Cheap Usb Charger/Psu - Page 1
Forum section: electronics / general

author: dragon2611
author_rank: Newbie
timestamp: December 15, 2013, 05:52:19 pm
content: http://cpc.farnell.com/raspberry-pi-psu/rpi-psu-uk-mk1/raspberry-pi-power-supply-5v-1a/dp/PW03060These likely to be ok for charging phones or for powering stuff that takes a micro usb input (e.g a "3G" usb router)?Not as compact as some of the "chargers" on the market but I'd hope if someone like farnel are selling them they'd have passed all the relevant safety testsIf not if someone can provide a recommendation for an alternative that would be great.

author: SeanB
author_rank: Super Contributor
timestamp: December 15, 2013, 06:00:58 pm
content: More likely to be a genuine item and not terribly bad, but you still cannot put a decent unit into such a small case.Look at the PW03335 or PW0339 for something a little bigger current wise but you will need to add a USB socket to it to plug in a phone or tablet.

author: dragon2611
author_rank: Newbie
timestamp: December 15, 2013, 06:09:08 pm
content: http://cpc.farnell.com/pro-power/mwusb3uk-black/usb-power-supply-5v-2-1a-black/dp/PW03051- Another oneI had a few phone chargers from buying various phones but I seem have an awful habit of leaving them places so might pickup a couple of spares.Also I have a small router thing coming that will probably be cheap chinese tat, it's usb powered but if it comes with a PSU I think i'll replace that with something that's more likely to at least been properly safety tested.

author: minime72706
author_rank: Frequent Contributor
timestamp: December 18, 2013, 07:16:00 pm
content: I don't tend to trust switch-mode USB chargers at this price range. I tear open USB chargers and other SMPS as a little hobby and I've seen some shitty shit. This is just my opinion, however. It might be just fine.The standard Apple iPad and/or iPhone charger is legitimately a very well designed power supply and any knock-offs are going to be terrible, especially <$10 ones.

author: AndersAnd
author_rank: Frequent Contributor
timestamp: December 19, 2013, 02:55:50 pm
content: HKJ who's also a member here has made a great "USB Power Supply/Charger Test":https://www.eevblog.com/forum/blog/eevblog-388-fake-apple-usb-charger-teardown/msg207735/#msg207735If you want one or more additional models tested, I think he would be interested to put a test on his website, if you either order it directly to his address in Denmark, ship it yourself or pay him to order one. You could try to ask if he's interested via PM or info@lygte-info.dkUSB Power Supply/Charger TestIncluding measurements and tear-down pictureshttp://www.lygte-info.dk/info/usbPowerSupplyTest%20UK.htmlQuoteHKJ has a lot of other very good flash-light, battery and charger tests too. Frontpage:http://www.lygte-info.dk

author: dragon2611
author_rank: Newbie
timestamp: December 21, 2013, 12:25:09 pm
content: Out of interest what casues some of them to emit a high pitched whistling noise under light to no load.The one that came with my Tesco Hudl and also the offical charger that was supplied with the LG Nexus 4 (Bought direct from google play) do it and it drives me nuts as I can hear it.In both cases it happens when I either disconnect the device, (No load) or when the device is fully charged therefore presumably not drawing much current.

author: amyk
author_rank: Super Contributor
timestamp: December 21, 2013, 12:44:52 pm
content: The SMPS in them is variable frequency - with a regular load the switching frequency is too high to hear, but when it's unloaded the frequency goes down; the oscillator is stopped most of the time and cycles only enough to top up the output capacitor as the voltage will be declining very slowly.And regarding that test: keep in mind that 250mV of pk-pk ripple on 5V is still only 5% out, no issue at all for a battery charger as 4.75V will charge the battery perfectly fine and power the device that DC-DC's that down to 3.3 or lower for the power rails. It's also within the USB spec.

author: minime72706
author_rank: Frequent Contributor
timestamp: December 21, 2013, 04:41:38 pm
content: I've been told that most designs do attempt to keep out of the audio range, but the feedback loop itself is what you hear whining. (through the switching transformer)

author: TheBay
author_rank: Unknown
timestamp: December 21, 2013, 09:41:21 pm
content: I like the HTC and Samsung Note 2/Galaxy S4 chargers.

author: VK5RC
author_rank: Unknown
timestamp: December 22, 2013, 04:52:42 am
content: As a RF enthusiast, please keep in mind that the 'ripple' is often conducted back up the mains wiring in the 'crappier' of these units, radiates around the district and drives us nuts, you get spikes that wander up and down the RF bands (sometimes you can hear the harmonics up to 20MHz if a really bad SMPS)Often the units are worse if unloaded; unplugging them if not in use helps.Rob Culver

author: TheBay
author_rank: Unknown
timestamp: December 26, 2013, 01:09:22 am
content: I bet you just love home plugsQuote from: VK5RC on December 22, 2013, 04:52:42 am

author: VK5RC
author_rank: Unknown
timestamp: December 26, 2013, 09:43:49 am
content: It does stretch the imagination that they were ever allowed anywhere! I suspect with more use of the RF spectrum (and the government getting its share of the profits)I hopethe RF regulator may start to pay more attention to 'polluters'.

author: TheBay
author_rank: Unknown
timestamp: December 27, 2013, 12:48:15 am
content: I do hope so!But in addition to that, all this rubbish coming over from the far east seems unstoppable, with their so called fake approval types etc.I recall a time when I was visiting my uncle in the Alps, their TV network and internet run via their mains power lines, during my stay their TV and internet was intermittent, we soon discovered the TV/Internet would return when I unplugged my netbook. It was a cheap far east SMPS causing so much noise it knocked the lot out.Quote from: VK5RC on December 26, 2013, 09:43:49 am

author: urbis
author_rank: Unknown
timestamp: December 28, 2013, 12:55:07 am
content: Although homeplugs can be a nuisance, they are fantastic in terms of what they offer.I wouldn't be surprised if the frequency used does change at some point but I'm pretty sure they're here to stay.