Introduction: Addressing Indicator Neglect
For bikers and scooter riders, remembering to cancel flashing indicators can be challenging without an audible reminder. Constantly checking indicator lamps isn’t practical; focus should be on the road ahead. This circuit offers a solution by providing an audible reminder. What makes it smart is its delay mechanism; it doesn’t beep instantly when the flashers activate, but rather after a preset time, ensuring it triggers only when indicators have been active longer than usual.
Circuit Operation: Utilizing Flasher Relay
The circuit is powered through the flasher relay, a central component in this setup. When the indicators are engaged, a square wave voltage is directed to bridge rectifier D1-D4 through terminal T1 or T2, while the other terminal remains grounded through the inactive indicator lamp. The pulsed DC voltage is then stored and smoothed in capacitor C1. D5 serves the dual purpose of preventing the electrolytic from discharging during periods when the flasher voltage is off and providing a clean supply voltage for the 555 timer whenever indicators operate.
555 Timer Implementation: Generating Audible Alert
In this setup, timer IC1 functions as an oscillator, dictating the operation of a piezo sounder via transistor T1. Crucially, the output of the 555 timer is active Low, meaning that initially, the transistor is blocked, rendering the sounder silent. This configuration sets the stage for generating a timely, audible alert for riders, ensuring a safer and more focused riding experience.
Calculating Delay Time: Circuit Operation
The timer consistently charges and discharges capacitor C2 within a range of one-third to two-thirds of the operating voltage, creating a delay interval calculated as 0.7 x C2 x (R2 + R1 + P1) [s]. The preset feature allows users to adjust this delay, extending it up to approximately one second. Initially, the delay before the sounder activates is significantly longer due to the discharged electrolytic. Only after this delay does the output become active, providing a pulse duration of 0.7 x C2 x R2 (approximately 0.15 seconds) for the sounder to operate.
Triggering the Sounder: +12 V Activation
This activation occurs when +12 V is present at the collector of transistor T1, happening when the flasher relay is switched on and the indicator bulbs illuminate. The circuit is securely housed within a splash-proof enclosure, strategically placed on the machine to ensure safety. The audible sounder, if waterproof, can be positioned outside the enclosure. The control unit necessitates just two cable connections, making it a straightforward process to link at any convenient access point.