El cheapo joule thief setup, with a spare blue LED, a ferrit from
an old mainboard coiled with a pair ripped of a 80 pin ide cable
(be lucky - one has a colored stripe, 39 other pairs not ;-)
here three dso pics with a battery voltage at about 1.2 volt (bright light), 0.6 volt (still lighting) and 0.5 volt (no light):
at about 1.2 volt we have about 35 khz: (please click to enlarge)
at 0.6 volt or so its about 140 khz: (please click to enlarge)
and with 0.5 volt there is no light, but it is still oscillating at 200 khz: (please click to enlarge)
about 2.6 volt peaks are left for the led - not enough...
see the dso 2090 at conrad.de (german site).
• back to bertnase.de