Keyless entry has been used for quite some time in automotive industry by most car manufacturers even though such a system may not be in their standard package. The owner receives a card or a small device, much like a remote control, and just by approaching the car, no buttons pushed, the car senses the master and opens its doors.
In this project is presented a method to build your own keyless entry system. Your RFID will be a Nike footpod which will send the secret code to its iPod receiver. This receiver communicates with an Arduino Pro Mini through an iPod Serial Board. The Arduino listens for the right code from the RFID and gives lock/unlock commands.
You can give these commands to your car’s fob or adapt it to the internal wiring of the door’s lock/unlock mechanism. This can be pretty tricky for there are several systems used for door locking. In some European cars like Volkswagen, Seat, Skoda the command for lock/unlock is given on a single wire. For example if on this wire the computer sees a firm ground then it will unlock if it sees a resistance to ground then it will lock or the other way around. In these case you will need to use diodes or relays.
Asian cars usually have two wires, one for lock one for unlock. You will need negative or ground to control these wires. Things complicate however with the more expensive cars as they use vacuum systems or sophisticated computers inside the door. Usually these cars when equipped with a factory keyless entry system have a sensor behind the door handle that must be triggered in order for the doors to unlock, even if the car senses its owner nearby.
Powering our keyless system requires that you find a permanent 12V supply in your car. Look at fuse box, under the driver’s kick panel behind the steering wheel for thick wires and use a multimeter to measure the voltage. Do not trust thin wires as their 12V can disappear after car’s computer falls asleep. Usually that happens between 15 to 30 minutes after locking the car. Be careful with this because serious damage can be caused.
Other difficulty you can experience, as the project’s author did, is the car’s door locking settings. If you unlock the door but do not open it the car might lock it again after a short period of time. You can change these settings from the car’s computer with a diagnosis tool.
RFID Keyless Entry: [Link]
Since I often find myself on the road with my battery drained out and because I intend to use my Eee Pc together with a GPS module as a navigation system I thought it would be a good idea to make myself a car charger. The charger would have to output 9,5 V 2.5A, and it would have to be able to maintain the output voltage constant over variations of the input voltage. Of-course there are lots of voltage regulators these days that would fit my circuit, but I chose to use the LM2576 because such a charger has already been build and tested here (also featured on Youritronics here).
Here is the schematic of the charger:
After ordering the needed parts I noticed that the inductor is slightly bigger than I expected it to be, so fitting the board into a small box became a bit of a problem. But I managed to designed the board so that it fits into the chosen box. I also fitted a medium sized TO-220 radiator so the circuit would dissipate the heat even in continuous use of the charger. The pcb was made using the photo etching technique and I tried spraying it with a mix of colophonium and alcohol that would act as a soldermask. The result is not pretty but I hope it will protect my board from corrosion.
After the soldermask dried it was only a matter of minutes until I assembled and tested it. The charger works great, the output voltage remains constant over continuous variations of the input voltage. Now all I have to do is close the box, solder a cigar lighter connector and pack it into my arm rest compartment.
This project was send to us by Bob Ashlock, who is rightfully proud of his achievement, he made a temperature gauge with the LM34 sensor and PIC16F684. He inspired he’s project from this PIC16F84 thermometer that was posted here on youritronics. The sensor has 10mV/F output, not to be mistaken with the LM35 which has 10mV/C output, but the firmware can be easily adapted.
The source code is well documented, but there is room for optimization, yet taking into consideration that this is Bob’s first project and he learned by himself its a great code. The outcome looks very nice and has its practical use, he used to measure the air and oil temperature in his 66′ Porsche. In the download you have the schematic and source code written in C.
Great job, and thanks for sharing with us your project and experience.
Car temperature gauge: [download]
If you have an old car, and you want to measure the fuel consumption to adjust your driver technique then check out this device. It is build around one Arduino board, off course the project is open hardware like any other Arduino project, the LCD is a simple two row alphanumeric display, nothing fancy about it. To power up, just tap into the battery, connect it anywhere you can find +12V.
The device only works on cars with injector based fuel distribution, by counting the pulses and the time which the injector valves are open, and using a calibration table it computes the fuel burned by the engine, the device has also a menu to access some settings, you can even display the CPU usage in %.
With a little work you could also integrated it into the dashboard, probably won’t increase your old cars value, but it will look good and its a great DIY project.
Fuel consumption calculator: [Link]
The Gas Guzzler Meter is an attempt at putting an immediate dollar value on your current driving techniques: a digital meter that displays exactly what you’re spending as you motor along. Stomp on the pedal and see the bucks zoom out your tailpipe faster than a NASCAR driver competing for the Nextel Cup. This device will help you impress your friends, drive responsibly, and keep those dollars in your pocket.
Gas Guzzler Meter: [Link]
