Question about a DC motor w/ encoder

[JohnCU]

We're building a robot and I got 2 Pittman motors off of Ebay for cheap: 15.1VDC, 256 CPR 2-channel encoder. From what I've been able to find online, the motor I have is the 8691 Pittman motor seen in this pdf: link

However, the encoder is different. Instead of 5 pins, as shown in the above pdf, my motor has 7 pins and the encoder looks exactly like the one shown here, Motor 63XX with HEDR8X00 Encoder 128/256 Line Count: link.

However, that is not the motor I have but it is the encoder since it is the same exact size and shape and has 7 pins. I'm confused at the functions for the 7 pins though. I understand pins 4-7 (encoder ground, vcc, chan A, chan B) but the first 3 pins are:
1. Motor Ground
2. Motor (-) 2
3. Motor (+) 1

I have no idea what this notation implies and couldn't figure it out in the lab today. Also, the encoder we have, when read back into the program we coded, outputs a triangular wave from 0 to -1 constantly. We have no previous experience with optical encoders, so what is this telling us? That it registers a -1 everytime it makes a count?

 

[dkozloski]

1,2, and 3 are the motor leads.

 

[JohnCU]

Originally posted by: dkozloski
1,2, and 3 are the motor leads.

why 3? why not just the + and -, the amp we're hooking it up to only has 2 leads, gotta ground it somehow.

 

[dkozloski]

Take a DVM and see if the motor leads are center tapped to ground. If not just ignore the ground.

 

[bobsmith1492]

The "ground" is probably just an earth (chassis, safety...) ground; i.e., connects to the case only and not the windings. Check it with the DMM. If so, you obviously don't need it (esp. at 15V) unless there is a noise problem.

 

[JohnCU]

There are also 2 other leads from the motor, red/black, I guess for by-passing the encoder to just use it as a regular motor.

Today, I went to the lab to do some more testing and there is no connection between the Motor (-)2 pin and ground but there is between ground and +1 pin, and between the (-)2 and (+)1. I left the ground out and hooked up everything, with the motor (-)2 and (+)1 hooked to the amplifier.

Got nothing, but I could turn the motor and it would give me pulses as it turned. Still, to get it to turn I had to wire in the red/black leads to the amp... I tried to email the company but it came back rejected... perhaps I'll call them tomorrow.

 

[JohnCU]

wtf? the company said it was proprietary information from HP and they couldn't tell me!

 

[MrDudeMan]

nm read OP