by Le Magicien

This is the project of a Light Chaser robot. The robot will turn towards the brightest light and move forward chasing or following it. It has two motors (left & right) in order to make the turns; on top two light sensors (photodiodes) separated by a PC board in order to simulate "a nose". This nose is particularly important because it will provide a shadow thus preventing both sensors from being illuminated when a side light is present (the motor on the non-illuminated sensor side will turn on thus aiming the robot towards the light). When the light is right in front of the sensors, there will be no shadow and both sensors will be equally illuminated, i.e.: both motors will be running and the robot will move forward.

The main robot board was an old MOVIT kit, it had two IR pairs of sensors (emitter-receptor) to read a rotating cardboard circle painted black and white in two circumferences. This sequence of black and white sectors programmed the robot to make turns, move forward, stop, etc. This part of the circuit was removed and a new circuit was designed and put in place

Click on the left to see the main circuit of the Light Chaser.


Front View

Here on the left we see the front view of the robot, the right plastic dome has inside the original circuit for motor control. The one on the left has the new circuit.

Right in the middle, a pair of photodiodes separated by a PC board "nose"; this circuit is supported and held in place by a rigid wire bent to put the sensors in the best position.

Below the main platform we see the motors and the gearboxes.

Originally there was a third motor to rotate the cardboard disk I've mentioned above, this motor was taken because it has no use in the new circuit.

Here on the left we see the lower part of the platform: left & right motors with its gear boxes, battery holders (3 volt for the motors and 9 volts for the control circuit).

Right between the batt holders we see a support terminated in a plastic sphere, although I could replace this 3rd support, if the surface is smooth enough the robot will move without any problem, only in rough surfaces this support should be replaced by a pivoting wheel.

Here on the left you may click the photograph to see a more detailed view. This one shows the right photo sensor with the PC board acting as a "nose".

General Connections

Now the general connections schematic, as you see the original circuit was preserved, only the Added Sensors Circuit & Sensors (RFT / LFT) are new.

Motor connections to the original circuit are preserved, but now we have SR and SL going to the Added Circuit, and the connections to the photodiodes RFT and LFT

Also we need a +9 volt / GND supply to the new circuit and sensors.

This is the basic arrangement of the Added Circuit without the sensors that go at the RFT and LFT pins.

As before, SR and SL command logic signals go to the main circuit board (Original).

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