mikro c

    I set up, the prescaler, timer0 to be in 8 bit mode, I then set the intcon register to 0xA0, enable global interrupts and enable timer0 interrupt. It's in the main code.
  15. R

    Led flashing for one second using Mikro c

    It's a pic 18f45k20. The one used on the debug express that comes with pic kit 3. Sorry for the wrong info.
  16. R

    Led flashing for one second using Mikro c

    Here is the code again.
  17. R

    Led flashing for one second using Mikro c

    Ok will do. Thanks.
  18. R

    Led flashing for one second using Mikro c

    Hi All, I am currently writing some code in C on Mikro C platform. The program is supposed to doba led chaser on port D of pic18f54k20, I am using debug PCB on pickit 3. Then it's supposed to flash led on port c bit 0 every second. It does the led chaser routine but never goes into the...
  19. R

    Capacitor / filtering for PSU

    No, the PSU data sheet doesn't mention anything about bulk capacitor decoupling etc
  20. R

    Capacitor / filtering for PSU

    Thanks for your replies. I thought that a PI filter may be used with a 100uF cap. The PSU is a switched mode offering +5V, +/-12V. It will be used to power a couple of opamp (OP1177), LP3985 LDO to generate 3V3. All these will have decoupling caps 100nF I am not sure about what I need from the...
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