Resume from power outage, really only with 24V?
-
@arhi said in Resume from power outage, really only with 24V?:
@the_dragonlord easy, these big caps have huge ESR so they take a while to charge, for e.g. the one on the picture is 0.5 - 0.8 ohm. Also those 5F ones to make 1F higher voltage one are also huge ESR so they all take a while to charge so they will not kill the PSU.
you ordered 10x1000uF, that is 10x lower ESR than a single 1000uF. Depending on what 1000uF you purchased (if you got some high quality low ESR ones, especially) they can have low esr, and when you divide it by 10 it will get even lower and in that case they can pull A LOT of current from the PSU and trigger overcurrent protection (or PSU will just die) so in that case you need a slow start circuit (basically a time relay and resistor, for few seconds you charge the caps trough resistor and then after few seconds relay shorts the resistor and you don't waste any more power heating the resistor) ... or if you don't know how to make a slow start circuit and have an old dead PC PSU, you can get PTC from the old PC PSU and use that for current limiting
e.g. this is 80mR ESR
this is 50mR ESR:
so if you for e.g.-
get that 22000uF
it will have 15A inrush current -
get that gloria 10000uF
it will pull from the 12V rail 140A -
get that gloria 3300uF
it will pull from the 12V rail 240A -
if you put 3 of those 3300uF in parallel to get 10000uF
it will pull from the 12V rail over 700A inrush current
will your psu survive any of those I can't say, the e.g. crappy psu that came with ender5 survives the 15A when you connect the 22000uF but does not survive any of the other ones..
so your hint is to buy a single "great one"
-
-
@the_dragonlord said in Resume from power outage, really only with 24V?:
Thanks
I'd rather go with something like this, if there is no option to add slow start circuit:
or like this
but ideally:
-
@the_dragonlord said in Resume from power outage, really only with 24V?:
so your hint is to buy a single "great one"
you already ordered 10x1000uF, just get 50W 1R resistor and add to them so you will add 1R to their ESR making them "low esr" caps
and it should work ok for what you need. -
@arhi said in Resume from power outage, really only with 24V?:
@the_dragonlord said in Resume from power outage, really only with 24V?:
so your hint is to buy a single "great one"
you already ordered 10x1000uF, just get 50W 1R resistor and add to them so you will add 1R to their ESR making them "low esr" caps
and it should work ok for what you need.in your opinion how many of them should I use in parallel? With 1 Ohm resistor about, depending from total capacity, what would be the peak current?
-
@the_dragonlord said in Resume from power outage, really only with 24V?:
in your opinion how many of them should I use in parallel? With 1 Ohm resistor about, depending from total capacity, what would be the peak current?
how many you have
with 1R resistor (note you need 50W, not the 1/8W one ) the peak current will be, assuming you put enough caps in parallel their total R is 0, so worse case scenario: I = U/R so 12V/1R = 12Aget 2 of those 1R resistors and see if 1R is too much, you can connect 2 in parallel to get 0.5R doubling that to 24A of max current that's acceptable by most psu's
-
If the capacitor is connected directly to the PSU, then the slow-start behaviour of the PSU will generally limit the inrush current to a reasonable value.
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 -
@arhi said in Resume from power outage, really only with 24V?:
@the_dragonlord said in Resume from power outage, really only with 24V?:
in your opinion how many of them should I use in parallel? With 1 Ohm resistor about, depending from total capacity, what would be the peak current?
how many you have
with 1R resistor (note you need 50W, not the 1/8W one ) the peak current will be, assuming you put enough caps in parallel their total R is 0, so worse case scenario: I = U/R so 12V/1R = 12Aget 2 of those 1R resistors and see if 1R is too much, you can connect 2 in parallel to get 0.5R doubling that to 24A of max current that's acceptable by most psu's
I can put even all 10 of them in parallel, I haven't problem about the space to place them... 12A is acceptable, I have a 650W ATX power supply... i think the current peak will last few milliseconds, right? .... so 10 capacitor in parallel with 1 Ohm 50W like in your schematic and I will be fine, right?
-
wrt those 50W 1R ... you can see 2 50W resistors here on this 220VAC slow start, they are different value but it's the "physical size / case" you are interested in ...
-
@dc42 said in Resume from power outage, really only with 24V?:
If the capacitor is connected directly to the PSU, then the slow-start behaviour of the PSU will generally limit the inrush current to a reasonable value.
yes, it will be connected in parallel
-
@the_dragonlord said in Resume from power outage, really only with 24V?:
so 10 capacitor in parallel with 1 Ohm 50W like in your schematic and I will be fine, right?
yes, even 20 or 30 will be ok, the 1R might be too much for 10 caps, you might want to put 2x1R in parallel to get 0.5R to allow for bit faster charging (and later discharging)
-
@dc42 said in Resume from power outage, really only with 24V?:
If the capacitor is connected directly to the PSU, then the slow-start behaviour of the PSU will generally limit the inrush current to a reasonable value.
it depends heavily on the PSU, bunch of high quality PSU's will not output anything till 12V is stable and pulling 240A from them will trigger overcurrent immediately.
the low quality ones will rise the output voltage from the 0 so the caps on the output will only slow down the time it takes to reach full 12V so no res would be necesary
-
@arhi said in Resume from power outage, really only with 24V?:
@the_dragonlord said in Resume from power outage, really only with 24V?:
so 10 capacitor in parallel with 1 Ohm 50W like in your schematic and I will be fine, right?
yes, even 20 or 30 will be ok, the 1R might be too much for 10 caps, you might want to put 2x1R in parallel to get 0.5R to allow for bit faster charging (and later discharging)
well, it depend how much the resistors are... in my opinion shouldn't be better to make the capacitors to discharge as slowest it's possible to give the board the needed time to save the position and raise a little the Z?
-
@arhi said in Resume from power outage, really only with 24V?:
@the_dragonlord said in Resume from power outage, really only with 24V?:
so 10 capacitor in parallel with 1 Ohm 50W like in your schematic and I will be fine, right?
yes, even 20 or 30 will be ok, the 1R might be too much for 10 caps, you might want to put 2x1R in parallel to get 0.5R to allow for bit faster charging (and later discharging)
with 1R you mean 1 Ohm, right?
-
@the_dragonlord said in Resume from power outage, really only with 24V?:
@arhi said in Resume from power outage, really only with 24V?:
@the_dragonlord said in Resume from power outage, really only with 24V?:
so 10 capacitor in parallel with 1 Ohm 50W like in your schematic and I will be fine, right?
yes, even 20 or 30 will be ok, the 1R might be too much for 10 caps, you might want to put 2x1R in parallel to get 0.5R to allow for bit faster charging (and later discharging)
well, it depend how much they are...
0.5-5$ depends on availability, quantity..
https://www.digikey.com/en/products/detail/ohmite/TWW20J1R0E/11689204...
in my opinion shouldn't be better to make the capacitors to discharge as slowest it's possible to give the board the needed time to save the position and raise a little the Z?
no as if they cannot deliver enough current voltage will drop before you use up the energy from the caps and duet will shutdown sooner than you would like ... you need to allow duet to pull as much current from them as it needs, ideally you only limit inrush current, that's while slow start circuit is best option
-
@the_dragonlord said in Resume from power outage, really only with 24V?:
with 1R you mean 1 Ohm, right?
yes.
btw, depending on the quality of the PSU, it might work without any res, so try first (no need to connect duet, just connect those caps in parallel on the output of the psu), if the psu shuts down you need res, if it works ok you don't need it
-
@arhi said in Resume from power outage, really only with 24V?:
@the_dragonlord said in Resume from power outage, really only with 24V?:
with 1R you mean 1 Ohm, right?
yes.
btw, depending on the quality of the PSU, it might work without any res, so try first (no need to connect duet, just connect those caps in parallel on the output of the psu), if the psu shuts down you need res, if it works ok you don't need it
well if it only shut down it will be ok, i didn't want to burn it
-
@the_dragonlord said in Resume from power outage, really only with 24V?:
well if it only shut down it will be ok, i didn't want to burn it
any half decent PSU will have overcurrent protection .. IMHO if it burns from adding 10x1000uF on the output you should not have bin using it in the first place
... anyhow you can minimize the chances of a death by- power with only 1, poweroff
- power with 2 in parallel, poweroff
... - power with all 10 in parallel, power off
-
@arhi said in Resume from power outage, really only with 24V?:
@the_dragonlord said in Resume from power outage, really only with 24V?:
well if it only shut down it will be ok, i didn't want to burn it
any half decent PSU will have overcurrent protection .. IMHO if it burns from adding 10x1000uF on the output you should not have bin using it in the first place
... anyhow you can minimize the chances of a death by- power with only 1, poweroff
- power with 2 in parallel, poweroff
... - power with all 10 in parallel, power off
ook, the ATX power supply I own should be mire than decent (I hope)... I realized I have some old power supplies, I see if I found some "big beast" capacitor...
-
@the_dragonlord then it has overcurrent protection so no worries there
as for the caps you can find in, there are two rather big ones on the input .. worse the psu bigger those caps are
(high end psu's have rather small ones as they have active input opposed to gretz+cap on the crappy ones) ... but those are 400V caps (200V in really crappy ones), 100-500uF capacity .. so they can hold lot of energy but are not usable for your case. on the output you should have few 1000-3300uF 16V ones that you can use.... look at the input of these psu's immediately after the fuse there's a "disk" part that's a PTC... that might be used but dunno what the actual properties here are as these are meant to run lower amps and more voltage so.. -
@arhi said in Resume from power outage, really only with 24V?:
@the_dragonlord then it has overcurrent protection so no worries there
as for the caps you can find in, there are two rather big ones on the input .. worse the psu bigger those caps are
(high end psu's have rather small ones as they have active input opposed to gretz+cap on the crappy ones) ... but those are 400V caps (200V in really crappy ones), 100-500uF capacity .. so they can hold lot of energy but are not usable for your case. on the output you should have few 1000-3300uF 16V ones that you can use.... look at the input of these psu's immediately after the fuse there's a "disk" part that's a PTC... that might be used but dunno what the actual properties here are as these are meant to run lower amps and more voltage so..ok, I'll check the psu later... last question : increasing the total capacity what's the benefit in terms of "energy" and time given to the board? I mean how much better for my purposes is a 10.000uF related to a 1.000uF and a 22.000uF related to a 10.000uF and so on?
