Fake Car Alarm Circuit – 555 tutorial
9 Comments
This is a very simple circuit to make using a 555 component and is recommended for the electronics beginner.
This page outlines how to make a simple theft detterant which may be just as effective. The idea is to have a flashing red led indicate that your car is protected. This device can protect your vehicle from potential thieves – it makes it look like your car has an armed alarm system installed, which causes thieves to pass by your car in search of an easier target.
The project can be broken down into three steps. Constructing the circuit, powering the circuit, and installation.
Constructing the Circuit
The circuit is build around a 555 IC.
| Nr. | Name | Description |
| 1 | Ground | Ground Reference (0V) |
| 2 | Trigger | OUT rises, and interval starts, when this input falls below 1/3 VCC |
| 3 | Output | This output is driven to +VCC or GND. |
| 4 | Reset | A timing interval may be interrupted by driving this input to GND. |
| 5 | Vcc | +5 to +15v |
| 6 | Discharge | Open collector output; may discharge a capacitor between intervals |
| 7 | Threshhold | The interval ends when the voltage at THR is greater than at CTRL. |
| 8 | Control Voltage | Control” access to the internal voltage divider (by default, 2/3 VCC). |
Circuit Schematics
Components
| Annotation | Value |
| C1 | 10uF |
| C2 | 0.1uF |
| D1 | LED |
| P1 | CONN_2 |
| R1 | 10k |
| R2 | 150k |
| R3 | 330 Ohm |
| U1 | LM555N |
The Printed Circuit Board
Questions and Additional Information
For questions, additional information, or discussions regarding the project, enter the Electronics Forum.
