View Full Version : 4 Wire Servos
11-04-2011, 12:08 PM
I have a bunch of 4 wire Servos (with 4 wire encoders). I don't have much info on them other than they have the terminals listed as +, -, +, -. Are these just like two wire servos but they happen to have 4 terminals?
Is there a easy way to test them, and some cheap servo controllers that would work with Mach3. I'm just playing around with them at this point so I don't want to spend much money.
11-04-2011, 12:18 PM
what do they feel like when you turn them? Do they Cog? It sounds like bipolar steppers with encoders attached.
You could hook a 1.5 volt battery up to one or the other pair of of + - and see what happens.. If it is a stepper - it will lock up - if it is a servo it will spin.
11-04-2011, 01:36 PM
They are servos. They do not cog and look like typical DC motors with an encoder attached. And I hooked up a 12v power supply to the + and - terminals and got them to spin.
Now, for a low cost servo controller....
11-04-2011, 01:48 PM
You didn't mention whether they are P.M. servo's, a wound field servo has four conductors?
11-04-2011, 01:53 PM
Is there a easy test to tell if them are PM servo's? At 12V, they seemed to run ok but with some vibration so I am assuming that they are 24 or 48 volt.
11-04-2011, 03:21 PM
A wound field motor has coils in the stator.
If you can identify the armature pair(s), shorting these together and giving the armature a good spin will tell if they are PM, if they are, there will be a distinct braking effect when spun.
11-04-2011, 09:06 PM
Sounds like a servo motor with a tach on the end. The encoder would be a seperate part. DO NOT put any power to the tach connections or you will burn it out.
11-05-2011, 11:43 PM
It could also be a motor with 4 brushes. Are the brushes all on one end 90 degrees apart or on both ends of the motor? Either way you can use a Whale3 drive to run them.