Lasersaber strikes again. A joule thief king ?

[SkyWatcher123]

Hi conrad, thanks for informative reply.
Ok, i looked up specs on the mpsa18, didn't see any rise or fall time specs, though i do notice it has much higher gain than the 2n3906.
The mpsa18 says this, this device is designed for low noise, high gain, applications at collector currents of 1ua to 50 ma.
While the 2n3906 says it rated at collector of 10ma to 100ma and its gain is 5 times less.
The 2n3906 rise time is 35ns and fall time is 75ns.
So maybe it has more to do with the mpsa18's gain and lower current operation, being able to suck dry the capacitor of every last bit of juice and the ringing is evident of course and any possible feedback.
I have a few different type of small transistors here, will look up the specs to see if any of them have this high gain, low current ability.
peace love light

[SkyWatcher123]

Well, i don't have any small transistors here with the high gain of the mpsa18.
Though i wonder if using two 2n3906 in a darlington pair might work, though that will slow down the rise and fall time.
Will test it out later today.
peace love light

[d3x0r]

Well, i don't have any small transistors here with the high gain of the mpsa18.
Though i wonder if using two 2n3906 in a darlington pair might work, though that will slow down the rise and fall time.
Will test it out later today.
peace love light

Germainum transistors only had a gain of 2-300.... but they had a really low gate voltage.
These NTE47 transistors have a similar character to mpsa18, but are only 1000 instead of 1500 gain, and I think they switch time is longer; on the order of 20us... waiting on mpsa18 from mouser


I tried searching for transistors with similar character, but cannot find anything with the same gain magnituder with the low base voltage...

[conradelektro]

I just had a total failure with the new windings on my transformer core, see the attached photo for the specs.

I put this coil into LaserSabers latest circuit http://laserhacker.com/?p=420 and it did not work without a resistor between base and positive rail. And with the resistor (1M to 20M) it did not do the very short ringing bursts but the normal JouleThief mode at 14 KHz. The LED was fairly bright but the power consumption was 200 µA to 600 µA depending on supply Voltage.

It seems to be more difficult than I thought to come up with the right transformer.

Greetings, Conrad

[electrospark]

looks like a nice circuit, i'll sure try to make one of those.