How to change current on MID7654/7652

[ChandlerChin]

Hi 

I am trying to use MID-7654/7652 to drive my servo motor with the motion controller. However, the smallest output current I can get from the driver is 0.85A which is way too high for my motor. The unloaded current for my motor is 0.01A, when I use it with the driver it gets really hot in 1 sec, so I am thinking it is due to the high voltage and current. So I am not sure if there is a way to change the current/Voltage on the driver to lower number.\

Thanks!

[Smootastic]

Hi ChandlerChin,

How do you have your connections set up?  The 0.85 A is continuous current limit (max) not a minimum value like you thought.  Are you using any custom cabling?  Refer to the User Guide for this drive for more information on the connections.

[ChandlerChin]

Hi

according to the user guide P.11 and P.12 using the DIP switch to change the current output on Axis-1. From the user guide, the default current is 0.85A and the default Peak current is 1.7, so I am not sure is there any way I can change the current to a smaller value? Thanks.

Chandler

[ChandlerChin]

Here is the spec for the motor and encoder I am using. Thanks

[AnalogKid2DigitalMan]

Does your motor just have 2 wires going to it? I do not believe the model you posted a link to is a servo.

-AK2DM

[ChandlerChin]

There are two links, one is for the motor and one is for the encoder. On the second link, there is a pin assignment for it on the first page. Right now the servo motor is able to work in series with a 250Ohm resistor, but the problem is that the resistor will get hot in quite a short time. So if it is possible that we can just change the output voltage then we don't need to think about the heat problem. Thanks

[Smootastic]

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@ChandlerChin wrote:

Hi

according to the user guide P.11 and P.12 using the DIP switch to change the current output on Axis-1. From the user guide, the default current is 0.85A and the default Peak current is 1.7, so I am not sure is there any way I can change the current to a smaller value? Thanks.

Chandler

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If you read page 10, the Continuous and Peak Currents are maximum current values that your motor can withstand, so it should be ok.  Can you double check the wiring on the Rear of the Drive (Pages 14-16).  

What are the output ranges of your AO signals?  +/- 10 V is to correspond to the maximum current limits (Page 10).

[Jochen]

What type of motion control board are you using? If you are using an NI 73xx motion control board you can limit the output voltage of the board's analog outputs. The AO voltage is proportional to the current driven by the MID, so limiting the AO voltage effectively limits the motor current.

Kind regards,

Jochen

[ChandlerChin]

I am using PXI-7340 as the Motion Controller and MID-7654/7652 as the motor driver. I have tried to limit the ADC voltage but did not either. No matter what value I changed, when I use a voltage meter to measure the motor+ and motor- it always give me a reading around 48V. 😞

[Jochen]

The MID-765x outputs a 48 V PWM signal. There is no way to limit the output voltage, but you can limit the output current by limiting the motion control board's output voltage, which effectively limits the drive's PWM duty cycle.

Please refer to page 10 and 11 in the MID-765x user manual for more detailed information.

Jochen