Fail-safe for keyless entry

I've got the typical minivan keyless entry keychain fob but it's got a serious design problem.

The buttons depress too easily and often accidentally when the fob is pushed into a pocket or a purse. It's happened more than once, so it's time to do something about it.

The real estate inside the fob is very cramped. It runs off a CR2032 coin cell battery, and the circuit traces are simple enough so that I could scrape off the 3VDC+ line and bridge it with a small switch. That way, I could just put in a tiny pushbutton that had to be depressed as well as the desired command button each time a command was sent. That approach makes it a two-handed operation, whereas a slide type ON/OFF switch could still be worked with one hand.

The problem is that I don't see any space in the fob for the kinds of switches I am used to. The ideal solution, of course, would be for the manufacturer to put something that's found even on most throwaway $10 MP3 players - a hold button that locks out the buttons when so desired. You'd think with what they charge for a replacement fob they'd include something like that.

I *might* be able to work a small slide or lever switch inside the fob, but it's tight. In the interim, I made a clamshell type case made of hard clear plastic bubble packing material and one of those retracting string keychain things so I can slide it out to activate it and then let the rewinding mechanism withdraw it. So far, the hard plastic sheath has reduced the accidental openings, but it's butt ugly, ungainly and not a very good solution. Plus, it came unglued more than once. There's a lot of interesting stresses in pockets and pocketbooks. Ideas, anyone?

Thanks in advance!

-- Bobby G.

Reply to
Robert Green
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Hmm, More likely you'll end up dead fob. I'd rather carry it in a little sturdy pouch if I need to.

Reply to
Tony Hwang

I just leave the fob at home and use the key.

-Brian

Reply to
rtandems

Don't put the fob in your pocket or purse until you are out of range.

Cost: $0.00

Reply to
mike

How about a tiny nylon washer or O ring under the pushbuttons? That would require more effort to push the button, and reduce accidental activation.

Reply to
JimH

Here's what worked for my wife's 2005 Ford Taurus, with the factory installed anti-theft system:

1 - Have an after-market Remote Starter installed. You will get a fob specific to that starter. 2 - Whenever you exit the vehicle, lock the doors with the switch mounted on the door, not with the Remote Starter fob.

You will never accidentally (or intentially) unlock the doors with the Remote Starter fob, because...

The Ford's anti-theft system is set up so that if the doors are locked with internal door switch, it arms the system such that the *only* fob that will unlock the doors is the factory fob, which, of course, is hanging on the hook at home because you only carry the Remote Starter fob.

Reply to
DerbyDad03

"Robert Green" wrote in news:hqi2ge$6a7$ snipped-for-privacy@speranza.aioe.org:

Before you scrape circuit traces or install switches, please try a simple experiment:

Remove the battery for a few hours (as if you had turned off the switch), then reinstall the battery and see what it takes to unlock your minivan.

Many keyless entry fobs use a trickle of battery current to maintain state information (such as where they are in a rolling code). The system can reacquire the state, but it may take multiple presses. Furthermore, since the state after power-off/power-on is likely to be the same each time (for the same fob under similar conditions), you may be defeating the purpose of the rolling code.

I may be wrong, but the experiment is a lot easier than all of the wasted work if I am right.

Good luck!

Reply to
Ian Shef

Had same problem. Glued small O rings around bottons with super glue. Problem solved. CAUTION don;t get any glue into edge of switch buttons. ww

Reply to
WW

Robert Green :

I had a similar problem with a Garmin GPS. I put a ring of hot-melt adhesive on the surface around the button(s). It was a tricky job but it looked good and worked perfectly.

Reply to
Mike Barnes

So, how do you get in?

Reply to
DT

Perhaps a leather jacket for a small penknife or similar would protect it from light touches.

I have the same problem and I swear I have never pushed some of the buttons. The more embarrassing one is the horn alarm button that seems to be even easier to hit in my pocket.

If you hack into the unit and have to take it to the car dealership, to be replaced, you may find yourself talking to police authorities with lots of questions.

The buttons depress too easily and often accidentally when the fob is pushed into a pocket or a purse. It's happened more than once, so it's time to do something about it.

The real estate inside the fob is very cramped. It runs off a CR2032 coin cell battery, and the circuit traces are simple enough so that I could scrape off the 3VDC+ line and bridge it with a small switch. That way, I could just put in a tiny pushbutton that had to be depressed as well as the desired command button each time a command was sent. That approach makes it a two-handed operation, whereas a slide type ON/OFF switch could still be worked with one hand.

The problem is that I don't see any space in the fob for the kinds of switches I am used to. The ideal solution, of course, would be for the manufacturer to put something that's found even on most throwaway $10 MP3 players - a hold button that locks out the buttons when so desired. You'd think with what they charge for a replacement fob they'd include something like that.

I *might* be able to work a small slide or lever switch inside the fob, but it's tight. In the interim, I made a clamshell type case made of hard clear plastic bubble packing material and one of those retracting string keychain things so I can slide it out to activate it and then let the rewinding mechanism withdraw it. So far, the hard plastic sheath has reduced the accidental openings, but it's butt ugly, ungainly and not a very good solution. Plus, it came unglued more than once. There's a lot of interesting stresses in pockets and pocketbooks. Ideas, anyone?

Thanks in advance!

-- Bobby G.

Reply to
Josepi

And we have a winner! I got 1 huge ungainly combined key and fob with my used 05 mopar van. Stopped at locksmith on way home, and got 2 chip-but-no-button keys to use instead. Only downside is, only doors with keyholes are driver door and hatch.

Reply to
aemeijers

You have to use the key.

Reply to
DerbyDad03

So what does the remote starter gain you, then? Just leave the fob at home and use the key.

Reply to
aemeijers

Still wind up with a dead battery...... May also set off a terrorist bomb.

TDD

Reply to
The Daring Dufas

Even if there's only a "remote" possibility of the unit losing its programming (I couldn't resist the pun!) it's a good thing to check. Very good contribution, Ian, and it's a good reminder to always get someone to review project plans!

Before reading your post, my latest thought was to cut out some thin plastic the same size as the battery, place a contact on it, and slide it between the battery and the case so that the battery can no longer touch the contact on the board and then lead the contact that I attached to the plastic insulator, run it to a tiny switch (maybe a small membrane switch attached to the back of the fob) and then solder a return wire to the battery contact on the board that would now be prevented from making contact with the battery except through the new pathway. Only one point on the fob circuit board needs to be touched doing it this way, and no traces need to be cut.

Now I'll just unload the battery from one of the keyfobs and see what happens.

Your post got me thinking that there has to be some way of keeping the battery alive but still require a second switch to complete the circuit. Perhaps there's a common line from the switch to the ground that could be interrupted so that it needed to be closed when the desired button was pressed. Thanks for reminding me it's a good idea to try to come up with a solution that doesn't affect any trickle current going into the IC.

I guess it's time to take pictures of both sides of the board and come up with a rudimentary circuit diagram.

Thanks for the heads up.

I'll need it. Experience suggests I may, as Tony predicted, end up with a dead fob but you know the old saying - experience is gained proportional to the amount of equipment ruined.

-- Bobby G.

Reply to
Robert Green

That's what I normally do, especially on things like pocket voice recorders that have an "itchy" delete button, but this is a "designer" sort of device, with curved, triangular shaped buttons arranged in a circular pattern. Very hard to "washer up." The best thing would be if I could somehow make a casting of the outer shell and build a second layer of plastic in the same shape and size as the current cover.

I'd grind down the tops of the buttons, but they are cast rubber membranes and that wouldn't work. JimH's solution of putting washers inside on the circuit board to make depressing the switch require more force has promise, but it may be hard to implement without a lot of trial and error sizing.

JimH, if you are reading this, your idea gave me another one, in combination with this one. I can put a spacer between the two halves of the fob and raise the frame around the buttons about an 1/8" higher all around and that might be enough to solve the problem with the minimum of effort and bulk. A

1/8" thick piece of plastic, a tracing of the top half, a little drill and Dremel work and it could do the trick.

Thanks for the input, WW

-- Bobby G.

Reply to
Robert Green

I don't wanna be a dead fob. Sounds awful. (0:

The problem is that it's a weird, rounded teardrop shaped thing and only a hard case will keep the buttons from getting accidentally depressed. I managed to find some of the very hard clear plastic bubble packaging that had close to a similar shape, but it was still much larger than the keyfob itself.

I have a good friend that's a soldering pro and who used to build custom devices for NASA that I could ask to do the soldering. He's tackled worse for me before, soldering tiny SMD devices and repairing tiny pushbuttons. I'd really like a solution other than a case. I tried that for a while. The biggest problem, other than the added bulk, is that a case requires two hands to operate, and might be very hard to do with gloves on. I already dropped the keys into deep snow fiddling with the case once this year. That's just one of the many reasons I don't like the case approach.

I think there's enough room if I find the right switch. I've taken some photos. The circuit board is very sparse, consisting of traces going to the switch, a single IC, and the power source.

Thanks for your input, Tony.

-- Bobby G.

Reply to
Robert Green

That's a good idea, and one I hadn't thought of. I've done the reverse on other things, supergluing a nylon washer collar around buttons that depress too easily. My favorite idiotic design was a Panasonic VCR remote that was designed so that you had to press two REC buttons that were side by side to engage the recording function. Unfortunately, the remote was designed with flowing curves and in such a way that when the remote was put down face down, the entire weight of the unit came down on the two REC buttons at the same time. More than one tape got ruined before I added a fail safe collar to the REC buttons.

Thanks for your input, Jim, it's exactly the kind of "brain storming" idea I was looking for.

-- Bobby G.

Reply to
Robert Green

Not an option. This is a handicapped van, and the keyfob in needed to activate the whole ramp deployment, kneeling and electric door activity.

Thanks anyway,

-- Bobby G.

Reply to
Robert Green

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