This circuit is like the eyes for a line following robot.
It uses special sensors infrared or IR that can tell the difference between a black line and a white surface.
These sensors are like tiny flashlights that shine invisible light.
By seeing how much light bounces back the circuit can tell where the line is.
This information is then sent to the robots brain control system so the robot can steer itself and follow the line perfectly.
Just like how you follow a sidewalk this circuit helps the robot follow its own special path.
Circuit Working:
Parts List:
| Component Type | Component Details | Quantity |
|---|---|---|
| Resistors (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 |
The Line Following Robot features a sensor or surface scanner, designed for robots.
This compact device, about the size of a stamp, utilizes a short range 5 to10mm infrared proximity detector built around the CNY70 IC.
In certain applications such as with line following robots or electronic toy vehicles the scanner is employed to trace a pre drawn black line on a white surface ensuring accurate alignment.
The CNY70 IC comprises an infrared LED and a phototransistor.
The LED emits invisible infrared light onto the track while the phototransistor acts as a receiver.
Typically, black surfaces reflect less light than white surfaces causing more current to flow through the phototransistor when it is above a white surface.
When a reflection is detected i.e when IR light falls on the phototransistor, current flows through R2 to ground, creating a voltage drop at the base of T1 which in turn causes it to conduct.
Consequently, transistor T2 starts conducting illuminating the visual indicator LED D1.
Capacitor C2 serves as a small buffer.
Upon construction and installation the scanner requires calibration.
Initially, set P1 to its mechanical center position and position the robot over the white portion of the track.
Slowly adjust P1 to achieve a strong response from D1.
Then, fine tune P1 to minimize false detections caused by external light sources.
Ensure that the LED remains off when the sensor module is over the black area.
Repeat this process until the correct calibration is achieved.
The red LED D1 serves solely as a visual indicator.
For additional functionality a suitable 5V reed relay can be added in parallel with the D1 and R4 wiring with appropriate modifications, to enable braking, stopping or redirecting of the robot.
Likewise, the high to low H-L transition at the collector of T2 can be utilized as a signal to control the logic blocks of the robot.
Resistor R1 determines the operating current of the IR LED inside IC1.
The sensing capability largely depends on the reflective properties of the track markings and the strength of the light output from IC1.
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 steps:
Assembly Steps:
- Begin by soldering the components onto the PCB following the circuit diagram.
- Use the datasheet of the CNY70 IC for pin identification and orientation.
- Connect the power supply 5V to the circuit.
- Install and calibrate the sensor as described in the previous message.
Conclusion:
A Line Following Robot Sensor Circuit is a key component in line following robots using infrared sensors to detect and follow lines on surfaces.
By emitting and detecting infrared light, the circuit provides feedback to the robots control system, allowing it to stay on course.
This technology enables robots to navigate predefined paths autonomously making them useful in various applications such as industrial automation, education and entertainment.
References
Analysis of Line Sensor Configuration for the Advanced Line Follower Robot
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