How do magnetic phone mounts work? - Page 1
Forum section: electronics / general

author: ThunderZed
author_rank: Regular Contributor
timestamp: April 17, 2025, 05:56:02 pm
content: Definitely a basic question for you but I can't tell if I received a defective one or if I'm just too clueless with technology to make it workI've just boughtthis magnetic mountboth for Motorola Moto G34 and my Samsung Galaxy S6, and neither of them charges wirelessly (no magsafe). The mount consists of a magnetic ring and an additional non-magnetic metal ring that should be used only if the phone is MagSafe compatible (not my case). Additionally, it says: "Note: Before using it, please stick the metal rings for 24 hours on the back of the phone."I've tried both with and without the non-magnetic ring, but the magnetic ring is extremely weak and can't hold no one of my phones. Also, it doesn't stick to the entire back surface of the phone, only to the lower and upper parts, I assume because that's where the microphone and speaker are located.I don’t know if my model is defective or if I’m doing something wrong. I don’t understand why it's necessary to stick the non-magnetic metal ring to the phone for "24 hours" as stated in that page I've linked. Also, in the last product image, this non-magnetic ring is called a "suction ring"; what does suction have to do with it if the mount is magnetic?I’m very confused. Does anyone know how these mounts with magnetic rings work?

author: Ranayna
author_rank: Super Contributor
timestamp: April 17, 2025, 06:10:16 pm
content: Small off topic rant: Since when can you not filter reviews on Amazon without being logged in?They only show a few, in this case all 5-star vine reviews...I can't click on "more", i can't look at that one 2-star review...

author: ThunderZed
author_rank: Regular Contributor
timestamp: April 17, 2025, 06:15:33 pm
content: I'm logged in right now and I can assure you that even if I click on the 2-star reviews, there's nothing thereThere're only 4 and 5 star reviews.

author: Analog Kid
author_rank: Super Contributor
timestamp: April 17, 2025, 07:30:53 pm
content: You mean people would actually trust that thing to hold a phone securelyon a bike?Really?

author: artag
author_rank: Super Contributor
timestamp: April 18, 2025, 03:54:33 am
content: It seems to be designed for Apple with magsafe. They have a ring of magnets already in the phone. This works quite strongly with magnetic holders like this.However, I don't understand the comment about the metal ring. That might be used to convert a non-magsafe phone into one that will work (though not as effectively) but I don't see why you'd put it on a magsafe phone. I think the '24 hour' thing is because it's stuck on with an adhesive pad that gets stronger after a little while. 3M's VFD is like this.No, I wouldn't use it on a bike. But the ad doesn't show that, does it ?

author: Analog Kid
author_rank: Super Contributor
timestamp: April 18, 2025, 04:05:35 am
content: Quote from: artag on April 18, 2025, 03:54:33 amDoesn't show it, but the product heading does say "Bike Tube Bar Clamp Mount".

author: ThunderZed
author_rank: Regular Contributor
timestamp: April 18, 2025, 10:34:45 am
content: Quote from: artag on April 18, 2025, 03:54:33 amYes, this holder works exactly as you said!It’s only for iPhones, but I was misled by the sentence: "It is compatible with most smartphones." I misunderstood it, I mean I didn’t realize that the extra ring had to be glued to the back of the phone in case it wasn’t an iPhone. I also thought that the extra ring somehow converted a non-MagSafe phone into a MagSafe-compatible one… I didn’t expect that the “conversion” was done using adhesive!After this clarification, I tried placing the extra ring inside the rubber thin case of my phone, without actually sticking it on (see attachment), and in this way the holder works, I mean the magnetic ring is able to hold the phone securely.So, does this mean that the only way to use these magnetic holders with non-MagSafe phones, like my Motorola, is to either stick the extra ring directly on the phone/case or place it inside its thin rubber case?I guess there’s no point in looking for a holder with a stronger magnet, since non-MagSafe phones don’t have enough internal “metal” to be held magnetically, right?

author: tom66
author_rank: Super Contributor
timestamp: April 18, 2025, 10:48:36 am
content: Most 'metal' phones are constructed of aluminium because it's easier to machine, can be anodized for corrosion resistance and is light weight for its mechanical strength... Apple do some out of titanium because they're Apple and being extra for no good reason works well for their marketing. Of course, aluminium is not a ferrous metal, so it does not matter how much metal the phone is made of, conventional magnets will not adhere to it.

author: ThunderZed
author_rank: Regular Contributor
timestamp: April 18, 2025, 10:58:28 am
content: Quote from: tom66 on April 18, 2025, 10:48:36 amI meant to say "junk iron" ("ferraglia" in italian), but the automatic translator used the more generic "metal" insteadSo in the end, is this extra adhesive ring a necessity for anyone with a non-MagSafe phone who wants to use a magnetic holder?

author: tom66
author_rank: Super Contributor
timestamp: April 18, 2025, 11:13:03 am
content: Quote from: ThunderZed on April 18, 2025, 10:58:28 amI would imagine so. Unless the manufacturer has put magnets in the phone.

author: SteveThackery
author_rank: Super Contributor
timestamp: April 18, 2025, 06:46:59 pm
content: OK, a question. How does the internal compass chip work in the presence of a really strong magnetic field?

author: Analog Kid
author_rank: Super Contributor
timestamp: April 18, 2025, 07:18:11 pm
content: Quote from: SteveThackery on April 18, 2025, 06:46:59 pmEasy: north always points toward the back of the phone!

author: TimFox
author_rank: Super Contributor
timestamp: April 18, 2025, 09:41:42 pm
content: Quote from: ThunderZed on April 18, 2025, 10:58:28 amIs the idiomatic English translation of “ferraglia” “pot metal”, or is it “scrap iron”?

author: ThunderZed
author_rank: Regular Contributor
timestamp: April 19, 2025, 09:51:33 am
content: Quote from: TimFox on April 18, 2025, 09:41:42 pmI wish my phone had more... ferraglia

author: tom66
author_rank: Super Contributor
timestamp: April 19, 2025, 10:23:33 am
content: Quote from: SteveThackery on April 18, 2025, 06:46:59 pmIf you've actually tried using the compass in a smartphone, you might realise how bad it actually is. Frequently off by 10-20 degrees. They just kind of lie to you. The 'sat nav' car mode uses GPS data to calculate your heading which is far better but only works when your heading and track are identical. You can sometimes do this with pedestrian walking, but you rely on the person always walking in the same direction they're pointing.You can compensate a compass for both hard and soft iron effects. Hard iron would be ferrous magnets typically. Soft iron would be materials that are paramagnetic - they distort the field but don't add to it. They're harder to compensate for because they're often environmental.To get best accuracy from a modern MEMS compass you need to rotate it periodically about all axes so it can see the full field and calculate these distortion factors.