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'Home Automation using PICs'
1995\12\16@103117 by Chris Smolinski

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I'm having a new house built, and what to put some "intelligence" in it. I
haven't decided exactly what and how yet, but I am going to run a lot of
wiring in the walls, so at least I will have that in place.

I have been thinking about using PICs, and here's what I have come up with
so far. Comments/suggestions welcome:

I plan on having a four conductor cable run throughout the whole house for
the PICs. Many drops in each room (perhaps with a modular phone type plug
for ease of connecting PIC devices, maybe an oversized plug so someone
doesn't accidently plug in a phone!). The four conductors would be used as
follows:

1. GND
2. +12V (maybe higher)
3. -12V (maybe higher)
4. Data (multidrop)

Modules with PICs would be plugged in. Each would have its own address. In
general, each module would only speak when spoken to by the controller,
although I would probably have some mechanism to allow modules to issue a
service request when they have something urgent to report. Modules could be
either outputs (such as to open or close a heating vent, turn on a light,
etc) or inputs (sensors, such as temperature in each room, motion sensors,
etc). I/O modules could exist also.

Some modules may be intelligent, such as a module that directly controls a
fan that turns on when it gets too hot (above a temperature setpoint sent
over the network). That way the control unit doesn't have to handle all the
little details.

The +/- 12V would provide power for each module.

The control unit will consist of a Mac with a PIC unit connected to it for
the system interface. I'm using a Mac because (a) I am a Mac user anyway
and (b) The control unit Mac can communicate with other Macs on my
Appletalk network. So from my Mac upstairs (or any other Mac in the house)
I can run a program to control/monitor the house. It commmunicates with the
controller Mac to actually communicate with the PIC modules.

I haven't really seen any inexpensive systems on the market that will do
what I want, plus the experimenter in me really wants to play around with
it anyway!

I probably will also use X10 modules to control lights, lamps, etc. But X10
seems rather limited. I have also heard of high failure rates of modules.
And as a ham radio operator, I am concerned that they will cause
interference (I'll get one or two to test first).

I'm also interested in the Dallas 1620 temperature sensors. These have a
built in A/D, so they send a 9 bit word representing the temperature, and
only require two wires (GND and Power/Signal). Plus each has a 64 bit
address, so they are multidrop. I'd like to drop them all over the house to
monitor the temperature in each room, and open/close air vents as
necessary. Has anyone played with them yet?

Anyway, this is all rather vague right now. My first goal is to make sure I
get enough wiring infrastructure in the house first, before the drywall
goes up.

Chris


P.S. I haven't completely stopped working on the Mac ADB PIC interface I
was working on. The A/D and D/A works fine, I just have to add digital I/O.
I'm contemplating writing an article for Nuts and Volts, has anyone written
one before?


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1995\12\16@104349 by Ian Stirling

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>
> I'm having a new house built, and what to put some "intelligence" in it. I
> haven't decided exactly what and how yet, but I am going to run a lot of
> wiring in the walls, so at least I will have that in place.

>
> Anyway, this is all rather vague right now. My first goal is to make sure I
> get enough wiring infrastructure in the house first, before the drywall
> goes up.
>
> Chris
Might be an idea to add in ducting, with string in, so you can drag fibre/or
whatever you want round at a later date.

>
>
> P.S. I haven't completely stopped working on the Mac ADB PIC interface I
> was working on. The A/D and D/A works fine, I just have to add digital I/O.
> I'm contemplating writing an article for Nuts and Volts, has anyone written
> one before?
Have you found any net sources for info on the ADB? I've looked in vain,
or are you using a paper referance. (I've found some specs for the software
side of ADB, but am interested in the harware, WRT doing things like making my
own infra-red ADB extender.
{Quote hidden}

--
Ian Stirling.                        |  http://web.students.stir.ac.uk/~is06
AKA Caeser, Bolonewbie.              |  Pretty sad at the moment, should get
                                    |  better tho.

1995\12\16@105836 by Chris Smolinski

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>> P.S. I haven't completely stopped working on the Mac ADB PIC interface I
>> was working on. The A/D and D/A works fine, I just have to add digital I/O.
>> I'm contemplating writing an article for Nuts and Volts, has anyone written
>> one before?
>Have you found any net sources for info on the ADB? I've looked in vain,
>or are you using a paper referance. (I've found some specs for the software
>side of ADB, but am interested in the harware, WRT doing things like making my
>own infra-red ADB extender.
>>

No net sources, I am using the info in Microchip's handbook, and Apple's
Hardware Ref Manual.

Chris


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1995\12\16@175314 by Clyde Smith-Stubbs

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Chris Smolinski <.....cpsKILLspamspam.....ACCESS.DIGEX.NET> wrote:

> I'm having a new house built, and what to put some "intelligence" in it. I
>
> I plan on having a four conductor cable run throughout the whole house for

I have been thinking similar things, only my house is already built, and
has no easy way to run cabling _anywhere_ - but that's another story - if
I ever build a house it will have ducting everywhere for high and low
voltage wiring. Here's my $0.67 worth;

Anyway, my plan is to use 8 way UTP cable, just like that used for 10base-T
ethernet. The 8 wires will be used as (order of allocations not yet
fixed)

1 & 2   +12
3       Audio 1
4       Audio 2
5       Signal 1
6       Signal 2
7 & 8   Ground

For connectors I plan to use standard 8 way modular plugs (again ethernet type -
they're cheap) and each controller box will have 2 sockets (jacks to the Yanks)
with pass through connections (can't think of any way of simply tapping this
kind of cable) with provision for local power supply. This would mean that there
could be several sources of 12V rather than trying to run everything from
the far end of the cable.

The cabling and control boxes are intended to be not readily accessible, so
plugging in a phone should not be a major problem (although you can plug a
4 way modular connector into an 8 way socket).

The signal pair will be RS485 or similar; the audio pair will be used for
intercom purposes etc. - haven't fully figured that out yet.

In each box will be a 16C74 or something similar (doesn't have to be a PIC).
The '74 has a serial comms port, A/D and an SPI port for local expansion.
I have in mind that each box will have one board with the CPU and expansion
boards as necessary with temperature sensors etc, digital in/out. I'd
prefer to use hardwired control for AC power, rather than X10, for
reliability and also because I want to know if things are on.

I'd been speculating about detecting AC current flow by having a few turns of
wire around one side of an AC pair, and amplifying/detecting this to detect,
and even measure current flow. Anyone done anything like this? The idea is to
be able to remotely turn stuff on, and verify it's running, but also detect
things that are on (local override) when they shouldn't be (hmm - pool pump
has been running for 7 hours - which of you kids turned it on??? That fridge
door
in the garage  has been open for 10 minutes. Whoop, whoop whoop! Oh, you're
defrosting
it? Sorry!)

All this is just dreams at present - I'm going to start small with a few
temperature sensors around the place (make sure the A/C is working!)

We now return you to our regularly scheduled program...

--
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1995\12\16@233042 by Mike Keitz

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>Anyway, my plan is to use 8 way UTP cable, just like that used for 10base-T
>ethernet. The 8 wires will be used as (order of allocations not yet
>fixed)
>
This is a good idea.  Using the Category 5 type of 4-pair cable, you should
be able to run 100 Mbps.  Also, running all the cables back to a central
point (attic, basement, wiring closet) gives the most flexibility in how
they are interconnected rather than dedicating the whole house to a bus
structure, which is likely to have trouble with high-speed signals.  Then
you can mix and match different "services" to different outlets.  Since it
is so much cheaper to run cable before the house is done, I'd be tempted to
run a couple of 8-pairs, a 75 ohm coax or two, and maybe some sort of fiber
to each location.  You're bound to want to use them someday.

You can tap and interconnect cable of the unshielded twisted pair type using
a "punch-down block" which is basically a big breadbord of clips that you
force the wires into.  Each set of clips is wired in pairs or threes, much
like the standard IC breadboard has its rows of holes interconnected in
groups of 5.  When insulated solid #22 or #24 wire is pressed into them, the
clips displace the insulation and make a solid connection, although I have
to admit that the whole affair looks like a rat's nest from hell, even when
installed carefully (that's why it's in the wiring closet).  They've been
used for analog telephone wiring for a long time.  You could even use one or
more of the pairs in the cable for telephone lines if need be, and punch
them in to suit your needs.

>could be several sources of 12V rather than trying to run everything from
>the far end of the cable.

This cable can't support much power anyway (on the other hand, most PIC
projects don't require much).  Be sure to protect the cable with a fuse or
PTC device at the source end. it's probably not safe for more than a few
hundred mA.

>I'd been speculating about detecting AC current flow by having a few turns of
>wire around one side of an AC pair, and amplifying/detecting this to detect,
>and even measure current flow. Anyone done anything like this?

Just wrapping turns of wire around a conductor does not work, as the
secondary "winding" is then perpendicular to current flow in the "primary"
wire.  Thus no magnetic coupling occurs.  Usually a ferrite or iron core is
used to make a closed magnetic circuit around the primary wire, with many
turns of secondary and just pass through for the primary.  The secondary
current is then primary current / N.  This is accurate enough to measure
electric power for utility metering purposes (customers that use several
hundred amps of power have current transformers attached to each phase of
the line, rather than the home type of meter that passes all the current
through the meter mechanism itself).

For homebrew purposes, you could probably build a current transformer using
a small power transformer of the "split bobbin" type (windings adjacent to
each other rather than on top of each other).  Remove the existing
low-voltage winding and pass the high-current wire through the space
created.  With a current transformer, the secondary voltage is theoretically
hard to define (depends on the inductance of the core, etc), thus it is
necessary to keep the sensing winding connected to a low-impedance load at
all times to keep the secondary voltage from soaring up to a dangerous level.

-Mike

1995\12\17@113355 by John Welling

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Before you get lulled into the novelty of homebrew device control,
Please take a long and healthy look at the strategy for 'Networking'
your PIC nodes.  How will you manage the address of each node?  Will
they be grouped or segmented?  How will they get
'broadcast-to-all/group' system updates from host?  How will you handle
the shifting priorities of arising emergency conditions?  How will the
system & network handle accidental collisions of data on the network.
Each PIC node unit will need to do the device control and manage
network comm protocol.  You may want to use an LSI chip to handle
network overhead.  How will you load sfwr changes to the node MCUs and
call/schedule their data feeds to the host?  Can nodes
exchange/share/control devices by interacting between themselves?  How
will the host moderate/assign such 'distributed processing'?

Good reading is the Byte & Circuit Cellar Ink magazine articles on the
development of Home Control System by Steve Ciarcia.  His ongoing
discussion of path choices will save you from reinventing the wheel.
Also get info on LON-Local Operating Network and CEBus.  Then you can
better establish the architecture of your system


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1995\12\18@003816 by Przemek Klosowski

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  >I'd been speculating about detecting AC current flow by having a few turns
of
  >wire around one side of an AC pair, and amplifying/detecting this to detect,
  >and even measure current flow. Anyone done anything like this?

  Just wrapping turns of wire around a conductor does not work, as the
  secondary "winding" is then perpendicular to current flow in the "primary"
  wire.  Thus no magnetic coupling occurs.  Usually a ferrite or iron core is
  used to make a closed magnetic circuit around the primary wire, with many
  turns of secondary and just pass through for the primary.  The secondary

To be exact, the magnetic field, B, is perpendicular to the current
flow (field lines form circles around the conductor); you have to
collect as much field flux as you can (maybe using a split ferrite
core), and wind your loop around this core (multiple turns amplify the
voltage). The idea that the flux created by the conductor has to also
pass through your measuring loop; generated voltage is proportional
to both number of turns and the normal component of the flux wrt. the loop
plane. In simplest case, you could just put your loop next to the
conductor without any core; since B drops off as 1/r it pays to make the
loop long, thin and parallel to the wire.

1995\12\18@024454 by Philippe TECHER

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On Sat, 16 Dec 1995, Chris Smolinski wrote:

>I'm having a new house built, and what to put some "intelligence" in it. I
>haven't decided exactly what and how yet, but I am going to run a lot of
>wiring in the walls, so at least I will have that in place.


Why don't use directly the current home wires. You can add on the power line
a FM signal (about 110-160 KHZ). Try to check the LM1893 application note. I
think there is no need of high speed communication in a home network.

With  LM1893 you will be able to send and receive logical signal up to 4800
Bauds. This circuit have a PLL and FM demodulator to recieve, a FM modulator
and power output stage.
If you want to get something as small as possible, you need also to get
power directly from the power line via a step-down-converter (see also MAXIM
product).

* if your design have a very low consumption (<15mA), and want to connect
directly to a light, you can steal some current through the light to get
power. This is realize with a TRIAC by open the gate a very little time,
just enought to charge a capacitor and just enought to get the light "turn
off". When the light is on, the same system can be use.

LM 1893 is not the only solution, you can also build yourself a
transmitter/receive with a 4046, some OP and power stage ... The main
problem with LM1893 is it need +12V ...

I know there is also some hybrid module wich are able to transmit and
receive data on a power line, try also to check ECHELON circuits.

The hard job is to define exactly the communication protocol. I think OSI
model is a good starting point ( just follow level 1,2 and 3). In my mind,
the best way to define such a protocol is like token ring, with a busy/free
flag on the current frame.

Regards,
               Philippe.

1995\12\18@115751 by Byron A Jeff

face picon face
-
- On Sat, 16 Dec 1995, Chris Smolinski wrote:
-
- >I'm having a new house built, and what to put some "intelligence" in it. I

- >haven't decided exactly what and how yet, but I am going to run a lot of

- >wiring in the walls, so at least I will have that in place.

- Why don't use directly the current home wires. You can add on the power line

- a FM signal (about 110-160 KHZ). Try to check the LM1893 application note. I

- think there is no need of high speed communication in a home network.

- With  LM1893 you will be able to send and receive logical signal up to 4800

- Bauds. This circuit have a PLL and FM demodulator to recieve, a FM modulator

- and power output stage.

There's your reason not to right here. It takes quite a bit of effort to send
information on the power lines. The bottom line is when you don't have drywall
up, dropping conduit/cable in the wall is the most efficient thing to do.

I'd advise putting in conduit (1 inch PVC would be wonderful). Then you can cut
out panels in the wall wherever you like. Be sure to put a string in the
conduits so that you can draw write through it. It's absolutely the most
flexible option...

BAJ

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