TRIAC control with Zero Crossing detection

Triac control circuit with built-in zero crossing detection and open collector output

3D model of a triac controller board PCB

Relays are bulky, heavy, power hungry and expensive (thus, they cannot be used for dimming lights or other devices!). This is what this little PCB is all about: controlling a TRIAC by leaving the possibility of using it as a dimmer.

Triac controller with zero crossing detection schematic

The Schematic is pretty simple: on the right, we have the high voltage side, separated from the low voltage one via a 1.5mm PCB cut underneath the two IC.

One IC (white) is a MOC3023 (Triac driver) and the other in black is an H11AA4X used as Zero crossing detector.

When connected to the main (PREF-H and L contacts) and to a load (LOAD-H and L contacts) the PCB will generate a 100Hz pulse on the COLLECT output, based on the circuitry that is going to be placed to control it. On the other side, the DRIVE line will enable external circuitry to fire the TRIAC at any moment.

Assembly view

A snubbing protection is implemented by using a 39R and 10n cap near the transzorb (this serves to shut the triac OFF when it is not driven from the outside).



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