Choosing a Stepper Motor

My kids and I are currently making a wheeled robot which will hopefully be able to go up and down stairs. I’ve found a few on youtube using rocker bogie type designs. I have built it and wired up a manual controller, however because I’m such a noob to all this I just got DC motors that were way too weak. Each wheel has it’s own motor. I currently have wired the 3 motors on each side to a single switch (forward & back). It can go forward and back, turn (sort of, on the right surface), but doesn’t handle rough terrain at all.

I’ve just ordered an arduino and bluetooth module to control it from the kid’s tablets. Eventually I would like to program it to navigate by itself to an extent, and install wifi and a webcam. With that in mind I think stepper motors would be best for simple routines of autonomously going from one room to another.

I’m looking for recommendations for which motor will have enough power/torque for the job. The whole thing probably weighs around 4-5 kg, including the 12v battery.

Apologies if I have overlooked necessary information or over-simplified it. It’s a pretty steep learning curve.

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Hi Alan,

Sounds like a great project! It’s not going to be an easy feat though - it’ll take a fair amount of DIY and experimenting to get there. The size of motor will perhaps be most affected by the choice of mechanical movement from one stair to another. The more efficient that energy can be transferred into movement, the smaller the motors (and motor controllers) can be. A bit of a “how long is a piece of string” question that is likely easier to experiment with than derive the math for every contact point.

Side note if this is your first Arduino project, then you could always kick off with something with less of a vertical learning curve (but just as educationally rewarding, such as a line following or Bluetooth controlled Robot.

Hi Graham,
Thanks for replying. Funny you should suggest making a simpler project, because that’s exactly what I’m doing now. I’ve used the motors I have and made a smaller frame for a 4 wheel version that will only go on flat ground. It works well with the wired controller (rocker switches mounted in a Ninja Turtles lunch box) at the moment. I am just waiting on my order for the bluetooth module and arduino from you guys so the kids can drive it with their tablets.
But back to my main project, I know there will be a fair bit of trial and error, I was just hoping for a few recommendations for a good powerful motor. I don’t want to have to buy 6 more each time I find they’re not powerful enough, but I also don’t want to go overboard on cost if I don’t have to.
It will be loosely based on this one: but I’m continually changing it as I go. Eventually it will have a webcam, arm, and obviously a mounted nerf gun.
If I get one batch of motors that won’t do the job I’m sure I will be able to use them for something else (maybe evolving the smaller robot).
Thanks again.


So I received my order (Uno and HC05) and managed to get a smaller four wheel robot all assembled and programmed fairly easily. Everything connects and moves like it’s supposed to, with one minor problem. It doesn’t seem to have enough power to move when it’s on the floor anymore. The wheels spin slowly when it’s elevated.
I’m assuming that there is too much voltage loss through the L298 now. I don’t know if I need a more powerful battery and/or different motor drivers.
Anyway, it’s getting closer and we’re learning as we go.
If I get four of the LiPo 3.7 batteries together I’m guessing that might work. Or it might fry my L298 in which case I’ll use a different driver. Either way the LiPo batteries will be considerably lighter than the 12v battery I’m using now.
Can’t wait for it to be finished so I can post the project.

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