Building a vehicle security system has been in mind for a while, however, a recent surge in motorcycle thefts from my university has forced me to pick up the pace with development. What this simple circuit does is once the bike's power is turned on from the ignition, a magnet must be waved over a hidden reed switch to activate a latching relay. This latched relay will continuously power the fuel pump until a) the ignition is turned off, b) the engine kill-switch is used, or c) a button on the handlebar is pressed that silently resets the circuit (without killing the engine). An LED is used to quickly identify whether power is going to the fuel pump, as it's not immediately obvious if you can't hear it pumping (ear plugs, loud ambiance).
This button (normally closed, press to open), which will release the relay, is mounted on the handlebar for emergency use. This would be used in a motorcycle-jacking situation. Instead of disabling the bike immediately, which could make for a tense situation if there's a weapon involved, the system silently turns the fuel pump off, leaving enough fuel in the carburetor bowls to drive ~1/8 mile. At that point the bike will stall and won't start until the fuel pump is energized by waving the magnet over the reed switch again.
Even if the circuit is known, the placement of the reed switch would not be apparent until body panels are taken off. The magnet can even be sewn into the sleeve of a jacket, so the hand placement over the reed switch or timing of its activation doesn't necessarily give away the position of the switch. The switch can also be reactivated after the bike is driven off, since the fuel in the carburetor bowls will still allow the bike to run a short distance. This can be crucial if you can predict a jacking, even if by a few seconds. If the reset button is pressed only to find it was unneeded, just a wave of the sleeve is needed to restore power to the fuel pump.
This circuit should also work with fuel injection, but would have to be activated before starting the bike. It must be mentioned that many fuel pumps allow fuel to flow when no power to the pump is supplied. This allows fuel to continually flow to the carb until the fuel in the tank(s) drops below the carb bowl level. In the case of carburetored bikes with a high-mounted tank(s), fuel pumps are unnecessary. For instance, the stock fuel pump of the KTM 950 Adventure does not inhibit fuel flow when the pump is not energized. To make this circuit work with this bike, the stock fuel pump must be replaced by a Facet 40171 solid state airplane pump. The design of this pump prevents fuel flow when power is not present. A solid state relay is something I'll choose use for its durability over this mechanical one shown below (blue box), as a SS relay has no moving parts and is less likely to fail.
On the subject of local bike thefts, the perps at my university are breaking the ignition by force and driving off. A friend of mine had his ignition broken recently, but his alarm system prevented the theft. Also, a few months ago, he was followed and almost bike-jacked while he was driving home from campus!
I personally use the steering lock, a disk lock, and occasionally a bike cover. I built this with the added benefit of preventing a jacking while driving, or about to drive. It would also be convenient if I were to want to get off my bike for a few minutes but didn't want to go through the trouble of putting my disk lock on.
The circuit itself would be easy to bypass if the side panels come off, which takes just a minute or so. This isn't something a thief is likely to do unless there was knowledge of the device. Even in that case, knowing the right wires to cross after that would also require intimate knowledge of the design. I'm betting if the bike stalls and won't start, the thief wouldn't bother to start removing panels to diagnose the electrical problem.
I ordered a solid state relay from mouser yesterday and will be testing the circuit under full load from the fuel pump early next week. I'm currently hunting for a waterproof button with handlebar mount.
The SS relay arrived today. This evening I dove into the wires and schematics of the KTM 950 electrical system. I found a few things about the fuel pump circuit I did not know that may cause a problem with my current prototype:
1: The ECU turns the fuel pump on and off.
2: The ECU controls the fuel pump through a relay.
Page 266 of the repair manual shows the wiring for this.
[Referencing the manual] I chose to have my SS relay switch the blue-grey wire between (1) on the ECU to (2) of the fuel pump relay. I used ACC2 (power switched with ignition) with the reed switch to trigger the SS relay (red and black wires on the corner of bread board next to - and +). I'm still on the search for a good SPST NC momentary push-button to reset the SS relay and a case for the circuitry.
The first prototype failed in tests today. After the key turn powers the bike, the ECU energizes the fuel pump for 3 seconds, then remains off until the bike has started and is running. The momentary power loss from the ECU between pre-start priming and when the bike and fuel pump are running caused the solid state relay to reset. This was fixed by adding a second relay to be latched by the first, instead of using the ignition power to latch the single relay. If one relay was used, the ignition power used to latch the relay would travel into the ECU, which I want to avoid to prevent possible damage.
*Prototype v2. The fuel pump relay to fuel pump part of the diagram is not drawn correctly (as you can see there is no battery drawn in the schematic)... but that's not the important part.
This afternoon I tested the second prototype on the breadboard, and it passed all tests. It was soldered onto perfboard and now awaits its live trial. Further coverage to ensue when I get a chance to test.
The first live test worked flawlessly, but it's too damn cold this December evening to do any more tinkering with bare hands behind the headlight. I should be able to make the circuit housing weatherproof and mount everything tomorrow. Maybe a driving test can be squeezed in, but that depends on the rate the epoxy cures.
It's sealed and mounted. For my own security I won't include pictures of where and how it's mounted, but it should be noted that to prevent corrosion, all wires were soldered, covered with heat-shrink tubing, and the case sealed with silicone or epoxy to weatherproof. Two test drives tonight lasted 0.25 miles and 0.4 miles until power was lost. The shorter distance was caused by 10 seconds at a red light. The 0.4 mi. test was in an uninhibited straight drive. Also keep in mind that this was from a hot-start, without the need for the engine to warm up. Many cold starts require at least 10 seconds until the bike is drivable. Currently, I'm very satisfied by the results.
As I said before, this is not my only theft deterrent. No single security device will prevent theft, but used in combination, they will increase the probability of thwarting a thief's attempts. This circuit design is mainly aimed at theft after other security devices have been removed, as in about to get on, or while riding. This is a high-risk time for theft because the bike's securities have [supposedly] been disabled. If no other way to lessen the danger presents itself, let the bike drive away and recover it shortly after.