last night I fried the motor controller board on my Linde 35 feeder..... But on the back shelf of my "skunk works" I had an old Chemtron motor / feeder unit mated up to my own electronics, which consists of a KB Electronics KBIC DC motor speed control, a few relays, a transformer and rectifier (12 volt DC), a few resistors, and a pair of TVSs. The whole thing was assembled, but some of the final wiring and plumbing had not been done yet.
This unit was designed to be controlled either as a normal constant speed feeder like my Mig 35, or as a feeder designed to work "across the arc" on a CC machine. As a CC feeder it takes the welding voltage, and runs it through a rectifier, and TVS (voltage limiter), and grounds it through a pot and some resistors, providing the KBIC with a reference voltage to control the feed rate.
I quick finished up the wiring, and plumbed in the gas and a few other things this AM, and am now back in business. The unit works fine as a constant speed feeder except that I am not yet set up to operate the contactor on the welder.... not a big deal. It also has a ramp up and ramp down speed adjustment, on the internal controller board, and I can adjust max and minimum motor speed so that my entire normal welding wire feed speed range is covered on my pot, rather than from extremely absurdly slow to way faster than anybody ever runs. And the feed rate is on a 10 turn pot giving a very fine adjustment.
So far the CC function does not operate properly....I need to fine tune my resistances, but it looks like it is going to work fine once this is done.
When completed this machine will work on any DC or AC welder....... but will need to be plugged into the wall. My total cost so far is less than $100 in the project. The Chemtron feeder is a 4 roll feeder...... obsolete..... but feed rolls interchange with Miller Model 10 rolls, and everything else is generic.
An interesting project......and as it proved..... well timed!

H.W.