Wall-plug adjustable DC motor control signal PUBLIC

Not provided.

A man who serviced a private business' central vacuum system had 2 - 240 VAC blowers. 1 would run continuously but couldn't maintain enough vacuum on its own. A second blower was acquired but had speed control provisions and came with no signal source, hence this circuit. His motor's signal input required an isolated 0 to 10 VDC signal to operate into a 10ma load. I started with an old 12 volt adapter, gutted it and only kept the case, xfmr & C1 ( a very small 470uf/16v electro-cap). After bread boarding some ideas, I settled on using an LM317T. It only went to a minimum of +1.25v but I was told that the blower would probably run somewhere between 50 & 100% depending on demand. I didn't have a lot of space to etch a small double-sided PCB (through-hole) and mount the remaining components, but it worked like a charm. I demoed it for the guy to make sure he was happy with it, and off he went to put it in service!