LED Driver Design with Arduino
Worked for 21 mins
Blocked: your account has no available ACUs, so I can’t continue executing tools right now.
Accomplished:
- Resolved the Arduino Nano
VINERC by markingVINas intentionally unused; the Nano is powered from5V_CTRL. - Searched for the exact OSRAM
GW CPSRM1.PM; it is not currently available in the Flux library, so I kept the closest available OSRAM 700 mA LED stand-in and submitted a missing-part request. - Selected and applied
SMMS0650-680Mas the real 68 µH shielded inductor candidate for L1–L5, using the closest valid footprint option. - Set the board to 140 × 90 mm, 4-layer stackup, and placed the LEDs as 5 horizontal rows of 3 LEDs, with each driver channel beside its row.
Open items:
- Need to rerun ERC/DRC after ACUs are available to confirm the VIN issue is clean and check placement.
- The exact
GW CPSRM1.PMstill needs to be imported/created from a datasheet if you want exact BOM/footprint fidelity. - High-current trace-width/layout rules still need to be applied; the last layout-rule call was blocked by a selector issue before I could correct it.
Suggested next steps:
- Re-run ERC/DRC and fix any new placement/footprint issues.
- Import/create the exact OSRAM
GW CPSRM1.PMpart from its datasheet. - Apply high-current net trace-width rules and thermal copper guidance.
- Route the PCB after confirming the LED row placement.
Create LED part
Run ERC/DRC
Set trace rules
Review BOM
Finish verification
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Ask about this doc
Design Notes — Arduino 15-LED Constant Current Driver
Architecture
- Input: 24 V DC through J1, F1 PTC protection, D_PROT1 TVS, and C_BULK1 bulk capacitance.
- LED array: 15 total LEDs as 5 independent strings, 3 LEDs in series per string.
- LED drivers: U1–U5 HV9967B PWM-dimmable buck constant-current LED drivers, one per string.
- Control: U_MCU1 Arduino Nano V3 drives U1–U5 PWMD pins from PWM-capable pins D3, D5, D6, D9, D10.
- Control power: U_REG1 24 V to 5 V buck regulator powers the Arduino 5 V rail.
Power Budget
Per LED string at 700 mA:
- Typical LED voltage: 3 × 2.83 V = 8.49 V.
- Typical LED optical/electrical load: 8.49 V × 0.7 A = 5.94 W.
- Worst-case LED string voltage: 3 × 3.2 V = 9.6 V.
- Worst-case LED load: 9.6 V × 0.7 A = 6.72 W.
Total LED load:
- Typical: 5 × 5.94 W = 29.7 W.
- Worst-case LED load: 5 × 6.72 W = 33.6 W.
- With ~85–90% driver efficiency and Arduino/control overhead, specify a 24 V supply rated at least 2 A minimum, preferably 24 V / 3 A or larger. A 24 V / 4–5 A supply gives startup and thermal margin.
Current Setting
HV9967B current set equation from datasheet:
I_LED = 0.25 V / R_CSSelected
R_CS = 0.36 Ω, giving:I_LED ≈ 0.25 / 0.36 = 0.694 AUse 1% tolerance, ≥0.5 W current-sense resistors.
LED Driver Channel Mapping
Table
| Channel | Driver | LEDs in series | PWM pin | Sense resistor | Inductor | Catch diode |
|---|---|---|---|---|---|---|
| CH1 | U1 | LED1, U6, U7 | D3 | R_SENSE1 | L1 | D1 |
| CH2 | U2 | U8, U9, U10 | D5 | R1 | L2 | D2 |
| CH3 | U3 | U11, U12, U13 | D6 | R2 | L3 | D3 |
| CH4 | U4 | U14, U15, U16 | D9 | R3 | L4 | D4 |
| CH5 | U5 | U17, U18, U19 | D10 | R4 | L5 | D5 |
Important BOM Notes
- Exact requested LED
OSRAM GW CPSRM1.PMwas not available in the Flux library. The schematic usesGW CSSRM2.EM-M9N1-XX56-1-700-R18as an OSRAM 700 mA 3-pad SMD stand-in. Replace with the exact GW CPSRM1.PM component/footprint before manufacturing if footprint or thermal pad differs. - L1–L5 are generic 68 µH placeholders. Select real shielded power inductors with saturation current comfortably above peak inductor current, recommended ≥1.2 A.
- U_REG1 support components should be verified against the final LMR50410 datasheet/layout guide before PCB release.
Thermal Requirements
Each LED dissipates roughly 2 W at nominal current. Total LED heat is about 30 W typical and can exceed 33 W at high forward voltage.
Minimum recommendations:
- Mount LEDs on aluminum-core PCB or heavy copper LED board, or provide large thermal copper pours and vias into a heatsink.
- Use thermal interface material between LED board and heatsink.
- Design heatsink for total LED dissipation with airflow assumptions; do not rely on FR-4 alone for 15 high-power LEDs.
- Keep LED junction temperature comfortably below datasheet maximum; target case/heatsink temperature that leaves junction margin at worst-case ambient.
Safety / Layout Notes
- Keep 24 V LED power loops short and wide.
- Place each driver’s Schottky diode, inductor, sense resistor, and VDD bypass capacitor close to its HV9967B.
- Use a solid common ground, but route high-current switching returns away from Arduino/control signal return paths.
- Route PWM lines away from switch nodes CHx_SW.
Architecture
Power Budget
Current Setting
LED Driver Channel Mapping
Important BOM Notes
Thermal Requirements
Safety / Layout Notes
