Re: Urgent - Time to kill, want to build IR Extender

["Graham Howe" <graham@xxxxxxx>]

I now have all components in place and I want to test it, but I have one
silly problem, how do I get 5V to the TSOP 1838. I am putting 12V to the
transmitter circuit no problem, but in the absence of ac 5V output from the
comfort system (not yet setup), can I convert 12V to 5V easily, or will
4.5V
be sufficient (three AA batteries in series).

Regards

Graham
----- Original Message -----
From: "Nigel Orr" <nigel@xxxxxxx>
To: <ukha_d@xxxxxxx>
Sent: Tuesday, October 31, 2000 11:17 AM
Subject: Re: [ukha_d] Urgent - Time to kill, want to build IR Extender


> At 11:12 31/10/00 +0000, you wrote:
> > > >Second, the LED's, I know that the shortest leg is the
cathode, does
that
> > > >mean the other leg is the one to connect to the +12V.
> > >
> > > Probably.  Some LEDs are the other way round, there's no
particularly
> > > common standard, if you can see inside, it looks a bit like
a wire
going
> > > into a 'cup'.  The 'cup' is usually the cathode (I think, I
usually
just
> > > test them with a battery!).
> > >
> >I was worried about blowing it if I did this and got it wrong, but
I will
> >now try tonight
>
> If you have a 9V battery with a 1k resistor in series, it's _very_
unlikely
> to blow up the diode if you connect it backwards, especially when it's
only
> for a second or two to find which is right.  If you leave out the
resistor,
> all bets are off, I've tried it...  you should be even safer with a 3V
> supply (2 AA batteries) as most diodes have a maximum reverse voltage
> around 5V.
>
> > > The only way to test before the receiver arrives is using an
oscilloscope,
> > > a multimeter with a frequency meter, or a camcorder/camera. 
If you
have
> > > any of those, let me know and I'll tell you what you can use
it for.
> > >
> >I do have a camcorder (Hi8) and a digital camera, please do send
> >instructions for testing with these.
>
> The camcorder is probably (almost certainly) sensitive to the IR from
the
> diode, so if you point it at the diode and it's connected right, it
should
> be visible on the video output.  The digital camera might work too,
but
> I've never tried one for IR.
>
> Once you build the circuit, put a 10k resistor between the input + pin
and
> +12V, the IR led shouldn't be lit.  If you now short out the input
(the
> junction between the 10k resistor and the 2.7k input resistor) to 0V,
the
> IR LED should come on.  It should also be possible to check that it's
> oscillating, not just stuck on.  Take the end of the 2k7 resistor that
is
> plugged into pin 3 of the chip, and plug it into +12V, the IR LED
should
> now appear brighter to the camera, as it's on constantly, not flashing
50%
> on 50% off at 38kHz.
>
> Don't forget to reconnect everything as it was before you try it for
> real!  When you point a remote at the receiver and press a button, you
> should see your remote's IR LED flash, and see your transmitter flash
at
> the same time (the flickering is usually visible when a signal is
being
passed)
>
>  > other question, I am planning to link the receiver(s) to the
transmitter
> >with CAT5 going through normal IDC connections. Should I avoid
using both
> >wires in a twisted pair or is this OK ?
>
> No, you should actually aim to use both wires in the same twisted
pair, as
> that should reduce radiated and received interference.  So you might
have
> one pair supplying +12V and 0V, and the other pair with 0V and IR
> data.  There are some situations where that could cause problems, but
> they're not very likely.
>
> After prototyping on plugboard, I've built my receiver up on soldered
> breadboard, with Krone PCB mount IDC terminals, but I've not tested
that
> one yet!
>
> Nigel
>
>
>
>
>
>


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