Sonsivri

I am starting a new project for home automation.

I am in the UK so we have some quirky wiring in our lighting circuits in that only the live wire goes to the switch, (no neutral return) so pulling power from there is pretty challenging.

This circuit is a PIC based controller, it takes power from the mains live feed, and derives the VDD at +5v from it.

*** THIS DESIGN USES MAINS VOLTAGES AND HAS NOT BEEN FULLY TESTED -- USE IT WITH EXTREME CAUTION ***
                                                          * potential to die if you mess up! , if you die, don't come haunting me! *

If you don't feel happy potentially debugging a circuit on mains voltages please stay away.

There is no code for the processor yet, as the design is incomplete.

The SCR is controlled by the pic and turns the lighting appliance on.

If you want to reduce costs, why not use the capacitor step-down circuit ?


BTW, which communication protocaol you will use? X10?

No, I have some X10 equipment at home now, and find it to be quite slow and unreliable.

I have found some 868MHz RF modules that have all of the encoding/decoding built in, and have a programmable 32-bit address.
Packets of data between them include the source and destination addresses, so it's quite a nice system.

As for software protocol, I am writing our own, but may possibly use something like xAP for some kind of compatibilty.

Hello,

It's excellent that you're working on home automation (particularly in, and for, the UK!) It's going to be a big market. I have some observations on your schematic - I hope you don't mind me commenting...

1. It looks like the voltage developed across R1 is dependent on the power of the lamp in the fitting. This may be ok with incandescent lamps upwards of 60W, but I'm not sure it'll work with low energy, or lower power, lamps.

2. You have a 1MEG resistor (R3) in the gate drive to the triac (T2.) The TICP206 needs the order of 8mA to turn it on - You won't get this with 5V through 1MEG.

3. The leakage current through triacs is quite high, so with low energy lamps you may get flickering, and worst case could damage the lamp fitting (electronic) ballast.

4. Your system allows only switch off - not on - if the mechanical switch is on (as it appears that the terminals are in parallel with the triac.) Of course, you may not be intending to fit a mechanical switch too...

I continue to look for an elegant solution to cheap, electronic, control of low-energy cfl lamps (as an (unhelpful) aside - I absolutely hate them, but we're all being forced to use them, even though the technology is rubbish - LED needs to catch up quick!) So far relays have been the only reliable solution for me.

I agree with your X10 comments - I really don't think much of it at all. The nicest system I've seen is based around Crestron equipment and KNX. It wasn't my system, and it cost ££££££s  :(

I hope these comments are of some small help.

Good luck.

Anifkin.

Hi Anifkin,

Thanks for your reply..
I am great on digital electronics, but "ok" on analogue...

1. indeed, I have been testing some of the design with a 100w incandescent bulb.. I will dig out the cheapo cfl that nPower sent me.
2. it has been a little "random" wrt turning off/on so this is most likely the cause.  I haven't had much chance to work on this lately, but hope to get back on it.
3. good point again - I will look at some other switching methods - triacs are obviously the easiest.
4. Yes, in the design as show, there is place for a switch, this is a hang-back to my "put test methods in place dammit" methodolgy.. Flick a switch - it comes on, so the power/bulb is there!
  There will be an input on the chip with a digital switch on/off.  otherwise the automation couldn't do a "all-lights off"

cfl ARE the worst design in the world..  LED's for me please.

-Mole

One problem I have is with the UK mains lighting circuits only having live feeds now, that's why I had the trickle through the resistor :/
Give me the good ol' fashioned dangerous light fittings every other country has :D

crazy people that we have in charge of the grid here.

well if your going to use X-10, i-red, wi-fi, or though the mains signals to control lighting, then your control unit belongs in light fitting or in ceiling/or/rose, original switch wires still used as normal.

Hi Pickit,

I am leaning towards that solution already,

put the mains voltage stuff up out of the way and put low voltage signalling down in the switchplates.