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Re: Sensorless back_emf speed controller
I downloaded the JAG Brushed motor software from Luminary micro to see what they are doing. After some looking, I found hbridge.c which shows how they control the gates. Looks like when a limit sw is activated , the high side gates are off and the low side gates correspond to either a coast or brake configuration. The coast has both low side gates off and the brake has both low side gates on. The limit sw is polled every interrupt so should be fast shutoff. For those that want to take a look, I am posting it here... I think this is ok since it has the copywrite headers on it.
Hardware:
The ckt doesn't seem to have voltage sense on the motor output terminals so I don't think they can read Back_emf as currently configured. I see a boost vsense but I think that only manages the boost voltage.
The inputs are 3.3v for the brake/coast and the limit switches. So would need to be careful when driving these with 5v Crio logic. The max voltage we can put into these ports is 5.5v and might be wise to use level shifting just in case of a slight over voltage. The level shifting would be needed for the brake/coast input. The limit switches have 3.3v pull-ups and are looking for a ground to pull them down. If Crio can be configured without a pull-up and be just a open collector might get away without level shifter.
Last edited by vamfun : 06-05-2009 at 16:26.
Reason: added content
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