Computer Power supply convertion. - Page 1
Forum section: electronics / beginners

author: AceOfJohn
author_rank: Newbie
timestamp: May 04, 2017, 11:23:35 pm
content: Hi im just starting to kit myself out and im trying to save some money because i dont have much at the moment. I see there are alot of videos about converting computer power supplys to bench power supplys. but...Is this a good idea as a usefull first project. I dont have an osciilloscope yet (well i have a cheep kit) but i have a fewmulti-testers. what family of power supply are computer power supplys? eg switch mode...can i limit current or should there be a current limit already. should i expect the output to change when i apply a load. what are the pros and cons and what should i look out for? i understand that building a bench power supply from a computer psu will be huge learning curve. implementing usefull fetures and improving the supply gradually. but atleast its a project that powers itself from the get go.I know this is anoob question but i dont realy want to end up with a half baked power supply that will give me a poor education when im messing with circuits and testing them.I can get a cheep power supply from ebay but i have no concept of the quality or limitations.If anyone can lead me towards the answers to these sort of questions i would be very greatfull.And thank you Dave for your videos.you aways make me laugh

author: danadak
author_rank: Super Contributor
timestamp: May 05, 2017, 01:27:16 am
content: You can start with a PC sound card based scope for free. Will give you basicallyaudio rang scope, spectrum analyzer, and function generator all using yourPC sound card.https://www.zeitnitz.eu/scope_enhttp://www.zelscope.com/http://www.ledametrix.com/oscope/http://www.virtins.com/downloads.shtmlBut first build a simple circuit to protect sound card inputs so you do notruin from transients, overvoltage. Google "protect sound card input".For examplehttp://makezine.com/projects/sound-card-oscilloscope/Regards, Dana.

author: danadak
author_rank: Super Contributor
timestamp: May 05, 2017, 01:29:42 am
content: Google this "lab power supply from pc power supply", looks likesome folks have done that.Regards, Dana.

author: AceOfJohn
author_rank: Newbie
timestamp: May 05, 2017, 02:11:47 am
content: yes i like that idea. it will suit my needs untill i save up for a scope. Thanks

author: AceOfJohn
author_rank: Newbie
timestamp: May 05, 2017, 02:17:56 am
content: there are plenty of videos and stuff that i have seen, but they dont seem to talk about the problems or the ways you could improve it. ill stick with the little usb 5/3v breadboard power supply for now untill ive learned more. maybe when i get the scope i can save up for a power supply next. Thanks for your reply. any ideas for tempory bench tools are welcomed.

author: rdl
author_rank: Super Contributor
timestamp: May 05, 2017, 02:59:33 am
content: You can't easily make a decent bench power supply from a computer power supply. They can actually supply far too much current if things go wrong. They do have their uses though.If you want to build something to learn from, you could start with basic LM317 circuits and power them from an AC adapter. Since you're just getting started, consider using regulated switch mode "wall warts" and save your money for a real lab supply. Buying one used from ebay is a viable option. There are a number of threads here that discuss this.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: May 05, 2017, 03:19:48 am
content: Computer power supplies are switched mode supplies. They usually regulate the output voltages to preset levels, which is fine because those are useful levels. Some have current limiting, but it is preset and intended for safety. It does not provide a constant current, but shuts down the supply if the current limit is reached.The most confusing thing about using a computer power supply for newbies is the large variety that there are. If you can find the exact model number that the YouTube video your are following you will be fine, but otherwise some fairly confusing problems will show up.Many of them require a load on both primary voltages (5V and 3.3V) to operate. It can be difficult to satisfy all of the conditions, or to modify the circuit to avoid it.You may find it more rewarding to build up a power supply using components salvaged from a computer PSU. This will require more googling and rapid learning, but you will end up with a device you understand very well and that is better suited as a general lab supply.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: May 05, 2017, 06:49:01 am
content: I am using a 350w SMPS that I converted. Thing was simply laying around, so might as well put it to use. I sure wouldn't mind finding an adjustable/variable one later... good enough for now though since I am just messing around. I think these are so popular as a result of having 3.3, 5, 12 and -12v outputs. Has been a tremendous asset while piddling around with electronics. Most likely will have short-circuit protection built-in as well. Very low-cost.For an oscilloscope I bought a DSO138 kit. $16usd shipped if I remember correctly. You get to assemble many of the components. But,....they are limited function and merely a learning tool. Sound card sounds like a fun project too.