Talk:Photoresistor

older comments
I changed the use of "LDR" since the article has changed name. I also singularized all uses of "photoresistor". Before, the plural and singular use was heavily mixed.

The previous author used italics to emphasize the dichotemy between intrinsic and extrinsic devices. At first read, the reason for the italics is unclear, so I simply added an introductory sentence to that paragraph to make it clear that it was about to discuss the difference between those two types. In which case the italics aren't needed. - ElusiveByte 00:38, Sep 22, 2003 (UTC)

symbol in circuit
Hi, would anyone who knows this subject add a picture of its symbol in a circuit scheme?

Added picture of symbol alone, thought this was sufficient. Only a paint drawing done by myself, if anyone feels they can do better, be my guest. This is a symbol used in the UK as mentioned in the article, I have no idea about other countries, maybe someone who does can add further images. Wheatleya 22:44, 22 February 2006 (UTC)

NOT PHOTOCELLS
Can I please add that Light Dependent Resistors are not photocells. They do not create an electromotive force (e.m.f.), and as such are not cells. A photocell is used as part of a circuit that makes use of the photoelectric effect to provide a current around a circuit that is proportional to the intensity of light. However these are different from a LDR, which simply varies the resistance in a circuit based on surrounding light. To repeat, LDRs are NOT photocells. —Preceding unsigned comment added by 92.12.43.166 (talk) 21:56, 26 February 2008 (UTC)


 * Neither were the devices known as 'photocells' (the vacuum device with a photo emissive cathode). They too did not create an e.m.f. but required an applied voltage to make use of them.  You are, of course, getting confused with 'photovoltaic cells' which do create an e.m.f. and hence a current (and thus power) in an external circuit. 86.166.66.41 (talk) 12:11, 4 February 2011 (UTC)

Circuit symbol
I've just noticed that Frozenport changed the circuit symbol of a LDR to Image:15580.gif. I have never seen this symbol in use, at least in the UK, and so I am going to change it back to my original. However, if is aware that the other symbol is used in other parts of the world, they are welcome to reinsert it. A quick Google of "ldr symbol" suggests that rectangular form is certainly more abundant.
 * Following the Google link you gave, it seems that a majority of the symbols are not as you claim rectangular - in fact a majority of the rectangle shaped images come from this article! I will leave the choice of what image to use to someone else, but I have yet to find a single other place where the rectangle shape is used. --Frozenport 00:17, 9 April 2007 (UTC)
 * Although maybe we should compromise at this --Frozenport 00:19, 9 April 2007 (UTC)

Neilgravir (talk) 21:13, 27 March 2007 (UTC)

Usual IEEE Symbol has a cirle around the rectangle with the arrows pointing to that. Tswsl1989 07:43, 28 March 2007 (UTC)

I have seen the symbol that looks like a resistor withe a oval around it on a schematic from the late 70s/early 80s, I am not sure if it is used elsewhere but I do believe it to be at least an alternate symbol so I think both pictures should be on the page -Austin 7/19/07

All 3 symbols are in use, so should be here really. The rectangle, circle and zigzag. Tabby (talk) 06:15, 3 January 2008 (UTC)

LDR voltage
hi, what is the average resistance of an LDR? say it is in a series circuit with a variable resistor, and a cell of voltage 12V.light wavelengths of 380nm (lowest) and 750nm (highest). if anyone can help asap that would be great!! 14 April 2007 —The preceding unsigned comment was added by 86.140.146.247 (talk) 10:56, 14 April 2007 (UTC).

Its hard to say what a specific circuit would use, but I have seen ones from the low 100k to several megohms. If you have the circuit and just need to check the resistance I recommend just using an ohmmeter -Austin Gibbons 22:14, 19 July 2007 (UTC)Austin 7/19/07


 * Different LDRs will vary in characteristics, but a popular device is the ORP12 (aka LDR03). The spec sheet states that it varies from >10 Megohm in the dark to 75 to 300 ohm when illuminated at 1000 lux (with a colour temperature of 2700 K).  The cell has a max voltage rating of 110 volts and a max power dissipation of 200 mW.  In real terms this means that such a cell could easily operate a medium sized relay without any additional components (other than a power supply that is!) 86.166.66.41 (talk) 12:18, 4 February 2011 (UTC)

Similar Devices
The description here seems almost identical to a Diode and/or a photo-voltaic (solar cell). Maybe someone who understands all three of these devices could point out what they have in common and what makes them different?
 * Tiki God 11:28, 7 September 2007 (UTC)

They are not similar at all. A diode usually only allows one "direction" of electricity to flow throw or otherwise cleans up the signal (or gives of light in the case of an led/light emitting diode). A photovoltaic transfers light (sunlight, usually) to VDC. A photoresistor is a variable resistor that resists more in low light. —Preceding unsigned comment added by 98.228.103.35 (talk) 09:18, 14 February 2010 (UTC)

Name
This should not be referred to as a "photoresistor," as far as most of the physics community is concerned. Wikipedia is the only site Google turns up after a definition-search for that word. The proper term is photoconductor—I think the page should be moved for encyclopedic purposes. Listing the synonym isn't enough. — DMCer ™  17:10, 27 February 2008 (UTC)
 * A CdS cell is known as both a Photoresistor and a Photoconductor. Take your pick. :-) Although as far as the industry is concerned the correct name is photoresistor. For example, the big companies such as DigiKey.com, Mouser.com, and even RadioShack.com will return no search results for photoconductor, but they return search results for photoresistor. --PaulLowrance (talk) 16:03, 11 June 2008 (UTC)

Not Comprehensive
These two lines from the article contradict: "The resistance of a photoresistor decreases with increasing incident light intensity" "In the dark, a photoresistor can have a resistance as high as a few megohms (MΩ)"

Perhaps the 2nd line should be reworded to "as low". — Preceding unsigned comment added by 2604:6000:8883:1201:58CD:F094:A934:1B67 (talk) 11:14, 21 May 2015 (UTC)
 * If resistance decreases with light intensity, then it is highest in the dark. Hence the article is correct. SpinningSpark 17:31, 21 May 2015 (UTC)


 * Technically, yes it is correct as-is. I agree with the first contributor, however, in saying that the use of over-complicated jargon is uncalled for outside of a textbook.  As is/are the words "thus" and "hence" - which add nothing to readability, and only sound pompous.  This is NOT a college textbook.  HENCE, it should not be written as such.  To wit:
 * Change this snippet to read as follows: "The resistance of a photoresistor increases in darkness, and decreases in light." <<< This is far better than what is currently written.  Casual readers don't care about ambient or incident light.  They understand what light is.  They understand what dark is.  Why introduce this level of technical detail at the top of the article?  Save the jargon for the detailed part below where folks can dig into the topic if they choose.  73.6.96.168 (talk) 04:04, 10 April 2021 (UTC)

Roach?
Is this sometimes informally called a 'roach'? I get the impression from this video and one of the comments. --Cancun771 (talk) 20:12, 6 August 2017 (UTC)

Examples
One of the examples links to an ecommerce site selling electronics hardware, is this an appropriate link? --Tim Savage

Lede Too Complex - Too Detailed
The so-called "lede" section contains a 2nd paragraph that belongs in the body of the article. Observe that the second para begins with: "A photoelectric device can be either intrinsic or extrinsic..." This is too much detail for a lede section. This type of information should be moved down into the body of the article... somewhere. Perhaps under a new section called something like "Types of Photoresistors", or "Design Characteristics". Whatever. In it's current form, the lede is WAY too complex and detailed - and serves no purpose except to scare away readers who just want to get a quick overview. 73.6.96.168 (talk) 03:55, 10 April 2021 (UTC)

India Education Program course assignment
This article was the subject of an educational assignment supported by Wikipedia Ambassadors through the India Education Program.

The above message was substituted from by PrimeBOT (talk) on 19:55, 1 February 2023 (UTC)