A Record of important things…

Rotor Tach

A lot of builders have added expanded scale tachometers for the rotor. The gauge supplied by Eagle has a very narrow active range. In flight, reading the range while flying would be tough. The acceptable range is 610 to 620 which is just a couple of needle widths.


I built this little display item. It is based on a 2" display from eBay and an Arduino processor. There will need to be some conditioning to amplify the incoming signal and to make sure the analog tach is not affected. On the bench I use an audio tone generator to mimic the signal form the sensor.


If the rotor is in the range of 610 to 620 the RPM is displayed in green.



When in the range of 605 to 610 the RPM is yellow with a downward pointing arrow and a tone. Between 620 and 625 the RPM is also yellow with a higher pitched tone. Above 625 the reading is red with a red up arrow and a higher pulsing tone. Similarly below 605 it is also red with a red down arrow and a pulsing low pitch tone.

This is designed to be easy and very quick to read with an attention getting audio tone mixing in to the headset feed. I plan on mounting it on the top of the pod as it is critical to interpret this quickly during autorotations. In the final incarnation this will be packaged well and be brighter. The display shown here is a tired old one I have beaten and abused and use for development where I may actually damage it.