>If that isn't enough add a couple more, or go strait for a standard
>electric water heater element. Seems like the last one I bought was 4500
>watts at 220V for about $18. Smaller is available or you could run it on
>110V to cut the wattage. Add a transistor and a relay and bob's your uncle.

Something from a water heater, eh?  I hadn't considered that.

>On the cold side, a fridge would probably work, but there are other options
>without getting too complicated. A couple bags of ice will get you pretty
>close to freezing, add a little table salt to the ice to get it MUCH colder
>(like -65 F). Or you could run a pipe through a freezer and your tank and
>pump coolant through it (saltwater or automotive antifreeze)

This is actually a pretty good idea; since it's important that the water in
the
tank be fairly homogeneous in temperature and in oxygenation, the
standard method is to buy a pump that has a heater built into it, thus
simultaneously mixing, oxygenating, and heating the water.  The problem
is, those are quite pricey.

>Will any of that help?
>-Denny

I hadn't considered running a hose or tube through the freezer; that may
be helpful.  It still doesn't solve my problem of an easy method for varying
the heater.

Ideally I need a 500-1000w aquarium heater that uses a serially input 16
bit number to determine its power output.  Of course, all you can find
in fish stores are turn-the-knob heaters.  I haven't stripped one of those
yet; if the pot which adjusts the temp doesn't have to handle much
current, maybe I can use a digital pot.

Maybe.

Mike H.

_________________________________________________________________
Let the advanced features & services of MSN Internet Software maximize your
online time. http://click.atdmt.com/AVE/go/onm00200363ave/direct/01/

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads