This Simple Line Following Robot Sensor Circuit work like robot eyes for follow line.
It uses special sensor called IR or infrared to see black line and white ground.
These sensor are like small light but light is invisible.
Circuit look how much light come back then know where line is.
Then this information goes to robot brain, so robot can turn and follow line good.
Like when we walk on footpath robot use this circuit to walk on its path.
Circuit Working:
Parts List:
| Component Type | Component Details | Quantity |
|---|---|---|
| Resistors (All resistors are 1/4 watt) | 1k | 1 |
| 4.7k | 1 | |
| 1.8k | 1 | |
| 200Ω | 1 | |
| Preset 10k | 1 | |
| Capacitors | Electrolytic 10µF 25V | 2 |
| Semiconductors | Transistors BC547 | 2 |
| Phototransistor CNY70 | 1 | |
| LED Red 5mm 20mA | 1 |
Line Following Robot have one sensor like small scanner which is made specially for robot.
This scanner is very small like size of postage stamp it uses short range infrared sensor which is around 5 to 10mm and can be used in CNY70 chip inside.
In robots or toy cars this sensor help follow black line on white floor and keeps robot on right path.
CNY70 chip have two parts one is IR LED which gives light and other one is phototransistor to see light.
LED send out invisible light to floor and phototransistor can see how much light comes back.
White surface send more light back and black send less.
So when robot is on white floor more current goes through phototransistor.
When sensor see light come back current go through resistor R2 to ground then this make voltage drop at transistor T1 base and T1 start working.
Then transistor T2 also turn ON and this make red light LED D1 turn ON
Capacitor C2 help a little by making signal smooth.
After we build the scanner we need to set it up.
First turn knob P1 to middle and put robot on white part of line.
Then move P1 slow until red LED D1 shine bright and after that change P1 small more to stop fake signal from sunlight or other light.
Be sure LED stay OFF when robot is over black line.
Do this many time until sensor work good.
Red LED D1 only show light to tell that sensor is working.
If we want more feature then can add small 5V relay near D1 and R4 and then robot can stop, brake or change the direction.
Also when T2 turn ON and OFF (H to L signal) then this signal can be used to control robot brain.
Resistor R1 control how much power goes to IR LED in chip.
How well sensor work depends on black/white line quality and LED brightness.
Basic characteristics of phototransistor CNY70:
| PARAMETER | TEST CONDITION | SYMBOL | MIN. | TYP. | MAX. | UNIT |
|---|---|---|---|---|---|---|
| COUPLER | ||||||
| Collector current | VCE=5 V,IF=20 mA,d=0.3 mm | IC | 0.3 | 1.0 | mA | |
| Cross talk current | VCE=5 V,IF=20 mA | ICX | 600 | nA | ||
| Collector emitter saturation voltage | IF=20 mA,IC=0.1 mA,d=0.3 mm | VCEsat | 0.3 | V | ||
| INPUT (EMITTER) | ||||||
| Forward voltage | IF=50 mA | VF | 1.25 | 1.6 | V | |
| Radiant intensity | IF=50 mA,tp=20 ms | Ie | 7.5 | mW/sr | ||
| Peak wavelength | IF=100 mA | λP | 940 | nm | ||
| Virtual source diameter | Method: 63% encircled energy | d | 1.2 | mm | ||
| OUTPUT (DETECTOR) | ||||||
| Collector emitter voltage | IC=1 mA | VCEO | 32 | V | ||
| Emitter collector voltage | IE=100 μA | VECO | 5 | V | ||
| Collector dark current | VCE=20 V,IF=0 A,E=0 lx | ICEO | 200 | nA |
How to Build:
To build a Simple Line Following Robot Sensor Circuit follow the below mentioned assembling steps:
- First solder all parts on PCB same like in circuit diagram.
- Check CNY70 datasheet to know which pin goes where and which side is front.
- Give 5V power to the circuit.
- Put the sensor in place and set it up like told before like the calibration steps.
Conclusion:
Simple Line Following Robot Sensor Circuit is important part for robot that follow line.
It uses infrared sensor to see line on floor.
Sensor send and catch back IR light and this tell robot where line is, so robot can move correct way.
This technique help robot go on path by itself and it is useful for many things like factory work, school projects and in fun robot toys.
References:
Analysis of Line Sensor Configuration for the Advanced Line Follower Robot