[TowerTalk] Prop pitch magnetic reed switch

Mel Whitten mel at melwhitten.com
Thu Jul 14 22:40:27 EDT 2005


I am using a larger prop pitch rotator with a M2 RC2800P-A controller and Mike's reed switch conversion kit for sending the digital pulses.  For several days, the rotor was operating intermittently.. motor would run a couple seconds and then stop. After a few attempts to get it to run normally, it would start working again and all was well.  I found when the rotor was working OK, the 11v DC digital pulse was about 5ms in duration and repeated every 25ms in Mode 0 and Speed 5. When it was not working, the pulses were not present.  A continuous short across the pulse leads (less than 2 ohms) was observed.  At the rotator, I pulled the cover off the motor and confirmed the magnetic reed switch was "stuck" closed.  A light "tap" on the switch however, opened the contacts. I ran the magnet across the switch again while observing the Simpson 260 and contacts closed but remained closed after moving away from the magnet.  Again, another tap and the circuit opened back up.  It appears the contacts are sticking... or it is possible the switch itself has become magnetized?  Maybe just enough to hold them closed until subjected to a slight vibration?  If so, is it possible to degauss the switch?  The switch mfg appears to be G R I, p/n P-20-A with mfg date of 1-Q-97.  I was not successful in finding this switch on in my search on the net. M2 responding quickly and is sending a new switch.  I am sure this will fix my problem, but just curious about the failure.  I've been using this prop pitch for about 2 1/2 years, but I believe original owner did not have it in service very long. Has any one had a similar experience with their prop pitch? Any comments would be appreciated.

Mel, K0PFX
St Louis



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