With a $40 pay-as-you-go cell phone, stun gun, and some basic electronic components, you can teach bike thieves a lesson and, hopefully, foster a small social change through individual action:)
Shameless self-promotion: I've got this and my other stuff for sale here
Updated: here's me demoing this at Dorkbot Austin last month. And yes, I shock myself:)
Here's the original video of me explaining details on building this:
Step 1: Ingredients
Part of what will make this secure is variance in the approaches we take. Feel free to start with a system similar to mine, but be sure to vary it up!
For a basic system that shocks and tracks, here's what you'll need:
-stun gun; I used the basic, ~50,000 volt one I found at a local sporting goods store. ~$20. You could also mod an instant camera or build one from scratch...
-Phone capable of talking to some tracking system. I went with mologogo, but feel free to play around with others. For the boost mobile motorola i425t, I paid ~$40. Unlimited internet service is like 35 cents a day. I haven't tried, but I've heard reports of being able to use mologogo without buying the net service...
-a diode to connect in paralel with the stun gun, because we're obviously concerned about safety...
-assorted thin-gauge interconnecting wires and non conductive electrical tapes
-circuit protobyping board
-a basic npn transistor, with datasheet. i used the 2n5088.
-a resistor sized based on your transistor. i used a 1.5-ohm one
To choose the right transistor and resistor, read this guide and look at these circuits. If you're using this same design as I did, the load you're trying to control is the 9v battery connection to the stun gun at 9volts 2.8 amps. If you go off the vibrating motor, you're controlling this via something like ~5volts .5 amps...
Useful tools were:
-screwdriver for the weird screws in the back of the cell phone. it was like ultra-tiny torx or something; your best bet is to get the phone, try your existing collection of weird screwdrivers, and get a specific new one if you need to
-multimeter (with ammeter)
-soldering iron, solder
-'helping hands' alligator clip + magnifying glass thing
Step 2: Install & Test Mologogo
Next, let's step away from our workbench and go for a walk. As part of this, we'll test our tracking setup.
I activated my pay-as-you-go phone (doesn't require a real address or any credit card, and came w/ $5 credit) and opted for the 35-cents-a-day unlimited web plan. Please immediately change your default ringtone from the obnoxious 'where you at' to anything slightly less ridiculous, for the sake of everyone's sanity. If you're running off the vibrator motor, you'll obviously want a ringtone including vibration...
Installing mologogo is pretty straightforward. The i425 is a newer phone without a full mologogo version as of this writing, but the i425 test version of the software (available on mologogo.com) worked fine for me. the only other real-cheap choice is the i415, which i didn't use because i couldn't find it in any local stores. the i415 seems more tested and slightly bulkier, but it may be a bit easier to tinker around inside:) also, you can use a camera's mini usb cable to install mologogo on the i425 but need a stupid proprietary cable for the i415.
Setup mologogo however you'd like. I've got mine refreshing ~every 15 seconds, turned off the 'revert to cell antenna location if no gps, and set retries to like 999. you can also set a calendar event on the phone to start mologogo every hour or whatever (to work around any issues w/ crashing), send location data to a different server, and all kind of other grooviness. I won't further belabor this point; mologogo's got a great wiki on it...
Obviously, you know mologogo's working when it is accurately displaying your path on your mologogo.com account from a computer...
Step 3: Connect Leads to Vibrator Motor
Connecting 2 wires to the 2 leads on the vibrator motor is waaaayyyyy more difficult than I anticipated. Try it yourself and then let me know whether this is more incompetence on my part or legitimate difficulty. But be forewarned: I broke one phone and spent over 6 hours trying to get this element just right.
Some things I did figure out:
-remove the back of the phone along with the battery and sim card. after you unscrew the 6 weird screws and pop out the cover to the usb port, the front of the phone will come off as well w/ a little force along the edges.
-the keypad assembly contains the vibrating motor and can be disconnected from the rest of the phone. if you're looking down at the keypad, force it upwards on the right side and it'll pop out a snap-on connector. flip up the ribbon cable connector on the other side and that'll pop off, too; my note on the picture below should make this a little more understandable.
-the ribbon cable that runs to the vibrating motor and speaker can also be disconnected. yeah, this took me forever to figure out:)
In the end, I used a flat ribbon cable from a dismantled cdrom drive just wedged and taped into place. When this broke, I switched to 2 wires from an ide cable and soldered the more accessible of the 2 while wedging in the other. We'll see how long this lasts:)
You know you've got this wired correctly when you get a brief reading for voltage / amperage on your multimeter when you make the phone vibrate and connect the multimeter leads to the 2 wires from the vibrator motor.
Step 4: Build Your Controlling Circuit
The photos below show how I put this all together; basically just a resistor, diode, and transistor holding it all together. Not too much to it!
If you use a speaker as input, you may need a resistor with more gain. You can create this via 2 transistors combined as a Darlington pair; see the resources I linked to on the 'instructions' page for more info.
Step 5: Customize Away!
For version 1, I'm putting everything in a water bottle case. I'm undecided on whether or not the water bottle pop-open lid will turn the assembly on and off:) Not nearly as subtle or miniature as we can get with this, but it's a start.
If you're delivering a shock, run wires from the stun gun leads to the handlebars, stripping the insulation at points such that they're not touching the metal of the bike frame but will touch the skin of the bike thief so that they'll be in contact with a positive and a negative charge. The best way I've thought of to do this is to run the wires to the handlebars and wind both wires around both grips. I'd guesstimate you should use at least 22gauge and then anticipate them melting if used frequently.
Some suggestions for expansion:
-Vibrate only for a call / text message from a specific number
-Use on cars / motorcycles / scooters with an ignition kill as the payload(!)
-Add an accelerometer to control power to the cell phone
-Turn on auto-answer with DTMF to control multiple actions. Here's one such controller.
-Add a solenoid to trigger the brakes:)
Basically, go to town! And, if you're biking to town, be sure to disable your wacky security system.
Ohyeah, and this is remotely triggered onto anyone who comments telling me to put a shirt on in the video:)
Second Prize in the
Park Tool Bike Month