The past few days have been spent testing my motors and hardware for my Broke-Ass Mario Kart project. I’ll be sharing a tear-down of the project at my FITC 2014 Talk, Broke-Ass Mario Kart.
I bought a simple, unmarked, mobility vehicle motor from Active Surplus.
The motor seems to run a little slow. I get about 42rpm with 12v or 64rpm with 24v. By my calculations, that will give me about 2.01kmh and 3.92kmh respectively. The average walking distance is about 4.8kmh, so I’m tempted to go with the 24v, but that’s a little heavy for my goals.
Below is a comparison of the speeds at 12v and 24v.
I’m probably going to use a motor shield to keep things easy, but I was interested in trying to use transistors and a capacitor, as seen here:
From the video, I was able to list the parts and make a rough illustration of the circuit in Fritzing:
- 2x 2n3055 Transistors
- 1x200v 220 uF Capacitor
- A diode “from a microwave” – I’m guessing that means something “beefy”
- A 12v SLA battery
- An Arduino, a POT, etc.
The circuit lets you send a PWM signal from Arduino to control the motor speed. It’s effective, but a little “burny”. At some point I must have shorted my Arduino to GND connection, because the wire started melting, I noticed the Arduino would get super hot if I used a 9v power supply and the diode on the capacitor can not handle 24v – I’ll need something “beefier”. In spite of the burniness, it runs well at 12v with my PC as power supply. Barely burny at all.
Besides all that, it works:
The PWM circuit is the cheapest controller solution – I think it probably amounts to about $10 per motor, but it’s only 1 direction. I could build a type of circuit called an H-Bridge and try that to get forward and reverse, but I’m content with achieving a functional PWM circuit – I consider that a successful proof of the old, “you can do it cheaper yourself” approach.
Next step is to buy another motor to see if I can get higher RPM and order a motor shield to replace the PWM circuit.