How to build a PAPRa m12 Battery Controller (April 2024)

The Tetra Powered Air Purified Respirator requires power to function, and the m12 battery controller provides that power for these models. The controller consists of internal circuitry, a potentiometer to adjust fan speeds, a cable to connect to the fan box, and a port for a Milwaulkee M12 Battery to be inserted.

This build differs from the v1 version in that it uses a custom-built circuitboard to remove many of the difficult steps of the build, add a battery charge indicator, and a separate power port for use in a car. If you cannot get the custom board, then please refer to the v1 version of this guide.

WARNING: we provide no warranty, implicit or explicit, that this device will work up to an N95 specification, when built outside of a facility rated to do so. The only way to truly test one of these devices using something like a Portacount under controlled conditions.

This build will require printed parts, purchased parts, and several tools. Here is a picture of all the components used in this build:

And the assembly diagram can be found here. Note that this assembly calls for version 0.7 of the board.

These parts should be printed at 0.2 spacing:

You will need these components. Prices fluctuate, and so are not included here. Alternative versions can be sourced, and we welcome edits for tested alternatives.

These tools are recommended. URLs are for tools purchased and used in the building of the prototypes:

Building this version of the controller is more a matter of ensuring that the Controller Box was printed cleanly and all support material is properly removed.

Attach Light Panel to body (unless using fully transparent one piece body):

Place the printed circuit board assembly battery leads into Plate:

Place the printed circuit board assembly with Plate into the Body:

Place washer over the power port, then finger tighten a hex nut over the same power port to hold the Plate in place:

Put the lid onto the body:

Place washer over BNC jack, then finger tighten a hex nut over the same BNC jack:

Place washer over potentiometer, then finger tighten a hex nut over the same potentiometer:

Use socket wrench to tighten hex nuts into place:

Attach 2X MOLLE spacers onto MOLLE strap:

Attach and screw MOLLE strap (with spacers) onto lid with M4 screws using a hex screwdriver:

Attach and secure MOLLE Catch onto MOLLE Strap and Lid with M4 screws using hex screwdriver:

Attach knob onto potentiometer:

Insert m12 battery:

Turn knob to turn on power (it should beep and flash an LED battery level indicator):

Test m12 battery controller with fan box by attaching a BNC cable:

Congratulations! You have built a Tetra PAPRa M12 Controller Box v4 (August 2021)!