There has been quite a bit of discussion as to which K40 control panel is “better”. This article will cover each of these panels and their differences.
K40 ANALOG CONTROL PANEL
The standard analog panel is preferred by a good majority of somewhat seasoned K40 laser users and modders. It has no electronics and displays to fail and the analog meter shows you exactly what your tube current draw is.
This configuration also affords easier panel customization and more room for extra displays, switches, etc… Sometimes simpler is better. This is one of those times.
This panel is perfect especially if you plan to upgrade controllers at some point. With the Cohesion3D, for instance, you dial in your max current once and then never touch it again. The controller does the rest.
K40 DIGITAL CONTROL PANEL
The digital control panel looks neat but not only contains additional electronics and circuitry that could fail but the percentage of power displayed is not 0 to 40 watts. it is very very easy to overdrive and damage your tube because you don’t really know what “35%” is.
The “percentage” is based on the maximum possible output of your power supply. 100% power on your machine may be 20mA or 38mA. Without a milliammeter you can not reliably know how you are driving your tube.
100 percent on the digital panel means 100 percent of the total output of the power supply, not 100% of the the laser tube. It is not calibrated to the tube specifications so the digital setting is quite literally a very poor guess.
People who fitted an ammeter have reported 15mA as being anywhere between 30% and 90% on the digital panel. Digital panels alone are a horribly misleading monstrosity when not used with an add-on 0-30mA DC milliammeter.
The big problem is, and we see it hundreds of times a day, is the “what speed and power do i use for etching edge lit acrylic?”. Percentages vary so wildly i firmly believe those values should never be discussed.
The laser community would benefit greatly if we only shared current values (mA) specific to a certain wattage tube and forget about the arbitrary and terribly inaccurate “%”.
You can (and should) add a current meter to this configuration. You can also add a potentiometer and make yours a simple, reliable analog panel and remove the bulky display and keypad.