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Archive for July 29th, 2019

Astable Multivibrator Blinkies: Radome Attachment

Ping-Pong ball radomes tend to fall off their perches at the slightest touch:

RGB LED - radome test
RGB LED – radome test

Because I planned to take my collection along to HV Open’s Mad Science Fair, I finally used a Round Tuit for some adhesive action.

The general plan was to punch a ring from double-sided tape, thusly:

Astable - Radome adhesive - poor surface
Astable – Radome adhesive – poor surface

The OD required touching up the edge of a brass tube punch I’d made a while ago:

Astable - Radome adhesive - punch sharpening
Astable – Radome adhesive – punch sharpening

It worked exactly as expected:

Astable - Radome adhesive - punching
Astable – Radome adhesive – punching

Unfortunately, the 3D printed spider’s “spherical” socket has such a rough surface that the adhesive had too few contact points to hold the ball in place.

My fallback has become 3M outdoor-rated double-stick foam tape, so:

Astable - Radome adhesive - 3M foam tape
Astable – Radome adhesive – 3M foam tape

This leaves a small black ring visible between ball and socket. Recessing the foam tape by half its thickness should improve its ahem optics, although it’s probably not worth the effort with black PETG.

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