Need help for PWM Led and IRF520

General Discussion
21

Hi, i just tried to connect my part fans to the MOSFET, i have 3.1v at the fan connection, and it doesn’t turns.
I should receive MOSFET proposed by @Sineos this week, i’ll try

Another idea: if the MOSFET and led strip acts as a voltage divider, what if I add a resistor in parallel to the led strip ?
Thanks

22

You have 3.1V across the LED strip when using the fan output on the MKS Robin Nano V1.3 controller board?

Something seems seriously wrong here - what’s your power supply output? What is the voltage rating on the fan that was on there before and how did it work?

If you add a resistor in parallel to the LED strip, then you’ll reduce the resistance of the load and lower the voltage across it.

Could you draw what you are doing and measuring as well as post some photographs? I’d like to understand exactly what’s happening here.

23

No, i have 3.1v across the fan wire when powering it with the IRF520. (I’m pretty sure the LED strip will work if plugged to the HE1 output of the Mks board, so i prefer to test powering the fan with the IRF520 first)

You can find a photo here : https://photos.app.goo.gl/7fvqgyZttKbyvA5H8

If i plug the Led strip to 24V PWM output (and PA5 output is equal 1) i have 19v at this output
If i plug the part fans (two 12v fans in serie) to 24V PWM output (and PA5 output is equal 1) i have 3.1V at this output

I also try this kind of level converter : https://www.amazon.fr/SparkFun-Logic-Level-Converter-Bi-Directional/dp/B00M7U5DV2
wired as following :

  • GND to Mks GND
  • HV to Mks 5V
  • LV to Mks 3.3V
  • GND to IRF520 GND
  • LV1 to Mks PA5 output
  • HV1 to IRF520 SIG
    It doesn’t works : if PA5 output is at 100%, i have 5v to HV1 if not connected to IRF520, but i have 2.75V if connected to IRF520 (so IRF520 output is about 18v)
24

Do you mind if I go through this line by line? I think I know what you’re saying but I need to confirm it.

What is the “fan wire”? I think you’re saying is that you want to see the fan working first with the IRF520 board before plugging in the LED strip.

I was hoping that you would plug the LED strip into one of the board heater/fan outputs to see how it works and measure the voltage across it. Once we saw the results from that, we’d decide where to go next.

The goal is to have the printer working as efficiently as before but with the added bonus of an LED strip.

This looks like what we were talking about earlier in the week - PA5 is being passed to the input of the PCB.

A couple of comments here:

  1. You can copy and paste images into your post, it makes it a bit easier to follow what’s going on rather than havining to jump between broswer tabs.
  2. I ask for a drawn circuit and a photograph for three reasons. The first is that it makes it easier for me to scan what you’re doing, both conceptually as well as how you’ve physically wired it. The second is to minimize the chance that we will be talking about different things. The final reason is for you - so that you think through what you are doing and can see it visually before you attempt to wire it.

A pencil drawing that’s photographed with your camera and then posted herre is more than good enough.

Again, a drawing and a photograph would be helpful here. I’m not sure what “at this output” means.

No, that won’t work.

Sorry, I guess that’s on me as I didn’t properly explain what I meant by level converter. The Spark-Fun Bi-Directional level converter board is for signals that do not have any loads on them - the IRF520 has an LED and some resistors which will result in lower voltages at the input of the IRF520, just as you are seeing.

I just did a review of the “Level Shifter” products on Spark-Fun and the (only) one that you should be using is:

That is basically what is on most 3D printer controller boards to bring the 3.3V logic to 5V - you need the active output to be able to drive enough current to the IRF520 board to drive the LED without a significant (if any) voltage drop.

I’m still curious to find out what happens if you wire the LED strip to one of the fan/heater outputs on your board. From there, we can figure out what is the best way of getting things working.

25

Ok, sorry, is that better ?

image
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On the left image, i measure 19v between V- and V+.
On the right one, i measure 3.1v between V- and V+

I’ll try the led strip connected to HE1 soon
Thanks again for your patience !

26

This is no good idea.

grafik
grafik948×1094 57 KB

You can put resistors, incandescent bulbs, LEDs or other passive components in series, but no such things like fans that work with active parts inside.

27

Part fans are wired this way on ultimaker 2, not my choice

28

That makes me :face_with_raised_eyebrow:

29

What is the reason ?
Not sure each fan has exactly 12v ?

30

For they are active components, the power consumption can vary - a bit more, a bit less. For a fan, a bearing can get sticky, so the the fan needs more power, the inner resistance goes down and the 50/50 balance between the fans is not given any more.

31

It’s better and explains what you’re doing along with what you’re seeing.

As @EddyMI3D noted, modern fans have electronics inside them, they’re not just DC motors. Applying 12V in this way really shouldn’t work.

Could you provide a photograph of the fans (I’m looking for any labels on them) as well as how they were wired in the printer?

32

Here is a photo :

image
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The ref is df0301012bm-501
And it can be found here : Model Cooling Fan 12VDC 0.1 A - 3DVerkstan
I’m sure they were originaly wired in serie

33

That’s helpful - thank you.

Could you put the fans back into the printer and report both whether or not they are wired in series and what is the voltage across them?

I found this thread here:

That discusses the fans. I’m wondering if there is a 12V voltage regulator for the fans.

Could you look at the voltage coming out of the fan connector?

34

I’m absolutely certain it’s 24v since I had to verify every wiring when converting the printer to klipper by replacing motherboard.

Here is an explanation: UM2 hotend side fans rating - Third party products & modifications - UltiMaker Community of 3D Printing Experts

35

Thank you for the link. That helps explain things with a bit of research.

Let’s recap:

  1. The Ultimaker 2 toolhead has two 3010 top level cooling fans which are rated at 12V and are wired in series to work with 24V.
  2. When you attach a 24V LED strip to an IRF520 board that is controlled by PA5 lights dimly. When you looked at the voltage across the LED strip it was 19V. This matches with my expectations and what I see with my LED strip/bench supply.
  3. You tried the Spark-Fun bi-directional level shifter and the voltage with the IRF520 and LED strip fell to 2.75V.
  4. You moved the (two series) fan connection to the IRF520 board and found they do not run and have 3.1V across them.

Is this correct?

As far as I can tell, you still haven’t tried connecting the LED strip to one of the fan output on the Robin Nano V1.3 to see if they work properly with this driver. Could you do that and measure the voltage across the LED (regardless whether or not it is working)? Before we go any further I want to verify if my theory matches practice.

Next, reconnect the two fans in series to the fan output on the Robin Nano V1.3 to ensure they still work properly?

How do you feel about wiring your own driver board for the LED strip? From what I can see, you’re reasonably handy with electronics. I would build my own and demonstrate it before I guide you through the process. I think all that’s required is a 2N2222 Bipolar transistor and a 220 Ohm resistor (but this is off the top of my head so this isn’t set in stone).

36

Hi, i have tried to connect the led to the fan output, it’s a bit brighter but not at maximum brightness. When PWM is 100%, there is 22V across the led.

But i have received the dual mosfet proposed by @Sineos
It works perfectly, brightness is maximum when PWM is 100%, i have 24V across the Led strip
The Mosfet doesn’t seems to be hot at all after 10 minutes at max brightness

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Thanks you very much !

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37

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