Its amazing that we just touch our mobile screens and they work like magic and do things. Now it is very common so we might not feel very awed about it. But, if you think, that’s a great invention and leap of technology, where a simple touch can be used as an input in devices to perform actions. The module which is responsible for carrying it out is the capacitive touch module.
A MPR121 module features 20 pins, as follows:-
| Pin | Function |
| IRQ | Open Collector Interrupt Output Pin, active low |
| SCL | I2C clock |
| SDA | I2C data |
| ADDR | I2C Address Select Input Pin. Connect the ADDR pin to the VSS, VDD, SDA or SCL line, the resulting I2C addresses
are 0x5A, 0x5B, 0x5C and 0x5D respectively |
| VREG | Internal Regulator Node – Connect a 0.1 μF bypass cap to VSS |
| VSS | Ground |
| REST | External Resistor – Connect a 75 kΩ 1% resistor to VSS to set internal reference current |
| ELE0-ELE11 | Electrode 0 to Electrode 11 |
| VDD | Connect a 0.1 μF bypass cap to VSS |
How to use
A step-by-step tutorial – Article Link
Common Applications
1. Mobile phones.
2. Touch pads, touch slide bars, etc.
Some example projects that students can try out in the ATL Lab
1. Make a music organ using capacitive touch module MPR 121 (https://youtu.be/AhVizoU8CB4) YouTube Video
Safety Measures to follow
● Do not put anything liquid with the interface of the module.
● Don’t apply excess pressure to the sensor part as it may get damaged.
Important Links
1. How to use MPR 121 module (https://www.youtube.com/watch?v=tTMsbL0eH_M)
YouTube Video
