Expo conv. heater (tomg et al.)

[tomg]

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> From: Steve Varner <varner at k-online.com>
> To: synth-diy <synth-diy at mailhost.bpa.nl>
> Subject: Expo conv. heater (tomg et al.)
> Date: Wednesday, January 27, 1999 8:08 PM
> 
> I haven't built a discrete VCO yet (just CEM chips in a kit VCO). I want
> to build a 3046/thermostat circuit, but I have a few questions.
> 
> 1. Do you really need a separate power source for the heater part?
> That's a real pain in the rear. You mentioned regulators and I've seen
> separate supplies mentioned on the web... so that's why I want to know.

No. But you have to beef up the one you intend to use a little. A fair
sized set of heat sinks for the regulators would be good.

> 2. Barry Klein suggested putting the 3046 under a styrofoam cover to
> isolate the chip from heat loss or gain - sort of a chip calorimeter.
> Has anyone done this?

Not me, but Berry is a pretty bright guy. Seems like it would be a little
odd though, kinda like a 3046 happy meal or something. 

> 3. How do you know where to set the temperature trim on the thermostat?
> I mean, how do you know where to set the temperature and how do you
> measure a silicon chip's temperature accurately anyway? Not having the
> temp too high or low was discussed, so this is important.

If it's too hot to keep your finger on it, It's too hot. Nice and warm is
the ticket, if you are just using one 3046 like I did in the vco7c. If you
intend to use one for each vco then the idle current needs to be the same
for both chips.   

> PS, if you folks lived in San Diego instead of 2 degrees from the Arctic
> Circle you might not worry so much about temperature   ;-)

I'm a guitar player. A little drift in my tuning doesn't bother me at all!
I'm just glad I don't usually have to worry about trying to keep  6 of them
right.

-tg