LED anti-theft alarm circuit for protecting motorcycle

Sometimes, the simulation of anti-theft devices, such as the real alarm system can be used to make the thief attempt to eliminate theft. To this end, the circuit in the figure so that the installation of the motorcycle taillight on the two super bright LED flashing automatically, used to simulate the commonly used to indicate an effective alarm warning. When the motorcycle is on the parking bracket, the mercury switch activates the circuit.

The core of the circuit is a linear regulator with an internal reset and watchdog circuit (MAX5023MASA). The judgment of "watchdog reset (Reset) pin to LED flash, the gate pin used to drive a P channel MOSFET, with P channel device logic level gate threshold and 50mA continuous current ratings are. The example of the circuit using A Morimi semiconductor (ON Semiconductor) MTD20P03HDL.

The red LED (Lumiled HPWT-DD00) is designed for automotive applications, the flash needs about 40mA current, but the circuit driver LED turn-on time is 200ms, the cycle is about 1.6s. This duty cycle of about 1/8 to minimize the leakage of the battery.

It is clear that when the motorcycle is upright, the circuit should not be energized, and on the parking bracket, the circuit should be through the mercury switch. It is hard to find a suitable mounting plate and adjust the angle of the switch with the motorcycle. The electrical performance of the mercury switch is not critical, but the switch designed for automotive applications is more robust and easier to adjust.

Source: electronic systems design / Author: Kevin Bilke, field application engineer, American letter integration products