Passive Arrays and Switches

This page covers two breadboard staples that pack several elements into one through-hole package: the resistor array (four matched resistors in a DIP-8) and the DIP switch (a configurable row of independent toggles). Both save space and wiring when you need the same thing repeated across several lines — pull-ups on a bus, current limiting for an LED bank, or a block of configuration straps.

Resistor array

The resistor array models a 4× isolated resistor network in a DIP-8 package. All four resistors share a single value (default 10 kΩ, set via the resistance property in the Inspector). The a pins sit on one side of the package and the b pins on the other — each a–b pair is a fully independent resistor with no common bus between elements.

Pinout

Each resistor connects exactly one aN to its matching bN. There is no internal connection between resistor 1, 2, 3, and 4.

Specs

Resistors are non-polarised, so either end of a pair can face the supply.

Isolated vs bussed

This part is the isolated type: four separate resistors with eight free pins. A bussed array instead ties one end of every resistor to a shared common pin (handy for a rail of pull-ups off a single VCC), but it costs you that flexibility. The isolated layout here lets each resistor go anywhere — pull-up on one line, series resistor on another — at the price of using both pins per element.

Typical use

• Pull-up / pull-down banks on I2C or SPI data lines, where every signal wants the same resistor to the rail.
• Current limiting for an LED array — one chip instead of eight loose resistors.
• Keyboard / button matrix lines that all need an identical pull resistor.

Because all four elements share the one resistance param, reach for the array only when the lines genuinely want the same value. Mixed values still need individual resistors.

Example circuit (I2C pull-ups)

        VCC (3.3 V)
         │   │
        a1   a2        ← resistor array (10 kΩ each)
         │   │
   [R1]──┘   └──[R2]
         │   │
        b1   b2
         │   │
   SDA ──┘   └── SCL ─── to MCU + I2C devices

Two of the four resistors pull SDA and SCL up to the rail; the other two pairs stay free for the next bus or LED bank.

DIP switch

The DIP switch is a classic red through-hole DIP switch with N independent SPST positions in one package — configurable from 2 to 8 positions (default 4). Each position simply connects its two pins when closed and opens the circuit when off. Click a rocker on the canvas to flip it, or drive each position from the sw1..swN property (0 = open, 1 = closed).

Pinout

(The default is a 4-position switch; setting positions higher adds more aN/bN pairs.) Each aN–bN pair is one isolated SPST contact — there is no common bus, so wire one side to your signal and the other to ground or a rail as needed.

Specs

The contacts are rated for low-level signal switching, not power. Do not run motor or relay coil current through them.

Typical use

• Address selection on I2C/SPI devices — set a chip’s bus address with a few rockers instead of soldering links.
• Mode jumpers and boot-configuration straps that you want to change without rewiring.
• Binary-coded inputs, where each closed switch contributes one bit to a value an MCU reads.

A switch on its own only opens or closes a connection — it does not produce a defined logic level. Pair each contact with a pull resistor (see the resistor array above) so an open switch reads a stable HIGH or LOW.

Example circuit (config straps)

        VCC (5 V)
         │
        10k  10k  10k  10k   ← pull-ups (resistor array)
         │    │    │    │
   D2 ───┴────┼────┼────┼──── (read by MCU)
   D3 ────────┴────┼────┼────
   D4 ─────────────┴────┼────
   D5 ──────────────────┴────
         │    │    │    │
        a1   a2   a3   a4     ← DIP switch
         │    │    │    │
        b1   b2   b3   b4
         └────┴────┴────┴──── GND

Each pin idles HIGH through its pull-up. Flip a rocker closed and that pin is tied to ground, reading LOW — a clean four-bit configuration the sketch can read at startup.