Cheap, accurate, low noise PSUs/regulators for DIY sensor projects? - Page 1
Forum section: electronics / projects

author: evb149
author_rank: Regular Contributor
timestamp: December 17, 2016, 05:53:26 pm
content: Sometimes I look for something like a +5.0VDC PSU for DIY projects or sometimes +/- 5V or +/- 12..15V for op-amps and communication transceivers.The other day, for instance, I wanted a low noise 5.0VDC +/- 2% (+/-0.1V) PSU that could supply 250mA or so with relatively low noise.I thought of USB power but that doesn't usually meet the accuracy or the noise requirements though maybe some USB "charger" AC-to-DC wall wart PSUs would, it's not so easy to find ones with specifications that indicate what the noise and accuracy will actually be to such levels in commodity marketplaces like Amazon.I thought of the Chinese made "DC-DC" modules that I sometimes hear about that are popular for projects but the ones I stumbled across seemed to not have good noise / accuracy specifications and also were only buck or only boost mode and not buck-boost / SEPIC or similar and so could not take in a voltage like from USB or a generic 5V ACDC PSU that may be a bit less or a bit more than the target voltage and put out a clean well regulated accurate 5.0V output.So in this age of "just buy it from Amazon" or "just buy it from ebay" what are good, inexpensive, and available options for AC-DC wall warts or DC-DC modules that are good off the shelf solutions for somewhat precision somewhat analog / sensor types of circuits that you don't want 300mV or switcher noise or +/- 5% or worse tolerances on the outputs if they are to be used fairly directly to supply mixed signal circuits and sensors?Obviously a "good choice" is to use a local filter and linear regulator running from a higher voltage like 7V or 9V or 12V to get a clean 5V but then that ends up being worthy of a small PCB by the time the decoupling and connectors and the regulator and so on are installed. The point of "off the shelf" modules is to avoid the need for building every little thing like a linear PSU yourself at least for a decent prototype / experiment. So what's out there that is good for grab & go prototyping with good accuracy and noise and also inexpensively using off the shelf modules / AC-DC adapters?A couple old phone charger 5VDC PSUs I found were even putting out 7V+ for a "5VDC" PSU unloaded though it appeared from size, shape, mass to be a switcher and therefore presumably actively regulated I couldn't understand why it'd be SO out of spec for regulation almost like an old transformer / rectifer / capacitor unregulated supply. So I'm skeptical about cheap "5V" ACDC units unless some are known to be good in noise and accuracy / regulation.Seems like a nice little buck-boost / SEPIC module that puts out clean +5.0 from USB or +3.3V or +12V or such would be nice. And a similar case for putting out a clean precise +/-5 to +/-12 adjustable by resistor choice or such.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 17, 2016, 06:18:52 pm
content: 5 V from USB is about the worst you can get: lots of noise / RF background and usually less than 5 V, sometimes quite a lot.You don't really need a board for regulation. Just a 7805 or similar regulator and to caps can work without (e.g. 0805 MLCC directly at the pins of TO220 case). Make sure the wall-wart is one of the old heavy ones. There are lower noise regulators then the old 7805, but many of the newer ones are low drop and are more picky with the caps.