Jump to content
Ultimaker Community of 3D Printing Experts

Recommended Posts

Hi all,

I have baught an E3D V6 1.75mm bowden verson and managed to get it installed with a modular hot end mount. A had to make a gizmo out of polycarbonate to keep the smaller coupler from popping out of the old wooden extruder, but now all I need to get up and running is the littile 12v fan to be powered from somewhere.

I have spoken to Joshua at E3D and he was kind enough to talk me through setting the firmware to accept the 12v heater cartridge and thermister settings. However he had said that I need to wire the fan in series from where the 19v comes into the UMO (1.5.7) board, together with a resistor to step down the voltage. I went to maplin and got a 90 Ohm resistor, but after checking the calcs again, I got 101.4 Ohm, is this going to be too small?

He also pointed me here:-

http://forum.e3d-online.com/viewtopic.php?f=7&t=2&p=2

After reading many posts on this topic I am still none the wiser and dont know the best place to take the power from, as I don't like the idea of trying to wire a resistor onto the main power terminal of the board. The other thing of course is that the fan needs to be 'always on'

Many thanks in advance.

Ian.

Share this post


Link to post
Share on other sites

I just used a variable voltage converter on the main board cooling fan connection, and set it to 12v. This is on all the time as soon as the machine is turned on. I think I got it from readymaderc or hobbyking.

Share this post


Link to post
Share on other sites

I'd just use the resistor - for a small fan (12V, less than 70 mA or 0.84W) this is no problem, and you don't lose much energy.

If you have a larger fan with more than 1W power rating, then you should either take a fat (1W+) resistor, or use a DC/DC voltage converter.

Example for small fan:

12 V fan, 40 mA (0.5W power rating)

Input voltage: 19.5 V (UMO power supply)

So, you want the resistor to take away 19.5 - 12 = 7.5 V from the fan, at 40 mA.

That means you need a 7.5 V / 40 mA = 187.5 Ohms resistor.

Nearest Preferred E-series value: 180 Ohms.

Resistor's power rating: 7.5 V * 40 mA = 0.3 W (use a 0.5W resistor)

Of course you need to adjust the values for your particular fan.

You can also turn the calculation around and see what happens if you take "any" resistor value:

Same example fan as before:

12 V fan, 40 mA (0.5W power rating)

Let's say the fan were a resistor (approximation), then it's value would be:

12 V / 40 mA = 300 Ohms

Now, we put your 90 Ohms resistor in series to that 300 Ohms fan, which means we have a total resistance of 390 Ohms.

Powering this from the UMO power supply, we get:

19.5 V / 390 Ohms = 50 mA

The fan's portion of this would be:

300 Ohms * 50 mA = 15 V

and the resistor's portion:

90 Ohms * 50 mA = 4.5 V

Now, back to the power ratings:

Fan: 15 V * 50 mA = 0.75 W

Resistor: 4.5 V * 50 mA = 0.225 W (still recommend a 0.5W resistor)

Our example fan should be able to take that overload without any problems, as long as it doesn't exceed any mechanical rpm limits. (Read: You shouldn't overdrive fans that already run at very high speeds above 10k rpm).

/edit:

About wasting energy: In the first example, we had 0.3W power on our resistor. This energy is wasted (turned into heat). But it's not much. If you use a DC/DC converter instead, you get around 85% efficiency, meaning the converter would waste around 0.075W for a 0.5W fan. This is less (meaning more efficient) than using a resistor, but we're talking about very small amounts of energy which can be neglected.

Hence: Prefer the simpler solution. Note that using a DC/DC converter can be simpler than using a resistor, because you just have to hook it up, no calculations whatsoever.

Edited by Guest

Share this post


Link to post
Share on other sites

Hi jonnybischof,

Thank you for your very detailed infomation :c)

THe E3D small fan is rated at 12V 0.15A.

After working through the numbers I worked out that there would be 1.55W going through the resistor, which is rated at 0.6W, would this handle the extra load?

Also as far as I can see, the only way to power the fan is to de-solder the power socket from the UM board and wire the fan in series, does anyone know of a better way to do this?

Many thanks and kind regards.

Ian.

Share this post


Link to post
Share on other sites
Hi jonnybischof,

Thank you for your very detailed infomation :c)

...

Ian.

You're welcome ;)

I can't reproduce your 1.55W, though...

You're using:

19.5 V UMO power supply

12 V, 0.15 A fan

90 Ohms resistor

right?

So, the "equivalent resistor" for your fan is 12V / 0.15 A = 80 Ohms.

Total resistance: 80 + 90 = 170 Ohms

19.5 V / 170 Ohms = 0.115 A effective current.

Resistor's portion:

90 Ohms * 0.115 A = 10.3 V

10.3 V * 0.115 A = 1.19 W

Fan's portion:

80 Ohms * 0.115 A = 9.2 V

a) Your fan is underpowered in this situation. It might suffice to cool the E3D, but it's not an ideal solution

b) 1.2W is definitely too much load for a 0.6W rated resistor. It will get very hot, possibly up to the point where the soldering tin might melt.

Power ratings should never be exceeded, unless you know exactly what you're doing.

The correct resistor for your fan would be:

(19.5 V - 12 V) / 0.15 A = 50 Ohms (nearest E24 value: 51 Ohms)

7.5 V * 0.15 A = 1.125 W --> Next standard power rating: 2 W

So, you should get a 51 Ohms, 2 W resistor (5% or better tolerance).

The resistor will get quite hot still, so as I mentioned before, the resistor solution is not too nice for fans above ~ 70 mA. A power converter (DC/DC) is preferrable here.

-------------------------------

Wiring:

 

...

Also as far as I can see, the only way to power the fan is to de-solder the power socket from the UM board and wire the fan in series, does anyone know of a better way to do this?

Many thanks and kind regards.

Ian.

(It seems to be impossible to quote your first post, this forum is plain awful -.-)

I overread this the first time, but now it struck me that there's a serious error in the instructions Joshua gave you. He told you to wire the fan in series to the power input, but he meant to say that you need to wire the resistor in series to the fan, and put that assembly directly on the UMO power supply input.

So, please do not desolder your power socket!

I made a sketch for the correct wiring:

5a330e477b819_UMOhookingupanalwaysonfan.thumb.png.7cc52d7caa1e97815f042970360ad960.png

I'd recommend you use the marked points for soldering. They are large and well accessible.

5a330e477b819_UMOhookingupanalwaysonfan.thumb.png.7cc52d7caa1e97815f042970360ad960.png

Share this post


Link to post
Share on other sites

Hi jonnybischof,

I have success, well kind of. I took note of your comment about the resistors getting hot and since I already had a 100 ohm 2W resistor, I decided to buy another one and run it in parallel giving 50 ohm as you suggested.

I measured the resistors after soldering and they come out at 50.1 ohm. I have hooked this up as per your diagram and tried it out. I think the small fan may be inaccurately rated or something because I am reading 14.5V across the fan when everything is running. I have also measured the input voltage at the board socket and that gives me 19.44V

The fan is running fine, if a bit noisy and the two resistors are just getting slightly warm but not hot. According to the E3D article, the small fan is rated from 7v - 13.8v so it looks like I am pushing this.

Am I right in my assumption that the fan is the dubious component here? I cannot understand how the voltage can be so high.

Many thanks again for your super detailed information :c)

5a330e495d865_UltimakerAlwaysonfan.thumb.png.dafe056a4bed59b8c86d64597e47bb97.png

5a330e495d865_UltimakerAlwaysonfan.thumb.png.dafe056a4bed59b8c86d64597e47bb97.png

Share this post


Link to post
Share on other sites

You're right about the fan - Calculating the equivalent resistance from the nominal values (12 V, 0.15 A) doesn't give you any precise results.

Well, now that you have the fan running, you can re-calculate the fan's actual equivalent resistance.

We have 19.44 V - 14.5 V = 4.94 V on the resistor. 4.94 V / 50.1 Ohms = 98.6 mA current.

14.5 V / 98.6 mA = 147 Ohms for the fan.

That means the fan actually draws less current than nominal. This is not unusual, simple manufacturing process thingy.

The difference is higher than I'd have anticipated, but then again it's not an expensive, high quality fan...

I don't think it's a problem to run it at 14.5V, other than the fact that it runs noisier this way. The E3D fans aren't exactly quiet, even at 12V.

/edit:

By the way: If you hook up the resistors in parallel, then you divide the power dissipation between them. Two 2W resistors in parallel equal one 4W resistor. You can take two or three resistors with a lower power rating using this trick ;)

Edited by Guest

Share this post


Link to post
Share on other sites

Hi jonnybischof,

I set a 2 hour print running the other night and everything worked great :c)

In the morning the print was done the e3d hot end had delivered the goods, the little fan was still running and nothing went wrong :c)

So thanks to your help I am in business again.

After being quite frustrated with the whole thing a week ago, I've developed a new found interest in electronics, your help with the calculations was great.

So many many thanks and happy printing :cD

Ian.

Share this post


Link to post
Share on other sites

This is an automotive part. The datasheet says 24..30V input voltage -> UMO power supply is 19V (Maybe UMO+ has a different one, don't know...).

So that's out of spec. Output voltage is 13.8V which is also out of spec for a 12V fan.

I would use a normal 24V to 12V DC/DC converter (5-10W) for a single fan, if you want it to run from the UMO power supply.

One of the cheapest methods however is to just use some cheap 12V power supply. For example, an old external harddrive power supply adapter. These have more than enough power for a fan.

Edited by Guest

Share this post


Link to post
Share on other sites

Guys, you could also use the PCB cooling fan circuit with 7812 voltage regulator, just split output to 2 fans and it will work fine. As long as the total current use is no more than 0.6-0.8A you will be fine.

Edited by Guest

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Our picks

    • Architect Design Contest | People
      The goal of this contest is to design a set of people figurines that could be used in such a project to make an area, office or mall seem populated. 
      Think of different types of people in different environments, like walking people, people standing still, working people, and both men and women.
       
      • 31 replies
    • Taking Advantage of DfAM
      This is a statement that’s often made about AM/3DP. I'll focus on the way DfAM can take advantage of some of the unique capabilities that AM and 3DP have to offer. I personally think that the use of AM/3DP for light-weighting is one of it’s most exciting possibilities and one that could play a key part in the sustainability of design and manufacturing in the future.
        • Like
      • 3 replies
×

Important Information

Welcome to the Ultimaker Community of 3D printing experts. Visit the following links to read more about our Terms of Use or our Privacy Policy. Thank you!