Hi, 

this is a small LED incicator for pull cords to see if the device is ON or OFF.
I used this for a herater on the diaper-changeing table.

Hope it helps to prevent leaving the heater on and burning our house down.

BOM:

Push Button Switch: TRU Components TC-R13-529BLRT
Cell: V13GA / LR44 (1.5V) 2X
Nickel strip
Screw :M3 10mm with hexagon socket

Instrucktions:

Print both sides: print side of LED to the ground, no support needed
Cut small overhang support on print with cutter (where the nickel strip will go)
Connect one LED pin to the switch pin and bend them 90° to fit (see picture)
Bend the other side as well
Create the nickel strip
Put the pull cord in place
Last but not least: Screw This!