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

[Nigel Orr <nigel@xxxxxxx>]

At 13:03 30/10/00 +0000, you wrote:
>http://www.mitedu.freeserve.co.uk/Circuits/Interface/irext.htm
and  I have
>to admit that the latter looks much simpler than Nigel's version.

It is simpler, in terms of component count and probably cost.  I've not
built it, but I'd expect the one I suggested would be significantly more
reliable.

The mitedu one doesn't demodulate the IR signal, and I wouldn't expect it
to cope well with high or varying ambient light (and particuarly in the
presence of fluorescents or compact fluorescents), I would expect that it
would generate more spurious noise from the transmitter which might reduce
the range of other remotes that you are using.  That's not due to any
cleverness on my part, just that the IR receivers I use seem to cope well
with extremes of light.

All that said, I don't have any particular interest in you building mine,
so feel free to go for either one!  In particular, if you're doing it
today, you might find the TSOP or Sharp devices hard to find.  The circuit
on the website is my IR transmitter.  You also need 1 receiver for each
room where you want to go with the remote.  That's the TSOP or Sharp
devices, they contain everything (IR photodiode, demodulator etc) but do
need a 5V supply.

A zener diode- based thing would suffice- if James Hoye is reading, maybe
he can share the secrets of his success, I can't easily find the emails I
sent with resistor value suggestions etc...

>normal seating position). So all I really want to know is what to buy,
how
>to build it and is this really feasible for a complete novice ?

Not sure, it should be OK.  At complete novice level, I'd suggest you buy a
little plugboard as well, which makes soldering faults less likely, and
gives you the chance to test it and correct mistakes without commiting
yourself.  M****n do a little white one, around 40 rows of contacts with
separate power rails, or at least used to... it's probably been replaced
with a larger range of mobile phone vouchers by now :-)

>If anyone has any advice or suggestions (other than go and do an
electronics
>course !) then please respond.

Take your time, and don't forget to add a connection from pin 8 of the
timer to +12V (must update the schematic some time!).  If possible, get
hold of a camcorder or cctv camera for testing- they are sensitive to IR so
you can get some idea of what is going on, assuming you have no
oscilloscope.

Check, double check and triple check before you switch it on.  Buy a cheap
multimeter if you don't already have one (even an analogue one will
probably be fine, but digital might save you reading resistor colour
codes!), and check the voltages before you plug in the 555 timer.  If you
solder it together, put the timer chip in a socket.

That's probably enough to get started!

Nigel


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