Tuesday, 16 August 2016

Variable voltage DC power supply

Finished making a little case (well a front and a back!) for this variable power supply that I had worked out and wired up a while back and then had on the (enormous) to do pile! I finally got round to drawing a bit of cad and I cnc routed these panels. The panels are just 4mm mdf with a bit of spraypaint to finish them. The gubbins comprises of a very cheap variable voltage dc-dc board which is a lm2596. They come with a small ceramic pot on the board to vary the voltage but I've replaced that eventually with a 10 turn pot to give me the resolution I need to set the voltage to 2 decimal places! (I say eventually, in testing I used an ordinary pot which proved the concept but was difficult to even hit a value to the nearest volt!!)
 These variable buck dc-dc boards take a voltage input of anything between 4v and 35v and will output a voltage range between 1.23-30v, they seem pretty stable. The display is a 3 digit voltage display like THIS, It is important you get one that is listed as having 3 wires, namely then it takes its power supply from the input voltage and has a third wire connected to measure the output voltage.. there are some that only have 2 wires that just connect across the output voltage which means when the voltage drops below around 3.3v.... they turn off! The 3 wire ones happy measure down to the minimum values. (note neither of the links are traders I've used.. rather just to show the stuff!)

The back panel has the inputs on the right and the outputs on the left all on 4mm banana jacks... I love cnc routing.. it makes you able to get these things really precise.. If I had had to drill those holes manually I would have designed it with more space between them making the entire thing bigger!

Anyway.... nice to finish one thing off the pile!

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