Reverse alarm is nothing new. Almost all commercial vehicles (trucks, buses, etc.) and industrial vehicles (forklifts, wheeled construction vehicles, etc.) have one installed. The loudness of reverse alarms varies from model to model, but the "beep frequency" is quite uniform. Most beeps at 1.5Hz. In other words, they make approximately 90 beeps per minute.
These alarms are commercially available. The reason I am building one is (1) to save money, as I already have the required parts to create one; and (2) to learn, as I have never utilized the infamous 555 timer IC.
The parts I utilized in this project are:
The 555 timer IC is made by ST Microelectronics (NE555N). Package is the 8-pin DIP, easy to work with.
The noise-maker is a piezo-electric beeper. Not sure who made it. It takes 3-15V DC, and makes continuous LOUD (I guess at least 70 dB at 30cm) beep.
According to the 555 timer IC datasheet, two sets of resistors (R1 and R2) and capacitors (C1) are required to set the timer. In my case of 1.5Hz astable (continuous) operation, R1 is chosen to be 2000 ohm, R2 4000 ohm, and C1 100 uF. I found a lot of 1000 ohm resistors so I used them in series instead of picking two discrete resistors. The capacitor is from Rubycon, real good stuff.
To save resource and time, I utilize good ol' P2P (point to point, not peer to peer) construction. Yeah it looks ugly, but it will be engulfed in hot glue inside a plastic cap, so I don't care.
The plastic cap is a cleaned child-safe bottle cap from a Listerine antiseptic mouthwash bottle. Here is the finished product with gallons of hot glue:
Overall, this is a real easy project. All I need now is to hook this up to the reverse light on my vehicle and find a place to secure it somehow...
