Trouble understand IR specification - Electronic Circuits Projects Diagrams Free

timothyjackson · 15th January 2007, 08:32 PM

Dear all:

I'm having a little trouble understanding something

For an IR (IR TX and RX) can someone explain what the following is

Frequency Range (Mhz) = ?
stripe (line) width (Khz) = ?
Modulation Type

many many thanks - tj

dknguyen · 15th January 2007, 08:41 PM

Frequency range would be the frequency of IR light (ie. the wavelength of light) that a RX is sensitive to. For a TX, this is the range of wavelengths it will emit. Neither RX or TX are perfect so they can't emit, or be sensitive to just a single wavelength of light- it's a small band around a center frequency.

Not sure what stripe width is...sounds familliar. It's a width, but you say the units are in kHz?

Modulation is similar to the RX and TX being switched on and off synchronously at a high frequency. That means the RX is only trying to detect light when the TX is sending light. This makes false triggers less likely to happen (like ambient light can sometimes cause a false trigger).

**Nigel Goodwin** · 15th January 2007, 10:50 PM

I suggest you give more details of what you're trying to do?, so far you're making no sense?.

Sceadwian · 16th January 2007, 12:35 AM

I did a little bit of searching on google and everything I'm finding with a refrence to line width is for infrared spectroscopy. I'm not sure how the receivers work but basically the line width is the sub band of the IR spectrum the specimen absorbs.

timothyjackson · 18th January 2007, 11:26 AM

OK - definatley helping.

Maybe by strip, i mean beam? - Beam width, does that ring any bells (i guess some "measurablity" of how big the IR beam is (thats being transmitted)

Modulation - I understand PWM, yet, what are the types of Modulation - are there different/generic ways to modulate. I.e. if i asked someone to modulate an ir tx and rx with XX(?) modulation?

thanks tj

**Nigel Goodwin** · 18th January 2007, 11:47 AM

Still not really making any sense - why not explain what you're wanting to do?.

timothyjackson · 19th January 2007, 02:10 PM

aiming to understand 2 things

1 - If IR can be technically specified according to the following factors:

stripe (line) width (Khz) = ?
Modulation Type

&

2 - Exactly what they mean

**Nigel Goodwin** · 19th January 2007, 02:21 PM

Still makes no sense - IR is just a certain part of the spectrum, do YOU understand your question if it's altered to read:

Quote:

1 - If BLUE can be technically specified according to the following factors:

stripe (line) width (Khz) = ?
Modulation Type

&

2 - Exactly what they mean

Sceadwian · 19th January 2007, 11:24 PM

LED's IR or otherwise don't send out only one frequency, they send out a thin band around a central frequency, the stripe width is basically the cuttoff above or bellow or center of the primary frequency.

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15th January 2007, 08:32 PM	(permalink)
timothyjackson	Trouble understand IR specification Dear all: I'm having a little trouble understanding something For an IR (IR TX and RX) can someone explain what the following is Frequency Range (Mhz) = ? stripe (line) width (Khz) = ? Modulation Type many many thanks - tj

15th January 2007, 08:41 PM	(permalink)
dknguyen	Frequency range would be the frequency of IR light (ie. the wavelength of light) that a RX is sensitive to. For a TX, this is the range of wavelengths it will emit. Neither RX or TX are perfect so they can't emit, or be sensitive to just a single wavelength of light- it's a small band around a center frequency. Not sure what stripe width is...sounds familliar. It's a width, but you say the units are in kHz? Modulation is similar to the RX and TX being switched on and off synchronously at a high frequency. That means the RX is only trying to detect light when the TX is sending light. This makes false triggers less likely to happen (like ambient light can sometimes cause a false trigger).

15th January 2007, 10:50 PM	(permalink)
Nigel Goodwin	I suggest you give more details of what you're trying to do?, so far you're making no sense?. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

16th January 2007, 12:35 AM	(permalink)
Sceadwian	I did a little bit of searching on google and everything I'm finding with a refrence to line width is for infrared spectroscopy. I'm not sure how the receivers work but basically the line width is the sub band of the IR spectrum the specimen absorbs. __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har."

18th January 2007, 11:26 AM	(permalink)
timothyjackson	OK - definatley helping. Maybe by strip, i mean beam? - Beam width, does that ring any bells (i guess some "measurablity" of how big the IR beam is (thats being transmitted) Modulation - I understand PWM, yet, what are the types of Modulation - are there different/generic ways to modulate. I.e. if i asked someone to modulate an ir tx and rx with XX(?) modulation? thanks tj

18th January 2007, 11:47 AM	(permalink)
Nigel Goodwin	Still not really making any sense - why not explain what you're wanting to do?. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

19th January 2007, 02:10 PM	(permalink)
timothyjackson	aiming to understand 2 things 1 - If IR can be technically specified according to the following factors: stripe (line) width (Khz) = ? Modulation Type & 2 - Exactly what they mean

19th January 2007, 11:24 PM	(permalink)
Sceadwian	LED's IR or otherwise don't send out only one frequency, they send out a thin band around a central frequency, the stripe width is basically the cuttoff above or bellow or center of the primary frequency. __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har."