Subject:
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Re: Mars mission IV
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 11 Mar 2008 15:01:50 GMT
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Viewed:
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11755 times
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In lugnet.robotics, Claude Baumann wrote:
> 2. I think that the RCX firmware should survey
> the battery status and more and more disable
> current-intensive functions... We could reduce
> the consumption to a few mA, if my memory doesn't
> leave me.
That sounds wonderful, although well beyond what I can do (which is why I
love reading your projects & posts).
> 3. As to the sleep mode, only the non-maskable
> interrupts can awake the RCX... we'll play with
> the watchdog-timer solution first...
Which sounds good, although ultimately I worry about what happens when the
power drops really low, and the watchdog timer keeps powering the system up to
check the power, draining it down faster than a power-controlled system would.
But I completely agree with applying the SW hack before the HW hack in this
case.
> 4. However, his battery-charging doesn't convince me.
> With our rover, we just can use 2 LEGO solar panels.
I's disagree, for a number of reasons. The LEGO solar cells are not great
efficiency, and even for their area are rather heavy, which means powering the
motors to move them will "cost" more. Notice it's not that a LEGO rover powered
by two stock LEGO solar cells isn't possible - it's just that using the lower
efficiency cells, coupled with the greater weight, implies even more time
recharging (sitting still) than moving. It comes down not to power management,
but power to weight... and both the LEGO solar cells (high weight, with low
efficiency) and batteries (high weight and *very* poor efficiency during
charging... notice how hot batteries get while charging... plus poor response
time to short transient power pulses from the panels) and poor in this regard.
Shuffling between voltage and current doesn't change the fact that what you
get out of a solar cell is power (current times voltage)... and worse,
converting & conditioning that power induces loosing some as well.
--
Brian Davis
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Message has 1 Reply:
Message is in Reply To:
 | | Re: Mars mission IV
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| (...) Interesting approach. Good arguments. 1. The RCX is the device of our choice for this project. 2. I think that the RCX firmware should survey the battery status and more and more disable current-intensive functions. I remember that we were (...) (17 years ago, 11-Mar-08, to lugnet.robotics)
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