Re: Hmevision ir transmitter

["andy_powell_is" <ukha@xxxxxxx>]

Dave,

as I understand it:

There are 2 separate power supplies for the circuit, the +5v supplied 
by homevision from it's IR port and the +5v for the led driver. The 
first transistor was designed to trigger the second thus minimal 
current would be drawn from homevision primarily because in the end I 
could be driving up to 72 leds (8 visible light and 64 IR ones)

The circuit represents 1/8 of the entire circuit. I've been told that 
it's more likely that for the LED driver I'll need a meaty 12v supply 
rather than 5v... (I'm assuming I can use %v LEDs with 12V by using a 
resistance of around 5k, dropping the current to 24mA, is that 
correct?)

Andy

BTW if anyone is getting annoyed at this I'm happy to take it off 
list...





--- In ukha_d@y..., "Dave McLaughlin" <dave@v...>
wrote:
> 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@b...>
> To: <ukha_d@y...>
> 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@b...>
> > To: <ukha_d@y...>
> > 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
> > > Unsubscribe:  ukha_d-unsubscribe@xxxxxxx
> > > List owner:  ukha_d-owner@xxxxxxx
> > >
> > > Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
> > >
> > >
> >
> >
> >
> > For more information: http://www.automatedhome.co.uk
> > Post message: ukha_d@xxxxxxx
> > Subscribe:  ukha_d-subscribe@xxxxxxx
> > Unsubscribe:  ukha_d-unsubscribe@xxxxxxx
> > List owner:  ukha_d-owner@xxxxxxx
> >
> > Your use of Yahoo! Groups is subject to 
http://docs.yahoo.com/info/terms/
> >
> >
> >



For more information: http://www.automatedhome.co.uk
Post message: ukha_d@xxxxxxx 
Subscribe:  ukha_d-subscribe@xxxxxxx 
Unsubscribe:  ukha_d-unsubscribe@xxxxxxx 
List owner:  ukha_d-owner@xxxxxxx

Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.