120VAC control from basic stamp?

[mrlucretius]

Hello,<p>I am trying to make an AC switch that I can control with a basic stamp. This way, I can build a humidity controller, that will switch on a humidifier when the humidity drops too low. Also, a small heating element will be controlled for heat control for my lizard's terarium. <p>I have read about relays, triacs, etc, and am not sure what direction to head.<p>Can someone suggest a simple way that I can make an AC switch that a bstamp io can control? I imagine that the total AC power draw will be 24watts for the heater element plus no more than another 26 watts for a small fan driven ultrasonic humidifier. So thats less than one amp at 120vac i would guess conservatively.<p>Thanks,
Alex Martin
http://www.rettc.com

[mrlucretius]

Hey,<p>http://www.ee.washington.edu/circuit_ar ... em_PC.html<p>This has a few different options. Any comments, suggestions? I guess the relay seems simplest. But I am asking for input here.<p>Thanks,
Alex Martin
http://www.rettc.com

[JKMADSCI]

I think the max output of a basic stamp is about
30ma. Basically all you will need is a base resistor of about 1k feeding a 3904 npn transistor, and an ac relay that runs from 5 volts less than 150ma. If you find a solid state relay that draws less than 25ma you can connect it direct. Dont forget the diode accros the relay!!

[paulrevelcet]

any time the ac mains is involved, you should use a opto isolator if your not using a solid state relay.
<p>If you are using a solid state relay the you can connect it stright to the relay, you will need a dropping resistor to keep from damaging the input led on the relay <p>

[mrlucretius]

Do you know of a suitable opto-triac part number?<p>Thanks

[paulrevelcet]

I found a better Picture of what you need, the part numbers are on the schematic.