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#16
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Re: Victor Brakes
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#17
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Re: Victor Brakes
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#18
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Re: Victor Brakes
Hmm, assuming you had the braking feature of the victor hooked up to an IO pin, do you think a pulsed variable breaking system similar to ABS would provide varied levels of braking?
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#19
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Re: Victor Brakes
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The speed controllers have this feature built in but using a slightly different method. The current supplied by the motor used as a generator is dumped into the transistors in the controller which are acting as a short. The controller is an "H" bridge design. Imagine the "H" with the motor connected from the center of the left vertical to the center of the right vertical. The top and bottom of each vertical is a set of power MOSFETs. The top of both upper vertical bars are connected to the positive battery connector and the bottom of both lower verticals is connected to the negative battery connector. To turn the motor on in one direction, the transistors in the upper left and lower right corners are turned on. To reverse the direction of the motor, the upper right and lower left transistors are turned on. To vary speed, you add a switching waveform to turn the transistors on and off, with speed determined by the ratio of the ON time to OFF. To provide braking, turn ON both of the bottom sets of transistors. Since they are both connected to the negative battery terminal, they are shorted together and that produces a short across the motor. By varying the pulse that enables the brake you could vary the braking force. As pointed out by others in this thread, the braking is dependent on rotation. The slower the motor is turning, the less current is being developed in the motor, and the less effective the braking becomes. |
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#20
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Re: Victor Brakes
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Also note that the braking feature of a Victor is not all that powerful, since it is proportional to the motor speed. So, it would not be a good brake. Don |
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#21
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Re: Victor Brakes
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#22
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Re: Victor Brakes
When I tried hooking the SIGNAL pin of a Digital Output directly to the centre pin of the Victor Brake/Coast header (2006 Robot Controller) the red HARDWARE LED comes on (Master Reset), on the Robot Controller.
This can't be good Shouldn't the Relay Outputs on the Robot Controller be used instead??? I have been unable to find a schematic for the Victor controller showing the Brake/Coast jumper. |
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#23
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Re: Victor Brakes
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#24
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Re: Victor Brakes
Sorry, I misread it.
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#25
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Re: Victor Brakes
In my experience, that red light usually means something is drawing too much current from the RC's +5v output. Are you absolutely certain you got the connection the way you intend it to be? Might your connector be faulty and have a short between signal and ground? Did you perhaps accidentally also connect the +5 from the digital header to the ground (I think it's the Coast end, but I might have that backwards) on the Victor?
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#26
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Re: Victor Brakes
Thanks Alan.
It is either something like that, or a short somehow via the chassis (unlikely - but I will be checking it). Last night we did try using the Relay Out ports, which seem to work. However the rules state that only the Digital Output can be used. We modified a standard servo cable so that it has one end normal (at the RC) and the other (at the Victor) routes the white (SIGNAL) wire to the centre conductor. The black and red servo wires are not connected to anything. This assumes that the PWM cable going to the Victor supplies the ground return - however since I cannot find a schematic for the Victor (or the RC for that matter), I don't know if this is correct. But IFI Robotics FAQ for the Victors does state: Quote:
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#27
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Re: Victor Brakes
mluckham,
I would check the operation of your wiring by removing the brake connection at the Victor and checking it with a VOM. It should not have voltage and should read a short to ground when Low and open circuit when High. You might be one pin off on the RC and feeding +5 volts to the jumper. |
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#28
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Re: Victor Brakes
If you are referring to the digital output from the RC, it will actually output 5V when high and ground when low. We used it in this configuration last year.
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#29
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Re: Victor Brakes
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I thought this was not an active high. So if it is disconnected from the Victor, there is no pull up. |
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#30
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Re: Victor Brakes
No, it's just a standard digital output on the RC. When set to high it outputs 5V and when low it shorts to ground.
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