Motorcycle Safeguard with Touch Sensor
How to secure a motorcycle?
Security motorcycle is basically making a double switch in addition to the lock switch on the motorcycle. Motorcycle can be turned on only if both the original and additional switch are ON. Additional switch is usually placed on a hidden place. Usually under the seat.
Although this methode is very simple, but effective enough to make dissuade thieves steal your motorcycle. In general, the thief action is in quick time. So, if after he turned the key on by force using T key, but it does not make the motorcycle engine can be turned on, then he will choose to cancel his intention to steal the bike rather than figuring out the secret switch position. Too risky!
However, although effective, the method has drawbacks. First, every time we turn the motorcycle off, we must also turn off the secret switch. If we forgot to turn off the secret switch, then it means that security become dysfunctional. The second weakness is, that the thief is usually observed first the motorcycle to be stolen. So, when we’re open seat and turning the secret switch off, so the thief could pay attention to us and know the position of the switch is on.
To overcome these weaknesses, we can use a relay.
Relay is enabled using the C9013 NPN transistor Q1. Relay will be active only if Q1 ON. While the Q1 will be ON only if its base get enough current. Q1 base can only get the current through R1 and the C9012 PNP transistor Q2. So, Q1 will be ON only if Q2 is also ON. Q2 will be ON if the base get a lower voltage than the emitter approximately below -0.7 V. Base of Q2 is connected to the collector of Q1 through R2. And because Q1 is OFF, the collector will be pulled to the power supply voltage through the relay coil. Thus, the base of Q2 will have the same voltage with its emitter. Therefore, Q2 will also be OFF.
The arrangement of the diode D2 and R4 make base voltage of Q2 is drawn to the power supply voltage through a relay and R2 only, which is 1M. If you touch the sensor while the other parts of our body also touches ground, the base voltage of Q2 will be pulled down. Pull toward the supply voltage by R2 is too small compared to the pull down through the hands. This make the base of Q2 will be lower than its emitter. Thus, Q2 will be ON. If Q2 is ON, then Q1 will be ON. And if Q1 is ON, then the collector of Q1 will drop to about 0.3 V only. With the arrangement of D2 and R4, then the base of Q2 will be pulled strongly enough to the ground. Thus, although our hands are released from the sensor, Q2 will be retained to ON.
C1 is used to ensure that when the circuit first get current, the base voltage of Q2 will be equal to its emitter. Thus, Q2 will be guaranteed in the OFF state until the sensor is touched.
D1 is used to remove the voltage generated by the relay coil when the power supply is disconnected. It is useful to prevent damage to the transistors because the voltage.
How to perform the installation.
There are two types of motorcycle CDI, which is “AC CDI” and “DC CDI”.
In the motorcycle using AC CDI, usually the lock bike has 4 wires (see directly from the back of the lock). 2 wires are normally open switch, and two other wires are normally closed switch. Normally open switch is used to connect or disconnect the motorcycle’s electricity and the Accumulator. While normally closed switch is used to allow the CDI on or prevent it. If both the CDI control cable is connected, then the CDI may not be activated. Conversely, if the cable is disconnected, then the CDI can be activated.
To install the circuit relay on a motorcycle of this type, connect the + of the circuit to point B. Then put in parallel the normally closed part relay switch to the point C and D. Ground of the circuit is connected to the motorcycle chassis.
To find these points, do the following experiment:
First, turn the key in the OFF position. Use a voltmeter with the negative probe connected to the chassis. Then positive probe tested at the four point on the key. There is only one point which will have a voltage of 12V. Well, that point is point A. Then turn the key to the ON position and find another spot that also has a voltage of 12V. The point is point B. 2 Another point is the point C and D.
While on a motorcycle with a DC CDI, then the motorcycle’s lock only has 2 wires. So you need to do is find the point A only. And automatically another point is the point B. While the installation is by cutting the point B from electricity. From B, connect to the + of the circuit and the common of relay switch. Then from the normally open switch is connected to the motorcycle’s electricity. Do not forget, grounding of the circuit is connected to the motorcycle chassis.
The sensor can be positioned anywhere up to you. However, the sensor must be completely isolated from the chassis. For example, connect the sensor to one of the screws or the bolt on the motor body (the plastic) that screws are not touching the chassis.
Good luck, may your motorcycle protected from theft ❗
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