RE: Electronics help with IR TX-RX

["Graham Howe" <graham@xxxxxxx>]

I have the Zener diode and resistor combination in place and that works
fine, what seems to be the problem is that the signal generated by this
(0.5V drop) is not interpreted properly by the transmitter unit when the
high voltage is applied. As I said the receiver bit seems to work OK (I can
see the voltage drop on the signal wire) but the signal does give rise to a
corresponding flashing of the LED (and IR LED) on the transmitter unit if
the higher voltage is involved.

Graham

-----Original Message-----
From: 	James Hoye [mailto:james.hoye@xxxxxxx]
Sent:	15 May 2001 20:45
To:	ukha_d@xxxxxxx
Subject:	RE: [ukha_d] Electronics help with IR TX-RX

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The TSOPs work at 5v and as such need some sort of regulation - either
using
a 39p voltage regulator from M***** or the combination of a 5.1v Zener
diode
and a resistor.  Ian B's PCBs utilise the Zener/resistor - I'm sure he can
provide you with the circuit details.

I have a couple of spare TSOPs, and I'm sure Keith has quite a few left.

James H

> -----Original Message-----
> From: Graham Howe [mailto:graham@xxxxxxx]
> Sent: Tuesday, May 15, 2001 7:20 PM
> To: UKHA List (E-mail)
> Subject: [ukha_d] Electronics help with IR TX-RX
>
>
> As many of you know, I eventually managed to put together some working
IR
> transmitters and receivers with help from several on the list and
> despite my
> non-existent electronics knowledge. However I now have a problem, the
kit
> works fine when I use a 12V battery and connect both TX and RX to it
(with
> an additional wire between them for the signal). I am currently in the
> process of installing Comfort and so drilled a little hole in one of
the
> PIRs and inserted an IR RX unit. I connected the 12V and 0V from
> the PIR to
> the unit and used a spare wire in the CAT5 cable for the signal. Then
I
> connected up the TX unit via Krone blocks and patch panel and it
didn't
> work. After I finished cursing myself for not testing the set up
before
> gluing the RX inside the PIR I started to investigate. After much
probing
> with a voltmeter, I discovered that the 12V output from Comfort
> was actually
> 13.8V and that when fed with this voltage the kit wouldn't work,
> in fact the
> TS1308 (is that the right code? If not it is the things Keith was
selling)
> seemed to die after a while at this voltage (I now have 2 dead
> ones). I then
> tried having just the RX unit fed by Comfort and the TX fed by
> the battery,
> this didn't work either, even though I could see the 0.5V drop in the
> trigger wire when IR was received. At this point I started thinking
that I
> was well and truly out of my depth, so I started guessing what might
be
> wrong. Here are my thoughts:
>
> The RX unit will operate correctly for at least a limited time when
> connected to the 13.8V, the trigger wire shows 5V which drops to 4.5V
when
> IR is received.
>
> The TX unit does not appear to like the higher voltage at all and
> certainly
> doesn't react correctly to the trigger when the higher voltage is
applied
> (could it be that the 0.5V drop is no longer sufficient to do the
'magic'.
>
> Both a RX and a TX unit appear to have been killed during my
experiments,
> possibly as a result of the high voltage.
>
> It seems I have two options, either use an alternative power
> supply that is
> closer to 12V and therefore put up with less convenient wiring inside
my
> PIRs. Or use some sort of electronic trickery (possibly a resistor?)
to
> reduce the voltage supplied from Comfort (after all the Comfort
> outputs are
> labeled 12V).
>
> Please can one of you electronic geniuses give me some advice,
> with the DDAR
> price increase this is turning out to be a very unsuccessful day!
>
> Graham
>
>
>
>
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>
>
>




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