Final System

Final System

   Combining the previous steps together we came up with a final system that could sense the deceleration rate of a vehicle and pulse a set of LED's when the deceleration was higher than the pre-set threshold. The row of LED's simulated a high mound stop light of a vehicle. The prototype system utilized a normally open relay but a real world system would use a single pole double throw relay so that when no current was coming from the adaptive brake light circuit,it would be closed and the brake lights would work as normal.

This is our final prototype system assembled:

This system has a lot of room for improvement but this is what we came up with in the end. Due to legal standards in New Zealand the brake lights of a vehicle have to emit a solid light. However, hazard lights are a widely recognized signal for danger and are meant to flash. Therefore, if we were to put this system on the market we would be using the hazard light system instead of the brake lights. We would also used a small computer chip to control the system as it would only need to be programmed to run the system and then wired in. The system would also be contained in a small box with the appropriate power and relay wires exposed for installation. A level would also be incorporated on top of the box so that the installer can make sure the system is level and will operate as intended.

Final Coding

Final Coding

   After determining the threshold figure from road testing we could now finalise the coding for the system. The aim is to get the system to print the values being read so that it can be monitored. We also want the system to flash the brake lights for 5 seconds if the readings drop below 290, and complete the circuit at all other times so that the brakes work normally. Since the sensor only dropped below 290 once during testing we figured that the flashing needs to be timed so that it will keep flashing even though the sensor may not still be reading below 290.

 The screenshots above show the coding with the functions also described in the pictures. The system is set to make pin 4 high at all other times because a normally open relay was used for demonstration purposes because we could not find a normally closed. This means the relay will be closed at all other times because it has power to it.

Road Testing

Road Testing 

We had our code set up and now we needed to figure out what values the accelerometer gave under different braking loads. With the arduino board and accelerometer plugged into the computer I could see the values it was reading with the sensor value code and the "serial monitor" feature. The testing was done in a 1989 Honda EF Civic. My project partner drove at 50 km/h and braked to a stop 3 times, once at a slow rate, once heavy, and one emergency stop. I videoed the readings so that it could be reviewed and the threshold value determined. Below shows a screenshot of the lowest readings from the 3 different braking scenarios. When cruising at 50 km/h the sensor was showing reading around 340 for reference.

 This photo shows the values given under normal braking conditions. The lowest value given was 315.



















This photo shows the values given under heavy braking conditions. The lowest value given was 295.
















This photo shows the values given under emergency braking conditions. The lowest value given was 284.
















From this testing we determined that the threshold for when the brake lights should flash was below 290. we figured this would be accurate with most cars as well since the car we were using was quite old and had no ABS.

Test Coding

Test Coding - Weeks 7, 8 & 9 

After a busy few weeks of not being able to work on the project, I sat down and did some research on Arduino coding and the Tri-axial accelerometer. I found a lot of Arduino help but sorting through the stuff that was of no use to me and finding the few pieces of code I needed was the hard part. 

In our project we will be using the accelerometer as a sensor to detect deceleration in order for the Arduino to determine when to flash the brake lights. Therefore, the code I needed was to let the Arduino know what the signals being fed to it meant and to tell it to send power to a digital output when the signal is below a certain value. Below is what I came up with.

This sketch was purely to test the code and get a better understanding for it. The next step is to do some testing on the values given from the accelerometer chip and set up the full circuit with the transistor, relay, and the 4 LED's.

Wiring and Components

Wiring and Components  - Week 5 & 6

After racking my brain trying to figure out how to wire the adaptive brake lights so that if the Arduino circuit fails, the brake lights will still work. I was toying with the idea of adding a resistor circuit which is activated by the Arduino and draws current from the lights to turn them off. However, there is a much simpler solution which uses a normally closed relay which will be switched into the off position to break the circuit. This will be done by the Arduino Uno and an NPN transistor. Below is a rough wiring diagram to display the idea.

The components we will be using are:

Sensor - 3-Axis accelerometer module for Arduino
Though we only require one axis for deceleration we will be using this sensor because its compatible with the Arduino and it is readily available.

Control Circuit - Arduino UNO, BD139 NPN transistor with a resistor added to the base to control voltage and a normally closed relay with a diode for protection.

Output Circuit - We will be using the existing brake light circuit which consists of the switch at the pedal and the lights.

Component Discussions

Component Discussions - Week 3 & 4

After doing our own research on components that could be used to activate the pulsing of the brake lights under heavy braking conditions, I talked to my lecturers about what they thought would be the best to use. We decided that a pitch sensor could work but not all cars have the same amount of dive under heavy braking conditions so the system would have to be calibrated for each vehicle it was put into. The pressure sensor could also be used but again, every vehicle is different and would require testing and calibration for each vehicle. Therefore, the sensor that was agreed upon was the Accelerometer which will sense the amount of deceleration the vehicle is experiencing and activate the pulsing when this deceleration is above a determined value. This value will be decided after additional research of emergency braking maneuvers. A good point that was brought up also, was that if the brake system is not operating as it should then a sensor should be in place to identify if the driver is applying a lot of force to try and decelerate quickly. This will pulse the brake lights and warn following drivers to slow down in the event of brake failure of the lead vehicle which would not produce the desired deceleration.   

Figure 1. Arduino 3-axis Accelerometer. (Jaycar, n.d.).

Reference: 

Jaycar. (n.d.). 3-axis Accelerometer. Retrieved from 

https://www.jaycar.co.nz/3-axis-accelerometer-module-for-arduino/p/XC4478

Initial Research

Initial Research - Week 1 & 2

During the first couple of weeks I researched the issue of rear-end collisions and found that they are the most common type of collision. Though not usually fatal, they do end up costing drivers and insurance companies a lot of money. The main cause of these collisions is distracted driving. Weather it be using a cellphone, changing music, tired driving or distractions from passengers, it is evident that the conventional brake lights are not enough when emergency baking maneuvers are performed. The conventional brake lights also do not indicate the rate of deceleration of the vehicle making it sometimes hard to judge how hard you need to brake.

Figure 1. Rear End Collision. (Ellis Law Corporation, 2017)

After some more research I found that Mercedes Benz had a system to remedy this problem. A system that pulses the brake lights under heavy deceleration was incorporated. It was proven that this system decreased reaction time by 0.2 seconds and shortened stopping distances. By using a pulsing break light it grabs drivers attention more effectively than a conventional solid red light. Once the system is more widely used drivers will become more accustomed to the system and recognize the emergency braking maneuvers quicker and further decrease reaction times.

Figure 2. Adaptive Brake Light Technology. (QY Reports, 2018)

References:

Ellis Law Corporation. (2017). Rear End Collision. Retrieved from https://ellisinjurylaw.com/auto/car-accident/rear-end-collision/

QY Reports. (2018). Adaptive Brake Light Technology. Retrieved from https://www.latestindustrynews.com/4508/automotive-adaptive-emergency-brake-lights-market-automotive-adaptive-emergency-brake-lights-market-latest-trends-growth-rate-profitability-business-opportunities-current-trends-market-challenges/