Ir Sensor and Transmitter Help
Brian Smith
Posts: 44
Hopefully this will be really simple.
I want to use an infrared sensor as an input on my bs2. The 350-00014 ·senses infrared light flashing at 38 kHz. How can I make a light flash at this rate? I need something thats not contralled by a bs2 . I want to·see a signal every time my bs2 passes the stand alone transmitter. Also how do I know how great of a·distance this sensor will work (how big of an·infrared light (or array)·do I need for say 10 feet)?
·
I want to use an infrared sensor as an input on my bs2. The 350-00014 ·senses infrared light flashing at 38 kHz. How can I make a light flash at this rate? I need something thats not contralled by a bs2 . I want to·see a signal every time my bs2 passes the stand alone transmitter. Also how do I know how great of a·distance this sensor will work (how big of an·infrared light (or array)·do I need for say 10 feet)?
·
Comments
You can use an inexpensive 555 timer for generating the modulation frequency you require.
10 feet should be no problem, as far as distance, is concerned, with almost any method.
The intensity of the I/R light is almost directly proportional to how "hard" you drive the I/R LED, meaning how much amperage you push through it. The more current (not too much in excess of the rated current) the more light will be produced. The more light that is produced, the further the usable distance. You can usually drive them over the stated maximum milliamp rating, if need be, since the use is not continuous, and most maximum rating ARE based on continuous use.
Exceptionally long distances can be achieved by using some of the more advanced circuits and infrared transmitters found here:
http://www.rentron.com/Fire-Stick-II.htm
Shorter distances can be achieved as noted above. Another thought to possibly keep in mind is that you may want to send a (say 4-bit) CODE along with the IR transmission to identify WHICH beacon is sending the signal, presuming there are multiple beacons involved in this system. There are solutions for that as well in the Remote Control Section of the RENTRON site noted above.
Regards,
Bruce Bates
Thats the 555 manual im looking at.·Im not really sure what I need to do with this circuit. Do I need monostable or astable opperation?·I·assume I use the output for the positive power supply of mt IR transmitter and Vdd for negative.
Post Edited (Brian Smith) : 11/4/2005 7:16:42 PM GMT
73
spence
k4kep
Just how critical is that 38KHz frequency you're trying to achieve - can you tolerate
a little drift?
See page 3 top center graph
http://www.parallax.com/dl/docs/prod/audiovis/PNA4601M.pdf
Will astable just go from .67 to .33 volts (never 0V)?·If so, will that work?
Post Edited (Brian Smith) : 11/4/2005 7:19:30 PM GMT
portion of the circuit to minimize drift. Given your frequency tolerance range,
you shouldn't have any problem attaining a good degree of stability
with these types of components.
Not sure about the lower level output voltage...I'll have to check the
datasheets, and unfortunately I don't have ready access to such at
the moment.
This is an oscillator with many output frequencies
and rock solid 40khz output
I made mistakes when drawing the tif version
you can see what frequencies each pin will output using resonators you have
or calculate the resonator frequency needed for your desired output.