Post by thread:[PICLIST] [OT] Re: Need some switch ideas

This is interesting. I would have to be sure that there isn't any radiated light.... and I always need the LED lit. We have talked about the reed/hall effect ideas with magnets - they are very good for this application. The problem seems to be that they all still require a movable actuator. As someone suggested, if the back of the actuator isn't sealed, there is no pressure differential. Unfortunately, that means that sand could get under the button head and jam the switch. So, they solve most of the power issues, but not the pressure issue unless I am missing something. Steve Subject: Re: Need some switch ideas Date: Tue, 3 Apr 2001 14:46:54 -0400 From: Bob Ammerman <spam_OUTRAMMERMANTakeThisOuTPRODIGY.NET> A variation on the optical theme.... Bounce a modulated LED at an angle from the interior thru the (Lexan?) plastic enclosure to reflect at the plastic/water interface back thru the wall of the enclosure to a phototransistor. Placing your finger on the surface of the camera at the point where the beam reflects might strongly affect the reflected signal. Or, using the same technique by with a reflector on the back of a spring mounted button. When the button is pressed in the reflector will bounce the LED beam to the detector. When the button isn't pressed the beam won't be reflected, or will miss the detector. Bob Ammerman RAm Systems (contract development of high performance, high function, low-level software) -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

----- Original Message ----- From: Steve Nordhauser <.....digitalKILLspam@spam@NYCAP.RR.COM> To: <PICLISTKILLspamMITVMA.MIT.EDU> Sent: Wednesday, April 04, 2001 10:56 AM Subject: [OT] Re: Need some switch ideas > This is interesting. I would have to be sure that there isn't any radiated light.... There would have to be something radiated, I'm afraid. > and I always need the LED lit. Naw, just pulse it when you want to check. > We have talked about the reed/hall effect > ideas with magnets - they are very good for this application. The problem > seems to be that they all still require a movable actuator. As someone suggested, > if the back of the actuator isn't sealed, there is no pressure differential. Unfortunately, > that means that sand could get under the button head and jam the switch. So, they > solve most of the power issues, but not the pressure issue unless I am missing > something. How about having the actuator move horizontally along the outside surface instead of in-and-out. Now no sand can get behind it. Bob Ammerman RAm Systems (contract development of high performance, high function, low-level software) -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

> As someone suggested, if the back of the actuator > isn't sealed, there is no pressure differential. Unfortunately, that > means that sand could get under the button head and jam the switch. > So, they solve most of the power issues, but not the pressure issue > unless I am missing something. Steve Here's another approach. If you take the constant pressure inside the enclosure out of the equation, the problem goes away. What you have at the moment is a rod with 1 atmosphere on one end and a varying pressure (1-6 atm) on the other. If you can apply the external pressure to the other end of the rod, the two will cancel each other out so the key pressure will remain constant, regardless of depth. My ascii art sucks so I'll try a description to illustrate. Take one waterproof box and drill a largish hole that goes right through both sides. Stick a rubber patch over both holes. Measure between the inside faces of the rubber sheet an cut a piece of solid rod to match. When assembled, pressing one rubber patch will make the other deflect outwards. When submerged, the pressure deflection on both ends is the same so the rod doesn't move and the box is still sealed. Now put a cross piece on the bar so that it looks like a letter "t" and position the cross piece above the switch on the circuit board. Make one of the outside rubber patches inaccessable to fingers with a (unsealed) cover of some sort and you have a push button that has the same actuation pressure at any depth. Obviously as described there are some practical limitations. You can apply the same basic concept using pivots, etc to make it fit within your mechanical constraints. Assuming you are moulding your own case, the extra plastic costs almost nothing and you get the constant switch pressure you require. PS. I've been looking for a business related reason to travel to North America/Canada and try some ice diving. You obviously need to hire a consultant on this one. :-) Steve. ====================================================== Steve Baldwin Electronic Product Design TLA Microsystems Ltd Microcontroller Specialists PO Box 15-680, New Lynn http://www.tla.co.nz Auckland, New Zealand ph +64 9 820-2221 email: .....stevebKILLspam.....tla.co.nz fax +64 9 820-1929 ====================================================== -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.