opto-isolatortriac
I have designed a circuit for water pump. Please correct me if I am wrong with schematics. The idea is to to switch on/off AC motor pump with 230V and 7.5A, when water is detected.
I have used opto-isolator MOC3063M and triac BT137.
I have four questions:
Thanks.
P.S. Water detector is nothing but plate with two conductors to detect water presence.
Additional: Yes you are right 1.5V is too small, because of voltage drops of led D1 and the led in MOC3063. I consider to use 6V DC power source.
It's a typical derating commonly used in various industries. Primarily to ensure long term reliability. And yes, that particular component can be referred to as a solid state relay.
The LED in the optocoupler is an infrared type rather than a visible type. As such, it has a much lower forward drop than even a red LED, so when the two are in parallel, the IR LED in the optocoupler hogs all the current and has a forward voltage drop of perhaps 1.1 or 1.2V, which is not enough to allow the visible LED to light.
When two similar visible LEDs are in parallel, they share current better, and will typically light to (visually) similar brightness. When the two LEDs are in series (and there is enough voltage for both) then the same current flows through both LEDs and both will light.
Here is what typical curves look like (this one for a Lite-on 4N35 optocoupler)
This one for Cree LEDs of various colors :
Best Answer
As others have noted in the comments, the voltage is not high enough. Assuming the WD1 output is a relay, you might be able to get rid of the indicator LED and use that circuit, perhaps with an indicator light across the pump motor. Alternately, use a 5V wall wart supply and increase R1 to get the proper current.
The triac drive circuit looks okay, suggest a higher value for C1, maybe 0.1uF with appropriate AC voltage rating.
Fuse placement should be in the 'hot' line- it's not clear if that's what you have done.
Heating will be around 7-10W so you need a fat heatsink for the triac. Note that the 8A BT137 is grossly underrated for a 7.5A motor load and will probably fail 'on' at the first opportunity. Suggest using at least a 25A triac (40A would not be too excessive) and giving it a large heatsink.