What we are trying to accomplish is digitally controlling the speed of a 18VAC motor, which can easily pull 1A (specifically old H0 Märklin locomotives, which can reportedly pull 5A at peaks). The supply power in our case is fixed at 18VAC.
Ideas we considered:
- Voltage divider with digital potentiometer which is probably not feasible due to the high current requirement.
- Using a DIAC+TRIAC dimmer circuit (with a digital potentiometer), but the existence of low-breakover-voltage DIAC's seems to be a myth. I found one 15V SIDAC but that still seems to high for our 18VAC motors.
Dimmer circuits for AC with voltages below 30V don't seem to be popular so I hope one of you can come up with/knows a circuit able to do this. Or perhaps you know an alternative for the DIAC? Not sure if this helps but a microcontroller with PWM capabilities is available.