Resistor
220 Ω, 1 kΩ, 10 kΩ…
Limits current and divides voltages. The most common component in any circuit. The value is read from colour bands on the body.
Open the course →How it works
Ohm's law: I = U / R. More resistance → less current. Three main roles in the projects: (1) current limiting for LEDs (220 Ω); (2) pull-up/pull-down — holds a pin at a defined state (10 kΩ); (3) voltage divider — makes 3.3 V from 5 V (1 kΩ + 2 kΩ), or reads an LDR/thermistor.
Pins and wiring
| Pin | What it is | Where it connects / why |
|---|---|---|
| End 1 | No polarity | Can be turned either way. |
| End 2 | No polarity | — |
Specifications
Power1/4 W (standard for breadboards)
Tolerance±5 % (gold band) or ±1 % (brown)
Colour → digitblack 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9
Reading 4 bandsdigit · digit · multiplier · tolerance
220 Ωred · red · brown (×10)
1 kΩbrown · black · red (×100)
10 kΩbrown · black · orange (×1000)
4.7 kΩyellow · violet · red
Tips and typical mistakes
- You cannot "burn" it with an ESP32 — 1/4 W is more than enough for every project here.
- No 220 Ω? 330 Ω or 470 Ω also work, the LED will just be a bit dimmer.
- A multimeter on Ω is the fastest way to check a value if you cannot read the colours.