Humble Beginnings Of A Home Automation Project


This board is the start of [Steven Pearson’s] quest to automate his home. The module will be used to prototype the rest of the project. Right now it uses an ATmega328 chip running the Arduino bootloader. This connects to one mechanical relay which we would wager is mains rated. The module will be controlled wirelessly via the wireless module seen in the foreground. That is a nRF24L01 board which he chose because of it’s bargain basement price tag of around $1.50.

There is much room for expansion in the system. You can see that a light-dependent resistor has been added to some of the microcontroller’s breakout pins. We would guess that [Steven] will use the hardware to develop for many different functions and will design more task-specific modules as the project progresses.

If you’re a fan of PCB milling and population you won’t want to miss the video after the break. [Steve] posted a fast-motion video of the entire process.

12 thoughts on “Humble Beginnings Of A Home Automation Project

  1. Using the light sensor to turn on a light when it is dark, or to close a curtain/shade when it is sunny, or sound an alarm when the refridgerator door is opened (while on a weight loss plan). Yep! A good first step.

    1. Because some loads don’t like triacs, they don’t missing some part around the zero crossing. SOme don’t like the leakage. Some loads don’t like electronic switches.
      Because once you ad an optocoupler capable of driving the triac it will cost about as much as a relay.
      Because triacs can be triggered by noise in the network, connection the load for a short time.
      Because a triac will dissipate more power for larger loads(you probably need a heatsink over around 1-2A).
      Beacause i’ve seen many 4A triacs blow when the 100W bulb blows(the 1.5A slow fuse was fine though).

      Look at commercial stuff: there are dimmers and there are switchers that use either relays or SSR.

      1. * The loss around zero can be neglected if you keep the gate on.
        * Depending on the circuit design, they do not trigger by noise.
        * Optocouplers cost in the order of 10’s of eurocents.
        * They do not require a heatsink above 2A. I’m using one at 6A continuous for a motor, just standing up on the pcb. Granted, there is some ventilation.
        * Not sure why they would blow with the 100W light bulb. Maybe no snubber?

        But okay, relays have their place, but in my experience they wear out quite fast.

  2. I’ve started some similar thing… so long ago. Never got to actually function in practice.
    I was using RFM12 though, much better range, less interference in the 868MHz band… though more expensive.
    I made a PCB with 4 triacs and three relays and a pcb that could accept sensors. a central node would get the data an send it to some software.

    This is where things get ugly: even now there’s no software that can do what i want. It also has to be free and opensource.
    Had a look at OpenRemote and OpenHAB. They are still young… openremote is nice for creating panels and just controlling. it lacks functionality for automation. OpenHAB has a bad interface but can do automation better. Both of them are meant for commercial existing protocols, it’s hard to add your own(at least for me, i don’t know java).
    There’s mr house which seems abandoned and ancient….

    Maybe someone can show me something that i missed….

    1. The reason for the 328 was to be able to expand the solution for several sensor inputs and to drive multiple relays. Is is just an early prototype for development. For sure though, if it was just for a single relay and a sensor you are right.

      1. Using a large enough micro might not be that expensive. You will save money by buying more of the same part. And don’t forget that the micro is just one part in the system.
        Theb you save time and money by designing and building less pcbs.
        Also, the 2313 lacks adc.

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