Re: Need help on very basic stuff


<mbaumann@xxxxxxxxx> wrote in message
news:1129425592.280771.270920@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Hi all
>
> I am really new to electronics and might have never joined, but I
> absolutely want to create this light barrier that I have seen done
> before, just not by me.
>
> I went out to radio-shack and with the help of the internet, was able
> to actually create a barrier that works with IR over a few inches.
>
> I am using all radio-shack parts, so here are my circuits:
>
> 9V 9v
> 10kR ---- 10kR
> ----100R---- GND ---collector
>
> EMITTER --- GND
> ----100R----
>
> I only have some Resistors,so I did what I could.
>
> The parts are:
> 100Ohm R = 271-152
> 10KOhn R = 271-1126
> IR emmiter and detector: 276-0142
>
> Now, whats the watt tolerance mean on these resistors, which ones
> should I use and HOW can i make this work over a few feet distance?
>
> Also, I would like to have 0Vs when barrier on, 5V when its broke.
> I am able to control an led with a transistor 2N3904 (276-2016), but I
> don't really understand that.
>
> Thank you for lowering yourself to my level.
> Manoo


There is a lot more to this when you go for distance. The beam should be
modulated so that the detector circuit can easily see the difference between
your beam and background radiation. This is most easily done with an LM555
integrated circuit operation in astable mode. A transmitter built around an
analog oscillator will likely drift so the receiver needs to track the
changes.
You can do that with an LM567 but you should know that designing the
circuit is not for a beginner. There needs to be more power for the
transmitter
and maybe a lens to focus the invisible beam at the receiver.

That being said, there are Ir receiver modules available, even at Rat Shack.
You will need to build your 555 transmitter circuit to operate near 40kHz
for the little detector to lock on. Don't forget the input voltage these
units
need, you will need to read on the use of the 78xx series of voltage
regulators.
The LM7805 is one very common device. Note its input voltage requirements
and its ability to dissipate the heat it will generate when operating.
Don't
worry, they are rugged / abuse tolerant and easy to use.

Have fun and enjoy the hobby. Most of the info you will need to read is
on the National Semiconductor (and many other) web site.


.

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