Shawn said:
Im looking to build a few power supplies that are able to put out 12vDC
at 2amps from a standard wall outlet (N.A 110vAC). I need 3 12v/2amps
power supplies to run three stepper motors. Any ideas or help would be
great.
thanks
If you are SURE you need only 2 amps, read on.
Below I describe building a 3 amp supply, or buying
one. Building a 2 amp supply would cost you only
a dollar less, not worth the savings.
Allelectronics sells a 3 amp 12 volt ac transformer
for $6.00 each. Catalog part number is CAT# TX-123
http://www.allelectronics.com/
Add a diode bridge rectifier (CAT# FWB-604) at 2 for $1.00,
a couple of filter caps in parallel) catalog # 4700/25VR
at $1.25 each and an LM350T regulator CAT# LM350T at $3.50
plus a couple of resistors and a diode, and you're done.
See the schematic at (watch the wrap):
http://ourworld.compuserve.com/homepages/Bill_Bowden/page12.htm#317.gif
or Google on Bowden Hobby Circuits and click on
LM317 Variable Voltage Regulator. The LM317 is replaced
by the LM350T, which is a 3 amp regulator - the LM317 is
good for only 1.5 amps. I don't think you need the 22000 uf
cap - I'm betting the 2 4700's will be plenty.
You will need to heat sink the LM350T. Worst case, it will
dissipate about 10 watts, but with intermittent duty a small
sink will do - you can make on out of a small piece of
aluminum, say 2" x 2". (Bigger is better.)
The price tag per supply comes to $12.50, not including the
resistors, diode, enclosure, hardware, line cord etc.
Or you can buy CAT# PS-1242 for $18.00 - its a regulated
3.5 amp 12 v supply. That's probably cheaper.