Slimline Proximity Fob Makes Life Easier

Modern cars these days tend to come with proximity keys, which allow the driver to unlock and start the vehicle without having to remove the key from one’s pocket. While this is a great usability upgrade, for some reason key fobs continue to be bulky plastic monstrosities that when stuffed into a pocket can easily ruin the lines of a well-chosen outfit. This wasn’t good enough so [Patrick] decided to sort it out.

Starting with a Prius key, the first step was to disassemble the already broken key fob and separate out the PCB from the case and battery holder. With those removed, a coin cell was soldered to some wires connected to the PCB. As a substitute for the original case, a plastic card was cut up and the PCB inserted within, allowing the setup to fit neatly in a wallet’s card pocket. Lashings of tape bring the project home.

Unsurprisingly, it works, and works well. It raises the question why key fobs are so large and ungainly, taking up so much precious pocket space. We’d love to see even slimmer takes on this with 3D printed enclosures or even completely redesigned PCBs. Give it a go, and hit up the tip line. Else, check out how key fobs are routinely hacked to steal cars.

43 thoughts on “Slimline Proximity Fob Makes Life Easier

  1. Or, you know, go for Renault which has been using key fobs the size of a few stacked credit cards for ages…

    Fits easily in your pocket without being noticeable, or even some wallets.

  2. Am I the only one who doesn’t like proximity keys?

    I don’t so much mind keyless entry systems that lock or unlock keys with the push of a button, but I’ve always liked taking my keys out of my pocket, putting a key in the ignition, and turning it to start the vehicle.

    I find it more comfortable to have the keys hanging from the ignition rather than being in a pocket, and the muscle memory of grabbing the keys from the ignition, exiting the car, locking it, and putting them in my pocket is ingrained after years of performing those actions.

    It seems harder to avoid them with modern cars, and I have it on my car, but I still find it annoying.

    1. My keyless Volvo still has the slot in the dashboard where you’d insert the fob if you had the non-keyless version. Normally I keep the key in my bag which goes with me every day to work, which makes life easy.

      The problem comes when I’m going somewhere without the bag, not so much as remembering taking the key out the bag, but what to do with the key when I’m in the car. It just feels wrong to put it in the slot on the dashboard, so much so that I try and put it anywhere other than the designated hole :)

      1. The slots are also normally there so you can still start the car if the battery in the fob dies. On Toyotas without a slot, you touch the Toyota logo on the back of the key to the start/stop button if the battery is dead. (I’ve also seen cars that have a “smart key” but you still have to put it in the slot in the dash for it to actually work vs it being a proximity key)

      2. My keyless motorcycle just has the ignition re-routed to a hidden toggle switch under the fuel tank. I left the keyhole just to make it look like it’s still needed and deter lazy theft. Works great. I did it one day when my key broke in half and I got stranded at work. Ain’t need no stinkin key.

    2. You’re not the only one.
      I had vague misgivings about them until I saw the episode of Top Gear where one of the presenters drove the other two presenters cars down the road a few hundred yards while the other two were sitting in a pub. I think the point was to demonstrate that in a similar situation, it would be extremely easy for a thief to hop in the car and drive it right onto a waiting flatbed just around the corner.
      I’d much rather have an ignition that requires a physical key. While it can still be defeated by a determined thief, the process is not as easy and way more obvious to onlookers.

      1. you’re assuming it wasn’t a ‘rigged’ prank of the tv show. i’ve accidentally left my keys on my trunk lid in the past, and the car won’t start, but will unlock. but i’ve also dropped my keys inside the trunk, and the car will start, but will refuse to lock.

        in my case, i believe my subaru makes a sort of faraday cage out of the body. anything within the cage allows the car to start. anything outside the cage controls lock/unlock functionality.

    3. That muscle-memory of physically handling the keys is something I’ve almost lost and it’s caught me out as a consequence: having become so used to having my keys in my jacket pocket, I’ve walked out to my car with a load of things to put in the car, only to find I’d not actually picked my keys up. Luckily I live in a quiet area so I don’t mind abandoning some things next to the car while I run back to pick up my keys but it’s frustrating when you find yourself in that situation.

    4. Nissan Qwhatever, if the door switches are sticky you can drive the car anywhere without the key once started.

      Passenger had the key and the switch was not working (door always closed according to computer), dropped him off and went to shop to pickup some filters and just before shutting down realized I had no keys.
      Drove back to the owner and as soon as I opened the door (still running) the car started beeping and warning about the key.
      The car made no checks during the drive (I drove about 15 mins without keys in car) if doors are not opened and it has been running for a while.
      Makes sense why they succeeded stealing cars with just RF repeater near the keys.

      1. Even with working door switches, a Nissan will continue running without the key. It’s a feature to avoid shutting the car off while driving because of a momentary failure to sense the key.

  3. It took me quite a while to get used to my current car’s keyless entry/start but I actually like it now. I have to press a button on the door handle to lock and unlock which I prefer to the type that unlocks as you approach.

    Whist the idea of making the fob smaller is appealing my fob contains an emergency key that can be used to get into the car in the event of an issue with the keyless entry system or the fob losing power which I find quite reassuring to know I have the backup key hidden inside the fob!

    1. Try gripping a small toolbox key, putting it into the slot the right way in the dark, at -5C, while it is sleeting sometime. Then you will understand why the heads of auto keys are generally large and grippy. The fobs tend to be, as well, so that they don’t get lost and can be gripped and positioned by feel to press the button (the weak link on many, being too small to find by feel or press with a glove or mitten on). I would guess the proximity types are similar due to design inertia- Thats how they were, and people are used to it, so why change to a design that someone might like less?

      1. I never had any problem with the older car keys that had metal heads maybe 3 cm across and 1.5 mm thick. It’s the extra thickness of the plastic heads that causes problems on my key ring.

  4. They are large to a reasonable degree because of perceived consumer value being associated with it. For many individuals, a car is a significant purchase and the key is one of the few car items that are regularly interacted with by the consumer on a nearly daily basis. The idea being, if every time they reach for the key, it makes the customer feel negative about the key, they are not going to feel as happy or positive about the vehicle either, even if the link is actually tenuous at best. Nobody wants to buy a five figure (or more) vehicle and then every time they go to interact with the vehicle, they are disappointed or let down before they even get inside the vehicle.

    It’s along the same lines as car manufacturers burying the access or even sight of the engine behind layers of decorative plastic and making it more difficult for the end consumer to do anything to their vehicle, which often times extends to service of the vehicle. Even going so far as to make it difficult for actual repair shops to actually perform repairs on newer vehicles, which delves into anticompetitiveness and other legally and other societally thorny issues.

    Additionally, there are fairly large security implications of proximity keys (as well as some patent issues depending on the municipality) but the current trend seems to be that car manufacturers believe that the value you place on a large key outweighs the idea of it being small and convenient to carry. To a certain extent, it is difficult to make a fob be both small, durable, long lasting and contain multiple physical buttons but also be below a certain form factor. Plus, if everybody else has an “impressive” (however you define that) key fob and your car does not, it very well may impact sales enough to force a manufacturer to make these fairly bulky keys simply because other companies are doing it.

    They certainly could be smaller and still function and be completely usable. Most people have no idea how much engineering goes into otherwise totally junk things like making the driver door “sound” impressive when you close it.

  5. In some fobs (like the ones for my “primo” 2002 Hyundai Elantra) the thick water-resistant gasketing adds significantly to the thickness. Especially around the buttons, this gasketing needs to survive thousands of presses without tearing. The fob itself isn’t too large, which is why it easily jumped out of my pocket one snowy morning, followed some short time later by its untimely (and utterly gruesome) demise vis-a-vis the infamous Snowblower Incident of 2015.

  6. Would it really have been too much trouble to include a picture of the thing in the article? I can’t always watch the linked video just to see what the final product looks like.

    Even a bad picture of the hack would have been better than a stock photo of a Prius…

        1. Last I checked, like many people living in the middle of a big city, she doesn’t own a car and therefore would not have that problem. Although if she did, I’m sure she’ll be able to 3D print a custom holder for the key after just an hour or two of design work.

  7. One part of the reason the fobs are so large is that many of them contain a metal emergency or valet key. In the emergency key case, it is there so you can get into the car if the battery dies. In the valet key case, it is there so your glove box can remain locked when you hand your key fob (minus the valet portion) to the valet. The first case can be important if you have a dead battery. I’m not sure if anyone really uses the valet key feature, though.

    1. Valet keys also (often?) limit the vehicle speed to 35 mph (do the metric conversion yourself).
      That prevents the valets from seeing just how fast that Mercedes/Ferrari/etc can go.

      Come to think of it, O.J. Simpson probably grabbed the Valet Key by mistake when he took off in the white Bronco.

  8. Two Reasons I can think of as to why the fobs are so large:

    1) dimensions and large buttons provide for a user experience that accommodates many types of hands, levels of dexterity, and insulates (to some degree) from loss/misplacement.

    2) The mechanical backup key – most keyfobs contain a key for unlocking the door, in the case that fob’s battery is dead or the auxiliary battery can’t power the unlock radio.

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