47 kΩ resistor color code

Where you'll meet it

Reading a 12 V solar panel on an Arduino

An Arduino's A0 pin measures 0 to 5 V, but a 12 V solar panel gives far more than that in sunlight. Two resistors scale it down: 47 kΩ from the panel's plus to A0, then 10 kΩ from A0 to ground.

V_out = 28.5 V × 10 kΩ / (47 kΩ + 10 kΩ) = 5.0 V

So the most A0 can read, 5 V, stands for 28.5 V at the panel. A 12 V panel reaches about 22 V in full sun with nothing drawing from it, so it fits with room to spare.

The pair draws at most 28.5 V / 57 kΩ = 0.5 mA, nothing next to what the panel gives in daylight.

At full scale the 47 kΩ resistor turns 23.5 V × 0.5 mA ≈ 0.012 W into heat, so any ¼ W part is fine.

The drawing shows only the panel's plus wire: its minus must connect to the Arduino's GND. Some cheap charge controllers switch the minus wire, so check that the panel's minus really is your ground before you join them. In code, multiply the voltage at A0 by 5.7 (57 kΩ / 10 kΩ) to get the panel's voltage; resistor tolerances shift it by a few percent, so check once against a meter. Seen from the pin, the pair looks like about 8.2 kΩ, under the 10 kΩ the Arduino's analog input is designed for.

On SMD parts

Look for 473 or 4702

• 473473 = 47 × 10³ = 47,000 Ω (3-digit code).
• 47024702 = 470 × 10² = 47,000 Ω (4-digit code, usually ±1% parts).

There is no EIA-96 code, because 47 kΩ is not an E96 value (the nearest E96 values are 46.4 kΩ and 47.5 kΩ).

Check it with a meter

Read 44.65–49.35 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 47 kΩ this matters: two fingers on the leads can pull the reading down.
4. Anything from 44.65 to 49.35 kΩ is a good ±5% part. A 5-band ±1% part should read 46.53 to 47.47 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.