Blowing power supplies
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Just checking the obvious... did you set the power supplies to the right voltage? Not putting 220v on a 110v supply or something?
800w is an amount of power that you should notice if you’re actually drawing that. It’s a small space heater worth of heat going somewhere. I would expect smoking connectors and hot wiring and such to help you track down where the energy is going.
Or, stop buying crap power supplies
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@rcarlyle said in Blowing power supplies:
Just checking the obvious... did you set the power supplies to the right voltage? Not putting 220v on a 110v supply or something?
Yes. Definitely set to 220v, on the two that are selectable. The other was sold as a 240v model.
800w is an amount of power that you should notice if you’re actually drawing that. It’s a small space heater worth of heat going somewhere. I would expect smoking connectors and hot wiring and such to help you track down where the energy is going.
Yeah, this is the bit that's weird for me. I was using 14AWG wire, and it was warm after powering the heater. But definitely not hot to the touch. 33c at the highest at the screw terminals via IR gun. And the heater wire, was cold. Room temperature.
I really don't want to be plugging in new power supplies, to blow them, considering that.
Or, stop buying crap power supplies
I'm now less convinced it was due to quality. They'd all lasted for a substantial amount of time on my other large printers.
@opentoideas said in Blowing power supplies:
@mortarart its possible that they ran out of the 1.03 and you got lucky and have the 1.04
Compare them here www.duet3d.com/DuetWifi
As for power supplies it depends some have no adjustment and even if they do its only a couple of volts either way. Just be sure to check with a meter before connecting up.Now I'm very confused. Mine has one large fuse. That image clearly has two fuses. The Duet 1.03 image has zero. I'm hoping I don't have some experimental model that is frying power supplies.
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Definitely says 1.03 on the board.
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well there are a few things. did you buy your duet from an authorised reseller or could it be clone? the clones are similar but can be slightly different eg. printing may say "based on v1.03 design"
you also really need to measure the resistance of the heater. if you have for example a 12V heater then at 24V it will be 4x the power but in that case I think the Duet would have been unlikely to survive but without numbers its difficult as anything could be going on.
do you have a multimeter?
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@mortarart said in Blowing power supplies:
Now I'm very confused. Mine has one large fuse. That image clearly has two fuses. The Duet 1.03 image has zero. I'm hoping I don't have some experimental model that is frying power supplies.
The v1.04 image has 3 fuses, not 2.
The Duet v1.03 image is actually an image of a Duet v1.0.
You don't have anything experimental, you're just using generic Chinese power supplies, and they're failing because they are poor quality, plus you're running a higher load than most.
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@opentoideas said in Blowing power supplies:
well there are a few things. did you buy your duet from an authorised reseller or could it be clone? the clones are similar but can be slightly different eg. printing may say "based on v1.03 design"
He got it from Duet3D, this is apparent from his original post in which he refers to the "on special batch".
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I saw that but the supplier is not mentioned and likewise I made the same assumption as I considered that special when I bought mine last week but it could also be the special sale on Aliexpress for example which is why I wanted to clarify as the description sounds more like these with the fuse issue.
these are the only way i can see having a fuse on a 1.03 board
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Just a quick reply to a few things. My original Duet Wifi (from the late beta batch) was from Duet3D. The Duet 1.03 is also from Duet3D. I do have a 0.6 Duet from Replikeo, but I don't use it anymore. Happy to provide screenshots of my receipts for proof if it's still being questioned.
I do have a multi-meter. I've been focused on power supply repair since, so that's why I haven't gotten around to checking the bed. I'll be attempting to replace the parts that I identified above.
All my other hardware either comes from e3d, or Robotdigg, except the 400 & 800w supplies.
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LOL I am as confused as you then about your fuse on a 1.03 board.
just noticed @elmoret mention the photo is on the website is not a 1.03 board so I guess they did have a fuse then???
either way hope you have some good luck with repairing the blown PSU's and get up and running again soon.
I can sympathise, I was just getting to grips with Duet and broke my hotend so stuck waiting on parts myself
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In theory, this COULD be multiple good PSUs failing due to a shorted load, but I’m leaning against that because good PSUs should have short protection that kicks in on overload before they fry. Not saying that always works, but it ought to. I’ve hard-shorted a Meanwell before with a big ol’ spark and it just went into protection mode until I power cycled it.
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The input fuse in a switched mode PSU should only blow if the PSU develops an internal fault, such as a blown switching transistor or capacitor. It will also blow if you exceed the rated input voltage by a sufficient margin, e.g. because the PSU has a 100V/220V switch and you feed it 220V with the switch in the 110V position. It shouldn't blow otherwise, even if you short the output of the PSU.
A continuous small overload might cause one of the switching transistors to overheat, resulting in eventual failure and the fuse blowing. Cheap PSUs do seem to have short-circuit protection, but I don't believe they monitor output current to detect lesser types of overload. With a low-quality PSU the transistors may even be running too hot even at or a little below rated output. That's why an output power safety margin of 20% or so is often recommended.
Failure of the PSU cooling fan could have a similar effect.
You haven't told us the resistance of your bed heater, so we can't work out the total load on the PSU. But 800W should be more than adequate.
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I just measured the resistance of my bed heater, but I'm really unsure I'm doing it right. My multi-meter gets a resistance of 7.5 between it's pins, and the heater returns a resistance of 8.5ohm.
I am about to find the method for calculating wattage, but I really feel like 1ohm is odd.
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@dc42 said in Blowing power supplies:
The input fuse in a switched mode PSU should only blow if the PSU develops an internal fault, such as a blown switching transistor or capacitor.
Given that the 400w power supply first blew the fuse on the IEC plug, then turned on briefly before it's input fuse died, I believe there must've been an internal fault? My assumption is still with over draw.
I've also since seen that 1ohm is in the ballpark of other heaters.
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I found some alligator clips, to get a better hold on the heater crimps. 1-1.1ohms.
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@mortarart said in Blowing power supplies:
I found some alligator clips, to get a better hold on the heater crimps. 1-1.1ohms.
If this is true then you bed needs at 12V a 144W but at 24V it need already 576W. So the 800W supply should get the job done, but the question what quality it was. And at 24V this would over-current the Duet any way since it is rated at 15A and at 24V you bed drivers 24A.
My personal opinion is - if you bed draws alone over 500W, go with mains power bed (I know they are many safety doubts but handling over 20A isn't really safe to - burning connectors, blowing power supplies). -
If it’s really 1 ohm, then yes, that’s a bit of a concern at 24v. Problem is, many multimeters don’t measure accurately at very low resistances. So it could be 1.1 or 1.4 or 0.8 or whatever, we don’t necessarily know.
I would personally not put more than 10A or so on any circuit not wired by an electrician. It’s just an unreasonable amount of amperage for a hobbyist to be dealing with. Typical low voltage terminals and connectors aren’t intended to go that high. Particularly when you factor in de-rating requirements due to adjacent terminals carrying power, or higher ambient temps. There’s a reason heatbed connectors burn up all over the place in the 3D printing world. Yeah, the Duet is good to 18A, but that’s still a LOT of current. And 24v at 1 ohm is more than 18A...
Is the 800w PSU intended to be run with full load on one output? For example, a lot of ATX PSUs have multiple 12v rails and each can only handle a portion of the total rating. Don’t know if that applies here.
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I was running on two rails on the 800w and 350w supplies. How viable is it for me to run the bed off of a massively turned down power supply, via an SSR? If I run it at 18v, it should only draw 324w...
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@mortarart said in Blowing power supplies:
I was running on two rails on the 800w and 350w supplies. How viable is it for me to run the bed off of a massively turned down power supply, via an SSR? If I run it at 18v, it should only draw 324w...
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Also seriously look to get a quality supply.
A good second hand PSU will likely set you back less than a rubbish new one.(and be FAR superior and last longer)
This just cost me £20 on fleabay and was local!
0_1536054740525_1536054706811947497414.jpg
600W with modules for 12V and 24v
Protected against overload thermal trips etc and remote switchable.
There are loads of quality industrial supplies out there for a fraction of what they would cost new and all this one needed was a new £1 fan I already had lying around
p.s. please excuse the mess this is only a temporary testbed as the bits just arrived! first prints will be a case for the duet and a tidy up of all the wiring!
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and yes lowering the voltage on the bed will reduce the power. thats why I got the PSU I am using. I have one 200W 24V module that is dedicated to the Duet and a pair of 200W 12V modules I can link for the bed heater (mine is 12V).
if and when I can upgrade the heater to 24V and have a 360W 24V module I can use - its an unusual PSU!
