How to build a PAPRa m12 Battery Controller (Mar 2021)

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:

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.

Remove the support material:

Seat the Plate on the board:

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

Seat the board into the controller box:

Place the washers and nuts on the potentiometer and the power port at the base of the controller body:

Tighten all three nuts using the socket wrench, but not so tightly that components come off the board:

Place the light pipe onto the board:

Place the light pipe clip over the light pipe to hold the pipe in place:

Place the Knob onto the potentiometer, and twist to turn on. If there is a charged battery in the Controller, you should see the lights in the light pipe:

Test that everything works with a battery in the socket by making sure the lights turn on:

Snap the Lid in place. Note the orientation; snapping the lid in in the opposite orientation may cause the lower lip to break off:

Congratulations! You have built a Tetra PAPRa M12 Controller Box v3!