Power adopter from china-under rated! - Page 1
Forum section: electronics / beginners

author: Greate
author_rank: Contributor
timestamp: June 01, 2012, 11:26:06 pm
content: We bough 4 power adopter that are made in china, it is rated 9 v 500mA. Just out of curiosity I measured the output and was supriesed to see 14.5v output because I think that's too much for a power adoter with 9v rating. I tried to measure the other power adopter I have that we bougth from radio shack it is rated 9v 300mA and I just got 10.4v wich is I think is just in rangebfornits rating.I thingk the 4 power adopter with 9v rating are under rated. It should be rated as 12v.Sent from my A100 using Tapatalk-

author: Bored@Work
author_rank: Super Contributor
timestamp: June 01, 2012, 11:59:47 pm
content: Quote from: Greate on June 01, 2012, 11:26:06 pmMight change under load.QuoteI don't care.

author: mariush
author_rank: Super Contributor
timestamp: June 02, 2012, 12:25:16 am
content: The power adapters are unregulated, the voltage will definitely go down as you put some load on them.For a simple demonstration, take a computer fan (most are 12v ~150-250mA) and measure the voltage once the fan spins and you'll see the voltage probably even under 9vIf you need them to always give you something close to 9v, you might try to "mod" them by adding a few leds (with the appropriate resistor) - each led being 10-20mA, with about 3 leds you would have about 50mA of constant load on the adapter which may be enough to pull the voltage down to something like about 10v

author: T4P
author_rank: Super Contributor
timestamp: June 02, 2012, 03:31:31 am
content: Quote from: Greate on June 01, 2012, 11:26:06 pmUnregulated, poor transformer regulation.Sent from my Windows using Rockmelt

author: DavidDLC
author_rank: Frequent Contributor
timestamp: June 02, 2012, 03:38:36 am
content: QuoteYou are right !Sent from my crappy computer using whatever I can use.

author: ftransform
author_rank: Frequent Contributor
timestamp: June 02, 2012, 08:30:57 am
content: If you are really curious about this phenomenon you could build yourself a constant current sink, as shown in daves video,http://www.eevblog.com/2010/08/01/eevblog-102-diy-constant-current-dummy-load-for-power-supply-and-battery-testing/This way you could get a graph of the voltage/load relationship of your particular power supply. If you are not familiar with the concept it allows you to regulate the amount of current you draw by way of a knob.sent by trained lyre bird chorus imitating a modem by way of payphone

author: metalphreak
author_rank: Frequent Contributor
timestamp: June 02, 2012, 08:36:45 am
content: Tapatalk is an app for smartphones that makes forums easier to read and post to on small screen devices. It automatically adds that crap on the bottom of your posts by default. Just like the iphone adds "Sent from my iPhone" to all your emails...On-Topic: as posted by others, its simply an unregulated supply. They're usually designed for a specific load range to get the advertised voltage. If you underload them (or put no load at all) they'll give you a higher voltage.

author: Zero999
author_rank: Super Contributor
timestamp: June 02, 2012, 09:15:07 am
content: I've never heard of a power adopter, you must mean a poweradaptor.

author: ejeffrey
author_rank: Super Contributor
timestamp: June 02, 2012, 09:30:20 am
content: It is not necessarily unregulated. Most regulators have a minimum load current below which they don't regulate. For a lot of cheap isolated converters the minimum is often quite high. Put 20-50% the rated load and it will likely drop down to 9v.

author: Monkeh
author_rank: Super Contributor
timestamp: June 02, 2012, 12:46:22 pm
content: Quote from: metalphreak on June 02, 2012, 08:36:45 amEven though you have to pay for the app, and for the phone, they still use you as free advertising. It's disgraceful.