Power Supply Opinions - Page 1
Forum section: electronics / beginners

author: Chet T16
author_rank: Frequent Contributor
timestamp: April 27, 2011, 02:48:26 pm
content: Hi all,First postI'm putting together a bench power supply using twotuxgraphicskits for dual outputs.I know people on here aren't overly impressed with these kits but its going to be a bit better than my chopped up wall adapter i use now!I bought a laptop power supply to run both of them off and i want to get some opinions on it before i go ahead with putting everything together.With the kits i'm looking at 22V/2.5A each and this power supply gives a claimed 5A @ 24VDoes it look like it might work? (i.e. does it look like disasterous crap that will kill everyone) Any problems just splitting the output between the two bench supplies?Pics turned out a bit dark, sorry.Thanks

author: firewalker
author_rank: Super Contributor
timestamp: April 27, 2011, 03:59:31 pm
content: I am using a modified (4x16 display with power consumption, removed the i2c protocol among other things I can't recall now) version of the old tuxgraphics psu for several years.I think that this laptop psu is ok. I am using a 3 amp 24 v laptop psu my self.

author: firewalker
author_rank: Super Contributor
timestamp: April 27, 2011, 04:04:53 pm
content: Ah...I would also suggest using a neon lamp to the output of the laptop psu.

author: Chet T16
author_rank: Frequent Contributor
timestamp: April 27, 2011, 05:14:24 pm
content: Forgive my ignorance, neon lamp?

author: firewalker
author_rank: Super Contributor
timestamp: April 27, 2011, 05:31:48 pm
content: Quote from: Chet T16 on April 27, 2011, 05:14:24 pmIn some switch mode psus there is a "high voltage" component that could potentially cause problems with some devices. I managed to eliminate mine with aconnected to the laptop psu output (A neon lamp was sitting to my bench at the time. I tried some caps too with no effect).Test with a testing screwdriver your laptop psu output.

author: Chet T16
author_rank: Frequent Contributor
timestamp: April 29, 2011, 08:28:46 am
content: Ok, i've been googling and still don't understandWhat should i be looking for with the psu? (i have my oscilloscope now \o/)What does the neon lamp do? Is it something specific to being a neon lamp??Thanks!

author: firewalker
author_rank: Super Contributor
timestamp: April 29, 2011, 12:25:39 pm
content: See the following video. Notice how the output (19 volts) of my laptops psu lights the testing screwdriver. Also notice that the "high voltage" disappears when touching the output with my finger.SaAW4-9bhcwThe only problem that caused (for me) was some "garbage" on an LCD of a circuit I had designed and was testing it with such an smps (usually the ones with CEE 7/16, CEE 7/17 ac plugs with lack of the ground).Putting an neon lamp (I also removed the resistor it goes with it) to the output somehow "sort circuit" this residual/component voltage and "eliminates" it.** I can;t recall why this voltage is there. It could be the filter caps on the 220 a.c. input or the caps after the rectifier (in some cases). If someone knows/remember will tell us.

author: hitachi8
author_rank: Contributor
timestamp: April 29, 2011, 09:18:25 pm
content: Quote from: firewalker on April 27, 2011, 05:31:48 pmBrilliant!, thank you for the information.(i had some problem in the past but i never knew why...)

author: Chet T16
author_rank: Frequent Contributor
timestamp: April 30, 2011, 11:41:54 am
content: I'll have to check out the psu for that!Thanks a million

author: firewalker
author_rank: Super Contributor
timestamp: April 30, 2011, 05:41:26 pm
content: Quote from: Chet T16 on April 30, 2011, 11:41:54 amAny time m8!** When you complete the power supply fell free to make and post a mini review. Basically if it over/under shoot, ripple etc. Use your fresh oscilloscope!

author: Chet T16
author_rank: Frequent Contributor
timestamp: April 30, 2011, 05:46:46 pm
content: I definately will! I just need to get these exams out of the way and i'll get stuck in

author: Chet T16
author_rank: Frequent Contributor
timestamp: August 21, 2011, 10:54:10 pm
content: I finished making the power supply and noticed the output wasn't very stable. I hooked the oscilloscope up to the input and outputs of the supply and i see the input isn't very stable and this is mirrored on the output. I this typical of a SMPS?? On screen you can see the peak to peak voltages of both, the input is 24v the output set to 4.5v

author: Kozmyk
author_rank: Regular Contributor
timestamp: August 21, 2011, 11:23:02 pm
content: I thought you might show us a trace with a neon in place. 8^)

author: firewalker
author_rank: Super Contributor
timestamp: August 23, 2011, 08:20:14 pm
content: Also give it a try with a normal transformer and a rectifier bridge.