On Wednesday 14 August 2013 11:52:41 Gregg Eshelman did opine: > On Tue, 8/13/13, TJoseph Powderly <tjt...@gmail.com> wrote: > > Subject: Re: [Emc-users] How to test brush type DC servo motors? > To: "Enhanced Machine Controller (EMC)" > <emc-users@lists.sourceforge.net> Date: Tuesday, August 13, 2013, 11:35 > PM > > On 08/14/2013 12:26 AM, Gregg > > Eshelman wrote: > > I want to see if my motors will run. How do I identify > > the motor wires VS the tachometer wires so I can hook up to > a DC power supply just to see if they'll run? > > a picture would help > but often the motor wires are heavier gauge > > also the 4 wires ( assumption ) are often not gathered > together > because the tacho easily gets noise from the motor > > and the tacho is usually at the end of the motor opposite > the shaft > > and the motor wires are nearer the brushes > > (often, not a rule ) > > hth > TomP tjtr33 > > The motors have flex conduit attached with the bulkhead connectors that > have screw collars. I'd rather not have to take that apart. Is there a > way to identify the motor wires with a continuity tester or ohmmeter? > Is there any wiring standard for those connectors?
Using an ohmmeter, the motor wires will probably have less than 3 or 4 ohms resistance. The tachometer wires will likely be quite a bit higher resistance than that. No wire should have continuity as both to another wire thru what may be a motor or tach coil, and to ground at the motor frame, thats a no-no. One wire, or perhaps the flex itself but ideally not both, should show a solid connection to the motor frame to function as a ground. But as above, this ground cannot connect to any live circuitry because of ground loop considerations. But the motor and tach wires should not be in the same flex conduit for noise reasons. Motor wires being controlled by a PWM servo amp can have several hundred volts of the servo psu imposed on them at ultrasonic frequencies. So the tachometer wiring must be kept separate, all the way to the controllers inputs. A fairly tight twist in the two pairs will reduce the inter-wire noise pickup once they become exposed in the control box. Recommended by Grandpa Gene. :) > I'm considering getting a set of steppers with encoders - 6 NM peak > torque, drops to around 3 NM at 1,000 RPM according to datasheet. 3 NM > is peak on the DC motors I have - so the steppers will have more torque > around the speeds they'll likely be running much of the time. Matching > drivers from the motor manufacturer are also in the package, so are > motor and encoder cables. Cost for all that (used pulls from a > functioning machine) is about the same as a single old Servo Dynamics > SD1525-12 driver board. > > Better yet, they're much shorter length and weigh less than the DC > motors and the system only needs 115 volt AC so I can take the big > power supply out of the box, and I get the benefit of having the > encoders and the linear scales. I'll have room in the big box for a > phase converter for the spindle motor and everything else. I'm thinking > a mini-fridge is a possibility so I can keep a supply of Mountain Dew > Throwback handy... it's a really huge box. Or I could move the spindle > control relay components into it and get rid of that slightly less big > box. > > I'm a cheap scrounger and there's just no way I'm spending > multi-thousands getting my mill into working condition. :-) With > patience I will find the components at prices I'm willing to pay. If a > good SD1525-12 board dropped in my lap at a price I figure is decent > for a piece of quarter century old electronics, I'd grab it and stay > with the DC motors and the old drivers. That's why I snagged that one > motor for $299, because it matched the other table motor and was at a > sane price instead of being priced as if it was a rare antique vase. > > Then there's the 'little' issue where I have no idea if *any* of the > motors and electronics on the mill are good. There could be reasons > beyond the broken CRT and fried monitor power supply why this mill was > sidelined and cannibalized for parts. Buying less expensive, newer, > used motors and drives looks like a safer play to me. I'd lean in that direction too. For the same reasons. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! My views <http://www.armchairpatriot.com/What%20Has%20America%20Become.shtml> Things will get better despite our efforts to improve them. -- Will Rogers A pen in the hand of this president is far more dangerous than 200 million guns in the hands of law-abiding citizens. ------------------------------------------------------------------------------ Get 100% visibility into Java/.NET code with AppDynamics Lite! It's a free troubleshooting tool designed for production. Get down to code-level detail for bottlenecks, with <2% overhead. Download for free and get started troubleshooting in minutes. http://pubads.g.doubleclick.net/gampad/clk?id=48897031&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
