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Author Topic: Newbie question- using PM-DC motor as servo  (Read 5235 times)

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Re: Newbie question- using PM-DC motor as servo
« Reply #10 on: September 21, 2010, 11:40:15 PM »
Thanks Ray,
       I was hoping it could be done. I am still a bit concerned about the voltage limits of the gecko units though. They have a max voltage of 80, and these motors I have are 90 which isn't a great amount but if a treadmill motor were employed for spindle drive it would be 130. Does a person just have to sacrifice rpm at the top, or could the output of the geckodrive be fed to the voltage following inputs of a secondary motor drive like the KB units. I wonder how the Geckodrive is actually controlling motor speed and acceleration. If it is varying voltage then the voltage folower inputs of the kbsi 240d isolater could track that and send an appropriate signal for any motor controller to follow. If it is pulse width modulation that is taking place it might be a little trickier. Of course in any case a person would have to work out a method of reversing the motor since that part of the loop would be lost in translation between the gecko and the signal isolator. How much loss of efficiency would a person see using the gecko at its upper limit and just losing that top end voltage I wonder?
     Regards, Les ;D

Geckos are designed with a hefty safety margin (like 30%), so you can operate them up to their spec limits with no real worries.  The cheap treadmill motors are typically very high RPM (like 6000), which you won't be able to use. So, operating them, at reduced voltage will not really hurt you at all.  Geckos are current-limiting PWM drives, and they do a very good job of protecting themselves, unless pretty severely abused.  Heating of the motors is really not a concern, unless you operate them under heavy load for a long time.  Reduced voltage has no real bearing on motor temperature.  Even under heavy machining use, you will rarely be operating the motor anywhere near it's peak rating more than very briefly.

Regards,
Ray L.
Regards,
Ray L.