Capacitive Touch Button Computer Mouse Hack

Mouse modified with capacitive touch button not only helps those with limited mobility (such as ALS), but also makes the mouse click silent

Description

The original idea to improve the computer mouse with capacitive touch sensor instead of mechanical micro switch is to help a friend with limited hand mobility due to ALS (Amyotrophic Lateral Sclerosis, also called Lou Gehrig's disease) to work from home. She needs to use a work station with professional software at home but her condition makes the clicking of a standard computer mouse a daunting task. This can also help those people suffering from Rheumatoid Arthritis or so called 'trigger finger' syndrome due to RSI (repetitive strain injury). These medical conditions lead to hand finger joints exhibiting a limitation of movements that makes mouse clicking difficult and painful.

Additionally it is sometimes desired to be able to use the computer mouse to make less obnoxious clicking sounds, such as during presentation in online video conferencing, or working in the same room with your spouse at home and a truly quiet working environment is desired.

Details

[From Mayo Clinic] Amyotrophic lateral sclerosis (a-my-o-TROE-fik LAT-ur-ul skluh-ROE-sis), or ALS, is a progressive nervous system disease that affects nerve cells in the brain and spinal cord, causing loss of muscle control.

Imagine your fingers are stiff and difficult to click the regular mouse button which requires you to lift up the finger and press down. The idea behind this capacitive touch mouse is to change the mouse click action to lateral movement of your finger in order to touch the surface of protruded electrodes. In this way zero click force is required, and requires much less hand muscle function. This is different than touch mouse on the market which still requires lifting up the fingers to touch.

The design is to hack a standard computer mouse with TTP223 capacitive touch sensor module, and to replace the mechanical microswitch for the left and right mouse buttons with the capacitive touch sensor. No other hardware or software modifications is required. The modified mouse with capacitive touch buttons performs and functions in the same way as before.

This project achieved the goal of hacking hardware to be more user-friendly and inclusive to all types of mobility. It is also beginner-friendly, as all the parts can be sourced inexpensively online and does not require any especial tools or software.

Files

Gerber_PCB_mouse_4_2021-08-19 3x6 panel.zip

Gerber file with 3x6 panel for JLPCB

Zip Archive - 31.89 kB - 11/08/2021 at 01:56

Download

Components

2 × TTP223 Capacitive Touch Sensor Module

1 × DELL MS-116T Wired Computer Mouse Other mouse can also be used, the wiring may be different but the concept is same.

2 × IN4148 Diodes

2 × M3-0.5 x 12mm Flanged Button Head Socket Cap Screw and Nut, 304 Stainless Steel Discrete Semiconductors / Diodes and Rectifiers

2 × 3MM LED Copper Lamp Holder (optional) Round Panel Mount Display for LED

Project Logs

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Final thoughts

Bin Sun • 11/08/2021 at 02:33 • 0 comments

I sent a couple of prototypes to my friend who lives in Canada for testing, she thinks it a great tool for people are in early onset ALS with mild symptoms. I've been trying this device myself a several weeks too, it does require to re-learn the way how the buttons are pressed, but works fairly well once you're used to it. I gave one to my daughter too, she does a loft of editing in Photoshop and found it is convenient for her to do the tracing which take millions of clicks. Sure it does not replace the conventional mouse, but has its advantage in many situations. Have fun.

Testing of V2 PCB

Bin Sun • 11/08/2021 at 02:24 • 0 comments

V2 is working too.

Final assembled touch mouse with V1 PCB

Bin Sun • 11/08/2021 at 02:22 • 0 comments

A success!

Updated PCB from JLPCB

Bin Sun • 11/05/2021 at 17:19 • 0 comments

The new PCBs from JLPCB also arrived.

First customized PCB soldered

Bin Sun • 11/05/2021 at 17:15 • 0 comments

Soldering SMD isn't too bad, a fine tip soldering iron and a lot of patience.

Updated PCB

Bin Sun • 11/04/2021 at 16:27 • 0 comments

I forgot to include the diodes in the 1st version of PCB, therefore the PCB design was revised with the missing components and better layout. Copper pour is also added. The PCB is designed in EasyEDA and ordered from JLPCB. I used panel option to reduce the cost.

TTP223B chips

Bin Sun • 11/04/2021 at 16:20 • 0 comments

The purple PCBs from OSH Park

Bin Sun • 11/04/2021 at 16:02 • 0 comments

The purple PCBs from OSH Park has arrived. Now let the fun begin.

First PCB ordered.

Bin Sun • 10/18/2021 at 23:56 • 0 comments

First time created my own PCB design and placed order at OSH Park, keep my fingers crossed. Waiting for components arriving on a slow boat.

August 21, 2021

Bin Sun • 08/21/2021 at 04:03 • 0 comments

First publish of the project design.

Build Instructions

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1

Prepare the Mouse

I modified the computer mouse with two different designs. The simple ways is to remove the original micro switch for the left and right mouse button, and use two M3 stainless steel screw as capacitive touch sensor electrodes at corresponding locations. This should work for most of the people. I also created another version that uses 3mm LED with metallic (copper) socket as touch sensor electrodes with LED as visual touch confirmation. This latter design allows one finger to control both left and right button with visual confirmation, and is more suitable with the consideration for the ALS patients. You can decide which one works for you.

Dell MS-116t wired mouse is chosen in this project as example because I happen to have several of them laying around. They are inexpensive, easy to work with, and have good quality and performance, and compatible with Windows PC, Apple iMac as well as Chromebook. It is based on PixArt PAW3515DB chip which can be found inside many of the computer mice. The same concept can be applied to variety of the computer mouse with minor modification to the wiring.

Capacitive Touch Mouse Designs

Step 1

The first step is to dissemble the mouse by removing the bottom Teflon pads with a knife or small screwdriver, exposing the 2 Philips head screws underneath.

Step 2

Once the screws are removed, the top and bottom of the mouse will separate easily. Remove the printed circuit board and remove the left and right mouse button micro switches using disordering iron.

Step 3

Drill holes at appropriate locations at the top mouse shell. The top mouse shell consists of two parts and can be separated. I will first drill a small pilot hole with two parts connected, then separately to make sure that I don't damage the top surface. Additional washers can be added between the top and bottom to make the mouse completely non-clickable.
2

Modify the TTP223 Module

I purchased the TTP223 Module from Amazon, which needs to be modified to fit our needs. First a 30-33 pF capacitor needs to be added to the empty pad on the board to get appropriate touch sensitivity. Also by default these modules are in toggle mode with output signal active-high. According to the mouse circuit diagram, the right mouse button switch is active-low, therefore we need to make the TTP223 module output goes to the right mouse button active-low. This can simply be done by bridging the pads marked A on the module (AB=10). Also remove the SMD LEDs on the modules if optional external LEDs are going to be used.
3

Wiring and Assembly

First, connect the touch electrodes to the TTP223 modules by soldering a wire from the module to the base of the electrodes. A copper washer should be used if the M3 stainless screw is used as electrode, since the stainless steel can not be soldered.

We then need to connect the TTP223 modules to the +5V power and ground as well as the left and right mouse buttons on the computer mouse PCB. Below is complete wiring diagram with the optional touch button LEDs included, as well as the location of connection points to the micro switches pads on the PCB. Two IN4148 diodes are added between the outputs of the TTP223 modules and the button inputs on the mouse PCB to eliminate the false signal.

Schematics

PCB Connection Points

Finished Touch Sensor Module

View all 4 instructions

Discussions

Bin Sun wrote 08/21/2021 at 04:02

This project is still ongoing. After successful testing of the prototype using the off-shelf TTP223 module, I'm going to make dedicated PCB with smaller footprint and better efficiency. Also I have made several of them and shared with people with hand mobility for testing. Stay tuned.

Are you sure? yes | no

goathens wrote 09/10/2023 at 20:56

I've found this specific off-the-shelf ttp223B module doesn't allow me to touch and hold for an indefinite period. No matter how long I touch the capacitive surface, the I/O pin will only send signal (high or low) for about 6 seconds before stopping. That's not allowing enough time for a drag-and-drop behavior on my mouse. Have you overcome this limitation? perhaps I have a different SKU of ttp223b module.

Are you sure? yes | no

Capacitive Touch Button Computer Mouse Hack

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Files

Gerber_PCB_mouse_4_2021-08-19 3x6 panel.zip

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