22 kΩ resistor color code

Where you'll meet it

Reading a car's voltage on an Arduino

With the engine running, a car's 12 V system sits at about 14.4 V, far above the 5 V an Arduino's analog pin can take. A 22 kΩ resistor from the car's 12 V to pin A0 and a 10 kΩ resistor from A0 to ground scale it down.

V_out = 14.4 V × 10 kΩ / (22 kΩ + 10 kΩ) = 4.5 V

With the engine off, 12 V becomes 12 V × 10 kΩ / 32 kΩ = 3.75 V. The pin would reach its 5 V limit only at 16 V, so the sketch multiplies its reading by 3.2.

The pair draws 14.4 V / 32 kΩ = 0.45 mA from the car.

The 22 kΩ resistor turns 9.9 V × 0.45 mA ≈ 0.004 W into heat, so any size will do.

A car's wiring also carries short spikes far above 14.4 V when big loads switch, so a real car project protects the pin as well, for example with a zener or clamp diode; it is left out here to keep the drawing simple. The Arduino's GND must connect to the car's ground. Resistor tolerances shift the reading by a few percent, so check it once against a meter.

On SMD parts

Look for 223 or 2202

• 223223 = 22 × 10³ = 22,000 Ω (3-digit code).
• 22022202 = 220 × 10² = 22,000 Ω (4-digit code, usually ±1% parts).

There is no EIA-96 code, because 22 kΩ is not an E96 value (the nearest E96 values are 21.5 kΩ and 22.1 kΩ).

Check it with a meter

Read 20.9–23.1 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.
4. Anything from 20.9 to 23.1 kΩ is a good ±5% part. A 5-band ±1% part should read 21.78 to 22.22 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.