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gEcky

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Everything posted by gEcky

  1. Hi! Thanks for the prompt reply! Does that mean that the blown switch should be a one time thing? The transformer i used is a center-tapped +/- 24V at 1A. The dilemma is that if I put the LED jus after the rectifier, a large resistor with high power rating may be required to protect theLED (I still have little clue to calculating R values for LEDs. I always use 220R for 5v suppplies ;D). If i put the LED after the regulators, the LED prob will not light when the regulated voltage is below, say, 3v. (I mainly work with PICs and recently got a 3v RF transmitter so i need voltages at ~3+,5,9,12++ :) ) I'm jus afraid that i might leave the PSU on if there is no indication, besides the switch position, that the thing is still on. :) The bad experience I had with the blown rocker switch that had a neon lamp didn't help either.
  2. Thanks! there is no short between the 2 coils..... i think i'm not suppose to use the 2 pairs of lugs the way i did... Means i can only connect the "live" or "neutral" and not use both to open/close the circuit. Another thing, at which point will it be good to place a LED to indicate power on?
  3. Hi I'm constructing a PSU, stepping down 230Vac to 24Vac via a transformer. The power to the transformer is connected via a rocker switch rated at 230V-16Amp. It's a DPDT i suppose since it has 4 lugs and forms 2 isolated pairs. So I connected the AC "live" and "neutral" on each side of the switch with the transformer inputs at the opposite side. The circuit will thus be complete when the switch is on. The circuit worked fine and i was able to on/off the PSU without leaving it on for more than a while to check the regulayed ouyput voltage. However when i left the PSU on for about a minute, the neon lamp of the switch blew. So did the fuse in included in the circuit, fortunately. A check with a ohm meter shows that the 2 pairs of lugs on the swith is now shorted! 2 inputs shorted / 2 outputs shorted. Could someone tell me what when wrong? (Transformer is 24Vac-1A and the mains supply is 230Vac-13Amps-50Hz.) Thank you in advance!
  4. Hi I was thinking of building the "laboratory power supply" based on the schematic given in LM317 datasheets. However, I'd like to know what the 2 MOS transistors does. Voltage reference? Thank you in advance!
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