A
AK
Guest
What specifically do these terms mean for a LDR?
Resistance (Dark): 1MâŚ
Resistance (Light): 12kâŚ
Resistance (Dark): 1MâŚ
Resistance (Light): 12kâŚ
A
AK
Guest
On Monday, May 13, 2019 at 7:18:43 PM UTC-5, AK wrote:
I forgot to state that it is Cadmium Sulfide (CdS) Photocell.
Features:
Maximum voltage rating @ 25°C: 350VDC
Maximum allowable power dissipation @ 25°C: 400mW
Resistance (Dark): 1MâŚ
Resistance (Light): 12kâŚ
Lead length: 1.44"
Operating temperature: -30°C to +70°C
Able to withstand soldering at 230°C for 3 seconds
I forgot to state that it is Cadmium Sulfide (CdS) Photocell.
Features:
Maximum voltage rating @ 25°C: 350VDC
Maximum allowable power dissipation @ 25°C: 400mW
Resistance (Dark): 1MâŚ
Resistance (Light): 12kâŚ
Lead length: 1.44"
Operating temperature: -30°C to +70°C
Able to withstand soldering at 230°C for 3 seconds
L
Look165
Guest
Dark= no light
Light = >= 10 or 100lux
AK a ĂŠcrit le 14/05/2019 Ă 02:18Â :
Light = >= 10 or 100lux
AK a ĂŠcrit le 14/05/2019 Ă 02:18Â :
D
default
Guest
On Mon, 13 May 2019 17:29:07 -0700 (PDT), AK
<scientist77017@gmail.com> wrote:
Light dependent resistors change resistance with light. 1,000,000
ohms when dark 12,000 ohms when light shines on it. (but those are
just nominal values)
<scientist77017@gmail.com> wrote:
Light dependent resistors change resistance with light. 1,000,000
ohms when dark 12,000 ohms when light shines on it. (but those are
just nominal values)
A
AK
Guest
On Monday, May 13, 2019 at 7:18:43 PM UTC-5, AK wrote:
I am trying to get my laser alarm working.
No luck so far.
I am wondering if the cadmium photo cell may be the problem?
Maybe I need an LDR that responds to light quicker.
Andy
I am trying to get my laser alarm working.
No luck so far.
I am wondering if the cadmium photo cell may be the problem?
Maybe I need an LDR that responds to light quicker.
Andy
W
Wolf Bagger
Guest
On 2019-05-14 05:25, AK wrote:
They're not slow. Do you have a meter to measure the resistance while
you illuminate it with your laser? It may not be interested in that
wavelength of light.
They're not slow. Do you have a meter to measure the resistance while
you illuminate it with your laser? It may not be interested in that
wavelength of light.
P
Phil Hobbs
Guest
On 5/15/19 12:37 AM, Wolf Bagger wrote:
Yeah, they're slow. Not seconds, but dramatically slower and less
well-behaved than photodiodes or even phototransistors.
Using a CdS or CdSe cell is very rarely the right answer. If you
modulate the light source and detect the AC at the other end with a
photodiode, transimpedance amp, and synchronous detector, you can easily
make an 'electric eye' that works fine in direct sunlight.
Cheers
Phil Hobbs
Yeah, they're slow. Not seconds, but dramatically slower and less
well-behaved than photodiodes or even phototransistors.
Using a CdS or CdSe cell is very rarely the right answer. If you
modulate the light source and detect the AC at the other end with a
photodiode, transimpedance amp, and synchronous detector, you can easily
make an 'electric eye' that works fine in direct sunlight.
Cheers
Phil Hobbs
L
Look165
Guest
A LDR reacts in some ms when the light's wavelength is in the operating
range.
Phil Hobbs a ĂŠcrit le 15/05/2019 Ă 07:49Â :
range.
Phil Hobbs a ĂŠcrit le 15/05/2019 Ă 07:49Â :
C
Cursitor Doom
Guest
On Wed, 15 May 2019 11:15:18 +0200, Look165 wrote:
You really can't beat a photodiode, though.
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protocols constitutes acceptance of this condition.
You really can't beat a photodiode, though.
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the Usenet protocol. Reproduction in whole or part through other
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GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.
A
amdx
Guest
On 5/15/2019 9:46 AM, AK wrote:
Please put the resistance meter on your LDR and give use the resistance
Dark and then with laser light on it.
You will need to change the scale between the two measurements.
Mikek
Please put the resistance meter on your LDR and give use the resistance
Dark and then with laser light on it.
You will need to change the scale between the two measurements.
Mikek
A
AK
Guest
On Wednesday, May 15, 2019 at 9:30:43 AM UTC-5, Cursitor Doom wrote:
Does anyone know of an alarm circuit that they have made and works?
I have tried 2 different circuits and both have failed.
Andy
Does anyone know of an alarm circuit that they have made and works?
I have tried 2 different circuits and both have failed.
Andy
L
Look165
Guest
Yes, it can.
A photodiode takes time to turn on or off, about the same a LDR takes.
LDR are reversible, standard photodiodes are only one way.
Cursitor Doom a ĂŠcrit le 15/05/2019 Ă 16:30Â :
A photodiode takes time to turn on or off, about the same a LDR takes.
LDR are reversible, standard photodiodes are only one way.
Cursitor Doom a ĂŠcrit le 15/05/2019 Ă 16:30Â :
P
Phil Hobbs
Guest
On 5/15/19 1:14 PM, Look165 wrote:
A fast photodiode will respond in picoseconds. Even slow ones are in
the tens-of-nanosecond range if used with the right transimpedance amp.
They're also highly linear and stable, neither of which is true of CdS
cells.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
https://hobbs-eo.com
A fast photodiode will respond in picoseconds. Even slow ones are in
the tens-of-nanosecond range if used with the right transimpedance amp.
They're also highly linear and stable, neither of which is true of CdS
cells.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
https://hobbs-eo.com
L
Look165
Guest
For an alarm, do you care to 10ms for instance ?
Phil Hobbs a ĂŠcrit le 15/05/2019 Ă 19:20Â :
Phil Hobbs a ĂŠcrit le 15/05/2019 Ă 19:20Â :
A
AK
Guest
On Wednesday, May 15, 2019 at 9:59:26 AM UTC-5, amdx wrote:
In the dark, .83 on the 2M scale.
With laser, .3 on 2k scale. From a distance of 6 feet.
So, 830,000 and 300 ohms.
Andy
In the dark, .83 on the 2M scale.
With laser, .3 on 2k scale. From a distance of 6 feet.
So, 830,000 and 300 ohms.
Andy
P
Phil Hobbs
Guest
On 5/15/19 1:26 PM, Look165 wrote:
friends of mine.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
https://hobbs-eo.com
Of course not, but you gave Bad Info about photodiodes, who are sort of
friends of mine.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
https://hobbs-eo.com
L
Look165
Guest
A bad friend which act only in one way !
Phil Hobbs a ĂŠcrit le 15/05/2019 Ă 20:05Â :
Phil Hobbs a ĂŠcrit le 15/05/2019 Ă 20:05Â :
On 5/15/19 1:26 PM, Look165 wrote:
For an alarm, do you care to 10ms for instance ?
Phil Hobbs a ĂŠcrit le 15/05/2019 Ă 19:20Â :
On 5/15/19 1:14 PM, Look165 wrote:
Yes, it can.
A photodiode takes time to turn on or off, about the same a LDR takes.
LDR are reversible, standard photodiodes are only one way.
Cursitor Doom a ĂŠcrit le 15/05/2019 Ă 16:30Â :
On Wed, 15 May 2019 11:15:18 +0200, Look165 wrote:
A LDR reacts in some ms when the light's wavelength is in the
operating
range.
You really can't beat a photodiode, though.
A fast photodiode will respond in picoseconds. Even slow ones are in
the tens-of-nanosecond range if used with the right transimpedance amp.
They're also highly linear and stable, neither of which is true of CdS
cells.
Cheers
Phil Hobbs
Of course not, but you gave Bad Info about photodiodes, who are sort of
friends of mine.
Cheers
Phil Hobbs
D
default
Guest
On Wed, 15 May 2019 19:14:51 +0200, Look165 <look165@numericable.fr>
wrote:
photo transistors. To get the most speed out of diodes and photo
transistors it depends on current and biasing. Over-drive the piss
out of them and they slow down a bit.
But for his application, with an un modulated light source, a CDS
photocell is fast enough, especially with the 555 circuit he was
building where it is directly coupled to the 555. It should be able
to meander all over the place in it's own sweet time and still trigger
the alarm.
My gripe with CDS cells is their susceptibility to moisture. I live
in a humid climate and these things will go bad just sitting in a
parts drawer unless they are sealed in glass,
wrote:
Photo diodes are much much faster than CDS- LDR's. Even faster than
photo transistors. To get the most speed out of diodes and photo
transistors it depends on current and biasing. Over-drive the piss
out of them and they slow down a bit.
But for his application, with an un modulated light source, a CDS
photocell is fast enough, especially with the 555 circuit he was
building where it is directly coupled to the 555. It should be able
to meander all over the place in it's own sweet time and still trigger
the alarm.
My gripe with CDS cells is their susceptibility to moisture. I live
in a humid climate and these things will go bad just sitting in a
parts drawer unless they are sealed in glass,
D
default
Guest
On Wed, 15 May 2019 20:23:37 +0200, Look165 <look165@numericable.fr>
wrote:
>A bad friend which act only in one way !
No problem, stick two back to back.
When do you actually need bidirectional conduction? Audio or linear
applications maybe, that's about it, and he's just looking for on-off
control here.
wrote:
>A bad friend which act only in one way !
No problem, stick two back to back.
When do you actually need bidirectional conduction? Audio or linear
applications maybe, that's about it, and he's just looking for on-off
control here.
Phil Hobbs a écrit le 15/05/2019 ŕ 20:05 :
On 5/15/19 1:26 PM, Look165 wrote:
For an alarm, do you care to 10ms for instance ?
Phil Hobbs a écrit le 15/05/2019 ŕ 19:20 :
On 5/15/19 1:14 PM, Look165 wrote:
Yes, it can.
A photodiode takes time to turn on or off, about the same a LDR takes.
LDR are reversible, standard photodiodes are only one way.
Cursitor Doom a écrit le 15/05/2019 ŕ 16:30 :
On Wed, 15 May 2019 11:15:18 +0200, Look165 wrote:
A LDR reacts in some ms when the light's wavelength is in the
operating
range.
You really can't beat a photodiode, though.
A fast photodiode will respond in picoseconds. Even slow ones are in
the tens-of-nanosecond range if used with the right transimpedance amp.
They're also highly linear and stable, neither of which is true of CdS
cells.
Cheers
Phil Hobbs
Of course not, but you gave Bad Info about photodiodes, who are sort of
friends of mine.
Cheers
Phil Hobbs
L
Look165
Guest
A LDR doesn't need power to operate !
default a ĂŠcrit le 15/05/2019 Ă 20:34Â :
default a ĂŠcrit le 15/05/2019 Ă 20:34Â :
On Wed, 15 May 2019 20:23:37 +0200, Look165 <look165@numericable.fr
wrote:
A bad friend which act only in one way !
No problem, stick two back to back.
When do you actually need bidirectional conduction? Audio or linear
applications maybe, that's about it, and he's just looking for on-off
control here.
Phil Hobbs a ĂŠcrit le 15/05/2019 Ă 20:05Â :
On 5/15/19 1:26 PM, Look165 wrote:
For an alarm, do you care to 10ms for instance ?
Phil Hobbs a ĂŠcrit le 15/05/2019 Ă 19:20Â :
On 5/15/19 1:14 PM, Look165 wrote:
Yes, it can.
A photodiode takes time to turn on or off, about the same a LDR takes.
LDR are reversible, standard photodiodes are only one way.
Cursitor Doom a ĂŠcrit le 15/05/2019 Ă 16:30Â :
On Wed, 15 May 2019 11:15:18 +0200, Look165 wrote:
A LDR reacts in some ms when the light's wavelength is in the
operating
range.
You really can't beat a photodiode, though.
A fast photodiode will respond in picoseconds. Even slow ones are in
the tens-of-nanosecond range if used with the right transimpedance amp.
They're also highly linear and stable, neither of which is true of CdS
cells.
Cheers
Phil Hobbs
Of course not, but you gave Bad Info about photodiodes, who are sort of
friends of mine.
Cheers
Phil Hobbs