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  1. CDRIVE

    A means of closing a JFET switch with a postive voltage?

    OK, I feel like I'm shoveling sh!t against the tide. The 9V battery limitation of this project leaves zero overhead to play with. It presented issues in your first topic, which is really the starting line of this topic. This has been a royal PITA right out of the gate... Pun? As I stated earlier...
  2. CDRIVE

    A means of closing a JFET switch with a postive voltage?

    Damn! ASDR Envelope.. I had to Google it. Interesting! ;) Chris
  3. CDRIVE

    A means of closing a JFET switch with a postive voltage?

    OK, I've spent a few hours simulating S&H circuits using BJTs, JFETs, MOSFETs, and chips for the Sampling Switch elements, using 9V as my supply restraint. Each circuit produced varying results from Switch OFF State leakage to not being able to charge the cap to the full 9V. May I ask why you...
  4. CDRIVE

    A means of closing a JFET switch with a postive voltage?

    I'd prefer to save myself the effort of sifting out an applicable Schottky. Perhaps another member has some suggestions? Chris
  5. CDRIVE

    A means of closing a JFET switch with a postive voltage?

    Once again you failed to divulge vital information. Do you remember My Rant way back in your original topic? :mad: Speaking of which,.. your decision to create multiple topics (3) that are actually the same topic isn't helping matters either. I just wasted a considerable amount of time tunneling...
  6. CDRIVE

    A means of closing a JFET switch with a postive voltage?

    Actually I'd rather not see any more schematics of what you're going to add or modify in the existing keyboard. What I'd like to see is the manufacturer's schematic. If that's not possible then a webpage with a sales description of it. Maybe some good photos might help. For the last time...
  7. CDRIVE

    A means of closing a JFET switch with a postive voltage?

    I need to find my roll of extra heavy duty duct tape. I'm going to wrap my head with it to keep it from exploding! In your last post I thought we had agreed that the pots and keys could not be wired like that. I read your reply as confirmation that the way I drew them is the way they're wired...
  8. CDRIVE

    A means of closing a JFET switch with a postive voltage?

    We have quite a few very knowledgeable and experienced members but like me they have their "Duh" moments. My guess is that this discrepancy wasn't caught do to the "It's 5 O' Clock Somewhere" factor. :D Regarding your question about using a SSR for the sampling switch: Maybe but I have a few...
  9. CDRIVE

    Voltage divider protected by Zener diode

    If you'd like to bring the clamping voltage a bit closer to your desired 4.2V you can add a 1N4002 Diode in series with the 3V Zener. The clamping voltage will then be ~ 3.7V. Two series Diodes will bring your clamp voltage up to ~4.4V. Chris
  10. CDRIVE

    Will this switch work with what I'm trying to do?

  11. CDRIVE

    A means of closing a JFET switch with a postive voltage?

    This is how I think the keyboard should be wired. In this arrangement the pots are independent of each other unless more than one key is pressed at the same time. Chris
  12. CDRIVE

    A means of closing a JFET switch with a postive voltage?

    I can't move on to discussing solid state switches until I get this nailed down. The way it's wired each pot will effect all the other pots. Are you absolutely positive it's wired like this? In other words if you set any one pot and switch to produce a given voltage and then move on to adjust...
  13. CDRIVE

    A means of closing a JFET switch with a postive voltage?

    You're correct. I didn't understand. So I re - read this thread 3 times to see if I missed a clue. As far as I could see I didn't miss anything that would hint that it's a DC level that's being sampled. One would need to go back to your Will A Basic Buffer Be Sufficient topic in which you posted...
  14. CDRIVE

    A means of closing a JFET switch with a postive voltage?

    Yes but the next time a sample is taken the cap voltage must follow the analog signal. If the signal at that moment is more positive than the previous sample the cap needs to charge more positive. On the other hand if the signal went less positive the cap has to discharge back into the buffer...
  15. CDRIVE

    A means of closing a JFET switch with a postive voltage?

    I think you need to review This Chris
  16. CDRIVE

    A means of closing a JFET switch with a postive voltage?

    If you're saying that your keyboard controls a DG403 then that was a Struther Martin moment. Chris
  17. CDRIVE

    A means of closing a JFET switch with a postive voltage?

    Now I'm really confused. Are you implying that your keyboard keys pass analog signals? Chris
  18. CDRIVE

    A means of closing a JFET switch with a postive voltage?

    Ever hear the expression "That's like comparing Apples & Pears"? Well there's no Pears in this Sample & Hold video but there are Apples. Here's a link to the LF398N that he mentions near the end of the vid. BTW: I was surprised to find quite a few S & H Circuits that employed JFETs but as...
  19. CDRIVE

    A means of closing a JFET switch with a postive voltage?

    I see you're still struggling to keep a negative source out of your project. That 9V battery limitation has been a royal pita. That said I don't understand this statement. You need to elaborate so we can determine whether you should be using a JFET at all. They're not exactly known for being a...
  20. CDRIVE

    looking for a "center-bore" motor

    There are large shaft motors. We had quite a few at the hospital I contracted at. Some as large as 3" but you'll need a crane to move them! :p Chris
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