Anth's Computer Cave

Wireless home-automation satellite: Part One

31st October 2015

Today I'll show you the new prototype wireless home-automation satellite for the AAIMI Project.

A wireless satellite with light, temperature and movement sensors. Picture: Anthony Hartup.

This satellite is designed to extend the reach of the AAIMI Home Automation system to places where cables can't reach.

With the current base-station configuration the system can run five of these wireless satellites.

Where possible we've used salvaged parts for the prototype. The casing is from an old, large-button cordless-phone base.

An old large-button cordless phone base. Picture: Anthony Hartup.

We removed the mainboard and button panel from the unit. The large button panel may come in handy for later projects.

The mainboard had nothing I really needed.

The components inside the phone base. Picture: Anthony Hartup.

With the old internals removed we had tons of room for our new components.

The empty casing from the phone base. Picture: Anthony Hartup.


Like our cabled home-automation satellites this one has a movement sensor, light sensor and temperature sensor, as well as a relay to switch lights on and off.

As well as the normal sensors, the wireless satellite also has an Arduino micro-controller to read the sensors and communicate by radio with my main base-station.

An arduino Uno and aPicture: Anthony Hartup.

The radio is an extra-cheap nRF24 module. I paid about $1.20 on ebay for these ones. You'll also need a radio for the Arduino in the base-station.

I haven't really tested their range yet. If you need long range you can spend more and buy a module with a larger antenna.

An nRF24 radio module connected to an Arduino. Picture: Anthony Hartup.

Regardless of the module you buy, you will need to solder a capacitor across the positive and negative pins. Without these capacitors I found these modules completely useless.

Now for the sensors.

A sensor board with light and temperature sensors.Picture: Anthony Hartup.

This is a combination board with the light and temperature circuits we've used throughout the series.

The movement-sensor return wire also connects via this board through the vertical resistor on the left.

The light fitting attached to the relay. Picture: Anthony Hartup.

Next we attached a light fitting and wired it to the relay. This was one end of an old light-extension cable.

The casing

There were two large holes to fill in the top cover of the unit.

We used some pieces cut from the outer screen of an LCD TV we tore down in the cave recently.

A piece cut from an LCD screen. Picture: Anthony Hartup.

The curved lower section we shaped down to fit precisely in the hole and applied a couple of drops of super-glue.

The finished top cover for the wireless satellite. Picture: Anthony Hartup.

The other piece for the upper hole was easier, we just screwed in from underneath.

The finished top cover for the wireless satellite. Picture: Anthony Hartup.

Lastly, we secured all the pin-connections with tape so they would stay in place as we closed the lid.

Picture: Anthony Hartup.

The satellite is almost done, but there are a more tasks.

The finished wireless home-automation satellite. Picture: Anthony Hartup.

Firstly, we need to make a swiveling holder for the movement sensor. These sensors are difficult to mount because the have no screw-holes. I think I'll glue it into a bracket and attach that to the casing.

Secondly, I forgot to drill a hole for the Arduino's USB port. I need to disassemble the unit and drill another hole in the rear, otherwise I'll have to pull everything apart any time I need to re-program the unit.

The code

The hardware is finished, but it's not going to do much without some code to run everything.

In part two of this article next week I'll show you how the system works.

I'll share the code for the Arduinos, and a Python script to control it all from a Raspberry Pi.



Previous: Mini home-automation satellite

Next: The AAIMI home-automation software modules.



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