The original Solar Tracker Arduino code was developed by George Bruce in Belgium.
George used two pots to set the delay time (dt) and the tolerance (tol) values so that they could be customized to the LDRs in use in the Tracker array.
BDG decided to forgo the two pots and arbitrarily set the delay time value at 10 and the tolerance value at 50.
The delay time set at 10 seems to be a good arbitrary value, however the tolerance value at 50 may or may not work depending on how well matched the LDRs are in the Tracker array.
I bought just the LDR array and the Arduino Shield and originally could not get the Tracker to work correctly with a tolerance value of 50. So I began experimenting with the tolerance value and found that a value of between 5 and 10 allowed the Tracker to accurately track the Sun without any hunting (dithering) of the gimbals.
I later bought two tracker shields from George Bruce’s 3D printer plans and hand selected LDRs with both high and low dark resistances and made sure that they were very similar in dark resistance.
The Tracker LDR array with the high dark resistance LDRs required a tolerance value of 25 to accurately track the Sun without hunting while the Tracker LDR array with the lower dark resistance LDRs required a tolerance value of 5 to accurately track the Sun without hunting.
I hope that the results of my experimenting will help some of you who have been having trouble getting your Solar Trackers to work.