Power Functions: Limit Switches & Servo's

[roamingstop]

Im just coming out of a second dark period and getting into Technic again now that Power Functions and some decent models have been released. One question always perplexing is how to implement proper limit switches? On the back-drivable (harmonic drives) Robotic systems we use at work, we have encoders and limit switches to stop the motors breaking the drive chains. However I have not seen anything suitable in the PF range; and a mechanical clutch is clearly used on the linear actuators.

Has anyone worked on a limit switch system yet? The PF functions with their C1 and C2 control lines would make a more useful system. I.e. limit switch detected (it could be an old RCX touch sensor) would disable C1, but still allow C2. A second limit switch could disable C2 and still enable C1. Thus a motor system could be driven to the end of range without difficulty. Useful examples could be a steering mechanism (two limit switches at either end), crane boom extension - or a pneumatic pressure regulator etc.

Im pretty sure it would be trivial to wire up a small circuit to enable an RC servo from the PF functions; C1 drive servo left; C2 drive servo right. A small one like this would make pneumatic switching interesting, whilst maintaining the flexability of building / combining small modules without too many custom parts. (sure a custom wiring).

Thanks for any comments.

[DLuders]

I did a search under the term "Limit Switch" in the TechnicBricks Blogspot http://technicbricks.blogspot.com/search?q=limit+switch, and came up with several interesting articles on how the Lego Linear Actuator's internal clutch could be used as a "limit switch" in Technic Power Functions applications. There is also some good info on Philo's website http://philohome.com/tech.htm .

Edited January 25, 2010 by dluders