Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: Hernan on May 25, 2010, 02:10:46 AM
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Hi,
I'm thinking of building whats basically a robotic platform for a netbook, and was wondering what components i would need.
I intend to have the processing done by the netbook itself, so (from my understanding of these things) i won't need a microcontroller.
To begin with it would basically consist of a platform with some wheels controlled by the netbook to move it about, but i want to extend it's abilities later on, eventually to include object avoidance etc, but that would be a fair bit down the track.
To begin with it would need at least two motors (or i suppose, one motor and a servo) to allow it to move and turn.
I would like the interface with the netbook to be via a usb port, and to be controlled by programs written by myself in C++ or similar (I'm a fairly capable programmer).
Cheers
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You'll need a micro controller, unless your notebook has a parallel port, the arduino is dam cheap, and programmed in pseudo-C so with that you shouldn't have a hard time with it.
As for the motors, expect to spend some dough, normal servos are small, and weak for a decently sized robot, you need something a long the lines of a Hitec HS805BB+ if you want to use servos, for their simplicity in use etc.
You will need a decent battery as well.
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the arduino looks pretty interesting, but my understanding was that a microcontroller was only needed if the robot was to control itself, if it's going to be connected to a computer, why would it need it's own processor? (correct me if i'm wrong, i havn't been looking into robotics very long).
Although that is pretty cheap, and the ability to work independently could lead to some future projects without a connected netbook.
What sort of sensors is the arduino compatible with? i had a quick look and saw some interesting things, but didnt see anything which could be used for object avoidance (well, a photocell, which i imagine could work using an LED and laying a path down for it around the house, but thats not what id call object avoidance.)
Also - how many motors/sensors is it able to use at once?
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As other has stated, you should get a microcontroller. The netbook can't interface easily with the sensors, servos and motors. If you get an Arduino or Picaxe, you could let the microcontroller interface with the electronics and only make a small program that acts as an interface between the sensors and the netbook. Then you make the main program on the netbook and let the netbook tell the microcontroller "turn on motors", "read ultrasound sensor" etc.
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As stated above, you will probably need some stuff besides your netbook to help with the control aspect of the robot. Two paths i can recommend for you:
1. A microcontroller such as the arduino that acts as a "middle man" between the pc and the sensors and motors.
2. Phidgets boards, these are already interfaced with the pc via usb and can control stuff like sensors and motors.
Of coarse the first would be cheaper but probably require a bit more effort on your behalf.
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Im thinking arduino looks like the way to go. Just a question about servos - as i understand them, servos have a limited range of movement, and can't just keep turning. Is this the case, or is that simply the one application i've seen them used in? (i used to fly model planes, and servos were used to manipulate the control surfaces).
Thanks for the replies by the way, this seems like a great place to get robotics help.
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Usually servos do have a limited range of movement, but often you modify them to so that they can rotate continually (http://www.societyofrobots.com/actuators_modifyservo.shtml). There are two ways of doing this: with glue and with reisitors. The method above is the glue method.
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What sort of sensors is the arduino compatible with? i had a quick look and saw some interesting things, but didnt see anything which could be used for object avoidance (well, a photocell, which i imagine could work using an LED and laying a path down for it around the house, but thats not what id call object avoidance.)
Also - how many motors/sensors is it able to use at once?
it's compatible with anything you want really, just make a program to make it compatible!
These guys are fairly cheap for what you get:
http://www.acroname.com/robotics/info/articles/sharp/sharp.html (http://www.acroname.com/robotics/info/articles/sharp/sharp.html)
choose the model that suits your wallet, and need, i'm using a short distance one, but i could do better with a longer range, considering my current robot project is a bit fast, but it's not with servos so you should be fine.
They let little interference from sun mess with your readings, so they are pretty good, they will output an analog voltage, that is very easy to read with one of the 6 analog inputs.
It can control 12 servos, 2 is enough for a simple differencial drive.
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Whenever someone asks me about starting out with robotics, I always tell them about Arduino.
The varieties of arduino that are available are suitable for most beginner applications(and a lot of not so beginner).
It's easy to use and the communities(ie available information) that are accessible are vast.
As stated above, you really do need some way of processing the data that will be sent from your computer and turn it into something that the servos(or motors) can use. This isn't really too easy to do without some funky electronics (the arduino does this for you, almost).
The arduino's also really easy to program and even the smallest and cheapest arduino will have enough 'ports' on it for you to be able to play around with different sensors in the future.
Phil.