Post by thread:[PICLIST] Need some switch ideas

I am developing an underwater digital camcorder and need some suggestions on pushbutton switches for the body. The requirements are that they are fairly small (1/4" to 1/2"), sealed to 200ft, can handle harsh environments (sand and sea water) and provide contact as long as depressed (unlike piezos which put out a single pulse). They should not draw much current when open and can be read by a PIC. One of the hangups is that at 200ft, the pressure on a 1/4" button is 4.4lbs. At sealevel, the switch would need at least 5lbs of force on the button to remain useful at 200ft. We are considering resistive ink technologies and looking for the pressure differential of someone adding 1 lb of force. Any other creative ideas would be greatly appreciated. Sorry if this is somewhat off topic. This is a great assembly of creative people (and I am using a PIC to read them.....) -- Steve Nordhauser Director of New Product Development Imaging Systems IEM Corp. 60 Fourth Ave. Albany, NY 12202-1924 spam_OUTdigitalTakeThisOuTnycap.rr.com http://www.iem.net Phone: (518) 449-5504x21 Fax: (518) 449-5567 -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

use a hall effect device inside the pressure chamber which is sensitive enough to detect a suitable magnet on a button. If the button/magnet assembly is outside the pressure chamber then the activation force need not change between surface and required depth. Thinking about it while reviewing what I have written, it may also be possible to do something similar optically - I do not know how thick the container needs to be for 200 ft, but if it had suitable material then reflective opto sensors where the led and optodiode are in a V looking for a reflective piece on the underneath of the button may also work. The led could be pulsed on while sensing the button. If more than one button is required this could also act as the button select, with all the photo transistors wired in parallel onto a single pin. :) -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

How about a momentary toggle switch instead of a push button switch? -- Rich Steve Nordhauser wrote: {Quote hidden}> > I am developing an underwater digital camcorder and need some suggestions > on pushbutton switches for the body. The requirements are that they are fairly > small (1/4" to 1/2"), sealed to 200ft, can handle harsh environments (sand and > sea water) and provide contact as long as depressed (unlike piezos which put > out a single pulse). They should not draw much current when open and can be > read by a PIC. One of the hangups is that at 200ft, the pressure on a 1/4" > button is 4.4lbs. At sealevel, the switch would need at least 5lbs of force on > the button to remain useful at 200ft. > > We are considering resistive ink technologies and looking for the pressure > differential of someone adding 1 lb of force. Any other creative ideas would be > greatly appreciated. Sorry if this is somewhat off topic. This is a great assembly > of creative people (and I am using a PIC to read them.....) > > -- > Steve Nordhauser > Director of New Product Development > Imaging Systems > IEM Corp. > 60 Fourth Ave. > Albany, NY 12202-1924 > .....digitalKILLspam@spam@nycap.rr.com http://www.iem.net > Phone: (518) 449-5504x21 Fax: (518) 449-5567 > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Steve Nordhauser wrote > I am developing an underwater digital camcorder and need some suggestions > on pushbutton switches for the body. The requirements are that they are fairly > small (1/4" to 1/2"), sealed to 200ft, can handle harsh environments (sand and > sea water) and provide contact as long as depressed (unlike piezos which put > out a single pulse). They should not draw much current when open and can be > read by a PIC. One of the hangups is that at 200ft, the pressure on a 1/4" > button is 4.4lbs. At sealevel, the switch would need at least 5lbs of force on > the button to remain useful at 200ft. > > We are considering resistive ink technologies and looking for the pressure > differential of someone adding 1 lb of force. Any other creative ideas would be > greatly appreciated. Sorry if this is somewhat off topic. This is a great assembly > of creative people (and I am using a PIC to read them.....) > > -- Use a Reed Switch (or even a reed relay) on the inside of the pressure casing with a bar magnet on the outside. When the bar magnet is in line with the reed, the circuit will be closed. If the centre of the bar magnet and the centre of the reed are aligned then when you pivot the bar magnet through 90 degrees the magnetic field across the reed will drop to zero and the reed contacts will open circuit. Simple, Cheap, no seals or pressure differentials to worry about and it draws no power. Regards Chris -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Though it would involve the invention of a mechanical device, this might give you an idea. Make an optically operated device. A plastic rod or some such that interrupts a light beam. The optics are inside the camera but the button/slide part is outside. The trick then is that you can let water pressure on both sides of the button and don't have to worry about the effects of pressure changes. Barry At 12:27 PM 4/3/01 -0400, you wrote: {Quote hidden}>I am developing an underwater digital camcorder and need some suggestions >on pushbutton switches for the body. The requirements are that they are fairly >small (1/4" to 1/2"), sealed to 200ft, can handle harsh environments (sand and >sea water) and provide contact as long as depressed (unlike piezos which put >out a single pulse). They should not draw much current when open and can be >read by a PIC. One of the hangups is that at 200ft, the pressure on a 1/4" >button is 4.4lbs. At sealevel, the switch would need at least 5lbs of force on >the button to remain useful at 200ft. > >We are considering resistive ink technologies and looking for the pressure >differential of someone adding 1 lb of force. Any other creative ideas would be >greatly appreciated. Sorry if this is somewhat off topic. This is a great assembly {Quote hidden}>of creative people (and I am using a PIC to read them.....) > >-- >Steve Nordhauser >Director of New Product Development >Imaging Systems >IEM Corp. >60 Fourth Ave. >Albany, NY 12202-1924 >digitalKILLspamnycap.rr.com http://www.iem.net >Phone: (518) 449-5504x21 Fax: (518) 449-5567 > >-- >http://www.piclist.com hint: The list server can filter out subtopics >(like ads or off topics) for you. See http://www.piclist.com/#topics > > > > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Hi Barry, I made a small underwater flash unit and did not want to have the hassle of finding a waterproof switch for the on/off switch. Since the enclosure was plastic, I used a reed switch on the inside and a magnet on the outside which when placed next to the reed switch turned the flash on. You could expand this concept to a small keypad if needed. Ceramic magnets dont seem to have a rusting problem. ======================================================= Lawrence Glaister VE7IT email: .....lgKILLspam.....jfm.bc.ca 1462 Madrona Drive http://jfm.bc.ca/ Nanoose Bay BC Canada http://gspy.sourceforge.net/ V9P 9C9 http://members.home.net/cncstuff/ ======================================================= {Original Message removed}

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 list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

On Tue, 3 Apr 2001, Alan B. Pearce wrote: > use a hall effect device inside the pressure chamber which is sensitive enough > to detect a suitable magnet on a button. If the button/magnet assembly is > outside the pressure chamber then the activation force need not change between > surface and required depth. Excellent idea with minor changes: use instead of hall, small reed cheaper contacts. No magnet on the button. Sell with your device a pair of gloves which have in two right hand fingers same material like electret have. ( magnetic powder included in rubber ) Anyway the diver needs gloves... I want 1 USD for any selled device... [hmmmmmm] Vasile -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

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 <RAMMERMANspam_OUTPRODIGY.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 <@spam@digitalKILLspamNYCAP.RR.COM> To: <KILLspamPICLISTKILLspamMITVMA.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.

Hello Steve & PIC.ers, Have a look at http://www.qprox.com They offer capacitive proximity switch ICs, specially for reading fingers through barriers. or, Go optical. I diddled with an IR switch some time ago for sensing finger presence through perspex. It worked _quite_ well, but I lost interest before putting it into any product. I could make this up into a commercial unit for you if you wanted (punt.. punt..) but I think you could just as well do it yourselves. See the genesis of this device at:- PIC12cxxx Design Challenge - Apps. Handbook. Microchip pub. DS40160A/3_017 pp 3-29 `Pulsed Optical Proximity Detector' ( Larry Nelson's design ) >Date: Tue, 3 Apr 2001 12:27:48 -0400 >From: Steve Nordhauser <RemoveMEdigitalTakeThisOuTNYCAP.RR.COM> >Subject: Need some switch ideas > >I am developing an underwater digital camcorder and need some suggestions >on pushbutton switches for the body. The requirements are that they are fairly >small (1/4" to 1/2"), sealed to 200ft, can handle harsh environments (sand and >sea water) and provide contact as long as depressed (unlike piezos which put best regards, John e-mail from the desk of John Sanderson, JS Controls. Snailmail: PO Box 1887, Boksburg 1460, Rep. of South Africa. Tel/fax: Johannesburg 893 4154 Cellphone no: 082 741 6275 email: spamBeGonejsandspamBeGonepixie.co.za Manufacturer & purveyor of laboratory force testing apparatus, and related products and services. -- 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: TakeThisOuTstevebEraseMEspam_OUTtla.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.

Steve, I've got the image. It would certainly work for equalizing the pressure. I think it would even be feasible for the shutter button. It would be a problem for all the menu switches that would need to penetrate the body (the internal boards would need to look like swiss cheese). On the other hand, I would like to visit a consultant in New Zealand..... Steve -- Steve Nordhauser Director of New Product Development Imaging Systems IEM Corp. 60 Fourth Ave. Albany, NY 12202-1924 RemoveMEdigitalTakeThisOuTnycap.rr.com http://www.iem.net Phone: (518) 449-5504x21 Fax: (518) 449-5567 Subject: Re: [OT] Re: Need some switch ideas Date: Thu, 5 Apr 2001 09:50:50 +1200 From: Steve Baldwin <steveEraseME.....TLA.CO.NZ> > 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: EraseMEstevebtla.co.nz fax +64 9 820-1929 ====================================================== -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email RemoveMElistservEraseMEEraseMEmitvma.mit.edu with SET PICList DIGEST in the body

Steve, > I've got the image. It would certainly work for equalizing the > pressure. I think it would even be feasible for the shutter button. > It would be a problem for all the menu switches that would need to > penetrate the body (the internal boards would need to look like swiss > cheese). That was more for illustrating the concept. Picture a "V" shaped piece of plastic behind a rubber keypad. The "V" pivots on the apex and one end is below the button and the other is in the gap between the buttons, the "V" only needs to be a few mm high. > On the other hand, I would like to visit a consultant in New > Zealand..... I had two US customers "visit" last month. I guess you guys can't be good at navigation. It always seems to take them a couple of weeks and a lot of miles to find their way back to the airport. And I have had business meetings at the Poor Knights Islands with the dress standard being a wetsuit. 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: RemoveMEstevebTakeThisOuTspamtla.co.nz fax +64 9 820-1929 ====================================================== -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email EraseMElistservspamspamBeGonemitvma.mit.edu with SET PICList DIGEST in the body

Here in Denver, at the foot of the Rocky Mountains, the standard visit is timed to end early on Friday. This leaves time to get to the ski slopes for weekend skiing. -- Rich Steve Baldwin wrote: {Quote hidden}> > Steve, > > > I've got the image. It would certainly work for equalizing the > > pressure. I think it would even be feasible for the shutter button. > > It would be a problem for all the menu switches that would need to > > penetrate the body (the internal boards would need to look like swiss > > cheese). > > That was more for illustrating the concept. Picture a "V" shaped > piece of plastic behind a rubber keypad. The "V" pivots on the apex > and one end is below the button and the other is in the gap > between the buttons, the "V" only needs to be a few mm high. > > > On the other hand, I would like to visit a consultant in New > > Zealand..... > > I had two US customers "visit" last month. I guess you guys can't > be good at navigation. It always seems to take them a couple of > weeks and a lot of miles to find their way back to the airport. > And I have had business meetings at the Poor Knights Islands with > the dress standard being a wetsuit. > > 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: RemoveMEstevebKILLspamtla.co.nz fax +64 9 820-1929 > ====================================================== > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listservSTOPspamspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spamBeGonelistservSTOPspamEraseMEmitvma.mit.edu with SET PICList DIGEST in the body

A good way to do this might be to use a magnetic reed switch inside the housing activated by a small moving magnet on the outside of the housing. The mechanism for moving the magnet may be exposed to the same pressure as the outside enviroment. You can either let this mechanism be exposed to the water or if you need it sealed, fill it with a liquid which has the same compressability as water. The resulting switch may be a little bulky, but is absolutely flood proof. At 200 ft any hole which has to be made in the housing is another potential way to flood the camera. If the switch needs to be made smaller then you can get away with a smaller magnet and shorter actuation stroke by using an electronic sensor like Hall effect or magneto resistance. Of course you need some extra electronics in the housing to drive/read these sensors, but the size savings on the actuator itself might be worth it. It is also possible to do much the same thing using an opto reflector sensor inside and a reflector on the end of the external actuator. In either case a spring loaded rotary or sliding actuator may save some space rather than a pushbutton. Please let me/ the list know how you get on with this project if you can. I've thought about this a bit with regard to housing my own camera and have some other (untested) ideas. I really must get around to doing something about it before I'm too old to dive................. Joe {Original Message removed}