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Bendy SAO

A poseable PCB assembly depicting an inflatable car wash tube balloon man

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Going for a variant of my "Articulated PCB" (aka "Bendy Boards") project from several years back (https://github.com/geekmomprojects/ArticulatedPCBs), but with a new design that (hopefully) works as an SAO for SuperCon 2024. It may or may not come together in time, but should definitely be in contention for the "least manufacturable" SAO prize!

This design is a flexible assembly comprised of two layers of PCBs which can pivot while maintaining electrical contact through spring-loaded pressure connectors on one side and circular contact pads on the other. It's basically an assembly of PCB slip-rings, with addressable LEDs that will display animation patterns along the full length of the assembly, no matter how the constituent boards pivot and bend.

The SAO can work with *either* a badge communicating through the SAO connector on the back, or  with a XIAO/QTPy or other pin-compatible microcontroller through a connector on the front side. The SAO connector provides Gnd, VCC, Signal (Through GPIO1) to control the twelve WS2812 compatible LEDs. An attached XIAO board can control the Bendy SAO through Pin D2 (RP2040 GPIO28) and provide power through the USB C port.

Micropython code for a badge or XIAO is available at https://github.com/geekmomprojects/BendySAO/tree/main/code/BADGE_micropython

I built a successful proof-of-concept a few years back: https://github.com/geekmomprojects/ArticulatedPCBs, but wanted to try to make it more fun this time, so the assembly of boards now takes the shape of an inflatable car wash balloon man, and the LEDs are mounted inside the assembly, to illuminate it from the inside.

BendySAOBufferLayer.svg

Outlines to be cut from 1.6mm thick acrylic to form buffer layers between the opposing PCBs in the assembly. They are not symmetric. Orientation matters.

svg+xml - 7.08 kB - 11/03/2024 at 19:39

Preview

BackTop2024-10-12.zip

x-zip-compressed - 37.00 kB - 10/12/2024 at 05:50

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FrontBase2024-10-12.zip

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BackCenter2024-10-12.zip

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BackBase2024-10-12.zip

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  • Preparing to Assemble the Assembly

    debraansell10/23/2024 at 21:40 0 comments

    Once the components were attached to the boards, the two layers of boards had to be sandwiched together with the spring contacts pressing against the circular solder pads. 

    A push rivet goes through the corresponding holes in the two layers to align them and allow them to pivot. The push rivet needs to be the correct height to hold the layers against each other firmly so they don't separate, but aren't too close either. A buffer layer sits in the middle of the opposing PCBs so that the spring contacts aren't crushed. The working height of the spring contacts is about 1.8 mm, so I used 1.6mm laser cut acrylic to create a buffer layer in a shape that doesn't overlap the components. In addition, male header pins hold opposing components together, so I needed to find male header pins with an insulation layer no more than 1.6 mm thick. I found these at DIgiKey.

  • SMT Assembly

    debraansell10/23/2024 at 21:39 0 comments

    Prototype boards came back from JLC, The side-emitting LEDs have tiny solder pads, so I ordered stencils along with the boards for the first time. Amazingly, the solder paste stenciling and SMT soldering worked quite well for the first few boards, and I seem to have routed all the connections correctly. I haven't used these specific LEDs before, but I like the way the attached lens diffuses the light.

  • Quick and dirty JLC prototype order

    debraansell10/12/2024 at 06:12 0 comments

    Submitted prototype (and possibly final as I doubt there will be enough time for iteration) designs to JLC PCB for 6 different boards (front base, front middle, front top, back base, back middle, back top) to comprise a bendy assembly. Working under a time crunch, I'm focusing on keeping things as simple as possible, so I added pads to mount a XIAO 2040 (only $3!) on the front base, to easily program patterns on the LEDs in CircuitPython. The image below shows two columns of boards, with front layer on left and back layer on right. Each column contains one base, two middle and one top board.

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Discussions

Hakaday wrote 10/24/2024 at 13:18 point

Very cool!  Video please, for those of us unable to make SuperCon...  :)

  Are you sure? yes | no

debraansell wrote 10/25/2024 at 00:47 point

Thank you! Preliminary video here (https://photos.app.goo.gl/LkdSwAg5Psr5CFGQ9), but I will be taking better video and photos soon

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davedarko wrote 10/12/2024 at 09:16 point

oh I look forward to seeing this one! :)

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