Homini In-Wall Light Switch Module - Revision 2

Brief Description

Module was created at http://forum.mysensors.org/topic/2511/in-wall-light-switch-node-custom-pcb by myself and many inputs from yourselves.

This ATmega328p-au based board has been created to enable you to have what is essentially a extremely low powered, low current wireless switch. It was designed with the use as a light switch in the primary driving seat, however you can use it as any switch you would like. The Micro Controller, when not in sleep mode, is running at 8MHz, using the internal crystal to bring the power consumption right down to what is supposedly around the same power consumption as the self discharge rate of the 3v3 coin cell battery power supply. The only disadvantage of this is that Atmel themselves do not support the use of Serial connections when using the internal crystal, however we do have it working perfect. We are able to upload through the serial connection and also monitor the serial communication through a FTDI programmer. This requires us to use a baud rate of 9600 with a copy of Gertsanders bootloader.

Physical Dimensions

• Height: 16mm
• Width: 26mm
• Length: 48mm

Connections

• Screw Terminals for switch wire connection
• ISP for programming
• FTDI for Serial Monitoring (Uploads may work in Revision 2 but not supported)
• nRF24L01+ for radio frequency connection to gateway module

Power Supply

3v3 Coin Cell Battery. Other variations of this board may be available in the future but currently we only have a working battery version.

Software

Bootloader

With special thanks to forum and community member 'GertSanders' for providing the branch of OptiBoot's bootloader with an upload speed of 9600.

FUSES

PLEASE NOTE THE FOLLOWING FUSE CHANGES FOR CORRECT BATTERY CONSUMPTION

• Low Fuse: 0xE2
• High Fuse: 0xDE
• Extended Fuse: 0x06

The current software that runs on the module is that of BinarySwitchSleepSensor, at the time of creating this module this software is located in the development branch (V1.6). The code is as shown on Source Code tab of this project.

Function

This module can be used as a generic switch that relays a 1/0 ON/OFF to your gateway.

Battery Monitoring

The monitoring method that would suit this module would be a software version, specifically that of 'secret voltmeter'. This is perfect for this module because the module gets its VCC straight from the battery without any step-ups or voltage regulators to filter its power. This enables us to have battery monitoring at virtually no extra power consumption unlike the conventional hardware monitoring variations. I'm currently working on getting this integrated with the module. Soon as I get it in a working, in a stable sense I will upload added information regarding this. However, as with all open source projects, feel free to experiment and implement this beautiful feature yourselves!

Power Consumption

I have been running this module since day one and we're still going strong with a voltage reporting close to the original. So at the moment we are at 1 year on this battery. (as of 26/02/17)

I'm very interested in all of your variations, improvements and applications of this module, please add them to the comments with pictures and videos if you can.