Light Controlled Vehicle
- 2. 2 Table of Contents: I. Introduction A.Problem Description……………………….………3 B.Design Concept…………………………………….3 II. Analysis of Components A.Characterization of each sensor..........................6 B.Design Considerations…………………………….7 III. Design Description A.Block Diagram……………………………………...8 B.Circuit Schematic…………………………………..9 C.Descriptions…………………………………….…10 D.Physical Mechanical Construction………………………….…………...11 IV. Conclusion A.Lessons Learned……...………………………….12 B.SelfAssessment………………………………….12 C.Future Work……………………………………….12 V. Appendix
- 3. 3 I. Introduction ● Problem Description Our team has worked on a design that allows us to control a forwardmoving vehicle using a flashlight. For practical purposes the flashlight will be an application from a smartphone. In addition, we have added basic object detection to the vehicle, allowing it to stop in the face of danger. In essence, our vehicle has the ability to turn based on amount of light shone on the sensors mounted on the vehicle, as well as stop in the event of imminent collision. ● Design Concept In the design, two photoresistors stick out from the sides of the car, having variable resistance in relation to the amount of light shone on them. The more light shone on them changes the resistance, which is read by the Arduino, which controls the current that feeds into the base of the BJT located in the motor circuit. This causes a change in motor speed, allowing us to control the turning of the vehicle with 2 control and motor circuits. The Arduino is used to create a pulse width modulated (PWM) signal that feeds through the control circuit. On one of the control circuits, there is another subcircuit, the infrared sensor circuit, that acts as a power switch. If an object is sufficiently close to the infrared sensors, the Arduino directs one of the motor circuits to shut off, either stopping the vehicle due to friction, or turning the vehicle away from the hazard.
- 4. 4 The following is a truth table about the behavior of the car: State Action If no object in front: Neutral Car moves forward Shine light on right sensor Car turns right Shine light on left sensor Car turns left Cover both sensors with hands Car stops If object in front: Any Car stops Table 1: Truth table for vehicle behavior
- 5. 5 The following is a table of items needed to construct our vehicle: Item Value Quantity Resistors 330 Ω 5 Resistors 10 kΩ 3 Resistors 10 Ω 4 BJT Transistors N5192 2 DC Motors DG01D 2 Diodes 1N914 1 V 2 Yellow LEDs 2.2 V 2 Photoresistors GL5528 2 Rechargable NiMh Battery Pack 7.2 V 1 Infrared Emitter and Detector Set 1 Table 2: Materials Needed For LightSensing Autonomous Vehicle
- 10. 10 ● Photoresistor Motor Control SubCircuit The two photoresistors change in resistance depending on how much light is shone on them. This affects the duty cycle of the virtual Pulse Width Modulation (PWM) signal generated by the Arduino with proper mapping from (700, 1023) to (0, 255). The analog Arduino values used range from 0 to 255, from stationary to full power. This is because there does not need to be any constraints to the maximum speed, as we only need a noticeable difference between room light, flashlight, and darkness. We use an LED to check for a change in current to the base of the BJT. ● Motor Drive SubCircuit The PWM signal feeds into the BJT, which, depending on the duty cycle, dictates how much current goes through the motor circuit. This changes the speed of the motor. By duplicating the photoresistor motor control subcircuit and the motor drive subcircuit, we can effectively create a turning effect by slowing down or speeding up one motor. ● Infrared Sensor SubCircuit The infrared emitter and detector LEDs are connected to the Arduino. They produce a signal by sending and detecting a signal that comes from the emitter. When the signal is detected, the result is sent to the Arduino for processing. If the analog value is above a certain threshold (something is too close), then the Arduino stops sending a PWM, stopping the motors.
- 12. 12 IV. Conclusion ● Lessons Learned When we were trying to map the parameters for the photoresistors into a range that the Arduino could read, we had to fiddle around with the numbers, effectively making our method trial and error. The infrared sensor was a pain to set up, and still doesn’t work perfectly. This is probably due to the fact that there are too many diodes, which take up too much voltage. The integration of the infrared sensor was a huge hurdle also, as we have never worked with a like sensor in ECE 110 lab. Eventually, it worked out, but it took twice as long as the photoresistor integration. ● SelfAssessment The lightdirected vehicle works as intended. When shining a flashlight at the photoresistors, the vehicle turns in the direction of the light being shined. Likewise, when a photoresistor is covered by a hand, the vehicle turns away from the hand. The added resistors in the motor circuit work well to slow the vehicle to a reasonable pace. The Infrared circuit is a bit spotty, but stops the vehicle when a reflective surface, like a phone screen, is placed in front of it. ● Future Work We may end up improving the reliability of the infrared sensor, as well as fiddling with the speed a little more, as the vehicle requires a little push to keep going due to static friction. Because the infrared sensor didn’t work so well, we may try using ultrasound in the future for increased reliability of object detection.