Introduction: Pressly:DIY Almighty Smartphone Button

About: I'm an Electronics Engineer who likes to make Doze Lamps, Lumen Powered Thingamajigs, Almighty Brainy Buttons, Tweeting Weather Stations and share them on Instructables.

Most physical keys have been chased off phones, thanks to the rampant rise of touch-screen technology, but here’s a DIY project that wants to bring a smarter kind of physical key to your smartphone. Pressly is a hardware button connected to a 3.5mm male audio jack that plugs into the headphone jack of your Smartphone or Tablet. It is compatible with both Android and iOS(Jailbreak required) platforms. So, for instance, if you always wanted a shortcut to snap a photo and upload it straight to a social network you could create that function in the app which link to Pressly. Of course there are apps that can do this sort of thing, but the point about Pressly is that it’s a chunk of hardware that sits within easy reach of your fingers — thereby cutting down on the number of actions required to perform the function you’re after. Pressly is compatible with a number of apps listed further in the Instructable.

The apps compatible with Pressly will allow a range of shortcuts to be created, based on a combination of short and long presses of the Pressly key. Which all sounds great, so long as you don’t get your shortcuts mixed up — and end up turning on your flashlight instead of taking a sneaky photo, say. Or sending an SMS to your mum saying ‘I’m on my way’, instead of toggling on your Wi-Fi.

The Pressly-compatible- apps will also allow for app settings to be customised too, so in addition to a basic photo snapping shortcut you could set up a specifically sneaky photo shortcut that keeps the phone’s screen and flash off and kills the shutter noise. If you wanted to be really, really creepy. Pressly also doubles up as a FM Radio antenna for your smartphone.

Pressly is the Smartphone Button that #rethinkphone

This Instructable was inspired by Eyd84's Instructable: How To Make A 3.5mm Audio Switch and I remixed it inorder to make a Smartphone Smart Button.

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One of the main uses of a laser cutter would be to laser cut enclosures for Pressly and many of my other Instructables too like TWIST, Component Tester. A laser cutter could have really helped with the construction of my Solar+Wind house. In the Instructables mentioned I also included the laser cutting files, which shows my familiarity with this technology. I could also use the Laser engraving feature to etch all my PCB's, it would be faster than the conventional chemical process.

Step 1: How Does Pressly Work?

Pressly relies on the inbuilt MIC button/call answering function of the smartphones audio connector. Pressly combines a male 3.5mm Audio jack and a simple push button. The terminals of the push button are connected between the Ground and MIC terminals of the 3.5mm audio jack. When the button is pressed, the Ground and MIC terminals are shorted and the signal generated is detected by the smartphone. An app compatible with Pressly is used to identify the signal/button press and perform a certain function assigned by the user.

Time Taken to make a Pressly: 1 Hour

Cost per Pressly: Less than $5

Step 2: Components & Tools Required

Electronic Components:


Step 3: 3.5mm Audio Jack

The Universal 4-pole Smartphone Headset 3.5mm male Audio jack has 4 different terminals. The terminal closest to the base of the jack is the 'MIC' or 'Microphone & Control' terminal also known as the 'Sleeve'. The terminal right after the Sleeve is the Ground(GND) terminal also known as the 2nd Ring. The remaining two terminals are the left and right channels for the audio headset.

Most smartphones and tablets manufactured by various OEM's follow this pinout for their audio jack integration in their smartphones.

Ensure that the 3.5mm male audio jack has a total of 4 Rings. Other connectors may have 3 Rings, but for this project it is mandatory that we have a 4 Ring audio jack.

Step 4: Testing the Audio Jack

In-order to ensure that you successfully build a Pressly it is necessary to check the components that you use before assembling or soldering them together.

  1. Start by identifying the ring closest to the base of the audio jack and the longest terminal. They should be the MIC terminal and ring and should be internally connected.
  2. Test the connection for the MIC terminal by setting the Multimeter to the 'continuity' mode and connecting one of the probes to the MIC ring and the other probe to the MIC terminal. If the multimeter emits a 'BEEP' sound, the MIC is internally connected.
  3. Next identify the Second ring from the base of the audio jack and the second longest terminal. They should be the Ground(GND) terminal and ring and should be internally connected.
  4. Test the connection for the GND terminal by setting the Multimeter on the 'continuity' mode and connecting one of the probes to the GND ring and the other probe to the GND terminal. If the Multimeter emits a "BEEP' sound, the GND is internally connected.
  5. The remaining two terminals are the Left and Right channels and do not have to be checked since they are not used.
  6. Also check that none of the 4 terminals are shorted. Example: GND & left channel. Do this by following the same method used to check the continuity of the ring and terminals.

Step 5: Push Button/ Momentary Switch

The push button or momentary switch acts like a normal switch. The only difference is that it is Normally-Open and hence need to be pressed for current to flow through it. If the push button is released no current flows through it.

The moment the push button is pressed the 'MIC' and 'GND' terminals are shorted and a signal is detected by the app on the smartphone.

Step 6: Cutting Off Extra Terminals

The 3.5mm audio jack has 4 terminals. The two- Left & Right Channel terminals are unnecessary since they are not being used in this project. Instead of leaving them open, we must cut them from the audio jack using a wire cutter so that they do not cause any problems later. Problems such as shorting will be avoided by cutting off these terminals.

Most momentary switches consist of 4 terminals. In this project we will be using only two of them making the other two redundant. After checking the two terminals that you wish to use using a multimeter, cut off the extra two terminals using a wire cutter or plier.

IMPORTANT: Use a Multimeter to check the continuity between the terminals of the Switch and audio jack before cutting.

Step 7: Circuit

Once you have cut off all the extra terminals from the audio jack and momentary switch, it is time to review the circuit diagram.

The connections are as follows:

  1. One terminal of the push button/ momentary switch is connected to the Ground(GND) terminal of the audio jack.
  2. The other terminal of the push button/ momentary switch is connected to the MIC(Sleeve) terminal of the audio jack.

Below is the file containing the circuit diagram, breadboard view and also PCB view. You can make changes to this circuit if you wish to by downloading and editing the file. The file has been created on the Fritzing circuit design software.

NOTE: The audio jack in the breadboard view is a 'Female 3.5mm Audio jack' as the 'Male 3.5mm Audio jack' cannot be connected to a breadboard.

Step 8: Soldering

  1. Start by placing the switch so that its terminals fit into the holes of the terminals of the audio jack.
  2. Solder the terminals of the audio jack and the push button.
  3. Ensure that the button works after soldering using a continuity test on your multimeter.

Step 9: Installing & Configuring the App

Pressly is compatible with a variety of apps from various developers on both Android and iPhone platforms. I have gone through various apps and tested them out thoroughly and my favourite was KeyCut for Android & for iOS you would require to Jailbreak your device and then install an app known as 'Activator' by the developer Ryan Petrich.

  1. Download the app from the PlayStore.
  2. Plug in Pressly into the audio connector on your smartphone. Depending on the app, it should indicate that Pressly has been plugged in. For KeyCut users it will display "MiKey plugged in".
  3. Open the app. Upon opening the app, iut will take you to the 'short presses' settings which are by default set to no action or "No action set". The same default settings applies for the 'long presses' too.
  4. Start changing the short & long presses settings according to your desire. You can choose from a whole range of Apps, Personal Settings, Toggles, Buttons, System Settings,etc.
  5. Pressly will also act as a FM Radio antenna for your smartphone.

Step 10: Test Your Pressly

By this point you should have completed making your Pressly and the controlling app should be up and running. Start testing out your Pressly by short and long pressing the push button.

Share your Pressly builds in the comments section below using the 'I Made it Button'.

Leave all your questions and suggestions in the comments section below.

Check out the #rethinkphone for more awesome phone hacks and DIY how to's.

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