80-watt generic PSU connection on board cohesion 3D mini

Machine: Custom in construction

Board: Cohesion 3D mini

Firmware: Smoothie

Problem/ Question: Hello everyone, I’m building a new 80-watt laser with a 3D mini cohesion board and a generic 80 watt (HY-T80) power supply. Now I have doubts about the connections. Wanting to mount an analog power meter , then having G/IN/5V occupied by the power meter. G and WP are ponticellated, remains free TL but I have the doubt if it should be connected to FET1 bed - or if it should be connected GND and L of the 4-pin connector normally used with the K40. Thank you so much for your help. I attach design to understand which is the most suitable solution.

The 4 pin power plug with L and Gnd is all that is needed. The terminal 4 FET Bed - is electrically the same connection as L, and terminal 2 is Ground. You can use these screw terminals because I figured most people would not want to make a custom connector with crimping to put it on the weird power plug that the M2Nano has.

Perfect , thank you so much.
Now I have to proceed to the connection and hope it doesn’t explode the house… :ghignante::ghignante:
Thank you again

Excuse me again, one last piece of information, the laser test button I connect between GND and L correct?
Thank you again

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That doesn’t seem like the right place for a test fire switch. The K40 style LPSU has K+ and K- dedicated for test fire switch. This HY-T style PSU appears not to.

The question is: “All the mosfet is doing is connecting TL to Ground when on and when off it’s not connected. So if you close the switch on those 2 lines while the mosfet is not connected, no short is being formed, right?” But I’m not completely sure of this.

And Jim said, " I was always told not to short the drain to source but never really looked into why."

So I’m not entirely sure yet.

So if I get it right there’s no way i can have a fire test button.
Is it the only way to use the TEST key on the PSU?

Ray do you think he could put his test switch between 5V and the unused TH pin on the laser PSU?

This sounds interesting, I hope it works as well as it sounds!

I had a look at the hand drawn schematic, and closing the switch does ground TL to G. To me that should work. I can not see it causing an issue if it is wired that way.

That part is fine, but it would also be “shorting” the opto on the board that does the same thing when that opto was not also firing the laser. The question is whether it is harmful to short the collector to emitter of a transistor when the transistor is off.

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I asked an EE friend of mine, and he said that the circuit will be fine, it is just bypassing the FET when pressed. Shorting the emitter to the collector just causes current to flow, but will not harm the FET in any way.

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