Ambient Light Level Monitoring

[scottl]

I am working on a solar water heater project and would like to monitor the ambient light level. Can anyone recommend a simple light level sensor that can interface directly to an analog pin of a PIC? I have run accross the Intersil light to current optical sensor. I have a sensor that was removed from an old controller I had but cannot tell the manufacturer. The chip looks like a through hole ic!

Any help would be greatly appreciated,

Scott

[mister_e]

A simple 10cents LDR could work. Directly on a PIC ADC input? probably not due to the impedance of those LDR. Just put an OP-AMP (or maybe transistor) between your LDR and your PIC.

[sayzer]

Here is a sample similar to what mister_e mentioned.






Here is a link to find just about anything about "lights & components".
http://jp.hamamatsu.com/products/nod...ng=en&ext=html



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[Archilochus]

Not as cheap as the LDR... TAOS (Texas Advanced Optical Systems - or something like that) has some light-to-voltage & light-to-frequency converters for a few US$.

http://www.mouser.com stocks several part #'s

Arch

[scottl]

I have setup an LDR with Op-Amp and it works just fine. I have been looking at using the TI parts and have some on order but may go with the LDR if I can generate a curve to allow voltage to lumens.

I have been thinking of mounting the board in an enclosure with an electronics ballast then start with total darkness then generate a curve from 0-100% but this does not follow ambient lighting.

Any thoughts?

Thanks to all that has replied,

Scott

[Dave]

scottl, I have used 4 of the TSL230's in a sun tracking sensor unit for a solar furnace with great success. All you need to do is count the pulses gererated by the units. No need for linearization or amplifiers. The Texas Advanced Optical Systems (TAOS) TSL230 sensor precisely measures light using an array of photodiodes, with an output of digital square waves. The TSL230 has an input dynamic range of 160dB; that is, it can measure light over a range of 100,000,000-to-1. Parallax still has them for $4.95 each.

Dave Purola,
N8NTA

[scottl]

Dave,

This look like this will do the trick. I am going to order a couple to try and I will let you everyone know the results.

Mouser also has stock at $4.75!

Thanks,

Scott

[ardhuru]

Hi,

I just used an LDR in a simple voltage divider configuration, and it works very well.

Use the circuit Sayzer's given minus the transistor; feed the junction of the LDR and the resistor directly to the pic.

Regards,

Anand

[scottl]

Thanks for the reply! I will give it a shot this week.

Scott