230v to 5v with no Noise? - Page 1
Forum section: electronics / general

author: Lord of nothing
author_rank: Super Contributor
timestamp: June 18, 2024, 10:59:43 pm
content: Hi everyoneI have some device who power other (aka an USB Hub) who have some sensitive electronic inside where the cheap Chinese Power Supply does send out some noise.So what should I buy for an clean output? Medical Power Supply? Some Voltcraft with multiple Rails one for each Device?Thanks

author: IanB
author_rank: Super Contributor
timestamp: June 18, 2024, 11:25:18 pm
content: If the other things are designed to be powered from a 5 V USB cable, then USB is probably not the issue. Have you tried a higher quality USB supply, like maybe an Apple one, instead of a cheap Chinese one?If you want mains isolation, and lack of mains noise, why not try a USB power bank?

author: Lord of nothing
author_rank: Super Contributor
timestamp: June 19, 2024, 03:30:13 am
content: The USB Fiber extender use an Barell Jack for Power.QuoteIf the are not get powert by Nuclear Energy the will run out of power soon.Everything run 24/7.

author: benyamin.kh200
author_rank: Newbie
timestamp: June 19, 2024, 08:51:08 am
content: you can use this "ADUM3160 USB to USB Isolation "

author: tunk
author_rank: Super Contributor
timestamp: June 19, 2024, 11:05:32 am
content: What's your "cheap Chinese Power Supply"? Maybe post some photos?Ikea has a pretty good reputation when it comes to USB power supplies.I think bigclive@youtube has tested some of them. Ditto for EEVblogmember HKJ:https://lygte-info.dk/info/indexUSB%20UK.html

author: mtwieg
author_rank: Frequent Contributor
timestamp: June 19, 2024, 01:47:31 pm
content: Regadring medical (IEC 60601-1) rated power supplies, the main difference is the stronger protective insulation and reduced leakage current, neither of which are directly related to noise. AFAIK the limits on conducted/radiated emissions for IEC 60601-1 are similar to other common standards.Hard to give more guidance without knowing more about the problem. For example if the problematic "noise" is common mode or differential mode, how the "sensitive electronics" are grounded, etc.

author: IanB
author_rank: Super Contributor
timestamp: June 19, 2024, 02:27:51 pm
content: What I understood is there is a USB hub, which is powered with a mains adapter. In the traditional way of USB hubs, the mains adapter plugs into the hub using a DC barrel plug. The USB hub then provides power to other devices plugged into it. Apparently, the power delivered by the USB hub is not clean enough for some USB device plugged into it.Answers might be to replace the USB hub mains adapter with a higher quality 5 V DC supply, or to replace hub itself with a higher quality hub and power adapter combination.Now 5 V mains adapters/plug packs cannot be hard to buy (Amazon surely has loads of them). So maybe experiment with some other ones and see if they work better?

author: Lord of nothing
author_rank: Super Contributor
timestamp: June 19, 2024, 02:47:17 pm
content: Its a Glasfiber Adapter with an build USB Hub. The reason why I use a bunch of them is simple it allow me to use the Software from the Manufacture of the USB Device on my Server while the Device is somewhere. That could be simple as an Serial Interface (build in the Device a Serial to USB Adapter) or just a USB Dongle like a Temperature Sensor.And why I use Glasfiber? Simple as an 100% Galvanic Isolation. No matter what on the Device side happen have an impact on my Server.QuoteSince the most are look inside quite the same (crappy) it would not make a difference.Here the Power is very noisy so the need good Filter to create an "clean" 5V Output.QuoteThe USB Adapter are just pugged into the USB Hub. How the "big" Device with an Build in Serial (or other USB Host Chip) are I dont know.I just see that the Signal I getting out of them is not useable.Like here with my SDR there are a TON of Noise and the Antenna is Outside.

author: dietert1
author_rank: Super Contributor
timestamp: June 19, 2024, 04:00:28 pm
content: You could try a traditional 5V supply instead, i mean with transformer operating at mains frequency. Even when using a secondary switcher it should be more "quiet". When DIY, you could use a mains transformer with a shield between primary and secondary in order to reduce coupling to mains noise (spikes). Quality bench multimeters have this kind of transformer.Former forum contributor Marco Reps has a youtube video about this: "Low leakage power in precision electronics". He ended up copying from a Datron scheme with isolating secondary switcher.A "better" quality switcher (Meanwell PS-25-5 5V 5A) is € 2,32 at ebay.Regards, Dieter

author: Lord of nothing
author_rank: Super Contributor
timestamp: June 19, 2024, 05:48:56 pm
content: https://www.ebay.at/itm/362728641919That for example?

author: John B
author_rank: Frequent Contributor
timestamp: June 19, 2024, 09:43:29 pm
content: At least from the manufacturers and product series I've looked at, the medical grade devices do also benefit from lower Vpp ripple compared to general purpose adapters.These days I toss away cheap no name AC/DC power supplies just for the safety aspect.

author: dietert1
author_rank: Super Contributor
timestamp: June 19, 2024, 10:04:19 pm
content: The meanwell supplies are better than those plug supplies since there is space for a better mains filter.The problem with all primary switchers is the optocoupler they use for output voltage regulation/feedback. It suffers from capacitive coupling inside the high frequency transformer. So they use capacitors between primary and secondary to absorb those spikes and make the optocoupler work normal. This means a capacitive coupling to a voltage of 115 V AC 50 Hz. Often the capacitance is 2,2 nF or 4,7 nF.The leakage capacitance of the shielded low frequency transformer i mentioned is some pF, so 1000x less.Regards, Dieter

author: mtwieg
author_rank: Frequent Contributor
timestamp: June 19, 2024, 11:28:08 pm
content: Quote from: dietert1 on June 19, 2024, 10:04:19 pmDepending on what specific sort of "noise" is problematic, the mains filter may or may not be relevant.QuoteI'm assuming you mistyped something here... the capacitance across an optocoupler is typically a few pF, which is a negligible fraction of the overall isolation barrier capacitance in an isolated power supply. Interwinding capacitance in the transformer is virtually always the dominant cause of common mode noise.QuoteNothing to do with the optocoupler. The capacitor added across the isolation barrier is there in order to pass EMC tests (particularly common mode conducted EMI), at the cost of increased leakage current.QuoteSome large medical devices do use special 50/60Hz transformers. The capacitance between primary and secondary sides isn't actually any lower than a normal transformer (and is typically far greater than a high frequency ferrite transformer of the same power capacity). But the shielding diverts leakage and conducted emissions to protective earth/chassis GND, making it much easier to pass safety and EMC tests.

author: ejeffrey
author_rank: Super Contributor
timestamp: June 19, 2024, 11:32:33 pm
content: Quote from: mtwieg on June 19, 2024, 01:47:31 pmDepends on what you mean by noise. The reduced leakage capacitance reduces common mode noise especially 50/60 Hz. Differential noise (i.e., ripple) is easily filtered or regulated at the target device so common mode noise is often the problem.

author: dietert1
author_rank: Super Contributor
timestamp: June 20, 2024, 07:54:36 am
content: When you try to make a low noise island, what is needed depends somewhat on your ambient. E.g. unless you have a clean protective earth, don't connect it to shields. And a shield that is connected by a 3 m cable doesn't help above 5 MHz. So the island should be as compact as possible. Shielding high frequency noise may require a ground plane or even a metal cage.Another easy to make mistake is having more than one power line to the island, let's say a mains cable and a USB cable. Or a separate mains cable for the scope. It's a bit of try and error. Once i found that the mains transformer of our old Russian microscope didn't have the spark extinction RC on its mains switch, so it was producing large inductive spikes on turn off. Such spikes are always present on the mains power lines. We also have a soldering iron that regularly emits in standby.Regards, Dieter

author: Nominal Animal
author_rank: Super Contributor
timestamp: June 20, 2024, 09:26:37 am
content: Mean WellGSM18EorNGE18E09P1JorGE18I09P1JorGEM18I09P1Jwith a DIY 9V-to-USB-5V linear regulator?GSM18E05-P1J is class II isolated and 2×MOPP rated, but the 5V 3A output is rated for 60 mVpp ripple.GSM18E07-P1J has 80 mVpp ripple at 7.5V 2A, and GSM18E09-P1J has 80 mVpp ripple at 9V 2A.It's not that much, ±0.060 Vpp and ±0.080 Vpp respectively, so I guess even a low-drop linear regulator (perhaps with an LC filter in front) should quieten that right down. 40dB PSRR would get to 1 mV or less peak-to-peak ripple.I've thought about doing this myself, but I'm only a hobbyist, and I need to learn how to do the USB overcurrent limiting right first... I suppose one could useTPS2561AandTPS2513Afor two USB output ports.

author: Phil1977
author_rank: Frequent Contributor
timestamp: June 20, 2024, 09:29:19 am
content: I just can confirm the necessity of such a low noise island.More technically spoken you want exactly *one* low impedant ground connection for your device. As soon as you connect it do more than one ground connection you create a big loop that´s capturing magnetic emissions.What I usually do if I need maximum cleanliness of any signal:- Get *one* good ground, connect it to your housing or cage- Get *one* connection from the cage to your ground of the most sensitive sensor. That´s also the point to ground your preamplifier- Do as many controls and readouts with differential signalling and use good common mode chokes- Use a staged power supply:- First stage: a Mains-->24V DC SMPS, like these Meanwell modules. Connect the (-)pole of the power suppy to PE-ground to get rid of all 50Hz-common-mode-voltage- Second stage: These isolated DC-DC-converters with metallic housing. Murata / japanese manufacturers are premium, but also the much cheaper chinese "Hi-Link" is doing quite good- Optional third stage: a filter unit of too many decoupling capacitors and common mode chokes where the DC enters the low noise area.But practically the combination of two galvanic isolations is getting rid of quite a lot of annoyances. And the 24V DC from the first stage can also be used as a safe power supply for many devices that else would need an own earth connection.

author: mtwieg
author_rank: Frequent Contributor
timestamp: June 20, 2024, 11:54:06 am
content: Quote from: ejeffrey on June 19, 2024, 11:32:33 pmI agree in principle. I guess I've been in industry so long I've started speaking the language of standards. The stuff injected from the AC line at 50/60Hz is relevant only to leakage tests, while higher frequency signals (starting at 150Khz or maybe 9KHz) is relevant for emissions/immunity tests. Also leakage currents are in fact very deterministic, so just feels weird to refer to them as "noise" IMO.

author: dietert1
author_rank: Super Contributor
timestamp: June 20, 2024, 02:19:21 pm
content: Using a DC intermediate circuit also facilitates battery drive, i mean with a large 24 V battery. Or two of those to keep one charging and the other one discharging, swapping them once a day or so. A 24 V 100 Ah battery sustains a 100 W consumption for 24 hours.Regards, Dieter

author: dietert1
author_rank: Super Contributor
timestamp: June 25, 2024, 10:27:11 am
content: Meanwhile i got a linear 5 V 3 A supply at ebay: "Kniel C5.3". It has a shielded mains transformer and built in mains fuse, with 2N3055 and rectifier bridge mounted on heat sink. Circuit includes a 0.1 Ohm shunt for current measurement.Regards, Dieter