I know this might be offtopic, but I can’t find any way to do this.
I just got an arduino, and I have been using it to drive Vex motors with the 7.2v Vex batteries. Only problem is, the motors go for a second and slow down. I don’t know much about electronics yet, since I’m not in highschool (yet) but I know that I need some device to keep a constant flow of current.
I have found something to do this. I think it’s called a UBEC? Not sure. But you plug in the battery and 5 volts, 8 amps comes out. Someone on the Arduino forum told me this would work, but the only ones I found on line were either out of stock or came from another country with very steep shipping.
I plan on wiring the setup so that that battery is only powering the motors, not the arduino.
Can anyone help me? I would do anything for help at this point! Thanks!
Which Vex Motors are you using (2-wire or 3-wire)?
If you are using 2-wire, are you also using a Motor Controller 29?
How are you attaching the motor to the Arduino?
Also, which Arduino are you using (3.3V or 5V?)
I’m not familiar with this item, but you shouldn’t need anything in addition to a Motor Controller 29 and the correct wiring.
I’m using the 3 wire motors with a 5v arduino, the arduino Mega. I just attached the ground lead of the motors to the arduino’s ground. I connected the signal leads to the digital ports. I connected the battery positive lead to the positive lead of the motors, and the ground lead to the ground of the arduino.
Also, forgot to mention I am using 6 Vex motors, all at once.
This sounds like the right connection scheme to me. You may want to put a 1K resistor between the digital pin and the vex motor signal lead, since that is they way the Vex digital ports are wired. It shouldn’t matter, but it is worth a shot.
Does the slowdown still happen if you run just 1 motor?
If you have a voltmeter, can you measure the voltage between the black and red wires at the motor? I’m trying to determine if this is a power problem. If the voltage isn’t sagging when the motor slows, then it is probably a signal/software problem.
It’s the same as any RC servo, nominal 1.5mS pulse every 20mS or so. The cortex uses 18mS as the duty cycle. How is your digital output configured? Is it open collector? does it need a pullup resistor?