Connections to Smoothieboard

smoothboard 5xc v1.0b

I have the following connections on the psu from left to right TH TL WP G IN 5V

I have the in connected to pin 2.4 and the g to a gnd pin close to it

where do the other connectors from the psu go please I have looked at the smoothie page but am unsure and don’t want to blow up the board

many thanks in advance

The board is 5V tolerant, so the laser PSU can not blow it up.

What you describe seems correct. If you want to use a TTL pin, wire a smoothie pin to TH, and configure the module accordingly. Otherwise, hard-wire TH to psu 5V, or TL to psu GND, the PSU won’t turn on otherwise. Also make sure you jumper WP and G together, or connect WP and G through your safety sensors.

If you browse the laser cutter guide, there’s a section about user’s build logs, and those go quite in details on the PSU wiring.


Here is an example of the wiring to the LPSU to the Smoothieboard. Credit to @donkjr and his very informative blog on K40’s:

This is also how i have mine wired and it works well(Smoothieboard 4xC. I did have a mosfet fail on me a while back but an easy swap to the other large mosfet right next to it solved that. I also torched a driver on x by moving the gantry a bit too fast so i am also utilizing M3 and M4 drivers instead of the first two but that was a simple config change and done :slight_smile: but I digress…)
This wiring setup means that you still have the potentiometer on the front panel conntected to 5V, IN, and GND to control the max power output and to allow for on the fly adjustments if its too dark, etc. There is some setups that run the in from the boad also but i never trusted them as they can overdrive your laser tube much easier. Better safe than sorry :slight_smile:

1 Like

thanks this is what I have …do I need another connection somewhere

the red and black wires go to a 24v psu
the white goes to TH
the black goes to G
when you say wire TH to psu 5v do you mean to a connection on the smoothie board next to the main power in connections

Using mosfets is NOT the recommended way of doing this. It’s something users of K40 have to do because their PSU can be weird, however for a normal laser PSU like you have, you SHOULD NOT use the mosfets, and should just wire the pins directly as the documentation instructs.

Huh, why do you suggest not using the mosfet in “open drain” ?.
What do you think is different about these supplies than the K40 stock ones?

There is no reason to use a Mosfet. Asking users to do things they don’t need to do is extremely confusing to newcomers.

You can wire smoothie ground to psu ground, smoothie ttl to psu TH/ttl, smoothie pwm to PSU IN/pwm, and it’ll work. Zero reason to go through a mosfet.

The K40s have several different types of PSUs, and for at least one of them, users have only been able to control them through the mosfet ( some of them have very very weird wiring ), but for a normal PSU like he has, there is zero reason to use a mosfet.

We can respectfully agree to disagree … both work …

My experience with 100’s of users using these supplies (K40 vintage and others) suggests:

  • All these laser supplies have optocouplers with the LED cathode connected to the input pin. The best design choice which is independent of interface voltage is simply to ground this pin.
  • Although it works to connect a TTL device, the input to these supplies are not TTL in spite of the documentation.
  • Connecting to the internal connectors of the smoothie is at least as difficult and confusing as connecting to the plugged screw terminal which requires no crimping nor connector restraints. I don’t think most users know what is behind the pin on the board.
  • Using a MOSFET in most K40 implementations is certainly power-wise an overkill but the connection is unused as are the internal TTL connections so I do not see this as a reason to use one or the other.
  • Using an open drain provides isolation as it simply provides a ground and there is no need for a specific pull-up voltage that is seen at the HVPS.
  • I do not like connecting a HVPS to the internals of an expensive control board.
  • I have no proof but I think this kind of connection is less prone to system noise. I say this because I have troubleshot K40 configs that used the internal TTL and we fixed noise problems by going to the open drain configuration. That said the grounding on many of these machines is ugly.
  • Based on my dissection of these supplies, I am unaware of any unique “weirdness” in the K40 supply’s interface vs other HV supplies.
1 Like

You’re still arguing about K40 stuff. That’s not what he has. Zero reason to use the mosfet for his setup, direct wiring to pins works, is simpler, easier to understand, is and what the documentation recommends, meaning it’s what he’ll have the easiest time getting help with.

1 Like

@Arthur_Wolf —- the only other post from @Lawrence_Graham says “on a k40” so you telling @donkjr that @Lawrence_Graham doesn’t have a K40 doesn’t make sense to me. Yes also he’s switched tube and controller, and that’s also within @donkjr’s personal experience and his professional qualification as an EE. Please take seriously @donkjr saying “We can respectfully agree to disagree” here and meet in the middle.

Both inputs posted and respected.
There is always more than one right way …
I’m moving on :slight_smile:

1 Like

I have the shell of a k40 and it now has a 50w psu with a 50w tube the problem I have is with wiring the new cloudray psu to the smoothie …

would anyone be able to mark a picture of a 5xc showing me what to connect to what to make the laser fire …soldering pins to the board is something I can do but working out what pins do what from the smoothie pages is not something I can do

many thanks

It doesn’t matter if it’s a K40 if it’s a K40 with a normal PSU. The reason I’m pointing out it’s not a K40( meaning not one of the problematic K40 psus, if it’s a normal PSU I don’t care what machine it’s in ) is because some K40 have weird PSUs that require weird wirings, and since he doesn’t have that, he should wire things normally.

He’s got a normal PSU, he should do the normal, simple, easy to understand for beginners, easier to get support for since it’s standard, way of wiring things.

You need to follow the instructions at