Forums

pin diode

Started by Unknown December 4, 2015
Hi, 

What is the difference between Light Detector Resistor and a pin diode? 

And which one is better to use for solar tracking purposes and why? For example 

LDR:

http://www.digikey.com/product-detail/en/PDV-P8104/PDV-P8104-ND/480611


PIN DIODE:

http://media.digikey.com/pdf/Data%20Sheets/Everlight%20PDFs/PD204-6C.pdf

mel

On Thu, 03 Dec 2015 20:59:21 -0800, walravenmelissa wrote:

> Hi, > > What is the difference between Light Detector Resistor and a pin diode?
PIN photodiode. In the photoresistor the CdS is a semiconductor that's more or less neutrally doped (I think); light striking it generates carriers (electron- hole pairs) that help it to conduct electricity. In the photodiode, it's a real live actual diode. Light striking it generates carriers that make it act like a diode in parallel with a current source. Depending on how you connect it, the diode will either generate a voltage that can be sensed or it will pass a current that can be sensed.
> And which one is better to use for solar tracking purposes and why? For > example > > LDR: > > http://www.digikey.com/product-detail/en/PDV-P8104/PDV-P8104-ND/480611 > > > PIN DIODE: > > http://media.digikey.com/pdf/Data%20Sheets/Everlight%20PDFs/PD204-6C.pdf
Six of one, half a dozen of the other. Cadmium is toxic; I'm not sure if that matters much at all in a CdS cell, but if the ROHS nazies ever come to your door you'd like to be clean. I'm more familiar with the care and feeding of photodiodes, so I'd probably use them (aren't they cheaper, too?). I'd probably use them in photovoltaic mode, because their voltage will be roughly logarithmic to illumination, meaning that the voltage difference between a pair of them will be fairly constant with illumination. (Come to think of it this won't matter much because if it's very cloudy the sun will appear to be defocused -- oh well, I'd use 'em in photovoltaic mode anyway). Why not just use an ephemeris and clockwork? That way your rig can always point at the sun regardless of whether it's behind the clouds, eclipsed, or gone out entirely. -- www.wescottdesign.com
On Thu, 3 Dec 2015 20:59:21 -0800 (PST), walravenmelissa@gmail.com
wrote:

>Hi, > >What is the difference between Light Detector Resistor and a pin diode? > >And which one is better to use for solar tracking purposes and why? For example > >LDR: > >http://www.digikey.com/product-detail/en/PDV-P8104/PDV-P8104-ND/480611 > > >PIN DIODE: > >http://media.digikey.com/pdf/Data%20Sheets/Everlight%20PDFs/PD204-6C.pdf > >mel
Solar tracking with light diodes is stone-age technology. SUN travels 15 degrees per hour and all you need is a small geared motor which makes a few turns every five minutes. A simple garden or household timer clock does that easily. The gear ratio has to be designed appropiately. End position switch sends it back to the morning position, like the windshield wipers in a car. Elevation to be corrected twice a year, or just leave it as is. No tracking, no calculations, not complicated control circuits. Your sun diodes will always point to the brightest spot in sky which may be a cloud in any direction. w.
 "Tim Wescott" <tim@seemywebsite.com> napisa&#322; w wiadomo&#347;ci 
news:dMqdnXV6w4lDqPzLnZ2dnUU7-SGdnZ2d@giganews.com...
> On Thu, 03 Dec 2015 20:59:21 -0800, walravenmelissa wrote: > >> Hi, >> >> What is the difference between Light Detector Resistor and a pin diode? > > PIN photodiode. > > In the photoresistor the CdS is a semiconductor that's more or less > neutrally doped (I think); light striking it generates carriers (electron- > hole pairs) that help it to conduct electricity.
Generated or induced? See: https://archive.org/stream/radiationlightil00steirich#page/14/mode/2up and: http://pvcdrom.pveducation.org/MANUFACT/FIRST.HTM "Edmond Becquerel appears to have been the first to demonstrate the photovoltaic effect (Becquerel, 1841a, , 1841b). Working in his father's laboratory as a nineteen year old, he generated electricity by illuminating an electrode with different types of light, including sunlight (see the figure below)." Steinmetz wrote that the radiation induce the charge to the antenna. Becquerel that the radiation generate the electricity (current) in the circuit. Who, when i for what invented the electron- hole pairs? S*
>
I was wondering that which option pin diode or LDR is better to track the s=
un. I meant which one has the better I do not know  how to say it has bette=
r light properties. Lets say that one LDR or pin diode is mounted on the ea=
st side and the other on the west side.  The motor will move until the diff=
erence between the two sensors becomes zero.=20

Lets say tracking algorithm is not an option.  which option you will go wit=
h?=20





On 12/04/2015 05:59 AM, walravenmelissa@gmail.com wrote:
> Hi, > > What is the difference between Light Detector Resistor and a pin diode? > > And which one is better to use for solar tracking purposes and why? For example > > LDR: > > http://www.digikey.com/product-detail/en/PDV-P8104/PDV-P8104-ND/480611 > > > PIN DIODE: > > http://media.digikey.com/pdf/Data%20Sheets/Everlight%20PDFs/PD204-6C.pdf > > mel >
I think the pin diodes are a bit faster than LDR. some people use LEDs... If neither speed nor sensitivity really matters for your application, just use what is cheapest...
They both are very cheap. That's true that my application is slow and does not require lots of sensitivity. 

But I am leaning towards pin diodes. You said that they are fast. How are they faster and sensitive than Light Detection resistor? Do pin diodes have better spectral properties than LDR. I have posted the link of the pin diodes in the OP. They are cheaper and how can I use them instead of LDRs?
On 12/04/2015 01:42 AM, Tim Wescott wrote:
> On Thu, 03 Dec 2015 20:59:21 -0800, walravenmelissa wrote: > >> Hi, >> >> What is the difference between Light Detector Resistor and a pin diode? > > PIN photodiode. > > In the photoresistor the CdS is a semiconductor that's more or less > neutrally doped (I think); light striking it generates carriers (electron- > hole pairs) that help it to conduct electricity. > > In the photodiode, it's a real live actual diode. Light striking it > generates carriers that make it act like a diode in parallel with a > current source. Depending on how you connect it, the diode will either > generate a voltage that can be sensed or it will pass a current that can > be sensed. > >> And which one is better to use for solar tracking purposes and why? For >> example >> >> LDR: >> >> http://www.digikey.com/product-detail/en/PDV-P8104/PDV-P8104-ND/480611 >> >> >> PIN DIODE: >> >> http://media.digikey.com/pdf/Data%20Sheets/Everlight%20PDFs/PD204-6C.pdf > > Six of one, half a dozen of the other. Cadmium is toxic; I'm not sure if > that matters much at all in a CdS cell, but if the ROHS nazies ever come > to your door you'd like to be clean. > > I'm more familiar with the care and feeding of photodiodes, so I'd > probably use them (aren't they cheaper, too?). I'd probably use them in > photovoltaic mode, because their voltage will be roughly logarithmic to > illumination, meaning that the voltage difference between a pair of them > will be fairly constant with illumination. (Come to think of it this > won't matter much because if it's very cloudy the sun will appear to be > defocused -- oh well, I'd use 'em in photovoltaic mode anyway). > > Why not just use an ephemeris and clockwork? That way your rig can > always point at the sun regardless of whether it's behind the clouds, > eclipsed, or gone out entirely. >
Hmm. I wonder if Melissa has ever met erica.cross? Maybe in the mirror? Cheers Phil Hobbs
On Friday, December 4, 2015 at 4:53:21 AM UTC-8, walrave...@gmail.com wrote:

[about CdS light-dependent resistors (LDR) versus PIN diodes as light sensors]

> But I am leaning towards pin diodes. You said that they are fast. How are they faster and sensitive than Light Detection resistor? Do pin diodes have better spectral properties than LDR. I have posted the link of the pin diodes in the OP. They are cheaper and how can I use them instead of LDRs?
A photodiode will generate a small current (so it needs an amplifier of some sort) and benefits from regulated bias voltage, or from feedback that keeps it at zero voltage. An LDR, on the other hand, can operate on AC line voltage. Spectral sensitivity is important? Why? Both will detect daylight. Sensitivity is important? Why? Speed is of interest? Why? Either will react in under a second.