Beginner looking at bench power supplies - Page 1
Forum section: electronics / beginners

author: jerrysimon
author_rank: Newbie
timestamp: February 12, 2017, 01:12:01 pm
content: Ok I class myself as a begginner only because I have very little understanding of electronics. All my experience has been self taught from areo modelling and building electric bikes. Here is the background to why I want a power supply and my requirements.Primarily this is in building and using battery packs. I do a lot with building and balancing cells packs and am handy with a soldering iron lolFor my DIY battery work I use a hobby cell balancer (Turnigy) and a converted PC power supply to power it.I then use a mains powered 36v charger block to bulk charge the packs. In practise this provides 42v.So I want a power supply which will give me more control than my DIY PC supply. Because I want the optiom to put my whole battery pack on it I want something with a voltage supply over 42v. This is not essential as my packs do split down into two 21v packs.So these are what I am looking atMy preffered choice (50v 3A) seems reasonable build quality and has a seperate output switch so you can set up V and A before supplying powerhttp://www.ebay.co.uk/itm/222258220290?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AITNext though only 30v but seems popularhttp://www.ebay.co.uk/itm/191766020330?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AITSimular but better build quality, I think, and I saw David's tear down of a simlar unit.http://www.ebay.co.uk/itm/281669947984?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AITOr megga cheap, probably very poor build quality and not keenhttp://www.ebay.co.uk/itm/201748248268?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AITAlthough some of the ones with lower voltage are 5A in practise I dont think I need more than 3A and I like that the first one goes up to 50V. Also saw this 60V one though I think the 50V one is better build quality.http://www.ebay.co.uk/itm/282230926115?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AITWould appreciate your comments/advice.Jerry

author: jerrysimon
author_rank: Newbie
timestamp: February 12, 2017, 01:41:29 pm
content: PS I do see you can buy units that double up. Can these be put in series to give me 60V ?https://www.amazon.co.uk/POWER-SUPPLY-ADJUSTABLE-72-10495-TENMA-x/dp/B01I7R7MGM/ref=sr_1_1?ie=UTF8&qid=1486906775&sr=8-1&keywords=TENMA+power+supplyJerry

author: Brumby
author_rank: Unknown
timestamp: February 12, 2017, 02:28:05 pm
content: The common recommendation often given here for beginners is to go for a dual tracking power supply, similar to the last unit you mentioned. (It is a dual supply, but not sure if it istrackingone.)There are a number of these that can provide two channels of up to 30v each. Some can do 3A and others can do 5A per channel.They can be used:* independently, giving you two separate power supplies* in series to give you a split rail supply of up to 30v (+/-) or a single supply of up to 60v* in parallel allowing you to double the current capacity.This would give you the most flexible supply that can handle not only what you have described - but a lot of future projects.Some also come with a fixed 5v output at a few amps capacity.Others here might have some opinions on makes and models...

author: Kleinstein
author_rank: Super Contributor
timestamp: February 12, 2017, 02:51:51 pm
content: With the dual supplies one can have them in series. Most of them can be used in parallel too, but this is not per Se always the case.With these rather cheap versions, one should take care of the "Chinese" marketing amps. The supplies are often to weak to really stand the full current long time. They may not blow up instantly, but chances are they won't last long. So if they advertise them as 5 A they might be OK up to 3 A or so.Also take a look a the weight - a classical transformer has a certain weight per power and the cheap ones do not use much better transformer quality, but just lower power transformers and don't care much about high temperatures.

author: jerrysimon
author_rank: Newbie
timestamp: February 12, 2017, 03:02:40 pm
content: Quote from: Brumby on February 12, 2017, 02:28:05 pmThanks guys really appreciate the guidance.I have thought about buying a really cheap one and another with higher voltage. I guess buying the dual one would give me the added advantage of having two sources and something a little better built and on the rare occasions I could put them in series. I assume these better quality ones will also display and go down to much lower current settings. The cheaper ones shown on youtube seem to be a bit hit and miss on the accurate display and output at higher settings.What does tracking mean ?RegardsJerry

author: Unknown
author_rank: Unknown
timestamp: February 12, 2017, 06:02:39 pm
content: Quote from: jerrysimon on February 12, 2017, 03:02:40 pmIf a power supply has two tracking outputs, their values follow one another (usually positive and negative) at the tracking ratio. So for example, if you had a 1:1 tracking ratio, V1 may be at 20V and V2 at 20V. If you adjusted V1 to be 10V, V2 would then be 10V. Usually this is set up to give positive and negative voltages (+20V/-20V), e.g. for an op amp.You can adjust the tracking ratio. For example, a 2:1 tracking ratio would give V1 @ 10V and V2 @ 5V.

author: jerrysimon
author_rank: Newbie
timestamp: February 12, 2017, 07:33:37 pm
content: Here is the data sheethttp://www.farnell.com/datasheets/2207185.pdf?_ga=1.59738095.39245907.1484474403Still not sure if it can output at 60V ?Jerry

author: Unknown
author_rank: Unknown
timestamp: February 12, 2017, 08:12:24 pm
content: It would depend whether the outputs are fully isolated from each other. That is to say, that they don't share a common negative rail or something like that.The datasheet is a bit sparse and doesn't mention whether the outputs are isolated, but given the appearance of the supply (where it looks like they've just basically glued two single units into one chassis and they each have a separate ground terminal), I would guess that they are.If you have access to one you could wire it up in series with the current limiters on both (or with a resistor as the bond between the two) and check if it works.

author: jerrysimon
author_rank: Newbie
timestamp: February 12, 2017, 08:12:44 pm
content: Here is another one clearly stating its tracked and can be connected in series.http://www.ebay.co.uk/itm/TENMA-72-8700A-DC-Bench-Power-Supply-Unit-PSU-2CH-32V-5A-adjustable-/112285053237?hash=item1a24b5f135:g:XDcAAOSwA3dYjcU6Jerry

author: Unknown
author_rank: Unknown
timestamp: February 12, 2017, 08:13:48 pm
content: Quote from: jerrysimon on February 12, 2017, 08:12:44 pmSure, there you go.

author: Brumby
author_rank: Unknown
timestamp: February 13, 2017, 02:34:14 am
content: Had a look at the Tenma - and found out a few things....First, there is the range - 3 models:Then there is tracking. Turn tracking on and CH2 follows CH1. Series/parallel connection is OK and appears to be via external connection. The only caution I would make here is - if you want to parallel the outputs, turn tracking on, so that the output voltages stay the same.Then, these are linear supplies - which means a big, fat, heavy transformer and making sure the mains voltage matches your location - but it will mean an electrically less noisy supply.FYI: I do not have any experience on the quality or reliability on these.

author: Housedad
author_rank: Frequent Contributor
timestamp: February 13, 2017, 09:19:31 am
content: I was going to make a suggestion for some used ones, but I then saw you are in England. The shipping would kill the deal.Anyway, A dual tracking is nice. I recently was able to provide +15v and -15v to a circuit with just one dual supply. A very versatile peice of equipment

author: xani
author_rank: Frequent Contributor
timestamp: February 13, 2017, 09:59:44 pm
content: Are those TENMA power supplies rebadges of KORADs ? they look very similiarhttp://koradtechnology.com/en/cp-10.html

author: Brumby
author_rank: Unknown
timestamp: February 14, 2017, 03:00:59 am
content: Or are the KORADs a rebadge of the TENMA?To be honest, I would not like to even venture anywhere near that rabbit hole.For all we know, there is an OEM somewhere that just churns these out by the thousands for anybody who wants to buy a container of them - to re-badge as they like.

author: ProBang2
author_rank: Frequent Contributor
timestamp: February 14, 2017, 06:32:30 am
content: The OEM is KORAD.TENMA rebadges stuff from e.g. UNI-T also.

author: innkeeper
author_rank: Unknown
timestamp: February 17, 2017, 07:28:04 am
content: You may want to consider a dual tracking supply.. as it can be set in series for a higher voltage, in parallel for higher current, and can be used as two supplies independently.