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  1. BobK

    Small Circuit needed for New Product Design - Help!

    That kind of LCD requires 1 pin for each segment + 1 pin for common. It cannot be multiplexed. So you have 15 pins taken up for the display, a 14 pin PIC isn't going to do it. As I mentioned before a 20 pin PIC is minimal, and would have no room for expansion. I am not certain of this, but...
  2. BobK

    How to measure voltage produced by magnets

    Don't you love it when a poster continues to prove himself wrong, but insists on doing it his way instead of following advice from people who actually know something? Bob
  3. BobK

    Understanding the nature of the electric field

    Yes, we won't even talk about strings. Bob
  4. BobK

    Where to Purchase Transformers

    You are not likely to find such a transformer because there would be almost no demand for it. What do you need it for? Maybe there is a better solution (DC-DC converter?) Bob
  5. BobK

    Understanding the nature of the electric field

    The electric field is a mathematical construct that has no real existence. All of the interactions attributed to the electric field (and magnetic field) are actually caused by exchange of particles called virtual photons. Bob
  6. BobK

    DC-DC Boost Converter!!! Need Help

    Then why not ask the person who posted the video? Bob
  7. BobK

    "Eh, I just had it laying around" How to know if it's okay?

    Or simply replace the LM317 part of the circuit with your 7805 circuit. Bob
  8. BobK

    Small Circuit needed for New Product Design - Help!

    Okay. So it is like keeping score. Have you picked out an LCD display? Typically these need a separate controller. You can get PIC microcontrollers with LCD controller built in. By the way, this is not a simple circuit. Edit: After more research, any micro with enough pins can operate...
  9. BobK

    Small Circuit needed for New Product Design - Help!

    How does your numeric display show which switch has been pressed and how many times? What if both switches have been pressed a different number of times? I expect what you actually want is an up / down counter, i.e. one switch counts up and the other counts down, is that correct? If so...
  10. BobK

    Custom PCB

    OshPark will give you 3 boards 2x2 in for $20. The boards are excellent quality 2 sided with silk-screen and solder mask. Edit: It looks like Olivier has me beat! Is that really $10 for 5 boards, or $10 each for 5 boards? Bob
  11. BobK

    Which MC should I get?

    You have not answered my questions. Bob
  12. BobK

    how to achieve desired delay time in cmos inverter

    This is where I am having a problem. Bob
  13. BobK

    Source/sink

    Yes, like dave said. And 1uF is probably too big. 0.1uF would be better. Bob
  14. BobK

    how to achieve desired delay time in cmos inverter

    Except that it wont be inverted. I think he is asking not asking about using existing logic chips, but rather about design logic chips that would have that gate delay. Bob
  15. BobK

    Source/sink

    The capacitor should be from the A/D input to ground. Bob
  16. BobK

    Which MC should I get?

    How big an MP3 file? Some microcontrollers come with as much as 256KB of program memory, which can be used to store static data. You can also get external flash chips that interface via SPI which could hold your .MP3 and would be simpler than using an SD card. Also, what do you want to do...
  17. BobK

    Remote Control Circuit with CD4017 - counter decoder

    Stripboard is hard to get right. You should recheck to make sure there are no extraneous connections. It is easy to miss a cut. Check each strip to make sure all the things connected into it should be. Bob
  18. BobK

    help needed for engineering college project

    As Kris already said, the current in the transformer primary is not limited by the resistance of the coil, but by the inductance. If you read otherwise, it was wrong, which is probably why you cannot find it now. Bob
  19. BobK

    Op Amp for speaker circuit

    After seeing the chip Steve linked to, I would go with that. It will be twice as efficient and put out more power. I would use 4 NiMH rechargeable cells to power it. The prices for the ones you linked are very high. On Mouser it is $1.02 for the LM386-4 single quantity. Bob
  20. BobK

    Using Ardunio and MOSFET to drive 5V to 12V

    Well, you have been given a perfectly good circuit in another forum. Why don't you try it? Bob
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