Lane Changing Car Signal With Blind Spot Detector Simulator

Original Idea

For my independent design project, I will be simulating a blinker system in a car that has a blind spot safety feature. I was doing some research into some designs online and I found the beginner version of this as a blinker system for a bike on the Electronics Hub (https://www.electronicshub.org/bike-turning-signal-circuit/). My design will feature Resistors, Capacitors, a 555 Timer, 2 Green LEDs, 1 Red LED, 1 IR LED, 1 Phototransistor, Diodes, and a SPDT Slide Switch. The 555 timer, in this case, will be astable and make the Green LEDs blink. If I can get the simpler version of this design working, then I will also implement more Green LEDs to have more of a flashing motion that is brighter and easier to see. I might also try to implement audio using a LM386 Amplifier to actually mimic the beeping noise if someone is in your blind spot.

For this circuit, about 9V - 12V should be enough to power it. If the SPDT Switch is slid to the right, then the Green LED(s) to the right will turn on and blink until the switch is returned to COM or to the left. If the SPDT Switch is slid to the left, then the Green LED(s) to the left will turn on and blink until the switch is returned to COM or to the right. Notionally, when the left or right light is blinking and the switch is toggled, then the LM386 should not make any noise. The Green LEDs in both cases will only be able to be toggled if and only if the phototransistor and the IR LED are not blocked. If it is not blocked, then this is simulating that the blind spot is clear, and you can switch lanes with no problem. If the IR LED and the phototransistor are blocked, then you should not be able to toggle the Green LEDs even if the SPDT Switch is toggled and the RED LED will come on to indicate that someone is in your blind spot and you should not switch lanes. Notionally, if the RED LED is on, then the LM386 Amplifier should make a loud noise to also let the driver know that you cannot switch lanes at this time.

Use the link below to download the original lab report pdf.

Results

Abstract

The Lane Changing Car Signal with Blind Spot Detector was designed by applying concepts from previous labs and using a similar template for a Bike Signal from the Electronics Hub. The project requires basic electronics knowledge about MOSFETs, common rectifier diodes, 555 timers, speakers, and troubleshooting skills for circuits.

I. INTRODUCTION

This Lane Changing Simulator with the Blind Spot Detector uses the same idea as an actual car with the blind spot detector light. The only difference is, not only does my design have a red light that comes on to signal it is not safe to change lanes, but it also makes a noise from the speaker. This could be useful for users that might not be paying attention or being as observant. In my original design, the goal was to use a sensor to detect motion and alert the driver by not allowing the turn signal to come on, turning on a red light, and playing a loud noise from the speaker. By attaching a sensor, the circuit will mimic a car that detected an object in its blind spot and will trigger the red light and a loud noise from the speaker.

II. MAIN IDEA

For starters, I used Multisim to build a circuit that was similar to the Bike Signaling Circuit from the Electronics Hub. I used common rectifier diodes and an SPDT switch to change which green LED was lit depending on the direction of the SPDT switch. The direction of the SPDT Switch mimicked the left and right blinker on a car. The astable 555 Timer allows the chosen green LED 1 to blink repeatedly. Using the formula, T = 0.693 × (R1+2R2) × C1, where R1 = 27 kΩ, R2 = 27 kΩ, and C1 = 1µF, the green LEDs should notionally blink at a rate of 0.056s.

Remembering how we used MOSFETs to invert which components were on and off at a given time, I used two BS170s and one IRF 520. By connecting these MOSFETs through the gate of the BS170 to the output of the astable 555 timer and through the gate of the IRF520 to the Push Button, I was able to invert the operations that occurred once the push button was pressed.

Though it was not possible to truly simulate the speaker making a sound with a certain frequency, I knew that there were multiple ways to approach the actual generating of the frequency. I considered using a 555 timer to produce around a 400 Hz square wave function. Opposed to using the 555 timer option, I decided to use the function generator to generate a 400 Hz square wave signal. The square wave function would generate a sound from the speaker that played when the button was pressed.

Based on previous labs, I remembered that there were multiple options that could substitute a push-button to mimic a closed and open connection. I debated a few methods for sensing if an object was in the vehicle's blind spot. I considered a CdS Cell that could have sensed the shadow from the object, but it would not be effective at night since it would not have any light at all. The primary method that I considered was using an IR LED and a Phototransistor as a sensor to detect an object. Though the IR LED and Phototransistor sensor was the most similar to real-world technology and, overall, the most effective, I did have a contingency plan. If I could not get the sensor working, then I would use a push button switch as the alternative. The logic is simple, if the button is pressed, then the safety features discussed earlier would be activated until the button is released.

III. CIRCUT SIMULATION

1. Components

• 1 SPDT Switch
• 1 Push Button Switch
• 1 Function Generator
• 1 Speaker
• 2 NMOS BS170
• 1 NMOS IRF520
• 2 common rectifier diodes 1N4007
• 1 555 timers LM555
• 2 Green LEDs
• 2 Red LEDs
• 0.01μF, 1μF capacitors
• 220Ω, 2.2kΩ, 27kΩ resistors

2. Final Schematic

3. Simulation Video

IV. ANALYSIS

I used 9.0V to power this circuit and its components. Using to confirm that the logic that I simulated on Multisim was correct, I first used a push button in the place of the IR LED - phototransistor sensor. The logic worked with a push button, but I could not get the IR LED - phototransistor sensor to work in the place of the push button. Therefore, my actual design on the breadboard was built using a push button as the blind spot sensor. The TRI pin of the 555 Timer is connected to the THR pin, a 1µF, and a common rectifier diode, which then connects to the SPDT Switch. This ensures that regardless of which way the SPDT is flipped, the 555 timer will be triggered.

After countless tests to ensure my 555 timer was working, I concluded that the 555 timer was not making the Green LEDs blink as they did in the Multisim simulation. I tried to lower and raise my resistor values to see if that would change the rate at which they were blinking. I also tested the output on the oscilloscope to see if there was a generated frequency. After countless tests, I could not get either of the green LEDs to blink at all.

The function generator was connected to the button with a 400 Hz (410.66 Hz) square wave. The function generator had no effect red LED. Typically, when a low frequency is given to an LED, it will begin to blink. This was not the case for this circuit because the frequency affected the audio that was outputted from the speaker. Because the resistor was in series with the speaker, the audio was not as loud as when it was connected directly to the speaker.

V. CONCLUSION

The circuit was successful overall in terms of functionality. Modifications could always be made to this circuit in the future to make it more effective. Though the green lights did not blink and the IR LED - phototransistor sensor was not able to turn on the safety features of the blinker system, this circuit was still able to perform the task at hand. Signal left and right and have the ability to detect an object in its blind spot and signal to the driver that it is not safe to change lanes. Because of this, I would say that this circuit was successful overall.

References

[1] Bike Turning Signal Circuit. Electronics Hub. [Online]                    https://www.electronicshub.org/bike-turning-signal-circuit/

[2] Davis, Chad. 555 Timer Notes. ECE 3873, Spring 2021 [Online]      https://www.dropbox.com/s/t41l5yuqfg5nbyg/555%20Timer%20Notes.docx?dl=0

[3] Davis, Chad. MOSFET Lab Part 1 - Characteristics & Switching. ECE 3873, Spring 2021. [Online]  https://www.dropbox.com/s/ujtxu0oyrw5l5s1/MOSFET%20Lab%20Characteristics%20and%20 switching.pptx?dl=0

[4] Davis, Chad. BJT Lab Overview Experiments 1, 2, and 4. ECE 3873, Spring 2021. [Online] https://www.dropbox.com/s/sh33yf9hjos6i4i/BJT%20Lab%20Experiments%201%2C%202%2C %20and%204%20-%20Switching%20and%20CE%20Amp.pptx?dl=0