This was a project set forth by the need to feel safer about leaving my bike in parking lots. I know that anything that left in a parking lot is fair game for a thief, but there are alot of morons that think its ok to lean or sit on someone else's bike even though they don't even know the owner. This has already happened to me twice. So I decided to design an alarm for my bike.
I was thinking about using a tilt sensor for the handlebars, but I didn't have any workable mercury switches on hand. So I decided to use a magentic reed relay as the main part instead.
Next I had to design a schematic that would work. I wanted to use a master switch to turn it on, so it would beep if the bike was moved from the rest position.
First, I had to decide how I wanted the alarm to be activated and set off. I realized that when I park my bike, I always turn the tire to the left by habit for stability. So I decided to have it armed when I put the wheel left. So if someone got on my bike the springs would go down and trip the reed or if the tire moved right at all the reed would trip as well.
So heres the rough schematic I came up with:
Please make sure that the coil-relay in the upper-right hand side of the schematic is NC (normally Closed) for that is the whole key to the alarm.
Yes, I know, It looks like shit. I had a brainstorm and used Paint to draw it quickly. But I ran it through Psplice after that and it worked flawlessly. I will add a professional schematic when i find time.
I finally found time, but I didnt make it more professional, but it is easier to understand though.
So here are the parts I used:
Once the parts were located I installed them per schematic. The wiring is to hard to take a picture of so I will just show the installed parts, and you'll see some of the wiring anyway:
I don't have the picture of the Switch installation, because thats the key to the whole system, and if u know the location of it, you could turn it off in a heartbeat. Same goes for the magnet.
Yes, as you have already realized, this alarm is no where near full proof, as it has alot of security flaws.(If u want to talk about security and its flaws in a scocialogical persepctive talk to strick. But, what I am looking for in this alarm is tactical suprise, since they don't know that an alarm is in place since most bikes I know don't have alarms. And if it moves more than an inch the piezo sounds until it is replaced in the orginal position.
There was a 2 minor flaws in my original design. Which I wasn't suprised about to begin with since this was a first-generation prototype of the idea. Flaw number one was the fact that i used an incredibly diffucult glass reed-relay to try to make this alarm work. Just trying to get the the reed-relay into the proper position without it getting crushed led to it acutally getting crushed in a test.
Flaw number 2, was the type of relay I originally used was not so good because it had not been designed for a normally-open circuit. Which lead to the buzzer continually going off.
These two major flaws were fixed when I bought a more reliable reed-relay made for door and window security alarms from RadioCrap (You got answers, but we don't know how the hell to answer them). Next I found a $3.00 coil-relay from the same store and used that because it had pins on the relay for normally open and close.
After having a test drive with it fully installed, I have found no other problems. I consider this project complete.