Mounting a tactile switch

mojorizing

Hello,
I have a SX48 proto board inside a Pactec handheld enclosure series TT. The proto board is 0.14" from the cover on bosses and I'm planning on using tactile switches with caps. In the past I've seen tactile switches w/ caps used but these had plastic overlays with print on them. In my case, I'm using a 4 x 20 LCD where the bottom line of text will depict what each of the 3 tactile switches do. These button will be just below the LCD, so I wasn't thinking about using an overlay. The switch and cap are Mouser part # 101-0621-EV and 101-0210-EV. These would be mounted to the proto type area and pass thru holes in the cover.

My question is then, is it normal practice to use tactile switches w/ caps that pass thru a cover with no overlay or cover? Will these caps fall off with hard use?

Thanks, Kevin

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Bad spellers of the world untie!

uxorious

Yes, that is common practice for devices using capped tactile switches. Many use membrane style overlay labels to make a seal, but depending on the environment, a seal is not required. High end video equipment uses chassis with silkscreen and cutouts for tactile switches. The switches usually have internal LEDs and a clear lens so that a plastic label can be inserted for the function of the switch. Typically a clearance gap of about 5-15 mils exists around the perimeter of the switch. Look at this Panasonic Switcher: catalog2.panasonic.com/webapp/wcs/stores/images/LargerPhoto/AV-HS400AN_500.jpg

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~~ dRu ~~

RDL2004

The cap you are going to use has a small rim or edge around the base. If you make your opening just large enough for the upper part of the cap to pass through then there should be no problem of it ever falling out.

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- Rick

mojorizing

Thanks for the replies.

I've mounted the LCD and tactile switches in the Pactec enclosure. The 4x20 LCD display fits right on to the enclosure's mounting bosses.

With the SX48 I had to mill 0.050" from both sides of the PCB and notch the PCB in way of the middle, left side mounting boss of the case. That side of the PCB has just the ground plane. The middle, right side boss I milled away due to the PCB has traces on that side. The tactile switches are soldered to the back of the PCB. The case is strong enough not to need this one attachment.

Unfortunately, the caps for the tactile are mounted such that the rim sits inside the thickness of the case. Plus the diameter of the rim is 0.512" , just a tad over a 1/2" milling cutter. I simply enlarged the hole by going +/- .010" in the x/y directions ( I did this on my milling machine) This is a first prototype. For the final production unit, I'll use green buttons to highlight them, I'll machine the rim of the cap so it has a diameter of 0.480" ( I can do that on my lathe in one quick step. ) This will mean I'll only need to plunge cut the 1/2" holes in the case.

This project is a OBD1 handheld scanner for the porsche 964 , the porsche 911's made from '89 to '94.

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Bad spellers of the world untie!

uxorious

Looks very nice, you scored with the nice fit using off the shelf parts. I had to hack my RFID board a little to fit inside a Polycase VM-24, but it came out pretty sweet. (If I ever finish it, it will be posted in the completed projects forum)

If you end up with a slightly smaller PCB/display for production units, take a look at the Polycase VM-36 series. They are 2 inches shorter without a tapered shape, but have boots that wrap around them for durability. I have used several of the VM-24s with boots in my handheld projects. I've used Polycase for numerous projects and have been very happy. If you are going to have any volume done, they also do machining/silkscreening at good prices (for >100 lot sizes) I have a small box used for a splitter power switch that I am actually saving money by having them do the machining of the required holes because I order 250 at a time. The picture is of the prototype, but you can see that I have them drill three holes in one side and machine a rectangular hole in the top.

www.polycase.com/category/vm-series.html

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~~ dRu ~~