Today I finish a new PCB design, Rev3. This time I decided to mount the ultrasonic transmitters and receivers on the PCB. This gives me a 15 by 2 inch board. The plan is to mount the ultrasonics on the back side, then mount the board upside down, with the components hanging down. I was able to take advantage of the extra board space to spread the circuits out. This allowed me to make a two layer board, instead of four, and saved some money.