0024Matrix Grand Prix (Part 2)
Continuing the journey of building a hardware car racing game.
In part 1 I had experimented with a stepper motor that includes a gearbox. This time I’ll try one without:
The SP20181 is a very small stepper motor with only 20 steps (18° per step) and no gearbox. It can rotate very fast, but has very little torque.
Because the motor’s shaft protrudes a few millimetres at the back side I couldn’t fasten it directly to the chipboard. So I built a quick contraption, using even more chipboard scraps. And then I realised that drilling a small hole below the motor would have been way easier, but hey …
I changed two more things in this second prototype:
- Instead of a string made from nylon string I used one made from cotton. These are much nicer to handle (the nylon string just kept jumping of the pulleys while I tried to get it in place), and I think they look better (the nylon string tries and fails to look invisible – the cotton string doesn’t even try and thus cannot fail).
- I made the idler pulley adjustable so that I could easily adjust the tension after mounting the string.
I could reuse the Arduino program for controlling the motor, only the parameters setting the number of steps and the motor speed needed to be adjusted.
How did it turn out? Well … double-edged. The motor’s torque is really low, so I had to use it at a slow speed. Otherwise it would instantly skip steps or not move the string at all. However, it still moved considerably faster than the motor I tried last time.
What I hadn’t thought of in advance, though: And having only 20 steps the motor turns a whopping 18° at each step, making the movement rather junky:
Okay, this motor is fast, has low torque, and no gearbox. Why not … add a simple gearbox? I suppose it would still be fast enough while at the same time noticeably improving the torque. Stay tuned for part 3!
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