Worksheet 6
UKMARSBOT assembly details:
Line follower sensor board assembly
(This has been edited to remove bits not used in the DHS robots
and some resistor values have changed as we are using 3.3 volts not 5v)
BUILD SEQUENCE
1. Solder in emitter load resistor R4, – 68 Ὠ
Then the detector load resistors R7. and R10.
The value of these detector load resistors depends on the photo transistors being used as detectors.
We are using only the two line detectors so are not using R6 or R11.
We are using the BPW85C phototransistor so the values are 1.8k (or 2.0k) Ὠ resistors for R7, R10
2. (We are not using resistors R1 or R2 that provide the biasing for the pulse transistor.)
The emitters are to be left on all the time, so we put in a wire link on the PCB where it says LNK1 BYPASS
3.We use the two indicator LEDs, solder in resistors R8 and R9 both 220Ὠ.
4. Solder in Capacitor C1 100μF making sure that it is oriented correctly. The longer lead should be the positive side and the negative side should be marked on the body of the capacitor. The PCB shows a + next to the positive lead.
5. Solder in the two indicator LEDs LED4 and LED5. Make sure these are correctly oriented.
The long lead on the LED should go to the hole marked A (Anode)
and the shorter lead (and the side with the flat on the LED) should go to the hole marked K (cathode).
Make the LEDs stand a few mm above the board by slipping a thin piece of paper between the legs of the LED
between the LED and the PCB.
6. The emitters are not to be pulsed, so no transistor is required.
7. Next we need to add the 1 sensor LED and 2 phototransistors.
These are all mounted on the other side of the PCB to the other components.
The LED (Truopto OSHR3131A-NO 3mm 3000mcd) is soldered in with its long lead (+ve) towards the front of the board marked A.
Once they are soldered in, put 3.3v and Gnd on the relevant connector pins and 5v on D12 to check that they all light up.
Next put in the 2 phototransistors.
These also go with their long leads towards the front of the board marked E (emitter).
7a, The stop sensor:
R11 is 2.2k, R5 is 82 ohm. 
The emitter and Phototransistor sould be on a small extra piece veroboard that puts them more than 40mm away from the centre line.
8. Ten of the 11 holes of connector J1 on the sensor board now need to be attached to a 10 core multi-way wire or by 10 connector leads to the sensor socket on the main board. You do not use the 3.3v connection at the end marked J1. These will plug in via whatever connectors you use into the group of 10 adjacent pins marked from 5v through to A3 on the main PCB. The easiest solution is to use 5 Female to Female Dupont connector leads cut in half with the cut end soldered into the sensor board so that the 10 female ends plug into the Pin header on the board.
9. The sensor board is fixed to the main PCB with two M3 screws with a 10mm spacer between the main PCB and the sensor board, with the nuts on top. These M3 screws go through the front set of two holes in the main PCB from the bottom.