MLW sub $500 robot

Hey MLW, What's the URL for your website again? I downloaded your code and can't figure out where I got it now.
Meant to mention this...
the OAP project has a WIKI site where those of us who are building robots either based on the project or like the OAP bot can post and keep in touch with each other.
For those of you not familiar... oap.sourceforge.net is the Open Automaton Project or how to build your own robot base with electronics...
It's based on PICs and all tied together with a Linux based micro PC board. Complete plans and schematics are provided on line and suggested software to run on the pc (Linux)..
Eljin
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Eljin wrote:

www.linuxpcrobot.org

Yea, I'm thinking of setting that up, but I've so many projects going on I'm swamped.

The OAP project is very cool.
I took a different route. I'm in the process of moving stuff to the 2.6 kernel, and am using the 2.6 serio driver instead of the 2.4 psaux driver. The Linux 2.6 kernel moves mouse stuff into the kernel under the "input" driver model. It is a great idea for desktop stuff, but a little limited in user space.
In dealing with the mouse issues, I've also been experimenting with the mouse resolution. Most mice have a resolution setting 1:1, 2:1, 4:1, 8:1 the higher the resolution the better precision at lower speeds. At higher speeds it becomes more likely that you will overflow the counter. I've also been testing if all the various scale settings return real counts or if they just accelerate them. A lot of turning motors by hand.
While I was redoing the code to interface with the mouse, I am also trying to modularize the internals a bit more so that when I dump the Veleman board, I won't have to deal with many suprises.
But, back on topic, any questions about the code?
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mlw wrote:

None at the moment. Still building electronics for the base. I have to build a PIC programmer and just haven't gotten that far yet.
I'm hoping to post some pictures and information soon to the wiki.
I started to go the same route as you, but wanted to leave more overhead on my main board for higher functions. I won't be able to afford a bleeding leading edge mother board for a while yet, so I'll be using a 233MHz Pentium board I'm salvaging from one of my previous PCs.
What I meant for you to do was post to the OAP wiki. It's open to modifications to the base design and I really think you have some good ideas that would be helpful to the small, but growing community there. Also, instead of reinventing the wheel, I thought you might be able to get something out of the OAP design.
I chose to go the OAP route, because it reminded me of the old Heathkit Hero platform. I'm even going to be adding an arm or two to my unit after I get a few more levels built up and am hoping to use your parallel port option for that. I'm going to try and tie the kinematics of the arm motions with the vision system after I do upgrade my main board. I've seen it done on a couple of University level bots and the results looked promising.
There is an alternative to the parallel port even. Boondog Automation has the schematics for a motion control card that plugs into the main board itself. It provides timing and resolution, so you don't have to use so much code space to create the same affect and you don't have to use up one of the precious ports on a pc main board. I like that since my I2C bus is currently having to reside on my parallel port.
Matter of fact that was the reason I was asking a few weeks ago about any implementations of I2C from USB or Serial ports that have Linux drivers. Know of anything like that?
See ya, Eljin
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Eljin wrote:

No thanks, silly rabbit, everyone knows PICs are for kids :)

Cool. If you want, I can add a space on linuxpcrobot.org for you.

233MHZ pentium, wow!! I haven't worked on one of those since my Metrabyte days. If it helps, I'm only using a 800MHZ EPIA.

I looked at the OAP design, and think it is "a" way to go, but not what I'm looking to do.
The sub $500 will not have user developed micro-controller code, period. If there are peripherals, like video cards, keyboards, etc. then that's fine, but the end-user programmability is at the PC level. It is a core design goal.

Cool, I'm sure everyone wants to see that and source of course.

I'm not worried about timing or "code space" for the main motor control system, it is trivial in both respects.

The 2.6 kernel has a whole I2C subsystem and drivers for a lot of chips. It looks very cool.
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I like it. But I have a few questions.
You don't mention what kind of battery you are using. It looks like there is one in the bottom of the robot in the pictures. What did you use? It looks a little like a motorcycle battery (or 3 6v?).
How long can the battery(ies) run the bot if it is moving constantly and how long can it run the bot if the thing is not moving and not sleeping but acting like a Linux PC?
Does an 800Mhz motherboard require a fan? Will it be ok if you cover the sides or the robot instead of it being an open rack?
Best Wishes
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snipped-for-privacy@ultratechnology.com wrote:

Thanks.

Right now I am using a gel type lead acid deep cycle battery commonly used by fire alarms and UPS systems. (12V)
The "best" consumer battery with regards to power density and weight is NiMH batteries, unfortunately, they are sort of expensive. If I can find a source of cheap NiMH I will switch.

I haven't done too much timing on the system, but I've left it on for about 10 hours not moving and not using the wireless ethernet system.

Unfortunately the 800MHZ board that I have does need a fan, though I bet I could put a big-ass heat sink on it and get rid of the fan. I think the newer 800MHZ boards can be fanless.
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NiMH
I'm using sub-c cell packs of NiMH. Did you take a look at maxamps.com? That's the best place I found to buy quality GP NiMH cells and accessories. I bought individual cells, so I can wire them as I need (electrically and mechanically speaking). The only problem is that it is really tricky to solder the batteries together, and some people even reccomend not to solder at all, but I'll try either way. I've researched LiPo, but that's really expensive...

You are correct on that. At least the newest ones from VIA (EPIA) at this speed do not require a fan, but we always have to keep in mind that our circunstances are a little bit different. If your robot is meant to work outdoors, you will have to take in consideration environment temperature. (what if your robot is meant to cross the desert on the summer peak?)
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Padu wrote:

Yea, they are really pricy. Take a look here: http://www.all-battery.com/index.asp?PageAction=VIEWCATS&Category 
20 3300mAH SUBC batteries for $50, thats $2.50 each.
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID@&HS=1
8 5000mAH NiMH C batteries, 21.95, that's about $2.75

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I had seen those sites before, I was very tempted to buy those cheaper ones, but when speaking about batteries, brand quality really makes a difference. From what I know, Sanyo and GP are the ones that make real quality batteries. If you are planning to use it a few times, I don't think there will be any difference, but after a couple recharges the cheaper ones won't hold a charge as they used to when new.
It is amazing how everything electronics evolved really fast, and batteries evolved much slower compared to everything else. (ok, very vague, but you got the idea)
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Padu wrote:

I am skeptical of quality claims from manufacturors, there is typically no real difference between a named brand battery and a generic one. (Often times they are made in the same fctory) The chemical process is the same for similar technologies, so I'm not sure how one can be better than another without being defective.

IMHO batteries are all wrong. Electro-chemical power storage is ancient technology. When we need is a super insulator to make long term electrical storage an electrostatic technology.
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Fact is when I put a pack of no-name batteries on my RC car, after a couple of months the run time decreases significantly (let's say from 15 to 6 minutes) while when I use a GP pack, it decreases to only 12 or 13 minutes. I need to perform more scientific experiments, but I have the clear impression that GP's give more punch, given the same mAh ratings. (I charge them at the same rate)
If you browse through some RC forums, you will see people telling the same stories.

They may use the same process, but maybe using cheaper components, and being "at the edge" of being deffective...
I work for a telephony equipment company, and we constantly have to quote on different parts from different suppliers. Usually a part has a standard spec, which all suppliers meet, but some with more or less quality, and quality does affect some aspects of your final product. Sometimes you don't care though.
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Padu wrote:

Without clear measurments and process, this data is not trustworthy. If people buy "generic" batteries, they may "feel" that they are not as good and thus have a worse "impression."
Without some solid statistics, it is impossible to judge. Also, if there are statistics that show one battery is better than another, I'd like to understand why, i.e. cut apart a "good" one and a "bad" one and see what 's the story.

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Padu wrote:

More likely simply outside of one or more specs defined for the brand. Manufacturers don't like to throw out the "rejects" if they are perfectly fine otherwise, and to support their main brand they may not want to put out their seconds with their name on the product. So they create a generic brand that allows them to sell through the seconds, while maintaining the value of the main brand..
Qualitative differences certainly do exist among products produced by the same factory. This has been the case with every manufacturer I've worked with. It's even true in the service sector. My folks ran a successful carpet cleaning business for years where we had both a "brand name" and higher prices for the affluents in the area, and a "no name" bargain basement company where there was less attention to detail. We just switched out the magnetic signs on the vans, and enjoyed the pricing spectrum of the business.
-- Gordon
PS: Sorry to have missed you this Saturday.
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"Gordon McComb"

No, I am sorry I couldn't go. I got a note from my advisor saying that this upcoming Friday we'll get a visit from someone from SPAWAR, and a few things must be ready.... so I had to use any free time to make progress. I'll try to go to the next one.
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Padu wrote:

I'm too lazy to make my own battery packs, but The Robot Marketplace makes them: http://www.robotmarketplace.com /
These are meant for battle-bots and their ilk, though.

I've *looked* at them a bit. I'm still thinking of them for my next bot, but I'm talking $750 for the batteries alone...
I'm *really* hoping that the price will come down quickly.
I'm thinking of a CrustCrawler Nomad for my next bot. -- D. Jay Newman http://enerd.ws/robots /
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"D. Jay Newman"

In my case, because I need long run times, LiPos would have costed $2500 (not counting the special charger required).
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Padu wrote:

Hmmm. I'm running a Pentium M (2 GHz) and sensors for 5 hours on 24V at 7 amp-hours.
I could get a 6 amp-hour LiPol 30V at 6 amp-hours for about $500. A 7.2V 6 amp-hour for my servos is around $150.
And this is at Robot Marketplace prices. -- D. Jay Newman http://enerd.ws/robots /
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My problem is not running the computer or sensors, it is running the dc motors. What do you use in that case? I need 20 amp hour just for mobility. (bear in mind it is an outdoors rover supposed to go over rough terrain at relatively high speeds)
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Padu wrote:

NiMHs or SLAs are probably best for that unless you have government funding. :) -- D. Jay Newman http://enerd.ws/robots /
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On Mon, Jun 06, 2005 at 03:44:02PM -0400, mlw wrote:

Lithium Polymer are hard to beat when it comes to both those factors and beat NiMH hands down. Also, they can typically be discharged at 6 to 10 C (6 to 8 times their capacity rating) without damage.
They do have some down sides - cost is one. The other is that they can be very dangerous if they get damaged or are improperly charged or discharged.
-Brian
--
Brian Dean
BDMICRO - ATmega128 Based MAVRIC Controllers
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