Protecting a cable entry point from dust/insect ingress - Page 1
Forum section: electronics / projects

author: 5U4GB
author_rank: Super Contributor
timestamp: July 08, 2025, 09:42:01 am
content: This is for a home project, not work-related so doesn't have to be professional-grade: I need to terminate a bunch of existing cables with connectors on them in a plastic enclosure in a shed. Because of the connectors I can't just push the cables through a grommet, and really don't want to chop them up and crimp/solder on new connectors. So it'll need an oversized set of holes in the case to admit the connectors and then some way of closing them up to just the size of the cable (think something like an RJ45 through the hole, then seal around the Cat5 behind it).Two options I thought of is (1) make t-shaped cuts into some butynol, push the cable up the base of the t into the cross-piece with the flaps of butynol pressed into place along the cable, glue onto the case, and (2) drill holes for the grommets into a piece of ABS, slice it in half through the centre of the holes, drop in the grommets and cables on one half and screw or glue the two halves into place on the case, so a sort of DIY Cablefix or similar seal at a tiny fraction of the price.Does anyone have any better ideas? So far I'm tending towards (2) because it'll give a better seal and is removable if I ever need to replace something later.

author: Phaseseeker
author_rank: Regular Contributor
timestamp: July 08, 2025, 09:46:10 am
content: Split cable glands do exist, for example the Icotek QVT series. Not the cheapest option though

author: 5U4GB
author_rank: Super Contributor
timestamp: July 08, 2025, 12:13:44 pm
content: Yeah, all the commercial ones are pretty overkill both in terms of what I'm after, maybe IP4x, and cost, I was more after alternative low-tech ideas that are more or less OK.

author: Ian.M
author_rank: Super Contributor
timestamp: July 08, 2025, 12:35:35 pm
content: For (2), if you cut after drilling you get undersize out-of-round holes!. To avoid this, slice the ABS in half (or use two pieces) and clamp them firmly together *BEFORE* drilling, and take care to drill as exactly as you can into the joint plane. With a smear of silicone caulk on all mating surfaces, and enough cross fixings between the cables to keep the two parts from bowing, it is likely to do the job, and if mounted from the inside of the case, isn't even noticeably fugly!However I am concerned that you may attempt to seal the enclosure too well, and with the expected temperature variation in an outbuilding, are likely to get moisture sucked in through the seals (or even down the cables if they aren't gel filled) leading to condensation buildup inside the enclosure and eventual flooding. If you gasket the lid, you probably need an insect-proof drain at the lowest point, or at the very least a Goretex vent to keep the interior pressure near ambient.

author: Terry Bites
author_rank: Super Contributor
timestamp: July 08, 2025, 12:53:36 pm
content: I used silicone gunk for my antenna cable entry holes.Good enough for Australia.

author: David Hess
author_rank: Super Contributor
timestamp: July 08, 2025, 03:02:07 pm
content: I would likely use foam sealant, which is easy to remove if necessary. If I needed to stop mice, then I would fill the gap with steel or copper wool and then use foam sealant.

author: ConKbot
author_rank: Super Contributor
timestamp: July 08, 2025, 03:10:35 pm
content: For semi-permanent/serviceable, the commercial solution would be "plug duct seal" called "monkey shit" in the trade. Wouldn't really provide retention for the cable, just sealing. Not sure how visible your location is, but for that it would be get the putty, and pack the cable in place. If you need rodent resistance, maybe involve some stainless steel wool in the mix.

author: 5U4GB
author_rank: Super Contributor
timestamp: July 09, 2025, 05:08:31 am
content: Quote from: Ian.M on July 08, 2025, 12:35:35 pmI'd already thought of that one, this isn't even remotely airtight, there's wiggle room between several of the grommets and the cables, just hopefully not enough to let ants in. Here's the initial test entry point, for the Ethernet cable:In the end I went with a clear case (probably PP, definitely not ABS) because there's a lot of blinkenlights to monitor, or at least to check that something hasn't silently failed. It's very much DIY'd but looks reasonably presentable overall. And I didn't take a photo of the other one with the multiple cables going in because that's slightly less clean looking.The cut was made with a 0.3mm Japanese razor saw, it's probably very marginally out of round but give that the flexible grommet fills the space anyway it's not noticeable.

author: jamesglanville
author_rank: Contributor
timestamp: July 09, 2025, 07:27:52 am
content: https://www.screwfix.com/p/vimark-nylon-male-comp-glands-20mm-black-2-pack/651vtSomething like that might let an RJ45 squeeze through, if you disassemble it and get the connector through piece by piece. Even if you have to really squeeze/deform the gland to get the connector through it's still likely to be pretty waterproof.

author: 5U4GB
author_rank: Super Contributor
timestamp: July 09, 2025, 08:40:39 am
content: The PGx's only have a few mm of clamping ability, you can get PG-something's that'll pass an RJ45 and PG9's that'll clamp Cat5, but not in the same unit.A waterproof seal is also slight overkill for what I'm after, I just need something to keep insects and general dust out.

author: Stray Electron
author_rank: Super Contributor
timestamp: July 09, 2025, 11:37:48 pm
content: Many years ago when I used to install Telco equipment we used a smelly putty-like substance called monkey shit. I don't know what the real name of the stuff was but Nothing seemed to affect it and no insect ever came near it. You can probably use Google and find out what the real name of the stuff was and what they sell in your country, But I'll leave you with this:https://en.wiktionary.org/wiki/Appendix:Glossary_of_U.S._Navy_slang

author: ipt555
author_rank: Newbie
timestamp: July 10, 2025, 05:21:30 am
content: It depends on the actual connectors you're working with, but AliExpress has reasonable affordable gland solutions for RJ45 connectors which can be installed after the connector is fitted, e.g.:https://www.aliexpress.com/item/1005004493093835.html. These are intended as inline couplers, but it wouldn't be too hard to adapt them to just use their bodyshell part with panel mount part of a PG series gland.Essentially they work by having the bodyshell be large enough that the connector can pass through, and then using a large, split sealing ring which slips over the cable and compresses down to make a seal, covering the difference (scroll down on that listing, there's a good exploded picture). The sealing ring is made of some sort of foam which has a slightly self-amalgamating character, which I guess helps with the sealing.I don't know that I'd trust them to IP68, but IP44 ought to be easily achieved.

author: BradC
author_rank: Super Contributor
timestamp: July 10, 2025, 10:06:09 am
content: When I have to penetrate a bulkhead with multiple cables/hoses and larger connectors I glue a conduit into the bulkhead. Feed all of the bits through it, tie a string around a rag and stuff that to pack as tightly as possible with the string hanging out, then put half an inch of silicone in the end as a plug. When I inevitably have to make changes I pull the string and the rag pushes the silicone plug out.Modify and replace as required.

author: Ian.M
author_rank: Super Contributor
timestamp: July 10, 2025, 11:44:33 am
content: A rag and string free variant is to bundle the cables, well gunked with sealant to fill the gaps, then wrap with self-amalgamating tape to bring the diameter up to something that will fit a single off the shelf gland big enough to get the connectors through one by one, starting from the biggest on assembly and visa versa on disassembly. With care and appropriate choice of sealant and self-amalgamating tape, IP68 is achievable. Even with an improvised split block and sealant gland IP66 is pretty easy.