For our demo we're keeping it simple with two low cost Trinkets + neopixel strips that share the same data pin. However, this is just to get you started! Customize your own helmet with your own designs. You can also upgrade to a Pro Trinket which has way more flash space for more complex designs.
Follow the illustration above as a reference for wiring the components. The trinket micro-controller is wired to the neopixel strip using a Y connection. Each strip is sharing a single connection to the trinket's data, power and ground pins.
This switch is only for about ~500mA of current (so only maybe 10 or 20 LEDs on at once). If you want to have way more LEDs and higher draw, please use this switch which is rated for 2 Amps
In this circuit diagram, you will need to solder a JST female connector to the bottom of the Trinket where the postive+ and negative- terminals are exposed.
The NeoPixel Strip IN pin is wired to D0 on Trinket. Postive+ pin on NeoPixel Strip is wired to BAT pin on Trinket. The Negative- pin on the strip is wired to GND pin on Trinket.
Shorten a JST extension cable to about 10mm long by cutting the positive and negative cables with wire cutters. Use wire stripers to strip the ends of the positive and negative wires. Apply a bit of rosin to the stripped ends and tin the tips of the wires. Add a piece of shrink tubing to the negative wire and solder them together by holding them in place with a third-helping-hand.