About the article

Car Tilt Alarm

Protect your alloy wheels

Car Tilt Alarm
The car alarm described here detects changes in the tilt angle of the vehicle in which the alarm is installed. It is set off when the change in the angle exceeds a threshold (adjustable) for too long (5 seconds). Short of cutting the power to it, the only way to stop the alarm is to put the car back to its initial angle. The change in angle to which the alarm is sensitive can be adjusted from 0 to 25°.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Extra info / Update
Technical Specifications
- trigger angle: 0–25°
- operating time adjustable 0–165 s;
- two activation modes: intermittent @ 0.5 Hz or continuous
- built-in installation aid.
Component list
R1 = SIL array 8x 4.7kOhm
R2,R3,R4 = 1kOhm
R5 = 330Ohm
R6 = 4.7kOhm
R7 = 10kOhm
C1 = 470µF 25V axial electrolytic
C2 = 100µF 25V axial electrolytic
C3, C6 = 100nF
C4, C5 = 15pF ceramic
IC1 = PIC16F877-20/P, programmed
IC2 = 7805
IC3 = ULN2803A
IC4 = 4N25 or equivalent
D1 = 1N4001
D2–D9, D12–D15 = 1N4148
D10, D11 = LED, 3mm
X1 = 8MHz quartz crystal, low profile
JP1–JP4, JP5–JP8, JP9–JP12 : 8-way (2x4) DIL pinheader with jumpers
S1 = 4-way DIP switch block
RE1 = relay, 12V coil, miniature, 2RT
K1,K2,K5,K6 = 3-way SIL pinheader, lead pitch 2.54mm (0.1")
Support for on/off LED, colour and diameter to personal requirements
2-axis accelerometer module with ADXL322 (Lextronic France # ADXL322)
Fuse and in-line fuseholder for vehicles
Standoffs, screws, case, etc.
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