In this project i am building a basic variable AC&DC power supply. All components in this build are rescued from broken/obsolete parts that would have otherwise gone to the trash.

We begin by emptying out some old machine that the parts will fit nicely in.



Aluminium panels are cut to size to cover the front & back. After the holes are cut in the front panel, it is brushed and painted with black spray paint.

The mains plug with fuse, 3A rectifying bridge and 220/110V transformer are bolted to the back wall.



The 0-120V variable transformer is mounted to the base plate. An oversized capacitor which stabilizes the DC output is also mounted.

2013-2-21



All the instruments and connectors are mounted to the front panel.

Left to right:

– Mains switch

– Ampere indicator

– Voltage indicator

– AC/DC selector switch (only affects what is shown in the meters)

– Output fuse

– +DC

– -DC

– Extension shaft for voltage selector knob

– AC Out



The front panel is mounted to the case and the wires are temporarily connected and basic operation is checked. Since everything seems to be working fine, it is time to finalize the build and solder the circuit board needed for the instrumentation.

2013-2-23



The circuit board was a nightmare to design. I should not have implemented a different scale for the true DC values. The difference is not that big. The down side is that it adds one 12-pin switch and increases the amount of components and logic quite a bit. It fails the KISS principle.



The drain resistors were mounted to the case to free up the area around the DC capacitor’s terminals. All connections are finalized and the instruments calibrated.



First prolonged testing of the unit. With a current of 1.2A @ 115V everything seemes to be working fine.

2013-2-24

After 12 hours of operation at 1.5A @ 100V (150W) the unit has passed quality control, and is declared ready.



The circuit diagram of the power supply. Simplified version with instruments indicating only AC current and voltage can be found here.