A friend of mine who teaches high school science commissioned me to make a Jeopardy style quiz game controller with a large timer display and buttons for players. The best way to make a button for the players that I could think of was to use the large push buttons you can find at most dollar stores. The complete project description is available on my website!
The problem with using these buttons is that they were designed to be push on/push off, and I need a momentary button. Rather then buy new buttons and replace the stock ones (as is done in this Instructable by jaycollet) I figured out how to easily convert the built in button to be momentary.
All you need are a few simple tools and a little bit of motivation!
Step 1: Equipment and Materials
Push Light - These can be found at any dollar store. If you are a big spender, you could use an Easy Button from Staples.
Precision Needle Nose Pliers
Small Gauge Phillips Head Screwdriver
Step 2: Dissassembly
First things first... we have to get inside of the light fixture.
There are four tiny screws on the bottom side of the light. Remove them, but don't lose them!
Step 3: Inspect the Inside
With the screws out, the outer shell can be removed. There should be a piece of cardboard inside of the shell, this is there to block light from leaving the sides of the button. The upper dome is not attached to anything, but just sits on the inner springs inside of the outer shell.
Set the shell and dome aside for now and focus on the inner circuitry. The piece of white paper is glued to the base. It is there to reflect light up and out of the top of the button. I removed mine because I plan on removing the bulb completely. There should be a couple of wires coming up from the battery compartment. One wire will go to the light bulb, the other to the switch. Another wire connects the second terminals of the bulb and switch so that when the switch is pressed, a complete circuit is formed.
Both the bulb and button should be tightly inserted into their compartments and can be easily removed by lightly pulling up on them. Do not pull by the wires or they break away from their terminals. (Unless, of course, you are going to modify the circuitry and replace the wiring anyway. Then, by all means, yank away.)
Step 4: Switch Mechanics
Our main focus is now the small push button switch. The upper portion is a different color than the lower portion and can be removed. Using the pick, carefully pry the top portion off by way of the tabs on either side of the switch.
Very carefully remove the top portion of the switch. The inner depressor will shift forward with the cover removed, but hopefully it will not shoot off. There is a very small spring underneath of it. If the entire switch comes a part, it can be put back together fairly easily. To prevent this from happening, I suggest you keep the switch pushed down with your finger at all times. I was able to remove my finger for the picture, but it was risky business!
There are two things to notice about the switch. The first is the small metal contact piece that slides up and down as the switch is pushed. If this piece comes out, the switch will not work unless you can find it and put it back in place. The second is a metal pin in the front of the switch. It is this pin that causes the switch to lock in the on state when it is pushed, and it is this pin that we need to remove.
Step 5: Switch Modifications
Hold the switch in one hand and keep a finger pushing down on the depressor at all times so it doesn't shoot off. Using your other hand and the needle nose pliers, carefully grab onto the pin and pull it out. You will need to wiggle it around a bit, but be careful not to let go of depressor. With the pin out, there is nothing holding the switch together.
If you do not have precision needle nose pliers, you won't be able to grab the pin! You may have some luck with a pair of teasers, but normal sized pliers will not fit into the gap.
Step 6: Cleaning Up
With the pin removed, the top portion of the switch needs to be replaced. This can be a bit tricky since you still need to keep the switch pushed down. Carefully slide the top of the switch under your pressed down finger until the top of the depressor is aligned with the top hole and quickly push the cover into place. You now have a momentary switch as opposed to the original push on/push off switch.
The entire push light can now be put back together, or other modifications can be done!
One thing I noticed while taking a few of these buttons apart was that the switch terminal soldering wasn't consistent. That means that sometimes the switch was wired to be closed (light on) when pushed, and sometimes the switch was wired to be open (light off) when pushed. Since the button was designed to be push on/push off you would never notice this fact, but if you are using this as a momentary button, keep in mind the difference in polarity. You may need to change which switch terminals the wires are soldered.
With the pins closest to you, the center pin is the common one. Connect the second wire to the far right pin for a normally open button, or connect the second wire to the far left pin for a normally closed button.