Intelligent key port aka fobgina question

FricFrac · 03-11-2010, 12:44 AM

Quote:

Originally Posted by antman22

the fob works when in proximity of car. you could have the key sitting a couple feet away from teh car and it'll work. all the fobgina is there for is if the battery runs out, it supplies temporary power to get the fob working. it won't recharge it, but its enough to get the sensor to sync up and start the engine. you realize you don't have to put the key in the fobgina everytime you get in the car right? my keys always stay in my pocket.

i'm not sure what you're expecting out of an "intelligent" key, but that's about it.

Its likely inductive coupling (kinda like the "wireless" chargers for the phone with 40,000 fart applications.... what's the commercial name? Oh yea the iPhone). It probably induces a current in a winding or trace on the PCB in the Fob when you place it in the fobgina. That gives the Fob power so the RFID can be transmitted to the ECU with a dead Fob battery. Its not a simple switch - its an inductive power supply.

rudi · 03-11-2010, 02:24 AM

Quote:

Originally Posted by FricFrac

Its likely inductive coupling (kinda like the "wireless" chargers for the phone with 40,000 fart applications.... what's the commercial name? Oh yea the iPhone). It probably induces a current in a winding or trace on the PCB in the Fob when you place it in the fobgina. That gives the Fob power so the RFID can be transmitted to the ECU with a dead Fob battery. Its not a simple switch - its an inductive power supply.

That sounds like a good answer to me

Modshack · 03-11-2010, 09:10 AM

Quote:

Originally Posted by FricFrac

Its likely inductive coupling (kinda like the "wireless" chargers for the phone with 40,000 fart applications.... what's the commercial name? Oh yea the iPhone). It probably induces a current in a winding or trace on the PCB in the Fob when you place it in the fobgina. That gives the Fob power so the RFID can be transmitted to the ECU with a dead Fob battery. Its not a simple switch - its an inductive power supply.

...Corvettes have a similar set-up/fob slot

Hugoneus · 03-11-2010, 12:07 PM

The principle operation of the FOB inside the keyhole is the same as RFID tags. The keyhole powers the FOB if it has no battery.

semtex · 03-11-2010, 12:31 PM

Quote:

Originally Posted by Hugoneus

The principle operation of the FOB inside the keyhole is the same as RFID tags. The keyhole powers the FOB if it has no battery.

But why do you need to power the fob at all? You don't need to power it to start the car. It's passive RFID, and you can start your car -- fob in pocket -- even with the battery completely removed. The only thing the fob needs power for is for the lock/unlock/horn buttons to work, and to be able to lock/unlock the doors by just pressing the button on the outside of the door. Well, you're not going to be using the buttons on the fob while it's in the fobgina for obvious reasons. And there's no reason to get out of the car while the fob is in the fobgina to hit the external door lock button. I just don't see the functional value of the fobgina. It's not like it recharges a dead battery or something.

Hugoneus · 03-11-2010, 02:03 PM

Quote:

Originally Posted by semtex

But why do you need to power the fob at all? You don't need to power it to start the car. It's passive RFID, and you can start your car -- fob in pocket -- even with the battery completely removed. The only thing the fob needs power for is for the lock/unlock/horn buttons to work, and to be able to lock/unlock the doors by just pressing the button on the outside of the door. Well, you're not going to be using the buttons on the fob while it's in the fobgina for obvious reasons. And there's no reason to get out of the car while the fob is in the fobgina to hit the external door lock button. I just don't see the functional value of the fobgina. It's not like it recharges a dead battery or something.

That is not exactly true. You wouldn't want a passive RFID for your car, they are much easier to duplicate.

In this FOB, the car and the FOB exchange a sequence of encryption messages. Furthermore, the FOB never sends the car the same message twice. A microprocessor changes the sent message every time (based on an encryption key). This is the most secure method.

semtex · 03-11-2010, 02:16 PM

Quote:

Originally Posted by Hugoneus

That is not exactly true. You wouldn't want a passive RFID for your car, they are much easier to duplicate.

In this FOB, the car and the FOB exchange a sequence of encryption messages. Furthermore, the FOB never sends the car the same message twice. A microprocessor changes the sent message every time (based on an encryption key). This is the most secure method.

Okay, whatever. You obviously know way more about RFID than I do. But you completely sidestepped the main point I was trying to make about the fobgina having no functional value in this car (other than being a hole to stick your fob into if you don't want to keep it in your pocket). You previously stated that the keyhole powers the fob if it has no battery. What I'm saying is that there's no value in doing that as far as I'm able to see. i.e., the functions of the fob that require power won't/can't be used while the fob is in the keyhole/fobgina anyway.

Hugoneus · 03-11-2010, 02:39 PM

Quote:

Originally Posted by semtex

Okay, whatever. You obviously know way more about RFID than I do. But you completely sidestepped the main point I was trying to make about the fobgina having no functional value in this car (other than being a hole to stick your fob into if you don't want to keep it in your pocket). You previously stated that the keyhole powers the fob if it has no battery. What I'm saying is that there's no value in doing that as far as I'm able to see. i.e., the functions of the fob that require power won't/can't be used while the fob is in the keyhole/fobgina anyway.

The FOB performs several functions:

1) It allows you to remotely lock/unlock doors and activate the emergency alarm.
2) Allows you to lock/unlock the doors and trunk if you are in the proximity of the car.
3) Allows you to start the car as long as the fob is inside the car.
4) Prevents other people from unlocking your door by pushing the buttons on the door handles.

Obviously the FOB is designed to be beneficial if it has batteries. If it runs out of battery they still provide you with some ways to turn your car on until you replace the battery. If the FOB has no battery, you cannot remotely lock/unlock your car. That is the same with any remote key-less entry system.

My apologize, but I fail to see what your point is. Are you saying that a device without batteries is (mostly) useless? Yes, I agree it is.

semtex · 03-11-2010, 02:59 PM

Quote:

Originally Posted by Hugoneus

The FOB performs several functions:

1) It allows you to remotely lock/unlock doors and activate the emergency alarm.
2) Allows you to lock/unlock the doors and trunk if you are in the proximity of the car.
3) Allows you to start the car as long as the fob is inside the car.
4) Prevents other people from unlocking your door by pushing the buttons on the door handles.

Obviously the FOB is designed to be beneficial if it has batteries. If it runs out of battery they still provide you with some ways to turn your car on until you replace the battery. If the FOB has no battery, you cannot remotely lock/unlock your car. That is the same with any remote key-less entry system.

My apologize, but I fail to see what your point is. Are you saying that a device without batteries is (mostly) useless? Yes, I agree it is.

No, I'm saying that the fobgina is useless, not the fob itself. As I previously mentioned, just to experiment, I have taken the battery out of my fob, left the fob in my pocket, gotten in my car and it still starts my car. So obviously the fob does not need power in order to start the car. So what's left that does require power? Well, you mentioned pretty much all of them above. But here's the rub. You can send power to a fob with a dead battery by sticking it into the fobgina, right? Well, you're not going to remotely lock/unlock the doors or activate the emergency alarm while the fob is stuck inside the fobgina. Or to put it another way, by sticking your fob into the key hole, it'll power up the buttons on your fob, but your access to those buttons will be obstructed by the very fact that you have inserted the fob into the key holder. So what's the point of even having a fobgina to stick it into? As I said, you don't need it to start the car up.

03-11-2010, 12:07 PM	#4 (permalink)
Hugoneus Base Member Join Date: Feb 2010 Location: Milky Way Posts: 245 Drives: 2010 370z T+S+N 6MT Rep Power: 16	The principle operation of the FOB inside the keyhole is the same as RFID tags. The keyhole powers the FOB if it has no battery. __________________ 2010 Cherry Black Nissan 370z + Black Interior + 6MT Touring + Sport + Navigation + Painted Splash Guards + Illuminated Kick Plates + Fog Light + Floor Mats + Clear Bra

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