Switches & Buttons

A switch is a mechanical contact that opens or closes a connection. de:volt ships three: the Switch (SPST) switch-spst, a latching on/off toggle; the Push Button switch-push, a momentary contact that closes only while held; and the SPDT Switch switch-spdt, a selector that routes a common terminal to one of two outputs. For a bank of switches in a single package, see the DIP switch on Arrays & Switches.

Actuating a switch

Every switch in de:volt is toggled by clicking it on the canvas while the simulation runs. A latching switch flips state and stays there; a momentary push button closes while you hold the click and re-opens when you release. You do not wire a separate signal to drive them — the click is the actuation.

Switch (SPST) — switch-spst

Single-pole single-throw: one contact pair that is either open or closed. It latches — once you flip it, it stays in that position until you flip it again — which makes it the right part for a power switch or a mode select that should hold its setting.

Pinout

On the breadboard footprint, the corners are top-left a, top-right b, bottom-left a2, and bottom-right b2. Pressing the button connects the left terminal (a/a2) to the right terminal (b/b2).

Parameters

Both are boolean and editable in the Inspector, so you can drop the switch in already closed, or turn it momentary if you want push-button behaviour from the SPST body.

Push Button — switch-push

A momentary tactile button: the contact closes while held and opens the moment you release. This is the standard way to give a microcontroller a manual input.

Pinout

Parameters

The pull-up / pull-down pattern

A bare button connects nothing to a digital input when it is open, leaving the pin floating — an undriven input that reads random noise. You fix that with a resistor that pins the input to a known level until the button overrides it. Two arrangements:

• Pull-up (most common): a 10 kΩ resistor from VCC to the input pin, with the button between the input pin and GND. At rest the resistor holds the input HIGH; pressing the button shorts it to GND so the input reads LOW. Note the inversion: pressed = LOW.
• Pull-down: a 10 kΩ resistor from the input pin to GND, with the button between VCC and the input pin. At rest the input is held LOW; pressing it reads HIGH.

The pull-up version is the classic layout:

VCC ─── 10kΩ ──┬─── MCU input pin
               │
            [button]
               │
              GND

On real hardware the metal contacts bounce for a millisecond or two as they make and break, producing a burst of fast transitions. A 100 nF debounce capacitor from the input pin to GND smooths that edge; in software you can instead wait a few milliseconds and re-read. Add the cap if your sketch is miscounting presses.

SPDT Switch — switch-spdt

Single-pole double-throw: one common terminal that is always connected to exactly one of two outputs, never both, never neither. It is the part for A/B signal routing or a two-way mode select.

Pinout

Parameters

The position parameter selects which throw is live and is editable in the Inspector; clicking the switch on the canvas flips it between the two throws. Because COM is always tied to one side, an SPDT makes a clean break-before-make selector — no moment where both outputs are joined.

Related parts

• Arrays & Switches — the multi-position DIP switch for setting several bits at once.
• LEDs — a button plus an LED is the canonical first interactive circuit.

New to placing and wiring parts? Start with Getting started.