I want to make a small unit with a keypad and LCD screen where i can type in a distance in inches and a stepper motor moves a wheel by that amount.
Im unsure as to what kind of hardware I’d need for this. I’d probably be using a 3A stepper motor and the driver board from hobbycnc.com.
So really i need to program a PIC controller to read the keypad entries, then replicate the serial inputs that the hobbycnc driver would normally get from a PC serial port.
Would the orangutan controllers be overkill for my application?
If anyone can give any advice it would e great. I’ve done lots of computer programming before but only on desktop PC systems. This will be my first ‘embedded’ device project.
The Orangutan controllers have integrated motor drivers that can do up to about 1A continuous, and you can drive a stepper motor directly from the Orangutan (but without microstepping). If that works for you, the Orangutan SV-328 could be quite reasonable since it already has the display and driver, and you just need to attach the keypad. However, if you’re using an external driver, the Orangutan might be overkill since you wouldn’t use the on-board motor drivers. But, if you like the small size, it still might be worth it since I don’t know of other similar boards with an LCD that cost less than the Orangutan.
You might also consider our A4983 stepper motor driver carrier, which supports 2A max per coil. It drives bipolar stepper motors, which generally makes it better than a unipolar driver. If you have a 6 or 8-wire unipolar motor, you should be able to drive it with a bipolar driver. (The Orangutan drivers can also support bipolar operation, but you can set them up to do a 5-wire unipolar, too.)
How many stepper motors can you hook up to the Orangutan SV-328 ? I’m looking at the motors at hobbycnc.com/products/stepper-motors/ , which have both bipolar and unipolar ratings.
The stepper will spin a worm-drive with fine pitch so I do’t think microstepping will be needed.
The motor i would like to use is in the range of 3-4v, 3A. is it possible to increase the power of the output with external circuit components, e.g amplify the outputs in both current and voltage?
Sorry if my questions seem silly but I really know very little about the hardware world!
Your questions don’t seem silly at all. The Orangutans can support one stepper each since you need two H-bridges to support the two coils on a bipolar stepper. 3-4V is quite low, so you won’t need to amplify that. The current is harder, and we don’t have a good solution for motors drawing over 2A. Making a unipolar driver is not that difficult since you’d just need four N-channel MOSFETs, but if you don’t have much hardware experience, you might be better off getting a pre-made driver board.
An advantage of a controller like the Allegro A4983 is that it does internal current limiting and allows operation from higher voltages, which allows higher step rates (and lets you use more common supply voltages, like 12V, instead of 3V). If you don’t need the full torque of the motor, you could run it at a lower current using something like this chip. Our carrier doesn’t cost much, so if you want to play around with it, you could get just one and see how that works with your motor, and get the additional channels later if things seem to work.
I think I could get away with using just one motor, my application is to move the fence on a table to save me measuring time with woodwork.
My friend tells me the output signal can be stepped up with power transformers. Do you agree? If so, I could then use 2 steppers, one at each end of the fence since their driving signals would be identical.
I’m unsure what would need to be connected to the Allegro A4983 in order for it to take user inputs and display on a screen, so I think it best to stick to the Orangutan SV-328 for now.
Just out of interest, what units would you connect to the allegro to make a complete stand-alone system?
I think your friend doesn’t know what he’s talking about (or you’re misunderstanding what he said). If using two lower-power stepper motors is an option, that’s great since the simple solution is to use two drivers (one per motor). Since our limitation is current, not voltage, you might also be able to wire your two motors in series, though I haven’t heard of that being done with stepper motors.
If you want the display and some user buttons, the Orangutan SV-328 is not a bad way to start. It’s possible to do what you’re describing with just the Orangutan, the stepper driver, and a power source.
The MOSFETs I mentioned earlier are transistors. If you want to go that route, it will be far easier to do a unipolar arrangement, and you would connect the transistor gates straight to microcontroller I/O lines. With that approach, there would not be much point to using something like the Allegro stepper motor driver or the motor driver outputs on the Orangutans.
