Another Bench Power Supply Question - Page 1
Forum section: electronics / beginners

author: msknight
author_rank: Regular Contributor
timestamp: June 25, 2021, 06:52:57 pm
content: Here we go. At it again. Another beginner asking the same old questionI was looking at the Rigol DP711 - £320 in the UK.Money is an issue so I was looking at switch mode. Surfing the forum posts and asking questions of people, saw the KA3005P pop up, but I'm confronted by this unit at £126https://www.amazon.co.uk/KORAD-KA3005P-Programmable-Precision-Adjustable/dp/B0085QLNFM/ref=sr_1_7?dchild=1&keywords=KA3005P&qid=1624646372&sr=8-7...and then I got confused by this same model at £231...https://www.amazon.co.uk/Programmable-Precision-Adjustable-Regulated-software/dp/B01NAMX0CC/ref=sr_1_5?dchild=1&keywords=KA3005P&qid=1624646372&sr=8-5...and then I got kerfuzzled.Likewise I've gone a bit nuts around the switch mode units, thinking that this was a version of the Dr Meter that people talk about in the US...https://www.amazon.co.uk/ReaseJoy-Laboratory-Regulated-Adjustable-Precision/dp/B06X9DD4HJ/ref=sr_1_8?dchild=1&keywords=Dr.meter+30V+5A&qid=1624644601&s=diy&sr=1-8...but I'm told that the noise is unacceptable even for a switch mode unit.I know that my first bench power supply won't be my last, but I don't yet have the confidence to build one. 30V at 5A will be plenty and should last me a while... I've just got to make sure that my money counts and that I don't make a stupid mistake.Hence I'm asking here for any suggestions to widen the scope of units that people know are worthwhile, either in the lower cost transformer, or the switch mode with little noise... because my poor brain is starting to melt with the choice.

author: ledtester
author_rank: Super Contributor
timestamp: June 25, 2021, 07:51:06 pm
content: Some things to keep in mind...- control circuits do not require a lot of power- it's often helpful to have two independent power supplies... for instance when working with op-amps or to simulate two different voltage levels in your application- low-voltage, low power electronics really benefit from a clean power rail such as you get from a linear power supplyFor example, let's suppose you're developing a 3D printer. The electronics controlling the motors is all low-voltage and low power. The motors themselves might need a higher voltage and a lot of current, but you don't need to use an expensive bench supply for them -- you can use a much less expensive fixed output supply. In any case you don't need a lot of current to exercise the control circuitry.My most used power supply is linear and has two 1A/24V variable outputs and a fixed 5V output. One ancillary benefit of using a low-power supply is that it is fanless and therefore very quiet.

author: ledtester
author_rank: Super Contributor
timestamp: June 25, 2021, 08:37:56 pm
content: Some linear possibilities from ebay.co.uk:-Weir Marconi 30V 6A DC Power Supply 413D Linear- £48.00 + P&P-Farnell 30V 5A Linear Power SupplyCurrently £15 (collect in person only)-Lavolta BPS305 Variable Linear Adjustable Lab DC Bench Power Supply 0-30V 0-5A- £55For the Lavolta supply, check out this video:Very Cheap and Easy Mod to Fix the Horrible Ripple, Below 1mV RMS ! - Lavolta BPS305 MKIIhttps://youtu.be/MAZooNXW1lw

author: msknight
author_rank: Regular Contributor
timestamp: June 25, 2021, 09:37:49 pm
content: Interestingly, the LaVolta picture through the side shows a circuit board, while in K-Tech's video there was a transformer visible. A comment only 4 months old stated that they bought one only to find the transformer had been swapped to switch mode. Feels like getting one of these, no matter what the brand, is going to be a bit of a crap shoot.Cheltenham's a bit too far away from me, and the M4 is probably back to being murder, but a good shout nonetheless.The Weir Marconi... down to 1A at 30V... but for that price, I'll have a think on that.I have to admit that I'm starting to conclude that I'm better off saving for a few months and waiting for the Rigol. I think I can survive using the 5v 3A USB transformer for a while longer.

author: rdl
author_rank: Super Contributor
timestamp: June 26, 2021, 12:55:15 am
content: I survived my first few years in the hobby with a power supply I built from a circuit in a Forrest Mims book. It probably cost less than $25 using mostly Radio Shack parts.

author: MarkF
author_rank: Super Contributor
timestamp: June 26, 2021, 02:15:52 am
content: I just posted about the Siglent a few days ago.TheSiglent SPD1305X 30 V/5 A Linear Power Supplyis a little less current than the Rigol buthas a USB interface and remote sense lines for $280 at Saelig minus their EEVBlog discount.There is also their16 V/8 A SPD1168Xmodel.And a review by Defpom:(Defpom also reviewed the SPD1168X model.)There is also theKORAD KA3005D 30V, 5A DC Linear Power Supply. Which Dave did a teardown and review on.And check out his follow-up on design fix by Korad.

author: MarkF
author_rank: Super Contributor
timestamp: June 26, 2021, 02:40:47 am
content: If you want a few projects:In the meantime, you might want to build a basic dual power supply with basic three terminal regulators.A +/- 12v, 1A power supply is nice to have around for those op-amp circuits.Also, at 12v you can use the positive half for projects with battery needs.There is also the LM317 variable power supply:

author: msknight
author_rank: Regular Contributor
timestamp: June 26, 2021, 07:09:21 am
content: Many thanks for the suggestions.One of the reasons behind buying a bench power supply is because I'm a beginner and I'm not confident about handling AC. I dare say that as I progress, I'll tackle those rite of passage power circuits. Also, being in the UK, the demise of Maplin(indeed, its slow morphing into a general low-cost chinese electronics toy shop before it died)does leave the UK hobbyist with reduced choices for parts.After watching some videos, I've decided to go with the KA3005D as a starting unit.I don't know the difference between the D and the P that Dave reviewed. He was complimentary about the construction of the thing including the power supply and some of the important AC stuff. A few times in the video he says,"They've gone to a bit of trouble here..."and,"They've done this properly. I like it."There were a few things about the USB board that he wasn't too happy about, but I won't be using that because it probably doesn't come with Linux software anyway. He was also fairly hacked off about the processor chips..."Ah, they've scratched the bloody numbers off again. Dickheads." ... "The first thing you notice is that the bastards have scratched the number off the chip. Gimme a break. Idiots. Why bother. It's just ridiculous."His testing did throw up a fail but looking at the circuit board in the sales pictures against the board as Dave looked at it 9 years ago, there do seem to be differences, so I'm going to take a chance with the D. They'd have to be insane to carry on with that fault present after he flagged it.Many thanks for all the suggestions and help.

author: radiolistener
author_rank: Super Contributor
timestamp: June 26, 2021, 07:20:48 am
content: Quote from: msknight on June 26, 2021, 07:09:21 amThe difference is USB-serial interface to control unit from PC software.D doesn't have USB moduleP has USB module

author: krzysssztof
author_rank: Contributor
timestamp: June 26, 2021, 06:49:43 pm
content: I'm also using KA3005D and I can recommend it for the begineers.My unit had an issue with noisy fan (not sure if Korad resolved it later), so I've added 40C degrees thermostat in series, and glued it to the heatsink.Now it is completely silent at low current.

author: msknight
author_rank: Regular Contributor
timestamp: July 05, 2021, 11:05:03 am
content: Quote from: krzysssztof on June 26, 2021, 06:49:43 pmI'd be grateful if you could point me at the part, if possible on Farnellhttps://uk.farnell.com/as I'm going to place an order with them shortly... to quiet down this fan. It sounds like it's a new unit because it's got a baby rattle in it. If there's a picture of how you did it, that would be a serious bonus for me, to make sure I don't muck something up. I'd also like to know which glue you used to attach to the heatsink, as the only thing I've got here is superglue.The side was mildly caved in on delivery... no clue as to how they managed that.The supplied probes are a complete mystery. What am I supposed to do... put one set of crocks on the banana plugs and then use the other set of crocs to stretch the lead to where I actually need it? Er... fortunately I did anticipate something like this and I have another set of leads on order.Unexpected was the bank of different sized jack plugs. A small bonus.So... bend the casing out again and deal with the fan, and I should be good to go. From what I believe, it would not be a simple job to replace the fan itself. Am I right?

author: ledtester
author_rank: Super Contributor
timestamp: July 08, 2021, 04:33:33 am
content: QuoteThe bare banana and alligator clips are provided so you can make your own cables.As for the supplied alligator cables -- you might be able use them as-is by inserting one of the jaws of the alligator clip into the banana socket with the other jaw biting down on the insulated part of the binding post.The binding posts should support the use of bare wires as demonstrated in the first part of this video:https://blog.kantoaudio.com/tech-tuesday-how-to-connect-speaker-wire-to-a-binding-post/QuoteFan replacement should be easy... but a quieter fan might not be the complete solution... have a look at this guy's experience:https://youtu.be/Hmc-2NBIztsalthough this guy seems to be pleased with the mod:https://youtu.be/fgdS_3ZApIQ

author: msknight
author_rank: Regular Contributor
timestamp: July 09, 2021, 06:18:10 pm
content: Quote from: ledtester on July 08, 2021, 04:33:33 amI figured that out after posting... like many things I do on the internet... I really should slow down and think on things before posting stuff and making myself look like an idiot.I had ordered a set of 1M cables which arrived a few days later, and they're nice quality, so I'm happy.Thanks very much for the links to the videos. I'll give them a look when I've unwound from another crazy week!

author: msknight
author_rank: Regular Contributor
timestamp: July 09, 2021, 08:05:48 pm
content: For what it's worth, after watching the videos I decided to open mine again to check the positioning of the wires against the air flow plate to make sure they wouldn't get cut... to find out that there wasn't any plate. It also looks like they're back to a large capacitor and there's a gap between the fan and the circuit board at the top. Interesting.Of course, one of the problems is that there aren't any noise readings so I've got no way of telling how noisy mine is against any of the earlier models. No clue as to the make of the fan as I didn't remove it and there was no label on the inside of the fan spindle (which I could see through the gap) - So I used a copy of Spectroid on my mobile phone and put it at the back of the fan, maybe 2 or 3 cm away from the metal. It doesn't sound too bad.

author: MarkF
author_rank: Super Contributor
timestamp: July 10, 2021, 04:16:55 am
content: Quote from: msknight on July 09, 2021, 08:05:48 pmNot sure what you're getting at here.However, here is a video Dave did on the redesigned power board (side-by-side @ time 2:30).

author: ledtester
author_rank: Super Contributor
timestamp: July 10, 2021, 05:49:08 am
content: Re: air-flow plate...Are you referring to the plate that you can see positioned in the middle of the case in this video?https://youtu.be/8PJdvY715w4

author: msknight
author_rank: Regular Contributor
timestamp: July 10, 2021, 05:50:34 am
content: Quote from: ledtester on July 10, 2021, 05:49:08 amYes

author: msknight
author_rank: Regular Contributor
timestamp: July 10, 2021, 05:57:22 am
content: Quote from: MarkF on July 10, 2021, 04:16:55 amI may have mis-understood one of the earlier videos, but I believed they'd changed the one big cap for three smaller caps for a short period... and that sort of made sense to me given the other positions on the board which are empty.Edit - That's what they did. It's in Peter Brockie's video