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Robotics Tutorials - Intermediate - Hardware - Build an Obstacle Avoiding Robot

This tutorial will talk about making a fairly simple robot using the Robocore, Sharp GP2D02 IR proximity sensor and a couple of microswitch bump sensors. At the bottom of the page you can find a sample program for it.

This little robot is great; the Sharp IR gives it an infra red 'vision' of up to 80cm. Watching a robot driving around and magically 'seeing' obstacles in its path is great to watch. Unfortunately its not foolproof and small objects might go undetected, so a pair of bump sensors on the front are needed for backup.

I used Lego to build the robot chassis but obviously you can use whatever you want. I like Lego for this sort of application because it's easy to work with and can be quickly modified. The finished robot is shown below:

I'm going to briefly talk about making the chassis but I'm not going to concentrate on it too much. Lego is a great fun, so play about with your ideas. Below are a few pictures of the Lego shell so you can get an idea as to what I did.

The bump microswitches are glued to the front Lego brick and attached to the sliding bump bar with masking tape. There might be a better way to do that but glue worked fine for me. The yellow elastic bands on either side of the chassis reset the bump bar after a collision

I'm a big fan of tracked robots because my lab isn't the tidiest of places and tracks give it a bit of climbing power. They do, however, make turning less efficient, but with good gearing and light robots this isn't really a problem

 

So now that you've built your chassis out of something it's now time to put all the electronics into place. All of the components used are shown below, excluding the bump microswitches.

I used the Robocore, 9.6 volt battery pack, Tamila to 2.1mm converter and Sharp GP2D02 IR sensor.

 

The bump sensors were soldered to 0.1" pitch headers with 47K pull down resistors. For more information about interfacing microswitches look at the tutorial here (link to tutorials, beginners, sensors)

Likewise, the Sharp GP2D02 was soldered to 0.1" pitch header.

 To follow the sample program the following connections should be made:

- DC motors should be connected to motor outputs 1 and 2.
- The bump sensors on pins 10 and 12.
- The Sharp on pins 13 and 15.
 

To put the whole thing together I stuck the battery in first then placed the Robocore on top, simply securing everything in place with a couple of elastic bands. The Sharp IR sensor is mounted on the front of the chassis with elastic bands.

The software drives the robot forwards until it detects an obstacle with either the Sharp or bump sensors and turns accordingly. The Sharp sensor gives no indication as to which side the object is on so the software alternates its turn direction. This can produce some fun 'dancing' if the robot drives into a corner but generally works well.

 


 

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