On Tue, 2005-06-07 at 16:48 +0100, Howard Winter wrote:
> Peter,
> Another downside is that knowing sunrise/set times isn't good enough to predict the light level - the time 
> when you need to switch house lights on here can vary by as much as a couple of hours on consecutive days 
> depending on the cloud cover.  Much better to measure the actual light level.

Indeed.....

I've been playing with a LDR, but last night I found what I think is a
selenium cell from an old servo positioning system in my junk box.  I
think this will be easier to use as I believe the output current will be
linear to the light intensity.  It was dark outside when I found it so
I'll have to wait until I get home this evening to see what range of
output current is available, and how it varies.

I spent some time last night playing with a "log amplifier" for use with
an LDR,  but on reflection today I think I might need an anti-log
amplifier (I need to think more (or maybe less) about this).

Peter



-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist