Joule Thief: Tinman’s Circuit w/ Tesla Bifilar Coil, DMM Current Measurements
I’m putting this in the Joule Thief category for now. Tinman’s circuit shows some very interesting behaviour. These white LEDs are absolutely the brightest I have ever seen, without blowing. They hurt my eyes to look at them when they are fully on. I’m driving the system at somewhat over 1 MHz with a symmetrical (positive and negative) square wave of 50 percent duty cycle.
The brightness of the LEDs goes up with applied voltage, just as you would expect, but the DMM current readings go _down_ with increasing output amplitude from the Interstate F43 FG.
I am using 2 “elcheepo” DMMs from Harbor Freight, both as ammeters, one on each leg of the FG’s input to the TinMan board. By careful selection of frequency and voltage output I can make the meters read _ZERO_ current, even in the 2000 microamp range…. and yet the LEDs are still quite bright. Also, at some frequency/voltage combinations the currents on the two supply legs are unequal.
I’m not scoping the circuit directly here in this video because there is some interaction between the grounds of the FG and the scopes, even when I have the FG set to full isolation (Black output not grounded to chassis). Later on tonight or tomorrow I’ll shoot another video showing the scope traces.
ETA: The capacitors called for in TM’s original are 2200 uF and 150 uF…. I made the larger one out of two, 1000 uF and one 220 uF in parallel, and I made the smaller one from one 100 uF and one 47 uF in parallel. So I have 2220 uF and 147 uF….. with 20 percent tolerance of course. 😉