Son of Motion detector fires off LED display

[pittsallen@usa.net]

Good morning Electronics Zone,

Using motion detector to fire timer cicuit to operate LED display.
LED displays are beautiful and reliable.
Finally figured out the 555 timer and have two circuits that I have adopted to accept the two second signal from the motion detector and extend the operation of the LED display to one minute. They are both timer circuit kits: the Velleman P2579 and the Can Kit CK002.
A crude diagram of the system can be seen in
motion_detector_w_LED_display_c.gif, attached.
More data on the system can be found at
http://www.electronic-circuits-diagrams ... php?t=4775

Every thing works fine except the motion detectors. I have had four of the cheaper Quoruam G6547 PIR and they have all worked for a while and failed. So I purchased a more expensive Honeywell IS215t. It also worked for a while and quit working. (In fainess I think I fried one of the G6547 by connecting it to an unregulated power supply.) Begnning to think
something about the system is killing the moption detectors. Bought a new Honeywell IS215t. I have read that when one is operating a relay with a signal it is a good idea to put a diode across the signal output. I was going to try that this weekend. Then I realized that I already have a diode, a light emitting diode, across the output. So I am out of ideas.
Any ideas why the PIR motion detectors keep giving up the ghost?

Allen in Dallas