My recent slider switch and the rotary switch I did some time ago turned out pretty well. They were both mostly 3D printed, and were implemented using reed switches and magnets. I wanted to see if the techniques used for them could be employed for other components. While I don't need one right now, I could have used a customizable push button switch back when I was constructing my Minivac 601 Replica to obtain a part more authentic than the off the shelf button I ended up using. So I decided to try my hand at making a DIY push button.
As can be seen in the pictures above I did indeed make a panel mount push button switch. You can find the construction details and STL files in my Mostly 3D Printed Push Button Instructable so I won't repeat them here. What I do want to talk briefly about is some of the design considerations that went into the build.
Making Magnet/Reed Switch Components
There are a few things in common with all three of the components I have designed so far:
- Magnets are used to both actuate the reed switches and also to provide feedback to the user in the form of "stops" or "detents". For the push button they replace a spring.
- The feedback provided by the magnets is unexpectedly satisfying.
- In the case where we are creating detents by having strategically placed magnets attract the moveable slider or knob to predefined positions, the switches actually accelerate to those positions then stop quickly with a nice "thunk". Hard to explain but it feels great.
- For the button, as you push the repelling magnets closer together they push back harder much like a spring under tension would. The magnet implementation feels a bit "softer" at the beginning of the push which is not necessarily a bad thing.
- Obviously the reed switches must be placed sufficiently distant from the magnets that are being used to provide feedback to prevent activation. This limits how small of a device can be achieved using this method.
Some things I've learned:
- You have to be careful of the placement of the "actuating" magnets. Sometimes aligning them with the exact center of the reed switch is not the best strategy. Case in point the push button: When I had the actuating (middle) magnet in a line with the other two, and directly over the center of the reed switch below, it would not trigger the reed switch when lowered. I had to offset the magnet from the center point as above to get good results. (There is probably a way of reading this from the reed switch data sheet. I guess should have checked.)
- I really like the reed switches I have been using (Digi-Key part number 2010-1087-ND). For one thing they are quite rugged. The cheaper glass modules will work but are easily broken. The form factor with both pins pointing downward makes them easier to integrated into a design (IMHO). Also the pins themselves are quite robust and take solder well.
- Keep in mind that reed switches come in all flavors, NO, NC, and even NO/NC. Be creative.
That's it for now. If I think of anything more I'll post it here.