Sensor Board in Enclosure
There is an easy way to assemble the sensor PCB similarly to previous versions, before start-stop indication was added. The green LED can be omitted, and the resistor for the red LED can be installed in a different way. The result would be that the red LED becomes an "On" or power indicator that stays illuminated as long as the sensor module is connected to the interface module. The following image illustrates how to stuff the 220 or 330 Ohm resistor and bypass the start-stop functionality.
The red LED just acts as an "On" indicator here.
This version of the sensor board also acts as an start-stop indicator so that the rider knows when to go and when to stop. If the sensor module is not being used to count roller revolutions, it can be mounted on the handlebars. Run an ethernet cable from the handlebars to the sensor on that bike. In other words, if you build 4 of these, you can mount 2 of them to count roller ticks, then mount another on the handlebars and daisy chain them with ethernet cables (i.e. from the main board to the roller tick counter to the handlebar 'indicator').
The Start-Stop indication is similar to this animation, except with only one red STOP light and one green GO light.
There are three LEDs now, instead of two. The red and green LEDs indicate to each rider whether it's time to go or stop. The white LED illuminates whenever the magnetic field is in the range of the sensor. Red or green must always be illuminated, but not both at the same time. Together, the start-stop lights also indicate that the board is getting power. If the board is connected to an Arduino that is not programmed with the OpenSprints firmware, both red and green LEDs may light at the same time.
For the green and white LEDs, 100 Ohm resistors are recommended (R1 and R3). For the red LED, a 220 Ohm or 330 Ohm resistor is recommended (R2).