Search results

Search Forums New Posts
  1. KrisBlueNZ

    trying to repair excersice bicycle control unit

    Photographs of both sides of the board would be a help
  2. KrisBlueNZ

    JFET Voltage Controlled Switch

    Yes, I think so. Technically the 4066 _is_ digital - at least, it's part of the CMOS 4000 series, which are digital ICs. But I know what you mean. The former. If your signal has only two states, you can amplitude-modulate it by feeding the signal into a transistor in common emitter...
  3. KrisBlueNZ

    Want to build a 2 event delay timer controller

    OK Steve. I'm sorry about the delay. I lost track of this project. This design consists of two monostables (pulse generators) and is built around an NE556, which contains two NE555 timers, probably the most famous IC among hobbyists. The first, on pins 1~6 of the 556, is triggered by the...
  4. KrisBlueNZ

    Capacitor Multipliers in Pulse Generator circuit

    More thoughts. I don't know what you're talking about regarding duty cycle. A monostable simply produces a pulse of settable duration in response to a trigger pulse. Duty cycle applies to an oscillator. You seem to think it relates somehow to the trigger circuit. Please explain what you mean...
  5. KrisBlueNZ

    JFET Voltage Controlled Switch

    OK. I've been playing with LTSpice to test out some ideas too. Its JFET model doesn't seem to be very accurate, and seems to have quite a high Rds(on). I'd be interetsed to know which real-life device they have based it on. But I don't have any models of real-life devices to compare with, or...
  6. KrisBlueNZ

    Capacitor Multipliers in Pulse Generator circuit

    I don't think the monostable will work. At least, I think D1 is backwards. Edit: The monostable doesn't reset the capacitor charge when it expires. If it's retriggered soon after the pulse ends, the next pulse will be much too short. I think you need to tie the monostable in with the...
  7. KrisBlueNZ

    LDO heating up

    Is the battery connected round the right way? Positive to the LDO input? It's drawn backwards on the diagram in your first post. Also do you have the LDO input and output round the right way? If you connect the battery to the output, you will probably damage it. The LDO shown in the second...
  8. KrisBlueNZ

    Want to build a 2 event delay timer controller

    slrphoto, I think you've sent me one or two messages but I can't find them now. I just read one about making the one second time variable because it controls a motor, but I can't find it anywhere now! There's nothing from you in my private messages inbox. Could you please post them here on this...
  9. KrisBlueNZ

    How can the new Yamaha HH65 Hi-Hat Pedals be modified to work with the Yamaha DD-50?

    I'm assuming that we're talking about the cable wiring diagrams from my post #22 on this thread. Both of those cables can be made from a stereo cable with a stereo plug at each end, or a mono plug at the DD-50 end (the DD-50 has a mono socket which doesn't have a ring contact). The original...
  10. KrisBlueNZ

    Capacitor Multipliers in Pulse Generator circuit

    So you need to create a monostable that generates a pulse with an adjustable duration when it's triggered. Then the assignment says that the "duty cycle must be continuously adjustable from 25% to 75%"... Huh?
  11. KrisBlueNZ

    Newbie help with relay card

    Spot on, Harald.
  12. KrisBlueNZ

    OpAmp circuit

    I think the OP wants to divide one voltage by another voltage. That's what Laplace has assumed as well. He has given a good answer.
  13. KrisBlueNZ

    Comparator inputs

    The input to the final comparator is on pin 13 not pin 12. The voltage on pin 13 should follow the LED state but with a delay due to CD being charged and discharged through RD. When the LED is ON, the pin 13 voltage should increase towards 12V (it will never quite reach it though; don't worry...
  14. KrisBlueNZ

    Comparator inputs

    The only simplification I can see would be to remove the two input buffers, but that would necessitate a "firmer" VAR rail. The saving, if any, is not significant. I don't see any way to simplify the rest of the circuit. Actually it's a pretty compact design I think. Does the LED correctly...
  15. KrisBlueNZ

    nimh charger

    Perhaps you can find a charger that supports multiple batteries and will charge them in sequence. If not, you need a way to detect end-of-charge and switch over to the next battery. Luckily with SLA, the charging algorithm is simple and there's no history involved, so a charger can be switched...
  16. KrisBlueNZ

    ad 620 instrumentation amplifier

    I will try one more time to get you to answer some basic questions. 1. Why are you using an AD620 instead of a standard op-amp connected as a non-inverting ampifier? 2. What is your input source? What type of signal? What impedance? 3. Provide a COMPLETE schematic, including details of (a)...
  17. KrisBlueNZ

    JFET Voltage Controlled Switch

    How about posting the full diagrams for two different connections that both don't work. That will give us a starting point.
  18. KrisBlueNZ

    nimh charger

    Temperature affects all batteries, because it affects chemical reactions. I don't know offhand what the requirements are for SLA; it will be described on the manufacturer's data sheet. I know their capacity drops significantly at lower temperatures.
  19. KrisBlueNZ

    JFET Voltage Controlled Switch

    I mean a complete circuit. There's no way to know what the DC voltages on any of the JFET terminals would be when you just draw an abstract diagram like that. Can you draw a complete circuit with an AC-coupled audio input and output and a clear indication of the ON and OFF voltages of the...
  20. KrisBlueNZ

    nimh charger

    Right. NiMH cell temperature should never exceed 50 deg.C, maybe lower (see the cell's data sheet).
Top