would this work?
http://www.epanorama.net/documents/ir/irremote.html

"Fritz Schlunder" wrote in message
...

"Fred" wrote in message
.. .

"Johan Wagener" wrote in message
...
I built the circuit as shown on
http://www.mitedu.freeserve.co.uk/Ci...face/irext.htm.

I could not get hold of the photodiodes they used in this circuit.

I used the following components available from
http://www.fort777.co.za/

Infra red emitter:

Peak wavelength: 940nm
Forward voltage at IF = 20mA: 1.6V
Forward current max.: 100mA
Power dissipation: 100mW
Radiated angle: 30°

Receiver photodiode:

High sensitivity infrared photodiode in side-looking TO92 package.
Black (infrared transparent) epoxy resin package.
Light current typically 75uA at 1000 lux.
Matching transmitter LIR151.
The cathode is the short lead.
ecifications

Peak wavelength: 900nm
Open circuit voltage: 0.35V
Acceptance angle: 120°

The receiving part of my circuit seems to work (led flashes when
remote
is
used) I can't seem to get the emitting part to work. The units
(tv,hi-fi,
ect) simply does nothing even when the diode is placed right in front
of
its
IR.

I can's seem to find the datasheet for the SFH2030 used in the circuit

Please help



I assume LED0 is the IR transmitting IR LED. I suspected it may have
flashed at least the once bearing in mind that you have a 27R series
resistor and a power supply of 12V. This would give a current of
3-400mA,
3
to 4 times rated current.


Infrared LEDs are often rated for a maximum of 100mA continuous forward DC
current. If the circuit is working properly like it should, then the
signal
detected from the remote will be a roughly 38kHz 50% duty cycle squarewave
carrier frequency light signal that is further modulated by the data at
likely less than 50% duty cycle (of the 38kHz carrier) at some frequency
well below the carrier. Usually IR remotes will AM modulate the 38kHz
carrier at some frequency so slow as to be very easily human detectable as
flickering.

So the effective duty cycle the LED should see is likely less than 25%,
but
certainly well less than 50%. So even though the 27 ohm resistor limits
the
current to something like 3-400mA, when multiplied by the effective duty
cycle the average current through the LED will likely be somewhat less
than
100mA. If the circuit is operating properly, the LED will not be
significantly abused...

Unfortunately this circuit is very poorly designed in many respects. The
circuit has novel simplicity, but pays for it in functionality/reliability
and performance.

If the ambient lighting conditions are too high, the circuit will
constantly
detect that and turn the output stage on full blast at 100% duty cycle
(plain DC). Thus there certainly exists a real possibility the IR LED
could
be damaged by excessive current.

The other really serious problem is the circuit doesn't really try very
hard
to keep the incomming and outgoing duty cycles the same. This is probably
why the OP's implementation isn't working. While some IR receiver
circuits
might have lax input filters that will respond acceptably to a distorted
IR
signal, the OP's IR receiver probably doesn't like the distortion that
likely will be added by the circuit. As a result is balks and doesn't
work.

A better designed IR repeater would do something more like this:

An infrared 38kHz receiver IC (such as the Panansonic PNA4602M from
Digikey)
should first detect the remote control signal. Since the output of the
receiver IC will be demodulated data, we will need to remodulate the data
onto a new 38kHz carrier. Since the output of the Panasonic is an open
collector output with internal pull up resistor, the output is inverted
from
the sent signal. We will need to invert the output signal to get it
looking
right again.

A 38kHz 50% duty cycle (fairly high precision, +/-1kHz will likely start
reducing functionality) oscillator will be needed. The oscillator output
should be ANDed with the output of the inverted IR receiver IC output.
The
final output should be buffered by a fast switching small MOSFET such as
the
BSS138 to drive the LED at pulse currents of up to around 400mA (or
perhaps
more if you can insure the average current is less than 100mA). Using
bipolar junction transistors isn't necessarily a good idea for this stage
since they can have fairly long storage times which will distort the
signal.
At 38kHz and reasonable drive currents the effect may be minimal, but to
be
safe it is easier to just use a MOSFET. Make sure the range extender LED
is
not pointed such that any significant amount of IR light will fall on the
detector, otherwise signal feedback will occur and the system will
probably
self oscillate.

Even when going to all this trouble the range extender may still not work
since the Panasonic PNA4602M or similar IR receiver IC may distort the
signal enough to cause problems in some cases. In these instances
probably
the easiest solution to increasing range is to modify the remote control
itself. Replace the IR LED with one that is more efficient (such as the
Vishay TSAL6100 from Mouser), or use multiple LEDs in parallel (make sure
to
pump up the driver power to drive them properly).

To give an idea of what is possible, using six paralleled TSAL6400 LEDs
pulsed at 1A peak currents and a Vishay TSOP1256 receiver IC I was able to
achieve outdoors (at night) data transmission at distances of up to an
estimated 70 meters. Even more range is surely possible with shorter beam
angle LEDs (or more LEDs) and perhaps some other circuit tweaks/improved
optics.