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  1. Old Steve

    Beginner ... ferrite core coil for crystal set

    Errol, here's another source of pre-wound coils. I haven't checked out postage details:- http://www.angelfire.com/electronic2/index1/loopstick.html
  2. Old Steve

    Need help on servo motor output gear sizing

    I think that sanyibacsi is actually after output shaft specs, not torque. ie Diameter, # of splines, depth and angle of splines. I did a bit of a search earlier, and found that the number, depth and angles of splines vary model to model and manufacturer to manufacturer. (And I always thought...
  3. Old Steve

    Drill bits for homemade PCBs?

    hevans, I bought some eBay "carbide" bits some time ago, too. No chance of breaking these babies - they're so soft they bend. :D The only use I found for them was cleaning the holes after drilling if they were blocked by swarf. I hope your's are better.
  4. Old Steve

    Drill bits for homemade PCBs?

    And everyone beat me. :D I'm with Bob. Except I don't use my Dremel - it's a bit heavy and bulky. I bought a mini version, 12V 1A. Much easier to manoeuvre.( I drill by hand, too, not with a drill press.):- And I find that HSS drill bits, especially the cheap ones, wear out way too fast, so...
  5. Old Steve

    Help with open collector output

    Like Alec, I'm puzzled as to why there's only 3V between +V and output when it's on. If your 9V battery is connected between +V and ground, then when it turns on you should be seeing virtually the full 9V between +V and the output terminal, with an open-collector output. (Actually open-drain, if...
  6. Old Steve

    Beginner ... ferrite core coil for crystal set

    Errol, the second winding will be fine on top of the first, without additional insulation. I suspected that they might want a ridiculous amount for postage. And I'm sorry, but I have no idea how many turns to suggest for either winding. I've never built a crystal radio.
  7. Old Steve

    Beginner ... ferrite core coil for crystal set

    I think the separate strip of cardboard is just there as a means of anchoring the wire ends. Ordinarily, the second winding would be wound over the top of the first, or sometimes beside it. And there would be no direct electrical connection between the coils. Do you have any instructions, or do...
  8. Old Steve

    motor driver 12v .. 2a... fail~

    The mA range uses a separate fuse. (At least it does on the model I showed.)
  9. Old Steve

    Testing a NPN Darlington Transistor

    I was going to add that a C-E test in both directions was a good idea. And note my weasel-words- I didn't say "there is a reverse diode". Instead I quoted you. :D
  10. Old Steve

    motor driver 12v .. 2a... fail~

    Like this:-
  11. Old Steve

    motor driver 12v .. 2a... fail~

    Are you setting it to the current setting? And are the leads in the correct multimeter jacks for current measurement?
  12. Old Steve

    Linker files

    How did you go? Find the problem?
  13. Old Steve

    Testing a NPN Darlington Transistor

    ModemHead said that there is a reverse diode.
  14. Old Steve

    Help in converting a wireless doorbell into a remote gate switch

    elvislives, what voltage does the gate opener need the pulse to be? Is it a 5V circuit, or higher?
  15. Old Steve

    Help in converting a wireless doorbell into a remote gate switch

    That makes sense. I was thinking more of taking the output pulse from the RF module, but your method should work. Either will provide a short pulse.
  16. Old Steve

    Help in converting a wireless doorbell into a remote gate switch

    That won't be easy simply from the photo you provided. What are the chips? You need to let us know what the markings are on each of the three individual chips shown, for starters. I suspect that the DT connection on the receiver module might be the key.
  17. Old Steve

    Testing a NPN Darlington Transistor

    Just in case it does turn out to be bad, MJE5740 or MJE5742 are recommended replacements, according to this:- http://www.hondashadow.net/forum/908215-post12.html
  18. Old Steve

    motor driver 12v .. 2a... fail~

    Buy something like this is best. A switching power supply. Much more sensible for what you want:- http://www.dealsmachine.com/best_256159.html?currency=AUD&gclid=CjwKEAjwp56wBRDThOSZ3vqGzmESJABjNaj9VCiIDb6bkYZKhd2B1k7XOrCE5CU0PgxfvhQfhcBsFxoCnmTw_wcB
  19. Old Steve

    motor driver 12v .. 2a... fail~

    Just measure across from collector to emitter and see if it's short-circuited. That LM317 is fine - the problem is that you're trying to dissipate too much power. Bad circuit design. I've answered enough questions on this. Go and buy a DC-DC converter.
  20. Old Steve

    motor driver 12v .. 2a... fail~

    No, I didn't say that. I said "Usually, transistors fail open-circuit" . Nothing more. Now that you mention it, though, it is a distinct possibility that something is connected wrongly, if the voltage goes up to 24V. Measure the transistor and see if it is short-circuited internally first...
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