Braille Raised Keyboard Letters and Numbers

I previously designed a keyboard for students with vision impairments, but none of my students read Braille. However, I hope to reach a larger audience with these keys.

Please provide feedback if you have any! Being a sighted individual, I am at a disadvantage. I'd love to make changes that will increase user-friendly interface with this design - larger dots, higher raise of dots, different spacing or other suggestions are all something I am interested in knowing from 1st hand use of the design. My many thanks!

Post-PRINT on August 21, 2018
I am dissatisfied with the overall quality of the vertical spacing in the dots. I may have to calibrate the sizing or shape. The horizontal dots don't join together, but as seen in the last post-print photo, the dots are somewhat connected. I had to wire brush and use a small knife to remove some plastic to shore up most of the dots on the other two boards.