View Full Version : light resistors questions

08-28-2005, 06:02 AM
hi guys,
i want to incorporate a ligt resistor(s) to my robot, so when i looked informations on the web for them, what i found was that they are also called NTCs and thats all, but when i went to a radio club (serbian version of radio shack) i found that there are lots and lost of different options, like their resistance range and such,
i use atmel AVR uC-s, which are the ones which would be most appropriate for basic light sensing? i thought of 0-1k range, since i used once a 1k pot to test ADC. but am unsure.
could anyone help?

08-28-2005, 02:49 PM
Atmel ADC is optimized for 0 -10 k ( give 0 - 1024 ) . So any LDRwill be fine with similar range .

You can also go in for LDR connected to the LM324 ( comparator ) to give on off at certain levels .

What do you want to do with it ???

08-28-2005, 05:40 PM
just some basic light searching, nothing much for start, i am still developing basic robot platform which will give me enough space to experiment further on it.

08-28-2005, 08:06 PM
either u use LM324

or measure its resistance range mostly around 10K .
The one I used in range 400-350Kohm

But if u use it as a line follower then u have to place under robo, so the resistance order of 10K

So connect 10K with it and tie it with ADC of AVR

12-25-2005, 12:44 AM
use lm324 for comparing the output ldr's voltages....
set a potential divider and give input to the comparator such that wen it receives the light and doesn't, the comparator shud give differentlogic levels.

be careful, shield ldrs properly from ambient lights....
otherwise the performance might vary drastically from one place to other place.