Bench Power Supply

A bench power supply is not a need for the average model railroader. For someone who likes to do electronic experimentation it is a necessity. I’ve wanted one for a long time but they are expensive. Looking around for DIY solutions, I came upon the DROK 250W Digital Controller Buck Adjustable Voltage Regulator DC 6~55V to 0~50V 5A Power Supply Module/Adapter + Digital Meter.

WOW, that’s a mouthful.

Simply put you put in 6 to 55 volts DC and the unit will give you a variable output from 0 to 50 volts at up to 5 amps. It features a constant current or voltage setting and the display tells you the voltage and current. For model railroad use, this is a great way to check the current draw of a motor in a locomotive as it will keep the voltage at a solid 12v and display how much current is being drawn. This is essential in DCC decoder selection. 

For the supply voltage I picked up a cheap switching power supply 48V 5A. This was the “sweet spot” in price for supplies. Anything higher voltage was quite a bit more expensive. 

Getting the parts. The DROK unit is available on eBay, Amazon and a variety of other vendors. It is from China. I got mine on Amazon for just under $40 (CAD). The switching power supply I got off eBay (from China) for just over $40 (CAD) so I have $80 invested. A bench power supply can cost much much more but a decent, inexpensive one is $359.95 CAD From Sayal Electronics in Toronto. 

Of course, I bought the raw parts. It needed an enclosure. That’s where the fun is! I made a simply box from scrap in the garage. 1/2″ ply for the base and 3/16″ ply for the sides and top. I used my dremel to cut out the openings for the DROK unit and a rocker switch for AC power. One precaution, the switching power supply needs 120v AC input. If you are uncomfortable with this, DO NOT PROCEED. I also added a small AC transformer from a wall wart to power the LED power on indicator and run a small DC fan to keep everything cool. The pictures tell the story pretty well. I’ve also included a schematic. Any questions, email me at


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