Gday Fahim
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Would a Basic Stamp be better? OR maybe a Atmel AVR based system.
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Not really, as they also have limited outputs, start to get costly, and require specialised hardware.
The beauty of the PICAXE is its cheap and simple to use.
Ie the 08M and 18X both have PWM but dont require oscillators etc
Just a 5V supply and they are away.
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Why not just use a LM35 to feed back a voltage to a LM317 to maintain a steady temperature.
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LM317s only work down to 1.2V, are only rated to 1A and also need a bit of headroom between input voltage and output voltage. As such, they will give a DC output, but need a lot of heatsinking if you want to draw any large currents. You may need bypass transistors or paralleled 317s to get the reqd output. You also need some way to turn it off as it will never drop below 10% due to the lower 1.2V regulation reqmt.
If you always have 240V nearby its OK, but PWM is much more efficient at doing wide range DC-DC conversion, hence its growing use.
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no2 circuit is quite complex. My head hurts looking at all those op amps.
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Nah. Its all good fun, but a uP that can read digital temp sensors makes it soooo much easier. The end result is the same, ie a ( temperature controlled ) PWM output stream driving a Mosfet
Andrew