pwm for a boost converter

Ditto. Those 555 circuits are like using a crescent wrench instead of a socket. Eh, maybe pliers instead of a socket.

C1 smaller (than shown), and the pot smaller (maybe 10k).

500pF is a little on the low side for a 555 but will still work. I think 20kHz is about right for that (or 0.005uF with a 10k pot).

I heartily recommend an UC3844 or similar chip for doing a boost converter. The current protection will keep your transistor from exploding, a notable advantage.

I was messing around with a BS boost circuit (two comparators and an op-amp, plus the obvious hardware) just tonight and popped two power transistors. :( Car batteries can sink a lot of current...

Tim

-- Deep Fryer: A very philosophical monk. Website @

^^^^^^^^^^^^^^^ AKA "adjustable nut-fucker"

Cheers Terry

Left or right handed?

dunno

what do you think?

martin

Heh, I realize that those are useless distinctions which can actually apply -- the only chiral part is the adjustment screw, while the wrench length is measured in perhaps 8" or 200mm.

Now, a bucket of vacuum...

Tim

-- Deep Fryer: A very philosophical monk. Website @

That's not a very good general-purpose power supply, as others have noted. Why not use one from my pal Bill Bowden?

Be sure and use a suitable (fast) rectifier, like a 1n5819 schottky, or a fast-recovery type.

Best, James Arthur