Re: Re: Hmevision ir transmitter

["Dave McLaughlin" <dave@xxxxxxx>]

So am I right in saying that the output from HV goes to +5V when switched
ON
and virtual GND when off?

If this is the case, then removal of the left hand transistor in Andy's
drawing and connecting the base of the right one via a 1K resistor will
work.

I have actually done a circuit and simulated it for the OPEN COLLECTOR
type
of output when the output goes to ground if that also helps.

Dave...

----- Original Message -----
From: "Frank Mc Alinden" <armagh@xxxxxxx>
To: <ukha_d@xxxxxxx>
Sent: Friday, May 31, 2002 2:06 PM
Subject: Re: [ukha_d] Re: Hmevision ir transmitter


> Andy
>         I think we are both
getting confused . When i spoke about open
> collector i was refering to Port A of HomeVision not the IR TX signal
.
> Anyway had a look at the manual . The output is driven by a PNP
transistor
> with emitter connected to +5v and the collector connected to the front
ir
> led via a resistor and also from cllector to the jack. Ignore the
comments
> about ground switching ,Homevision will be switching approx +5v.
DONT
> CONNECT AT THIS STAGE YOUR CIRCUIT TO HOMEVISION.........Until you got
it
> 100%.
>
> Frank Mc
>
> ps if i get my prototype to work and its what your after i will
make
another
> (veroboard only)and sent it to you.....
> ----- Original Message -----
> From: "andy_powell_is" <ukha@xxxxxxx>
> To: <ukha_d@xxxxxxx>
> Sent: Friday, May 31, 2002 10:49 PM
> Subject: [ukha_d] Re: Hmevision ir transmitter
>
>
> > --- In ukha_d@y..., "Frank Mc Alinden"
<armagh@b...> wrote:
> > > Andy
> > >         The best
person to explain these things is off list at the
> > moment
> > > K.D.
> >
> > Yes, I know, it pains em that he's working hard on the KAT5 box
:P
> >
> > >You are using the transistor basically as a switch,
> > > switching it on and off rapidly to mimic the ir signal.
> >
> > Yep, I think I get that part...
> >
> > > The ground signal i think you are referring to is supplied
by the
> > open
> > > collector output of HomeVision .When someone refers to
open
> > collector it
> > > means that the collector is connected to ground when the
ouput is
> > active.
> >
> > This is the bit I'm unsure about, from what you are saying I
/guess/
> > that what you are telling me is that the IR jack on the back
isn't
> > pulsing 5v it's making a connection to ground, ie pulsing a
circuit
> > in that normally the ir jack isn't grounded when ir is sent
the
> > ground is connected and unconnected very quickly to create the
IR
> > pulses.
> >
> > My problem is understanding that if the diagram I did before
> > (http://groups.yahoo.com/group/ukha_d/files/Transistor.bmp) 
is
> > correct then the transistor would never pass any current because
in
> > order for HV to send a pulse it must have the ground, but as soon
as
> > the ground is made on the base of the transistor there is no
current,
> > and thus the transistor wont pass the current... or have I lost
the
> > plot entirely?
> >
> >
> > > Andy  hope this makes sense also i hope to teach
myself  Visual
> > Basic as i
> > > want to learn a high level language so i will have lots of
question
> > s to ask
> > > you programmer gurus
> >
> > No problems here Frank, I'll be happy to help where I can..
> >
> > Andy
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > For more information: http://www.automatedhome.co.uk
> > Post message: ukha_d@xxxxxxx
> > Subscribe:  ukha_d-subscribe@xxxxxxx
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> >
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> >
> >
>
>
>
> For more information: http://www.automatedhome.co.uk
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