I'm at my wit's end. I'm currently designer a miniature coil winder, and I need a way to maintain tension on the wire while it is doing its work. The first thing that came to mind was to buy an ordinary BLDC cooling fan and adapt it to the machine, mounting it on the spool and then make it gently counteract the motion generated by the step motor that I placed on the winder.
Then things got complicated. After breaking the fan apart, I found that it's using a deeply integrated special purpose control chip (U1) that uses an external hall sensor (U2) to monitor position (as it should) and that cuts power to the wingdings if it senses that no motion is taking place, which defeats the whole plan that I had in mind. And I can't think of a way to bypass that condition.
So I ordered a dc motor from sparkfun, and it should be delivered in the next few days. But I doubt that it's going to work the way I want it to, mainly because its reduction gearbox will maybe add too much torque resistance for what I need. I tried to order a motor with a 1:10 gearbox, but ended buying one with a 1:18 because they ran out of stock of the former. The other motors listed in their site have output shafts of 3mm dia and look to flimsy for my application. The motor I ordered has a 6mm dia shaft, which feels about right for my purpose. My main concerns are that maybe the motor will produce too much torque (even though I plan to PWM it) due to its gearbox, or that it might overheat because it will be slowly rotating backwards while I apply power for it to run forward.
Plan B would be to use a passive system by simply adding a friction clutch that could be adjusted with a spring and a screw, but I don't like it because it would leave too many variables out of my control; such as losing tension when the winder stops, or wide swings in tension when it changes speed.
The coils will be 10mm id x 20mm od x 5mm thick using 0.010" (I think it's #30 gauge) magnet wire. And I'll be using a couple of small step motors to control the winder and the wire guide. I've already designed and tested the main mechanism and the motion controller and it's working as it should be. The only thing left for me to do is find a way to control the tension in the wire.
I really need to make this thing work ASAP, or I'll smash my face into a deadline ... any suggestions?
Then things got complicated. After breaking the fan apart, I found that it's using a deeply integrated special purpose control chip (U1) that uses an external hall sensor (U2) to monitor position (as it should) and that cuts power to the wingdings if it senses that no motion is taking place, which defeats the whole plan that I had in mind. And I can't think of a way to bypass that condition.
So I ordered a dc motor from sparkfun, and it should be delivered in the next few days. But I doubt that it's going to work the way I want it to, mainly because its reduction gearbox will maybe add too much torque resistance for what I need. I tried to order a motor with a 1:10 gearbox, but ended buying one with a 1:18 because they ran out of stock of the former. The other motors listed in their site have output shafts of 3mm dia and look to flimsy for my application. The motor I ordered has a 6mm dia shaft, which feels about right for my purpose. My main concerns are that maybe the motor will produce too much torque (even though I plan to PWM it) due to its gearbox, or that it might overheat because it will be slowly rotating backwards while I apply power for it to run forward.
Plan B would be to use a passive system by simply adding a friction clutch that could be adjusted with a spring and a screw, but I don't like it because it would leave too many variables out of my control; such as losing tension when the winder stops, or wide swings in tension when it changes speed.
The coils will be 10mm id x 20mm od x 5mm thick using 0.010" (I think it's #30 gauge) magnet wire. And I'll be using a couple of small step motors to control the winder and the wire guide. I've already designed and tested the main mechanism and the motion controller and it's working as it should be. The only thing left for me to do is find a way to control the tension in the wire.
I really need to make this thing work ASAP, or I'll smash my face into a deadline ... any suggestions?