M2Nano 5V current load & board info

After working with users that changed their LPS and had problems with the M2Nano’s USB connection I wanted to know:

  • How much current does the M2Nano draw??

This is important in that some LPS’s 5V are very limited in capacity (20ma) and my not be able to be used to power a M2Nano.

I dont like to just guess on things like this.

Not being able to get a direct answer from any source of M2Nano specs it occurred to me there may be an indirect way to estimate the M2Nano max current draw.

That is, by considering the stock configuration of a K40. In a stock K40 the LPS’s 5V output drives the Nano and I know something about the internals of K40 LPS.

You can see from the schematic below that the stock LPS provides 5V power from a 7805

From the TI LM7805 data sheet:

I found output current specs on LM7805 devices ranging from 1 - 1.5 amps depending on the vendor.

I physically checked one of my test LPS. It had a 7805H installed


  • It seems reasonable to estimate that the current draw of the M2Nano to be less than 1.5A
  • A 2A @ 5V supply seems like a safe design point and should have enough capacity to power a M2Nano.

An incidental finding while looking for M2 Nano specs for 5V power supply load.

I do not recall seeing this info posted anywhere.



The Wiki page is a nice find! Looks like more people are reverse engineering the M2nano.

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I pulled out my old M2Nano and installed K40 Whisperer v0.58 src and tested using my bench power supply. I put just 5V on it and got no USB device, I tried just the USB cable and got no USB device. When I connected only 24V I got /dev/ttyUSB1 and k40 whisperer connects to it.

I see only 0.05A being drawn on the 24V supply. Again, nothing connected( no 1K POT, no end stops, no motors. ).

It’s from 2017… new versions might power up differently.
says firmware version: 2017-05-25
says Model 6C6879-LASER-M2:9

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It felt to me that the M2NANO engineering team just discovered OPEN engineering.

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That implies that the USB controller’s power is derived from the 24V and the 5V input on the M2Nano is not related to the USB connection?? Why does the Nano need the 5V then?

Let me power it back up and see if the 5V output is there with only 24V connected… I see 5V on LO of the power connector and I do not see 5V on the nc pin of the end stop connector(end pin opposite(gnd/Y-endstop/X-endstop/gnd/NC). pinout on google says there should be 5V on that NC pin.

I do not know why that 5V input is there. With just 24V connected the USB connection works and the board is recognized by K40 Whisperer v0.58 and i saw 4.8x volts on the 2 end stop pins so I don’t know why 5V input is there. I also saw 5.0V on the L0 pin of the power supply indicating Laser Off.

what 5V output is that?

I just rung out the 5V pin to the internals and it connects to almost every chip on the board.
Most importantly it connects to pin 28 of the CH341A.
That makes me very confident that the M2NANO needs the 5V for proper operation.

Confusing: the ohmmeter shows no connection from any pin on the USB and the NANO’s 5V.

So its connecting with only 24V on the board I suspect the USB connection is what is powering the NANO logic??? But then the USB only cable should have worked?

The USB connection is powering the board but the firmware is setup such that communications will not connect unless the 24V is good.


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I can see there being no USB-5V connection to the board and the onboard power being the only thing powering the USB chip and controller because otherwise you’d need diodes to deal with variations in voltage between onboard and USB supplied 5V but most importantly, you could connect the USB cable and think everything was working even with no 24V. I’ve seen it with the Orturs as people power up and connect to the Ortur and forget to turn on the laser power switch but LightBurn thinks everything is OK with just a USB cable powering the controller.

The 78L05 on the very right is a 5 V voltage regulator. Max output is 100 mA.

Seems like at least some of the 5 V stuff is powered via the 24 V rail.

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With the “DRV” flavor (external steppers), that pin isn’t connected:

The description for that pin:


NC: Not used, that is, not wired;

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M2Nano V7 PDF:

供电要求(5V 实测<40mA,以下 100mA 是备用余量)

  1. 5V(4.75V - 5.25V):大于 0.10A = 100mA
  2. 24V(23.5V - 28.0V):最小 1.2A,最好大于 1.8A
  3. 5V、24V、激光电源,这三者要共地

Power supply requirements (5V measured <40mA, the following 100mA is the reserve margin)

  1. 5V (4.75V - 5.25V): > 0.10A = 100mA
  2. 24V(23.5V - 28.0V): min. 1.2A, better than 1.8A
  3. 5V, 24V, laser power, these three should be common ground

If I read that right, the measured consumption was less than 40 mA, but they recommend to use a PSU which is rated for at least 100 mA.

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Can you post the PDF?

M2 Nano V7:




Those links do not resolve for me?

It’s strange that the board could draw only 100ma when the CH341 itself draws 30 ma.

Here is the link to the manual that I translated through Google.

Thanks forgot about this doc…

The host name can’t be resolved? Or do you get some error message from the server?

Pasting the link in a different browser worked just fine for me.

Try pasting it into a new incognito window.

Got the links to work, thanks.
The version of the M2 nano in these documents is different than those in K40 in that the 5V pin is NC.