Re: Low loss/dissipation xistor or ...
- From: Eeyore <rabbitsfriendsandrelations@xxxxxxxxxxx>
- Date: Sat, 20 Dec 2008 02:01:58 +0000
Bob Engelhardt wrote:
The project:
I am making electrically heated socks & gloves. For power I'm using the
9.6v NiCad batteries from my cordless drill. The working assumption is
that each sock & glove will need 1w, but that's very tentative & I'll
have a regulator to adjust as needed. The critical parameter is the
9w-hr available from a battery before needing to be recharged. So the
regulator must have minimum losses. The 2 socks & the 2 gloves will be
in series & independently regulated.
The current plan is to use a 555 timer for each pair & vary the duty
cycle to achieve regulation. But the 555 can't drive the heaters
directly - they'll require about an amp. I'm thinking of using SMT
BJT's from ON Semi:
http://www.onsemi.com/PowerSolutions/parametrics.do?id=808
because the very low VCEsat (as low as 50mv) will minimize the regulator
losses.
The questions:
- is there another device that I could use instead of BJT's? Switching
10v & carrying an amp at low loss (1/10w +-). (OK, now it's obvious - I
don't know anything about semiconductors <G>)
- are there through-hole BJT's with very low VCEsat? (I've not used
SMT's & I suspect that they'll be a fabrication challenge.) Googling on
"low VCEsat BJT" was not helpful.
Well there are Mosfets but if your Vce is only going to be 50mV, I don't see
much advantage.
Graham
.
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- Low loss/dissipation xistor or ...
- From: Bob Engelhardt
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