Arduino project - detect someone touching trailer

Thread Starter

JeremyCondie

Joined Jan 5, 2015
13
Hi Guys
My trailer is my mobile man-cave - it holds my bicycles, motorbikes etc. I need to stop f**kers from stealing my toys. I don't want to set off an alarm *after* someone has broken in and damaged the doors etc. I'd like to be able to detect them as they touch the trailer *before* they try to enter. I'd obviously want to prevent false alarms.
I am thinking of an Arduino-controlled anti-theft system. But I am trying to decide on right sensors. Touching a metal surface must create an electrical field / small current drain / change in voltage. I can't seem to find something suitable.
Suggestions appreciated.
Thanks.
 

Yaakov

Joined Jan 27, 2019
3,492
Hi Guys
My trailer is my mobile man-cave - it holds my bicycles, motorbikes etc. I need to stop f**kers from stealing my toys. I don't want to set off an alarm *after* someone has broken in and damaged the doors etc. I'd like to be able to detect them as they touch the trailer *before* they try to enter. I'd obviously want to prevent false alarms.
I am thinking of an Arduino-controlled anti-theft system. But I am trying to decide on right sensors. Touching a metal surface must create an electrical field / small current drain / change in voltage. I can't seem to find something suitable.
Suggestions appreciated.
Thanks.
This Arduino compatible Teensy LC board has 11 capacitive touch sensor pins: https://www.pjrc.com/store/teensylc.html It seems like a running head start.

1616314450004.png
 

Alec_t

Joined Sep 17, 2013
12,201
Your trailer is probably earthed, albeit poorly, via its tyres, which these days often (always?) contain conductive particles to discharge static electricity. That could be a problem for a capacitive sensor? Worth trying though. An alternative would be a PIR sensor.
 

KeithWalker

Joined Jul 10, 2017
1,917
Your trailer is probably earthed, albeit poorly, via its tyres, which these days often (always?) contain conductive particles to discharge static electricity. That could be a problem for a capacitive sensor? Worth trying though. An alternative would be a PIR sensor.
A capacitative touch sensor would probably work, but only in dry weather. Go with the proximity detector solution.
 

MalcolmZA

Joined Feb 1, 2021
16
When you say trailer I automatically think of something you'd put the wife's excess luggage in when going on vacation.
But seeing what you store in there, its more of what we call a caravan.

You might try RCWL-0516 radar sensor modules. Their sensitivity can be adjusted by a single resistor.
If your trailer has windows they're able to see through and can detect metal doors moving.
I've detuned one and connected to a the alarm in the wife's car. It's working a treat.

Take a look here... https://create.arduino.cc/projecthub/remnis/coolest-motion-detection-sensor-ever-d2d688

Cheers
MalcolmZA
 

djsfantasi

Joined Apr 11, 2010
7,827
Six PIR sensors. Or four Ping ultrasonic sensors. I’d go for the ping sensors, maybe doubled up, one on each end of each plane.
 
I made a touch alarm for my garage, wooden door with metal handle.
Actually it's a burglar alarm that goes off if the door is (forced) opened or motion sensor inside triggers.
If it's armed and someone touches the handle, it chirps four times. Steady siren is if the alarm trips.

I used a capacitive sensor. I started with the cheapola TTP223 touch sensor boards and modded them to work with a metal handle. But the IC did not work good because it only auto-nulls stray capacitance on power up, and is very sensitive to power 5V changing the slightest bit. So the IC was not stable and would stop detecting touch if outdoor temperature changed.

Next I went with AT42QT1010 from Sparkfun and modded the board to work sensing a door handle.
The problem will be these don't work great if it rains and there is water/frost/dew on the door between something metal. Dog pee on the tires.
The sensors are super sensitive and would pick up anything touching an isolated pice of metal. A lot depends on what wood and aluminum the trailer is made of.

I like the guy that just ran a car ignition coil to the vehicle to zap thieves. But your trailer tongue rest likely earth grounds things.
 
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