Considering a 12v to 24v upgrade? DO IT!



  • Hello! I recently started having issues where my printer would brown out only when using the heated bed. I had been using the bed for many months happily but since a recent firmware update, it just wasn't cooperating. Most of the things I found googling this issue suggested replacing the wiring or PSU, so I figured now is the time for 24v.

    I spent $20 on a 240W 10A 24v power supply and it totally fixed my browning out issues. Previously I would get "voltage low" errors until the brownout occurred, but it's now printing like a champ sticking around 24v.

    Swapping out was pretty painless, the board accepts 12/24v readily, I had a small little circuit I made to make my bed sensor play nice with the duet and I put a small box I got off amazon that steps 24v down to 12v so I can keep printing now and fix this "less than perfect" thing later.

    If you are still on 12v with your duet... upgrade! it's awesome! Heated bed reaches temp SO MUCH FASTER now... fans are louder which leads me to believe they were previously starved for power/voltage.



  • @dirtybirdnj said in Considering a 12v to 24v upgrade? DO IT!:

    fans are louder which leads me to believe they were previously starved for power/voltage.

    uh.. more likely the fans are 12v and are now being over volted. They will run faster and eventually burn out. You can use a buck converter to supply the fans with the proper 12v. https://duet3d.dozuki.com/Wiki/Connecting_and_configuring_fans#Section_Using_12V_fans_when_VIN_is_24V

    Hopefully you changed the hotend heater to a 24v cartridge at least? Running a 12v cartridge at 24v is a fire hazard.



  • @dirtybirdnj

    upgrade! it's awesome!

    Can’t share your enthusiasm. @Phaedrux is absolutely right, I just want to extend his warning: running a bed heater specified for 12 V with 24 V is a fire hazard, too. At least it is a proven way to reduce the lifespan of the heater considerably.



  • Assuming the cartridge heater and bed heater were not already passively safe (ie would never reach hazardous temps if left at 100% duty) are there safety issues with modulating the heater to match the power rating to 12V?

    Edit: Also do the cartridge heaters need a heat sink in order to operate safely at 100% duty at rated voltage?



  • @DocTrucker , what makes you think that cartridge heaters or bed heaters are 'passively safe' ?



  • interesting timing on this thread - I was just looking at 24v and considered that I would either need to use buck convertors for existing 12v component (heater cartridge/bed/fans) or replace. For safety I think the components should be driven at their design voltages, not pushed by using 24v.



  • @dirtybirdnj said in Considering a 12v to 24v upgrade? DO IT!:

    I put a small box I got off amazon that steps 24v down to 12v so I can keep printing now and fix this "less than perfect" thing later.

    It looks he has buck converter. But this is still not ideal.



  • @jens55 said in Considering a 12v to 24v upgrade? DO IT!:

    @DocTrucker , what makes you think that cartridge heaters or bed heaters are 'passively safe' ?

    I wasn't making a statement. More that some people advocate and aim for what they describe as a passively safe system whereby the heaters are incapable of reaching an unsafe temperature if ran at 100% duty.

    In reality these aren't that 'passively' safe as two faults could easily render them unsafe, such aa the hotend fan could fail which in some systems would lead to the cold end of the heatsink exceeding safe temperatures for what it is mounted in. Likewise my question was relating to the safety of the cartridges. A system maybe safe if the cartridge remained in the heater block, but I was curious if the temperature of the cartridge would exceed max safe temps if it was at 100% duty at 12V and on free air.



  • @DocTrucker said in Considering a 12v to 24v upgrade? DO IT!:

    I was curious if the temperature of the cartridge would exceed max safe temps if it was at 100% duty at 12V and on free air.

    I guess it all depends on what you would consider a 'safe' temperature. You can expect several hundred degrees before the heat dissipation of the bare cartridge equalizes the electrical generated power (ie equilibrium).
    I would suspect well over 500C which is definitively not safe when in contact with everyday substances such as paper/wood/fabric etc. On the other hand, if the cartridge is suspended in mid air, well clear of any combustible material, it will be just fine until the internal heating wire fails.



  • @jens55 I'd concur that 500C would be beyond what I would call safe. I was curious if running in free air would cause them to effectively self destruct, and if that failure would be fail safe like a fuse generally holding together or if the failure would be more catastrophic, causing a potential hazard in itself.

    Anyway I digress from the original posters topic.



  • Fans will fail when overdriven like this, typically rather nosily. You should certainly take care of them with either replacements or a buck converter. If replacing you can go for all 5V fans everywhere and use the inbuilt 5V on the Duet for them 😉

    Heaters are not necessarily a blocker. But you MUST re-calibrate them at the least. Basically you will be getting double the power from them and if you cannot sink the extra heat fast enough the heater will burn out,.

    Most heaters on powerful machines can get too hot, this is why we have thermistors, feedback and failure modes. For a printbed you can start setting things on fire etc, with hotends you can hit the melting point of the heatblock. Properly tuning them and calibrating heat sensors is your defence against this.

    Heatbeds are often relatively easy, you can run most 12V heatbeds off 24V with no issues, Match the PSU to twice the stated 12V current rating, tune and calibrate, and enjoyed the fast warm up.

    Hot-end Cartridges are different, they are rated for a certain power (eg 30W hotend cartridges may fail to sink 60W of heat energy and burn out internally). I'd always recommend fitting a cartridge with the correct voltage rating, I'd also recommend the 50/60W cartridge heaters over the usual 30W units, they are very responsive and allow higher flow rates.



  • @EasyTarget said in Considering a 12v to 24v upgrade? DO IT!:

    Heaters are not necessarily a blocker. But you MUST re-calibrate them at the least. Basically you will be getting double the power from them and if you cannot sink the extra heat fast enough the heater will burn out,.

    Actually they heaters receive double the current, resulting in the power squared given P = I^2 *R. Your point is still very much valid though, even more so.



  • @EasyTarget said in Considering a 12v to 24v upgrade? DO IT!:

    Heaters are not necessarily a blocker. But you MUST re-calibrate them at the least. Basically you will be getting double the power from them and if you cannot sink the extra heat fast enough the heater will burn out,.

    Actually you will get 4 times the power out of them when you double the voltage !



  • @jens55 @Nxt-1 Oops; yep. Thanks for catching that.
    I forgot that in pure resistive DC circuits twice the voltage=twice the current too, Increasing Power by voltage squared. For the PSU you only need to consider the Current part of that (It's usual to spec PSU's to maximum current, not 'power', for exactly the reasons seen in my error..)

    That said; what I said still stands, just more so. A heavy aluminium bed like mine takes 24V despite being sold and marked as a 12V bed. With PCB beds etc you may have more problems.



  • Now, everybody has got it? Doubling the voltage means to send 4 times the rated power through a component. This is clearly irresponsible. Simply DON’T DO THAT.

    Under normal conditions, you can control the temperatures of the heaters with the Duet, as far as possible, it even provides one or more fallback levels. However, a single system, safe in itself, can still fail, and most of our printers have no independent backup control systems to catch a catastrophic fault.

    Think of a thermistor which fails or drops out, which means the Duet can no longer monitor the associated heater - your hot end, rated for 30 watts, can go wild with 120 watts… definitely enough heat to weaken or even to melt the printed parts of the print head. Near the hot end, the deconstructed parts can easily catch fire…

    @EasyTarget Still, the bed heater is laminated to the aluminium, which means the conductive path is isolated by plastic. Due to irregularities, the resistance of the path is not evenly distributed, you risk local hot spots. These can - locally - delaminate from the aluminium, are then no longer cooled and will eventually burn through, wrecking the heater. With four times the rated wattage, you are no longer on the safe side.



  • Well, for me, I am converting to 24v. But ALL my components will be 24v.
    The nozzle heater and fans... the print bed is relayed at 110v.
    Looking forward to getting it done.
    I'm also converting to MGN12 bearings so its pretty much a complete redesign and has been a slow go...

    I also agree what everyone else says here. Don't run 12v equipment with 24v's. Your looking for trouble.



  • Well he did say he got a device to convert 24v to 12v so I would assume he powered the 12v parts from that.

    Maybe not.

    Frederick



  • @dirtybirdnj said in Considering a 12v to 24v upgrade? DO IT!:

    Hello! I recently started having issues where my printer would brown out only when using the heated bed.

    A "brownout" would be an indication that your 12v power supply wasn't able to supply the required current.

    This could happen with a 24v power supply as well.

    Frederick



  • @infiniteloop said in Considering a 12v to 24v upgrade? DO IT!:

    @EasyTarget Still, the bed heater is laminated to the aluminium, which means the conductive path is isolated by plastic. Due to irregularities, the resistance of the path is not evenly distributed, you risk local hot spots. These can - locally - delaminate from the aluminium, are then no longer cooled and will eventually burn through, wrecking the heater. With four times the rated wattage, you are no longer on the safe side.

    Two years in, still going strong. But your point is valid, I shouldn't be so flippant with such advice just because it worked for me. And if mine wasn't a well made unit I might well have had a burn out by now.
    I still, however, consider the PSU to be the biggest fire risk in this printer, and most others.



  • @EasyTarget said in Considering a 12v to 24v upgrade? DO IT!:

    I still, however, consider the PSU to be the biggest fire risk in this printer, and most others.

    Why do you think that?

    The various heaters are a source of much higher temperatures.

    Thanks.

    Frederick


Log in to reply