Robot Controller : 24V Axis Motors

Hello. First of all i want to let it be known that i am very new to the arduino world!!!! so please forgive my stupidity and lack of knowledge....so please keep the flaming to a minimum! :grinning:

I am an Automation Technician for the natural gas industry and i am a senior at Miami University as well. Our senior design group is designing a drive unit for an old Mitsubishi RM-501 Move master Robot. This robot was made back in the 80's for a short period of time before they came out with a much better updated model, so there is hardly any material online regarding this specific model. Basically we received the robot in a heaping mess. half the motors work, and the original drive unit was in pieces.

What we have learned is that the motors in the axis' for this robot are continuous motion Servo Motors, which i have been studying up on. they are 24v motors and we are looking to control the robot with an Arduino Mega. I have read up on the use of PWM signals to control the position of a standard servo and to control the speed of a continuous motion servo.

My first question is, How can i get my 5v arduino PWM to control the 24v motor? I have read that mosfets are the way to go but i guessi am running into a slight mis-understanding.

The way i understand it, a servo has a Motor+, a Motor-, and a PWM Input. you supply your voltage to the motor and then let the PWM signal do the controlling. although... on all these Mosfet and Transistor drivers i am seeing, they show the mosfet wiring straight to the positive and negative of the motor.

So i guess some clarification would be greatly appreciated as well as some support and recommendations.

I really do apologize if this specific topic has been covered on the forum, but i have done a decent amount of research and could not find anything that specifically relates to my application.

Thank you all in advance!!

-Rob

With servos (non-continuous), the smaller hobby kind anyway, you supply a 1mS wide pulse at 50 Hz rate, good picture here,
http://www.codeproject.com/Articles/513169/Servomotor-Control-with-PWM-and-VHDL
and the electronics in the servo move the position to center.
Keeping the frequency at 50 Hz, making the pulse wider turns it one way, making the pulse narrower moves it the other way.
Standard servos will stop at a position based on the pulse width.
Continuous rotation servos will just keep turning, possibly faster based on pulse width? I don't have any experience with them, especially higher power units.

Motor+ is likely 24V, Motor- is likely the 24V Return (which would also connect to system Gnd withe everything else), and then you'll have to experiment if the servo library 5V output at 50Hz is enough to make the motor move, or if the control signal needs to be more, which you can create by buffering the Arduino output.
Do you have a part number on the servo?

Some youtube videos of the arm that might have control info.

https://www.youtube.com/results?search_query=Mitsubishi+RM-501

CrossRoads:
With servos (non-continuous), the smaller hobby kind anyway, you supply a 1mS wide pulse at 50 Hz rate, good picture here,
Servomotor Control with PWM and VHDL - CodeProject
and the electronics in the servo move the position to center.
Keeping the frequency at 50 Hz, making the pulse wider turns it one way, making the pulse narrower moves it the other way.
Standard servos will stop at a position based on the pulse width.
Continuous rotation servos will just keep turning, possibly faster based on pulse width? I don't have any experience with them, especially higher power units.

Motor+ is likely 24V, Motor- is likely the 24V Return (which would also connect to system Gnd withe everything else), and then you'll have to experiment if the servo library 5V output at 50Hz is enough to make the motor move, or if the control signal needs to be more, which you can create by buffering the Arduino output.
Do you have a part number on the servo?

I do not have a part number at the moment... And to be honest, there's hardly any documentation on the servo motor itself. Like I said this robot was made in the 80's and there's not much info on it.

When I'm back on campus I could get you a part number though.

And if you don't mind me asking, what do you mean by "buffering the arduino output"? Are you referring to some transistor or mosfet setup?

Thanks for your help!

Yes, transistor or mosfet. 2 in series if you don’t want the control signal inverted.
Example:

These are probably industrial servo motors, you'll need a motor driver. Any nameplate on the motor?

A bare servo motor without a driver is basically a high performance motor and an encoder/resolver
to measure position. Servo motors are normally optimised for rapid response and high power at
stationary. Thus they are usually long and thin. Some are DC (two power wires) and some AC (3
phase synchronous with 3 power wires).

Hobby servos are complete servomechanisms (a little servomotor, gearing and driver in one).