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I have a brain fart of an idea on how go use a 24v psu with a ultimaker. I though that using the full 24v for a heated bed then using a dc to dc converter to get to the 19v for the rest of the electronics. Anyone see any issues with this idea? I have found a few 150w dc to dc converters on eBay so seems it will have enough juice.

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So it comes back to cooling of the UM board. Although it has a powerful radial fan, the fan duct is quite - uhm - suboptimal...

Just for completing the picture: The other way round (12V instead of 19V) shouldn't be a problem? As I will (hopefully soon) implement my heated bed with a 12V additional PS, it might become a topic for me to reduce to one PS.

 

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I wouldn't need extra cooling as there will still only be 19v going to the board. The dropper would be an external device bolted to the bottom. If you can see where I am coming from. From my readings the UM uses 70-80w at 19v so a 150w dc to dc would do fine.

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Using a DC/DC converter like you describe would work fine.

But it's probably more intelligent to actually supply the UM electronics with 24V and deal with the consequences:

- The hotend will be supplied with 24V instead of 19V. That will make it heat up more quickly. It shouldn't have any problem with that because it's actually made for 24V if I'm not mistaken (I doubt that 19V heater cartridges even exist). But maybe the temperature control (PID settings) will need to be adjusted a little in order to handle the new circumstances. I don't know - never tried it. Again, that's no big deal, you can change the PID settings by making a custom firmware (e.g. with the marlinbuilder forn robotfuzz).

- You'll need to replace the 7812 linear regulator, ideally replace it with a DC/DC switching regulator. You won't need a 150W switcher because you don't need to convert the main power hungry part of the UM anymore (the hotend). I suppose a 50W regulator will still have a lot of headroom because the 7812 could never sink that much power. I guess there's only the fans and the electronics board left that run from 12V.

I'm not sure about the steppers, but I sure hope they're supplied from 19V and not 12V.

I think that's actually everything.. Afaik some people here in the forum have already done this mod.

 

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I am planning to do the exact same thing with my machine so also curious if nobody has input to why it wouldn't work...

Seems like people are generally misinterpreting your intentions though...

The way I understand you (and the same way I was planning to do it) is like this:

- Buy a 24V PSU large enough to handle both printer and HB (I think 150W might be too small, I got a 350W myself)

- Connect the HB directly to this PSU through a relay controlled by the HB outputs on the UM board

- Connect the UM board to the PSU through a DC to DC converter that regulates down to 19V

So HB gets 24, UM board 19 and you don't need to change anything on the board itself

 

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Yeah, I'll admit I read the thread a bit hastily. I just assumed that he wanted to use the higher voltage for the board as well as using the same voltage isn't much of a change :)

I was also unclear about the 7812 not being able to handle 24V, I should've clarified that I meant without additional heatsinking.

I need to stop bouncing between tabs and reading different things while replying to topics :p

 

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Yeah, I'll admit I read the thread a bit hastily. I just assumed that he wanted to use the higher voltage for the board as well as using the same voltage isn't much of a change :)

I was also unclear about the 7812 not being able to handle 24V, I should've clarified that I meant without additional heatsinking.

I need to stop bouncing between tabs and reading different things while replying to topics :p

 

Haha guilty of that too sometimes. :D

 

I am planning to do the exact same thing with my machine so also curious if nobody has input to why it wouldn't work...

Seems like people are generally misinterpreting your intentions though...

The way I understand you (and the same way I was planning to do it) is like this:

- Buy a 24V PSU large enough to handle both printer and HB (I think 150W might be too small, I got a 350W myself)

- Connect the HB directly to this PSU through a relay controlled by the HB outputs on the UM board

- Connect the UM board to the PSU through a DC to DC converter that regulates down to 19V

So HB gets 24, UM board 19 and you don't need to change anything on the board itself

 

Exactly the way I was thinking but without the relay. I was going to unsolder the Mosfet, take a wire from the gate pin to the mosfet thats on a external board that then allows you to use the 24V with the loveliness of PWM! Also gets rid of that ticking from a relay!

 

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Haha guilty of that too sometimes. :D

Exactly the way I was thinking but without the relay. I was going to unsolder the Mosfet, take a wire from the gate pin to the mosfet thats on a external board that then allows you to use the 24V with the loveliness of PWM! Also gets rid of that ticking from a relay!

 

I bought myself a DC-DC Solid State Relay which should be able to switch on-off every 10 ms. or so... So no ticking... and I guess at those switching speeds PWM is still an option?

 

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I bought myself a DC-DC Solid State Relay which should be able to switch on-off every 10 ms. or so... So no ticking... and I guess at those switching speeds PWM is still an option?

 

I bought myself a DC-DC Solid State Relay which should be able to switch on-off every 10 ms. or so... So no ticking... and I guess at those switching speeds PWM is still an option?

 

My understanding of pwm is that it is pulses of 10s of thousands per second. Varying the number per second to create a output of a certain value. Meaning that your 10ms May be too slow for true pwm. Could be totally wrong though. :D

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The heated bed typically is in "bang bang" mode meaning it turns on when temp is low and off when too high. Like my house thermostat. In PID mode the bed switches on and off I believe only about 10 times per second.

But ginge Marlin builder defaults to bang bang mode I think. It works just fine:

http://marlinbuilder.robotfuzz.com/

 

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Should work just fine, it's even tested for that application according to the seller.

Looking at it, I might acutally get some of those myself :)

Generally (if you were looking at another converter), you just have to watch out that you have enough "Dropout" voltage:

Buck converters usually need to convert from a higher input voltage to a lower output voltage, and there's a minimum voltage drop, which would be something between 1 to 3 V. Always depends on the converter.

In our case we have 24V - 19V = 5V drop.

So you need to look for a converter that can operate with a voltage drop of 5V or less.

If that information is not given, look for another product... You could probably not do 22V output at 24V input. Depends on the module.

 

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Generally (if you were looking at another converter), you just have to watch out that you have enough "Dropout" voltage

You also have to watch out for what max current its rated at...

This one says 12A which should be more than enough for driving the UM.

It also says to add a heatsink if consuming more than 100W, I believe I saw somewhere else people estimating the UM to draw around 75W max, so it should be fine even without a heatsink..

I got two different ones, but very similar to it...

 

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I made some measurements on the primary side of the UM PSU. I used a device which was found to be very accurate in a independent test (Brennenstuhl PM231). And it said that while printing, the primary consumption is around 160W and the power factor 0.86. Further measurements showed that the 75W might be the power needed when not heating the hotend. I also have to mention that my UM1 has a dual extruder. Maybe you know that the idle extruder motor is always enabled as well (something I intend to bring up in the Marlin developer group sometime soon).

 

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Dual extruder means dual hotends which are by far the component gulping up the most watts on the UM, isnt the standard heater cartridge 60W?

 

Only one hotend was actually heated during the measurement.

 

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