Understanding Resistors in PCBs

Resistors play a crucial role in limiting the flow of electric current within printed circuit boards (PCBs). They are essential passive components that help control the overall circuit behavior. While resistors do not have polarity, interpreting their values correctly is key to ensuring the functionality of the circuit.

Decoding Through-Hole Resistors

Through-hole resistors feature color-coded rings that provide valuable information about their resistance values. These rings come in various configurations, with the four-ring setup being the most common. In a four-ring resistor, the first two rings indicate the resistance value, the third ring shows the multiplier, and the fourth ring denotes the tolerance.

• Example: A resistor with red, red, silver, and gold rings translates to a resistance of 0.22 Ω with a tolerance of ±5%.

Reading Tips and Orientation

When reading the color code on resistors, always start from the side with more rings and move towards the side with fewer rings. The first ring is typically positioned near one of the leads, while the last ring signifies the tolerance level.

Deciphering SMD Resistors

SMD resistors use coding systems like the three-digit, four-digit, and EIA-96 systems to convey resistance values. In these systems, the initial digits represent the resistance value, while the following digits indicate the multiplier.

• Example: The code “54B” in the EIA-96 system signifies a resistance value of 3570 Ω with a ±1% tolerance.

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