Re: Re: Hmevision ir transmitter

["Dave McLaughlin" <dave@xxxxxxx>]

Hi Andy

Your circuit won't work as it is.

Remove the left hand transistor in your drawing and connect the output
from
HV via a 1K resistor to the base of the right hand one.

Also connect a 4K7 resistor (or 10K) from the HV output to +5V. This
makes
the output go to +5v when the HV output is off.

This means the signal is inverted.

I'll knock up a drawing this afternoon if I get time for a correct
circuit
which does invert.

Dave...

----- Original Message -----
From: "andy_powell_is" <ukha@xxxxxxx>
To: <ukha_d@xxxxxxx>
Sent: Friday, May 31, 2002 1:49 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
>
>
>
>
>
>
>
>
>
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