PIC, AVR, and Arduino are ubiquitous in projects these days and a lot of the time it’s easy to over-complicate things with their use. In this case, [Tod] wanted to use a momentary tactile switch to turn something on and off. Instead of going with a microcontroller he built the circuit around a 555 timer. What he really needed in this case is a flip-flop but lacking a chip for that he went with the 555 because it has one built-in. Three resistors and a capacitor later he’s in business, adding another resistor and a transistor to deal with the load switching. We’ve embedded video of the circuit controlling an LED after the break. This IC ends up in a lot of projects so dig through your parts bin and give this circuit a try.

Electronics parts can be a pain to choose. It’s often hard to tell from manufacturers’ datasheets if a part will fit your design. We auditioned six different tactile switches to find a cheap button to use in upcoming projects. A tactile switch, also called a momentary button or push-to-make switch, is commonly used for input and microcontroller resets. This type of button creates a temporary electrical connection when pressed.

Footprints for most of these buttons are available in the Cadsoft Eagle library switch-tac, or in the Sparkfun parts library under TAC_SWITCH. Buttons in the image above are discussed from left to right.

Through hole push button switch (6mm): This switch will appeal to fans of through-hole parts, but you can see that it’s actually smaller than the 6x6mm surface mount buttons. Note that it does not have the standard 0.1″ straight mounting legs, and thus won’t fit in a breadboard. Common package name(s): DTS-3 (S1 above).

642-MJTP1250 (16 cents)

Regular SMD tactile switches (6 X 6mm): A 6 x 6mm tactile switch is probably the most common surface mount button. Even though it’s surface mount, it’s large and easy to solder.  The button has two pairs of leads (1&2, 3&4) that connect internally to the same switch — although there are four legs you only get a single switch. You only need to connect one pin from each pair to use the button, but it makes no difference if you decide to connect both. The yellow and red buttons are rated in terms of the force required for activation (gf), yellow requires the most force (520gf) and makes the loudest snap. Common package name(s): DTS-6 (S2 above).

101-0164-EV (22 cents)

101-TS5922T5202-EV 520gf YELLOW (36 cents)

101-TS6824T2604-EV 260gf RED SMT (51 cents)

Small SMD tactile switches (4.5×4.5×0.4mm): Unlike the previous buttons, these tiny switches require practice and skill to solder. While the mounting area is only 12% smaller than the previous buttons, the leads are tiny and hidden under the package. Like the 6 x 6mm tactile switches, these are rated in terms of actuation force (gf). We were unable to find a ready-made footprint for this part.

688-SKRMAA 160gf (30 cents)

688-SKRMAB 260gf (30 cents)