Every ROBOT entering a SUMO contest needs a white line detector not to fall out of the DOJO (Arena with a white border ! Build this circuit and get ready for combat !
This circuit uses 1/2 of a LM358 OpAmp so if you decide to do a line follower instead of a single line detector you'll just need to add components to it's right side !
I used a stripboard as this is a easy method to build a circuit and it doesn't require acids and special equipment !
Step 1: Cut the Stripboard
Cut a 9x14 piece of stripboard. Solder a conductor from line 1 to 7. This will bring the positive to one edge of the variable resistor.
Step 2: Minus OpAmp
Solder a conductor from line 6 to 8. This will bring the negative to pin 4 of opAmp.
Step 3: Cuts for Variable Resistor
Cut the strips near where you are going to solder the variable resistor.
Step 4: Enlarge Hole for Variable Resistor
You will have to enlarge the too holes for the variable resistor.
Step 5: Solder the Variable Resistor
Put the variable resistor in place and solder it's 3 pins !
Step 6: Solder the 10k Pull-down Resistor
This is to keep the output at a low state if you are going to connect it to a microcontroller.
Step 7: Solder the 560 Ohm Resistor to IR LED
Solder the resistor which will connect to the IR LED
Step 8: Solder the 10K Resistor (pull-down to Non-inverting Ampop Input)
Solder a 10k resistor between line 5 and line 8 (minus)
Step 9: Solder the 560 Ohm Resistor for Output Red Led
Solder the 560 ohm resistor between line 3 and 9 that will limit the current through the output led (white line indicator)
Step 10: Solder the Led Indicator
Now that you have the 560 ohm in place solder the red led indicator !
Step 11: Solder the 8 Pin Socket for the OpAmp
Solder the OpAmp socket and make the cuts on each of the 4 lines
Step 12: Solder the IR Emitter (Transparent) and the IR Photodiode (Filtered)
This step is critical. As the line detector will be facing down you will have the solder the IR LED and the IR Photodiode on stripside of the board !
Step 13: Solder the + Shunt
Pin 8 (line 3) of the OpAmp needs to be connected to + rail (line 1)
Step 14: Cut 3 Double Headers and Solder
You will need to connect you line detector circuit to power and microcontroller so solder the headers to - line 8, + line 1 and output line 3
Step 15: Put the LM358 in Place and Power the Circuit !
You will have to test it pointing the board to a white surface and a black surface and adjusting the variable resistor ! Remember it is a good practice to indicate on you board the out header, the minus and the positive.
Step 16: Protect You Sensors !
Your SUMO ROBOT will have fierce combats ! You better put some PVC pipes to protect the sensors and glue it with hot glue !