midibox driven stepper motor

[cutter filtoff]

Hello, has any one explored driving a stepper motor on the midibox platform? I want to use the steppers to manipulate tape in real time. Any advice would be very helpful.

Thanks

J

[stryd_one]

I want to use the steppers to manipulate tape in real time.

That could be really interesting!

Search for PWM, and keep us posted!

[Imp]

I've thought about that too....

I had the idea to build a stepper-driven Tonewheel (like in a Hammond).

A square-wave could be generated via core or sid and buffered/amplified until it's strong enough to drive the stepper.

Its frequency and therefore the speed of the motor would depend on the note played...

But i actually don't know how to amplify the voltages...an op-amp seems much to weak...

Pwm is afaik for controlling the speed of normal dc-motors, or did i miss something?

[cutter filtoff]

I think PWM is the way to do it, because each pulse turns the motor one step. I'll search it and see what I come up with. My main obstacle to overcome is I have never really done any coding before, so I'm looking for someone up to the task. If you know of anyone who would be interested please let me know.

[Sasha]

I've thought about that too....

I had the idea to build a stepper-driven Tonewheel (like in a Hammond).

A square-wave could be generated via core or sid and buffered/amplified until it's strong enough to drive the stepper.

Its frequency and therefore the speed of the motor would depend on the note played...

But i actually don't know how to amplify the voltages...an op-amp seems much to weak...

Pwm is afaik for controlling the speed of normal dc-motors, or did i miss something?

It is not just square wave nor PWM you need. Steppers coils needs to be energized in right sequential order to turn the motor. Also, there are two different types of it - unipolar and bipolar, and they are driven differently. To drive it i suggest using ULN2803. I did some testing with it and steppers I dug from old printers and big floppy drives, and it work good for smaller steppers. Simplest way to drive the motors is ULNs connected to AOUT and MIDI simple 4bar pattern. :)

[stryd_one]

Ahhh yes the hard drive drumkit :D

Thanks for the lowdown sasha!

OT, just out of curiosity: So which are the motors that are PWM driven? I'm sure RC servos use it?

[Sasha]

Ahhh yes the hard drive drumkit :D

Well HDD drumkit is not about steppers, it is simple driving voice coils.

OT, just out of curiosity: So which are the motors that are PWM driven? I'm sure RC servos use it?

I think any motor can be driven with PWM with exception that steppers needs exact order. But, I don`t know so much about motor control. I`m not sure who was it but some forum member is doing some testing and coding to drive the servos. Those could be useful for making some strange MIDI acoustic instruments.

[Screaming_Rabbit]

Steppers coils needs to be energized in right sequential order to turn the motor.

... so called commutation

So which are the motors that are PWM driven? I'm sure RC servos use it?

e.g. DC-Motors and Servos

Greets, Roger