Stepper VS DC motors

[Lucas]

What are the pros and cons of Stepper motors and PWM controlled DC motors for use in winding machines?
I just picked up an Arduino with plans to use PWM output for DC motor control.
Then I saw a recent thread started by rdrr about using an Arduino to control Stepper motors that got me wondering.

[big_teee]

This belongs in the Tools & Winder Forum.

[Jazz P Bass]

It is a whole lot easier, circuit wise, to build a pmw/ dc motor setup.

Stepper motors, while being fantastic where accuracy is concerned, can be a bit of a bother when tasked with variable rpm designs.

[David King]

I keep losing my posts. A shitty way to waste time. Not sure what the heck is going on.

Briefly consider small 3 phase motor and fractional VFD. (Needs 240V or step up transformer)
Numbers of pickups?
Budget?

[rdrr]

The main reason I went with 2 steppers is because I didn't want to deal with an encoder and feedback loop that you will need with the dc motor seeing how I think you plan on a cnc type build. I was going down that road to begin with but couldn't find a control board that had the encoder feedback built in. I may still tinker around with one later on but for now the stepper will do. With a chopping driver I should be able to get a few thousand rpms out of it with accuracy though I will limit it to ~1000 to 1500 rpm or so for torque reasons.

I also plan on seeing what I can do to hook it up directly to a pc though a usb to parallel interface and I have a good idea how to do that with stepper boards but I'm not sure how to do that with a pwm board with an encoder.

[David King]

Most VFDs can be easily software controlled through 10 speed steps that you pre-program into the VFD.
Again I can't imagine why anyone would need to use encoders on a winder spindle. That's 2 orders of magnitude more resolution than you need for TPL. A simple turns counter is more than enough.
Simply program the traverse stepper to step however many times for each revolution of the spindle. You can add resolution by doubling or quadrupling the counter triggers but there is no wire guide that will place wire with anywhere near that precision on an oblong coil.

[Lucas]

Right now I am planning on using the PWM output from the arduino and an H-Bridge to drive motors. There is an arduino motor shield that I could use but will most likely DIY. Use some sensors for RPM and count.
VFD - variable frequency drive? For AC motor drive?
TPL?
Budget? As cheap as I can. I have some DC motors from an old set Black and Decker portable tools that I need to take apart and evaluate.
What I was concerned about were pitfalls of motor type. For example; low speed torque and control...

[Kindly Killer]

A DC motor is fine for the spindle. For the traverse it's really easy to program a servo because each position can stand for a location of the traverse. The catch is that you have to gear it so that the full 180 degrees just barely covers your tallest coil - in order to get enough resolution. I yanked geared pulleys and belt from a dead printer that was just about perfect size. I posted the code for my servo traverse on this forum a long time ago if you're interested. It's kinda ghetto, but it's easy and cheap. I used a cheap little $10 servo that's meant for use in toys.

It's easier to find and assemble the parts if you do it the "right" way with a stepper and pulleys and a belt, and it doesn't cost that much - you can use the steppers, pulleys and belts meant for a RepRap, of which there are billions and billions on eBay. Ball screw is unnecessarily complex and expensive IMHO - I think ball screws are meant for moving more weight, not sure.

On my little winder I don't even use a stage - I just clip my little guide directly to the belt. If you use a stepper you have to be able to either move your guide manually to zero position on the coil, or you need a way to zero the position of the stage, or both. Actually that's what I'm doing on my next winder, for which I'm still gathering parts. It's a tiny bit more programming, but less trouble overall. I did the servo thing because it was easy to do with recycled parts I had handy when the mood struck to make a CNC winder.

[kayakerca]

Budget? As cheap as I can.

There are a number of the Haydon Dual Motion Linear/Rotary bipolar steppers one ebay right now @ $40 each. This motor and 2 controllers and you are off to the races. The stroke is a short 11mm, but if you can work with that, they are a great deal!

Haydon Switch and Instrument Linear and Rotary Stepper Drive | eBay

[Lucas]

I remember this same stepper motor posted in another thread a while ago (maybe you?) and I went to look for it again but couldn't find. Very cool.
I think there is an arduino motor driver shield that will drive two steppers. 11mm travel may be an issue though.

(...wheels turning)

[rdrr]

https://www.sparkfun.com/products/10848 shaft is 100mm long and you can get a 250mm long one for about $12.

[kayakerca]

https://www.sparkfun.com/products/10848 shaft is 100mm long and you can get a 250mm long one for about $12.

You certainly can. . .

[Joe Gwinn]

I keep losing my posts. A shitty way to waste time. Not sure what the heck is going on.

Neither am I. What I do is to copy the post onto the clipboard before posting. If the post fails to take, the text is still on the clipboard, ready for a 2nd try.

[David King]

HA! i think I figured it out as user error. I use several different fora software in my daily stroll. I get confused about which button does what.
I think I was hitting the "reply to thread" button instead of the "quick reply button". The result is that the Quick reply text box gets zapped.

[Lucas]

Is there any drawback to PWM controlled DC motors?
I know that one of the issues with stepper motors in the lack of feedback.