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 10:44:08 GMT
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Viewed:
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10029 times
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In lugnet.robotics, Brian Davis wrote:
> In lugnet.robotics, Rob Hendrix wrote:
>
> > And more specifically, here's a working solar RCX robot rover:
> > http://home.earthlink.net/~stuff.tm/solarlego/index.html
>
> This last, BTW, was the URL I was going to contribute. It's a good clean site
> presentation, of a very novel hack to the RCX. Note that while he used non-LEGO
> technology (the LEGO solar cells, while robust, have a really poor
> power-to-weight ratio, and his "energy can" beats the pants off batteries for
> this sort of thing), he's made it all nicely LEGO-clad. And while I'd love to
> see this done on the NXT or PF platforms, I suspect that the RCX-based approach
> is at this point more viable. The PF & NXT motors are current hogs, with much
> higher weight and lower efficiency than the old RCX-era gear motors.. again,
> that power-to-weight ratio is going to drive a lot of things.
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 playing with
this from the software point of view. I have to search in my many files: we once
wrote a firmware that disabled any peripherical device, just keeping the RAM
under voltage -not to loose the program- like in sleep-mode and before that,
move a portion of program to the H8/3292 on-chip RAM, run it there, which keeps
alive the microcontroller and through a certain timing, shortly relaunch the
system, check the battery-status and decide what next. We could reduce the
consumption to a few mA, if my memory doesn't leave me.
3. As to the sleep mode, only the non-maskable interrupts can awake the RCX:
watchdog-timer and button interrupts. The hack of the link you mention is an
interesting idea. However we'll play with the watchdog-timer solution first
before hacking the RCX.
3. Justin Fisher's thermal fuse is a good idea for security.
4. However, his battery-charging doesn't convince me. With our rover, we just
can use 2 LEGO solar panels. The voltage is rather constant, independently of
the light intensity: about 2..3V per panel. The current is weak with artificial
light(30mA..50mA). Even if we place the panels in series, the voltage won't be
sufficient for recharging. So, the idea is to add some electronics to provide
constant recharge-voltage for the batteries. The current then of course is
variable, depending on the light intensity. I only wonder how to realize a
voltage DC-converter with these features. What is the optimal recharge voltage
for NiMH batteries? I'm currently scanning my library for sample circuits having
in mind a device with a coil and a microcontroller that is regulating the
interruption of the primary circuit.
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Message has 1 Reply:
 | | Re: Mars mission IV
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| (...) That sounds wonderful, although well beyond what I can do (which is why I love reading your projects & posts). (...) Which sounds good, although ultimately I worry about what happens when the power drops really low, and the watchdog timer (...) (16 years ago, 11-Mar-08, to lugnet.robotics)
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Message is in Reply To:
| | Re: Mars mission IV
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| (...) presentation, of a very novel hack to the RCX. Note that while he used non-LEGO technology (the LEGO solar cells, while robust, have a really poor power-to-weight ratio, and his "energy can" beats the pants off batteries for this sort of (...) (16 years ago, 10-Mar-08, to lugnet.robotics)
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