RE: SCART switching with Homevision

["Keith Doxey" <ukha@xxxxxxx>]

Hi Steve,

+12 will select a SCART and +5V will select widescreen mode on a compatable
TV.

To get Homevision to do the switching you need to use Port A

Wire a 1K resistor from a +12V supply to a pin of Port A, (open collector
output) and wire the Port A pin to pin 8 of the SCART, connect the 0V of
the
power supply to one of the ground pins on the SCART. When the Port A is low
it will short the SCART end of the resistor to ground and the TV will not
be
"grabbed" when Port A is high (open circuit) the 12V supply will
feed
through the resistor to the SCART and grab the TV.

If you want to be able to select widescreen mode as well you will need two
pins on Port A and a couple of diodes as well.

Poor attempt at a diagram follows

+12V ----- 1K Resistor ---------------SCART Pin 8
l
l
Port A pin


For the 12V/5V switching it is like this

+12V ----- 1K Resistor ------------Diode>-----
l                l
l                l
Port A pin 1         l-----SCART Pin8
l
+ 5V ----- 1K Resistor ------------Diode>-----l
l
l
Port A pin 2

The diodes prevent the two voltages being shorted by the other Port A pin,
it doesnt matter if both are output at the same time as the 12V will take
precendence and grab the TV in full screen mode.

Hope that makes sense :-)

Keith



-----Original Message-----
From: Steve Morgan [mailto:steve@xxxxxxx]
Sent: 04 February 2002 21:32
To: ukha_d@xxxxxxx
Subject: [ukha_d] SCART switching with Homevision


Anybody got any suggestions on how to use HV to automate the switching of
AV
inputs on my TV?

I would expect that by toggling the Function switching inputs, I could get
HV to select a SCART socket automatically. Anyone know what the electrical
characteristics of the Function switching pin (8) is and how best to
manipulate it. I'm thinking of making a SCART 'breakout box' that will
bring
out the function switching signals.

Cheers,
--
Smorgo (Steve Morgan)
2001 Deauville & 1986 V8 110
E-Mail address is spam trapped. Try using my nickname (above) at wormpurple
dot com



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