Monsieur Adaptateur is an adapter which adapts between different plug formats you'll encounter when prototyping circuits on 2 channels.

Using Monsieur Adaptateur, you can interconnect the following standard connectors:

  • DC Jack 2.1mm (like on your Arduino)
  • 2mm Jacks (for Multimeter probes)
  • 4mm Jacks (for your regular banana jacks)
  • BNC Connector
  • Terminal Block (up to 1.5mm²/16AWG)
  • Scope probe connector
  • Standard 6 pin 0.1" female header
  • Standard 6 pin 0.1" male header
  • 4.75 and 6.3mm blade connectors (FastOn)
  • Maximum Voltage: 12V DC (see the FAQ for additional information)
  • Maximum Current: Depending on connector, see board silkscreen

You can choose between different case colors: black (opaque polystyrene), grey (opaque polystyrene), red (translucent ABS) and blue (translucent ABS).

Assembly is pretty easy, you only need a soldering iron, a wrench for the banana jacks (pliers would also work) and a Philips screwdriver. I also made assembly instructions, see the documentation.


The upper half of the PCB is the first channel (usually GND) and the lower half is the second channel (usually positive or negative signal).

The rings of the BNC and DC connectors are connected to the first channel. That's the most common usage – however, sometimes manufacturers put positive voltage on the outer ring on the DC connector.

Application ideas (besides the obvious):

  • Connect a DC Jack, plug your multimeter test leads into the 2mm jacks and verify that the polarity of the DC jack is what you expect (sometimes DC Jacks have the positive terminal on the outside of the connector)


  • Why didn't you use larger screw terminals?

Initially I wanted to do that, however, I've found that the 5mm screw terminals often lose cables with smaller diameter (I usually use 0.14mm²/26AWG). The screw terminals I use now support up to 1.5mm²/16AWG, which is also about the maximum I ever used for prototyping.

  • Why only 12V DC?

The maximum rated voltage for the whole board is 12VDC, because that's what the DC connector is rated at. If you buy a kit, you may decide to skip the DC connector in order to gain more safety at higher voltages. The PCB itself has an isolation gap of 1mm, which is fine for higher voltages – I recommend a maximum of 30V DC without the DC connector, so bad things won't happen if you touch the contacts. But again, I am not liable if you exceed my recommendations. See the documentation link for a full list of all connectors with their voltage/current ratings.

  • The 2mm connectors aren't a tight fit!

I thought so, too, until I realized that it wasn't the connectors – it was my multimeter probes, which were only 1.85mm in diameter! My authentic fluke multimeter probes were 1.99mm in diameter, and those where a good fit.