Power Expander

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Power Expander

Release status: Working

Power Expander
CAD Models
External Link

The Power Expander

...is a versatile electronics adapter for 3D printer heatbeds, hotends, fans and other high current demanding equipment.

The Power Expander is based on MOSFET technology, hence no relay contact switching or associated EMC noise, leading to increased long term durability.

Use cases

Add a heated build platform to an Ultimaker 3D printer


If you are building a larger 3D printer you might want to attach multiple heated printbeds (connections shown here with Ultimaker electronics)


Driving a heating element together with a Heatbed Temperature Controller

PowerExpander W1209.png

Ideas for possible uses:

  • fans
  • lighting
  • automatic conveyor belt
  • motors
  • incubators
  • heated magnetic stirrers
  • ...

In general anything that draws DC current from a voltage in between 12 and 24 Volt DC can be driven by the Power Expander

The Motivation

Lots of 3D printer electronics does have the ability to drive only a few power consuming devices at one time, for instance a hotend, a heatbed and usually a small fan. Still there's normally a lot of general I/O pins left for extra functionality. These pins however usually can only handle small currents up to 20 milliampere. Most equipment require driving currents well beyond this limit, hence the need for an adapter capable of administering these larger currents.

Technical specifications

Power handling designed for 12 to 24V DC (absolute maximum 32V DC)

Signal_in 5 to 24V DC (absolute maximum 32V DC)

Signal_in and power_in are galvanically isolated.

Maximum power current up to 60A peak (unfused)

Board outline 30X30mm

Mounting holes 22X22mm (Ø3.2mm)

Please note that the Power Expander is unfused.

Datasheet for the driving MOSFET: PSMN7R0-30YLC.


PowerExpander sch.png

PowerExpander pcb.png


PDF files for printing and toner transfer: File:PowerExpander files.zip

Eagle files are available at RepRap.me

Custom configuration

Solder pads are located on the rear side, these are intended for optional invertion of the operation mode. By factory default the Pad designated NORMAL is shorted by a small trace between the solder pads. In this mode the output is turned off until voltage is applied to the Signal input terminal. For inverse operation, first cut the small trace between the solder pads designated NORMAL (it can later be shorted by applying some solder). Then apply solder to the INVERTED pads. In this mode the output is switched on until voltage is applied to the Signal input terminal.

Where to get it

Power Expander at reprap.me

Development history

PCB Outline

The PCB outline is based on the Sick of Beige PCB from Dangerous Prototypes but the size that I wanted wasn't in the library so I made my own version of the library with a 10mm increments all the way from 20X20mm to 150X150mm with both unplated and plated mounting holes.

PowerExpander All sizes small.png

Download the Eagle library here: File:Reprap.me sick of beige all sizes.zip

Rev. 1

PowerExpander-2-front.jpg PowerExpander-2-back.jpg


PowerExpander-1-front.jpg PowerExpander-1-back.jpg

The PCB for the prototype was made on the LPKF Protomat_C60 PCB milling machine in Labitat.