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. |