Circuit

Step 1: The breadboard
This is the “breadboard” – the electronics prototyping board on which we will build the circuit. The breadboard has 30 numbered rows and 10 columns labelled with the letters from A-J. Each hole in the main panel of the breadboard therefore has a unique alphanumeric code. For example, the top left hole is A1 and the bottom right hole is J30. Each short row of five holes forms a single electrical node – when wires (or pins, component legs, etc) are inserted into two holes in the same row of five, they become electrically connected. Two long continuously connected “rails” are provided on each side of the breadboard. These are normally used to distribute a supply voltage to different points in the circuit. We will be connecting the battery voltage to the red and blue rails on the left side of the breadboard, which will supply 3V and 0V respectively to the circuit.

Step 2: Insert the MSP430 microcontroller into the breadboard
CAUTION: The legs of the chip are very fragile, so take care to position the chip correctly before pushing it all the way in!

1. Carefully position the MSP430 with pin 1 at E11 and pin 11 at F20. Pins 1 and 11 are at diagonally opposite corners of the chip. Pin 1 is at the end of the chip with the semi-circular notch on the upper surface.
2. Once all of the MSP430’s legs are sitting into the correct holes on the breadboard, push it down gently but firmly until the black plastic body of the chip is lying flat against the white plastic of the breadboard.

Step 3: Connect the battery pack to the breadboard

1. Do not insert the batteries into the battery pack yet!!!
2. Connect the red wire of the battery pack to the red 3V rail on the breadboard.
3. Connect the black wire of the battery pack to the blue 0V rail on the breadboard.

Step 4: Connect battery supply voltage to the MSP430 microcontroller

1. Connect a short red wire between A11 and the red 3V rail.
2. Connect a short black wire between G11 and the blue 0V rail.
3. Connect a 22 kOhm resistor (coloured bands: red, red, orange, gold) between D11 and G15. This resistor will keep the voltage high on the reset pin of the MSP430 (pin 16) when the robot is disconnected from the LaunchPad.

Step 5: Add a capacitor to stabilise the power supply

1. Connect the 220 uF capacitor between the red 3V rail and the blue 0V rail on the left side of the breadboard. The capacitor is polarised, so it must be inserted the right way around. The minus leg is indicated by a black stripe down the side of the cylindrical body of the capacitor. The minus leg should be inserted into the blue 0V rail.

Step 6: Add a green indicator LED to the circuit

1. Connect a short orange wire between D20 and C29.
2. Connect the green LED between E29 and E30. The LED is polarised, so it must be inserted the right way around. There collar around the base of the green plastic bead is slightly flattened on the side of the negative leg (cathode) which should be inserted in E30.
3. Connect a 220 Ohm resistor (coloured bands: red, red, brown, gold) between A30 and the blue 0V rail.

Step 7 (1/2): Add the transistors (BC237) to the circuit

1. Insert the three legs of the first transistor into E21, E22 and E23. The flat side of the transistor should be facing towards the centre line of the breadboard.
2. Insert the three legs of the second transistor into E24, E25 and E26. The flat side of the transistor should be facing towards the centre line of the breadboard.

Step 7 (2/2): Add the transistors (BC237) to the circuit

1. Insert the three legs of the first transistor into E21, E22 and E23. The flat side of the transistor should be facing towards the centre line of the breadboard.
2. Insert the three legs of the second transistor into E24, E25 and E26. The flat side of the transistor should be facing towards the centre line of the breadboard.

Step 8: Add base resistors for the transistors

1. Connect a 1 kOhm resistor (coloured bands: brown, black, red, gold) between C19 and C22.
2. Connect a 1 kOhm resistor (coloured bands: brown, black, red, gold) between B18 and B25.

Step 9: Add ground connections for the transistors

1. Connect a short black wire between A21 and the blue 0V rail.
2. Connect a short black wire between A24 and the blue 0V rail.

Step 10: Add flyback diodes (1N4001) to the circuit

1. Add one diode between A23 and the red 3V rail. The minus leg (cathode) is marked with a silver band around one end of the black cylindrical body of the diode. That end must be attached to the red 3V rail.
2. Add another diode between A26 and the red 3V rail. Again, the minus leg (cathode), marked with the silver band, must be attached to the red 3V rail.

Step 11 (1/2): Connect the motors to the circuit

1. Connect one motor between C23 and the red 3V rail.
2. Connect the other motor between C26 and the red 3V rail.

Step 11 (2/2): A closer view of the motor connection points on the breadboard.

Step 12: To transfer our compiled program from the PC into the flash memory of the MSP430 microcontroller, we need to make three connections between the LaunchPad and the breadboard.

1. Connect a long black wire between GND on the LaunchPad and the blue rail on the breadboard.
2. Connect a long yellow wire between TEST on the LaunchPad and J14 on the breadboard.
3. Connect a long green wire between RST on the LaunchPad and J15 on the breadboard.
4. Using the mini USB cable, connect the LaunchPad to a USB socket on the PC.

Step 13: Prepare to contruct the light sensor module on terminal block

1. Locate the following parts: 4-terminal block, long red wire, long black wire, long blue wire, 220 Ohm resistor (coloured bands: red, red, brown, gold), 22 kOhm resistor (coloured bands: red, red, orange, gold), RPR220 optical sensor (rectangular black plastic body with four legs).
2. Loosen all screws on the terminal block so that wires can be inserted.
3. To make a neater sensor module, the resistor legs may need to be trimmed a little, but don’t cut off too much. You can always go back to trim off more, but there’s nothing you can do if you trim them too short!

Step 14: Attach leads to the light sensor module

1. Insert a long red wire into the bottom half of terminal 1. Tighten the screw to hold it in place.
2. Insert a long blue wire into the bottom half of terminal 2. Tighten the screw to hold it in place.
3. Insert a long black wire into the bottom half of terminal 4. Tighted the screw to hold it in place.

Step 15 (1/3): Insert the RPR220 optical sensor into the terminal block
CAUTION: Identifying which legs are which is tricky, so please take care with this step! If in doubt, don’t be afraid to ask us to check the position before you tighten it in place.

1. On one side of the black plastic body, the upper edge is slightly sloped and “RPR220” is written on it (you need to look carefully). The two legs on this side of the device should both be inserted into the top side of terminal 1.
2. Of the remaining two legs, the one closest to the chamfered (flattened) corner edge of the black plastic body is inserted into the top side of terminal 2.
3. The final leg is inserted into the top side of terminal 3.

Step 15 (2/3): Insert the RPR220 optical sensor into the terminal block
CAUTION: Identifying which legs are which is tricky, so please take care with this step! If in doubt, don’t be afraid to ask us to check the position before you tighten it in place.

1. On one side of the black plastic body, the upper edge is slightly sloped and “RPR220” is written on it (you need to look carefully). The two legs on this side of the device should both be inserted into the top side of terminal 1.
2. Of the remaining two legs, the one closest to the chamfered (flattened) corner edge of the black plastic body is inserted into the top side of terminal 2.
3. The final leg is inserted into the top side of terminal 3.

Step 15 (3/3): Insert the RPR220 optical sensor into the terminal block
CAUTION: Identifying which legs are which is tricky, so please take care with this step! If in doubt, don’t be afraid to ask us to check the position before you tighten it in place.

1. On one side of the black plastic body, the upper edge is slightly sloped and “RPR220” is written on it (you need to look carefully). The two legs on this side of the device should both be inserted into the top side of terminal 1.
2. Of the remaining two legs, the one closest to the chamfered (flattened) corner edge of the black plastic body is inserted into the top side of terminal 2.
3. The final leg is inserted into the top side of terminal 3.

Step 16 (1/3): Add the resistors to the colour sensor module

1. Connect the 220 Ohm resistor between the top side of terminal 3 and the top side of terminal 4.
2. Connect the 22 kOhm resistor between the top side of terminal 2 and the top side of terminal 4.
3. Tighten the screws in the top halves of all four terminals.

Step 16 (2/3): Add the resistors to the colour sensor module

1. Connect the 220 Ohm resistor between the top side of terminal 3 and the top side of terminal 4.
2. Connect the 22 kOhm resistor between the top side of terminal 2 and the top side of terminal 4.
3. Tighten the screws in the top halves of all four terminals.

Step 16 (3/3): Add the resistors to the colour sensor module

1. Connect the 220 Ohm resistor between the top side of terminal 3 and the top side of terminal 4.
2. Connect the 22 kOhm resistor between the top side of terminal 2 and the top side of terminal 4.
3. Tighten the screws in the top halves of all four terminals.

Step 17 (1/2): Connect the colour sensor module to the breadboard circuit

1. Connect the red wire of the colour sensor module to the red 3V rail on the breadboard.
2. Connect the black wire of the colour sensor module to the blue 0V rail on the breadboard.
3. Connect the blue wire of the colour sensor module to D17 on the breadboard.

Step 17 (2/2): Connect the colour sensor module to the breadboard circuit

1. Connect the red wire of the colour sensor module to the red 3V rail on the breadboard.
2. Connect the black wire of the colour sensor module to the blue 0V rail on the breadboard.
3. Connect the blue wire of the colour sensor module to D17 on the breadboard.

Step 18: Insert the batteries.
CAUTION: Double check the circuit for error before inserting the batteries. Even better, get someone else to double check it for you.