Power Supply/Transformer Design - RF Cafe Forums
Post subject: Power supply/Transformer design.
postPosted: Fri Apr 22, 2005 12:39 am
Joined: Fri Apr 22, 2005 12:22 am
was an electronics engineer, one of his creations being a clock.
I know the clock needs about 10 or 11 volts AC, and I believe at
60 hz. After a while this transformer gets really hot, I don't know
if it doesn't have enough Amps or just because it is small and in
a closed case. The power supply for it was cracked in half and thrown
out a while ago. Currently I am running it off an AT&T Answering
Machine adapter I found at RadioShack. That gives out about 10 volts
AC, and 800 mA. I am not sure of the frequency. The rectifier is
on the clock itself, because it uses the AC frequency as pulses
to increment the time, then the rest of it works off DC. Long story
short, I was wondering how I could design a new power supply, I
am not really that good with electronics. I can do it if I had schematics,
but I can't make my own, I don't know what parts to use. Are there
general design rules to follow to design power supply/transformers?
Or is each one especially unique? I may have to play around to get
the voltage/amps/frequency just right. Thanks for any help. If there
is any other information I could try to find to make it easier let
me know. I've tried different kinds of transformers, if I use DC
the clock can't count, and it worked with 20 VAC but the DC part
of the clock is regulated by a 5 volt regulator, which overheats
within an hour and shuts off. The rectifier is 200 PIV. I don't
know what other random information you would need. I think I may
be able to go even lower than 10 volts, but sometimes the audio
part seems to struggle at the lower voltage, I think its safest
to stay at 10.
Thanks for any help.
Post subject: Power Supply
Sun May 01, 2005 11:05 pm
It sounds like the clock already
HAS a power supply, minus the transformer.
So it sounds like
all you need is a transformer with enough current capability.
A "wall wart" type of transformer is usually bit wimpy. Try
a 12V 2 A transformer, rated at 120V in for 60 Hz operation. These
are pretty standard items, and you can get them from mail-order/web
stores like Electronic Goldmine, MPJA, etc., or from industrial
distributors (try DigiKey or Mouser - most of the others have minimum
order requirements), or possibly even Radio Shack.
don't change the frequency of the applied power, but the efficiency
of the transformer changes with frequency - that's why they have
a frequency specification.
There are lots of transformers
available for purchase, I don't think you want to consider making