Let's Make Robots!

School project tank robot

Hi

To finish my education i have decided to make a tank robot as my project. But i cant afford it to cost to much, as i am not sure how much time i will use on it when i am done. And if i decide to spend more time on my robot, i realy want it to be able to drive around outside. (more fun)

First problem i have runed into is, damm tracked based chassis cost alot. And most of them can only be used indoors. Any1 know some good cheap track based chassis that dont cost to much? And some motors/gearbox.

I live in Denmark (Aarhus). But at the time, i dont know any shops, that sells robot parts.

In my project i shall build all the electronics my self. And i have deciede to start out with building a robot that can drive around by it self, and avoid obstacles.

I am thinking of using either Led's with photo diodes/transistors, or maybe infra red. Not sure what is best. As i where told by a friend that they dont cost to much, and still should be very good to use.

Hope that there are some1 out there, that can help me.

 

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If you are using it outside, the IR light from the sun would scramble the sensor. For outside apps, I'd reccomend an ultrasonic.
While virtually all IR sensors are hampered by sunlight, appropriate filtering and modulation can almost remove the problem entirely, so there is certainly nothing wrong withusing IR outside.
In cases where you want to detect and avoid everything (i.e. forward collision sensors), ultrasonic sensors are often a good choice. However if you use an ultrasonic sensor to detect cliffs/drops/steep slopes you'll often find that by the time the sensor reports a problem the bot is already halfway off the cliff =/
IR sensors are great in this case because as soon as the IR beam points over the edge the bot will know about it.
for tank tracks , search rc tank on ebay and you will find some small tanks that u could pull apart , or u can find the replacement metal tracks (but they tend to be dearer then the hole tank).
Cheap tank tracks for outdoor use is the wet dream for all hobbybuilders. If you find a way to manufacture it you'll get rich quick. In the meen time I'd settle for big off-road wheels. If you use 6 wheels it'll get the rugged all terrain look at much lower price. Here's Oddbots DIY version. DAGU's gonna start selling these (really cheap I hope)!

Thanks for the replys.

I can proberly afford to use about 600-2000kr (danish kr) on my project. aybe alittle more.

Problem with ebay, is that most of those that sells tank's there only will ship to canada and U.S.

The reason i want to use tank tracks, is that then the robot will have the ability to turn around where it stand. And if i also can use it outdoors, it will be more fun to work with, also if i want to work on it when i am done with my school project.

And i must say, that link to the 6wheeled, where very nice.

the six wheel design I linked to (and many onthers) have the same kind of steering as your tank, often referred to as skid steering or tank steering. None of the wheels turn like the front wheels of a car, they are all mounted in line. And you turn by running the wheels on one side forward, and the other side backwards. Just like a tank on threads or tracks.

 

And for those unfamiliar with Danish money-thingys: The budget is roughly 100-350 USDollar

i recamend vex they have a reliable tread and a easy programing software

a good platform for beginers

vex.com

I have found that sensors (for obstacle detection) are the hardest of themall to fabricate yourself or scavange from used gadgets. All the other stuff (drive system, motors, power, electrics, even brains) are easier and cheaper to come by.

So my advice would be: choose one really good sensor that you understand really well. Spend some time in the understanding part. Spend your remaining budget on the rest. Economize where you want, just not on the one sensor.

One sensor hould be enough. If you want a robot that can look in different directions, put the expensive sensor on a cheap servo. Build your budget around the sensor. The rest will follow.

i have built my own ir sensor before but they are not as good as some you can buy. Rik is right, robots only way to know anything is by sensors, so that parts needs to be the best part of your robot. Without working sensors it isnt really even a robot.

 

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