Controlling a MaxxFan over Ethernet

I bought a MaxxFan Deluxe model 00-05100K fan to install in my 1989 Winnebago LeSharo. I noticed that it has an RJ45 connector — commonly known as an ethernet connector — on the circuit board, and wondered what it was used for, but I couldn't find any useful info about it on the internet.

I thought it would be interesting to be able to control the fan with a microcontroller or a custom remote, so I took the fan apart and started investigating.

The process of the investigation is documented in this video:

MaxxFan Ethernet Port Wiring

The wires on the ethernet port1 are connected directly to the wires on the button panel of the fan, and can be used to duplicate the commands of the buttons by connecting two of the wires.

Using standard RJ45 pin wiring numbers, with 1 being on the left side when the bump is down, the wiring is as follows:

ButtonPins
Up6, 8
Down5, 8
Auto4, 7
In/Out5, 7
On/Off6, 7

The MaxxFan Deluxe models 00-07000K and 00-07500K also include an auto-open feature that is triggered by simultaneously triggering both the Up and Down buttons.

There are other MaxxFan models with different button panels, such as the MaxxFan Plus model that has a Rain Sensor button on its control panel. If you are aware of any wiring differences on other models, let me know and I will update this post to reflect those.

Electronics

To determine the wiring of the connector, I took apart the fan and inspected the circuit board and control panel.

  • Controlling a MaxxFan with an ESP8266 microcontroller
    Controlling the fan with a microcontroller.
  • MaxxFan Control Panel, lit from back
    The traces in the control panel are visible when backlit.
  • MaxxFan Circuit Board Top.
  • MaxxFan Circuit Board Bottom

I had success using a simple NPN transistor circuit to control each button. This can be wired as follows, using a resistor to connect the signal wire to the base pin, and is detailed in the video above.

Transistor as a switch

I used an 2N2222 transistor with a 1kΩ 1/4 watt resistor.

I haven't tested this personally, but I believe another good option would be to use a MOSFET Trigger Switch Board to do this. They are affordable and include screw terminals that would make the connection to the switched device easy.

These boards are designed for higher loads and can drive lights or motors with PWM signals, but I believe they can be used as a simple switch too, as it is basically a more robust version of the schematic above. I believe you would wire one side of your switch to the negative input, and the other side to the negative output, as the ground side of the circuit is switched.

Trigger Switch Board Diagrams

Products

  1. I am using the term "ethernet" because it is known colloquially, but of course the fan does not use the ethernet protocol, but rather simply utilizes the cable and RJ45 connector because it's a cheap and easy way to get an eight-wire connection.↩︎