Mounting circuits in a wood box - Page 1
Forum section: electronics / projects

author: paulskiogorki
author_rank: Newbie
timestamp: July 17, 2018, 12:01:37 pm
content: HiI'm new here, a woodworking hobbyist dabbling in adding electronics to some projects.I have some Qi wireless charging components, and looking for advice on a couple of things. I am mounting the components basically inside a small wooden box, on the underside of the 'lid' of the box.The PCBA I have looks just like the linked one.https://www.aliexpress.com/item/DIY-Wireless-Phone-Charger-PCBA-Circuit-Board-Coil-Micro-USB-Port-DC-5V-Qi-Standard-Universal/32838102206.htmlMy questions:- suggestions for best way to mount the coil/magnet and circuit board? Glue? I have some double sided 3M tape meant to hold photos to walls etc. Have also tried PL glue, but would like something easier to 'undo' for troubleshooting.- In my design the LED light attached to the board will stay inside the box and I'd like to run a light conducting material from it to the edge of the box exterior. I have experimented with strips of acrylic and thin fiber optics I got from a hobby shop, with mixed results. Specifically, is there a good way to attach or bond the light conducting materials to the LED? Like with wrapping tape around it or a dab of CA glue or something?- Is it safe to bend the prongs the LED is mounted to, and if so by how much? 90 degrees etc...?Separate questions on obtaining components:- I've had the best luck on AliExpress finding the components. Is there somewhere better?- I've also been looking for USB flash drives with a plain metal sleeve, i.e. no case, but haven't had much luck. Suggestions?Thanks for reading.Paul

author: Ian.M
author_rank: Super Contributor
timestamp: July 17, 2018, 12:25:51 pm
content: I see at least one mounting hole in the board. Just put a screw through the mounting hole with a fibre washer under the head to protect the board. If its got components on the back you may need a short standoff cut from plastic tubing. You may need to add a batten beside each edge to stop the board twisting if you only use one mounting hole.There's no good way to attach a light guide to a LED without a custom plastic clip to hold them together. It has to fit properly in the first place and be secured to the case, and if the board and light guide are both properly fastened to the case you don't need a clip anyway. I'd avoid clear silicone or epoxy or similar unless you want to do a lot of experimenting to get the correct geometry for the interface. Superglue is a non-starter because the fumes will 'frost' nearby surfaces.You can bend the LED leads ONCE at any position along them through at least 90 degrees. However you mustn't bend them within 3mm of the board or LED, or apply significant force to the LED body or solder joints.N.B the charging coil itself must be as close as possible to the lid top surface to minimise the distance to the device. You should probably rout a recess, epoxy it in then plug the recess to restore strength to the top.

author: KL27x
author_rank: Super Contributor
timestamp: July 18, 2018, 01:39:24 am
content: Best glue that is undoable is hotmelt. Sanded, unfinished wood will hold fine until you add a little alcohol to release it. Then it'll peel right off. Just don't expect the glue to release if the wood is left really rough.I'll hot glue just about anything/everything while refining, tuning, debugging. And lots o times, hot glue is a perfectly good final solution.

author: paulskiogorki
author_rank: Newbie
timestamp: July 18, 2018, 01:41:27 am
content: Thanks for your reply. You mean like a glue gun when you say hot melt?

author: KL27x
author_rank: Super Contributor
timestamp: July 18, 2018, 01:43:06 am
content: Yeah.Other caveat: If the two surfaces you glue together are very large, one or both surfaces has to have a little bit of flexibility (like a circuit board). If you glue two large things which are super rigid, good luck prying them apart.

author: paulskiogorki
author_rank: Newbie
timestamp: July 18, 2018, 01:44:37 am
content: Thanks for the detailed reply Ian.As far as mounting, I have been shying away from screws because I am mounting to the same board as the coil, which is slightly less than 4mm thick, to allow proper charging. I'll experiment with some small wood screws, but I think I would want at least two because the little board takes a fair bit of force when the cable is plugged and unplugged.

author: Ian.M
author_rank: Super Contributor
timestamp: July 18, 2018, 03:43:18 am
content: In that case, groove two battens for the the edges of the PCB, glue them to the lid, slide the board in and lock it in place with a couple of short dowels that are a push-fit through cross-holes in the battens to trap the corners of the board.

author: paulskiogorki
author_rank: Newbie
timestamp: July 18, 2018, 12:09:18 pm
content: Ah, that's a good idea. I'll try that in my next iteration.Incidentally, thefiberopticstore.com recommends using heat shrink tubing to fasten fiber optic cable to LED. I'll give that a try too.

author: Ian.M
author_rank: Super Contributor
timestamp: July 18, 2018, 12:41:34 pm
content: Another option would be to 3D print a plastic base plate the board clips into, similar to that provided with genuine Arduino Uno boards. With the baseplate screwed or glued to your box lid, one screw could then positively retain the charger board.The problem with heatshrinking a fibre optic cable to a LED is the very poor match between the LED beam pattern and the acceptance angle of the end of the fibre optic cable - even if its one of those large diameter cheap plastic ones. It would work better with a Pespex rod light guide that's a similar diameter to the LED.