I wanted an rpm indicator on the mill, i have a handheld one but since it had one originally i thought why not use it.

since we're on a vfd don't need this lot anymore

apply bandsaw

i'm using a 12VDC wall wart to power it. you can use the old 120V if you want, just chop it off at the other side of the transformer or use the whole board.

Remove D1 (this converts the 12VAC from the transformer to 12VDC, you could cut all the way past L1, but this way you get reverse polarity diode protection and some filtering/smoothing.

attach a power plug.

add 12VDC

tadah!

now i just have to find where i put the optical pickup....