A Small Experiment - Part Two - Page 1
Forum section: electronics / projects

author: German_EE
author_rank: Super Contributor
timestamp: December 07, 2019, 04:10:30 pm
content: Please seehttps://www.eevblog.com/forum/projects/a-small-experiment-part-one/msg2788726/#msg2788726for part one of this story when I order the power supply.Well, it arrived this morning which makes it about two and a half weeks from China to Germany, nice quick service. The power supply was well packed in an unmarked cardboard box and the usual gray China Post plastic bag. The sticker on the base of the supply gives the input voltage (110V-245 V) and the output voltage (5 V 2 A) but nothing else. no safety markings and no CE mark. The power lead is 45 cm long with a 5.5 mm plug on the end.96 V AC was measured between the negative terminal and mains earth. This figure dropped to zero when a 100 k resistor was added between the two points.The results of the output tests are as follows:No LoadOutput 5.345 V DC with 120 mV of 140 KHz noise on top of the DC and it's nasty spiky stuff which will interfere with radio reception.1A Load (50%)Output 5.163 V DC with 300 mV of 158 KHz noise on top of the DC. The power supply ran cool for thirty minutes during this test.2A Load (100%)Output 5.08 V DC with 447 mV of 185 KHz noise on top of the DC. The power supply was slightly warm at the end of the thirty minute test but not hot.SummaryI got what I paid for, a cheap 5 V supply to power a desk light. It needs additional filtering on the output to reduce that noise and I actually get 5 V at 2 A which is a pleasant surprise. This supply will probably be OK for logic work but I wouldn't consider it for test and measurement work or powering an audio amp.

author: Bud
author_rank: Super Contributor
timestamp: December 07, 2019, 04:43:30 pm
content: Could not you use a phone/tablet charger, there are plenty of them in any household laying around.

author: StillTrying
author_rank: Super Contributor
timestamp: December 07, 2019, 05:20:27 pm
content: A Small Question - Part 1Why would you split an already bad thread title into 2 separate bad thread titles.

author: German_EE
author_rank: Super Contributor
timestamp: December 07, 2019, 06:46:38 pm
content: The initial requirement was for a 5V 2A supply as the 1A unit I originally had ran hot and died a fiery death, the average phone charger therefore will not do the job as they are designed for continuous low current float charge.As for splitting the threads, I issued an open invitation to see if anyone could find a 5V 2A supply that was cheaper, the idea being to see what I (we) could get for the lowest sum possible. It looks like I won the race to the bottom but I would have liked to see at least one additional entry.Poor title, maybe. Clickbate was not my intention but I always planned to split this over two posts.

author: madires
author_rank: Super Contributor
timestamp: December 07, 2019, 07:21:19 pm
content: For EUR 2.29 I'd expect a death-dapter.Have you checked the PCB?

author: German_EE
author_rank: Super Contributor
timestamp: December 08, 2019, 09:59:24 am
content: No, because I actually want to use this and the case is sealed. A teardown would be destructive.

author: magic
author_rank: Super Contributor
timestamp: December 08, 2019, 01:56:38 pm
content: QuoteWaiting for part 3I must say that, personally, if I want something ultra cheap I buy brand name and tested PSUs from electronics recyclers.

author: madires
author_rank: Super Contributor
timestamp: December 08, 2019, 03:24:02 pm
content: Quote from: German_EE on December 08, 2019, 09:59:24 amYou might need a good luck charm. Anyhow, in three or four years when the cheap low ESR electrolytic caps break down you have the opportunity to find out if you were lucky or if the SMPSU is built reasonable.

author: austfox
author_rank: Regular Contributor
timestamp: December 08, 2019, 06:48:00 pm
content: I clicked the link to Part 1 expecting page after page of comments (hence the need for Part 2) and came away severely disappointed with only 2 replies!