Login Join Maker Pro

# Need help on very basic stuff

M

#### [email protected]

Jan 1, 1970
0
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

L

#### Lord Garth

Jan 1, 1970
0
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.

M

#### [email protected]

Jan 1, 1970
0
Thank you, this is great stuff. I already bought one of those ir
receivers at said store, but I will need a 555 now to get the emitter
to pulse.

About input voltage... I noticed that my amp readings came out right,
but I always had more voltage than I expected. Should I build this:
http://www.eidusa.com/Electronics_Voltage_Regulator.htm

instead? Also, on the receiver side, I would like to use the power of
the rs232 serial interface and send a signal to that very special pin.

This is exciting. Another one: Why does using 20kOhm before the
detector work better than using about (9-5)/0.05=80?

Thanks for the help and the resources. I am currently checking out
National Semiconductor.

C

#### Chris

Jan 1, 1970
0
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

How do, Manoo. Since you're at Radio Shack already, wander over to the
counter and ask about the Electronic Sensor Lab, Catalog #: 28-278

M

#### [email protected]

Jan 1, 1970
0
Thank you, Chris and Rich. I noticed that even though I had some
classes on the topic back in College, I didn't retain the slightest bit
of practical knowledge about the topic. Therefore, you can imagine how
thrilled I was when my visible LED would actually turn on and off when
I put my finger through the beam.

Since I actually AM in a hurry, (and I like experimenting better than
http://www.robotroom.com/Infrared555.html

If I can make my Voltage lower to +5V DC steady, (with an LM7805),
can't I just build above circuit and voila? Or what major problems
would I face?

And on the other end, I use the (276-640) 38kHz IR Receiver Module from
Radio Shack, possibly in combination with another LM7805 for voltage
regulation and maybe a transistor (as switch) for supplying the result
to the rs232 pin? Or can I use the power of the rs232 directly? I
remember having seen circuits on the topic, but I think there is some
danger involved.

The electronics kit sounds like a good idea, but on the other hand, you
know how many parts I can burn out for 50 bucks?

Thank you all again for your help. I'll keep you posted about my
progress, if that's ok...
Manoo.

C

#### Chris

Jan 1, 1970
0
Thank you, Chris and Rich. I noticed that even though I had some
classes on the topic back in College, I didn't retain the slightest bit
of practical knowledge about the topic. Therefore, you can imagine how
thrilled I was when my visible LED would actually turn on and off when
I put my finger through the beam.

Since I actually AM in a hurry, (and I like experimenting better than
http://www.robotroom.com/Infrared555.html

If I can make my Voltage lower to +5V DC steady, (with an LM7805),
can't I just build above circuit and voila? Or what major problems
would I face?

And on the other end, I use the (276-640) 38kHz IR Receiver Module from
Radio Shack, possibly in combination with another LM7805 for voltage
regulation and maybe a transistor (as switch) for supplying the result
to the rs232 pin? Or can I use the power of the rs232 directly? I
remember having seen circuits on the topic, but I think there is some
danger involved.

The electronics kit sounds like a good idea, but on the other hand, you
know how many parts I can burn out for 50 bucks?

Thank you all again for your help. I'll keep you posted about my
progress, if that's ok...
Manoo.

The circuit in the link looks like it would do the job for the emitter.
There aren't any docs on the RS detector (usually they just have
connections to Vcc and GND, with the third pin as output which may
require a pullup resistor). There should be a basic hookup diagram on
the back of the package. Line up your LED and detector, then start
pulling the detector away until the signal just disappears, tweak the
pot until the signal comes back on, then stretch it some more. Repeat
until you can't get a signal. That should be the appropriate tuned
frequency for the detector.

Good luck
Chris

J

#### Jasen Betts

Jan 1, 1970
0
The circuit in the link looks like it would do the job for the emitter.
There aren't any docs on the RS detector (usually they just have
connections to Vcc and GND, with the third pin as output which may
require a pullup resistor). There should be a basic hookup diagram on
the back of the package. Line up your LED and detector, then start
pulling the detector away until the signal just disappears, tweak the
pot until the signal comes back on, then stretch it some more. Repeat
until you can't get a signal. That should be the appropriate tuned
frequency for the detector.

38Khz Crystals are easily had, what sort of circuit would be needed to use
one of them?

Bye.
Jasen

M

#### [email protected]

Jan 1, 1970
0
Ok. I am still not sure I am doing it right, but it seems to work. I
have a configuration where I use a 555 timer in astable mode, cranking
its frequency to what I hope is somewhere between 38 and 40 kHz. On the
other side, I have the Rat Shack IR receiver and a couple of
transistors and resistors and when I wave my hand between the two, my
LED on the receiver lights up.

I noticed, that it mainly picks up on a signal change, rather than the
emitter itsself, that's why I liked someone's suggestion (forgot who it
was) to use a second 555 timer to turn the emitter circuit on and off
in a range of about 1 to 10 khZ.

Getting that LED to light up tho, tells me its time to move on to the
next problem: How do I get that flash to translate to a signal to the
serial interface on my computer? (rs232). The wiring should be real
easy, but I can't find a simple circuit out there on the internet.

Does anyone have a good resource?
Thank you
Manuel

M

#### [email protected]

Jan 1, 1970
0
I actually did it! Thank you for your contributions all.

I built a sender emitting IR at good-know-what frequency (with a 555
astable)
and a 38kHz receiver from radio-shack that responds to my hand moving
at a certain minimal speed through the beam. The signal on the output
goes into the receive-pin on the rs232, the handshake is looped-back
and
ground goes to exactly there.

When running a port diagnostics program, I receive a '0' when my hand
breaks the beam.

end
up having to set an interrupt trap, but from here on out, I feel much
more
comfortable.

Thanks again
Manuel

Replies
3
Views
872
Replies
3
Views
888
Replies
2
Views
669
Replies
51
Views
4K
N
Replies
7
Views
1K
Mark Fergerson
M