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Old 12-21-2009, 11:22 AM   #1
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Default New project

Hey guys,

Well, no idea whether this will or won't happen, but I'd quite like it too if I can find the time / get round to it. At the moment though I'm still in the stages of collecting ideas and working out whether it's feasible from both a practical and financial standpoint.

The idea is to have a wifi controlled robot that can trawl about with a full computer on board. It'll probably be an atom based build powered off a Yuasa cyclic 12V battery (or similar) and running some version of unix / linux (using a wireless card so I can communicate with it over a network.) The higher level programming / PC side I'm not worried about at all, but my lower level electronics isn't brilliant - and in terms of controlling motors this is a fair stumbling block.

So, the questions:

- Any suggestions on motors / gearboxes (preferably motors with gearboxes included!) that will drive this thing? It doesn't need to be the fastest thing on the block at all - I'd prefer it to be a bit slower and more torquey than fast and not be able to go over any bumps. It'd be nice if it moved at a reasonable speed though! I'm imagining the whole thing will probably weigh in at well over 10KG with the battery (with most of it being the battery) so it'll need to shift that lot.

- Any advice / suggetsions on motor controller boards that'll work under linux and power the above motors?

- Any suggestions on wheels? If so, any recommendations on attaching them to the motor / gearbox axle?

- Anything else you think I'm missing and haven't yet thought about?

I'm in the UK if that makes a difference with any links you'd recommend. Thanks
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Old 12-23-2009, 08:45 AM   #2
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Default Re: New project

hmmm...
it really depends on what you're after.

IF you want a cheap motor that can shift, then look at cannibalising a cordless power drill perhaps, the motor will drag a fair weight, (especially when geared down). and you should be able to power it from the same battery that you plan on powering the PC from.

(or if you cannibalise a couple of cordless drills you'll have a couple of decent powerpacks, and their connectors from the drill body, and the wall chargers, so you can use the quick release and fast charge mechanisms that the drill company have already developed).

if you want some serious torque, then electric wheel chair motors are probably the way to go, and these will have a gear box with them, and large rubber wheels. (but these may be too big for you purpose.

if you want precision, like the ability to tell the robot to go forward ten feet then you'll want to either create some sort of feed back system using wheels and optical sensors to see how far the wheels have turned, (much like you'd find in an old ball mouse). or you'll want to use stepper motors.

I'd recommend stepper motors, simply because then you can buy an off the shelf controller rather than having to build your own solution for the counting method of wheel turns...

aside from dedicated stepper motor controllers, you might also look at some development boards, these will interface with the PC over standard ports, and can usually do an awful lot of stuff.

if you really wanted to go in-depth with the electronics on this, and perhaps learn a little as you go, then I can give you a hand to pick some reasonable PIC controllers, (use microchip ones and you can register at their site for some free samples). there are also plans on the internet to be able to build a free programmers too. and there are freely available compilers as well.

I've build a light controller before that connects to a PC via the serial port and just listens for commands and turns on outputs, I'd be happy to give you this code, and links to the chip/instruction manual and instructions to build a programmer if you want. (you could use the light controller to connect to a set of relays rather than triacs to switch on the higher current/voltage supply for the motors. (I used triacs as I was switching mains voltage).
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Old 12-23-2009, 11:17 AM   #3
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Default Re: New project

www.parallax.com
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Old 12-23-2009, 01:50 PM   #4
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Default Re: New project

Quote:
Originally Posted by setishock View Post
Seti has the right idea.

Let me introduce you to a couple of places.

http://Arduino.cc
http://sparkfun.com
http://www.robotshop.us
http://www.societyofrobots.com


I am currently working on a robot.


Also! check this place out! It's a GREAT place. They have a sample program where they will send you free samples of most of there products OKW enclosures

http://www.okwenclosures.com

EDIT: WHOA!!! CHECK THIS OUT!
Sparkfun.com is doing what is called a "Free day" all you have to do is pay for shipping and your order must be under 100 usd.
!!
http://www.sparkfun.com/commerce/news.php?id=305
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Old 12-23-2009, 02:26 PM   #5
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Default Re: New project

Thanks for the advice and the liks guys, very helpful Just a minor point without wanting to sound like I'm complaining - I'm UK based so any relevant shops this side of the atlantic would be much appreciated! At the moment I'm just looking at maplins for the electronics stuff and B&Q for various bits and bobs I'll need to build the frame - if there's any gems out there I'm missing feel free to let me know!

Electric wheelchair motors are an interesting thought, thanks for that suggestion. They might be a bit big, but on the other hand over-speccing is better than the other way round. My other thought along the motor front was a pair of windscreen wiper motors. They seem fairly cheap to pick up on ebay and the like, and from what I've heard they're pretty torquey as well (popular choice for featherweight robots on robot wars for instance.) I considered stepper motors and decided against them in the end, for the amount of torque I'd need they're expensive things. I might make myself up some rotation sensors later if I need them - that'd be an interesting task.

Vampist - would be interested to hear about your bot? What does it / will it do and what kind of design does it use? If you don't mind
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Old 12-23-2009, 02:40 PM   #6
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Default Re: New project

This is my first bot so I am sort of starting easy, but I am an over overachiever soo lol..

I am using a material called Sintra, using a 6mm piece for the base of the robot.
(pretty strong stuff)

The base is 8 by 12 inches. That will have four one inch stand offs in a 6 by 8 rectangle with a 3mm piece of sintra on top. (mainly just to protect the electronics but it will also be used to raise up some of the sensors.

For controls I am using two-three ATmega328p-pu Microcontrollers on the actual robot. Mainly to control motor directions, lights, sensors, etc.
Communicating via Serial(tx/rx)

I will also be building a remote control I can use to take control of the robot at any moment.

Sensors I am using so far are, light sensors and some range finders (act like feelers).

For the motors I am using a Quad half H-bridge. That can handle up to 36VDC at 1A.

I am designing this robot to be built so I can add to it.
I am thinking of designing some type of data logging system to map out my house.

I will keep you updated as I am in designing phase sort of like the alpha phase.

I will be building the robot sort of in sections testing it out on breadboards and then incorporating them all together.

EDIT: As for the actual motors as of right now I have two http://www.solarbotics.com/products/gm12a Gm12a 100:1 but I may scrap them for this project as for they don't really have A LOT of speed to them.

It all depends if I can find a 1:3 ratio gear setup somewhere.


I would LOVE to eventually move up into a build with an actual computer as the brains.
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Old 12-24-2009, 06:34 AM   #7
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Default Re: New project

windscreen wiper motors probably won't be up to the job. -you can stop a wiper with your hand, or with a not too thick layer of snow landing on them, and they are already geared down...

if the battery drill idea isn't floating your boat then you also you might look at some second hand starter motors on ebay cause they'll have lots of torque.

a lot of the suggestions above are not just sold in the US, there are UK suppliers. -unfortunately it'll just be a long search.
also some of those things will be found on ebay.

and some of the US shows will ship to the UK.
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