So, I bought a few of these things to play around with/use some day. The cost was cheap, $11 for 10 of them, so I don't mind blowing up a couple.
The input voltage is 4V-35V and the output voltage is 1.23V-30V, so I set my supply to 12 volts and connected it to the input side and connected my multimeter across the output side. I got pretty much the same voltage as the input voltage, ever so slightly lower. I tried twiddling the adjustment pot to no effect.
Should I have a load to get a different voltage across output? I don't think so, but wanted to ask just in case. Does hooking this kind of converter up with no load damage it? Could it just be bad out of the bag? The latter wouldn't surprise me, it's a cheapo straight from China. :-)
I included a picture of the module and a picture of the "specs" for convenience.
Is the listed 92% efficiency pretty decent? It says "highest" in quotes because it will vary, I assume the efficiency will drop the greater the difference is between the input voltage and the output voltage?
I read the wikipedia article on a buck converter, but I'm still not sure what makes a buck converter a buck converter. Is it because it's a DC to DC converter? Or is it due to the topology of the circuit?
Thanks for any insight anyone may provide.