rpm-based controller for variable-pitch prop

[werner2k]

Hello from Vienna (that one in Austria!). Does somebody know of a nice circuit-diagramm for a feedback-controller, which allows me to feather my variable-pitch prop when reaching a certain rpm value after engaging the electronic brake?
The project (a Grob G109 motorglider) uses a Cyclon 90 brushless motor, a JETI-BECless controller and a 10SLipo-Powerpak.
The variable-pitch-prop can be feathered using a standard-servo from the receiver, but I would like to automate it based on the actual rpm's.
For a sensor either a Hal-senssor or optical one is possible, and I have a solution for counting the sensor's pulses and calculation the rpm's - I just dont want to go all the way to an on-board micro-computer (going back to PIC-programming would be a last ditch-solution) - any suggestions are greatly
appreciated!

[Cyberwollf]

any progress?

are the sensors's pulses counted analog or digitaly. maybe some ADCs and comparators.

[werner2k]

Yes there is progress - I decided to go for the microprozessor-solution, but spawned the pic-processor and decided to use an atmel-chip with the arduino-opensource development environment (thats a free high-level-language, programming-boards at around half the price of pic ones, etc.)
got the development package from italy just this week. the sensor-hw will be an optical one (no magnets on the axle).

[jperch]

If you are already using a brushless controller, you can sense the RPM from teh signals being sent to the motor. You don't need and extra optical or hall effect sensor. Eagle Tree now makes a sensor that electrically conntects to the wires going to the motor and can record motor RPM.

Joe