Welcome! Log In Create A New Profile

Advanced

Power supply electricity does not cut off immediately

Posted by jjfawkes 
Power supply electricity does not cut off immediately
May 16, 2019 05:33AM
Hi,
I have a Surom 12v 30a power supply:


When I turn off electricity ( I have an AC Rocker switch wired to it ), it takes a couple of seconds for the PSU to power off.
How can I make it instantaneous?

It's as if the PSU stores the electricity somewhere inside, and once I cut off the AC power, it keeps on powering up my electronics from it's own battery(?). Why is it designed like this?
The switch can't be at fault, because the same thing happens when I unplug the power cable from the outlet - for a couple of seconds everything is still being powered..
Re: Power supply electricity does not cut off immediately
May 16, 2019 05:42AM
That is quite normal, the capacitors in the PSU keep it running a bit. Usually the load on the PSU will cut this short to a few 1/10 sec though. Is the PSU way over spec for the needs of your electronics?


[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]
Re: Power supply electricity does not cut off immediately
May 16, 2019 06:20AM
I haven't tested the PSU with full load, I just started assembling everything and I noticed that this could be a possible issue in the future.
But if you're saying that the time will be reduced to 1/10 sec when it's actually in use, then it shouldn't be a problem.

I am connecting 4 stepper motors, and arduino + ramps + LCD. Heatbed is powered directly from the mains, so I suppose PSU has a lot less to handle because of that.

Thanks!
Re: Power supply electricity does not cut off immediately
May 16, 2019 07:03AM
Without the heatbed powered by the PSU you will always notice this. 30A is way over the top if you don't power the heatbed so the resulting switch off lag will likely be more than a tenth of a second. It shouldn't create any problems though, just a bit annyoing and the efficiency of the PSU won't be very good.


[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]
Re: Power supply electricity does not cut off immediately
May 16, 2019 08:09AM
The Power supply stores power in its filter capacitors, You will never get it to discharge that quickly.

If you want a instant shutoff you should purchase a " Emergency Stop button about 30A should be OK!! ", Do A google search.

Another way is to control the 3D Printer with a raspberry Pi running OctoPrint, this will allow you to have a software controlled Emergency Stop button plugin.

Edited 1 time(s). Last edit at 05/16/2019 07:47PM by Roberts_Clif.


Electronics Technician / Computer Programmer
Re: Power supply electricity does not cut off immediately
May 16, 2019 08:38AM
Quote
Roberts_Clif
The Power supply stores power in its filter capacitors, You will never get it to discharge that quickly.

If you want a instant shutoff the you should purchase a " Emergency Stop button about 30A should be OK!! ", Do A google search.

Another way is to control the 3D Printer with a raspberry Pi running OctoPrint, this will allow you to have a software controlled Emergency Stop button plugin.

Those are good alternatives for the stop button, I will look into both of them.

Thank you!
Re: Power supply electricity does not cut off immediately
May 16, 2019 09:09AM
If you want power off the load (your printer) more or less instantly, you have to interrupt the DC between the power supply and load.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Power supply electricity does not cut off immediately
May 16, 2019 09:20AM
Well, I have one of these ( DPS-750RB ), it takes a few more seconds than a couple to discharge and turn off (if the bed isn't powered) than the one you have, so I wouldn't worry about it smiling smiley .. it's totally normal.



Up to 57Amps these are, very tiny for what they can give, very nicely made, the QC on them is nice. Amazing what you get for around £14 inc postage.

I also have the typical chinese PSU too, I opened it up to check the quality, it was scary. The isolation tracking on the PCB between the rectified mains (the 300V or so DC) was terrible between it and the lower voltage user side, it was dangerous.

Edited 6 time(s). Last edit at 05/16/2019 09:33AM by Pippy.
Re: Power supply electricity does not cut off immediately
May 16, 2019 11:08AM
The power is stored so if there's a glitch on the mains power net it may be able to filter it out without your print failing and keep riple to a minimum, which can interfere with electronics like cpu/microcontrollers.

Some boards rely on a slow power off so it can store the position/layer to resume from that point onwards on next power up. If the power drops too quickly it might not be in time to do that, or even corrupt the file system on the sd card when it's writing.


--
Kind regards
Imqqmi

NFAN CoreXY printer:
[reprap.org]
Sorry, only registered users may post in this forum.

Click here to login