AN #125 - How to set up zero crossing software to trigger a Triac



This AN was submitted by Mike Crean

Here is some additional info from Mike. He sent this after the first circuit was published. 

If anyone is trying to use the zero crossing detector in AN125 there are corrections.
The 10k resistor from pin 1 of the 4069 hex. Inverter should NOT be pulled LOW
It should be pulled HIGH (5V+). The pulse width on pin 4 should be less than 1ms.
The pull up resistor on the collector of the BC548 should be 1K NOT 1K5.

If anyone is using a sensitive gate TRIAC remember to use a bias resistor (10k) on
the gate to neutral or timing cap line side. This will prevent erratic triggering by
external electrical noise.

The 2nd. zero crossing circuit in AN125 should be used for more stable operation
of the TRIAC.

It also shows how to use Timer0, Urxc ISR and ADCs from the  AT90S8535.

Here are two methods to derive the zero crossing from the mains.

DANGER - WARNING

High voltages are present when equipment is connected to a mains supply.

Some Authorities may only allow suitably qualified & licensed persons to connect any such equipment to a high voltage supply.

Take CAUTION. Avoid electric SHOCK



The pulse time will depend on the mains frequency used in your country.

Download source code and files in an125.zip