LDR becomes brownish on surface WHY???

[Abhinandan Aggarwal]

why does my LDR become brownish on surface.....

 

[betwixt]

Under what circumstances is it doing this?

In direct sunlight for very long periods it is possible the plastic body, if it has one, is deteriorating in UV light. It may also be overheating, the resistance of an LDR drops as the light level increases so the current passing through it will also increase. In a poorly designed system it could pass enough current to overheat itself.

You really need to give us the part number of the LDR, some idea of how it is connected and a photograph of it so we can see the brown for ourselves.

Brian.

 

[D.A.(Tony)Stewart]

It can be many reasons, depending on materials; essentially a poor choice for unprotected solar power sensing of ambient light.

- the problem may be with the Polymer, stabilizer or the process.

- it can be triggered in poor parts from Fluorescent source or Sun or heat with moisture in the molding process or lack of formaldyhyde used with CdS chip processing from Oganic contaminants.

LDR's also use a substance Cd, banned in most countries to avoid toxic dumping, and have huge tolerances compared to water clear or Daylight blocking silicon photodiodes, but convenient lower impedance, which not a huge obstacle.

I would have considered LDR's obsolete for new design 20 yrs ago, err make that 30 yrs ago.

 

[ArticCynda]

I would have considered LDR's obsolete for new design 20 yrs ago, err make that 30 yrs ago.

Interesting point of view, could you elaborate on that? If you take the classic example of turning on the headlights of a train automatically when it drives through a tunnel, what would you use as low cost light sensor instead?