Arduino based battery on/off and temperature monitoring system

A simple diy project on how to monitor car battery, engine temperature and automatically control the headlights of car with arduino uno. I have pretty old vehicle, which does not have any fancy items/mechanics in it. So i decided to make this project and make my car look a little bit fancy by my self. I decided to add the functionally of automatically switching the head lights on and off depending on the visible light. I used an LDR(Light dependent resistor) for this project but i have plans to moving forward and using a standard lux(light intensity) sensor for controlling head lights of vehicel. I am also monitoring the engine temperature and battery voltage.

Vehicle Temperature Monitoring with arduino and DHT11 Temperature sensor

For temperature monitoring of vehicle engine i used DHT11 temperature and humidity sensor. DHT11 is a 1-wire temperature sensor. DHT11 can measure from 0 degree centigrade to 50 degree centigrade. In my region the hot temperature ever recorded is 45 degree centigrade. So dht11 is pretty good for my diy project. The measured temperature is then displayed on a 16×2 character lcd.

Car battery voltage monitoring with arduino

Car battery supplies 12 v at stationary mode, but when the vehicle is moving the voltage raises to 18 v maximum for charging the battery. Arduino adc(analog to digital converter) can measure max 5 v of. So to measure the car 12 v battery which can jump to 18 v during charging, i used a voltage divider circuit to bring the voltage down to 5 v range acceptable by the arduino adc.

Car autonomous head light control with arduino uno

To switch the head lights of the car on and off automatically depending on the intensity of the visible light i used an ldr(light dependent resistor) to detect the light and for switching i used a small 3 v relay. When ever a dark spot is detected or the car is passing underneath a bridge the 3 v relay is energized and the head lights turns on. I used 3 v relay because i want the relay controlled directly by the arduino digital pins, i don’t want any middle driver circuit for the relay usually transistors and mosfets. Arduino digital pins can source 5 v at 40 mA and my 3 v relay consumes 25 mA so my 3 v relay can easily be controlled by the arduino digital pin.

Inside circuitry of car monitoring and controlling system

Car head light control system with dht11 temperature sensor

light dependent resistor arduino module measuring daylight

The above circuit is what i made at end. I made the circuit on a vero board. I hope that the circuit make sense to you. On left side i have an ldr (Light dependent module). Ldr legs were too small and i need approximately 1 m in length, so i de-soldered the ldr make its legs 1 m long by connecting wires and wrapped around it a black surface plastic.

Whole of the circuit and arduino is powered by car battery. On the above vero board circuit i am dropping some voltage using a resistor and then supplying the rest to arduino. 3v relay supplies power to car head light relay which in turn switches on and off the head light. I did not used any external power supply. Only utilized car battery to control each and every thing.

Final end shape diy car automation project

Main diy car headlight control and temerature monitoring module

Arduino Uno Circuit Connections for car automation using arduino

Arduino lcd shield occupies pins 4,5,6,7,8,9. Dht11 temperature and humidity sensor data output pin is connected to pin#11 of the arduino uno. To measure the battery voltage i used analog channel-1 of arduino uno. To measure the intensity of visible light i used analog channel-2 of arduino uno. To energize the relay digital pin#3 of arduino is used.

Hurdles faced after operating of the circuit in real environment

When i installed the circuit in car and tested it all the things works well. But when i went on long 2 hour tour the module connecting wire to battery melts down. Actually what i did is i used a very thin wire for powering the circuit with car battery. So when car moves on long drive its battery voltage increased for charging. The wire could not hold the large power and wire starts heating and it melts down gradually.
Another error that i found is when we manually switch on the head lights and also the head lights are switched on by the arduino module. The module does not switches off. Its because the current founds a path to flow from the manual side in to the board. I eliminated this error by connecting a diode in series.