Full digital triac circuit diagram

The simple digital circuit shown in the figure can be used to accurately control AC power without any digital-to-analog conversion circuitry. In the application, the system's control computer sends valid data to the SN74HC T534. After latching, it is compared with the output of the asynchronous waveform counter SN74HC4040 through the binary comparator SN74LS682.

SN74HC4040 is driven by a 1MHz clock, which can provide an accurate 50Hz~60Hz clock. At the zero crossing of the AC power supply, the bidirectional optocoupler TIL194B clears the output of the SN74HC4040, allowing the SN74HC4040 to synchronize with the AC signal. At the zero-crossing point, the output of the binary comparator is inactive. The output of the binary comparator controls the isolated thyristor optocoupler TIL3020. After the zero crossing point, the counter starts counting. The output of the binary comparator remains inactive until the counter exceeds the data latched in the SN74HC T534. The thyristor optocoupler conducts the AC signal for half a cycle and does not turn off until the next zero-crossing point arrives.

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Description: You can control more AC channels through circuits such as latches, comparators, and optocouplers. The clock's waveform counter can drive multiple channels at a time. By inserting an EPROM or PAL device between the waveform counter and the binary comparator, exponential, logarithmic, or arbitrary waveforms can be generated.