Instructables
Picture of Festival Tent Finder

Finding your tent in a large festival or campsite can often be pretty tricky! Miles upon miles of similar looking tents, dark paths between them and as often as not (for me at least) a beer inside you to fuddle your tent finding prowess.

Enter the festival tent finder! This super simple circuit, when strapped to a mobile phone, detects the illumination from a mobile phone backlight and turns on a small battery powered relay. This relay can be used to turn on a set of battery powered LED lights fastened to your tent.

All you need do to find your tent, is phone it! When the phone in your tent rings, the lights will turn on. Easy!

This project is a collaboration* between Kiteman and myself.

(*Kiteman adds: I had the basic idea ("Wouldn't it be cool if you could phone your tent to find it?"), but Jayefuu did the actual work designing and building the circuit. I had something much less elegant, and more expensive, in mind.)

 
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Step 1: Circuit Design

Picture of Circuit Design

Functionality:

The objective is to design a circuit that can be easily triggered from the backlight of a cheap, old mobile phone. As you ring the mobile, the screen backlight will turn on and our simple circuit will trigger a relay. This relay can easily be attached to some battery powered LED lights or a lantern on the outside of your tent, allowing you to easily see your tent.

Components:

  • 1 x breadboard
  • 1 x TEPT4400 phototransistor
  • 1 x 2N2222 NPN transistor
  • 1 x 1N40001 diode
  • 1 x SPDT (single pole, dual throw) 9V relay
  • 1 x 100 Ohm resistor

This is brilliant! I'm going to have to make one of these for Burning Man!

Post pictures when you do!

meikdre3 months ago

love to see things done different but why not intercepting the vibration of the mobile?

Kiteman meikdre3 months ago

That was my original idea, but it would have involved physically hacking into the phone to remove the vibration motor and use the current from that to trigger the relay in the version Jayefuu designed, which would have made the phone useless for anything except the tent finder.

Jayefuu's design turned out to be simpler, cheaper, and more elegant.

Jayefuu (author)  meikdre3 months ago

The electronics would be more complicated and would use more power. It's totally possible, but this seemed simpler.

mefromliny3 months ago
Nicely done!
ItalianJack3 months ago
This is a phenomenal idea! Great job! I will definitely try it sometime.
kbc23 months ago
dig the idea! how about another spin on it? like taking a receiver from a car for the door lock remote to turn on the lights so all you have to do is carry a key fob. some times you're not where you have cell signal. and you can leave the panic horn attached, ( EVIL LAUGH).
Kiteman3 months ago

I'm rather pleased this worked...