Subject:
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Re: moving in a straight line with two motors?
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 13 Nov 1998 20:09:14 GMT
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Original-From:
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Kekoa Proudfoot <kekoa@Graphics.Stanford.EDU>
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Viewed:
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2555 times
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> Obviously 00 is the state of the RCX when it is off. When it is on,
> the wheels are much harder to turn by hand. The RCX must default to
> state 11 when idle. Not all motor drivers support this, but this one
> does....
This all depends. The table you gave (presumably from the date sheet), said:
> The data sheet confirmed something else that I thought was happening...:
> In1 In2
> 1 0 Forward turning
> 0 1 Backward turning in opposite direction
> 1 1 Brake motor is shorted
> 0 0 Off motor is disabled
Now, Lego uses Off to mean Brake and Float to Off ...
> That means that there is no coast mode, the RCX starts
> electromagnetically braking as soon as the motor is turned off.
Well, you can set the motor to "float" and you do coast.
> Also, there is constant current leakage whenever there are motors attached.
> Should be pretty low if the motor is not moving, but should climb a
> LOT if the motor is driven by some mechanical force.
Please explain why there is necessarily leakage current when the motor is
shorted. I can see there being very little leakage current if the CMOS is
done right, but I haven't reviewed the circuit diagram on the data sheet
recently, so I'm not sure if this is the case with the chip in the RCX.
> So, is there any way to disable a motor port in firmware, without
> disconnecting the motor physically? Could be useful for long running
> battery powered robots that do not need the motors moving all the
> time.
You mean is there a way to set them to float? Of course. Is there a
dedicated pin on the RCX to physically stop power from going to the motors,
aside from setting them to float? Unknown at the moment.
-Kekoa
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Message has 1 Reply:
Message is in Reply To:
 | | Re: moving in a straight line with two motors?
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| (...) kp> There needs to be a link to this somewhere: kp> Peter Phillips pointed out a long while back (my messages from him are kp> dated Sep 21) that the specs to the chip are here: (...) kp> drivers. OK, 500mA per driver. Which, if the rest of my (...) (26 years ago, 13-Nov-98, to lugnet.robotics)
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