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RF Car Locator

RF Car Locator

A Car Locator devise is a device used to identify the direction of a parked automobile. This device was designed conceptually, actualized by several circuits that performed specific tasks, tested, debugged, and a working prototype was produced.
The main feature of the Car Locator is to identify to the user, the direction the car is parked. In order to accomplish this task, RF principles were used. The car would have a transmitter placed on the vehicle. This transmitter would emit an RF (radio frequency) signal. The Car Locator device would be a hand held unit that receives the RF signal. The user would then sweep the Car Locator device in an arc (refer to Illustration 1) and when the directional antenna in the hand held unit detects the RF signal, the user would be notified via a lit LED that the direction he or she is pointing the hand held unit in, is the direction the car is parked.

As a user walks out onto the parking lot, the vehicle could be positioned in any arbitrary location with respect to the user. The user then takes out the device and starts to sweep it in an arc as previously discussed. The user would stand at a fixed distance from the car. The omni-directional antenna would receive the signal and the RSSI chip would output a voltage with respect to that distance. If the user is pointing the unit in a direction not aligned with the car, the output of the RSSI chip from the directional antenna would be less than the output of the RSSI chip from the omni-directional antenna. The difference of these two voltages would be taken and compared to a set threshold. If that voltage is not smaller than the set threshold, the LED will remain off. As the user sweeps the unit in the arc, and as the directional antenna is eventually pointed in the right direction, the output of the two RSSI chips would be very similar. The difference again is taken, and compared to the threshold. At this point, the difference would be smaller than the threshold voltage, and the LED circuit will turn on. Thus the user is able to identify the direction of his or her car.

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