Resin Roller Pro

A motorized resin bottle roller / mixer built around the MKS Gen L V1.0 3D printer controller board (ATmega2560). Two stepper motors spin a pair of rollers that gently tumble epoxy resin bottles to keep the mix homogeneous, with a simple three-button interface and addressable LED status strip.

CAD model (OnShape): Open in OnShape

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CAD Gallery

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Features

• Three operating modes selected by coloured push-buttons
  • Red — Emergency stop (immediate motor kill + red LED flash)
  • Yellow — Continuous rolling at half speed (1.5 RPM)
  • Green — Timed alternating direction: 8 s forward → 8 s reverse, loops indefinitely
• Smooth exponential speed ramp — no abrupt starts or stops (τ = 400 ms)
• Hardware step generation via Timer1 CTC ISR — cycle-accurate timing, decoupled from the main loop
• Direct port writes on step pins (PORTF) for ~125 ns pulse width; supports up to ~500 kHz step rate
• Addressable LED strip (5 × WS2812B) with per-mode effects
  • Idle: slow blue breathing
  • Yellow: solid yellow
  • Green: animated green wave that sweeps with motor direction
  • Stop: 3× red flash
• Cooling fan on D9, active whenever motors are enabled

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Hardware

Component	Details
Controller	MKS Gen L V1.0 (ATmega2560)
Motor drivers	TMC2209 (or compatible) × 2, configured for 256 µsteps
Motors	NEMA 17 (1.8°, 200 steps/rev)
LED strip	WS2812B × 5, connected to D3
Buttons	Normally-open, wired to X+/Y+/Z+ endstop headers (INPUT_PULLUP)
Fan	12 V cooling fan on D9

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Wiring Summary

Buttons

Button	Colour	MKS Header	Arduino Pin
Stop	Red	X+	D2
Half speed	Yellow	Y+	D15
Timed cycle	Green	Z+	D18

Motors

Motor	Function	STEP pin	DIR pin	EN pin
X driver	Roller 1	54 (PF0)	55	38
Y driver	Roller 2	60 (PF6)	61	56

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Software

Dependencies

Library	Version
FastLED	^3.10.3

Build & Flash

Requires PlatformIO.

# Build
pio run

# Upload
pio run --target upload

# Serial monitor (115200 baud)
pio device monitor

Configurable Parameters

All tuning constants are at the top of src/main.cpp:

Constant	Default	Description
MOTOR_STEPS_PER_REV	200	Steps per revolution (200 for 1.8°, 400 for 0.9°)
MICROSTEP_COUNT	256	Must match MS1/MS2 jumper setting on driver
REDUCTION_RATIO	1.0	Motor revs per roller rev (1.0 = direct drive)
FULL_SPEED_ROLLER_RPM	3.0	RPM in green timed mode
HALF_SPEED_ROLLER_RPM	1.5	RPM in yellow continuous mode
GREEN_DIRECTION_TIME_MS	8000	Milliseconds per direction in green mode
ACCEL_TAU_MS	400	Exponential ramp time constant (ms)

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Architecture Notes

Stepping is handled exclusively by the Timer1 CTC ISR — the main loop only updates the speed target and direction. This separation means:

• Step pulse timing is cycle-accurate regardless of main-loop duration
• LED animations, button debounce, and ramp calculations run freely in the main loop
• A direction change ramps the motor to zero first, flips DIR, then ramps back up

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License

MIT — do whatever you want with it.