Just discovered the amazing Photon and wanted to make an IoT garage door opener. I found a schematic that got me puzzled. https://i2.wp.com/www.circuitspecialists.com/blog/wp-content/uploads/2016/02/Schematic-rev1.jpg?ssl=1
It shows D0 output connected to ground. How does that trigger the transistor? I’m just curious to how that works as I found another solution to a garage door opener here on the Particle Community.