Key Finder/Bike Lock

[Gadgego]

Hi,

for a schoolassignment we have to make a fictive product and we've chosen an electronic bike lock.
It should work the same way as an electronic car lock, with a key where you can push a button to open your lock etc.

But now we have a giant problem with the batteries. None of us has a technical background so we don't have a clue
which batteries to use.
We figured out that if we use 6 AA batteries our lock works for 16 hours (I guess we did the calculation wrong)
so we're looking for a way that the batteries work longer.

So we started thinking of what electronic toy also has to receive constantly, and we thought of a keyfinder (a thing
makes noise if you whistle, so you can find your keys back).

So now is my question: does anyone know how such a keyfinder works (especially how the batteries work, when does it receive ...).

And if anyone knows a solution for our problem it's also welcome.

 

[dknguyen]

Use something that locks by default mechanically with a spring and only uses power to open it, then it should last a lot longer and the bike will stay safe if batteries die. Also...have a key for manual override in case the batteries do run out...(though I suppose you could just replace the batteries!)

 

[Super_voip]

The keyfinders work on PLL (phase locked loop), the problem for the bike lock is that the radio has to stay powered on, so make the tuned section with an AM detector(diode) to turn the power on via a FET(field effect transistor) then do the signal analysis.

 

[audioguru]

The remote door opener on cars is a sophisticated radio receiver that is continuously powered from the huge car battery.

A Keys finder is an low power Cmos audio amplifier. Its button battery cells last one week or two.
My daughter had one. It triggered whenever she talked and all the time the TV sound was on. I couldn't trigger it by whistling nor by screaming at it.

 

[OutToLunch]

maybe it didn't like getting yelled at...

 

[jpanhalt]

Why would you want a remote lock for a bicycle? Where I live, you need to pass a chain through each wheel and the frame. Even then, the seat or handle bars may get stolen. Many riders take the seat with them.

Now, if it is not going to be remote, then do as dknguyen suggests. Have the lock active when off. Then you simply turn the receiver on with something like a pushbutton switch and simultaneously or within a short period press the electronic switch to open the lock. John

 

[dknguyen]

Or an RFID thing that you could wave your wallet in front of.

 

[audioguru]

I went to a training course in New York. There was a bus from the hotel to the training center. In the morning there were a couple of cars broken down on the side of the highway.
In the afternoon the wheels and doors of the cars were gone.
I broad daylight and everybody can see. I couldn't believe it.

Here in Canada a car was stolen from a gas station. The owner left the keys in the ignition while he pumped in the gas. The stolen car almost hit me.

 

[kchriste]

As mentioned above, a standard U-lock would be silly because it would still be in the spokes when remotely unlocked. However, a popular lock used in Europe in the past, just acted like a brake on the rear wheel. It was basically a C type lock mounted on the frame above the rear wheel. Turning a key engaged a claw like device that locked wheel by passing the claw though the spokes. A thief could still pick up the bike and carry it away though. You could add an alarm function to make the carrying less pleasant.
To conserve battery power in a receiver you would put it to sleep and wake it up every 2 seconds for 0.1 second. If the receiver doesn't see a carrier within 100ms then it goes back to sleep for 2 seconds. You would make your preamble on the remote 2.5 seconds so the receiver can wake up, see the carrier, and decode the unlock sequence.

 

[HiTech]

Your bicycle is made of steel or aluminum tubing so use that as a housing for the rechargeable batteries. A group of C-cells should fit nicely. They can also power any front/rear lighting and be complemented with a wheel mounted generator for charging during daylight riding. Just make sure that you use a plastic sleeve between the batteries and the tubing for this "ficticious" project to prevent salts from corroding the batteries to the steel.