Need to control 2 single axis brushed DC servo motors that require low currents?

[phil_prismtc]

I need to control two DC brushed servo motors that have the following specs:
0.1A running current and 0.5A peak current;
7-16V input.

I expect to use an NI FW-7344 with either a MID 7652 (min current is too high though) or a UMI-7772 but I am having trouble finding an amplifier to connect to the UMI.

Ideally, I would prefer a complete NI solution to avoid custom cabling issues etc.

Thanks in advance for syour submissions.

[ColinAE]

Hello.

Based on your motor specs I believe that the MID-7652 would actually be an acceptable drive. The stated specs:

• Peak current limit: 1.7 to 10A


• Continuous current limit: 0.8 to 5A

are for maximums, not minimums. For example, you could use the lowest setting (Cont. current 0.8, Peak 1.7) and the drive will be able to supply the necesarry current for the motors.

Feel free to give our tech reps a call too, and they can clarify any of these questions you may have!
Regards,
Colin C.
Applications Engineering

[ColinAE]

Hello all.

I want to apologize as my last post was definitely incorrect.

The way you use the current specifications is as follows: The Peak and Continuous Current specifications for the motor must be GREATER than the current specifications for the drive. If the motor has too low a current spec, then the drive will attempt to source too much current and will burn out the motor.

In this case, the motor will not be compatible with our MID-7652. You will need to look at a 3rd party drive with a UMI.

Again, I apologize for my error.

Regards,
Colin C.
Applications Engineering

[phil_prismtc]

Could the PWM output of the MID-7652 be used in conjunction with resistors (in parrallel and series) to dissipate some of the current? (I know it is lossy and may require a hest sink).

Cheers.

[Koninika]

Hello,
Using the PWM output in conjunction with resistors has not been tested and is not supported. How would you dissipate current and what would be the value of resistors that you use? All that would affect the motor. I would recommend using the drive that matches your motor.
Good luck with your application and have a good day!
Regards,
Koninika
Applications Engineer
National Instruments
http://www.ni.com/support

[phil_prismtc]

Which leads me back to my original problem. I can't find a suitable amplifier.