RE: HA control of your Air Con unit

[Keith Doxey <ukha@xxxxxxx>]

Interfacing to a device such as the Aircon or a Satellite receiver that has
a low voltage control panel is a Piece of P***.

You use a multimeter to detect with side of the switch is more positive
than
the other when the switch is open. Typically you will see a reading of 3-5
volts.

All you  have to do is wire the Transistor of an Opto-Isolator across the
contacts with the correct polarity. You then connect the LED of the
opto-isolator t  your HA controller via a suitable resistor. Lighting the
LED simulates pressing the button.

You MUST use and Opto-Isolator for safety but these come in Single, Dual or
Quad packages and are cheap.

No feedback is NOT a good idea.
For example the "Mode" button on the Aircon cycles round
Fan,Cool,Heat. If
someone has pressed the button to turn Cooling on and HV presses the button
you will turn the cooling off and heating on. It probably wouldnt heat the
house as the room temp would be higher than the temp setting, unless you
has
a powercut whereby the heat setting would have defaulted t  26C.

As you say, you can get to a "Known State" by using an AM to
reset the unit
but you would have to do that EVERY time you wanted t  adjust it just
incase
someone had pressed a button :-(

Keith

-----Original Message-----
From: Ian Bird [mailto:I.Bird@xxxxxxx]
Sent: 05 July 2001 10:17
To: Ukha_d
Subject: [ukha_d] HA control of your Air Con unit


Having read the previous post about automating the Homebase A/C units I was
just wondering..

I have HomeVision but am currently using most of the relay output ports for
my watering valves. I know Port C can be configured for output but can only
drive ttl, cmos, leds or similar. I don't see any reason why this could not
drive a transistor and that in turn either simulate the switch or a relay
to
simulate the switch (depending on the requirements). That would give HV
control over the unit with manual override available (but no feedback).

This is something I might look into soon(ish) as it would be dead useful.
The lack of feedback would not bother me particularly as I could always
reset the unit using an appliance module e.g. prior to turning it on.

If you don't have HV then back t  the drawing board. If this and another
interface could be designed into the same unit then let me know and we'll
think about it.

Phil - have you taken off the panel or whatever yet (defeated the anti
tamper screws)?

Ian




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http://www.automatedhome.co.uk
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____________________________________
Automated Home UK
http://www.automatedhome.co.uk
____________________________________

Your use of Yahoo! Groups is subject t  http://docs.yahoo.com/info/terms/