Control cct. for triac S-C devices - logic circuit controls optical coupler and trigger of input to triac

摘要

Control circuit for triac elements used for interfacing logic circuits to functional networks or units does not need sensitive relay arrangements. The circuit is triggered when the logic circuit (20), in this instance an 'or' gate provides power to operate an opto-electric coupling unit (14) having an output resistance element whose value falls when illuminated. This output resistor is in series with an R.C. (17, 18) circuit across an A.C. supply (1, 7). The junction point of the two resistors supplying the trigger electrode of a triac (19) via a series diac (16). Since the resistance of the coupler is slow to recover the triac priming voltage is held during reversal of the A.C. supply.