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'[EE]: IR problem'
2002\05\04@080535 by hasan volkan guducu

picon face
hi all, i am working on a IR transmitter receiver design and using
sharp IS1U60 receiver. But i cant detect transmitter signals 50 cm.
far from the receiver. i try to amplify current with opamp but i does
not do any good. what shall i do?

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2002\05\04@092906 by Jinx

face picon face
An IS1U60 puts out data or 5V - trying to amplify signals
will do you no good

Sounds like you need more power in the transmitter. The
examples here work for many metres. You can shield the
receiver from ambient light by putting a shroud around it,
although that will limit the coverage angle. Never needed
to put them in a metal box as VCR & TV types are

http://home.clear.net.nz/pages/joecolquitt/txless.html

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2002\05\04@092921 by Lyle Hazelwood

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face
The Sharp IS1U60 requires that the IR Emitter is modulated at (or near)
38Khz.
Also, the datasheet shows a Minimum pulse width of 400us, and a maximum
pulse length of 800us.

Try watching the output while aiming a TV remote control at the unit.
If you see a bunch of pulses on the ISU160 Output, it's working fine.

You cannot just turn on an IR Emitter, it must be modulated at about 36 to
40Khz.
Also, you can't just run a constant stream of 36-40 KHz. The output must be
in
"bursts" of about 600us in duration.

The above numbers come from the Sharp datasheet.

Good Luck,
Lyle Hazelwood
spam_OUTmotoman9TakeThisOuTspambellsouth.net

{Original Message removed}

2002\05\04@093405 by Russell McMahon

face
flavicon
face
> hi all, i am working on a IR transmitter receiver design and using
> sharp IS1U60 receiver. But i cant detect transmitter signals 50 cm.
> far from the receiver. i try to amplify current with opamp but i does
> not do any good. what shall i do?

These devices are very simple to use when properly connected and when
supplied with a modulated 38 kHz IR signal.

What are you using as a "transmitter"
For starters try using a TV IR controller.
These send a signal at, typically, 38 kHz and modulate it with a data stream
with bit times around 1 mS.
The IS1U60 is a 38 kHz receiver.

If you can't see a signal from something like that then you are probably
doing something wrong.

Check whether you have the right connections.
Looking into the lense side with leads downwards the connections are

       Output / Ground   V+

Check that V+ is under 6 volts and preferably 5 volts.

Are you sending a modulated 38 kHz beam which you have generated?
If so this MUST be modulated with slower speed digital data - the units WILL
NOT WORK with a steady IR beam modulated at 38 kHz with no imposed data
stream. ie they don't work for a  steady "DC:" beam.

Datasheet at

       http://www.hvwtech.com/dnload/datasheets/is1u60.pdf



           Russell McMahon

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2002\05\04@133228 by uter van ooijen & floortje hanneman

picon face
> hi all, i am working on a IR transmitter receiver design and using
> sharp IS1U60 receiver. But i cant detect transmitter signals 50 cm.
> far from the receiver. i try to amplify current with opamp but i does
> not do any good. what shall i do?

give some details:
- which code/encoding etc are you using
- which send diode
- what is the (peak) current through the diode

and which current are you trying to amplify with an opamp??

Wouter van Ooijen
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2002\05\04@180229 by Peter L. Peres

picon face
Use a carrier matched to the detector's band. You are not using a carrier
now probably. LED current should be 1A or so when on (for a low duty
cycle). You may have to use a small filter (dark red plastic) on the
detector to avoid ambient light problems.

Peter

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2002\05\04@215939 by Russell McMahon

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flavicon
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> Use a carrier matched to the detector's band. You are not using a carrier
> now probably. LED current should be 1A or so when on (for a low duty
> cycle). You may have to use a small filter (dark red plastic) on the
> detector to avoid ambient light problems.


I played with similar designs just recently.
While the centre frequency is indeed 38 kHz as stated they are quite
forgiving and you will get SOME output at eg 35 or even 33 kHz. Spectral
frequency of the IR is also not absolutely critical and most IR LEDS will
work.

As Peter says, BEST results will be achieved with very high LED currents but
these are by no means necessary for quite impressive ranges. It is a very
good idea to start off using a standard TV or similar IR remote and see if
you get ANY output from the receiver using that as the transmitter. If you
don't then you need to check your receiver before you start trying to make
it work with your own transmitter. While an oscilloscope is quite useful  to
see what is happening you can get a good indication with an analogue meter
on the receiver output or even by using it to drive a visible LED.
eg 1k resistor from V+ to LED to output. LED lights on activation. Using an
IR remote control the LED will flicker while receiving a data signal.

ONCE you have got the receiver working with a working remote control AND NOT
BEFORE then try your own transmitter. Note that you will not get any output
if you send a steady 38 kHz signal. You MUST modulate the 38 kHz signal with
a "data signal". This could be as simple as turning it on and off at about a
1 kHz rate.

From a 5v supply with a driver transistor and a 50% modulated signal you
should get very useable results with a 100 ohm resistor in series with the
LED. LED current drain if always on would be about (5-1.2)/100 = 38 mA. At
50% duty cycle it will be half that.

TV sty;e IR remotes typically draw from about 5 to 30 mA average when on.
They typically run from 3 volts with only a few ohms in series with the
LEDS. Most of the battery voltage is dropped across the LED and driver
transistor but peak currents will be several hundred milliamps. The 38 kHz
drive data runs at from 50% to 30% duty cycle  (ie not necessarily a 50/50
square wave) and the data bursts are about 50% on and then the data bursts
can have longish gaps between each burst - say 1 unit on and 5 off. The
overall result is to make the average current smaller than peak current by
around 1/3 x 1/2 x 1/6 = 1/36 of peak. With a LED rated at say 50 mA average
continuous max this allows approaching 50 x 36 = 1800 mA peak !
Peak currents around 1 A are not unknown as Peter says. YMMV and you have to
design with some care when approaching this limit. The data sheet will
usually spec a peak current of around 1A. Distances of 5m are easily
achieved without pushing this limit and with peak currents of around 300 mA
I can get around 12 metre operating range. (Still less than an enthusiastic
IR remote control!).

Note that the trick of making the 38 kHz drive asymmetric can be
counterproductive as the receiver sensitivity will decrease away from a 50%
on / 50% off setting.



.                  Russell McMahon

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2002\05\04@215939 by Russell McMahon

face
flavicon
face
> Use a carrier matched to the detector's band. You are not using a carrier
> now probably. LED current should be 1A or so when on (for a low duty
> cycle). You may have to use a small filter (dark red plastic) on the
> detector to avoid ambient light problems.


I played with similar designs just recently.
While the centre frequency is indeed 38 kHz as stated they are quite
forgiving and you will get SOME output at eg 35 or even 33 kHz. Spectral
frequency of the IR is also not absolutely critical and most IR LEDS will
work.

As Peter says, BEST results will be achieved with very high LED currents but
these are by no means necessary for quite impressive ranges. It is a very
good idea to start off using a standard TV or similar IR remote and see if
you get ANY output from the receiver using that as the transmitter. If you
don't then you need to check your receiver before you start trying to make
it work with your own transmitter. While an oscilloscope is quite useful  to
see what is happening you can get a good indication with an analogue meter
on the receiver output or even by using it to drive a visible LED.
eg 1k resistor from V+ to LED to output. LED lights on activation. Using an
IR remote control the LED will flicker while receiving a data signal.

ONCE you have got the receiver working with a working remote control AND NOT
BEFORE then try your own transmitter. Note that you will not get any output
if you send a steady 38 kHz signal. You MUST modulate the 38 kHz signal with
a "data signal". This could be as simple as turning it on and off at about a
1 kHz rate.

From a 5v supply with a driver transistor and a 50% modulated signal you
should get very useable results with a 100 ohm resistor in series with the
LED. LED current drain if always on would be about (5-1.2)/100 = 38 mA. At
50% duty cycle it will be half that.

TV sty;e IR remotes typically draw from about 5 to 30 mA average when on.
They typically run from 3 volts with only a few ohms in series with the
LEDS. Most of the battery voltage is dropped across the LED and driver
transistor but peak currents will be several hundred milliamps. The 38 kHz
drive data runs at from 50% to 30% duty cycle  (ie not necessarily a 50/50
square wave) and the data bursts are about 50% on and then the data bursts
can have longish gaps between each burst - say 1 unit on and 5 off. The
overall result is to make the average current smaller than peak current by
around 1/3 x 1/2 x 1/6 = 1/36 of peak. With a LED rated at say 50 mA average
continuous max this allows approaching 50 x 36 = 1800 mA peak !
Peak currents around 1 A are not unknown as Peter says. YMMV and you have to
design with some care when approaching this limit. The data sheet will
usually spec a peak current of around 1A. Distances of 5m are easily
achieved without pushing this limit and with peak currents of around 300 mA
I can get around 12 metre operating range. (Still less than an enthusiastic
IR remote control!).

Note that the trick of making the 38 kHz drive asymmetric can be
counterproductive as the receiver sensitivity will decrease away from a 50%
on / 50% off setting.



.                  Russell McMahon

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