Fake voltage regulator from ali Express - Page 1
Forum section: electronics / general

author: Aurgelme
author_rank: Contributor
timestamp: November 06, 2023, 11:27:26 pm
content: Just for fun I bought a set of voltage regulators cheap from ali express.Some tested fine with 1500mA load, but the 7805 series up to and including 7812 were stable up to only 500mA.Can anyone verify which die this is (78M05 ?)What is the size of the die for an original L7805CV?This was the best picture I managed on my cameraThe lines on the ruler are 1mm, so it seems the silicon chip is around 0.8x 0.6mm

author: wraper
author_rank: Unknown
timestamp: November 06, 2023, 11:46:01 pm
content: 0.5A is what you expect from 78Mxx. Although these are total garbage and who knows what they are supposed to be.

author: magic
author_rank: Super Contributor
timestamp: November 07, 2023, 10:05:34 am
content: I recall LM317 being about 1.5×1.5 millimeter, if not 2×2.Chips with fake markings are normal on AliExpress. They often don't even bother sanding original markings off of chips anymore, the chips are either ordered with false markings straight from the factory or they are ordered blank and marked elsewhere. You can't know it's fake until you test it or look what's inside.Quote from: Aurgelme on November 06, 2023, 11:27:26 pmYou could do better, see below

author: WimWalther
author_rank: Regular Contributor
timestamp: November 09, 2023, 02:36:27 pm
content: Btw.. for the record, it's "die". "Dye" is something used to color fabrics and other items. It's similar to ink.

author: Aurgelme
author_rank: Contributor
timestamp: November 09, 2023, 06:15:25 pm
content: Quote from: WimWalther on November 09, 2023, 02:36:27 pmThanks for the correction! I should have seen the typo myself, since I use quite a bit of 'dye' in aluminum anodizing. Maybe it's the age and the lack of good reading glasses. I have corrected the error in the post above.

author: Aurgelme
author_rank: Contributor
timestamp: November 09, 2023, 06:35:14 pm
content: Along with this set of voltage regulators I also bought some 10 pack bags of L78xxCV and L79xxCV for around 0.1$ each, and they tested correctly according to the data sheet. So shopping on aliexpress is a bit of a lottery.

author: wraper
author_rank: Unknown
timestamp: November 09, 2023, 07:08:05 pm
content: Quote from: Aurgelme on November 09, 2023, 06:35:14 pmThen inspect their logo, which most likely will look more like S7 rather than ST. If you want cheap parts buy Chinese branded stuff from LCSC rather than random fake garbage from Ali, it won't even be more expensive.

author: Kean
author_rank: Unknown
timestamp: November 09, 2023, 07:49:48 pm
content: Some sellers from AliExpress will be better than others, but there is no great way to know. Many small sellers are quite possibly just doing a daily shop at the local markets based on their orders and get whatever part matches the orders that they can make a good profit on. Even the larger sellers that have actual stores in the markets might still run out of the part and will pop to a neighbouring store and pick up some different parts than you bought last time.As @wraper mentioned, buying from LCSC is one of the safer methods of getting cheaper parts. Brand names and part numbers are properly specified. You can choose if you want a known brand or happy to try some clone part, and even review the datasheets on many of those clone parts. Only thing about LCSC is that the total cost is often a little higher once you add shipping.

author: Aurgelme
author_rank: Contributor
timestamp: November 09, 2023, 08:22:14 pm
content: Quote from: wraper on November 09, 2023, 07:08:05 pmNo ST logo on them, but marked with CHN and a Chinese character in the lower left corner

author: Veketti
author_rank: Regular Contributor
timestamp: November 23, 2023, 11:24:27 am
content: I had similar experience with LM2596s step down power converter from Aliexpress. Similar units are sold in many places so the chances are it is quite common with these units. The whole module cost less than euro a piece and one LM2596s IC from Mouser or Digikey cost ~6 euros. Even if there were huuuuge volume, it still doesn’t seem plausible they could sell these modules so cheap. So I did some measurements and indeed it used fake LM2596s ic. Conversion frequency was ~28kHz, when it should have been 150. I measured ripple voltage to be 134mV. For the sake of testing, I ordered some original LM2596s ic’s from Mouser and changed to one of the units and re-measured. Frequency was advertized 150kHz, ripple dropped to 72mV. However the fake ic was better in efficiency. I supplied 24V to the module and had 5V out with 61mA load. With fake chip current draw was 0.0232A and original 0.0262A, so the fake was actually bit better in efficiency. However I was bit surprised by the quite big ripple voltage with the original ic. Maybe it’s due to bad quality output capacitor? Out of curiosity ordered some Panasonic low esr caps to see whether that makes any differences.Makes me wonder why the efficiency was so poor, when these were advertized up to 92% efficiency. Maybe it’s due to so low load?

author: wraper
author_rank: Unknown
timestamp: November 23, 2023, 11:40:31 am
content: Quote from: Veketti on November 23, 2023, 11:24:27 amCould be inadequate diode, inductor or PCB layout for high frequency operation. Also there are cheap real clones of LM2596 on LCSChttps://www.lcsc.com/products/DC-DC-Converters_484.html?keyword=LM2596I personally would not use LM2596, its clones and modules at all when there are cheap modules based on genuine ICs and much cheaper and better ICs available. LM2596 is utterly outdated.

author: Veketti
author_rank: Regular Contributor
timestamp: November 23, 2023, 12:39:51 pm
content: Hopefully it's not too much off topic, but wraper would you mind sharing what better modules you mean? Any adjustable as well?

author: wraper
author_rank: Unknown
timestamp: November 23, 2023, 05:19:55 pm
content: Quote from: Veketti on November 23, 2023, 12:39:51 pmFor example thishttps://www.aliexpress.com/item/1005003696426993.htmland thishttps://www.aliexpress.com/item/32999157554.htmlYou may want to add some more capacitance to the output for lower voltage ripple

author: Whales
author_rank: Super Contributor
timestamp: November 23, 2023, 09:19:32 pm
content: The key thing about LM25x6 is that they look approachable and they look better quality than 34063. For years I thought of them as my easy way into switchmode. Having 2.54mm pins here also helps. "Small must mean hard"I later learned that many buck/boost chips are just as easy to use as the LM25x6 series.I'm very surprised that this chip is still so popular in pre-made modules. Surely it's more expensive to make than its contemporaries, if just in plastic and leadframe costs? Perhaps the market searches by this chip name?