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From: John Popelish
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X-Mailer: Mozilla 4.7 [en] (Win98; U)
Subject: Re: thermostat for heat lamp w/ remote probe
Date: Thu, 12 Dec 2002 23:42:59 GMT
NNTP-Posting-Date: Thu, 12 Dec 2002 18:42:59 EST
"Jason A. Arends" wrote:
> i currently use a heat lamp hooked up through a rheostat that i can
> manually adjust for temperature based on a digital thermometer with an
> in/outdoors feature (outdoors uses a probe on a wire). i'd like to make
> a thermostat that will control the intensity of the light based on the
> temperature according to a setting that i make on a dial. i don't want
> it to be an on/off thermostat, but a continuously variable design so the
> temperature is more stable. a common one used is here:
> http://helixcontrols.com/prod_dbs1000.htm but it's digital and costs
> $120. i don't need any fancy features, just a dial. it doesn't even
> have to be calibrated, i can find the correct temp by trial and error.
> the temperature sensor should be small and on a long wire, like a
> thermistor probably. the probe goes in my gecko's cage. is this
> something that can be done easily? i've seen designs for a temperature
> controller using a wheatstone bridge but i have no idea how to make the
> AC vary with this idea.
There are some solid state relays that vary the effective voltage via
phase control in response ot a DC control signal. (for instance the
10PCV2415 good for up to 15 amps out, available from digikey for about
$70) if you can get one of those, it is a simple matter to make a one
opamp PI controller that will hold the temperature constant.
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