UM2 power switch specifications for remote position

[rotorhead 1]

I'd like to move the UM2 power switch from the rear to the front. I already have a Pi running on the printer which has 2 status LEDs and a reset momentary switch and so it would be really nice to have all the controls in the same place. From looking at the original switch on the mainboard, it does not 'seem' to be very significant which makes me wonder if it is actually switching the full 24V 9A power supply or if it runs through a transistor or something?

Has anyone done this before?

Does anyone know what specs I need for an additional switch on the front. Does it really have to be able to handle 24V 9.2A?

I guess I could just move the existing switch but getting all those tabs off the board without doing any damage does not fill me with excitement! Also, it wouldn't look that great on the front.

 

Thanks

[tinkergnome 927]

11 hours ago, rotorhead said:

From looking at the original switch on the mainboard, it does not 'seem' to be very significant which makes me wonder if it is actually switching the full 24V 9A power supply or if it runs through a transistor or something?

 

Well, there's an additional relay on the mainboard that switches the 24V loads (AFAIK) - this may be a clue. But this is not my field of expertise.

The schematics are published:

https://github.com/Ultimaker/Ultimaker2/tree/master/1091_Main_board_v2.1.1_(x1)

 

[Torgeir 242]

Hi rotorhead,

 

Sure this is possible, but leave the original switch in place as it is meant to be used for PCB mounting.

Also you don't need a switch that's need to cope with 9.4 Amps, you'll just need a switch that can do 2 Amps!

This as the original switch on the PCB only direct power to the DC-DC converter (24 VDC-5 VDC), so this is the power used for the processing part of the board.

The power consuming parts is delivered by the power relay mounted on the board, delivering power to heat bed, heat block and all stepper motors + logic in here.

Find a switch that match (your style) and make sure to select one with good quality!---

You just need a single pole switch that's connected in parallel with the original power switch (that's to be in selected off position), then you only use your remote located as power switch.

I've made a copy from the UM2 (where the power switch is involved) for you to see how it can be done.

 

 

 

This picture shows where to connect the "remote" switch in the wiring.

 

 

This picture show the location of power switch and used pins (1 and 2) looking into the pcb when still installed in the printer.

So no need to do to much here, but need some skill to solder this correct.

 

Hope this will do.

Good luck.

Torgeir

 

[rotorhead 1]

Perfect, they were exactly my suspicions but the confirmation is ideal.

Thanks for getting that information for me.

 

Thank-you both

[rotorhead 1]

This worked perfectly using a £1 switch from CPC. I have actually used a DPST switch and so will double it up to also switch the power to my OctoPi (taking the supply from the main 24v input). It's also now in series with a relay controlled by the Pi so I can have some temperature driven failsafes.

I'll post a pic when it's done

[Torgeir 242]

Hi rotorhead,

 

Way to go!

Thanks for the update.

 

Regards

Torgeir

[rotorhead 1]

I'm trying to work out how the power switch actually works. I've had a look at the circuit diagrams but I don't know enough about what I'm looking at to answer the question. Does it control a relay/transistor which then switches the power to everything else?

I'm asking because I'm trying to work out what components could potentially fail and therefore where the emergency power-off relay should go.

[tinkergnome 927]

 

45 minutes ago, rotorhead said:

I'm trying to work out what components could potentially fail and therefore where the emergency power-off relay should go.

 

Well... a power supply can fail as well (and catch fire). The really big capacitors are in the power supply. If you don't cut the mains voltage in an emergency case, it will always be only half of the solution.

(just my 2ct.)

 

[rotorhead 1]

7 hours ago, tinkergnome said:

 

 

Well... a power supply can fail as well (and catch fire). The really big capacitors are in the power supply. If you don't cut the mains voltage in an emergency case, it will always be only half of the solution.

(just my 2ct.)

 

That's a very good point although I think that adding temperature probes to monitor the power brick as well as the heating elements, print head and enclosure might be beyond the scope of this project - for now!

 

Maybe my project does need to be more complicated to be worth the effort but I was just trying to increase the protection to a reasonable level from a reasonable amount of work. I presume that the firmware has some heating protection built-in and I also assume that the main board has been designed to minimise the extremity of a failure but I don't know enough about it all and can't find the info online.

 

My thought was to just remove an additional potential problem. If the main switch is switching a mosfet and this fails at the same time as something in the heated bed then potentially my kill relay would not stop the thing indefinitely heating itself up and catching fire? Or maybe this isn't possible?

[Torgeir 242]

Hi rotorhead,

 

 

You're right there is a built in max hi temp protection and temp sensor failure protection.

This protection is made for the extruder and heat bed.

This is the highest level of error in an UM2 that will cut the power -so all heaters and steppers will loose power!

On this PCB there is also two safety switches input, that might be used for over temperature issues etc.

Normally those two connectors are shorted by a link. If one of those two open K1 also open.

A max temp switch/sensor might be used in here..

 

For the separate power supply itself, you might install it in a vented metal box. However, those power supplies normally have several protection "fuses" built in.

 

For the main power, I'm using an extension cord with several connectors in a row plus a main switch. After turning off the printer I'll then switch off the main switch that's kill the power to the printer power supply.

 

I'm not sure about the max temp for the UM2 extruder but I'll think it was 265 deg. C.

 

I'm sure @tinkergnome now those temperature limits. 😉

 

 

Thanks

Regards

Torgeir

Edited April 22, 2021 by Torgeir
Error corrected.