Treadmill Illumination PCB

→ to GitHub project folder

A two-channel LED driver board for near-infrared (NIR) illumination of the spherical treadmill in the “Integrated Inexpensive Treadmill”. Each channel independently drives four NIR LEDs in series from a 12 V supply, with a trimmer potentiometer per channel for brightness control. The circuit contains no ICs and no PWM, brightness is set resistively and therefore flicker free. This also keeps assembly straightforward and the adjustment stable between sessions.

Circuit

12 V DC enters through a barrel jack. Each of the two independent channels connects a trimmer and a current-limiting resistor in series with four NIR LEDs. Adjusting the trimmer changes the effective resistance in the chain and therefore the LED current and brightness. Because the two channels share only the supply, each lamp cluster can be set independently. Three M2 mounting holes allow the board to be attached to the newest iteration of the integrated inexpensive treadmill.

Bill of materials (v1.1 THT build)

Reference	Component	Value
J1	DC barrel jack	5.5/2.1 mm THT
D9–D16	NIR LED, 3 mm THT	4 per channel
R3, R4	Resistor, axial THT	120 Ω
RV3, RV4	Trimmer potentiometer	Bourns 3005, 25 turns

SMD alternative (DNP in v1.1)

The PCB also carries footprints for a surface-mount build. In v1.1 these are marked DNP (do not populate). Do not populate both variants on the same channel.

Reference	Component	Notes
D1–D8	NIR LED, 1206 SMD	4 per channel
R1, R2	Resistor, 0805 SMD	1 kΩ
RV1, RV2	Trimmer	Bourns 3386C, single-turn: coarse adjustment

Production files

production/v1.1/ contains the current fabrication package for this revision: Gerber ZIP, BOM CSV, component placement CSV, and IPC netlist, formatted for JLCPCB. Ordered from project “Treadmill Illumination” as W2026062323003684 on 2026-06-23.

production/v1.0/ contains the earlier revision with a panel ZIP and IPC netlist only. Walking-Setup/Inexpensive-Treadmill_Assembly/Inexpensive-Treadmill_Assembly.html