Long distance remote operation - check this out

[bmwrocks]

Got this in email the other day, I couldn't think of any reason why it would work, and decided to try it anyways.....

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WHEN LOCKED OUT OF YOUR CAR Easy way to unlock your car (If you have
the right equipment, etc.) Hi, All You Forgetful People and there are a lot of us. This only applies to cars that can be unlocked by that remote button
on your key ring. Should you lock your keys in the car and the spare keys are home, and you don't have "OnStar," here's your answer to the problem! If some one has access to the spare remote at your home, call them on your cell phone (or borrow one from someone if the cell phone is locked in the car too!) Hold your (or anyone's) cell phone about a foot from your car door and have the other person at your home press the unlock button, holding it near the phone. Your car will unlock. I tried it and it works. Saves someone from having to drive your keys to you. Distance is no object. You could be hundreds of miles away, and if you can reach someone who has the other "remote" for your car, you can unlock the doors (or the trunk, or have the "horn" signal go off, or whatever!) Too cool!
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Well, it worked for me at a distance of 500 yards. I had my daughter stand at the car and I walked to the other end of the parking lot. I had no line of sight to my car, blocked by many other cars. I then called her cell with mine and worked the remote near my cell and low and behold the remote opened/locked the car!!!!!!! I want to try it at a longer distance (miles) but haven't yet.

I am not sure if the signals were just amplified by my phone or if it truly passed over the phone, didn't experiment with it.

Anyone else ever heard of this?

 

[tool fan]

Freakin cool post man, I am definately going to try that.

 

[Kirby]

I gotta try this! It can't work, it shouldn't work, there's no logical way it can work, but clearly it worked for you.

 

[epj3]

I agree, I don't understand how it can work. A remote transmits at a high radio frequency, and cellphones only transmit voice between a limited number of AUDIBLE frequencies.


Here: http://www.snopes.com/autos/techno/keyless.asp?print=y

 

[codex57]

I don't see how it can work either, but hey, it wouldn't be that hard to try. Someone try it out. I would but stupid Cingular gets no reception in my neighborhood.

 

[theBMWenthusiast]

anyone try this yet? i dont got a spare key so can't really check it across distances...plus no cell phone service in my neighborhood either

 

[xLibelle]

i spent 4 months calculating this stuff out in school... not opening car doors through cell phones, but the cell phone encoding methods and the signals that the car remotes send out.

i am a member of IEEE (a world wide electronics group) and in one of their publishings, they talked about the technology cell phones are using and extra things that they are capable of. For example, if you so much as put the cell phone up to your ear, your vital signs (such as ekg) are being sent over the phone all the time. Only thing thats needed to be done with this to make it worth something to, say, 911, is to include the proper filters.

On this topic specifically, cell phones use Pulse Amplitude/Code Modulation (PAM or PCM)... one of them anyway. There are many of them (in which we studied all that were relevant at that time) but its most likely close to that.
Your car remote also uses some digital modulation encoding method so when you hit the button, the cell phone picks up your remote code and combines it into the cell phone signal. Then over to the receiving end and "decoded" by that phone, to create the car remote signal.
Only one thing that confuses me is ... (well, i cant explaing the exact process in detail, so you could say the whole thing confuses me, but the concept is simple).. is the reason you have to have the cell about a foot from your car. ....ok, heres a theory - speakers and microphones *are* capable of signals well below and above human vocal range. the car remote signal could actaully be "played" through that speaker coil, acting as an antennae... sooo, then the signal could actaully be weak (or strong, how ever you want to look at it) enough to need to have it close to the car.

DAMN I LOVE THIS STUFF

 

[MrElussive]

I agree, I don't understand how it can work. A remote transmits at a high radio frequency, and cellphones only transmit voice between a limited number of AUDIBLE frequencies.


Here: http://www.snopes.com/autos/techno/keyless.asp?print=y

Maybe the guy should have actually tried it before labeling it as rubbish.

I think I will give it a try. My only question is, do you need both people on the phone to be using cell phones, or can the "sender" (the person who has your keys) be on a land line?

 

[xLibelle]

from my explination (in theory), and knowledge of how a land line works, you have to both be using a cell phone.

The cell phone picks up the car remote signal and sends it to receiving phone - a very important half of process needed for this to work.
A land line only supports like 50 Hz to ~4 kHz and the remote transmits at a much higher frequency so there is NO way at all, that a regualr phone can pick up the signal.

but i think it might have to be a digital signal too. not sure about gsm or analog signals

 

[andreyiv]

This is something. I will try to do that to a person or two. Guys, it would be awesome if you call one of your family members and when they lets say leave the car and are talking on the phone with you, you can unlock the doors again if the other transmitter is with you. It would be an AWESOME way to freak somebody out. Or lets say trick BMW (or any other company for that matter) into a lemon or something, hahahahhahahaha. I bet you someone will actually do it. Sick of the car, come to the dealership with your phone in your pocket and have a friend do this over the phone only at needed times. I will deffinately do that to my dad, he always keeps the spare keys in the house, just have to get the timing right and do it after he leaves work, unlocks the car, reaches for the handle and oops, it is loked again.

 

[Kirby]

.... Only one thing that confuses me is ... (well, i cant explaing the exact process in detail, so you could say the whole thing confuses me, but the concept is simple).. is the reason you have to have the cell about a foot from your car. ....ok, heres a theory - speakers and microphones *are* capable of signals well below and above human vocal range. the car remote signal could actaully be "played" through that speaker coil, acting as an antennae... sooo, then the signal could actaully be weak (or strong, how ever you want to look at it) enough to need to have it close to the car.

DAMN I LOVE THIS STUFF

...

from my explination (in theory), and knowledge of how a land line works, you have to both be using a cell phone.

The cell phone picks up the car remote signal and sends it to receiving phone - a very important half of process needed for this to work.
A land line only supports like 50 Hz to ~4 kHz and the remote transmits at a much higher frequency so there is NO way at all, that a regualr phone can pick up the signal.

but i think it might have to be a digital signal too. not sure about gsm or analog signals

I agree with your fundamental analysis. The stumbling block is that the remote control generates RF (radio frequency) signals while the cell phone speaker generates AF (audio frequency). Even if the remote control's digital signal somehow got mixed into the audio, and it actually made it cleanly through the cellular phone system (which is 99.99% unlikely) the cell phone at the car would have to RF modulate the digital code at the remote's frequency to unlock the car.

I have a similar, but still very unlikely, explanation. This would work ONLY if the cell phone signal stays RF - either the transmitting phone is a few hundred yards from the car or both phones are communicating on the same cell tower and the cell tower repeats the RF. In this case the remote's RF could be heterodyned (mixed) with the transmitting cell phone's RF and then received by the car. The problem is that this would require sloppy electronic design and a lot of random luck for the frequencies or harmonics to actually match up. In theory, maybe, but in the real world this would be SO unlikely.


I will be able to try this tonight. I don't expect it to work, but if it does, I will probably spend way too much time trying to figure out HOW it works....

 

[xLibelle]

after i explained how the signal was lastly sent from phone-to-car, i relized my thinking on remote-to-phone was a little flawed.... heh, but general enough for someone to not call me out on it. ...but you guys get the idea

Edit: and its doubtful that that these communication systems are *that* sloppy. Yet gsm is not only an entirely new technology on cell phones, its considered an upgrade. so "first gen" could be considered "sloppy".

I was going to say, sloppy could be considered your home mobile phone... but those are only RF transmitters.


Here is one of my projects out of this class that i have pictures of. Its basicly a PCM communications system. you can select out of two encoding methods and three frequencies. You plug in mic and head phones.... pointless because youre standing next to each other, heh.

thinking about it now... uhg, nevermind... my professor was this chineese dude that wrote the freekin book on this stuff - talk about a fun semester. (and i said i wanted to be challenged. actually, i learned more in that class than in a whole year)

 

[Kirby]

Nice circuit layout. I can't quite makeout the IC markings, but let me guess. It looks you used the LM386 audio IC as an input amp in the upper left and right? Frequency divider in the center breadboard to divide the crystal to the working PCM frequencies? What did you use for the A/D and D/A conversion?

Yup, you can learn more practical stuff from a good hands on project in one week, than a whole semester of book theory. That's good stuff you got going on there!

 

[Kirby]

I tried the "experiment" with the remote and cell phones tonight, and it didn't work.

 

[aNoodle]

I tried the "experiment" with the remote and cell phones tonight, and it didn't work.

BMWrocks, how far away did you say you were?

Anyone been able to replicate this, or is this cold-fusion?

 

[andreyiv]

I tried this today, just an hour or so ago with my neighboor with his Infinity SUV and it did in fact work. He walked far far away and it still worked so then he walked just a little farther and it stopped working. I call him, he puts the remote right next to the phone and I stand by the car, guess what, it worked. I have a Verizon phone and he has Cingular I think so go figure. We'll try it again sometime soon but farther away, like a mile or so away.

 

[epj3]

It's impossible! Absolutley impossible. Unless the wireless carrier built in a reciever/transmitter into their phones that could operate on an additional frequency, and then transmit that VARIED signal (Changes all the time due to security) to another phone.

I think you guys are getting it to work simply becuase of the placement of the remote in relationship to the car. Kind of the same reason if you put the remote under your chin it seems to get better range.

 

[andreyiv]

Could be that too, thats why we will try it out at a greater distance. He did get VERY good range with the remote, I mean really, the distance was so great that I saw him but could not make out if lets say his eyes are open or not, I have 20/20 vision btw. I'll report on how it goes.

 

[DRAGO]

I tried this and it dosnt work it worked when i put the key under my chin. but not with the cell phone .

 

[bmwrocks]

I was 500 yards away. The remote stopped working normally at about 10-20 yards.

I think the remote just used my phone as an antenna and that increased the range (like the chin method).

Someone needs to try just holding the remote near the phone and not linking up with the other cell and see if that works. Then try it at a mile without linking up (no way this would work). Then link up and see if it works. Case closed.