Thread: New generatot.

The stepper stalling if you try to accelerate it too fast is normal - typically, if you increase the motor voltage you'll find you can accelerate faster than at lower voltages.

I played with on of those units last week. It has a jumper setting for what the knob at the front does. One is variable frequency and one is variable pulse width modulation/duty cycle. They are labelled and are on the jumpers to the right of the knob.
It also has a jumpers for two or three different frequency ranges, if I remember. They are on the left.
It also has a 12v output for DIR which can cause problems on 5v Logic circuits.

Gday Tony,

The problem that you are having is inertia in the motor rotor.
You are increasing the frequency to tell the stepper to rotate faster, but the motors rotor inertia is too much and the "go faster pulses" overtake the motor rotor ability to keep up.
When this happens, the motor will just stop and squeal or if it happens at a lower speed, then you'll get a growling noise.
When you speed it up slowly, than the motor can keep up.

As RustyArc says, you can increase the motor voltage, but keep in mind, you can't go over the driver boards maximum rated voltage which in your case is 24V and you also shouldn't go over the motors max rated voltage. (you need to check the data sheets for that)
You stated in past posts that you were after torque to turn your lathe, try this for a test.
When you have the motor rotating slowly, grab the shaft and try to stop it. You should find it hard to do. Now speed it up to the high speed and try to stop it. You can stop it easy as.
This is because steppers do not have a lot of torque at higher speeds due to the fact that each coil of the motor is turned on for less time, and because it's on for less time, there is less torque.
In machines that have the motors running at high speed they use a multitude of different methods.
The main one is run the motor at high speed and gear it down a lot. this gives you the higher torque and increased accuracy due to the gearing.
Another on the (lot) more expensive drivers (out of my range). When it gets to a certain speed, they change the pulsing technique and pulse every second coil for longer.

Hope this explanation helps.

Dean

I've given up on steppers for carriage/cross/compound feeds, but I came across this geared motor on ebay, pays to check ebay daily. This one is a fair size so might work ok, and I won't need drivers and pulse generators so it's simpler. I will try the stepper in the tailstock though, because it's very accurate and stepping may prove beneficial in some cases.

I've been busy the last few days setting up a bench for electronic projects, almost finished just need to make up an audible continuity checker.

Hi Tony,
Look into pulse width modulation for DC motors.
If you use variable voltage to change the speed, you might for example hve 2V to run your low speed. This how ever has no poser for low speeds.
You only get the power from those motors when your running the full 12V.
This is where PWM comes in.
The voltage ALWAYS remains at the 12V and the time that it is applied to the DC motor changes.
pwm-duty.png
If the pulse width is small, then only a small very narrow pulse of 12V is applied to the motor and therefore the motor doesn't move much.
As the the pulse is increased the time period that the 12v pulse is applied to the motor is increased and therefore the average voltage/time is increased giving the motor more on time and therfore rotating faster.
If the pulse is nearing the 100% mark, the 12v applied to the motor is on more than off and therefor the motor is at near maximum average on time and runs the motor near full bore.

Your 555 timer board can supply this PWM signal apparently from what others have described, the only thing you are missing is a high current FET to do the heavy current pulses. (N channel I think) some thing capable of supplying the motor current with some overheads. IRFZ44N or similar. (Specs. VDSS = 55V. RDS(on) = 17.5mΩ. ID = 49A)


Dean