Open a door using a cell phone app

Introduction

This project allows you to open a door using an app on a smartphone. The app is based upon the “DO button” app from IFTTT and is available on both iOS and Android smartphones.

The door is opened electronically using an electric door strike. An electric door strike replaces the standard door strike with a device that has a solenoid controlling the back of the strike. When the solenoid is activated, the door may be pushed open even when the door bolt is extended and locked. The door strike should be a “fail safe” model; this means that the back of the electric door strike is always locked in place when there is no power to the solenoid. The back of the door strike can only be pushed open when the solenoid is activated. Use of an electric door strike means that no modifications need be made to the standard door knob and lock mechanism. These continue to work as usual and the door can always be unlocked and opened with the standard key.

NOTE: Installation of an electric door strike involves significant modification to the door frame. Please do not attempt this project unless you have the necessary tools and skills to do this. A sample video about installation of a similar door strike in a wooden door frame can be viewed at: https://www.youtube.com/watch?v=dImYdCY89CM.

The “DO button” app on your smartphone allows you to open the door from anywhere in the world, as long as you have Internet access. You can let yourself into your house via this project and you can let family and friends into your locked house when you are away. Activation of the “DO button” on your smartphone unlocks the door strike for two seconds, allowing anyone standing at the door to enter by simply pushing on the door. An LED lights when the door strike is activated to cue the person at the door that the door strike is unlatched. You can easily change this two second activation time to any time period that you want via the IFTTT “DO” app recipe that you create in your private IFTTT account.

Overview

The figure below contains an overview of the system concept for this project. Internet capability is supplied by a “Photon” (or Core) module from Particle.io. The Photon requires a WiFi connection to the Internet. The software supplied with this project is loaded onto the Photon module (via WiFi). This software activates a relay which, in turn, activates the electric door strike for a period of time that is specified in the IFTTT “DO” recipe that you create.

The Photon is plugged into a “Relay Shield”, also from Particle.io. The Relay Shield accepts 12 volt DC power (which is also used by the door strike) and connects the Photon to 4 relays. Only one relay (#1) is used for this project. You can use the other three relays in any manner that you wish by writing functions similar to the one supplied with this project. Refer to the Particle.io on-line documentation for further information.

Note that it takes about 5 seconds from DO button activation on a smartphone until the door strike actually unlocks. This is a delay through the IFTTT cloud service. A custom app that communicates directly with the Particle Cloud service could avoid this delay, but is not part of this project. An LED is included in this project so that a person standing by the door knows when the door strike is unlatched.

This project requires you to have an account with Particle.io and with IFTTT.com. Both services are free and all Internet communication is secure.

Complete instructions for this project can be found at:

https://github.com/BobGlicksman/Particle-Door-Open