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Topic: IR frequency (Read 2 times) previous topic - next topic

TweakGeek

This might be a super noob question, but I can't seem to figure it out and I'm up against a deadline.  I'm working on a project for school where I'm making like a shooting gallery type project.  The "bullet" will be the IR beam and the "target" will be the IR receiver.  I've looked at IR LEDs and the receivers.  The receivers receive specific frequencies, but the IR LEDs only show the wavelengths.  How can I be certain that I match the correct LED with the receivers?  Is the frequency controlled by the board the LED is attached to?

Please help me........ :~

DuaneB

look up 38khz 555 timer or 38khz Arduino

Duane B
Read this
http://rcarduino.blogspot.com/2012/04/servo-problems-with-arduino-part-1.html
then watch this
http://rcarduino.blogspot.com/2012/04/servo-problems-part-2-demonstration.html

Rcarduino.blogspot.com

TweakGeek

Thanks!  I'm looking it up now.  I'm fairly new to the world of electronics so figuring out what to use and with what is fairly difficult for me to understand right now.  I don't have any books I'm learning from either so the internet is my only guide.  Hopefully I'll learn it the right way.

I just ordered a Teensy board (http://www.pjrc.com/store/teensy.html) which uses the ATMEGA32U4 processor.  I will be researching this more, but are you familiar with this board or know if I can use it to set the frequency of the IR?  I don't need a long extended answer at this point, but if you know it can or can't be done then it could save me some research time.

Thanks so much for your help!

floresta

Quote
The receivers receive specific frequencies, but the IR LEDs only show the wavelengths.

The wavelength that you are referring to above is that of the light being emitted by the LED.

The frequency that you are referring to above is the rate at which the LED is being turned on and off.

So you wind up with an LED that is being turned on and off at a high frequency.  During the time that it is on it emits light at a certain wavelength.


Don

AWOL

...and don't try to relate the modulation frequency measured in kHz, with the actual frequency of the light measured in THz.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

Docedison

Yeah cuz thats a lot of numbers... What I think is that the OP needs to pulse the LED and detect it on another device... Kinda simple If you leave out the IR Remote control device... Just IMO needs a transmitter and a receiver, could have a lot of transmitters and one receiver... just detect the different "tones {pulses} or Id's from each transmitter... "Point and Shoot..." Forget the IR receiver from Radio Shack and it's equivalents... Not good for what he describes... what I read in his description is a simple IR detector (Photo-transistor) looking for IR input (IR led controlled by something (Uno or Equivalent))

Doc
--> WA7EMS <--
"The solution of every problem is another problem." -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard

TweakGeek


What I think is that the OP needs to pulse the LED and detect it on another device...


Doc, that is exactly what I need.  I just need to "shoot" a brief pulse to be detected at the other end.  I'm not sending actual 'directions' like different buttons on a remote or such.  This is just a very simple application.

Quote

Forget the IR receiver from Radio Shack and it's equivalents... Not good for what he describes... what I read in his description is a simple IR detector (Photo-transistor) looking for IR input (IR led controlled by something (Uno or Equivalent))


I was wondering if a photo-transistor would be better for my application.  I don't know all of the uses for these items so I'm not real sure.  I just figured that an IR receiver would be best for detecting the IR beam.

pekkaa

Quote
I was wondering if a photo-transistor would be better for my application.


It won't be. You really need a "real" IR detector which detects 38kHz modulated IR signal. If you just try to detect an IR beam with a photo-transistor it would be very difficult to distinguish the ambient IR (for example, sunlight) from the actual beam you want to detect.

TweakGeek

That does make sense to me and I wondered about that.

Thanks a bunch!

dkl65

http://www.arcfn.com/2009/08/multi-protocol-infrared-remote-library.html would be a great library to send modulated IR signals!
Visit http://www.glenof.webs.com/!

Grumpy_Mike

#10
Jun 20, 2012, 11:04 pm Last Edit: Jun 20, 2012, 11:15 pm by Grumpy_Mike Reason: 1
Quote
I was wondering if a photo-transistor would be better for my application.

Also a proper detector has a built in amplifier and can easily achieve the range of 6 to 10ft. Where as you need a lot of extra circuit to do that with a photo transistor.
You need the TSOP4038, all the others have limits on the number of pulses it can receive.

Docedison

I tried to suggest a simple method. Please take a look at it again. The data could very well be RS232 Data... to another Arduino???

Quote
What I think is that the OP needs to pulse the LED and detect it on another device... Kinda simple If you leave out the IR Remote control device... Just IMO needs a transmitter and a receiver, could have a lot of transmitters and one receiver... just detect the different "tones {pulses} or Id's from each transmitter... "Point and Shoot..." Forget the IR receiver from Radio Shack and it's equivalents... Not good for what he describes... what I read in his description is a simple IR detector (Photo-transistor) looking for IR input (IR led controlled by something (Uno or Equivalent))


This is a quote from an earlier post of mine. The OP made no mention of a "Modulated IR Beam"  
This is the relevant part... Only
Quote
I'm working on a project for school where I'm making like a shooting gallery type project.  The "bullet" will be the IR beam and the "target" will be the IR receiver.

Quote
What I think is that the OP needs to pulse the LED and detect it on another device... Kinda simple If you leave out the IR Remote control device... Just IMO needs a transmitter and a receiver, could have a lot of transmitters and one receiver... just detect the different "tones {pulses} or Id's from each transmitter... "Point and Shoot...

The object of Any project First Must be to apply the KISS method and try to find the simplest solution to the problem "Shooting Gallery could very well be using a port  on an Arduino to directly pulse (PWM) an IR LED and use a photo detector to "receive" the (PWM)Pulsed Beam...If there were more than one "Shooter"... use another PWM duty cycle... Simple, or did you intend to emulate an IR remote control transmitter and receiver on two Arduino's...
You Could. Adafruit sells a device that transmits only the "OFF" code for every tv code known. You could use that and a photo... what a waste...    IMO

Doc
--> WA7EMS <--
"The solution of every problem is another problem." -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard

Grumpy_Mike

Did a shooting gallery game back in November 92,
http://www.doc.mmu.ac.uk/STAFF/A.Wiseman/Acorn/BodyBuild/BB92.html
However that was "shooting" at a CRT computer display, a sort of long range light pen.

Quote
The OP made no mention of a "Modulated IR Beam" 

Not directly but he was talking of:-
Quote
The receivers receive specific frequencies

And that means a modulated beam.

pekkaa

#13
Jun 20, 2012, 11:21 pm Last Edit: Jun 20, 2012, 11:24 pm by pekkaa Reason: 1
You will need the Arduino to detect hits in the targets and to keep the score, but you probably don't want/need to use the Arduino in the guns. As DuaneB suggested, use 555 timer to generate 38kHz frequency. If you need to distinguish several guns from each other, use second 555 the generate payload signal which is different for each gun (say 1000Hz for one gun and 800Hz for an other).

TweakGeek



The object of Any project First Must be to apply the KISS method and try to find the simplest solution to the problem "Shooting Gallery could very well be using a port  on an Arduino to directly pulse (PWM) an IR LED and use a photo detector to "receive" the (PWM)Pulsed Beam...If there were more than one "Shooter"... use another PWM duty cycle... Simple, or did you intend to emulate an IR remote control transmitter and receiver on two Arduino's...
You Could. Adafruit sells a device that transmits only the "OFF" code for every tv code known. You could use that and a photo... what a waste...    IMO

Doc


Doc,  I value your opinion, but you are talking over my knowledge level (not your problem, it's mine).  I will need the range of the IR to be somewhere in the neighborhood of 30-50+ feet.  I agree that I want to apply the KISS method.  I was intending on just wiring up an IR LED to the switch and sending the signal (after focusing the IR beam etc but I didn't want to explain all that), but then got concerned about the frequency of the IR receiver. 

I only have 1 Arduino board at the moment.  I have access to another, but I don't want to have to mess with fitting the board into the gun if I don't have to.

I might need to use the 555 timer to generate the frequency.  Luckily, at this point, I will only be using 1 gun so I won't need to worry about detecting different frequencies.

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