My garage door has a T handle on the front that, when turned, extends arms on the door into square holes on the garage door rails, locking the door in place. The garage door opener doesn't know this, though, and will still try and open the locked door if triggered.

To fix this, I designed this switch to bolt to the outside of the rail where the sliding lock extends. When the door is locked, it depresses the switch, which is wired to the garage door opener's interlock terminals, preventing it from triggering.

Technical Details

The switch triggers when depressed by about 5mm, and allows for 23mm of total travel. It travels smoothly without binding, even if force is applied off-center to the plunger.

Parts Needed

• A D2F-L microswitch or similar (one with a straight lever arm).
• A spring; I used a 23/64" x 1-3/8" (around 34mm x 8.5mm) spring from Harbor Freight
• Two 10-24 nuts and bolts (the slots in the housing were designed for 3mm tall nuts)
• Six #4 x 5/8" sheet metal screws, also from Harbor Freight
• Two M2x10 self-tapping screws (for the microswitch

Building

I printed this in ABS, though any material should work. I recommend printing the plunger part with its “ears” on the build plate and the hole for the spring facing the side; this makes the layer lines for the housing and plunger perpendicular, so they should slide easily without binding.

1. Do a test-fit of the plunger and housing, making sure the plunger slides freely back and forth. You'll probably have to trim the plunger edges, particularly if printing with a brim.
2. Insert the microswitch into the square hole on the inside of the housing. The lever arm should point away from where the plunger rests. You may have to trim down some material to make it fit, depending on how the print went.
3. Using the two access holes, secure the microswitch using the M2x10 self-tapping screws
4. Insert the plunger into the housing. You'll need to depress the microswitch lever to do so.
5. Install the spring into the hole in the back of the plunger.
6. Put the cover plate onto the housing, making sure the spring sits on the cone that's on the cover plate.
7. Secure the cover plate using the six sheet metal screws.
8. Insert the two 10-24 nuts into the pockets on the housing.