Need Digital Temperature Control Module Similar To Radio

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WildBoar
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Need Digital Temperature Control Module Similar To Radio

Post by WildBoar » Sun Jun 23, 2002 8:16 pm

For several years RS has sold a $20.00 Digital
Temperature Control Module. You preset the
high and low trip points and an ouput signal
is produced that can drive a logic gate,
transistor, etc.<p>If you want to see it go to this URL:<p>http://www.radioshack.com/product.asp?c ... 910%2D4911<p>I'm looking for something similar, only with
a much wider temperature range. The RS unit
cuts off around 120 degrees fahrenheit.
I need something in the six to seven hundred
degree range.<p>I realize $20.00 isn't going to buy me anything
with a range of six to seven hundred degrees!
However, I don't need a massively complex
industrial style unit like the kind you might
find in the Newark or Allied catalogs.<p>A surplus unit would be great, if it's in good
condition. <p>Can anyone help?<p>WildBoar

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Chris Smith
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Location: Bieber Ca.

Re: Need Digital Temperature Control Module Similar To Radio

Post by Chris Smith » Sun Jun 23, 2002 10:45 pm

You dont want to build one?

WildBoar
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Re: Need Digital Temperature Control Module Similar To Radio

Post by WildBoar » Mon Jun 24, 2002 2:14 pm

Hi Chris Smith.<p>Oh yeah, I always think about building
everything!! At least I did when I was
a lot younger, anyway.<p>If a kit is available, tell me where to
buy it. I'll place an order right away.<p>Before the the PC and the Web I collected
mountains of data books from the various
electronics component manufacturers. These
data books were filled with schematics with
names like "DVM-on-a-chip", or "TV-on-a-chip."
These diagrams ALWAYS contained discrete
components like super precision resistor
arrays (0.01% or better), or incredibly
unusual capacitor or inductor values that
could only be obtained by special order
from one (and only one!) manufacturer.<p>For many years I read the column by Bob Pease
in Electronic Design magazine. He would
often write about calling up companies like
Caddock and requesting a few 0.00l%-50 meg
resistors for an experiment he was running.
Most of us can't do things like that, obviously!<p>If you can point my browser to a schematic
with components that can purchased from
Digi-Key, Mouser, etc., please do so without
hesitation!<p>Thank you, Chris.<p>WildBoar

Jerry5555
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Re: Need Digital Temperature Control Module Similar To Radio

Post by Jerry5555 » Sat Jun 29, 2002 2:02 pm

If I wanted to raise the controlable temp. on a cheap unit like that I would "fudge" the control probe with common resistors to move it's range up.
I am not familiar with the unit mentioned but I will assume it has a "thermister" type probe. You could add resistors in series & parallel so that you could add say 400 to the reading. Example when it reads 100 you add 400 and you actually have 500 degrees. If It reads 190 add 400 and you have 590. So I would measure the probe by itself and I would expect to see it reads 1000 ohms at 75 degrees Or it might be a 500 ohm probe which is 500 ohms at 75 degrees. There are also standard thermisters that are 10,000 ohms at 75 degrees. It might not be real accurate but it would get you going.

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Crowbar
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Re: Need Digital Temperature Control Module Similar To Radio

Post by Crowbar » Sat Jun 29, 2002 5:41 pm

Try AutomationDirect.com. They have some small industrial controllers (1/8 and I believe 1/16 DIN) and they are very reasonably priced and should handle just about any thing you could want to do.
Keep Prying...

Crowbar

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Edd
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Re: Need Digital Temperature Control Module Similar To Radio

Post by Edd » Tue Jul 02, 2002 8:07 pm

Wild Boar : The probe on the unit shown resembles
the same unit on their in/out door dig thermometers, and having seen the tracking with
both sensors in the same temp environment and
their uniformity: I suspect the probe element to be the same as the units indoor sensor which is a 1N914/4148 diode.Your temp range mentioned of
600-700 d/F hmmm sounds like soldering temp range. That would be in the frying range for a
diode or therm. Look into utilizing a thermocouple as your sensing unit. K type wire is chromel-alumel and J type is iron-constantin.
I remember having 4 sets for a Fluke dig therm
and all were ~4 ft long so I took one and cut off the ball end and about 3 ft of wire and this left me with 1 ft to exp with. Stripped the teflon insul from one end and slightly twisted
the wires then put an acet torch to the wire tips
quickly to fuse them into a small ball as the orig did then used teflon wire to connect with
and extend its length with. This was my sensor for a soldering iron temp idling ckt.If you want to look into the same hook up ,connect a sensor to a DVM in the DC MV range and subject the unit to your temp range and the resultant voltage shud give U an idea of the variance and the resultant corrective scaling/amp necessary to interface with the control unit in lieu of its diode sensor.
73's de Edd

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