Electronics Forum / Electronics / July 2009

Something else to add to the sum of human knowledge.
Because I had them already , I have used 3.5mm co-axial mono connectors to
join vavious bits and pieces in my P.I.R. to camera setups.
In a scheme where everything depends on presence or absence of a voltage
this was a Bad Move. The contact between these line-plugs and line-sockets
is dodgy: a light tap at the point where they are connected is enough to
interrupt the earth/shield contact. The signal part of the plug is gripped
by a little spring inside the socket, and probably doesn't ever lose
contact, but the outer earth/shield plug merely slides into a cylindrical
hole. It looks and feels as if it is a snug fit but can, as I said,
momentarily lose continuity if moved even slightly. In my scheme, such an
interrupted connection is equivalent to the end of one camera trigger and
the beginning of another trigger. I believe that sometimes it has occurred
that there was no initial contact at all and that valid signals from the
P.I.R. were never sensed by the camera.
On the weekend I will replace all these connectors with RCA connectors.