# What size resistor do I need for my LED?

## What size resistor do I need for my LED?

LEDs typically require 10 to 20mA, the datasheet for the LED will detail this along with the forward voltage drop. For example an ultra bright blue LED with a 9V battery has a forward voltage of 3.2V and typical current of 20mA. So the resistor needs to be 290 ohms or as close as is available.

## What is the size of a 1/2 watt resistor?

Axial Resistor Sizes

Power rating | Body length (l) | Body diameter (d) |
---|---|---|

Watt | mm | mm |

1/8 (0.125) | 3.0 ± 0.3 | 1.8 ± 0.3 |

1/4 (0.25) | 6.5 ± 0.5 | 2.5 ± 0.3 |

1/2 (0.5) | 8.5 ± 0.5 | 3.2 ± 0.3 |

**How do I know what resistor to use with LED?**

We’ll use the following formula to determine the resistor value: Resistor = (Battery Voltage – LED voltage) / desired LED current. For a typical white LED that requires 10mA, powered by 12V the values are: (12-3.4)/. 010=860 ohms. To use several LEDs in parallel, sum the current values.

### How big is a 2 watt resistor?

Resistors – 2 Watt, Metal Oxide, Power

Body Length | 15.0 mm |
---|---|

Item Diameter | 5.0 mm |

Lead Diameter | 0.78 mm |

Lead Length | 35 mm |

Operating Temperature (TJ) | -55°C to 240°C |

### What resistor do I need to drop 12v to 5V?

12v to 5v converter using a voltage divider: Components required: One 12v battery, 1.8k resistor, 1.3k resistor, connecting wires.

**How big is a 1206 resistor?**

3.2 mm × 1.6 mm

Chip Resistor Sizes

ROHM Part No. | Chip Size (Length x Width) | inch |
---|---|---|

***10 | 2.0 mm × 1.2 mm | 0805 |

***18 | 3.2 mm × 1.6 mm | 1206 |

***25 | 3.2 mm × 2.5 mm | 1210 |

***50 | 5.0 mm × 2.5 mm | 2010 |

#### What size are resistors?

The most common through-hole resistors come in an axial package. The size of an axial resistor is relative to its power rating. A common ½W resistor measures about 9.2mm across, while a smaller ¼W resistor is about 6.3mm long. A half-watt (½W) resistor (above) sized up to a quarter-watt (¼W).

#### What watt resistor do I need?

Carbon resistors, for example, are commonly made in wattage ratings of 1/8 (0.125)W, 1/4 (0.250)W, 1/2 (0.5)W, 1W, and 2 Watts. Generally speaking the larger their physical size the higher its wattage rating….The Resistor Power Triangle.

Type | Power Rating | Stability |
---|---|---|

Wirewound | High up to 500 Watts | High 1% |

**What are the different types of wirewound resistors?**

Axial Cemented Fusible Leaded Wirewound Safety Resistors Wirewound Resistors, Commercial Power, Silicone Coated, Axial Lead Carbon Film Resistors, General Purpose, High Voltage Molded and Insulated Wirewound Power Resistors Axial Leads High Stability Resistor Chips (< 0.25 % at Pn at 70 °C during 1000 h) Thick Film Technology

## What are the different types of resistors?

Metal Film Resistors, Military/Established Reliability, Hermetically-Sealed, MIL-PRF-55182 Qualified, Precision, Type RNR, Characteristics E and C High Ohmic Value (up to 1.5 GOhm), High Power Resistors (up to 10 W at 25 °C) Thick Film Technology High Ohmic Values (up to 100 GΩ), High Voltage Resistors (up to 50 kV) Thick Film Technology

## What is the maximum ohmic value of a thin film resistor?

High Ohmic Values (up to 100 GΩ), High Voltage Resistors (up to 50 kV) Thick Film Technology Low Value (0.03 Ohm to 10 Ohm) Thin Film Resistor, Surface Mount Chip

**How do you calculate the resistance of an LED light?**

The formula to calculate resistance in a circuit is: R=V/I or, more relevant to what we’re doing: (Source Volts – LED Volts) / (Current / 1000) = Resistance*. So if we have a 12v battery powering a 3.5V 25mA LED our formula becomes: (12 – 3.5) / (25 / 1000) = 340ohms.