Subject: Re: Triac Hack?
Date: Mon, 23 Sep 2002 15:34:19 +0000 (UTC)
Organization: Transcontinental Telegenetics, Ltd.
NNTP-Posting-Date: Mon, 23 Sep 2002 15:34:19 +0000 (UTC)
User-Agent: tin/1.4.6-20020816 ("Aerials") (UNIX) (NetBSD/1.5.4_ALPHA (i386))
John Woodgate wrote:
>>All I want to do is to figure out what value pot to replace the standard
>>one with, so that I can turn it further (for more resolution) and ideally,
>>so I can turn it all the way and still have to motor turn enough to
>>prevent the heater coils from getting excessively hot.
> You need a lower resistance-value pot and two fixed resistors. The sum
> of the three resistances must be near the value of the original pot. You
> replace the original pot by resistor-new pot-resistor, keeping the pot
> slider connection unchanged. This reduces the speed range you can get.
Hmmm......I'm not really trying to reduce the range of speeds, and I
certainly don't want to end up with a higher resistance, no matter where
my dial is set. I need the resistance to be zero, or as close to zero as
possible (I think) so that the fan will go full speed when the pot is
turned all the way "up". With resistors in series with the pot, won't I
get resistance no matter what?
> Just as an example, you might replace a 100 k ohm pot by a 47 kohm
> resistor, a 25 kohm pot and a 27 kohm resistor, totalling 99 kohms, and
> giving *very roughly* the middle quarter of the speed control range.
But I need the top quarter of the pot's range to instead be "spread out"
over the whole 3/4 turn range. I can't lose any speed on the motor, or
else the fan won't turn forcefully enough, and I won't be able to roast as
big a batch.
>>Another idea ocurred to me, which is to put a resistor in parallel with
>>the pot, so that the effective value of the pot is reduced, and when the
>>pot is turned to full value, enough juice still flows.
> No, that may have other, very undesirable effects.
Can you tell me what they are? I don't understand the difference between
turning the pot to give less resistance and putting a resistor in parallel
to give less resistance.
> BTW, some people will say you can't use an ordinary dimmer to feed a
> transformer, because 'it's an inductive load'. It ISN'T, unless you run
> it with no load on the secondary winding, and in that case, who cares
> what the dimmer does (it won't explode)? (;-)
Well, it works. I just want to make it work better.
If you can't say something nice,
say something surrealistic.