getting height of pot, fader and button to line up on pcb??

[intellijel]

I am making a controller with pcb mounted pots, sliders and tact switches. The problem I am having is with making sure everything will protrude through the frontpanel at an appropriate height.

The problem component is the pcb mounted pots. All the ones have bodies that are slightly too tall (or just on the borderline) relative to the height of the tact switches with caps. I have looked at a bunch of different combinations of different pots with different switches+caps but with the same issue.

These are the parts I would like to use:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=SW801-ND  tact switch

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=SW255-ND  switch cap

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=PP1045SB-ND slider

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=P3E5103-ND    pot

the body height of the pot: 8.5mm

the height of the tact switch with cap is 10mm and it need to protrude by 1mm from the front panel. If I have a 2.5mm front panel then that means the max height the pot can be is 6.5 mm.

So my two choices:

1. Find nice tact switches+caps that are much taller

2. Find pots that are shorter bodied

Any tips for this?

I made 3d models to see how everything lined up and this is where I really noticed I had a problem.

Maybe my real question is:

What is a good low operating force, inexpensive, reliable tact switch that has colored cap options and is greater than 12mm in height ?

[chuck]

I'v just use different PCNs for the things that are different height, then mount them either off a support behind them, or from the front with machine screws glues to the front panel -- depending on how heavily used I think the device will get.

So an LCD, buttons and pots would be three different boards.

[intellijel]

using different pcbs is not an option for this design.

On the datasheet for the panasonic pots there is one that is 7.5mm tall: EVUF2K

If I used this and reduced my front panel thickness I could make it work. Trouble is that it is not available at digikey.ca or mouser.com

[cimo]

hi

with the original design you are off just 2 mm with the buttons right?

now i am not sure if that s actually possible cause i never tried it myself but what about glueing a 2mm shim under the buttons? I am not sure if the pins are long enough, you can check it.

even more crazy:

get a throught hole plated proto board, mount the button/s on it, solder the buttons only in the top side then place the protoboard on top of another protoboard (i am assuming you are using proto boards for the CS but it could work also with normal boards+protoboards) with aligned holes, stick a 0,0005% tolerance cut resistor lead (Wilba s organizing a bulk order for these rare items) in the hole and give it plenty of solder.

Simone

[chuck]

cimo has a point.

Just make the leads longer....  shim it up with protoboard or whatever.

[Jidis]

Intellijel,

I ran into the same issue last year:

http://www.midibox.org/forum/index.php/topic,8294.0.html

That stupid PCB & panel has actually been finished and populated soon after that post, but I haven't needed it and haven't felt like getting back to molding the button caps to finish it. ;D

The plan is:

To model taller add-on caps for the switches (similar to what Sasha describes) and glue them to the existing flat caps. As with yours, the button caps are the main problem (faders and pot shafts are already tall enough to need cutting). I'll likely be slicing up what I need out of modeling clay, fine tuning the shape, greasing them up, and then setting them into a shallow tray of resin or plaster to get a mold for the finals. There's probably a bunch of material that could be used for the models though. The duplicates will be made with fiberglass resin, tinted with paint, but I'm not sure I can get the desired color without spraying them afterward.

I'll probably make them just slightly smaller than my panel holes, so they don't scrape or bind. I'll install them with the PCB mounted to the panel and may put temporary shims of paper or thin tape on the inside edges of the panel holes to make sure they sit perfectly centered when they are being glued to the stock caps.

Hope that helps,

George

PS- In my case, I actually need different shapes than what the buttons have. If you don't, it may not be a bad idea to just try to jack the legs up longer like others have suggested. With mine, I had also considered doing that, using those round machine pin legs from an IC socket and soldering them to the end of the original legs. 

[stryd_one]

Moral of the story: Pick your switches/lcds/encoders/knobs etc first, then design the case and pcbs to hold them all....