Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: manut on December 04, 2009, 08:43:37 PM

Title: 50$ robot photoresistors
Post by: manut on December 04, 2009, 08:43:37 PM

hello,
I built my 50$ robot with two photoresistors of different values..now it seems to react differently to my hand hiding the light..
Do you think I should use same value for the photoresistors?
thanx
manu

Title: Re: 50$ robot photoresistors
Post by: Joker94 on December 05, 2009, 02:03:17 AM

it would be better to use the same valuesfor the sensors.

you may be able to adjust it in the code and all but that is alot more complicated than changing the sensors to the same value

and the same readings will be more accurate and better controlability

Title: Re: 50$ robot photoresistors
Post by: ozbot on December 05, 2009, 06:09:54 AM

Yes, get the values as close as possible.  Even when buying a bag of 5 or more of the same part, there are variations and it is good to test them to find the closest pair.

Title: Re: 50$ robot photoresistors
Post by: manut on December 05, 2009, 07:56:35 AM

okay, thank you...good to know..
Do you know a good value for photoresistors for the 50$ robot? I didn't find it in the tutorial
and also:on the package of one of my photoresistors, it's written: PHOTOCELL 40K-120K  OHM.  Does it mean that the resistance is 40K in the light and 120 K in the dark? ..that means that to find the value of the resistor, I have to calculate it like this: square root of (40K*120)=69,28K OHM  ?
thank you
manu