**RESOLVED** SEM MT30R4-33 servo wiring?

[Landon]

Bridgeport Series 2 R2E3 w/ SEM MT30R4-33 servos having 5 wires; 110VDC+, 110VDC-, Grnd,...... What are the other two? Is it a drive fault i/o, or servo brake? How do you power/connect?
thanks

[cncsnw]

Most likely a tachometer output, which you don't need if you are using Centroid DC drives (e.g. DC3IOB).

You can test whether it is a tachometer by connecting those two extra wires to a DC volt meter and giving the motor shaft a spin. If you get a small voltage out when you turn the shaft (positive in one direction, negative in the other) then the wires are probably a tachometer.

If you can't spin the shaft, then the wires are probably for brake, and you need to apply power to release the brake. The brake voltage should be specified on the motor's data plate.

[CNCguy]

I believe that the extra two wires were actually a thermal switch , which opened on overheat.
If the wires appear to be a closed contact (low ohms) and doesn't generate any voltage when the shaft is spun by hand,
then they probably are a thermal switch.

[Landon]

Ok so it's a tachometer feed, which would make sense since the machine would fault out if you put too much pressure against one of the ways as it was trying to move. So with that being said, is there not a way to use the tach in a drive fault scenario?

[CNCguy]

So , did you spin the otherwise unconnected motor by hand and did the two mystery wires generate a voltage?

[diycncscott]

Ok so it's a tachometer feed, which would make sense since the machine would fault out if you put too much pressure against one of the ways as it was trying to move. So with that being said, is there not a way to use the tach in a drive fault scenario?

Hello Landon

There is no reason to use a tach as a stall detection device as the motion control hardware uses the encoder feedback to detect a stall and generates an error which cancels movement. ie.. If the control commands movement and doesn't see the appropriate encoder movement -it faults with a stall or position error..

While it could be a tach, we don't have any use for the tach feedback. As CNCGuy points out, the wires are most likely a thermal overload which could be wired into one of the unused PLC inputs and programmed as a fault input but I personally don't think that is necessary because the control has enough built in protection (see above) to prevent the motors from overheating.

Regarding the possibility that the wires control a brake: A brake on a servo controlled R2E3 (series II knee mill) would be highly unlikely - unless the motor is on the knee and I've never run into a B'port servo controlled knee mill configured with the Z on the knee. That said, check it by turning the shaft by hand.

[cnckeith]

Klmoses installed Ajax encoders on his stock Bridgeport SEM motors here is a pictorial of how he did it.

http://picasaweb.google.com/cnckeith/Br ... erRetrofit#

[Landon]

yup that looks like what I did only I put standoffs between the encoder and the mounting bracket that it came on so I didn't have to make a spacer plate for the servo end cap.