Cohesion3D PWM Control and Potentiometer vs 'Digital Panel'


#1

We get asked about these things a lot:

  • Does the Cohesion3D control the laser power? (Yes it does, just throwing it out there)
  • Well then why do I still need the potentiometer that came with my machine?
  • I have the oh-so-fancy digital panel instead of the potentiometer, is the Cohesion3D compatible with that?
  • Seriously, why can’t I just get rid of the digital panel and let the board run the laser power entirely?

These are a small subset of the types of questions we get asked and answer on a regular basis.

So here goes:

Intro

Yes, the Cohesion3D boards (both Mini and LaserBoard) have a PWM output so that they can control the laser power from the software. So you can have true grayscale engraving, cut at multiple power levels, and do it all in one job without having to run one section at a time, come back, tweak the pot, run the next section, and so on.

In a typical installation you don’t have to do anything different or extra to enable this, there’s a wire called L (Laser Fire) in the large power plug that went to the stock board, and you’re going to unplug that from your stock board and into your C3D as part of the swap. That’s it.

Hard Limits

We still want something to set a hard limit on your laser power. It’s bad for the laser tube life to run it at full power, so we want to limit it to 75-80% of its maximum, at most. So we want the pot/ panel to set the max power.

Also, you’re not going to get good grayscale results (particularly with raster engraving of images) if you just “set the pot/ panel to max” - which is the same outcome as if you removed it entirely - by lowering the pot/ panel value the C3D board can control power within that smaller range, meaning better resolution.

A number of customers have written that they set the pot once to a “safe” max value such as 15mA and leave that alone - that way the board can freely work in its full pwm range from 1-100% but your tube is safe.
I personally set the pot to what is the highest power needed for a particular job - that might be only a few mA to engrave only or 12mA to cut through some plastic. In this example, if I want to engrave and then cut, I would set to 12mA.

Pot vs Digital Panel

You really want a potentiometer. This is a time where analog is actually better - a good potentiometer will allow you to get higher quality grayscale, and the digital panel K40 models don’t have an mA meter so you’re firing in the blind without ever knowing what power your tube is getting.

TL; DR

In short: the digital panel is common but sucks because you don’t actually know what power you’re firing your tube at. You really want an mA meter. You can keep the digital panel and install an mA meter, or you can replace the digital panel with a potentiometer. Making this upgrade kit for the digital panel is on my list to do, will take a while though. And reading my response to you, this is complicated stuff. Much more than it needs to be.

Example (because everyone loves pictures)

It is possible to do all this in a single job by just setting the pot to the maximum power value for the job as discussed above:


Variable Laser Power (pwm)?
Wiring up board (had digital display)
LSPU wiring
X and y axis moving but laser not firing
Engraving Annodized Aluminum
Fslaser 5th gen conversion
C3D - Laser tube always on