Fail-safe for keyless entry

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of
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.
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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

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<stuff snipped>

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.
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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.
--
Mike Barnes

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pushed
do
Mike, you must have nerves of steel and one hell of an even-flowing glue gun to be able to sculpt glue like that. It would be beyond me. Besides, this is a 7 button (IIRC) remote with four of the keys arranged like pie wedges with very thin separators.
The glue method is a good technique to know, and I've used a similar one elsewhere (superglue and washers and O-rings) but I don't think it will work on this fob.
Thanks for the suggestion, though, Mike.
-- Bobby G.
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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.
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.
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pushed
do
the
it
but
clear
keychain
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I had been told in safety meetings these "flight recorders" were coming for our company vans....WHoa!!! Union strike...LOL
Gives a whole new meaning to a SSD (solid state HDD). You can get about 60GB for $135 now. Endless loop and keeps the last 15 minutes or so. May go a long way.
Actually. I take that back about the penknife case. After reading your rant about the hands full of crap, I empathise with that and a case would be one more piece of crap in your hands when you are trying to get out of the vehicle.
Solution? Don't carry it or black electrical tape over the buttons to make them hard to push. Replace when gooey.
I like the "O" ring under the button, depending on design.
The worst incident was deploying the fold out ramp by accident, turning to try to stop it from hitting the car next to me and leaning on the van's horn button and then grabbing the keys hard enough to hit the panic button. I felt like everyone within 1000 feet was watching me. Yet the other day, when someone cut in front of me, I couldn't find the right area of the steering wheel cover to press to warn them. There's something wrong with a design that goes off when you don't want it to, but doesn't go off when you do.

The dash cam I got from Ebay for about $80 was useful, but you really need to have a record of what's happening on all four sides of you if you're in an accident. A windshield cam won't capture the image of someone T-boning you while they're running a red light but a side-view cam will. Put it together from COTS parts for under $200. Starts up with the car, goes into automatic record (with one channel of audio, too) and goes off with the car.
I am going to mod it so that I can also monitor the car when it's sitting parked to see who's looking inside to see what's what. Thieves usually "case the joint" first. The DVR is a small box that fits easily under the rear seat. Cabling and mounting the cams to be unobtrusive was a problem and still needs refinement. Right now it runs off the van battery, but I want to mount a separate 12VDC marine battery to power the rig independently of the van's power supply.
I got the idea from an episode of "COPS" where they rig up a car with all sorts of cameras and remote functions. The leave the "bait" car in places where people are likely to steal them. Apparently, that turns out to be everywhere. With the Toyota debacle unfolding, having a "flight recorder" in the car doesn't seem as far-fetched as it used to. With people texting while they're driving, a visual record might come in very handy if a serious accident occurs. And if I am at fault, a CF card goes missing. (-:
If I power it from a marine battery, I can also add a 2.4gHz transmitter and watch what happens out of sight with my trusty Taser (they're having a big sale on the pro-sumer model).
-- Bobby G.
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for
It makes economic sense given the liabilities. In tough economic times, there is in increase in people that insurers call "jumpers." They look for a company van or an expensive car at an intersections and for drivers fussing with cell phones and not paying attention. Then they "jump" out in front of a vehicle hoping to get hurt just enough to make an insurance claim.

60GB
You really don't need anything more than the last minute of a recording to deal with car accidents. They happen pretty quickly. A 16GB card is overkill, really, but it allows for faster FPS's and higher resolution, and that's a good thing to have. The CF card format means after an accident, I can just pop out the card easily. Don't know about you, but I've had stuff disappear from cars that have been towed to wrecking yards.
My major concern is that testing to make sure the data is actually written and is readable after a crash could be very expensive. (-:

rant
one
Agreed, it's not the ideal solution, but it may be a decent work-around until I can explore some of the options that people have contributed here.

Tried that, actually. Two weeks of gooey tape riding around in a typical pants pocket looks like a furry little mouse. It really just needs a harder plastic "skin" around it that makes the buttons a little harder to press than they are now. I was kinda of hoping someone would post something telling me "that's the fobshield 101, and you can get it at so and so's."

That whole concept has a lot going for it. No soldering, for one. The problem is that there are seven buttons on the remote. A spacer between the two halves of the fob may be the best bet.
-- Bobby G.
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A fob sleeve holder in the vehicle may work for the sleeve.
You push the fob and condom into a hlder, pull out the fob and use it. When complete, you push the fob into the holder, grab both and remove them for your pockets. Trouble is you want the buttons usable outside the vehicle and the flow logic isn't there.
I am still not convinced, on my Camry that I have actually pushed the buttons. When hearing lock clicks, a few times, I have looked down and fingers could not even reach the buttons in my hand??? However, if the buttons were transmitting intermittently, one would think a dead battery would happen in a few months / years. Mine is 9 years old (some like it hot...)
My work van unit had a long range ( a 100 meters or so) and the panic alarm was doing it's thing a few times, while I was in a public building, just being in my pocket. GMC van. Got embarrassing, a few times, wondering who the idiot is and finding out it's you...LOL ASt least the Camry is 30-40 feet to the front and about 10 feet to the rear of car. Doesn't help find the car when you parked at the same mall a few times and can't remember what day it is.
Agreed, it's not the ideal solution, but it may be a decent work-around until I can explore some of the options that people have contributed here.

rant
one
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groupe de discussion : hql728$emd$ snipped-for-privacy@speranza.aioe.org...

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Did you try the Heat-shrink tubing approch?
http://en.wikipedia.org/wiki/Heat-shrink_tubing
Just use some large heat shrink tube on your keyfob then shrink it to fit..
when it will be worn out replace and your on the road again!
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<stuff snipped>

fit..
No, I hadn't thought of that, but it could be the winning suggestion. I'd have to copy the markings on the buttons with a silver tipped pen, but I think I have some heat shrink large enough to at least make a trial run.
Thanks for your input! I'm off to try it right now. . . .
Just tried it with one layer of heat shrink, and that helps. I think there's room enough for a second layer, and that should do the trick!
Good call. This is why I always take my intractable problems to Usenet for the "group mind" approach. Thanks to all who contributed to the process, as there were some very good "also rans" in this thread.
The heat shrink method is not invasive, doesn't require good hand/eye coordination and looks like it will do the trick, making the buttons just a little harder to depress by accident. Considering how much I use heat shrink tubing for everything around the house, I am surprised I didn't think of it. I use the large diameter stuff to put on broom handles, canes and other things where I need to have a good grip (and not get splinters!). Turns out to be the right size for the fob, too. Best thing is that it won't come undone accidentally like my O-ring/washer solutions do after a while. Now to try to draw little pictograms on the buttons to indicate what they do.
Thanks again, Pete, and to everyone who responded. Good work!
-- Bobby G.
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Perhaps well placed holes with a paper hole punch may may the button pressing more available??
Heat shrink can become brittle after a while with the heat exposure and maybe UV?? Slit and replace every year or so?
Nice
<stuff snipped>

fit..
No, I hadn't thought of that, but it could be the winning suggestion. I'd have to copy the markings on the buttons with a silver tipped pen, but I think I have some heat shrink large enough to at least make a trial run.
Thanks for your input! I'm off to try it right now. . . .
Just tried it with one layer of heat shrink, and that helps. I think there's room enough for a second layer, and that should do the trick!
Good call. This is why I always take my intractable problems to Usenet for the "group mind" approach. Thanks to all who contributed to the process, as there were some very good "also rans" in this thread.
The heat shrink method is not invasive, doesn't require good hand/eye coordination and looks like it will do the trick, making the buttons just a little harder to depress by accident. Considering how much I use heat shrink tubing for everything around the house, I am surprised I didn't think of it. I use the large diameter stuff to put on broom handles, canes and other things where I need to have a good grip (and not get splinters!). Turns out to be the right size for the fob, too. Best thing is that it won't come undone accidentally like my O-ring/washer solutions do after a while. Now to try to draw little pictograms on the buttons to indicate what they do.
Thanks again, Pete, and to everyone who responded. Good work!
-- Bobby G.
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I have enough tubing to do a fleet of fobs, so when it starts to go, I'll just slit and replace, as you suggest. The only problem I see now is that the silver pen writing on the heat shrink will wear off very quickly. I am going to see if I can find white shrink tubing in the 1.5" size so I can write on it with an indelible Sharpie.
It turns out that a second layer of heat-shrink tubing did the trick. I tried to accidentally activate the unit and it only responds to direct pressure now. Sweet!
Now, if only I had thought of replacing the battery before I put the shrink tubing on. D'oh!
Now I won't have the neighbors asking why I left the doors open and the ramp down all night. Ironically, when I leave it parked in the driveway, it's impossible to see from the window or the CCTV cams whether the door is wide open. It's on the opposite side and the rear windows are tinted. Three cheers for Usenet and for Pete who came up with the heat shrink tubing. Honorable mention goes to Josephi for the tape solution which had the same idea using electrical tape, only slightly messier. (-:
-- Bobby G.
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Why not use transparent heat shrink?

--
Tom Stiller

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and
I'll
that
am
'Cuz I didn't think of it!
!!!
D'oh times two.
Thanks,
-- Bobby G.
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"Robert Green" wrote:

Robert,
I've used SAharpie fine point laundry markers on wire for years. It will last forever once it's dry. I actually prefer it to Dymo labels.
I did not realize you use a chair. So far I've only got a cane. I've been offered a power chair but I don't want it. Trying to get by with as few machines as I can. :^(
Regards, Robert
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groupe de discussion : hqpurh$e6k$ snipped-for-privacy@speranza.aioe.org...

Your welcome Bob...
Sometime a french man from Quebec can be usefull!! LOL
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wrote:

My fob needs to be reprogrammed every time the battery is changed. I would imagine yours is similar.
Disconnecting the battery would have the same effect. It would get very annoying to have to reprogram the fob every time I wanted to get into the car.
Try wearing pants that aren't so tight when you keep the keys in your pocket.
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wrote:

the
it
<<My fob needs to be reprogrammed every time the battery is changed. I would imagine yours is similar.>>
I inadvertently did the experiment that Ian first suggested because when the fob is popped open, the battery goes with one half, the circuit board with the other. After being disconnected for several hours, it still locked the car (I looked out the window to see the lights flash). This is a TRW remote for a 2002 Chrysler Grand Caravan.
<<Disconnecting the battery would have the same effect. It would get very annoying to have to reprogram the fob every time I wanted to get into the car.>>
Yes, that would be a deal-breaker. That's why I suggested to Ian that I would look for a way to insert a second switch into the circuit that did not affect the trickle current going to the IC. That should be pretty easy since it's an open circuit anyway. Adding a second switch would just mean that both had to be pressed simultaneously.
Thanks for the caveat, but as far as I can tell, my unit doesn't have a sophisticated fob. Perhaps that's because the keys have RF immobolizers built into them and the security is "concentrated" at that point.
<Try wearing pants that aren't so tight when you keep the keys in your pocket.>
It's not only pants, it's holding them in your hand with all the other things your hands do upon exiting a vehicle or even throwing them in a purse. The damn buttons are just not "stiff" enough to resist erroneous activation. Bad design. From a carmaker. Who would have ever expected it? (-:
-- Bobby G.
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