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Author Topic: Use motor out of a digital servo  (Read 606 times)

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Offline drbTopic starter

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Use motor out of a digital servo
« on: November 04, 2010, 08:33:38 AM »
I have a Hitech digital servo that is fried.  With an analog servo I know I can connect the leads of the motor to a motor controller and use it as a DC gearbox type of motor.  Can I do the same thing with a digital servo?

Here is what I tried:

I cut the leads to the digital servo motor and connected them to a power supply.  The motor runs, but draws a lot of current (around 6 amps) with no load.  The manufacturer's specs for the digital servo is that the typical no load current draw will be around 400 mA.

Offline Soeren

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Re: Use motor out of a digital servo
« Reply #1 on: November 06, 2010, 11:46:36 PM »
Hi,

Can I do the same thing with a digital servo?
Yes.


I cut the leads to the digital servo motor and connected them to a power supply.  The motor runs, but draws a lot of current (around 6 amps) with no load.  The manufacturer's specs for the digital servo is that the typical no load current draw will be around 400 mA.
If you have a working servo, measure the draw of that one the same way and/or the voltage that the internal controller puts out to the motor.

What voltage did you test the motor with?

Perhaps try to lower the voltage until it shows close to the 400mA mark and find the voltage needed that way.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline drbTopic starter

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Re: Use motor out of a digital servo
« Reply #2 on: November 09, 2010, 09:33:34 AM »
I don't have a good one to try only another bad one.  Both bad motors measure the same resistance and draw approximately the same current when connected up to a 5 VDC source.  I figured it was unlikey that two motors failed in exactly the same way. 

Offline Soeren

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Re: Use motor out of a digital servo
« Reply #3 on: November 09, 2010, 06:28:30 PM »
Hi,

I figured it was unlikey that two motors failed in exactly the same way. 
Why, was it two different persons ruining them in two very different scenarios?  ;)

You can be pretty sure that the H-bridge in a servo has a voltage drop and perhaps there's a sense resistor dropping some too and a digital servo runs at a higher update frequency internally, so it's a safe bet that the motor doesn't see 5V - try a lower voltage, the motor is most likely OK.

Was it perhaps coreless servos?
While it's close to being a crime smoking a coreless, it would explain the high current.

Well, lower the voltage! Perhaps start from around half a volt and work your way up to the 400mA or whatever it can take without getting too hot.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

 


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