Almost a year ago, I purchased a 5 pack of tiny switching bucking supplies. Finally I think I was stable enough to solder some wires onto one and test it out. These supplies can have the output variable, jumpered for 1.8V, 2.5V, 3.3V, 5V, 9V, or 12V. The maximum rated current is 3 amps. The input voltage ranges from 4.5 – 24 volts. Being that this has no boost function, the output can only be below the input.
Here’s a picture of the back of the supply. It arrived set for variable by default. You can change that by cutting the jumper going to the gold ring by the “A” in ADJ. Pick the voltage you want and solder a small bridge between the two pads above the voltage you wish (or set it back to variable). there is a potentiometer on the other side for setting the variable voltage. To the left, the “EN” is the enable input if you want to override the default always on state. Ground it to disable it, apply V+ to enable it, or just let it float.
With the output not used, it exhibits a sawtooth waveform that disappears when a load more than a few milliamps is connected. the remaining noise is reasonably low. Here’s a picture from one of my scopes of the input and output waveforms. the top yellow trace is the output and the bottom blue trace is the input from a programmable bench power supply.
Sorry, I haven’t figured out how to let you enlarge the pictures yet.
The output voltage has held from 10.160-10.163 volts for the last couple of days I have monitored this. I forgot to activate max/min recording for the picture. The supply is running in its default variable mode, and I’m pleased that the potentiometer seems to be good quality.
Varying the input voltage from a few tenths above set voltage to about 20 volts has no effect on the output voltage or the waveform.
You probably can’t see anything worthwhile in this mess of wires and probes, but here’s where the connections are. It’s definitely nothing fancy at all! I guess simplicity rules here.
I’m thinking about using these for my next iteration of outdoor twinkling Christmas lights operating from an Arduino project I put together before being diagnosed with cancer. I have a 20 amp 5V power supply running it all now, but I’m thinking of expanding it and using a higher DC voltage to the remote Arduino controllers I have planned. That way, there will only be one power supply needing 120VAC.
We’ll see if that might rate a post outlining the project. I want to redo the code from ground up in addition to the expanded project.
