Re: Electrickery advise needed

In article <PtskxJAbDh4KFwg5@xxxxxxxxxxxxxxxxxxxx>, dont_spam@xxxxxxxxxxxx
says...

In article <egmEm.49361$q07.22050@xxxxxxxxxxxxx>, ian field <gangprobing
.alien@xxxxxxxxxxxx> writes

"Andy Bonwick" <nospam@xxxxxxxxxxxxx> wrote in message
news:dvg6d55ockfo5bblk1kumn273b36frau66@xxxxxxxxxx
I need some resistive (resistance) wire for a little project I've got
in mind so where's the best place to buy it from?

I'm thinking Maplins would be a good starting point but my experience
of their staff suggests that the useless cunts know even less than I
do and that could be very dangerous.

Another question is should I rely on altering the length of wire to
get the temperature right or should I be sensible and wire in a
potentiometer of some sort?

Its quite unlikely you'll easily get hold of a potentiometer that can handle
the current for a resistance wire visor de-icer, if you do its going to
waste an awful lot of power on any setting other than zero resistance.

The modern way of controlling current is "Pulse Width Modulation" (PWM). Its
not a black art and there are some web sites with very detailed
illustrations of how to put one together.

One of the simplest you can find is based on the LM/SE/NE555 timer chip
(multiple choice prefix letters from many manufacturers). Its literally half
a dozen components including the chip, a power MOSFET (transistor), a couple
of diodes and resistors and a potentiometer.

With the added bonus that any cunt with half a brain would throw away
the expensive

<10p

bulky

2mm square surface mount

heavy

<1g

unnecessary timer chip and juts use the transistor and pot.

Lol, and waste all that power as heat from the transistors? Get with it
grandad, PWM isn't hard to understand, its just switching it off and on very
fast.


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frag
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