Pulse delay generator for triac dimming applications

NE555 and Digital potentiometer based pulse delay generator: trigger it and get a pulse back after some delay!

3D model of a pulse delay generator  by Nadim Conti

TRIACS are magical if compared to relays, but they show a real margin only when driven correctly, this circuit generates a pulse after a certain amount of time has passed following an external trigger.

schematic of a pulse delay generator  by Nadim Conti

On the Schematic’s left the triac interface (or whatever you would like to drive with this circuit). Mind that the RC constant defined by C4 and DIGITAL-POT is tuned to be working at the 100Hz of a Zero Crossing detection circuit (Europe).

Top Assembly view (included in PDF)

In principle, the digital potentiometer could be replaced with a transistor or floating gate MOS, but here I was interested in controlling everything via an SPI bus, thus this choice.

The pulse is generated at DRIVE, and triggered at COLLECT, notice R7 and R11 to adapt external circuits in order to be LOW LEVEL ACTIVE.



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