Sunday, April 6, 2014

Bench Variable Power Supply

I have been wishing for a bench power supply for quite some time. Part of the problem is you need one to be able to make one. So I decided to cheat and make one the easy way. It is also the proper size for my limited work area.

I still intend to make a proper one with current limiting and a few more amps, but this will  help in  the mean time.
Variable 1.5 to 30V 3 amp supply, No current limiting. Driving a drill spindle.

The local electronics parts house stocks a few of the popular Chinese modules. So I bought a box and some modules:

The layout. Amp meter requires separate supply.

The modules from top to bottom:
Digital DC Voltmeter 2.5-30V red
DC AMP METER DC 0-10A 2.5-30V
DPDT switch for input and battery on/off
LM317 based variable supply 
  Voltage Regulator AC/DC 1.25-37V max 2.2A
  overload and short protected
Banana plugs and 9v battery
not shown 19V DC old laptop supply

Links to similar:
http://www.tinydeal.com/yb27-dc-33-30v-led-digital-voltmeter-led-car-voltmeter-p-105975.html

http://www.tinydeal.com/yb27va-2-in-1-dc-0-100v-10a-led-digital-voltmeter-ammeter-p-107011.html

http://www.aliexpress.com/item/1pc-new-AC-DC-to-DC-LM317-power-Continuous-adjustable-Voltage-regulator-With-protection-free-shipping/1121236182.html

http://www.aliexpress.com/item/electric-tools12V-24V-Mini-PCB-Drill-Press-mini-saws-burnishing-chuck-Electric-drill-bits-0-6/1115717842.html

While looking for the sample link for the mini drill I saw many like I wish I had found! This one will drill holes in PCB but the runout is to big for milling and the collet is real trash. A 0.8mm drill bit fits with considerable force.