Simple Light Seeking Robot

Picture of Simple Light Seeking Robot
Building the robot

This robot was designed as a project for secondary school pupils to build on an activity day.  The chassis was provided to the pupils pre cut.  The entire cost of the components per robot was just under GBP5 including the batteries.

The robot shown in the picture is the prototype shown with different LDRs and the batteries not in a holder.

The robot you are going to build is a simple light seeking robot that will run towards a light source or can be made follow a moving light source.

The robot is built on a small aluminium chassis and has two motors to move the robot left or right and two light dependent resistors used as light sensors. If the robot senses light with the left sensor it will drive the right motor to turn the robot left and visa versa. If both light sensors receive equal amounts of light both motors will be driven to move the robot forward. The two variable resistors are used to adjust the sensitivity of each channel. The transistors are used to amplify the small current flowing through the light dependent resistor to enable the current to drive the motor
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Step 1: Building the Circuit

Picture of Building the Circuit
The main circuitry for the robot will be on stripboard. Stripboard consists of an insulating board with a square grid of holes drilled in it. Strips of copper link each row of holes, components such as resistors and transistors can be mounted on the plain side of the board with connecting wires passing through the holes. These wires are then soldered to the copper strip.

To solder onto the stripboard pass the wire ends of the components or connecting wire through the correct hole, you can bend the ends of the lead over slightly so that component does not fall out when you turn the board over. Hold the soldering iron so that the bit is against the copper strip of the stripboard and the wire of the component. Touch both with the resin cored solder just long enough for the solder to flow freely. Be careful not to over heat the components or board, then remove the soldering iron and wait for the joint to cool. Now cut off the surplus wire as close to the board as possible. Be careful to hold the end of wire to stop it flying into the air.

The robot is built on a small piece of 0.1 in matrix stripboard 13 strips by 17 holes. Some of the strips need to have breaks in them as shown in diagram. These breaks are made using a twist drill, these breaks are already made for you, the switch is also soldered onto the board.

The components can now be soldered to the circuit board, the position of the components is shown in the diagram.

Once the circuit is complete you will need to solder connecting wires to it, the position for these wires is shown in the diagram.