Electronic – arduino – Whats the best way to control voltage AC from 0 – 18VAC with a Arduino

acarduinovoltage

What would be a good method of controlling low AC voltage with an Arduino

I have an old motor (Lionel Postwar Train Motor from 1956 example) that runs on AC between 5vac and 18vac with a max of 8amp

I need to be able to manipulate the voltage with the Arduino so I can gradually increase or decrease it. Preferably as a percentage (0% = 0vac > 100% = 18vac) or decimals

So just to clarify. The power coming to the Arduino is already transformed at a constant 18vac.

I just need to safely control the voltage

Thanks

Best Answer

A DC controller "inside" a bridge rectifier may work.
Feed AC via load bridge ACin and bridge AC out to AC2.

If you short Bridge + & - outputs the load runs on full AC.

Now place a DC speed controller between bridge DC+ and DC-.
The controller (pot or PWM short or ...) sees rectified full cycle DC but load sees AC.

PWMing the DC load control (or using a variable resistor or electronically variable equivalent) will alter the AC

schematic

simulate this circuit – Schematic created using CircuitLab

It's likely that converting the whole system to DC would work - unless there is some clever tricks hidden in there. eg points switching 'engines' rated for AC (higher inductance, with resistance too low for undropped DC). Unlikely, but ... . .

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