Ulitmaker 2 part fans not working

[ctsniper86 0]

I noticed that the part fans on my ultimaker 2 had stopped working the other day and found a broken wire between them, after replacing the wire they still don't work.

I tried switching them both out with new replacement fans with no luck.

I have since noticed that the heated bed isn't heating anymore.

I have access to the board atm but don't know what I am looking for or how to test anything.

 

Any info I've missed I can find.

Any advice on how to proceed from here

Thanks

[gr5 2,067]

Do you know how to read schematics?  The schematics for the UM2 are here:

https://github.com/Ultimaker/Ultimaker2/blob/master/1091_Main_board_v2.1.1_(x1)/Main Board V2.1.1.pdf

 

The 2 cooling fans are 12V fans with 24V across them but the fans are in series so it usually works where each fan gets half the voltage.  But some brands of 12V fan will not work that way - they do not like being put in series.

 

1) Are the stepper motors also broken?  If the relay, K1 is broken (it broke on my UM2) then everything will look fine except 3 things won't work (no 24v reaching them):  steppers, heaters, side fans.  Everything else will seem okay (ability to read temperatures and use the menu system and so on).  Hopefully this is the case as this is super easy to fix.

 

2) You can turn on the side fans manually with the menu system (if I remember right) on the printer (if not you can certainly do it with the "tinkerGnome" version of the UM2 firmware.

 

[ctsniper86 0]

I realized that I had got 5v replacement fans rather that 12v. So I got two new 12v fans but I still can't get them to function on the fan pwm plug. I have tried them on the other fan plug (which also shows 24v) they don't work when I connect them in series no matter how. However when I connect just one it works just at what I assume to be faster speed than normal.

[ctsniper86 0]

They work when I connect them in parallel to the other fan plug but not to the fan pwm plug. I assume that the pwm controller part must be blown.

My plan is to run them from the other fan plug and put a manual switch in the connection to allow me to turn the part fans on and off manually.

 

Do I need to use a 240v switch or will a 12v work? Could I use a 12v LED dimmer switch or a regular light dimmer to give me control over the fan speed?

 

Thanks

[gr5 2,067]

Lol.  I put 24V across a 12V fan once.  It died in about 1/4 second.  A bit of smoke came out.  It never worked after that.  You are lucky that your fans have built in protection for that.  I see that kind of thing more often - parts that can be abused quite a bit and are just fine.

 

Switches:

Most switches have a max amperage and max voltage rating.  If you go over the max voltage the risk is that a spark can arc across the gap.  So a switch rated for 240V is fine for lower voltages.  However you have to check the amperage also.  Most 240V appliances will use less than 20 amps (probably less than 1 amp).  So switches are rated for something like 10A or 20A.  Those fans have a heavy inductive load and can draw quite a bit of current for their size but any switch rated for 1 amp is probably fine.  Still it's smart to add a fly-back diode around any switch.

 

A 12V LED dimmer will probably work but it definitely definitely needs a fly-back diode.  These are not needed for LEDs but are needed for any kind of motor (like a fan).  There should be a way to find out if the dimmer has a fly-back built in.  It might say "appropriate for motors" or "okay for inductive loads" or "safety diode" or "fly-back diode".  Without this fly-back diode the voltage across the switch (the on/off switch inside the dimmer) can build up to thousands of volts (but only for a few milliseconds - long enough to destroy the semiconductor transistor inside the dimmer).

 

In fact this inductive load issue is probably what broke the current circuitry inside the printer.  If you are curious, google about inductive loads and fly-back diodes.

 

Or you could buy a diode.  It needs to be able to handle 24V reverse voltage (not a difficult spec at all).  

[ctsniper86 0]

Would a zener diode work? 

[gr5 2,067]

No.  Not unless it is set way above 24V.  Typically Zeners allow current the other direction when the voltage is above say 3V or 7V.  30V zener would be rare.  You have to place it directly across the two fan wires.  If you put a normal diode one way it will conduct all power and burn out in a second.  If you put it in the flyback mode it only conducts current if the power goes negative (which it will when you stop powering the fan - the fan will keep moving the current and the voltage will go negative to quite a high voltage and blow up the circuitry inside the printer or in your case cause a spark across the switch or even a spark somewhere inside the fan - the diode protects all this from happening allowing the current from the fan to dissipate harmlessly back through the fan motor again until air friction uses up that power).  Anyway when you put the zener across the fan wires and the first time you put 24V across it, if it's say a 7V zener - it will let all the power through and blow up the zener immediately.