Keyless entry

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I'm exploring the idea of making a remote unlock system for an old car of mine.

I was thinking something similar to using RFID tags but I was hoping it could be much longer range. The other option would be to hack a conventional car remote. Does anyone know of any hardware that would do this?

I'd really like to be able to walk up to the car and find it unlocked and have it lock it's self when I walk away.

Pushing AVRs to their limits

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Cinderblock,

Welcome to the forum.

Linx Technologies, LINX , sells OEM Keyfobs. I've never ordered from them, but their advertisements are everywhere.

It might be a good starting point. I'm sure there are others out there.

The automatic operation requirement is an interesting stipulation. At first glance one might aproach this with a periodic inquiry from the vehicle to see if the keyfob is nearby, but this requires the keyfob to be a transceiver, not a simple transmitter, and it has to listen for transmissions from the vehicle.

This will eat up batteries...

One might consider having the keyfob periodically send a signal to the vehicle. No keyfob receiver needed. Vehicle is always listening. No pings in a while, lock the door. Pings present, engine off, unlock the door...

Adding an accelerometer to the keyfob could turn it off when it is stationary for a long period of time.

If you weren't too lazy to push a button once in a while this would be an easier project :wink:

JC

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cinderblock wrote:
I'd really like to be able to walk up to the car and find it unlocked

Use a brick ... or don't lock it in the first place ...

cinderblock wrote:
... and have it lock it's self when I walk away.

Oops ... a brick cannot do that. Back to the drawing board. How about a coded dog whistle ... :roll:

Ross McKenzie ValuSoft Melbourne Australia

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For now I'm just looking for hardware options. Just searching for "keyless entry" or "proximity sensor" on google yeilds results that aren't relevant. I need somewhere a little more specific to start.

Obviously something will need to be done for the battery issue. Maybe it's got a charging station in the car / at home.

The other option is bluetooth. My entire family has bluetooth capable phones. Anyone know how easy it is to simply pair a bluetooth device and what simple hardware would be needed for this? Maybe rev 2 is an iPhone app that would even let you start the car!

Pushing AVRs to their limits

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Here is one BT/uC project for general info and a starting point: BT-GPS .

Although I have seen some very small BT dongles to plug into a USB port on a PC, then BT modules for embedding that I've seen have been much larger..., and more power hungry than the keyfobs sited above.

JC

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RFID would be a good idea but it is not designed for long distances.
Also, as you said, it would be nice for the car to auto switch off itself when you leave it. But you must be sure that the comunication will not lost while you are driving your car.

Michael.

Michael.

User of:
IAR Embedded Workbench C/C++ Compiler
Altium Designer

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I don't think you need long distances... a range of 10-15 feet should be more than enough. You want to be in the immediate vicinity of your car for it to unlock, any further and your car will unlock itself while your in your house, leaving it open for theft.

I second the concerns about the auto shut-off feature. I suggest you stick with the locks, leave the ignition system alone.

[if something goes wrong, a mis-behaving lock is a minor annoyance... a mis-behaving ignition can be a major hazard]

Writing code is like having sex.... make one little mistake, and you're supporting it for life.

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Conrad in Germany sells a keyless entry kit that does exactly what you want.

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True Passive entry systems uses multiple technologies. Everything from LF (125kHz) to UHF (300-900MHZ) to create the system. Cool stuff.