Mars mission IV

[Claude Baumann]

We are currently (and urgently) working on a new edition of our Mars mission
project (http://www.convict.lu/Jeunes/Mars/breaking_news.htm). The idea is to
start from our former RCX experiences and add some new features this time. We
are designing the rover in traditional stud-technology with the RCX.

(Why not NXT? Our issues are: if ever we have to hack a control-brick, better do
it with an RCX; we haven't the time for long-time tests, so we need to rely on
our previous experiences).

The rover has already been designed as a kind of Rocker-bogie suspension. I'll
soon post some pictures to our web-site.

The ultimative challenge seems to be the fully autonomous robot that also
recharges its batteries with solar panels. I'm not sure this can be done with
the LEGO solar panels. My questions now turn around the circuitry that is
necessary to use the panels to charge 6 NiMH batteries. Probably we'd need a
pump circuit with a coil and a pulse control. Has anyone got more reliable data
about the solar panels? What about the gold capacitor? Has anyone an idea how to
design such a circuitry? is this a realistic challenge? How far can the RCX
power consumption be reduced?...

Are there interested people to help me design this?

-Claude

[Rob Hendrix-2]

"Claude Baumann" <cbaumann@...> wrote in message
news:JxIys1.HME@......

> We are currently (and urgently) working on a new edition of our Mars
> mission
> project (http://www.convict.lu/Jeunes/Mars/breaking_news.htm). The idea is
> to
> start from our former RCX experiences and add some new features this time.
> We
> are designing the rover in traditional stud-technology with the RCX.
>
> (Why not NXT? Our issues are: if ever we have to hack a control-brick,
> better do
> it with an RCX; we haven't the time for long-time tests, so we need to
> rely on
> our previous experiences).
>
> The rover has already been designed as a kind of Rocker-bogie suspension.
> I'll
> soon post some pictures to our web-site.
>
> The ultimative challenge seems to be the fully autonomous robot that also
> recharges its batteries with solar panels. I'm not sure this can be done
> with
> the LEGO solar panels. My questions now turn around the circuitry that is
> necessary to use the panels to charge 6 NiMH batteries. Probably we'd need
> a
> pump circuit with a coil and a pulse control. Has anyone got more reliable
> data
> about the solar panels? What about the gold capacitor? Has anyone an idea
> how to
> design such a circuitry? is this a realistic challenge? How far can the
> RCX
> power consumption be reduced?...
>
> Are there interested people to help me design this?
>
> -Claude

Solar Cell / RCX info -

From the LEGO site:
http://www.lego.com/eng/service/faqs.asp?section=ConsumerService-FAQ-TechSupport&catid=87BC4CA6-D8CD-4BF1-8307-6B52AB45AF02&faqid=1725&tech=true

"  What are the specs on the LEGO Solar Cell and Capacitor?
 The LEGO Solar Cell and Capacitor are designed to be used with the LEGO
Educational Division set, but can be used with the Robotics Invention
System. The Solar Cell supplies 3V, 200mA in full sun outdoors, and 3V,
100mA in full sun through a window. You can connect the solar cell to power
a LEGO motor, but the motors require 9 volts to operate at full strength.

For more information on the LEGO Solar Cell and Capacitor, please visit the
LEGO Dacta site at http://www.lego.com/dacta/hardware/solarcell.asp"

-----------------------------------------------

Some more helpful info from Lugnet:
http://news.lugnet.com/robotics/?n=16142&t=f&v=a

Some more recent info involving an NXT from nxtasy.org:
http://forums.nxtasy.org/lofiversion/index.php?t385.html

And more specifically, here's a working solar RCX robot rover:
http://home.earthlink.net/~stuff.tm/solarlego/index.html

Good luck!

-Rob
www.lifelites.com
www.brickmodder.net

[Brian Davis-3]

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.

--
Brian Davis

[Juan Antonio BreñaMoral, JAB]

Hi, Claude Baumann, I would like to collaborate with you.

I am very interesting in Rover projects.

Juan Antonio Breña Moral
www.juanantonio.info

[Claude Baumann]

Thanks

In lugnet.robotics, Rob Hendrix wrote:
>
> "Claude Baumann" <cbaumann@...> wrote in message
> news:JxIys1.HME@......
>> We are currently (and urgently) working on a new edition of our Mars
>> mission
>> project (http://www.convict.lu/Jeunes/Mars/breaking_news.htm). The idea is
>> to
//snip

[Claude Baumann]

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.

[Claude Baumann]

In lugnet.robotics, Juan Antonio BreñaMoral, JAB <tsp44@...> wrote:
>
> Hi, Claude Baumann, I would like to collaborate with you.
>
> I am very interesting in Rover projects.
>
> Juan Antonio Breña Moral
> www.juanantonio.info

You're welcome

[Brian Davis-3]

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

[Claude Baumann]

../snip>
>    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.

Please consult http://www.convict.lu/htm/rob/mars_IV.htm. I propose to do the
discussions in this forum.

[Claude Baumann]

Question to H8/3292 specialists (Kekoa Proudfoot, Michael Anderson, Markus Noga,
Ralph Hempel, John Hansen, Dick Swan ... these are the ones I know, ... are
there others... probably?)

I tried to plunge the RCX into sleep mode (not the normal RCX software stand-by
mode), which, according to the datasheet, halts the CPU, but keeps on running
the clock. The hardware manual explains that the H8/3292 can be exited from this
state through an internal or external interrupt.

But, I was not able, after several tests of doing this. I first cleared the 7th
bit of SYSCR, then configured an interrupt, added a dummy interrupt service
routine, finally called "SLEEP". The current dissipation corresponds to the one
noted in the datasheet, but none of the interrupts -neither external, nor
internal, woke-up the RCX. Has anyone got an idea, what I might be doing wrong
here? Am I missing a configuration sequence? Is there a special timing that
needs to be respected?

This is quite intriguing, because it should work according to the datasheet.

http://www.convict.lu/htm/rob/mars_IV.htm 

[Claude Baumann]

In lugnet.robotics, Claude Baumann wrote:

> Question to H8/3292 specialists (Kekoa Proudfoot, Michael Anderson, Markus Noga,
> Ralph Hempel, John Hansen, Dick Swan ... these are the ones I know, ... are
> there others... probably?)
>
> I tried to plunge the RCX into sleep mode (not the normal RCX software stand-by
> mode), which, according to the datasheet, halts the CPU, but keeps on running
> the clock. The hardware manual explains that the H8/3292 can be exited from this
> state through an internal or external interrupt.
>
> But, I was not able, after several tests of doing this. I first cleared the 7th
> bit of SYSCR, then configured an interrupt, added a dummy interrupt service
> routine, finally called "SLEEP". The current dissipation corresponds to the one
> noted in the datasheet, but none of the interrupts -neither external, nor
> internal, woke-up the RCX. Has anyone got an idea, what I might be doing wrong
> here? Am I missing a configuration sequence? Is there a special timing that
> needs to be respected?
>
> This is quite intriguing, because it should work according to the datasheet.
>
> http://www.convict.lu/htm/rob/mars_IV.htm

Perhaps it's not the best habitude to answer one's own post, but the good news
is that we were able to fix the problem:

The issue was that we were using the Assembler code

bclr #7,@0xFFC4

in order to select sleep mode instead of software stand-by mode. We already had
troubles with direct bit setting or clearing with other microcontrollers.
Sometimes the hardware requires that certain registers are first read and then
set. This also is the case with the SYSCR register of the H8/3292. So, we used
the following code instead:

mov.b @0xffc4:8,r6L
and #0x7F,r6L
mov.b r6L,@0xffc4:8

==> And everything works now. We already tested the NMI-interrupt that is
generated through the watchdog timer overflow and IRQ0 interrupt that is
produced through the RUN-button pressed.

[Philippe Hurbain]

In lugnet.robotics, Claude Baumann wrote:
> ../snip>
>>    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.
>
> Please consult http://www.convict.lu/htm/rob/mars_IV.htm. I propose to do the
> discussions in this forum.

Hi Claude,

If you need to model your rover, I just LDrawed the solar panel and the
supercap...

<http://www.ldraw.org/cgi-bin/ptdetail.cgi?f=parts/32342c01.dat
<http://www.ldraw.org/library/unofficial/images/parts//32342c01.png>>

<http://www.ldraw.org/cgi-bin/ptdetail.cgi?f=parts/32339c01.dat
<http://www.ldraw.org/library/unofficial/images/parts//32339c01.png>>

Philo

[Claude Baumann]

In lugnet.robotics, Philippe Hurbain wrote:

> Hi Claude,
>
> If you need to model your rover, I just LDrawed the solar panel and the
> supercap...
>
>  Philo

Hi Philo, this is amazing. Thanks a lot.

[Rich Diaz-2]

Hi,

I need two RCX battery trays (the green part)

anyone have any idea where I can get them?

Many thanks!

Rich


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[Rich Diaz-2]

I've been away a long while.

How are RCXs currenlty programmed? I used a C type
program before and I liked it a lot, is that still
used?

Also, is there a good central site for RCX bot builds?

Thanks!
Rich


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