56 kΩ resistor color code

Where you'll meet it

A button on an ESP32 input-only pin

On the ESP32, pins GPIO34 to GPIO39 can only be inputs, and unlike the other pins they have no built-in pull-up or pull-down resistors. A button on GPIO34 therefore needs its own: the button connects 3.3 V to the pin, and a 56 kΩ resistor from the pin to ground holds it at 0 V while the button is up.

I = 3.3 V / 56 kΩ ≈ 0.059 mA

Button up: no current flows, the resistor holds the pin at 0 V and it reads LOW.

Button down: the pin is at 3.3 V and reads HIGH. Only 0.059 mA flows, and the resistor turns 3.3 V × 0.059 mA ≈ 0.0002 W into heat, so any ¼ W part is fine.

Wire the button to 3.3 V, never 5 V: ESP32 pins are not made for 5 V. On a 5 V Arduino the same resistor would pass 5 V / 56 kΩ ≈ 0.089 mA.

Any value from about 10 kΩ to 100 kΩ works as a pull-down here. A larger one wastes less current while the button is held; a smaller one holds the pin more firmly against noise on long wires. This is the original ESP32: newer chips such as the ESP32-S3 number their pins differently, and the S3 has no input-only pins like these. A real button also bounces for a few milliseconds when pressed; handle that in code.

On SMD parts

Look for 563 or 5602

• 563563 = 56 × 10³ = 56,000 Ω (3-digit code).
• 56025602 = 560 × 10² = 56,000 Ω (4-digit code, usually ±1% parts).

There is no EIA-96 code, because 56 kΩ is not an E96 value (the nearest E96 values are 54.9 kΩ and 56.2 kΩ).

Check it with a meter

Read 53.2–58.8 kΩ

1. Take the resistor out of the circuit.
2. Set the meter to Ω, range 200 kΩ (or auto).
3. Touch one probe to each lead. Keep your fingers off the metal: your body is a resistor too. At 56 kΩ this matters: two fingers on the leads can pull the reading down.
4. Anything from 53.2 to 58.8 kΩ is a good ±5% part. A 5-band ±1% part should read 55.44 to 56.56 kΩ.

A meter has a small error of its own, so a reading a hair outside the range does not prove the part is bad. Measure again with firm contact before you swap it.