I'm building an Arduino based coffee roaster, and I'm looking to power it by mains voltage in the U.S. (~120VAC, 60Hz).
What would be ideal would be a single transformer with a total of 18-20V AC secondary with a non-center split, something more like a 8V / 12V split. Is this asymmetric splitting even possible electrically? If so, is it sold at reasonable volume?
Single Output (6V - 8V): would power the Arduino, bluetooth module, thermocouple breakout board, solid state relay, 4x DC Relay coils and two ~6V vibration motors to the tune of ~2A maximum.
Both Outputs (18V - 20V): would power the fan motor to the tune of ~3A maximum.
Since I was unable to find anything asymmetrically split, I went with a 100VA Toroidal below, with two 9V outputs @ 5.5A maximum, but I'll have to drop ~4V to get to the Arduino's 5V logic level, and since that's so far I'll be using a switch mode power supply to drop it to ~6.5V before the Arduino for the current demands, which wouldn't be necessary if the transformer output was closer to 6V.
Are there transformers made with two different coil values, something closer to 6V/12V or 8V/12V for around these power requirements?