Improved Opto Endstop - Needs some improvement

Most of the Opto Endstops offered on eBay have used a design posted on the “instructables” website about a year ago.

http://www.instructables.com/id/Improved-Optical-End-Stop/


While the mechanical construction of the “Improved Optical Endstop” is much better than the reprap design http://reprap.org/wiki/Gen7_Endstop_1.3.1 , the electronic design has a flaw which will cause the endstop to fail slowly over time and become erratic and temperature sensitive.

I realized there must be a design problem when the opto endstops I am using in my Z Probe auto bed level compensation design failed for the second time in just a few weeks. While the stock Robo does not use Opto Endstops, many other printers and some mods do.

The solution is simple but requires some SMD rework/soldering skills.

The explanation of the design flaw and the solution is outlined in the attached notes.