Re: After IR beam break info

[ian.bird@xxxxxxx]

Hi Justin

As far as I know the following is good advice (but I stand to be=20
corrected)

There is a lot or IR pollution outside in particular from the sun but most=
=20
of the time from other sources too. Assuming you only want to detect a=20
beam being broken you will need a very directional IR transmitter, a=20
receiver that ideally can be built into a tube which will provide some=20
form of protection from stray IR etc. and a modulated beam so you can tell=
=20
the difference between stray IR and the stuff from your transmitter.

I think the Maplin units will do most of this at a tenner but I cannot=20
vouch for the range. If you are building your own then you will need to=20
send the modulated signal and detect and check it at the receiver. I would=
=20
guess your current experiment is running into problems with the strength=20
of the output from the photo diode as over a range this will be rather=20
small.

Drop me a line if you want the circuit diagram for the Maplin units as
it=20
on the back of the pack for the units and I have one at home.

See ya

Ian

p.s. if you still have that Xantech IR receiver I can now solder the=20
transistors that were on it - you know, the tiny black three legged things=
=20
that melted on us.







"Justin" <justin@xxxxxxx>
10/10/2003 15:07
Please respond to ukha_d

=20
To:     "UKHA" <ukha_d@xxxxxxx>
cc:=20
Subject:        [ukha_d] After IR beam break info


I wonder if anyone can help...

I would like to build a beam break with an outdoor range of approx 5M.=20
I've
been experimenting with a SFH309 Phototransistor and a pronto but have=20
only
been able to get a range of 6" or so (indoors). I know the Pronto has
good
range, so the problem must be with the receiver, but I don't know what
to=20
do
about it!
A LOT of Googling has led me nowhere, so short of buying an off the shelf
solution, I'm a bit stuck!

Any links, advice?

Cheers,
Justin.



UKHA 2004: 15th and 16th May 2004

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