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ArjinFerman  Tinfoil Gigachad  4d ago (text post)   347 thread views

Tinker Tuesday for May 6, 2025

This thread is for anyone working on personal projects to share their progress, and hold themselves somewhat accountable to a group of peers.

Post your project, your progress from last week, and what you hope to accomplish this week.

If you want to be pinged with a reminder asking about your project, let me know, and I'll harass you each week until you cancel the service

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OK my stuff from mouser.com arrived w.r.t. my LED project.

I got charged a tariff!

I ordered $5.00 worth of MOSFETs. I saw a line item that said $1.50 in tariffs. If they came from China, and they were anticipating a 145%ish tariff on these items, aren't they telegraphing that their wholesale price for the MOSFETs was $1.00? Seems kind of not that big a deal. If I were a retailer I might simply hide this cost rather than give away proprietary business info like my wholesale costs this way.

Anyway!

My next biggest stumbling block with my LED lighting project for my bikes and bike accessories is coming up with adhesion. For the helmets I think I want to use double-sided tape but I'm concerned it won't hold. My experience with gluing/sticking things has historically been lousy, although I do note that Tesla Model 3 and Model Y license plate holders are stuck to the front with sticky tape so I assume it's possible. I'm eyeing 3M double-sided "very high bond" tape though not holding out a lot of hope.

If that doesn't work, or if I'm dealing with surfaces that are more porous, the next best thing might be to get LED sleeves that are more like tracks with a cover and try to rivet or staple them into the surfaces instead? Thinking of my cargo bike box here.

Thoughts?

VHB is ridiculously strong when used on properly prepared surfaces; I've bent 1/8th inch aluminum plate trying to remove two stuck together with three 8-inch strips of the stuff without solvents. The trick is figuring out what 'properly prepared' means -- 90% of the time just dunking in simple green and rinsing with water works, but heavily polished or painted and almost all rubberized materials can benefit a lot from primer, and I'd expect helmets will fall into this domain.

Most other double-sided tape is either garbage (carpet tape) or won't last very long under exposure (basically every foam mounting tape).

Rivets are a great option in most situations you can make them fit, but alignment can be a pain without kliecos. I don't recommend staples. Epoxy is a mess, but it's really strong and there exist mixtures that will secure to most everything, at the cost of never coming off period. For obvious reasons I'd keep all three but especially the staples away from helmet pieces.

The other constraint to keep in mind is what you're sticking in place; it doesn't help to just have adhesive and the PCB strip well-secured and the LEDs flopping in the wind. Those sleeves have an advantage here, though even the floppy ones might have too large a minimum bend radius. Expect to mix-and-match.

The trick is figuring out what 'properly prepared' means -- 90% of the time just dunking in simple green and rinsing with water works, but heavily polished or painted and almost all rubberized materials can benefit a lot from primer, and I'd expect helmets will fall into this domain.

What about rubbing alcohol on the shiny (not foamy) parts of a bike helmet?

Isopropyl alcohol's worth a shot first, before trying to use primer. Beyond that, depends a lot on the plastic and coating; most bicycle helmets are ABS that I'd expect it would bind fine, perhaps benefiting from a bit of heat. Higher-end ones that are using carbonfiber, or scratch-resistant polycarbonate, I'd expect you'd want the primer.

The higher ends of gorilla tape can handle those cases if you don't want to deal with (or can't get, thank you California) the primers, but I haven't gotten any experience with how weatherproof it gets.

thanks!

how do you know so much about this stuff?

VHB specifically, I've volunteered for FIRST FRC a lot, and it's one of the go-to adhesives in that realm (and most teams get free spools of it), so I've gotten a lot of hands-on experience.

WS2812s, I ran a few different STEM outreach projects using them. They're great as a way to teach and show for loops in physical space, but the constraints are very easy to run into, even with Adafruit's documentation.

Circuit assembly work in general has just been a hobby. I think it's a really important skillset, but also one that's very badly underserved by mainstream college training courses.

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