To help to protect owners' cars I have designed the device based on GPS/GSM localization. When the car has clear sky view it would get a geolocation fix via GPS and when GPS signal is not available, the pinpoint position would be established based on GSM base stations only, since GSM signal penetrates through buildings. In urban areas a GSM based location fix accuracy is about tens to hundreds meters and in country sides it is more likely to be kilometers. Still, it is a good starting point for the police to find your stolen vehicle.
The system overview is presented in pictures below.
The Geckolizator is a battery operated device (Li-Po 1500mAh cellphone battery). It also has battery charger implemented. This is the 5V/500mAh MAX1811 USB charger. When the car engine is turned on and the 12V is available in the car, the device recharges battery using 12V/5V car adapter. What you do with Geckolizator is you hide it somewhere in your car and connect it to this 12V/5V adapter. When you leave your car in non secure location (or even in your garage), always arm it (turn on). The system will initialize the accelerometer (MMA7455L) and go into EM3 mode. EM4 could have been used, but I could not find EM4 wakeup pins on EXP, so I have used EM3. Now, when someone manages to steal your car and drives it off, accelerometer generates interrupt. EFM wakes up, turns off accelerometer and turns on HOPE's GPS reveiver (GPS03) and Sagem's HiLo GSM/GPRS modem. Now, when GPS signal is valid after a few seconds, the system sends SMS with localization data. If the GPS signal is not valid (not clear sky view and when your car is already inside a truck :) heading somewhere), the Geckolizator uses GSM base stations signal to check the possible location with a use of Google's databases and also sends you SMS. Then EFM turns off GSM modem, but leaves GPS receiver to maintain signal availability or to get a fix which was not available then and EFM goes to EM2 for a programmed time (in the demo, it is 5 minutes). After this time it wakes up and starts localization scheme one more time and sends sms. This is being done until you turn off the device, there are no more money on SIM prepaid card or battery drains out. EM4 with GG can also be used for timed wakeup.
Why I have used EFM? When you do not use your car very often, you do not want to drain your car battery (especially in winter) if you have 12V in your connector when engine is off. In the same time you want to keep your car safe and monitored by Geckolizator. That is why EFM are the perfect fit for this design in my opinion.
- Implement EFM on Geckolizator to get rid off STK in the car
- Change GPS enable MOS for low power switch
Edited by Rasmus, 07 February 2013 - 04:10 PM.