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Topic: Home automation (Read 600 times) previous topic - next topic


Hi All,

I am trying to automate my staircase lights now.. there are about 6 of them.. right now my electricians have setup it all with 2 way switches.

each 2way switch is connected to 2 lights at a time. so switching them on will set 2 lamps to be on at a time.

I have an arduino, and have a fairly basic understanding of how things work in this regard and how to use digital signal to trigger relays with transistor.

Now question is in the actual implementation.

I have like 3 PIR sensors.. that i would place at 3 places on 3 floors to detect movement and use that inputs to trigger my lights.

How do i run these small wires over a longer distances? say about each floor is atleast 12 feet high.. will digital signals/voltages go over 36 feet easily?

Can i buy a wire like this ?

or a normal twisted wire ( one they use for small speakers) will do the job? , I can buy the normal jumper wires i used to experiment for longer distances but worried this could easily damaged on longer term// also dont know much about voltage drops,etc.

I heard on this forum that I cannot pass these wires together with the AC grid wires, should i use seperate pipings? I would love have it as internal wiring. any options here?

Another unrelated question about the Relays

I am thinking to buy a relay control board like this

There is also 4/ 8 relay boards like this in ebay, will this do the job? i am worried abut drawing too much current out of the arduino and exceed the limits.

how many relays is safe to run on the same power adapter? or from the arduino 5v itself?

I plan to learn things with this 6 lights to start.. I would love to control them all separately but even if I wire them in 2 pairs so a relay controls 2 lights, im fine with it.
then slowly add other room lights into the mix.. how do this scale..

how many arduino's(Mega) I m going to need to completely automate the home lights and fans.. which is about 14 in total.

I would also get a Raspberry Pi for web control for all my lights/fans very soon , may be use this as the base station
I am much better at software side of the things than the hardware wiring,etc . I can code my own android/iphone and web app that controls this easily .

I did try to google a lot/etc, I couldnt find all the answers there. I started with arduino like 2-3 weeks ago sorry for all the silly questions if they are.

Is there any open systems like "open energy monitor" for home automation so I am better off purchasing all the components and use the set standard instead of redoing it.


Lots of questions.  Let's tackle this one thing at a time.  A Mega will give you a lot of outputs, but you can do the same with an Uno and shift registers.  These use SPI (serial) to communicate with the micro, and then provide a certain number of outputs (typically 8) that can be individually enabled.  If you need more, you can daisy chain them.  Look at the shiftOut docs for examples of parts and code.

You should not run high voltage and low voltage signals together.  Separate them at least a couple inches to avoid induced noise from the HV AC hum.  There are often code regulations about how you handle HV/LV wiring as well, like not having both exposed in the same junction box.  You'll have to check your local wiring code to be sure, but a safe bet is to keep them completely separate.  Using UL-approved LV-controlled enclosed relays may be something to look into as well.  I'm not an expert on code, so hopefully a qualified electrician can make some suggestions on that.

The distance you can run is often a function of frequency.  If you run low-speed serial, you can go quite some distance.  You might want to use shielded coaxial cable.  Not cable TV necessarily, but something with an outer jacket, foil or braided shield, then one or more conductors within.  Like line level, headphone, or microphone cable for instance.  Twisted pair will only be useful if you use differential signalling, but that would require a single-ended to differential driver on the sending side, and diff to SE at the receive side.  That's not too difficult, but at the distances you need to send, it's probably unnecessary complication.


Thanks for the answer, Regarding the wires, I do have lots of cat5 ethernet cables.. is it possible to carry these digital signals over that without added devices/chips?


Cat 5 will work just fine.

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It will, but Cat5 is twisted pair and usually unshielded.  At relatively short distances and low frequencies you can get away with just about anything, so you'll probably be just fine.  Shielded coaxial is technically better.


We have CATkits (Arduino shields) and Kittens (satellite boards) that handle up to 18, 5v signals over CAT5.  They have been tested to over 100m with most protocols.   This is the website (usual disclaimer) http://smartgreenhouse.org
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