Bench Power Supply

As a home brewer a flexible power supply is an important piece of gear. Commercial made multi-voltage supplies can be very expensive. There are plenty of designs using an old PC power supply, and they mostly fit the bill, but I had some other ideas. I really wanted something more like adding a variable voltage supply with voltage and current metering, and including -5v and 9v voltages. Most PC supplies made within the past 4 or 5 years no longer have -5v, so an appropriate DC-DC converter is required. For this project, I haven't started researching which converter to use but adding a 9v regulator to the project is rather easy.

I set out to design a very flexible supply using as much recycled parts as possible. The only purchased parts were the case, banana jacks, and the fuse holders. Everything else was scrounged.

Bench Supply Internal Wiring
Internal View

I used a large case for this project. I wanted to have enough room for future expansion and ease of assembly. The ATX power supply is a 500 watt ASUS pulled from one of my kid's desktop PCs. I cut the back panels using an ATX template so the supply could be properly screwed in and didn't interfere with cooling. The right front panel of the case has the main voltages of the supply, the left side of the case has the voltage & current metering with associated individual 5v power supplies for each meter, and 9v and variable voltage regulators.

Meter Power Supplies

A close up of the of the left side of the case. Starting on the left, these are 5v power supplies repurposed from USB wall chargers. They are hot-glued down to a sheet of plastic and the fat black wiring is the AC connected to the backside of the AC connector inside the ATX supply. Both meters require separate power supplies independant of the of the voltage being measured. This means I couldn't use the +5v output from the ATX supply.

At the top of the perfboard is the variable voltage regulator, with the 9v at the bottom. The blue component is a 12v double-pole double-pole relay that's used to disconnect the power going to the meters.

Power Supply Panel Connections

This is a close-up of the right side of the front panel that has all the standard voltages from the ATX supply. In the center of the photo, is the +9v@1A output. I used several of the +5/+12 volt in case there was a need for higher current on for those voltages.

Back Panel

Here's the back of the supply. Nice and clean, with room on the left for additional voltage outputs. I've thought about using it to power other test equipment.

Power Supply Front Panel

The completed front panel with my usual utilitarian looking, yet functional design. The meters were my second attempt at installing them. I first tried a pair of el-cheapo DMMs and used some solder blobs in place of the selector knob. That approach didn't work very well so digging around in my junk box, I found these Simpson M315 digital meters. Trying to straighten out them out was like trying to level a three-legged stool. So, I got them as even as possible and left it as that. The entire cost was around $50, including the case.

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Mark Schoonover,
Nov 12, 2012, 8:48 AM
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Mark Schoonover,
Nov 12, 2012, 8:48 AM