[Sandy H.]

I have the need to build a test setup which I can control using an analog +/-10VDC signal for forward and reverse motion. A stepper motor could be a good way to do this if I could build/buy a driver the send the pulses proportional to the input signal. I've seen one that can use a 0-5V input, but if I could locate one that uses +/-10V by default, that would be nice. I'm OK with building electronic kits or following simple plans, so if there is a DIY solution, I would be OK trying that too.

The task is for a test apparatus, so accuracy and precision are not really a huge concern. I just like how my CNC machine has nice slow motion rotational control and thought a stepper would be adequate for the design. I'm open to other suggestions (servo etc) but I don't have a lot of experience with other options. As far as stepper size goes, a low power (50oz-in should be plenty) motor is all I think I should need.

I'll be glad to supply more information if needed. I'm not really sure how to tackle this yet, so I might be leaving out a critical piece of information or two.

Thanks for any help that you can provide.

Sandy.

[Al_The_Man]

Any of the A-M-C, Copley Controls, Aerotech, all sell analogue input drives, the BLDC drives will also drive a DC brushed motor when set to 60deg commutation.
A DC brushed with a tach is an advantage, a BLDC motor already has a digital tach feature by virtue of the commutation pulses.
Al.

[mcphill]

What range of ram are you wanting to run?

[Sandy H.]

Al: I researched the DC motor options a bit and it does seem that there are a few ways to accomplish my goal. Thanks!

mcphill: I think max speed will be around 75 RPM with a minimum closer to 7.5. I have some latitude, but those are good approximations.

Thanks for the help!

Sandy.

[Al_The_Man]

Seems you could do it with a stepper if you wished, you could probably control it to a position more precisely that a servo that is open loop, for precise positioning it would require a PID loop control, open loop servo would not be so precise for some applications.
Al.

[Sandy H.]

I have been very impressed with the quality of open loop control using steppers on my CNC, which is part of the reason I wanted to go that way initially. Your suggestion to look at DC motor controllers, though, helped me re-evaluate my requirements to find a workable solution and I think I'm close on that. I think I can make an assembly for just under $100 that will give me rough positioning using the +/-10V input and that should be adequate.

The real goal of this apparatus is to help ring out the electrical system on equipment that isn't yet ready to be powered for full testing. Basically, I will make a black box that accepts the +/-10V control signal to control a motor which is then coupled to a feedback sensor like will be used on the actual equipment. We can then hook it up using the on-machine connections and power up the control and do a temporary calibration and run through all of the direction and rate functions to ensure that all of the wiring and control settings are basically correct. Right now we use a PC in our lab to simulate the machine by hooking it up to terminal boards with wires etc. This proves out that things communicate and other needs, but if there is a wiring error on the machine, we wouldn't catch that. by using this black box, our assembly staff will have a visual indicator (a moving wheel) to show direction and rate control and we can test the feedback loop using the actual type of sensor that the machine is configured for. High quality motion control isn't really needed, but I guess it could be a bonus. Unless the DC motor arrangement is really bad and send the control into wild oscillations, it would work. I guess if it does cause really bad oscillations, we can just dial back our PID settings in the control and make it so lazy that the outputs to the black box don't swing too rapidly.

Thanks again for the help. If I can come up with a $100 solution for stepper, that would be cool to learn about, but I think your tip about the DC motor will get things done.

Sandy.