Heat controling circuit? (ie, Heat Troller type circuit)

I'm trying to find information on a heat controller type circuit,
kinda like what heat troller (www.warmnsafe.com) makes. From what I
understand, it supplies the full voltage to the heating element (in
this case 12VDC), but limits the amount of time the heating element
receives the voltage. So at full on, the heating element is getting
12VDC all the time. At its lowest setting, it is pulsing 12VDC at only
a tenth of a second for every second.

I'd really like to find plans for one I can build on my own. I need to
power a resistive element heater for a telescope (no more then 5watts
@ 12VDC), but would like to increase battery time when I dont need the
circuit on all the time.

Or if there is another (better? easier?) circuit that could be used,
I'm all ears.

TIA

 

You want a PWM (Pulse Width Modulation) circuit, PWM is the magic
keyword that will find you loads of circuits on the web.

http://www.google.com/search?q=PWM+circuit

http://www.google.com/search?q=PWM+dew+heater


Tim

 

There are many examples available on the internet. Here is one:
http://mysite.verizon.net/res0owmd/id1.html
Select key words from this example and use Google to search for more.