Need a 0.5 sec UPS (prolonging agony for resurrection)
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@droftarts Thanks a lot! OK, a 10mF capacitor, connected to the two 24v leads via a Schottky diode and a resistor (both in parallel to each other) would do the trick. I understand how this works. I would figure out the value of the resistor to limit the current, but I have no idea how to choose the Schottky diode.
Would anyone indicate a particular Schottky diode as a possible example for this purpose? Otherwise this will be trial and error for me.
And yes, I know that I have to care about the polarity
. This simple circuit is nothing more than a kind of downsized DC UPS controler, and I would even have expected to find a board with a similar function but I couldn't. I don't think I am the first one coping with such a question, as many different devices need to be shut down in a controlled fashion (think of a NAS storage for example). -
@samlogan87 Yes, I have already read that article a couple of hours ago. I found the solution very attractive but my concern is not to run the printer any long time at an outage. There are virtually no power outages in the country where I live, except very short ones most people won't even notice (probably caused by a more challenging management of the public power grid due to a large and increasing share of renewable, but discontinuous power sources). Right now I am running a 23 h print and I have no ambition to use a UPS for that. Frankly, I even suspect something is wrong in the electrical installation of my house.
After looking at the DC UPS mentioned in the article I found them to be oversized solutions for a 0.5 sec problem, and I thought I would find something similar, but self-powered, essentially like a supercap. I could only find supercaps for 12v only, for whatever reason.
Deckingman passed by? Well that's a loss indeed. He was an enthusiastic and respected comrade in the 3D printer community.
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@Triet you can connect supercaps of the same type and value in series, with parallel resistors to help keep the voltages balanced. For example, ten 10F 2.7V caps in series with a 100 ohm resistor in parallel with each one will give you a 1F 27V capacitor. Charge/discharge them through a 100 ohm 6W resistor and parallel Schottky diode.
Don't forget that after turning power off the supercaps will still power the board for some time, so wait until the LEDs have all turned off before doing any work on the system.
Duet WiFi hardware designer and firmware engineer
Please do not ask me for Duet support via PM or email, use the forum
http://www.escher3d.com, https://miscsolutions.wordpress.com -
@dc42 Of course! Why didn't I myself come to the idea of combining several capacitors, so having even more design flexibility.
You gave me the decisive impulse to start this task. I would even use the remaining power to run the hotend fan a bit longer to avoid nozzle clogging after a sudden heater shutoff.
By the way: What I most appreciate using Duet hardware is... this help forum, definitely (beside their indisputable quality). Sincere thanks!
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@dc42 I wanted to wrap up some informations about this topic but found that I am not allowed to post links - I need two "reputations".
That's a pity. Would anyone be so kind to enable posting links for me? At least for this time. (Assuming that my findings are of general interest for the furure).
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@Triet you should be able to now
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There is quite a discussion here:
Also - if you don't want to build - something like this may be OK for your needs.
https://github.com/bigtreetech/BIGTREETECH-MINI-UPS-V2.0/tree/master/BTT UPS 24V V1.0 -
@stuartofmt I just read that discussion, looks a bit chaotic but the hint about the BTT Supercap UPS is valuable.
@T3P3Tony Thanks!I just wanted to clarify that it is really not necessary to build a pack of supercaps yourself. I was looking around and found some solutions. Often, supercap modules are offered to be used in automotive applications to protect the vehicle battery from to sudden current surge or to stabilize board voltage to satisfy hifi equipment (music listening people tend to be very demanding when it comes to sound quality).
For example, this one:
5PCS 1Set Super Capacitor 13.5V 12F Single Row Farad Capacitor2.7V 60F Automotive Super Farad Capacitor Module Supply Rectifier
Of course this would only be suitable for a 12V power supply, but you can connect two of them in series. This boards have voltage protection and balancing built-in. They are even oversized for this case (remember: the purpose is to allow a controlled shutdown, not to run the printer on UPS).For more ambitious people, a 24V module is also available, for about $100 on Amazon, or around $21 on AliExpress:
GDCPH 24V5.5F Supercapacitor Electronic Rectifier Module 2.7V50F Super Farad Capacitor Backup Power Supply 24.3V Electrolysis
Note that it is composed of 9x50F supercaps in series (resulting in 5.5F), which is plenty of energy.
Still, these are not full fledged UPS - you still need the combo of resistor and Shottky (in parallel to each other) between the module and the PSU.I even found a supercap module exactly as @dc42 proposed, if using two of them in series:
[16V 1F/2F Farad Capacitor Module 2.7V 10F Super Capacitors With Protection Board]
(https://www.aliexpress.com/item/1005002715223142.html)
You get one module for $6 or two for about $12, fairly affordable. That is currently my preferred option. The BigTreeTech 24V UPS mentioned above does not add any value because the Duet already has a power failure detection built-in.My impression is that supercap based UPS are becoming popular. There are some professional solutions, for example customized for a Raspberry Pi (if you use one):
Andino-UPS - Supercapacitor UPS for the Raspberry Pi
but I also found some DIY projects. They should be considered as "emergency power supply" rather than UPS due to the limited length of time they can keep a printer running.Engaging in this matter I have some new questions and ideas, namely: I would like to switch my printer on remotely (it is in an attic and I always have to go upstairs to switch it on) - a reversed question in comparison.
But also: What happens when I just switch the printer off in a regular manner when resurrection has been configured? The voltage will drop to the defined threshold in this situation too- will then the power failure procedure defined by M911 be executed? I have never checked that. OK, as a rule, no print job is running when I deliberately switch my printer off, so I suppose the procedure is only triggered in this case.
Why I come up with this question?
Assume that I have a small UPS that is able to detect failure of the mains power. It does not have to wait until DC voltage drops below say 22.5V to kick in. I can then save current coordinates and take some other precautions to prepare the resurrection, even before the voltage threshold is reached. Will then the power failure procedure defined with M911 still be executed a 2nd time when the DC voltage falls?A real UPS has one key advantage compared to an emergency power supply, even when it is not meant to run the printer accross the powerless time, since it allows to keep the hotend fan running for a couple of minutes until the hotend gets cold enough, so to avoid nozzle clogging. In this case, the question whether M911 kicks in and saves the current state a 2nd time would be relevant.
I am done.
Thanks again. -
@Triet said in Need a 0.5 sec UPS (prolonging agony for resurrection):
But also: What happens when I just switch the printer off in a regular manner when resurrection has been configured? The voltage will drop to the defined threshold in this situation too- will then the power failure procedure defined by M911 be executed? I have never checked that. OK, as a rule, no print job is running when I deliberately switch my printer off, so I suppose the procedure is only triggered in this case.
M911 is only triggered when the supply voltage falls below the auto save threshold while a print from SD card is in progress. So turning off the printer when idle will not trigger it.
@Triet said in Need a 0.5 sec UPS (prolonging agony for resurrection):
A real UPS has one key advantage compared to an emergency power supply, even when it is not meant to run the printer accross the powerless time, since it allows to keep the hotend fan running for a couple of minutes until the hotend gets cold enough, so to avoid nozzle clogging. In this case, the question whether M911 kicks in and saves the current state a 2nd time would be relevant.
M911 is triggered by a voltage drop. If there's no voltage drop, because the UPS has kicked in, then the firmware would be oblivious. If there's an output from the UPS to indicate that it's running, that can be connected to a Duet input, then you could create a trigger and macro to accomplish this.
Ian
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Triet
15 Jan 2025, 02:19
@Triet said in Need a 0.5 sec UPS (prolonging agony for resurrection):
I just read that discussion, looks a bit chaotic ...Fee flowing discussions usually are
@Triet said in Need a 0.5 sec UPS (prolonging agony for resurrection):
I would like to switch my printer on remotely (it is in an attic and I always have to go upstairs to switch it on) - a reversed question in comparison.I use Shelly products for this type of functionality (there are of course others). They are essentially WIFI equipped relays with built in http commands. The ones I use are powered by and switch mains voltage.
https://www.shelly.com/collections/smart-switches-dimmers
They are small and can even be fitted in a wall socket (if its deep enough). I have a Shelly 1 mounted in a small box (printed of course!) attached to my printer. That way I can remotely turned the printer on / off from a browser (or app that issues http).
Hope this helps.
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@stuartofmt I am looking at different options and learned about a switch with a ESP8266 NodeMCU microprocessor, which is more elegant and flexible. It runs a Webserver as well.
If you are interested:
ESP8266 Button -
@Triet said in Need a 0.5 sec UPS (prolonging agony for resurrection):
@stuartofmt ...which is more elegant and flexible.
Than ? I guess it all depends on build vs buy. If you want to go down the buy route - you will find the Shelly has way more out-of-the box capability (than ESP8266 NodeMCU microprocessor) with no need for programming / building.
I'm not plugging Shelly just offering an idea. Way back, I considered building but for ~$15 to buy ... well you see where I am coming from
