I have a couple of linear PSU's (Weir, both 30V-2A, 15V-4A) but they are both old and are now non-functional / iffy and I was considering something newer, lighter, smaller and with twin digital displays (on the Weir's you have to switch between displaying V and A).
There are loads over the normal suppliers but I wondered if anyone here had got something reasonably recently that they could recommend?
It's for general use, (temporarily) powering 5/12V things, charging the odd battery and the like.
A 10A capacity might mean it can batter handle a 5A output, quieter the better (some use small heatsinks and small fans) and ideally under say £100?
I did look at kits (good to know you have the cct diagram) but that's probably not best done with a SMPSU and linear stuff also seems to require large heatsinks and heavy switching devices, all taking extra time to source/ build (unless a complete kit with case / hardware etc).
In message snipped-for-privacy@4ax.com, T i m snipped-for-privacy@spaced.me.uk> writes
I, and quite a few people I know, regularly use units from Maplins and Circuit Specialists (Europe) with excellent results, although our use is operating ancient (open frame) and modern (can) electric motors (toy trains), where voltage requirements can be anywhere from 4 to 30, and amps less than an amp to 5 amps.
I don't think the Maplin units are available unused now, but CSE units are :
Yes, something I discovered when automating a section of BIL's model railway layout with an Arduino and using PWM. On the same settings, one loco would hardly move and another would fly off the track!
That's spooky Graeme, that looks *exactly* the same as the one my mate had in his PC shop and *we* used many times, till he sold up (and took it with him). ;-(
My only criticism of it (and we shared it actually) is that it was easy to grab the 'Coarse' rather than 'Fine' knob if you were doing something on the fly. Apart from that, it always did what we asked of it and was pretty compact (and being portrait rather than landscape, took up very little shelf space). ;-)
That's the sort of thing I was hoping for, thanks. ;-)
Looking at the price difference (nearly double) and assuming the 5A model really can source 5A continuously (for 8 hours it says) then I might just go with that, certainly for now.
Cheers, T i m
p.s. With the advent of all these electric scooters and cycles, some of which running 36V+ battery systems I'm wondering if a 50V (3A) might be of use to me? Circuitspecialists do a 50V / 3A linear PSU that just sneaks in under my price limit. ;-)
My iCharger can 'boost' the output voltage over the input voltage:
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has the balance feature so I might stick with that for the batteries.
In message snipped-for-privacy@4ax.com, T i m snipped-for-privacy@spaced.me.uk> writes
Tim, should you ever see an advert for a vintage train show, almost any display running 0 gauge or larger will be using Maplin or CSE units. I belong to various groups and hear nothing but praise for them, and use them myself.
There are others, designed for the job, that are just not up to it, particularly all day events, to the extent that people build frames with cooling fans to prevent overheating and cut out. No such problems reported with the Maplin/CSE units. I have also found CSE to be approachable and helpful, should the need arise.
Had a look as I want one too. It doesn't give any clue whether the adjustable current limit shows what it's set to or whether it's adjusted blind. I therefore expect it's the latter. Also beware the 0.2v ripple spec! Also zero info on meter accuracy.
I think that does usually suggest they have found a good solution. ;-)
Oh. ;-(
Similar with RC racing car gear. You often see all sorts of gear at the beginning of a season but they gradually refine towards just a few models towards the end.
That was another question so thanks. ;-)
OOI, do we think that the models shown on the CSE site are in any way different to those (exact looking) sold via the likes of eBay or Amazon etc? Not that CSE's prices aren't competitive etc?
No I wanted one where the current limit was fully adjustable, which on my model it is 0.001A to the max of 5.200A.
the adjustment of voltage or current is achieved by pressing in the control knob to select the decade 10V.1V.0.1V,0.01V and turning the encoder shaft to to desired value. Current setting likewise but
correct, though I would not expct there to be any separate CV or CC modes. With bench psus one simply sets the 2 limits.
0.2v of ripple is terrible for a bench psu. It seriously compromises what it can be used for. It does not lead me to conclude this is a competent unit.
So upto 30.0v
+/- 1% is 0.3v and 2 more digits is +/- a total of 0.5v. That's terrible. No good for me anyway.
Good enough to run motors, but not as a multipurpose bench psu.
So that was a 'yes' then, the current limit thing. Bit isn't that available on most 'current limiting' PSU's, even if they aren't so easy to apply (without shorting the output) or as accurate to set?
I think most people use the current limit as a fuse or to limit the current for charging a car battery, where I don't think you need so much accuracy etc? It could be important when charging a very small battery etc.
I checked out the PSU you have on Youtube and saw that in action and I was wondering how easy / fast it was to use in practice, compared with a straight linear knob etc (the only type I've used).
If I use my Weir linear PSU as an example and charging a car battery. If the battery was a reasonable size then I'd just wind the current to max (assuming a 5A PSU), set the voltage to maybe 14V and connect up. If it was as smaller capacity battery (say off a motorbike) I might want to limit the current to 1A then I'd just turn the current knob up or down till it reads 1A. If it's already fully charged it may only take 1A (at 14V) for a few seconds in any case.
An example of where the selection method of the PSU you have was shown on the Youtube video was where he set a very fine current limit to drive a LED, saves having to bother with a series resistor etc.
I guess it might all boil down to how accurately you want to control the voltage and current and how often you are changing it (along with any other characteristics etc).
My Weir PSUs have a single analogue meter on the front (albeit quite a big one) that you switch between volts and amps (triple reading scale as it can go 0-15V and 0-30V, plus amps etc) and I've found it sufficient for most of the stuff I've used it for so far. If I want more voltage accuracy I just stick a DMM on the thing I'm powering.
The control knobs feel like they are wire would so probably quite expensive. I just prefer the digital display and am not sure I need to go down to that level of accuracy .01 V/A?
That's for bringing it to my attention though and I will consider it further. ;-)
All my PSU's so far have been linear and with analogue displays and controls and so the setting accuracy was really down to the analogue meter and the granularity of the control knobs.
Two Weirs are built like an old skool radio with lots or wires and a fairly large PCB and given most of the stuff on there is likely to be good (or easily replaced), I was wondering if I couldn't take the most faulty one and 'upgrade' it with an LM338 or similar?
I could replace the analogue meter with two digital ones (or a dual one) but I could stick with the analogue meters to start with as that's less to do.
The only thing is it's currently able to be split rail or 0-30 so I'd probably lose the spilt bit (not sure I've ever used it).
Ideally I'd like a kit PCB with all the components on that aren't already in the Weir and start from that. At least I could fault find it if / when it goes wrong. ;-)
I have seen one that suggests the LM338 can be 0-30V and 5A so I could limit the current to 4A to match the existing meter and allow it to run cooler (it has a large passive heatsink across the back).
Cheers, T i m
p.s. I think I'll still go for one of the basic SM PSU's and I'm sure it would be fine for most my needs and I've used one before.
In message snipped-for-privacy@4ax.com, T i m snipped-for-privacy@spaced.me.uk> writes
I think they are identical, although I don't have two units from different sources side by side to compare. Speaking to friends, some have purchased via Amazon or eBay and some (like me) direct from CSE, and all seem the same.
After looking around and starting to get distracted by feature creep, I think I'm now resigned to go for the same as you and yer MR friends and go for the SM 30/5 jobby, partly because of the price (bang for buck), partly because your usage would be similar to mine (running things that aren't 'fussy' about voltage), ease of voltage adjustment and the compact size and light weight.
The strange thing is that with a digital display you can be inclined to try to set the voltage exactly, say 12.00V when in many cases it wouldn't actually matter if it was 10 or 15 (as you are driving a voltage regulator in the first place). When I had the analogue displayed meter you just turned it to 'about' 12V and you were happy to leave it at that (very fast).
I'm comparing that with the 4 digit analogue PSU with the encoder style digit-by-digit adjustment and just wondering if that might become a bit tiresome in use?
Like if you want to go from 12 to 5V (I believe you have to):
Press the voltage knob Turn it to select the units field (2) Press the knob again to select that field Turn it up to 5, (you now have 15V) Press the knob again to enter that value Turn it to select the 10's field (1) Press the knob again to select that field Turn it from 1 to 0 (now saying 5V) Not sure if you have to press it to select 0 or that it times out to
0?
It's similar to setting some clocks.
On the simpler linear adjustment versions and assuming the 'Fine' control knob is set in the middle of it's range.
Turn the 'Coarse' voltage knob down from 12 to 5V, or as near as you can get with that control. If required, turn the 'Fine' voltage control to get a more accurate value.
I bought one from CPC some time ago. Twin unit, and does +/- rails at the push of a switch. Shows voltage and current from both at all times - 4 displays. Badged Circuit Specialists EU. Been very pleased with it. It does 0-50v so useful for testing power amp PCBs.
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