Lasersaber strikes again. A joule thief king ?

[TinselKoala]

Congratulations! Soon you will have invented the Joule Slayer.

Meanwhile, I've been working with LS's most recent circuit and I have some interesting things to demonstrate, which I should be able to show in a video later on this evening.

I am using a Loopstick variable inductor with two extra windings. The normal Loopstick winding consists of two nice herringbone-winding Litz wire coils in series, and the inductor's range is about 2 mH to about 9 mH. Probably 300 turns total. I added one coil by winding 20 turns of heavy magnet wire over these coils and potted in epoxy. Then I wound another 100 turns or so on top of that with #30 magnet wire and covered the whole winding with heatshrink to hold it in place. So there are three coils total, and the ferrite slug that varies inductance and coupling.

I'm using the MPSA18 transistor, and a 1F capacitor, and a 10 Meg (or 5 Meg) resistor, the special loopstick, and 3 LEDs in series: R, G and B. The main Litz windings of the loopstick are on the LED side of the Lasersaber schematic. I can confirm that the current drain is very low and it runs in what I call "basic" or dim mode for a long long time.

But.... there is another mode, made available by the extra winding on the loopstick wired in an unexpected way.... stay tuned for the video...

[d3x0r]

I got mpsa18's today; they look almost the same as the NTE47's ... but the NTE47 is slightly lower frequency (slightly higher resistance?)  ... slightly being maybe 10% but that's only a guess...

my 1000uF caps were only 5.6V *no wonder it popped at 16V* 
... probably pretty leaky at 9V too

*looks forward to TK's loopstick JT*

http://www.mouser.com/Search/ProductDetail.aspx?R=MPSA18RLRMGvirtualkey58410000virtualkey863-MPSA18RLRMG

RLRMG?
the pdf says -D on title; but inside are no suffix letters....

[TinselKoala]

No doubt the NTE part is quite a bit more expensive !

My MPSA18s appear to be manufactured by Fairchild, and the MPSA18 data sheet I have is from Motorola. Heh....

I've learned over the years that transistor substitution is only rarely critical. Match material, polarity, max voltages/currents and power dissipation first, then Hfe/gain/speed, etc.

I've also found, down in this range, that the BC337-25 is almost like the MPSA18 and in some circuits may be superior.

(Thanks to DarkAlchemist)

[d3x0r]

No doubt the NTE part is quite a bit more expensive !

My MPSA18s appear to be manufactured by Fairchild, and the MPSA18 data sheet I have is from Motorola. Heh....

I've learned over the years that transistor substitution is only rarely critical. Match material, polarity, max voltages/currents and power dissipation first, then Hfe/gain/speed, etc.

I've also found, down in this range, that the BC337-25 is almost like the MPSA18 and in some circuits may be superior.

(Thanks to DarkAlchemist)

well 99 cents with instant gratification (can go down to store); vs 40 cents in low quantities ... and 2000 for $120 (6 cents)
and radio shack carries nte parts...


I think I broke a mpsa18; I have it now at 1us pulses... but are negative emitter  driven.... it generates more light at the cost of a lot more amps... and now when I back up to the simple circuit it's doing the same thing... can get down to 10mA but that's pretty high... at one point I shorted a diode to ground... think maybe it's a common collector oscillator now

[TinselKoala]

Don't throw it away... I have a "broken" 2n2222a that does some interesting things...

But meanwhile the Loopstick meets LS Looper video demo is done. The change in brightness in the LEDs doesn't show up so well on the video but I hope you can at least tell a bit of what's going on.


http://www.youtube.com/watch?v=eqBK00tuI8Y