Re: this schematic:
If I change C1 to 500 pF, would I get a 20 kHz PWM frequency?
Would any other modifications be necessary to achieve 20 kHz?
I'm trying to build a boost converter, and I'd like to use a variation on this circuit to perform the switching.
Thanks,
Michael
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-f***er"
Cheers Terry
Left or right handed?
dunno
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
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