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  1. KrisBlueNZ

    Emergency Power Supply Schematic Diagram

    You haven't replaced the diodes with properly rated ones. You don't need R5. The gate-source pulldown resistor I mentioned in my last post was on Q1 not Q3. Changing Q1 from a MOSFET to a junction transistor doesn't make it current-controlled instead of voltage-controlled. The circuit still...
  2. KrisBlueNZ

    Emergency Power Supply Schematic Diagram

    There are many problems with your schematic. D2 is a 1N4148, and D3 and D4 are BAT54s. These are small signal diodes rated for 200 mA maximum! Q1 and Q2 don't need to be power MOSFETs. The ones you've specified are rated for 14A or more! If you used those parts because of a limitation with...
  3. KrisBlueNZ

    SMPS boost regulator using a schmitt trigger oscillator

    R2 seems to be left over from the design in post #4 when feedback was applied differently. I don't see any need for it now. IC1B is needed because when Q2 conducts and disables the oscillator, IC1A's output will go high, but you want the MOSFET to turn OFF.
  4. KrisBlueNZ

    Implementing fuzzy logic in PIC18F4431 in MPLAB using c language programming

    Do you know about Google?
  5. KrisBlueNZ

    pic 16f877a program problem

    I don't have one. Are you asking me to write your code for you? Post photos of both sides of all of the circuit boards inside the TC303AX. They need to be in focus, and all the component markings need to be readable. Do you understand multiplexing?
  6. KrisBlueNZ

    No voltage drop

    No problem :-)
  7. KrisBlueNZ

    PIC Multiple Timer Interrupt Problem

    Have you forgotten to set the PR2 register? What PIC device are you using?
  8. KrisBlueNZ

    Virtual grounds

    Or you can use the TLE2426 which connects across the rails and generates the virtual ground. http://www.ti.com/lit/ds/symlink/tle2426.pdf
  9. KrisBlueNZ

    Digital clock using DS3234

    I agree with kpatz's post. Good advice there. Do you plan to multiplex the displays? It doesn't sound like you do. In that case you'll need seven separately controllable digital outputs for each digit. A serial-input parallel-output shift register like the 74HC595 is a good choice here. You can...
  10. KrisBlueNZ

    pic 16f877a program problem

    OK, I will help with the program once you have worked out where to get the segment and digit control signals on the boards inside the TC303AX and drawn up a schematic diagram of your PIC circuit. Do you know where to get those signals? If not, I will help you find out. I need to see both sides...
  11. KrisBlueNZ

    RC Network Spike Generator Confusion

    That's right.
  12. KrisBlueNZ

    pic 16f877a program problem

    It will be simpler to connect to the logic-level signals (0V/5V) which drive the anodes and cathodes of the display. If you do that, you won't need any op-amps or comparators. Yes you will need to connect the 0V rail of the TC303AX to the 0V rail of your PIC circuit. You may also be able to use...
  13. KrisBlueNZ

    RC Network Spike Generator Confusion

    The simple answer is that when the input has been at +5V and the output has stabilised at 0V (due to the action of the resistor), the capacitor is charged to 5V. The left hand plate is 5V more positive than the right hand plate. So if you suddenly bring the left hand plate down to 0V, the...
  14. KrisBlueNZ

    pic 16f877a program problem

    When you measure voltage across segments in the display, you will not see 5V for several reasons. First, the forward voltage of a single red LED is around 2V (if the segment is powered from 5V, the remaining 3V is dropped across the current limiting resistor). Second, each digit is only enabled...
  15. KrisBlueNZ

    pic 16f877a program problem

    OK, that's useful information. It should be possible to do what you want, but there is some hardware and software work required. That multiple-digit LED display must be driven using multiplexing. If you don't know what that is, Google multiplexed led display drive. To read the contents of...
  16. KrisBlueNZ

    low voltage comparison/amplification

    Yes, you would normally connect the 0V rail of one circuit to the 0V rail of the other circuit. Try just connecting the 0V rails together. If this causes a problem, the two circuits were not completely isolated from each other, so you need to fix that. If the problem only shows up when you...
  17. KrisBlueNZ

    Rectifier Help

    I would start by shortening all of those long insulated wires. Personally I would try to use copper wires (component leads bent along under the board, and offcuts) for as many connections as possible. That might involve changing the component positioning slightly so that the whole board...
  18. KrisBlueNZ

    pic 16f877a program problem

    LOL :-) Go Bob! Go Bob! Which microcontroller are you going to use? shrinivasdevkar, can you answer some basic questions. What is driving the displays? What is the product? Some kind of counter? What supply voltages are available? Have you done microcontroller development before? If so...
  19. KrisBlueNZ

    Rectifier Help

    Hi Anthony and welcome to Electronics Point :-) Can you upload a photo of each side of your circuit board? How is the op-amp IC powered? Have you used decoupling capacitors? How is the ground rail obtained?
  20. KrisBlueNZ

    Digital clock using DS3234

    Sure, any crystal-controlled circuit will be far more accurate than an R-C oscillator. An R-C oscillator would be a terrible timing source! But (depending on where you live) the AC mains frequency is an accurate reference. In the countries that I know of, it is adjusted so that over the medium...
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