Re: [amsat-bb] Temperature control...PTC thermistor info

["Mark L. Hammond" <hammond@xxxxxxxxxxxxxx>]

At 02:02 AM 5/23/2001, you wrote:
>Now I need to tackle the temperature stability problem of the 3733.
>
>I read on the list about someone using a PTC thermistor on the crystal.
>
>What are the specs?  Does it run on 15 or 12 volts?  Where can such
>an item be obtained?
>
>Thanks in advance!
>
>Kevin
>N0BEL


Hi Kevin,

I bought a few of these a couple of weeks ago; they cost a couple of 
dollars each.

Digikey part number KC003P-ND   (50 deg C)
Digikey part number KC004P-ND   (60 deg C)

www.digikey.com of course :)

They'll work off the 12 Volt supply in the Transystem 3733 just fine.

Installation was easy:

1) unsolder the leads from both sides
2) tin the crystal case
3) solder one side of the thermistor onto the crystal case
4) feed +12V onto the other side by soldering/routing a wire to the 7812; I 
chose to remover a screw and run the wire from the other side, rather than 
drill any holes, etc.

Here are some pictures of my thermistor "oven" in one of my TranSystem 3373 
units:

http://camel.campbell.edu/~hammond/ham/transystem/3373_thermistor.JPG
http://camel.campbell.edu/~hammond/ham/transystem/3373_12v.JPG
http://camel.campbell.edu/~hammond/ham/transystem/3373_7812.JPG
http://camel.campbell.edu/~hammond/ham/transystem/3373_tape.JPG
http://camel.campbell.edu/~hammond/ham/transystem/ptc_60deg_thermistor.JPG

I didn't get any literature with the PTC thermistors, but I did a little 
digging and found these.  You can print out the ones that interest you...

http://info.digikey.com/T011/v4/455.pdf

http://www.thermometrics.com/assets/images/ptcnotes.pdf

http://www.thermometrics.com/assets/images/pto.pdf

I used one of the 60 deg units to start with.  Works great.  I did have to 
snip the crystal leads a bit to lower it so the thermistor didn't touch the 
top cover.  I put a small piece of electrical tape over the top, just in case.

Hope that information helps?

Mark L. Hammond  [N8MH]

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