I've been searching for a good motor for a school project.
I want to build a 4 wheeled robot/car, that can move quite precisely, e.g. turn 90° (+- 5°) or move 20cm (+-2cm). I tried using these common yellow dc motors with gearboxes, but they weren't precise or strong enough. I know that there are encoders available for them, but that seems unnecessary complex. My thought was using a stepper motor like the 28byj-48. But this uses way to many pins (4 per motor) and the "drivers" are quite big(uln2003). Are there other compact (and not that expensive) stepper motors, that use either 5V or 12V and can be used with the drv8825 or a4988? Or do you have a completely different approach I haven't thought of?
Size is not that big of a problem, but amount of pins sure is. I know that pin extenders exist, but I'm not sure if they could cause problems when used with steppers(especially when driven by ULN2001).
What about a square or circular platform driven by 2 gear motors in a differential drive/steering (skid steering) configuration, mounted with an axle across the middle of the chassis?
Then for the other two wheels just use free rolling casters at the front and back
I probably should have written in my question, but my robot needs to turn on a single spot, like a tank. I'm not sure if differential steering would work with that
Well, I think it's 4x4 = 16 Pins. But I still need 6 pins for analog sensors, 1 for RGB LEDs, 2 for I2C communication and 2 for Servos. So every pin counts
Oh, you're right, English isn't my first language and I confused it with something different. I could try that out. For more power, could I make the 2 motors on every side move the same, requiring only 8 pins, right?
Are you counting VCC and G for each motor? You only need two total for that. If it does become a problem, there are multiplexor boards to add more pins. Very easy to implement.
Hi, I'm sorry, but I don't understand what your saying. English isn't my first language, so I would appreciate it, if you could tell me what you are referring to.
A multiplexer board or port expander allows for example 4 pins plus one from UNO to expander, then the expander connects to the motor drivers (16 wires)
VCC and G do NOT go to the UNO, there is not enough power, it has to be a seperate power supply. The 4 wires going off to the left can go to a port expander for all 4 motors. The port expander then connects to the UNO with 4 wires plus either 1 or 2.
Hi, I think there has been a misunderstanding. I know that I can't power the motor via the Arduino. A port expander seems to be the way to go, one alternative would be sending the same signals to a pair of motors, making them turn the same way and speed. What solution would be simpler?
The problem with same signal two motors is they will not turn the same, these are not precision devices. Even with the expander, you will still need some feedback if you need precise maneuvering. Steppers are somewhat easier, but can still get out of synch.
Okay, I get that. I found this interesting article, on how to mod a 28BYJ-48 Stepper to work with the A4988. I have some of them laying around, so I will give this a try. The advantage is only 2 pins per motor and easier control
