There is a new version with Photo Diode instead of LDR.
LDR had not polarity. This new component has 2 pins, the longest is marked E, the shortest is marked C in the manual.
When Im measuring this component it says that the shortest to + says its leading on 1,7 Volts.
The other way its blocking. Similar to a LED.
On the manual it says point 11 is a LDR, which its not.
On the circuit board it says TR1 but no C or E placement !!!
The updated Circuit diagram:
For placement of the Phototransitor (TR1) see updated step 11
Best Regards,
Velleman Support