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    thenutbunny reacted to RobG in Advice about a water temperature controller   
    OCY is right, mechanical relay, besides being loud, will also cause interference and will require more current to drive it. Solid state is a good idea since you can probably find one with zero crossing detection, but you will also pay more for what's basically a triac-in-a-box.
    You can get 25A/600V triac (Q6025R6, BTA24-600, BTA26-600) for less than $2 and coupler with zero crossing detection (MOC3041) for less than $1 (at futurlec.com for example.)
    Oh, and you can always connect few triacs in parallel.
  2. Like
    thenutbunny reacted to OCY in Advice about a water temperature controller   
    I think you should consider a SCR or some kind of solid-state switch instead of a electromechanical relay. Do you have data for life expectancy of such a device if you make-and-break at the rate of once per second?
    -- OCY
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    thenutbunny reacted to RobG in Advice about a water temperature controller   
    First of all, be very careful, you are dealing here with high voltage, make sure your circuit is properly grounded and isolated.
    Dimmer circuit will be perfect for the heater. I would use opto-triac to control power triac, because opto-triacs will isolate your circuit and usually come with built-in zero crossing detector, one less thing to worry about.
    Usually, circuits like this get their Vcc from line power, lowering it using a resistor and zener or regulator. Since you want to do some fancy stuff like USB connection, separate supply is the way to go. You can probably pick up cheap 5V regulated supply or salvage one from an old phone or something, or get unregulated one and just add a 5V or 3.3V regulator (http://www.sparkfun.com/products/526)
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