The circuit in the figure can be used to trigger a triac or even a comparator in a project that requires a landing that is produced exactly at a certain phase angle of a sinusoidal signal applied to the input. The 220nF capacitor for the 110 V network and 470nF for the 220 V network is dimensioned to obtain, with the adjustment of the potentiometer of 100 k ohms delays between approximately 0 and 180 degrees. For other frequencies of the sinusoidal signals the capacitor must be recalculated. Note that the diac will drive and remain until the input signal has zeroed out. Between the instant of the trigger and this instant we have the discharge of the capacitor through the load resistor and the output pulse output. This means that, if the load resistor is not correctly dimensioned, there will be no complete discharge of the capacitor and, therefore, the next semiconductor will be triggered at a less angle and thus successively causing the circuit to operate in an undesired manner. The amplitude of the output pulse produced by this circuit is the triggering voltage of the DIAC since it will be present in the capacitor at this moment.
