Motor Speed decrease

I recently purchased the VEX Robotic kits, but I felt bored programming it since I don’t have a lot of sensors. Anyway, I decided to take the robot a bit further by making it fly. I connected the helicopter motors to the PLC but they kept running forever. I then discovered that the robot motor has a circuit board that receives information from the PLC.
I opened one of the motors and removed the circuit board to attach it to the helicopter motor. The problem is that the motor will run for a few seconds and then it stops. When I did the online testing procedure the motor runs fine with in this range (127-197), but if I increase the speed above 197 the motor starts decreasing the speed. I don’t really know why it is behaving like that, but if anyone faced the same problem please help!! I have included a photo of my robot with the circuit board in front.

HELLOW :slight_smile: Any Body Here!!

The problem you are more then likely running into is you are exceeding the output of the h-bridge in the servo output. The extra current is causing the h-bridge to shutdown. This isn’t a programming related problem.

So is there a way to make it work !!

What you need is a separate power supply for the helicopter motors that matches up with their requirements. Look for threads in this forum on running non-Vex motors with the Vex microcontroller. If you have gotten the two to talk together already through a motor output, you might just be able to run it by bypassing the voltage in/out on the cable. (red and black wires respectively.)

Try Thread, Answer to “Motor Speed decrease”.

Right… I couldn’t reply to this thread over the weekend (did it get moved from the EasyC Support Forum?) so I started the other thread that MarkO references. Here is my post, to keep the discussion in a single thread:

Thank you BMX670. I will try your way, and I will let you know if it works.

MarkO, and Quazar thanks for the tip. It is so clear now. :slight_smile:

Thank you Every Body… :slight_smile:

I tried jumping the fuse and it worked.

Watch out the Flying Robot is Coming >>>

Sweet! If you get that to work, it will be awesome.

Jumping fuses may work for a while, but doing that also tends to break more expensive things later down the line (since the fuses were designed to protect the electronics from damage). Without that protection, there is nothing protecting from from overheating or magic smoking.

Arthur Dutra,

You are right, but I can’t stop exploring :)). The fun is not having it, the fun is making it. So far, I didn’t start running the robot yet, because I don’t have a speed controller for the second motor. Plus I am exploring some devices such iPods and such to know how their balance work (when you move the device sideways the photo flips sideways too). If I figure out how they make it then I would make a helicopter that can fly by itself using “motion sensors”. I all ready wrote the program, but now I am looking for hardware to work with it. If it flies for a few minutes and then it crashes, I wouldn’t care because I will feel satisfied making something complicated like that. Plus, the only thing I would need to change would be the circuit board.

I agree in general, but in this case it might not be so bad. I believe that the polyswitch fuse in the motor driver is more to protect the motor itself than to protect the electronics. The driver chip is rated for considerably more current than the polyswitch trip current, and the driver chip has its own internal thermal overload protection.

If you wanted to take this to the next level, you could try to do something like this. the helicopter can actually learn maneuvers from its human operator and execute them on its own.