DIY Liquid level controller - The Planted Tank Forum
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post #1 of 4 (permalink) Old 08-29-2007, 04:11 PM Thread Starter
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DIY Liquid level controller

I am putting together a few liquid (water) level controller - aka - a float switch will trigger a solenoid valve to turn on and off the water line. Most over the counter controllers use "a general purpose relay" between the float switch and the solenoid valve.

Instead of using a relay, I prefer to use a TRIAC (Thyristor) - a solid state relay - more reliable than a relay. The solid-state module offers improved safety by not routing the high power of the AC operating the switched devices to go through the float switch.

My question - Anybody knows how the wiring should go - float switch to TRIAC to AC oultlet.


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post #2 of 4 (permalink) Old 08-30-2007, 08:30 AM
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I don't think you'll like this answer, but if you have to ask how to do it, you shouldn't be trying. In order to do it properly you need to design in proper isolation between the line and the low voltage side, with an optoisolator or other means. If you do things wrong you can easily lead to a dangerous and even lethal situation. Stick to a conventional electromagnetic relay, or a pre-configured SSR module, rather than try to "roll your own" by building your own triac circuit.
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post #3 of 4 (permalink) Old 09-03-2007, 02:55 AM
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A SSR is no diffrent to wire up then a electromagnetic one. Most will have only 4 pins, there will be 2 for the mains side (120 or 240VAC) and 2 for the low side. You will need to find out what the voltage for the low side is. Most would be between 3-15v so you can just use a normal battery. Put a switch inbetween the battery and the Llow side of the relay and that should be it. You dont need any back EMF protection as the SR R will have them installed.

Have Fun

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post #4 of 4 (permalink) Old 09-04-2007, 08:23 PM
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One thing to watch out for, I have heard that some triacs wont switch off if the current is very low. And some of the controllers out there have this problem with things like solenoids and very low power pumps. Not sure if youll have problems or not but I know many were suggesting heavy duty relays for critical things (especially solenoids and small pumps) rather than ssr's.
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