Re: Need for heat


JeffK wrote:
Hi Rheilly and Rich,
If I stay with using a light, a dimmer would be the ticket. I don't
know why I didn't think of that before, Great idea, Thanks.

Rich. I would not need it to heat up right away. It could take as
long as an hour or so to get to temperature. It will be out all night
or longer unattened. I was thinking about using a Pic16F627a or the
16F628a and a thermistor to control the temperature. Also, it would
have a roof over it and a weather proof box for the electronics.

So you think resistors could heat up the aluminum? If so how, what
type of battery voltage am I looking at and how many mah (or amps)
would I need? How long would it last?

Thanks Jeff

Hi, Jeff. If you're considering sticking with line voltage for power
(a good idea -- 200 watts is something like leaving the car headlights
on, your 12V battery won't last long), you also might want to consider
just cannibalizing a drip coffeemaker hotplate. The heater element can
be affixed to the aluminum without too much difficulty. The built-in
bimetallic switch will take care of the temp control.

If you're a little crafty in how you mount the heater, you can achieve
pretty much the right temperature, and it will have the ability to
compensate for changes in line voltage, or an occasional breeze cooling
the surface of the aluminum. A lamp dimmer doesn't have this
capability. Also, you'll have the capability to come up to temp
quickly.

On the other hand, the coffeepot hotplate temp controller will have
some hysteresis, and the aluminum plate temp will go up and down a bit.
However, from your original description, it doesn't seem that really
precise control is much of an issue for your experiment, just that it
be within the range.

And yes, if you aren't familiar with using line voltage safely, this
solution is not for you.

Good luck
Chris

.

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