This is a simple test rig for a little solar tracker I'm building.

Hence the dummy LDR I uploaded yesterday.
http://www.thingiverse.com/thing:858043

Analogue pin A0 for pair 1 & 2
Analogue pin A1 for pair 3 & 4
Test pin 9 (raise to HIGH to test) -Saves power - though not sure how much(!)

Gnd - LDR1 - A0 - LDR2 - +ve(pin9)

Gnd - LDR3 - A1 - LDR4 - +ve(pin9)

TWO Sets of 2 LDRS WITHWIRED IN SERIES BETWEEN +ve (pin9 to HIGH) and Gnd. Pin A0 is central to the two LDRs.

LDR LAYOUT:

1 ! 4

3 ! 2

1 & 2 is a set, 3 & 4 is a 2nd set.
1 & 3 GND; 2 & 4 +ve (or Check Pin)

Choice Table:
CASE 1:
A0 High A1 High MA Right

CASE 2:
A0 High A1 Low MB Down
CASE 3:
A0 Low A1 High MB Up

CASE 4:
A0 Low A1 Low MA Left

Other more complex cases: when three are shaded or partially shaded.

Sorryy, This is random tired writing.

I'm turning in for the night.

EurIng Andy Southern

aka Bath Robotics