Overview
This project repurposes a Tevo Tarantula heated bed into a standalone PCB preheater using an Arduino Mega 2560 and an MKS Base v1.4 (12 V / 24 A) controller.
It is designed for electronics rework, not solder reflow. The purpose is to evenly warm PCBs (approximately 80–120 °C) so soldering and hot-air work becomes faster, safer, and less stressful on components.
The controller is fully self-contained and does not use Marlin firmware or G-code.
What It Does
The preheater provides gentle, even heating across an entire PCB before rework. This reduces thermal shock, lowers the amount of hot-air required, improves solder flow on large ground planes, and shortens overall rework time.
It also gives old 3D-printer hardware a genuinely useful second life.
Hardware Used
Core electronics:
Arduino Mega 2560
MKS Base v1.4 (12 V, 24 A rated)
RepRapDiscount Smart Controller (20×4 LCD, rotary encoder, buzzer)
Heating and sensing:
Tevo Tarantula aluminium PCB heated bed (12 V)
Original bed thermistor
Reused hotend thermistor as a work / surface probe
Power and cooling:
12 V / 24 A power supply
12 V fan connected to the MKS Base FAN output
Why the MKS Base v1.4
The MKS Base v1.4 already provides everything needed for this project:
A high-current MOSFET for the bed
Screw terminals rated for heater current
A fan MOSFET output
Thermistor inputs with correct pull-ups
Native Arduino Mega pin compatibility
This allows proven printer hardware to be reused directly, without firmware overhead.
Features
Heating control:
Bang-bang control with hysteresis
Heater always boots OFF for safety
EEPROM-saved temperature setpoint
Dual temperature monitoring:
Bed temperature used for control and safety
Work temperature representing the actual PCB surface
User interface:
Rotary encoder for temperature adjustment
Short press toggles heating on or off
Long press triggers an immediate panic stop
20×4 LCD with fixed-width rendering to avoid wrap glitches
Feedback and safety:
Buzzer alerts for power-on, heating activity, setpoint reached, and timeout
Automatic one-hour unattended shutdown
Thermistor fault detection
Over-temperature shutdown
Automatic board cooling fan control
Wiring Notes
The heated bed connects to the BED screw terminal on the MKS Base.
The bed thermistor is connected to analogue input A13.
The work thermistor is connected to analogue input A15.
The cooling fan connects to the FAN screw terminal.
Power is supplied through the main 12 V input terminals.
Note: the FAN output is low-side switched. The fan always has 12 V present, and the MOSFET switches ground. This is normal behaviour.
The RepRapDiscount Smart Controller wiring follows standard MKS / RAMPS Arduino Mega pin mappings. If the controller works with Marlin’s REPRAP_DISCOUNT_SMART_CONTROLLER configuration, it will work here.
Safe Temperature Guidance
This device is a preheater, not a hot plate.
Typical usage:
Light boards: 80–90 °C
General rework: 90–110 °C
Heavy multilayer boards: 110–120 °C
Hardware limits:
Continuous safe operation is around 110–120 °C
Short, supervised use up to approximately 130 °C is acceptable
Higher temperatures are unnecessary and place extra stress on the PCB heater.
Calibration Notes
Infrared thermometers often read low on bare aluminium due to emissivity. For accurate IR measurements, use matte black tape or marker on the surface.
The work probe will usually read lower unless it is taped down with good thermal contact. This is normal and reflects the real PCB temperature rather than the heater temperature.
LCD Layout
Line 1 shows bed temperature and work temperature.
Line 2 shows the target setpoint.
Line 3 shows heater and fan status.
Line 4 shows guidance or fault messages.
All lines are fixed-width to prevent display glitches.
Safety Behaviour
The heater never auto-starts on power-up.
A long button press immediately shuts the heater down and clears the target.
Thermistor faults force the heater off.
Over-temperature conditions force the heater off.
If left unattended for one hour, the heater automatically shuts down.
The system is designed to fail safe.
Possible Enhancements
PID control for tighter temperature regulation
Preset temperature slots (80, 90, 100, 110 °C)
Soft ramp or soak modes
Automatic cooldown timer
Insulation or enclosure under the bed
Final Notes
Many people have retired 3D printers with usable beds and electronics but no obvious reuse path. This project gives that hardware a second life as a practical and genuinely useful bench tool for electronics work.
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