Brake connection on AX3500

14 years 2 months ago #12081069 by Sonya
Brake connection on AX3500 was created by Sonya
Hello all,

I am developing a number of prototypes based on mobility chair bases. One of the first things we want to hear before motors are powered up is the "clunck" of those em brakes disengaging.

The AX3500 manual mentions an auxiliary output specifically for brakes but I can find no mention of its actual physical whereabouts on the board or its operation only that there is no brake/coast option implemented at this time.

Maybe I've missed something but if someone could give me a couple pointers I would appreciate it,

TIA

Sonya

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14 years 2 months ago #12082051 by cosma
Replied by cosma on topic Re:Brake connection on AX3500
<P style="MARGIN: 0px">This feature is supported in a beta version of the software that we can make available to you upon request.
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<P style="MARGIN: 0px">The function uses output C which gets activated whenever power goes out to any motor.
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14 years 2 months ago #12082971 by jcweber
Replied by jcweber on topic Re:Brake connection on AX3500

<FONT face="arial, helvetica, sans-serif">I Was wondering about this as well. I noticed that there are two output C's (pins 1 and 9, the brake output) on the 15 pin connector. Does this mean that there is a brake pin for each channel working independently of each other? Because my robots work on the skid steer principle and when one drive is stopped and the other is moving the drive that is stopped will coast if the brake isn't on resulting in a poor turn. And then the reverse happens for turning the other way. Will beta ver be released to all in the future?</FONT>

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14 years 2 months ago #12084124 by cosma
Replied by cosma on topic Re:Brake connection on AX3500

There is only one output. Pins 9 and 15 are connected to the same transistor.
<P style="MARGIN: 0px">So the output activates to release the brakes on both motors as soon as power is &lt;&gt; 0 on either motor.
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<P style="MARGIN: 0px">It would have been preferable to have one output for each motor but this appears to be an acceptable compromise for many users we've talked to.
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14 years 2 months ago #12105342 by Sonya
Replied by Sonya on topic Re:Brake connection on AX3500
Thanks, Cosma, for your expedient reply.

I was wondering if code for disengaging the brakes in the beta software you mentioned contains a slight delay between the time the brake is disengaged and the motors are powered or is there a ramp up period ? I would think doing something like simultaneously disengaging the brake and giving full power to the motors would produce quite a spike as the motor would essentially be stalled for the brief period of time from when the brakes are energized until fully disengaged.

Also do the acceleration ramp up configurations apply to serial commands to run the motors or would this fall under the jurisdiction of code external to the board?

TIA,
Sonya

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14 years 2 months ago #12106451 by cosma
Replied by cosma on topic Re:Brake connection on AX3500
<P style="MARGIN: 0px">There is no delay from the time the output is energized to the time the motors are getting power.
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<P style="MARGIN: 0px">However, when power is applied to a stopped motor, the current grows gradually (the higher the motor inductance, the longer). Also, you can play with the acceleration parameter to make sure that power is not applied all at once to the motors. So unless your brake are very slow to release, this will work fine.
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<P style="MARGIN: 0px">The programmable acceleration applies to all operating modes.
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<P style="MARGIN: 0px">Keep in mind that the output C has only limited drive capability (~1A max), so you may need to add an external relay if you need more current for your brakes. This will slow down a bit the release of the brake if a mechanical relay is used but this should not make a significant difference.
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