what is the minimum Tpulse and maximum frequency to drive a stepper motor ?

[takis1234]

Hello,
as newbie I need your help please to control the speed of stepper motor like Nema34. I have available power supplies and also drivers as DM860a. I like to control the speed from 50rpm to maximum for the following stepper 85BYGH450D-002 connected as bipolar, using a potentiometer. Thus , for starting , I can accelerate and decelerate turning "slowly" the knob right or left. Can I use the Arduino Uno r3 for this purposes ?
1. Τhe Arduino running its code, will provide to send at the 4 pins output, the minimum Tpulse and also the maximum frequency to the above motor so to reach the max speed ?
2. Which is the minimum Pulse duration in ms or us , and which is the max frequency which can held this stepper ? This freq is measured at one coil or is the basic output freq which needs to be divided by 4 ?
3. All stepper motors ( Nema 17-34 ) have the same minimum Pulse duration, and also the same max frequency that works ?
4. can I use the timer 555 , which has a very simple circuit ? In that case what will be the minimum timing of the pulses and also the maximum frequency so to obtain the maximum speed from this stepper motor ? Next, the output from the 555 needs to be send to a shift register or H-bridge so to produce 4 output pins to drive the DM860a ?
thanks for your helps

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[James Newton]

Maximum speed is changed by so many things that there is really no way to calculate it in advance. And it isn't a common question. Usually, people have a known load and desired speed, and want to know what driver / power supply / motors will be required to reach that goal.

You can make a reasonable estimate of the power required to drive a given load at this page:
techref.massmind.org/techref/io/stepper/estimate.htm

1. You can program an Arduino to do just about anything, and it can certainly produce pulses faster than a stepper motor can handle.
2. Pulse width is specified in the driver data sheet. As I said, max speed is impossible to know in advance.
3. Stepper motors don't have a minimum pulse duration, stepper motor /drivers/ have a minimum pulse width. Stepper motor datasheets have a graph that shows the torque at different speeds.
5. Again, minimum pulse width is in the driver datasheet. Max frequency can't be predicted. I have no idea why you would want to use a shift register or H-bridge between a 555 and a stepper driver... The 555 can generate pulses to test the driver and motor. For more complex control of multiple drivers / motors, you would need an arduino or PC.

For help with designing a 555 timer circuit see:
techref.massmind.org/techref/logic/555s.htm

[takis1234]

Hello James, first thank you very much for your analytical answer.
ok, the max speed depends of the load.For start I will attach a metal disk (diameter 15cm , weight 1.5kg). So, if I understand well, for a dedicated power supply and for a dedicated stepper motor , I need to increase only the frequency to take higher speed ? What will happen If I increase the freq more that the freq which the motor can handle ? will damage the motor ? will loose the torque the motor ? will overhead ?
Have you in mind any ready to use code for Arduino with acceleration, deceleration and buttons or joystic so to start from this ?
thanks again

[vegipete]

A disk like that puts a dynamic load on the stepper motor. So it will take torque to change the RPM. Since the torque output by a stepper motor decreases with increased RPM, the ability of the motor to change the RPM decreases as the RPM increases. Thus the acceleration also decreases, until no more acceleration is possible at some RPM. (This RPM depends on the motor, the driver, the power supply, maybe even the colour of your socks.)

As such, high frequencies shouldn't hurt the motor although more heat will be generated.

In the Adruino world, have a look at the 'AccelStepper' library. It is easy to use and can generate nice acceleration ramps on multiple motors.

[takis1234]

thanks vegipete for your help.