hi,
i'm doing a little experience with infrared emission,reception modulation
etc

eventough my system(very primitive) works fine indoor it is not the same
outdoor,it looks that the sfh250 Ir receiving diode when exposed to the weak
winter sun of northern Italy is able to generate about
-400 mV on a 1MOhm load

What is it due to? and how can i avoid it if possible?Shielding?Red glass
filtering or what ??Thank you

Diego
Italy

On Feb 15, 6:47 am, "blisca" <bliscachiocciolinatiscali.it> wrote:
hi,
i'm doing a little experience with infrared emission,reception
modulation
etc

eventough my system(very primitive) works fine indoor it is not the same
outdoor,it looks that the sfh250 Ir receiving diode when exposed to the
weak
winter sun of northern Italy is able to generate about
-400 mV on a 1MOhm load

What is it due to? and how can i avoid it if possible?Shielding?Red
glass
filtering or what ??Thank you

Diego
Italy

Photodiodes produce current. Resistors create voltage drop
proportional to current. The usual remedies:

1) reduce load resistance, which also reduces sensitivity, of course
2) apply reverse bias voltage, which may require capacitive coupling
if the amplifier circuit is sensitive to DC level
3) use a transconductance amplifier, which can be configured to keep
voltage across the photodiode near zero volts

Paul Mathews

Paul Mathews <o...@whidbey.com> wrote in message

1171551554.380692.274...@q2g2000cwa.googlegroups.com...





On Feb 15, 6:47 am, "blisca" <bliscachiocciolinatiscali.it> wrote:
hi,
i'm doing a little experience with infrared emission,reception
modulation
etc

eventough my system(very primitive) works fine indoor it is not the same
outdoor,it looks that the sfh250 Ir receiving diode when exposed to the
weak
winter sun of northern Italy is able to generate about
-400 mV on a 1MOhm load

What is it due to? and how can i avoid it if possible?Shielding?Red
glass
filtering or what ??Thank you

Diego
Italy

Photodiodes produce current. Resistors create voltage drop
proportional to current. The usual remedies:

1) reduce load resistance, which also reduces sensitivity, of course
2) apply reverse bias voltage, which may require capacitive coupling
if the amplifier circuit is sensitive to DC level
3) use a transconductance amplifier, which can be configured to keep
voltage across the photodiode near zero volts

Paul Mathews

thank you,very much,at first

in the past days i used a TSOP1736,integrating filters ,demodulation and so
on

his feature should be high immunity to environmental light,but while exposed
to the sun passing fast the hand and shadowing it quickly seems enough to
turn it's output active

strange,not?



- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

On Feb 15, 7:16 am, "blisca" <bliscachiocciolinatiscali.it> wrote:
Paul Mathews <o...@whidbey.com> wrote in message

1171551554.380692.274...@q2g2000cwa.googlegroups.com...





On Feb 15, 6:47 am, "blisca" <bliscachiocciolinatiscali.it> wrote:
hi,
i'm doing a little experience with infrared emission,reception
modulation
etc

eventough my system(very primitive) works fine indoor it is not the same
outdoor,it looks that the sfh250 Ir receiving diode when exposed to the
weak
winter sun of northern Italy is able to generate about
-400 mV on a 1MOhm load

What is it due to? and how can i avoid it if possible?Shielding?Red
glass
filtering or what ??Thank you

Diego
Italy

Photodiodes produce current. Resistors create voltage drop
proportional to current. The usual remedies:

1) reduce load resistance, which also reduces sensitivity, of course
2) apply reverse bias voltage, which may require capacitive coupling
if the amplifier circuit is sensitive to DC level
3) use a transconductance amplifier, which can be configured to keep
voltage across the photodiode near zero volts

Paul Mathews

thank you,very much,at first

in the past days i used a TSOP1736,integrating filters ,demodulation and so
on

his feature should be high immunity to environmental light,but while exposed
to the sun passing fast the hand and shadowing it quickly seems enough to
turn it's output active

strange,not?



- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

Integrated IR photodetectors such as TSOP1736 usually include an
optical filter that reduces effects of ambient light. However, they
are not really designed to operate in daylight, since most people
don't watch TV in daylight. Typically, their field of view is reduced
by some type of aperture or tube placed in front of the photodetector.
IR remote controls emit intense beams, and the 'commands' are
repeated, with the user re-aiming the remote, until the desired
results are achieved. You can use and aperture, tube, or lens to
narrow the field of view.
Paul Mathews

In article <1171561655.710689.92...@l53g2000cwa.googlegroups.com>,
"Paul Mathews" <o...@whidbey.com> wrote:



On Feb 15, 7:16 am, "blisca" <bliscachiocciolinatiscali.it> wrote:
Paul Mathews <o...@whidbey.com> wrote in message

1171551554.380692.274...@q2g2000cwa.googlegroups.com...

On Feb 15, 6:47 am, "blisca" <bliscachiocciolinatiscali.it> wrote:
hi,
i'm doing a little experience with infrared emission,reception
modulation
etc

eventough my system(very primitive) works fine indoor it is not the same
outdoor,it looks that the sfh250 Ir receiving diode when exposed to the
weak
winter sun of northern Italy is able to generate about
-400 mV on a 1MOhm load

What is it due to? and how can i avoid it if possible?Shielding?Red
glass
filtering or what ??Thank you

Diego
Italy

Photodiodes produce current. Resistors create voltage drop
proportional to current. The usual remedies:

1) reduce load resistance, which also reduces sensitivity, of course
2) apply reverse bias voltage, which may require capacitive coupling
if the amplifier circuit is sensitive to DC level
3) use a transconductance amplifier, which can be configured to keep
voltage across the photodiode near zero volts

Paul Mathews

thank you,very much,at first

in the past days i used a TSOP1736,integrating filters ,demodulation and so
on

his feature should be high immunity to environmental light,but while exposed
to the sun passing fast the hand and shadowing it quickly seems enough to
turn it's output active

strange,not?

- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

Integrated IR photodetectors such as TSOP1736 usually include an
optical filter that reduces effects of ambient light. However, they
are not really designed to operate in daylight, since most people
don't watch TV in daylight. Typically, their field of view is reduced
by some type of aperture or tube placed in front of the photodetector.
IR remote controls emit intense beams, and the 'commands' are
repeated, with the user re-aiming the remote, until the desired
results are achieved. You can use and aperture, tube, or lens to
narrow the field of view.
Paul Mathews

Use two photodiodes. Aim one at your source, the other someplace else
neutral. Use a differential input and subtract one from the other.

Al

On Feb 15, 4:06 pm, Al <no.s...@wanted.com> wrote:
In article <1171561655.710689.92...@l53g2000cwa.googlegroups.com>,
"Paul Mathews" <o...@whidbey.com> wrote:



On Feb 15, 7:16 am, "blisca" <bliscachiocciolinatiscali.it> wrote:
Paul Mathews <o...@whidbey.com> wrote in message

1171551554.380692.274...@q2g2000cwa.googlegroups.com...

On Feb 15, 6:47 am, "blisca" <bliscachiocciolinatiscali.it> wrote:
hi,
i'm doing a little experience with infrared emission,reception
modulation
etc

eventough my system(very primitive) works fine indoor it is not
the same
outdoor,it looks that the sfh250 Ir receiving diode when exposed
to the
weak
winter sun of northern Italy is able to generate about
-400 mV on a 1MOhm load

What is it due to? and how can i avoid it if
possible?Shielding?Red
glass
filtering or what ??Thank you

Diego
Italy

Photodiodes produce current. Resistors create voltage drop
proportional to current. The usual remedies:

1) reduce load resistance, which also reduces sensitivity, of
course
2) apply reverse bias voltage, which may require capacitive
coupling
if the amplifier circuit is sensitive to DC level
3) use a transconductance amplifier, which can be configured to
keep
voltage across the photodiode near zero volts

Paul Mathews

thank you,very much,at first

in the past days i used a TSOP1736,integrating filters
,demodulation and so
on

his feature should be high immunity to environmental light,but while
exposed
to the sun passing fast the hand and shadowing it quickly seems
enough to
turn it's output active

strange,not?

- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

Integrated IR photodetectors such as TSOP1736 usually include an
optical filter that reduces effects of ambient light. However, they
are not really designed to operate in daylight, since most people
don't watch TV in daylight. Typically, their field of view is reduced
by some type of aperture or tube placed in front of the photodetector.
IR remote controls emit intense beams, and the 'commands' are
repeated, with the user re-aiming the remote, until the desired
results are achieved. You can use and aperture, tube, or lens to
narrow the field of view.
Paul Mathews

Use two photodiodes. Aim one at your source, the other someplace else
neutral. Use a differential input and subtract one from the other.

Al

What will also work, and be simpler, is to wire the two photodiodes
together, in parallel but with opposite polarity. (cathode of one to
the anode of the other, and vice versa).

That way, the two should act as a single differential current source,
requiring just a single amplifier or current-to-voltage converter.

My coworkers and I used such a configuration years ago for a laser
spectroscopy measurement.

Mark

Every time lot of things hint and ideas from the NG,thank you sincerely

hi,
i'm doing a little experience with infrared emission,reception modulation
etc

eventough my system(very primitive) works fine indoor it is not the same
outdoor,it looks that the sfh250 Ir receiving diode when exposed to the weak
winter sun of northern Italy is able to generate about
-400 mV on a 1MOhm load

What is it due to? and how can i avoid it if possible?Shielding?Red glass
filtering or what ??Thank you

Diego
Italy