MOSFETs Table
This page documents the MOSFET outputs available on Smoothieboard and their specifications.
MOSFETs are used to control high-power devices like heated beds, hotends, fans, and other accessories.
MOSFET Specifications
| MOSFET Pair |
Big MOSFETS |
Small MOSFETS |
Mixed MOSFETS |
|
|
|
| Label on diagram |
P2_7 |
P2_5 |
P2_4 |
P2_6 |
P1_23 |
P1_22 |
| Digital output pin |
2.7 |
2.5 |
2.4 |
2.6 |
1.23 |
1.22 |
| Power Input |
Between P2_7 and P2_5 |
Between P2_6 and P1_23 |
Taken from VBB |
|
|
|
| Size |
Big |
Big |
Small |
Small |
Big |
Small |
| Maximum current |
12A |
12A |
3A |
3A |
12A |
3A |
| Used by default for |
Heated bed |
|
Hotend 0 |
Fan |
Hotend 1 |
|
Understanding MOSFET Pairs
Smoothieboard has three MOSFET pairs:
Big MOSFETs Pair (P2_7 and P2_5)
- Current capacity: 12A each
- Power input: Shared between the two outputs (between P2_7 and P2_5 terminals)
- Typical use: Heated bed (high current devices)
- Note: Both outputs share the same power input
Small MOSFETs Pair (P2_4 and P2_6)
- Current capacity: 3A each
- Power input: Shared between the two outputs (between P2_6 and P1_23 terminals)
- Typical use: Hotend 0 and fan (moderate current devices)
- Note: Both outputs share the same power input
Mixed MOSFETs Pair (P1_23 and P1_22)
- Current capacity: P1_23: 12A, P1_22: 3A
- Power input: Taken directly from VBB (main power supply)
- Typical use: P1_23 for Hotend 1, P1_22 for accessories
- Note: These outputs use the main VBB power supply
Important Safety Notes
Current Limits: Do not exceed the maximum current ratings. Big MOSFETs can handle up to 12A, small MOSFETs up to 3A. Exceeding these limits can damage the board.
Shared Power: MOSFETs in the same pair share their power input. Make sure your power supply can handle the combined load of both outputs in a pair.
Configuration
To configure a MOSFET output in your config file, use the appropriate pin number from the “Digital output pin” row.
Example for configuring a heated bed on P2_7:
temperature_control.bed.heater_pin 2.7
Example for configuring a hotend on P2_4:
temperature_control.hotend.heater_pin 2.4