2012/01/092012/03/14 By admin In Electronics, Joule Thief SMPS DC-DC, Meters and Test Equipment 2012-01-08 DSO Waveform across Joule Thief LED Here’s a screenshot of my DSO with the scope probes across the LED. The pic on the bottom is the actual Joule Thief. The capacitor that is half hidden at the bottom is a 10 uF bypass capacitor.