24V Supply with voltage adjustment

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Sari33
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24V Supply with voltage adjustment

Just found this 24V supply
https://www.aliexpress.com/item/-/32921010516.html
Seem well spoken by feedback but there isn’t info about protections or noise at heavy loads
this is a photo with case opened (36V model)
from AE feedback
http://www.aliexpress.com/item/1005001664514099.html

What you think,value for money or not?

Edited by: Sari33 on 06/08/2021 - 06:21
Robin Dobbie
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Quote:
Seem well spoken by feedback but

Sometimes there are ways to judge a potential purchase by evaluating visible feedback, but the presence of positive feedback isn’t one of them. Sadly, I’ve just learned this the hard way with a “charger” I bought on there that outputs 17.48V when its supposed to cut off at 16.8. At 17V, with the current it was still pumping in, I would have needed 20 of those little balance boards in parallel to keep the damn thing from cooking my cells.

All the feedback was super happy happy joy joy time! Except one guy from France who was like, hey, this putting out 17.52V!

I don’t know if that high voltage would have dissuaded me because I do have a charger that, with no load, has nutty voltages. Soon as you put the device on there, the voltage is what it’s supposed to be, and it stays there when it hits 8.4V and stops. Soon as you take off the doodad, BOOM! An extra volt or two appears.

What sucks is, now, I remember seeing a youtube video about this piece of shit, however long ago, …and I bought it anyway. Facepalm Facepalm Facepalm

So, what’s the lowest voltage you’ll actually need?

Sari33
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unfortunately this happen with products made by unknown and aliexpress is full of them.
Yes,positive feeds often have no value because there are people who give them without trying the products, that’s why I check negative feeds.A fragile point of this supply can be the carbon potentiometer,seem wh148 series.they are smooth but don’t know for how many cycles rotation works.
I wanted use this supply for adjust brightness of a 24V Led strip without additional dimmer and pwm or use it for general purposes

Lightbringer
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Yeh, those beasties are hit or miss, and you gotta check each one individually. And forget about returns.

That said, a lot of switchers are notoriously unstable at light/no loads. Remember the old PC/ATs that needed the big honkin’ resistor in a cage to draw a fake load if no… hard-drive?… was present?

I’ve been pretty lucky so far, but I might lose the lottery next time I’d need one of those.

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Robin Dobbie
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How many watts? For LEDs, probably better if you found a used high quality 12V power supply and one of those 150W or even 400W boost converters with a constant current adjustment. They have tiny little pots, but you can add a larger one. Max out the voltage and use the current adjustment for dimming. You might not need 150 or 400W, but about 45 – 50 watts is about as much as I’d use them for without a fan.

jeff51
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Amazon US is loaded with 12 and 24 volt LED power supplies.
A few bucks more but quicker to arrive and return if it’s a brick.
Don’t know what’s available in the EU.
All the Best,
Jeff

Sari33
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Videoreview of this supply with opened case at min.7.40,
https://youtu.be/WsFouHsBo64
Don’t understand well what he said if is a good unit or not. It pull out 2A at 24V
Exit wires seem thin but can be easy replaced,the box is press fit hold by clips
What I need is a decent compact unit with knob and display for medium loads.
If you know a model like this but from famous brands as Mean well
I’ll buy on Amazon if available
Greetings

Robin Dobbie
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Someone opened the one I bought and posted a picture on aliexpress. I guess there was a sale on gigantic power supply boxes.

One thing I noticed is the weight given on the sale page is 200g, mine weighs about half. 148 with the power cord, but why they even needed to add the weight I don’t know because most pages I’d seen don’t even list that.

A generic laptop charger that’s smaller and weighs twice as much.

Sari33
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Robin Dobbie wrote:
How many watts? For LEDs, probably better if you found a used high quality 12V power supply and one of those 150W or even 400W boost converters with a constant current adjustment. They have tiny little pots, but you can add a larger one. Max out the voltage and use the current adjustment for dimming. You might not need 150 or 400W, but about 45 – 50 watts is about as much as I’d use them for without a fan.

You mean add on the exit of my mean well 12V supply one of these boost?
https://www.aliexpress.com/item/32958518616.html
It’s an option, but for what I know it increase also noise if used near or with Audio devices.
There are filters that I can add? The blue trimmer also need to be replaced by a knob.
I have on the way these https://www.aliexpress.com/item/1005002717551701.html
The seller kindly mixed the order with all values for 10pcs as my request,ordered also some wh148 pot.
Robin Dobbie
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Yeah I’m using those boosts in a couple projects right now. I have 5 going for some plant lights, then I have another right on top of my speakers as my bedroom light doing ceiling bounce with a 100W COB at 60W. At 60W it needs a fan. At the voltage I’m running it’s intaking about 3.4A. At 2.5A IN it could run fanless.

I hadn’t noticed RFI noise from them, but I’m not exactly an audio expert and I have a window unit AC that drowns out a lot. I do have a server power supply that I floated the ground(I just disconnected the chassis and the negative output from ground) and it makes audible noise through the speakers now when powered on. Same power supply model un-modded does not do it, or at least that I can detect. In both cases I was using the 400W boost at a similar power level.

Speaking of server power supplies, that’s what I ended up having to use to combat inrush problems I had with my mean well when using these boosts. With different power supplies from laptop PSUs to a 350-watt mean well, I’ve found that the inrush causes problems if starting LEDs that are drawing significantly more than I dunno… about 35% of the rated power of the supply. 460W server power supplies are like £9.99 on ebay.co.uk, so, that’s something to look at. Make sure you’ll know how to turn it on before you buy them. I have some I know how to turn on, some that are a puzzle for another day. Many people have documented the HP server PSUs so that’s a place to start. I have some of the blue label ones and it’s easy to get those going and the fan is very quiet.

Sari33
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Good to know that there is not audible noise with these boost modules.When I on my powerbank,the Radio is not audible.
Hope also pwm will be not visible or at least above 30KHZ.
Don’t know if they have overload or short circuit protection
If isn’t present, would be better put fuses in and out calculating the max load supported ?
I have also others 12V Led strips to dim.
My MN LRS 150 12 have trimmer voltage regulation 10.2-13.8V (marked on red)
Can I replace it or add with solder wires a knob potent. like WH148 with different resistance value to go below the 10.2 volt?
On the green arrow we can see the Mosfets are full covered by rubber caps.So strange,they don’t contact direct with metal case.How they can spread heat?

kennybobby
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That’s an interesting idea, but it would require an examination of the schematic to understand how the potentiometer controls the voltage.

The rubber caps are strange, but the devices are clamped to the aluminum case for conduction cooling.

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Robin Dobbie
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To be clear, I can’t hear any noise with my setup and ambient noise pollution, that doesn’t mean there isn’t any. I use optical out from the source, that goes on to a DAC, then “shielded” cables to the amp. I don’t have audiophile speaker cables or anything. Could be a lot better, could be a lot worse.

The PWM should be around 150kHz. If any of the ads on those are accurate.

Maybe someone with more experience can comment on controlling LEDs from power supplies with the exact same voltage. It isn’t something I thought was a good idea. Supposedly you need a good voltage difference of a couple volts for a buck(step-down) and possibly more for boost.

Sari33
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Robin Dobbie wrote:

Maybe someone with more experience can comment on controlling LEDs from power supplies with the exact same voltage. It isn’t something I thought was a good idea. Supposedly you need a good voltage difference of a couple volts for a buck(step-down) and possibly more for boost.

I was thinking what type of driver with tension regulation can be used If connect a 12V 4A strip on 12V battery
Linear driver? The LM317 have 2-3V Drop out that is too much and limited output
Imho put them in parallel the exit current will not be equal and one will heat up more.