Blog - Sketching with Hardware

How to build a smartphone camera trigger

Published on: | Author: Lea Gardner | Categories: 2018b, Tutorials

WHY?

Making sure that everything trivial is safely documented in form of a picture is nowadays a commonly practiced procedure. A quick morning selfie (your face might look different today?), a foodpic or a picture of your last holiday taken by means of your selfie-stick – all these routines need good and flexible access to your smartphone camera. For our Arduino Project “What’s the story morning glory?” we built a breakfast box which serves you your cereals and milk and takes a picture of your finely prepared breakfast (take a look at the blog entry from Elena Rudolph).

#selfie #fornoreasonatall

WHAT DO YOU NEED?

  • arduino
  • 5V relais module (arduino-compatible)
  • selfie stick circuit board
  • 4 pin headphone jack (TRRS)
  • jumper wires, soldering iron etc.

HOW DOES IT WORK?

  1. In this setup the arduino is the source of electricity and the digital pin is an OUTPUT pin.
  2. The relais is used to create a “button”, that can be triggered after a certain period of time without the interaction of the user.
    (it is safer than setting two connected pins HIGH after a certain period of time)
  3. The selfie stick circuit board, which you can find in any cheap selfie stick (without Bluetooth function), imitates the action of increasing or decreasing the volume of your audio, that is normally achieved by pressing the volume buttons on your smartphone. In camera mode this action triggers the shutter button of your smartphone. The circuit board functions as a resistor between 210-290 Ω for Vol+ or 360-680 Ω for Vol-.
  4. The microphone bit of the headphone jack triggers a picture once the circuit is closed (by “connecting” GND and mic) and the resistor (in this case the selfie stick circuit board) is in the correct resistance range (210-290 Ω or 360-680 Ω).
  5. Your smartphone has to be in camera mode to trigger a picture.

Notes:

  • We tried using regular resistors instead of the selfie stick circuit board, but it didn’t work for some reason. So, you are better off just using the selfie circuit board instead.
  • Once you cut the headphone jack you will have to try around a bit to figure out which of the cables are the GND and mic cables.

 

linked categories 2018b, Tutorials

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