I have just had a look at the ldr. I measure it from around 40 (infront of a 10w LED) to 20m ohms (in pitch black).

is there a simple formula for selecting the right value res to use in the divider?

I'm a little confused because the datasheet says 20k to 2m ohms but I don't measure that?

Thanks  

looks great, good work!

looks good mate, and very usefull!

How accurate are your voltages? I tried making one a while ago but even with a small load I could not keep the 12v rail above 12v

Oh, silly me thanks for pointing that out!

Hi all, I think it might be a nice idea to have either a project build forum or completed project forum.

The first would be a place for people to document their projects from start to finish, and the latter would be a place where people document their projects once they have been completed.

Just bumping this thread to the top because I still have the same issue with initialization, maybe someone who has not seen it has some suggestions?

Thanks so much DC

Would this be a suitable LDR? http://uk.rs-online.com/web/p/ldr/0596141/

Sorry for the noob questions but I have never used them before 

Thanks for the help 

what would be a SMD equivalent if I decide to go down the smd route?

Thanks again

thank you all for the help, that's great.

@dc42 - why do you need to use a 1K resistor? and how did you come to this value? I'm not questioning your intelligence in any shape or form I just like to learn

excellent I will set it up as a divider then

Because the resistance swing is so great, how would I calculate the value of the other resistor in the divider?

many thanks

Thanks liudr thats a good point. Just looking at the datasheet for my screens and I think they draw 120mA at max!

Any recommendations on a transistor? I guess it would have to be a fast one if I am to use PWM?

Thanks

thanks for the link, which bit do you suggest looking at?

the only relevent bit that I can see is 'Theremin – Use a photocell & piezo as a theremin' but I have no idea what that is doing, or what a theremin is?

Thanks kindly

http://www.rapidonline.com/Electronic-Components/Light-Dependant-Photoresistor-58-0134/?sid=53bc3fcf-5ffd-4335-aea8-a7850ab2d13f

just looking at the above, I guess the resistance swing would be from 1m ohm to 2-4k ohm, what would be the best way to use that? or are there more suitable ranges? Would I set it up as a voltage divider or directly to one of the analogue inputs?

Hi all,

I saw somewhere on here (cant remember exactly where) that someone had set up a photo resistor to measure amibent light and dim the LCD's back light accordingly.

I really like this idea and I would like to try it out.

I use LCD's in parallel mode (not yet tried a serial one). I guess the code should be pretty simple - analogue read on the photo resistor, and set it to vary the voltage on a analogue output pin?

I'm unsure on the coding and what type (and where to look) photo-resistor to use?

Thanks in advance

Thanks guys, the thing is I've got 100's of 10k leaded ntc sensors so I might just use them, and try and calculate the drop over the cable? Not sure if I should have the divider set up at the thermistor end or the measurement end?

Thanks guys! The Blinkm looks good but not so good for the price I will need a fair few so is there a cheaper alternative or a way to make them yourself?

Thanks