Fudge Ripple

That’s the AC ripple from the power supply mentioned here, when connected to a 10 ohm 10% 10W power resistor, sinking ~490mA. The scope is set at 10mV and 5uS per division, probe at 1x, AC mode. In that image it’s being fed about 36VDC. Cutting that in half using only half the power supply (about 18VDC or so) gives this waveform, with marginally less noise.

The way I see that, peak to peak noise is about 50mV, so just about 1%. I think RMS would actually be a good bit lower, but my scope won’t figure that out for me and I think it’d be a lot of work to do it by hand. So, I think this should be an okay design… This is also on a breadboard, and something well laid out actually with a groundplane and all should be even better.

I might head downstairs and pull out the second filter (inductor + capacitor) and see how much more noise it adds, but I’m fairly certain that it’ll be quite substantial.

One thing is for certain, I really could use a better scope. I’m very tempted to just buy a refurb, $547 Tek 1002. However, I think I’d really rather have one of the B models, which adds serial and USB ports for getting data (screenshots, etc) right out of the scope.