servo help..turmite?

[senor J.]

has anyone used these servos with gecko drives? ebay item# 3843488086 (just paste that number into the ebay search and it will go to the auction) I think turmite may have used these? the guy selling them on ebay says they are rated at 120 volts but he says that you can get away with less than that ie. the 80 volt limit on the geckos. Im curious how they perform with less voltage. thanks

[ESjaavik]

They will go slower.
The output power will be less (Power = Torque * Speed).
They will be heavier that a motor with the same power but designed for your voltage.

The price may be right if the motors are just perfect for your application, which it seems they are not. If you use 80V bus voltage, look for motors rated at around 60V or lower.

[senor J.]

thanks for the reply
Is torque related to amps or volts? what I mean is lets say the motor is rated at 120 volts 20 amp and lets say that makes 670 oz/in of torque and spins the shaft at 1200rpm. Now if you reduce the volts to 80 but keep the amps at 20 are you gonna get more or less the same torque just at a lower rpm?

[ESjaavik]

Basically yes. Generated torque is proportional to current (in Ampere). Output torque at the shaft will be somewhat less than predicted at increasing speed due to internal drag and electric losses.

And speed (RPM) is proportional to voltage. The same applies here, at higher speeds there will be some losses. So it's not linear ad infinitum.

Below rated speed for all practical purposes you can regard output torque and speed to be directly proportional to current and voltage. Above that the losses will get into play. So will electric factors related to the fact that the motor have coils, and thus have an inductance. And.... Well let's say it's best to keep below rated isn't it?

[ESjaavik]

And you'd better scrap that motor!
It eats 2400 Watt, and give you about 570 Watt at the output shaft.
The remaining 1830 Watt it returns as heat. A good heater, but a lousy motor.

[turmite]

senorj sorry about the absence. Lots of family sickness. I have 3 of the motors but have never hooked them up so I can't be of much use to you.

Mike

[happytriger2000]

Senor J

I have 3 gecko 320, and Im also looking for motor for the drivers, have you finished wiring up?

Freeman

[senor J.]

hello, Yes I did finsh wiring up and they run great. I am using a direct drive on 8tpi acme lead screw with delrin nuts. my current lead screw set up has a lot of friction and so even by hand the screws are tight to turn but even so the motors run them well. I can cut at about 120 ipm right now and I think I should be able to cut around 150 with ball screws The rapids are limited to the rpm of the motors which are around 1100 rpm so direct drive works the best. You can get a really good power supply here.. http://www.surplussales.com/Transformers/HvLvTr-5.html
It will rectify up to 75 vdc~
and finally just so you have an idea of what they can push my machine is made entirely of steel the y axis weights aproxamately 150 maybe more.
I put my own encoders from us digital I used the E2 250cpr encoder with the screw down wing style they worked wonderfully because the motors already come with the screw holes for that type and size. The guy on ebay sells agilent encoders with the motors but I think you have to have a seperate power supply for those because the geckos are limited to a 5 volt encoder power signal. One very good reason to just get the motors and put the US digital encoders on them. One more thing dont pay his asking price if you just want the motors. I offered him 100 per motor outside of ebay and he settled for 110. maybe he might do that again.

[happytriger2000]

senor J

Thanks for your reply.

Im starting to build my first cnc machine, and my electronic skill is not good, so just wondering if you can post a photo of your G320, the motor, and the encoder wiring?
I know how stepper motor works, and now Im learning how to use servo, so I'll appreciate for your support.

Thanks

Freeman