Finally a decent winder.

[mickmutante]

I had a manual driller and I use it to wing some coils, totally hand wound (hand power, hand guided). I had a lot of fun but it was really difficult to guide, apply the correct tension on the wire, and turn the drill at the same time. So like everyone here, I was trying to improve my winding process, son I bought an old sewing machine, and made some arrangements, the problem... too much speed.. and bla bla bla....
So I decide to buy a winding coil, went to ebay.com and start my search... I bought one of these LowSpeed Coil Winding Machine Winder 0.1Turn 2Direction.
It looks good, 10-700rpm, bi-directional, counter up to 10.000 turns.
I built a wooden a box to put it on, I modified the output shaft, made a guide for the wire... and then I try it.

[copperheadroads]

Great job & some nice looking coils as well

[marku52]

Wow, that is a big stepper motor used to spin the coil. Nice looking work!

[mickmutante]

Does someone know which is the recommended time of work for a stepper motor? And which is the "normal" temperature of the motor can reach? (I mean to try not to force the winder).

[marku52]

A motor that large will not be highly loaded in this application, I wouldn't worry about the motor at all. The motor case can probably reach 100C before you would have to stop. You can probably google the motor spec from the nameplate on the back of the motor and get all the specifications. But I would doubt that you could stress the motor.

[jmaf]

Does someone know which is the recommended time of work for a stepper motor? And which is the "normal" temperature of the motor can reach? (I mean to try not to force the winder).

Under normal conditions they will work forever, or until mechanical failure. What is a "normal condition"? If your motor is rated 12 to 36V, try to use it at 24 V, allowing a 50% margin up and down. As marku52 said, if you used it with the correct voltage(halfway in the range it's made for, for example) the winder will not overload that big of a motor(4 to 6 kilos?).

Using the right voltage and having the windings correctly attached to the driver, you can leave it on forever, it should only get warm.

Now, if you invert the motor coils, the windings are working against each other and will heat up and the motor will seem weak.

[marku52]

Just a quick point, you may find that the motor is "rated" as a 3.6V motor or some such. Not to worry, the drive electronics will be switching the power supply voltage off and on a a rate so that the motor will not be overdriven, even if the supply V is 12 V or 24V or so. Often low voltage motors will be driven PWM (pulse width modulated) from a higher voltage so as to more quickly overcome the motor inductance, and allow operation at higher speeds. Most higher performance stepper dirvers work in this way

[jmaf]

Just a quick point, you may find that the motor is "rated" as a 3.6V motor or some such. Not to worry, the drive electronics will be switching the power supply voltage off and on a a rate so that the motor will not be overdriven, even if the supply V is 12 V or 24V or so. Often low voltage motors will be driven PWM (pulse width modulated) from a higher voltage so as to more quickly overcome the motor inductance, and allow operation at higher speeds. Most higher performance stepper dirvers work in this way

Motors normally have an internal resistance rating and current rating along with the voltage stamped on the back. No matter how narrow the duty cycle pulses, if you're constantly going over the rated specs you're at least reducing the life of the motor.

My rule of thumb: take ratings, use 50% lower. 1 watt requirements, use 2 watt resistors. 12 to 36 v driver board, use 24 v, etc....it saves you a bunch of headache, especially in the day of mostly cheap components.

[marku52]

Don't mean to be argumentative, but have you professionally designed a stepper motor driver? I have. A 1.8V motor (very common rating) means that it will achieve it's maximum safe current (heating power) with 1.8VDC across the resistance of it's windings. Whatever current that is, that is what you should not exceed in a PWM driver. You will never see these motors driven with only 1.8V however. The advantage of the low voltage spec is that the winding has correspondingly fewer turns and lower inductance. At high rotational speeds, you are limited by how quickly you can charge and discharge the windings. Applying a higher voltage allows a faster charge/discharge time via the fundamental equation V = L di/dt, so higher V gives a quicker di/dt, which is what is desired. As long as the current limit implied by the motor voltage rating is not exceeded, no damge to the motor will occur.

Your advice for derating is perfectly correct for DC applications. In the case of a PWM'd stepper motor, it is not required, and will limit max motor speed.

[jmaf]

Don't mean to be argumentative, but have you professionally designed a stepper motor driver? I have. A 1.8V motor (very common rating) means that it will achieve it's maximum safe current (heating power) with 1.8VDC across the resistance of it's windings. Whatever current that is, that is what you should not exceed in a PWM driver. You will never see these motors driven with only 1.8V however. The advantage of the low voltage spec is that the winding has correspondingly fewer turns and lower inductance. At high rotational speeds, you are limited by how quickly you can charge and discharge the windings. Applying a higher voltage allows a faster charge/discharge time via the fundamental equation V = L di/dt, so higher V gives a quicker di/dt, which is what is desired. As long as the current limit implied by the motor voltage rating is not exceeded, no damge to the motor will occur.

Your advice for derating is perfectly correct for DC applications. In the case of a PWM'd stepper motor, it is not required, and will limit max motor speed.

I've been messing around with CNC's and winders for a while, but not professionally, no. That is, I gave away the stuff I made, did not charge for it.

The problem with your advice is that you can't fully control the PWM duty cycle. Suffice to say that if you're running the 1.8V motor at 12 V your maximum duty cycle will be 15% or you'll have excessive current. Running the motor at the rated voltage means you can have 100% duty cycle whereas in your application you are trading speed for torque.

So it is not about it being DC or AC, it's about what he's trying to achieve, speed, torque or maximum both? Maximum speed AND maximum torque only happens at 100% duty cycle, at the maximum rated specs.

[marku52]

OK I see the point of our disagreement. The limitation in the motor is heating, not actual current per se. It would really make more sense for the motors to be rated by power, not voltage, because it is the accumulated heat caused by Pmotor = I^2 * R motor coil * duty cycle that causes the damage. As long as I limit the motor current to the max implied by Idc max = Vdc motor / R motor, then I can run at 100% duty cycle b/c from the heat point of view, it is the same as DC, even tho I am applying a much higher voltage than the motor nameplate.

Why bother with all this monkey motion? Higher speed. As you increase motor revs, the time each phase is on decreases, until eventually the coils won't reach max current before it is time for the phase to shut off. You can see this if you put a current probe on a phase wire while you up the revs. The rise time of the current is set by V=L di/dt, or to rearrange, di/dt = V/L. di/dt, the rate of rise of current is controlled by motor L (we can't change that) and V applied, which we can. So if we apply a high voltage we can get up to max motor current much more quickly, which means we can have a faster max RPMs.

And as long as we PWM-current-limit so that we don't violate the I max spec, we put no more heat into the motor (well, eddy current losses, but that is second order....) than we would running at the rated DC voltage with much poorer max speed.

[David King]

I thought stepper drivers generally had amperage settings that limited the power to the motor. Stepper motors typically run on voltages many times the name-plate voltage. On Elepro's cnc winder I'm running a 1.75V motor at 40V. It gets warm but I can limit the current from anything between .5A and 2.4A if I don't need the extra torque at speed. Stepper motors are "different". I would far prefer to use a DC or 3phase motor for a spindle but that would require a feedback loop for counting turns which adds to cost and complexity of the project especially when you need to synchronize the traverse stepper.

[marku52]

Yes, that is exactly as I described, running a 1.75V motor at 40V with the current limit controlled in the drive electronics.

How do you synchronize the traverse stepper today? does it get a pulse count from the stepper drive? it's pretty easy to get a once per rev or even multiples/rev pulses out of an optical interrupter. I'm using the paper advance encoder out of an inkjet printer to drive my red lion counter, once per rev, but it would be pretty easy to make a disc that gave you more pulses per rev. just draw up the encoder disc you need in a draw program, print it out on transparency, moount to your shaft, and bob's your uncle, so to speak. or even simpler, just stick pieces of electrical tape on transparency to do the same.

[David King]

Marku52. You can read all the details of the winder in a sticky at the top of the main pickup makers page. It uses a PIC to generate pulses for both motors and send them out. The PIC asks a series of questions for setting up the bobbin height, the number of turns, the winds speeds and ramps and either a variable pitch wind pattern, a single pitch or a randomly generated pitch for the traverse.

[marku52]

yeah so the code would have to be rewritten (and an input port configured)to take in counts from the shaft instead of deterministically commanding one count of traverse for every X counts of rotations.

How do you like that winder, esp the stepper tensioner? I may have to build a production winder....