Hi there. I got a switching power source which cannot adjust to output below 21.2 v, i do not want to force the pot, perhaps there is something i'm missing, any suggestions?

It's for a ramps 1.4.




Thanks!

Interesting, there is a very similar post on the Ormerod forum today. I wonder whether one of the Chinese suppliers has got their 12V and 24V PSUs mixed up.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

... my thoughts too

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Viktor
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Call for the project "garbage-free seas" - [reprap.org]

The thing is, i got this one like a year and a half ago. I think i'll have to plug a voltage regulator or something.

I opened the case and look at that big (coil?) clearly says 12v30A.

Plus, i took picture of the caps, perhaps some electrical engineer/hobbyist will know if those are suitable for a 12v PSU:

Probably there is a resistor that takes one value for 12V and another value for 24V, but I would need a schematic to work out which one. There will be other components that change between 12V and 24V, such as the smoothing capacitors on the output, the inductors, and the main transformer.

Edited 1 time(s). Last edit at 10/12/2015 06:52PM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Just a thought, do you have the input voltage switch set correctly?

If I were the developer of this PSU, I'd make the output voltage selectable by bridges on the secondary side of the main transformer.
12V would use two secondary coils in parallel; 24V use them in series.

I see bridges in the picture, but they seem to be for current control ( shunt resistors ) They're only half populated, so I assume it's jumpered for half the max. current ( 24V/15A? )

But it's all just wild guessing...

I have 12V and 24V Meanwell PSUs on the shelf. Will open them today and take a look.
-Olaf

I took some pictures of both PSUs and found some significant differences:

The 12V PSU has two output FETs, were the 24V version has one. Also the smoothing capacitors at the output were different ( 16V vs. 25V )

Compared to the pics you provided, you have a 12V PCB with a 24V main transformer.
The biggest concern is the bank of 16V smoothing capacitors, which eventually will pop!!
Unfortunately I couldn't see any bridges meant to switch the transformer between output configs...

Don't use this PSU!
-Olaf

the transformer in my 30A 12v looks to be identical to GAZ082's

Can you take a close photo of R39, near the variable resistor looks to be different colors to myne (but could just be the photo)

I also notice your power supply does seem to have the standard temperature sensor to turn the fan on and off, mine has a ksd9700 stuffed inside the transformer

Why not use this as an opportunity to switch to 24V?

I made the change and all I had to replace was my hotend heater cartridge and heatsink fan. As a result I have happier steppers and a hotbed that gets to temperature quickly.

YMMV of course, depending on how much 12V specific stuff you have on your printer, but it's worth a thought!

Cheers,
Robin.

Anyone consider that his meter might just be bad?

Just a thought . . .


- Tim

Quote
tadawson
Anyone consider that his meter might just be bad?

Just a thought . . .


- Tim

Well, BAD was the OPERATOR! Haha, i was checking alternate current instead of continuous. :O :O

@Dust: double check your meter!

Don't feel too bad - we've all done something similar.

(But this must set something of a record for how long it took to "spot the deliberate mistake"!)

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Follow my Mendel Prusa build here: [julianh72.blogspot.com]

You are reading 21.1V AC! on your PSU terminals?

Or did you misread millivolt vs. volt?

As former IT supporter we'd called this Error 50, because the error was 50cm away from keyboard
-Olaf

Did you put any load on it ?
Switching power supplies tend to have the output voltage 'float' if there is no current drawn, because they need some load for the reference voltage.
If you want to draw say 10mA at 24V to check you just hook up a ~2400Ohm-ish resistor.

Is the 110v/220v selector switch set for 110v or 220v?