How I started wondering to automate some parts of our home..

Our living room and kitchen is in the same space; they are separated by a half-wall. We have a table in the kitchen; with a smaller tablepiece over it…I wanted to install a led strip under the upper one.

I’ve bought the led strip…the power supply for it..and then I was unable to install them; because I would need to replace the existing switch with another one…which is already at a bad position…and because I forgot to buy a box for the 220v parts i needed to install - the whole idea got stuck because of implementation problems.

Somehow I came across some IoT videos…and I wondered: how cool would it be that we don’t even need to turn on any switch/knob or anything…if you walk into the kitchen…it should be aware that you might want to do something in that area…so: something should turn on the light and after a while of no activity it should turn it off.

I already had some arduinos and I’ve played with them earlier…so I started watching arduino/iot videos.

I will walk thru every implementation way I considered so far:

First implementation idea

  • pro mini + some regulators
  • use relays to switch 220v on and off
  • communication: 1-wire or some custom.
  • use cat5 cable to connect communication/power


  • i may use 3-4 wires from existing cat5(or 6 i dont know) cables…this implies that limiting clients to 100mbit/s - this is acceptable because this isn’t a datacenter; and i’m not planning to start one here ;)
  • it might work ;)


  • nonstandard usage of ethernet cables
  • even thru by using ethernet cables - i dont have to run wires everywhere; but i have to cover a few meteres…if i add more devices this might became awkward…
  • relays tend to give a clicking sound ;)
  • relays may use up to 65mA to power their coil; by centralizing the power supply - I’m not only getting a single point of failure; I get a bottleneck opportunity as well! :)


  • I started thinking how to make it happen…so I read a lot more; after a while I ended up changing the communication protocol to RS-485 - because it’s the industrial standard for communication between not-so-close devices ;)

I’ve ordered a bunch of rs-485 parts; regulators etc.. from ebay.

I was aware from the first time that there are xbee/etc devices which can solve the communication without any wires…but I think those devices are a bit overpriced and they are large by the pro mini itself…but after a while I came across nrf24l01+, which looked very much what I want…and I even found esp8266.

  • I settled to use nrf24l01 for communication.

Using rf24 for communication relieves me from wiring communication channels. But I still need to run some DC power to these boxes to supply them power…I’m not sure how it came to my mind…but it came to me:

  • why wouldn’t I use the led strip’s 12V DC supply to power the electronics…those wires have to run there already! :)

it would be cool to only turn on the lights when the kitchen itself is dark…if i use some light resistant thing I might be aware of this fact…it would be even cooler to supply/correct the existing lighting for the “needed” level. But for this to work, I needed finer control over the led strips output brightness…

  • I should be able to dimm it - some mosfet can doit.

Current implementation plan

  • nRF24L01+ module for communication
  • arduino pro mini
  • sensors (dhtXX, light, IR)
  • some mosfet
  • power supplied by the led strips converter

If i’m successfull with the kitchen prototype; I plan to extend this further: replacing our lights with 12v led based equipments.

It might be able to enable to some comfort features, like: * we have a passageway which connects all the rooms; but the lights are a bit intense when i came out from our room - so it should begin with a very dimmed * presence aware lighting in the walk-in closet * removal of switches ;)

Because I’m notoriously leave lights on…this could even help reducing our electricity consumption.

I’m not sure how far I get ;)

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