cheap DC power supply that an do +/-5v - Page 1
Forum section: electronics / testgear

author: prune
author_rank: Newbie
timestamp: January 23, 2025, 03:23:36 pm
content: Hi there,I searched (probably badly) but can't find the info i'm looking for...I'm looking for a cheap DC power supply that can do +/- 5v (or other voltages) for playing with op-amps and other stuffs like that.Back in school (in the 80s), we used to have dual output DC power supply that we were bridging and using the middle connector as our "gnd" (0v).What about now ?I'm seeing a lot of Chinese made DC power supply like 30v 10A, for 75$ (in Canada)https://www.amazon.ca/gp/product/B07GCKHKC6/ref=ox_sc_act_title_3or dual output for 300$https://www.amazon.ca/gp/product/B09YS47GYF/ref=ox_sc_act_title_4... but can I bridge 2 small or the 2 outputs from the bigger one to get symetric voltage ?Any other recommendation if not ?I'm a hobbyist so I don't want to break the bank for it... and I think it does not have to be super quality/low noise either for what I want to "play with".Thanks !

author: myf
author_rank: Regular Contributor
timestamp: January 23, 2025, 05:58:35 pm
content: Hello,Maybe you can use two ruideng dps-3005 with TWO laptop power supply unit. Series connection of these power supplies is possible, but they must not be connected in parallel.Diodes in series on both outputs prevent current from flowing “the wrong way” through the DC/DC converter.The circuit can also be protected by an inverting diode on both power supply poles. The aim is to prevent the generator receiving current in the wrong direction, as this destroys these poorly protected power supplies.A dual power supply is not necessary with all op-amps. Some circuits and assemblies don't need a midpoint, or the midpoint can be obtained as the midpoint between two resistors in series (connected to (+) and (-)).F. with the DeepL.com free version help !

author: prune
author_rank: Newbie
timestamp: January 23, 2025, 06:18:44 pm
content: thanks for the reply !I just saw a video on youtube, using a siglent dual power supply, and having the middle point set on the ground... so:channel 1: + will be your main positivechannel 1: - linked to groundchannel 2: + plugged to the groundchannel 2: - is the main negativeground: middle pointI really doubt that is possible, right ?

author: bdunham7
author_rank: Super Contributor
timestamp: January 23, 2025, 06:34:32 pm
content: Quote from: prune on January 23, 2025, 06:18:44 pmIn fact that is exactly how it is done. The only requirement is that the two channels have to be isolated and that is the usual case. However, there are exceptions to watch for.

author: prune
author_rank: Newbie
timestamp: January 23, 2025, 06:41:00 pm
content: OK many thanks !

author: adam4521
author_rank: Regular Contributor
timestamp: January 23, 2025, 06:54:17 pm
content: Allow for leads, clips, adaptors to connect to your projects. If you’re thinking about ‘opamps’, audio or other analogue/measurement type projects you might want to see if you can get a linear one with old-school transformer inside rather than a ‘switching’ PSU.For breadboarding also consider getting a USB powered module for convenience although take care —the ‘dual rail’ ones are not typically independent supplies. AA battery holders can be quite convenient too.

author: themadhippy
author_rank: Super Contributor
timestamp: January 23, 2025, 07:16:18 pm
content: why not knock something up yerself?

author: prune
author_rank: Newbie
timestamp: January 23, 2025, 07:52:43 pm
content: lazinessI'm just starting to look into this and trying to make my head around... but it will probably be the next option if I want to keep costs to the minimum

author: Hr_Satch
author_rank: Contributor
timestamp: January 23, 2025, 08:12:45 pm
content: Hello, yeah, if it doesn't may take a huge bite in your budget,assemble a dual PSU yourselves.BUT, OpAmps, often do need more than +&- 5Volts.AND, it needs to be symmetrical, and at best somehow tracking under Load !my simplest, best , and ideal limited costs would be two 15V regs. LM7815and a uA7915 for the negative side. But this isn't Tracking, . . .And often tracking designs in ANs, are just tracking one rail to the other.Moreover, they are too often Tracking the Least loaded rail, the Negative oneIdeally should track both. Otherwise stick to assymmetrical supplied OpAmp applications, LoLThere used to be a rather simple solution to Tracking both rails: an SG-3501 see pict.But with ALL good things, somehow they come to an end, and get replaces by rubbish SMPS, . . .Once again: my simplest, and best for the wallet: two complemantary 'fixed' regs in To-220dual bridge rectifier, some CAPS,and a convenient dual centertapped secondary transformer with it:pritty much less noise and distortion.