Finding the kHz of an IR detector?

Nitrohawk

Being a big DIY'er I enjoy scourging through broken or defunct electronic equipment in order to get my components. I am in the process of gathering parts for an IR experiment in range detection. My intended application is very similar to that of the Boe.
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I noticed that the old PC mice (the ones with the balls) used an IR set up for the X and Y coordinates. My donor mouse also had a scroll wheel that had a slightly different IR set up.
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I have had little to no luck finding a data sheet based on the numbers stamped on the components.

I was wondering if there was a loop of some sort I could set up my BS2 to span the different kHz? Or, maybe even a common testing method using my DMM to find the order of the leads?

I understand it depends on the signal from the IR LED and each IR Detector is tuned to a certan kHz, right?
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As a reference, I have begun researching with Parallax's document:
http://www.parallax.com/dl/docs/prod/audiovis/IRdecodeDetectAppnote.zip

The linked zip file was found here:
http://www.parallax.com/detail.asp?product_id=350-00014

Ideas or suggestions?



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Nitrohawk

Jonathan

Nitro,

One way might be to make a 555 circuit and use it to drive an IR LED. With a pot you can vary the output of the 555 and watch the output of the reciver, perhaps by putting an LED on the data lead. When you hit the right frequency hte output should change. Find the range, then assume that the proper frequemcy is somewhere in the middle of the range.

However, I'm not sure that the IR stuff from a mouse will work like the typically used IR remote module. To find the order of the leads, hook the mouse up to a PC and use a DMM. You can also figure that out by looking at the PCB and seeing what goes where, usually.

Jonathan

Nice to see another scrounger... I really like using "previously enjoyed" parts and keeping 'em out of the landfill.

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www.madlabs.info - Home of the Hydrogen Fuel Cell Robot

LoopyByteloose

Scrounging parts is quite a challenge.
You may have gotten something that is similar, but not useful
[noparse][[/noparse]I got a bag of bandpass filters that look just like resonators]

First of all there are really TWO general types of IR sensors.

The mouse has a paired LED and a two wire sensor that is NOT frequency specific. These are a photo-transistor and count the on/off cycles of a slotted wheel. This is something like a light beam that tells you when someone walks into a 7/11. When the beam is broken, an electrical pulse is sent. In some cases, they can be used to follow a line, but both the led and the sensor must point in the same direction.

The kind of IR sensors that recieve transmited digital information usually have three wires and are quite different as they have more complex circuitry to both receive and filter digital information that is modulated by a 38KH to 40KH carrier. The idea here is to have a narrow band of IR that will not pick up IR from your desk lamp, a hot cup of coffee, and so on.

If you are not comfortable with understanding all the concepts of Modulation, Carrier Frequency, and Filtering -- these things originated from radio. The Parallax textbooks include one on the whole subject of IR communications. That would be a great place to begin to start.

Having said that,
if you have the right sensor you can adjust the optimal distance by trial and error in software. You just change the Modulated output frequency of your tranmitting BasicStamp until you get the best fit in terms of distance and reliablity. You can start at 38KH, then go to 40KH, then go to 39KH. After making observations of where the best fit is in that range, {let's say below 39KH], you try 38KH, then 38.5KH, and then 40KH to find a tighter fit -- and so on until you are satisfied.

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"When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)

······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

Bruce Bates

Nitrohawk -

I fear you'll have to look somewhere else for an I/R transmission facilty for range detection, unless the range you're intending to investigate in in the centimeter range. The I/R devices inside a computer mouse are used for encoding purposes, and this need to be quite close together for proper operation.

To answer your question about matching, yes they should be matched both in wavelength, and by their modulation frequency. Only a transmitter and reciever which are matched will give satisfactory results.

The I/R equipment found in laptops or hand-held devices used for IrDA may work, but I'd hate to see you hacking those parts, ruining an otherwise useful device, when for a few dollars you can get exactly what you need, either from Parallax or elsewhere.

For l-o-n-g distance I/R applications, you may want to look into using the I/R trnasmitters and recievers found here onthe Rentron web site:
http://www.rentron.com/PicBasic/RemoteControl.htm

Just ask my friend Bruce Reynolds (owner of that web site) which I/R units he might suggest for long distance ranging. The other alternative is to obtain these Parallax parts as follows:

I/R transmitter - http://www.parallax.com/detail.asp?product_id=350-00017

I/R reciever - http://www.parallax.com/detail.asp?product_id=350-00014

For less than $10.00 US you're good to go, and almost any documentation regarding use or application of I/R transmitters and I/R recievers on the Parallax web site can also be used to guide you. If you go with scavenged parts, you'll be pretty much on your own.

Regards,

Bruce Bates