servo/stepper motors

[hbui3077]

this is probably a stupid question, but how can you tell whether a motor is a servo and/or stepper motor? There's a surplus store nearby, but they have hundreds of motors to chose from.

[vladdy]

In 'general' a stepper motor will have 4 or 6 or 8 wires, usually all coming out of the end opposite the shaft [if single ended].. 5 wire [5 phase] steppers not really recommended for 'first time' hobby useage..

In 'general' servo motors will have two larger wires coming out the back end, three [sometimes four] smaller wires coming from around the shaft end [for the encoder, not always there], and sometimes two smaller [usually same color] wires again going to the shaft end for brake, not always there..The heavier duty industrial servo's will usually have product specific connectors..

do some searches for 'stepper motor' and 'servo motor' [here and elsewhere], and view the photos, the differences will be easy to tell...

here's a pretty definition of 'how' they work,
http://www.woodweb.com/knowledge_bas...er_motors.html

here's a couple of examples..

[hbui3077]

thanks for the reply vladdy, really appreciate it...
some info regarding the dc motor i found is as follows:
*12.5:1 gear ratio
*Optical encoder is +5 VDC(pos. blue, neg. grn), two channel output with 100 pulses and 4.550 pulses per rev.
*RPM: @6vdc: 20rpm; @12vdc: 46rpm; @18vdc: 72rpm; @22vdc: 89rpm
*Dimensions (excluding shaft): 4-3/8"W x 6-1/4"L x 3-5/8"H
*Shaft Dims: 3/8"Dia x 4"
*Weight: 3.85lbs

That's all the info that is listed for the motor...from the picture, and according to your description, it seems to be a servo, since it has the 2 big wires come out of it...one with 4 wires and the other wire looks like it's for the power source. I'll try to get a picture up soon.
But from the description, how large of a cnc table would you estimate it can handle? Thanks again.

[Al_The_Man]

It looks obviously like a DC servo with gear reduction with single ended encoder, the rpm is not very high, at 22vdc the motor rpm would be 1112 rpm.
More info on the motor would be needed to estimate torque etc.
Al

[vladdy]

as a 'guesstimate' given the approximate size and weight of the motor, it should be more than enough for a light duty MDF or similar style cnc table, with the gear reduction it should be able to support machines sized similar to the harbor freight or grizzly sized bench top mills... a full size bridgeport, weel, doubtful it would be powerful enough for normal shop use..

again, just a guess on the information you had given..