0-10V Digital Rheostat for LED Dimmer?
I might have this wrong as ive not done it with LED ballasts but a number of industrial controllers which take 0-10v control signal voltage. It's not the only way of doing it but personally in your case i would try using a DAC like MCP4725 - which will either give you 0-5v or 0-3.3 depending upon your supply voltage. 12bit is likely more than enough for your dimmer. I would then use an opamp to bring your voltage upto 0-10v range. Even a cheap opamp like an LM324 with a 12v supply should give you about 0-10.8V, use a pot to fine tune max out to allow for voltage drop in control wiring :)