LED Array / Matrix Calculator

When you need more than one LED, the wiring topology matters. In a series chain, all LEDs share the same current, and the forward voltages add up. The supply must exceed the total forward voltage, and a single resistor sets the current for the whole string. This is the most efficient approach when the supply voltage is high enough.

Parallel LEDs should never share a single resistor. Even LEDs from the same batch have slight Vf differences, and the exponential V-I curve of a diode means a tiny voltage difference causes a large current imbalance. The LED with the lowest Vf hogs the current, heats up, its Vf drops further, and thermal runaway can destroy it. Always use one resistor per LED (or per series string) when wiring in parallel.

A series-parallel matrix combines both: you wire the maximum number of LEDs in series per string (limited by Vsource / Vf), then run as many parallel strings as needed to reach the total count. Each string gets its own current-limiting resistor. This is how commercial LED strips and sign modules are designed — it minimizes total current while keeping supply voltage practical.

Key Points

• Series: same current through all LEDs, forward voltages add up
• Parallel: each LED (or string) must have its own resistor
• Never share a resistor between parallel LEDs — thermal runaway risk
• Matrix: maximize series count per string for best efficiency
• Leave at least 1–2V headroom for the current-limiting resistor
• Total power = Vsource x total current (includes resistor losses)

Applications

• LED strip and tape light design
• Signage and display backlighting
• Automotive LED clusters and brake lights
• Arduino and microcontroller LED projects
• Grow light arrays and UV curing panels
• Indicator panel and dashboard lighting