RE: Electronics help with IR TX-RX

["Ian B" <I.Bird@xxxxxxx>]

Congratulations on getting everything working again.

You can connect many receivers to one transmitter. I think about 4 have
been
tested and work. IR transmitters are a little different. You can connect
many to the board but not without some mods. This will keep the power to
them correct etc. If it is not too many leds though just connect them up. I
think it is in series but Keith would be the best person to check with. The
IR leds are currently wired as follows.

+12----IR LED----100ohm res----transistor----ground.

Ian

-----Original Message-----
From: Graham Howe [mailto:graham@xxxxxxx]
Sent: 16 May 2001 08:13
To: ukha_d@xxxxxxx
Subject: RE: [ukha_d] Electronics help with IR TX-RX


I don't know how I made it happen, but I did kill one 555 timer and one
TSOP, but replacing those two everything works fine. Thanks to Ian's
boards,
I think it would be unlikely for even a complete electronic novice like me
to make a mistake with the circuit. In fact the only real opportunity for
error would be connecting up the LEDs the wrong way round (something I
didn't do). It is certainly strange, maybe I just got unlucky with some
duff
components (though both did work initially) but everything is fine now. The
next question is how many receivers can I have feeding back to a single
transmitter, if it is possible to have more than one at all. Also how many
IR LEDs could I connect to a single transmitter, if they are mounted
directly on the equipment's IR window (or inside).

Graham

-----Original Message-----
From: 	Keith Doxey [mailto:ukha.diyha@xxxxxxx]
Sent:	16 May 2001 07:55
To:	ukha_d@xxxxxxx
Subject:	RE: [ukha_d] Electronics help with IR TX-RX

Hi Graham,

I dont have the receiver circuit to hand but the TX  should be fine on
13.8.

The 555 timer used in the receiver has a supply range of 5-15V

The receiver failure is also strange. The TSOP1838 has a supply rating or
3-6V but keep it to 5 for safety. If I remember the circuit correctly there
is a dropper resistor between the 12v supply and the +ve input of the TSOP.
There should also be a 5V1 Zener diode at the input of the TSOP to clamp
the
voltage to 5.1V.

It sounds as if you have made a mistake with the voltage dropper circuit
and
are running the TSOP above its rated voltage. It is probably struggling
with
12v and failing completely at 13.8.

Keith

BTW I do still have TSOP1838's at £1-50 each.

> -----Original Message-----
> From: Graham Howe [mailto:graham@xxxxxxx]
> Sent: 15 May 2001 19:20
> 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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