PAGE 121 OF 150 · POWER SUPPLIES & BATTERIES
Choosing a Battery for LED Projects
Capacity in mAh sets how long an LED runs.
LED SYMBOLTriangle points from anode to cathode; the arrows show light leaving the part.
Questions to ask
- What voltage does the circuit need?
- How much current does it draw, and for how long?
- How big and heavy can the pack be?
- Should it be rechargeable?
Quick guide
- Two AA or three AAA cells, 3 to 4.5 V: simple LED lights.
- 9 V battery: light loads only, because capacity is small.
- Coin cell: tiny, low current.
- Lithium-ion cell: high capacity, 3.7 V, needs a charger and protection.
Choose capacity in milliamp-hours from your current and run-time target.
REMEMBER
Pick voltage first, then capacity.Try it yourself
Sketch the circuit on paper first, calculate the values, then build it on a solderless breadboard using a low-voltage supply. Measure with a multimeter before you make anything permanent.
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