How to Make a Simple Motorcycle Security Alarm with Tilt Sensor

Here in this article, we are talking about one simple basic kind of motorcycle anti-theft alarm circuit. We are using one tilt switch and one TTP223 touch switch in it, right?

Now this idea actually came from Mr. Carl. He asked us to make this circuit for him. So now we see what he wanted.

What Mr. Carl Asked and What He Needed

He is a biker, right? And he wanted us to make one cheap and super simple alarm system for his bike. Maybe using a tilt sensor, he said. And then maybe turning it ON and OFF using a TTP223 touch pad, like that.

How the Circuit Works

So first, we have the tilt switch. When the bike is parked and standing tilted on its side stand then this switch stays in the ON position, right? But at this time the circuit is not running because the owner still has to turn it ON. For that, he secretly presses the hidden TTP223 touch switch. That powers the circuit.

Now what happens if a thief tries to steal the bike? If he lifts it off the stand then the bike becomes straight, and then that makes the mercury inside the tilt switch move.

Because of this, the tilt switch suddenly turns OFF, and then at the same time, it triggers the IC 555, which is set in monostable mode. This then activates a loud siren right away.

Now the siren starts blasting! So, people around will hear it, and then the owner will know that somebody is trying to steal his bike.

Ok, now here we explain the whole circuit, so we understand how this motorcycle anti-theft alarm works, right? We have a tilt switch, we have a TTP223 module, and now we go step by step to see how all this functions together.

How We Set Up and How This Works

First we take the TTP223 and set it up as a touch ON/OFF switch.

Now when the bike is parked and standing on its side stand then the owner taps on the back side of the TTP223 module. Then that turns it ON.

When it turns ON then the OUT pin of the TTP223 gives a positive voltage to the base of T2, and then T2 gets energized.

When T2 gets activated, then it also activates T3 and then that powers up the IC 555 circuit.

Now this IC 555 is working as a monostable multivibrator, right? So in this setup when pin#2 of IC 555 goes to ground then pin#3 of the IC gives a short high pulse.

How long this high pulse stays depends on the values of R2 and C1.

This high pulse is the one that turns ON T1, and then the siren starts blasting.

Now as we already said, pin#3 of the IC555 gives this high pulse only when pin#2 is connected to ground.

If we see the diagram, then we notice that the mercury tilt switch SW-520D is connected between pin#2 and the ground.

So, when the motorcycle is parked and tilted, then the mercury inside the tilt switch moves to one side. Then that keeps the internal contacts of the switch disconnected, so pin#2 of the IC 555 does not touch the ground.

Now imagine that some thief comes and tries to steal the bike. If he lifts the bike upright, then what happens? Then the mercury inside the tilt switch moves to the other side and then it shorts the internal contacts.

When this happens, then pin#2 of the IC555 immediately gets connected to the ground. Then that makes pin#3 go high, and then T1 and the alarm siren get triggered.

Now the thief may panic and try to put the bike back where it was, but that will not stop the alarm.

The alarm will stay ON for some time because the timing is set by R2 and C1.

By the time the alarm stops, then the owner already knows what is happening, so he can quickly take action.

Parts List

How to Build It Step by Step (Super Crude English)

Ok so now we are going to build this circuit, right? We have all parts ready and now we just connect everything step by step.

1. Fix the IC 555 on Board – First take one small PCB or a breadboard and place the IC 555 properly. Make sure pin#1 goes to ground and pin#8 goes to +12V.
2. Connect the Resistors and Capacitor – Now take all resistors and connect them exactly like in the circuit diagram. The capacitor C1 should be placed near the IC.
3. Fix the Transistors – Put the TIP122, TIP127 and BC547 in their correct places. See their pins carefully—collector, emitter, and base must go to the right points.
4. Add the TTP223 Module – Now fix the touch switch module on the board. Remember we need to short the "B" pads on the module as shown in the diagram.
5. Connect the Tilt Switch – This is very important. Mount the SW-520D tilt switch in the correct position. It should be placed in such a way that when the bike is tilted then the contacts stay open, and when the bike is straight, then the contacts close.
6. Solder the Zener Diode – The 5V Zener diode must be placed correctly. The cathode (striped end) goes to the correct transistor connection.
7. Wire Up the Siren – Take the siren and connect it to the transistor output as per the circuit. One wire goes to the collector of TIP122, and the other goes to +12V.
8. Do the Final Wiring – Now connect all ground wires together and then all +12V lines together. Check all connections properly.
9. Test It Before Fixing on Bike – Before fixing it permanently power the circuit and test. When you touch the TTP223, the system should activate. Then if you tilt the switch, then the alarm should trigger.
10. Install on Motorcycle – Once the testing is done then install the circuit inside the bike body in a hidden place. The tilt switch should be placed correctly so that it works properly when the bike is tilted and straightened.

That is all. Now the bike is protected. If a thief tries to take it then the alarm will make a loud noise and scare him away!