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.

We recommend to use a heatsink and have good airflow around the Power Expander.

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 W1209 thermostat

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 30V DC)

Signal_in 5 to 24V DC

Signal_in and power_in are galvanically isolated.

Maximum power current up to 60A peak

Maximum recommended DC current 20A (Heatsink required and fan cooling)

Board outline 30X30mm

Mounting holes 22X22mm (Ø3.2mm)

Please note that the Power Expander is unfused.

Datasheet for the driving MOSFET: PSMN7R0-30YLC.

Design files

PowerExpander_bottom_mirrored.pdf

PowerExpander_bottom_silk_mirrored.pdf

PowerExpander_outline.pdf

PowerExpander_top.pdf

PowerExpander_top_silk.pdf

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. Then apply solder to the INVERTED pads. In this mode the output is switched on until voltage is applied to the Signal input terminal.

To restore normal operation reconnect the "NORMAL" solder jumper by applying some solder and remove the solder previously applied to the "INVERTED" solder jumper.

(please avoid scenarios where both solder jumpers are either shorted or open, this will cause the Power Expander to remain indifferent on input changes, hence it will stay in either on or off mode - in other words rendered pretty much useless until you toggle one of the solder jumpers.)

For additional info, please see reprap.org/wiki/Power_Expander

FAQ

Q: What is the maximum amount of Watts that can be operated via a single Power Expander?

A: The maximum rating of the SMD Mosfet (the flat square black thing with four legs on one side, the thing that is actually doing the switching on and off) will tolerate up to 60 Ampere for a very brief moment, however under continuous load conditions we recommend that you do not exceed 20 Ampere. This amount largely depends on environment conditions and if you find the PCB is getting hot and the Mosfet is way too hot to touch please read on.

Please note that the Power ratings for the Power Expander output depend on the relationship of Ohm's law: Voltage x Amperage = Wattage.
Therefore at a system voltage of 24 Volt the Power Expander can handle more power than on a 12 Volt system.

Q: What should I do if I need to draw more than 20 Ampere or  if my current Power Expander is running hot?

A: If your application needs more current we suggest you couple two or more Power Expanders in parallel so that they can share the load current.

Q: Could you please list some examples of operating conditions?

A: Sure, here is a list of  examples of operating conditions:

Example 1: a 12 Volt system operating a 1.2 Ohm heated bed will draw 10 Ampere and consume 120 Watts of power
12V / 1.2Ω = 10A and 10A x 12V = 120W

Example 2: a 24 Volt system operating a 1.2 Ohm heated bed will draw 20 Ampere and consume 480 Watts of power
24V / 1.2Ω = 20A and 20A x 24V = 480W

Example 3: a 24 Volt system operating a 2.4 Ohm heated bed will draw 10 Ampere and consume 240 Watts of power
24V / 2.4Ω = 10A and 10A x 24V = 240W

Example 4: a 24 Volt system operating a 4.8 Ohm heated bed will draw 5 Ampere and consume 120 Watts of power
24V / 4.8Ω = 5A and 5A x 24V = 120W