Purpose of "sand" inside a solar charge controller - Page 1
Forum section: electronics / projects

author: DTJ
author_rank: Super Contributor
timestamp: April 17, 2019, 01:01:16 am
content: Have a look at this short video.https://www.youtube.com/watch?v=QzyZCdmQqH0&feature=youtu.beIt shows "sand" inside a sealed solar charge controller. I've read a few different opinions on why it is there:1) Heat transfer.2) Its not sand, its a polymer that helps to protect the electronics. Its also how it gets its IP65 rating.﻿Is there any truth in 2) above.Perhaps they just use it as a very cheap filler to save on the cost of the epoxy by only having to put a thin layer on top to seal the unit.Perhaps they want to avoid rigid epoxy over the thermally stressed parts to prevent fracturing as they thermally cycle.Anyone seen this before?

author: floobydust
author_rank: Super Contributor
timestamp: April 17, 2019, 01:10:16 am
content: Sand is a cheap filler in order to use less potting compound. It also helps extinguish any flames or sparks inside. I think it's just a cheap way to seal something big, chinese do that kind of thing.

author: Nusa
author_rank: Super Contributor
timestamp: April 17, 2019, 01:58:06 am
content: Plus there's the whole "Feel how heavy it is...there must be some beefy components in there!" thing! Most people don't open the box.

author: DTJ
author_rank: Super Contributor
timestamp: April 17, 2019, 05:28:43 am
content: Quote from: floobydust on April 17, 2019, 01:10:16 amYeah I think that as well.Quote from: Nusa on April 17, 2019, 01:58:06 amI reckon that's a side benefit. I've also seen products before that have a short length of black finish steel flatbar inside just to add that heavy "quality" feel.

author: TERRA Operative
author_rank: Super Contributor
timestamp: April 17, 2019, 07:53:24 am
content: Quote from: DTJ on April 17, 2019, 05:28:43 amMy Roku network video streaming thingo has a metal plate in it for this reason.Without the plate, it's a single PCB in a plastic box a bit bigger than the palm of your hand and hence weighs almost nothing.The plate adding weight does make it feel nicer, even though I know it is there exactly for that reason.

author: mikerj
author_rank: Super Contributor
timestamp: April 17, 2019, 11:36:34 am
content: Quote from: TERRA Operative on April 17, 2019, 07:53:24 amWeight is very useful for these small streaming boxes as HDMI cables are quite stiff so you'd never get the box to stay where you want it.

author: sanman
author_rank: Contributor
timestamp: April 17, 2019, 03:02:10 pm
content: I remember a lot of CB microphones had pieces of lead, or even rocks, inside to give them some 'heft'

author: JimRemington
author_rank: Regular Contributor
timestamp: April 19, 2019, 02:25:16 am
content: Adjust antenna for best reception.

author: AlienRelics
author_rank: Unknown
timestamp: April 19, 2019, 02:39:01 am
content: Not only that, it costs more for the model with an "antenna" than without.

author: Gyro
author_rank: Super Contributor
timestamp: April 19, 2019, 10:10:10 am
content: Quote from: floobydust on April 17, 2019, 01:10:16 amIf it's Silica sand then maybe itisthere as a cheap flame suppressor - turning the whole thing in into a sand-filled fuse. It would hardly help with IP65 rating - if moisture got in, the sand would get damp. It possibly lets them get away with a plastic, rather than metal, enclosure.

author: coromonadalix
author_rank: Super Contributor
timestamp: April 19, 2019, 10:21:06 am
content: In marine / boat transformers they are filled with sand to provide humidity and rust and salt water protection ??

author: MaTkEOxjC
author_rank: Contributor
timestamp: April 19, 2019, 11:26:13 am
content: I found a couple (like 20) neon sign transformers in the dumpster in Europe. The body of them was a mixture of sand and some resin (the actual transformer was surrounded by the resin/sand mix, giving it a sturdy cover, making it semi-waterproof (the lid was injection molded plastic with mains disconnect contacts but had no seal).Probably again to save resin with some nice side effects (more robust shell, less shrinkage when curing)Looks pretty much like the lower one of these:

author: tecman
author_rank: Frequent Contributor
timestamp: April 19, 2019, 03:20:46 pm
content: One note, sand is primarily a thermal insulator and not good for heat transfer. Think of a foundry casting steel using sand. Or at a beach under the sun, a few inches down is not hot.paul