Electronic load with voltage, current meter.

I had bought a cheap, USB plug-able, electronic load which I have used to test some HiMh batteries. The load comes with a USB type A connector but is usable for voltages up to 15 volts. I had just soldered two wires to connect it the batteries and used a handheld multi-meter to control the voltage. It did the job but was not the best way, so I bought an electrical parameter tester which measures the voltage, current and power consumed and displays them on an O-LED display. All I had to do is to stick those two modules in an enclosure so it is more usable and reliable.

Putting those things together was a matter of drilling some holes and some filing. First applied some masking tape so I could mark the hole centers easier.

then drill them out and cut the rectangular opening for the meter using an knife.

File the rectangular opening until the bezel fits and stick it in there. Next attach the electronic load using the screws that hold it’s fan to the heat sink.

I have removed the potentiometer used to adjust the load’s current and mounter it with some wires so that the axle pokes through one of the holes in the front of the enclosure. I made a bracket, out of three pieces of prototyping PCB, to attach the potentiometer.

It is done. Here it is used to load a one cell power bank.

I had initially wired the thing in such a way that the meter is powered by the banana jacks, but then I decided to add a separate power input for it. It is true that the consumption is very small, some 10 to 15 mA, but it is not shown on the display, so in situations where the used load current is not very high this might introduce significant error. I used a mini USB break-out board. I had to modify it slightly so that the face of the mini USB socket sits flush with that enclosure wall at the end.

Just cut out the bit of the PCB which is under the front end ot the socket.

Then glue the thing in the enclosure and solder two more wires.

Other things that I would do differently is to mount a switch and another banana jack so I can disconnect the load and use the meter with some external load. Maybe 3D print a better looking grill for the ventilation holes.

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