Be careful when moving the cables around! Be super cautious not to over flex/bend any of the wires, it could totally break and that sucks! But if any of them do, you can re-solder your connections.

Adding the 8x8 LED Matrix

Before adding the LED matrix, add a black piece of tape to cover up the slot right below BMO's face. It's just for decoration, it doesn't actually do anything but adds a great finishing detail to make BMO look more like BMO.

Position the 8x8 LED matrix 'upright' by making sure the pin outs are at the top and adafruit logo at the bottom. Insert the LED Matrix into box with the top going in first, and then the bottom. The LED matrix should loosely fit into the BMO's box enclosure. Ensure the wiring in the pinout are positioned to the top.


Adding Push Button

Gently move the wiring of the LED matrix away from the top clips.

Slightly bend one of the pins of the push button inward, so it does not touch any part of the LED Matrix.


Insert one side of the button into the clips near the top of the box.  Align up the push button with the hole in the top middle. Apply pressure to the opposite side of the button while pushing the top of the box inward. This will make a slight bend allowing the push button to snap into place.


Add Gemma

Place GEMMA over the back of the box cover with the USB port aligned up to the bottom opening. Lightly press GEMMA down into the cover so it stays put.


Add the JST/Switch adapter to the GEMMA. Make sure two cables are not too long or else it won't fit inside the box!

Closing it Up

You will need to neatly fit the GEMMA, lipo battery and the JST/switch adapter into the box. For an easier build, try using a 110mAh lithium polymer battery (the 150mAh is a little more tricky to fit into the box, but it can be done!). Place the battery in between the Gemma and led matrix.

If the cover doesn't quite close, you may need to reduce the length of the battery cable and/or the JST/switch adapter. With patience, trial and error, you're box will nicely close shut with a little wiggle room.

Mounting JST/Switch adapter

Carefully adjust the cables and insert the switch through the cut out near the top of the box cover. If the wires are too long, you may need to cut off some slack so all the components fit inside the box.

Add the Finishing Details

If you have already, pop in the button pieces into the holes on the front of BMO's boxy box. If they don't fit, using an x-acto knife to loosen up the opening. Be careful, don't over loosen the holes or the limbs and buttons won't stay put! But if you do, you can super glue them into place. BMO's arms and legs should freely rotate.

Add a split ring to the cover and put it on a necklace to wear your new electronic pal for a 3d printed adventure time!

This guide was first published on Feb 20, 2014. It was last updated on Jul 16, 2024.

This page (Assembling BMO) was last updated on Feb 18, 2014.

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