FYI - Don't know if this is common knowledge, but I'm hoping to add a sonar so that during the climb, we have some help in clearing the 12 inches needed. Software is aware of this but perhaps not the hw team.
There are 3 options for the sonar.
- The small proximity sensor we used on Satis last year. The Vex version was better than the other cheap blue one we had (SparkFun maybe?). Easy connection, good down to a couple of inches with a 1 inch resolution. These are simple transmitter and receiver pairs that require the host to calculate the time difference between the send and receive signals. It works but is not my favorite. The Vex model is actually pretty expensive given how little it does ($30).
- Maxbotix sonars are also easy to use. I know we have some with a 30cm min range and we may have one that's 20 cm. Both will work though the 30cm means we won't get good data until just before we reach our desired height (accounting for bumpers).
- From FirstChoice, we got an industrial sensor from Rockwell Automation. This is probably the best of the sensors in terms of quality but the hardest to use. It's min distance is 30 mm. It too is analog output but requires some additional amount of external support. Supply voltage is 15 to 30V so we can power it from the pneumatic supply or use a DC-to-DC converter. The output is 0-10VDC so we need a divider. The min/max points can be preset via a simple procedure.
There's an analog input already allocated for this.
My preference is probably #2. All options require some testing. We've testing #2 before so we know it's behavior. Option #3 is new to us; we should take some time and learn about it for future years.