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  1. Alec_t

    Help with solid state relays

    So do you need a 2P3T switch? Does this help?
  2. Alec_t

    CD 4047 inverter

    The lowest oscillation frequency your circuit will produce, according to a Spice simulation, is about 90Hz. There will be some shoot-through, so the FETs are likely to overheat. I think that poor little 3VA transformer will probably saturate, as duke says.
  3. Alec_t

    SMPS Troubles

    It happens because the 20uH value is too small. The current in the primary does ramp up, but with such a low inductance that ramp occurs in the first microsecond or so of the 'on' pulse. (Zoom in on the waveform to see). For the remainder of the pulse the current is limited only by the inherent...
  4. Alec_t

    Help with solid state relays

    :confused: That equates to permanently on: so why do you need a switch at all? Perhaps what you want is a SP3T switch?
  5. Alec_t

    How to improve upon this comparator driven LED circuit?

    Oops, forgot that. A 1k resistor directly across the green LED in the post #10 circuit should do the job.
  6. Alec_t

    Mosfet / Gate drive problems

    File too big? Keep it below 500k (take pity on folk with limited/poor broadband ;)). Wrong format? Use PNG or GIF or JPG.
  7. Alec_t

    Replacing a faulty SMPS

    Well, you won't need four regulators: two will suffice. I think you could go with the +5 and the -12 wired as you're suggesting. Alternatively, if you choose to go with the +12 and +5 you should be ok if they're wired similarly to the diagram in post #23. Fingers crossed!
  8. Alec_t

    Replacing a faulty SMPS

    That's precisely what the original Whirlpool circuit does, and why the TS is concerned ;).
  9. Alec_t

    What Is This

    It could be an embedded control chip.
  10. Alec_t

    Oscillating pulse to stable

    Ground the Reset pin (4).
  11. Alec_t

    Successful monitor repair

    Good one. Always nice to hear a success story :).
  12. Alec_t

    EGR Emulator Circuit

    I think there's more to it than simply using a coil or resistor. If I understand the other thread's OBD graphs correctly (that's a big IF, since I've no experience with OBD :)), the second graph relates to the EGR position sensor; so wouldn't you also need to emulate that sensor to keep the ECU...
  13. Alec_t

    Replacing a faulty SMPS

    When it comes to mounting your components in the machine, remember that ALL parts of your added circuit should be treated as HOT/LIVE and housed in an insulated, ventilated enclosure accordingly.
  14. Alec_t

    Gate automation system - Motors open but do not close.

    Relays may look ok, but if the contacts are burnt/welded you will have problems. Can you check that the contacts open/close as they should? My only suggestion would be to replace the ULN2003, but of course there's no guarantee that will fix things.
  15. Alec_t

    Paddle mixer speed controller

    Looks a likely circuit. D1 is a diac. C1 is a 0.1uF non-polarised cap.
  16. Alec_t

    Replacing a faulty SMPS

    The linear regs should do the job. Good luck.
  17. Alec_t

    Need help to create safety device which will stop window blind going down if something is in the way

    IdmountabaralongthebottomedgeoftheblindwitheachendofthebarsupportedbyarespectivemicroswitchwelcometoEPpleaseuseproperpunctuationinanyfurtherposts
  18. Alec_t

    SMPS Troubles

    Your L1 value is rather low for the frequency you're generating and that may be causing the ringing you see, via capacitive feedback to the gate. You need a back-emf protection diode across L1 to kill the voltage spike. The output needs a cap to stabilise the voltage. Try this mod: The asc file...
  19. Alec_t

    IR carrier frequency

    If by 'carrier' he means the IR itself then yes. There's been no mention of anything else, e.g.a 38kHz modulation, itself pulsed.
  20. Alec_t

    Replacing a faulty SMPS

    If it were me I'd probably buy a couple of generic off-the-shelf SMPS supplies (one +5V, one +12V) and wire them like this :-
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