LDR pulldown resistor value ? For line tracking Robot !!

[ammarabbasi]

I am going to build a line tracking robot , tracking a 1" white line on a Blue arena . and potting 3 pingpong balls (preloaded) in each of already placed 3 baskets at 3 different positions , when it finds them . i have got LDR to track line .

I have LDR whose values of resistances for dark and Light in a room have been calculated . Now to decide for pulldown resitor should i take average of these two values . as

Pull down Resistance = LDR_resistance (light) + LDR_resistance (covered) / 2

OR

i have to stick on my tracking situation and get LDR resistace values from WHITE TAPE (used for line) and BLUE arena . and then take average of it , as

Pull down Resistance = LDR_resistance (white line) + LDR_resistance (blue arena) / 2

kindly have a look at schematics attached !

 

[miredox]

Re: LDR pulldown resistor value ? For line tracking Robot

The value of the resistor is not very critical. Especially since with RV1, you can set the threshold according to the resistor you used. If the contrast between blue and white is adequate, you will have no problems.

A good starting point is to choose the resistor equally to the average value of the LDR resistance, then you will have maximum sensitivity. So
[ LDR_resistance (white line) + LDR_resistance (arena) ] / 2
will certainly do.

But the value is not very critical, since you can adapt the threshold with RV1.

 

[ammarabbasi]

thanks miredox