Parts
| 1× | 12 V LED strip W/m × metres from the label (warm white 2700 to 3000 K) |
| 1× | 12 V adapter ≥ strip amps × 1.25 (BIS registration number on the label) |
| 1× | DC jack pigtail 5.5 × 2.1 mm, centre + |
| 1× | Red/black twin wire 0.75 mm² (1.5 mm² for 5 A) (socket-to-strip distance) |
| 1× | Second wire pair same size (far-end feed, 5 m runs) |
| 2× | Heat-shrink sleeve 3 to 5 mm |
| 1× | MOSFET, logic-level IRLZ44N (not IRFZ44N) (dimming only) |
| 1× | Resistor 330 Ω gate + 10 kΩ pull-down |
| 1× | Arduino UNO/Nano or 12 V in-line PWM dimmer one of the two |
| 1× | Clip-on TO-220 heatsink small (above about 4 A) |
| 1× | Aluminium channel strip width (high-output strips) |
Wiring
| Adapter plug (centre +) | → DC jack pigtail |
| Jack + | → red wire → strip + |
| Jack − | → black wire → strip − (no dimmer) |
| Strip − (with dimmer) | → MOSFET drain |
| MOSFET source | → jack − (short, thick wire) |
| D9 | → 330 Ω → MOSFET gate |
| MOSFET gate | → 10 kΩ → GND |
| Arduino GND | → MOSFET source (own wire) |
| Strip far end + / − | → second pair → jack (5 m runs) |
Steps
| 1 | Read the strip's label | Check: Strip watts written on the card |
| 2 | Size the adapter | Check: Adapter amps above strip amps × 1.25 |
| 3 | Choose the wire from adapter to strip | Check: Wire loss from the table under 0.5 V |
| 4 | Cut the strip only on the marked pads | Check: Both cut ends show half a copper pad |
| 5 | Join the wires | Check: About 12 V at the far end with the strip lit |
| 6 | Feed long runs from both ends | Check: Near and far ends look equally bright |
| 7 | Dim it, with code or without | Check: Strip off at power-up, full at 255, dim at 64 |
| 8 | Check the heat, then fix it in place | Check: After 30 min, MOSFET and adapter warm, not hot |
Tests
| Measure | Expect | Got |
|---|
| W/m ___ × m ___ ÷ 12 × 1.25 | adapter amps needed: ___ | |
| Adapter output, strip unplugged | about 12 V | |
| Far end of the strip, lit | at least 11.5 V | |
| Drain to GND at analogWrite 255, 2 A | about 0.05 V | |
| MOSFET and adapter after 30 min | warm, not too hot to hold | |
