Digital Control Panel and Tube Current

(Ned Hill) #1

So the HVT on my LPS went and did a zombie on me. Since I needed to replace my LPS I decided it was time to do a bunch of upgrades I’ve been sitting on. In addition to the LPS I also replace the tube (2.5yrs original). Also wanted to get rid of the digital control panel and go to a potentiometer and ammeter so I can see how much current I’m actually running. @donkjr was big help in getting me going on this upgrade.

To make the transition I did a series of measurements . With the new tube and LPS I first measured the voltage between the G and In pins on the LPS as a function of % on the digital control panel. I next hooked up my multimeter into the cathode wire of the tube to measure tube current as a function of power %. The a table of values and a chart are shown below. My new tube is rated at a maximum of 16ma which gave 38W when the tube was measured just prior to shipment. As you can see from the chart, I reach the maximum current at about 55% on the digital control panel. When you operate above the maximum rated current the power output (watts) quickly plateaus off and it shortens the life of the tube. So if you are just using a digital control panel please keep in mind that there is no real value in operating the tube much above 50%.Tube%20power%20percent%20plot Tube%20power%20percent%20table

Ned's control data drove me to distraction
K-40 Panel
How high can you go?
(Anthony Bolgar) #2

Actually, there have been cases I have seen where 30% on the digital panel was 16mA, and as high as 90% on the panel being 16mA. The only safe way to know is to add a mA meter to your machine if you have a digital panel.

(Ned Hill) #3

That’s crazy, but not really surprising with these machines. Which is also why I wanted to add an ammeter. For anyone interested @donkjr has a blog post on adding an ammeter.

(Ned Hill) #4

@donkjr also has a blog post on his work on examining how the digital panel works and the drawbacks.

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(0.45 NACL) #5

Where did you end up getting your tube and power supply?

(Ned Hill) #6

The tube was from lightobjects https://www.lightobject.com/SPT-35W-CO2-Sealed-Laser-Tube-for-Small-K40-Laser-Engraving-Machine-P208.aspx and is a nice SPT tube.

And the LPS I got from Amazon. This one was actually selected because it was a little lower in price then other ones and I could get it fast with Prime shipping. Bit of a crap shoot, but it seems to be a decent quality.
https://www.amazon.com/gp/product/B07JJ4ZL4G/

(0.45 NACL) #7

I’m curious why you did not buy a matched pair from light objects.

(Ned Hill) #8

The tube I actually bought several months ago and hadn’t installed yet. The LPS that light objects sell are a lot more expensive plus I needed to get my laser back up and running quick to meet a make by date.

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(Anthony Bolgar) #9

I am waiting for a 120W tube to arrive for my big laser (1200X900mm) I used LightObjects for that, they seem to have some decent tubes at good prices. The power supply I got for it came from Cloudray Laser. I use Cloudray for almost everything except tubes, as their tube prices are kinda of high .

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(Ned Hill) #10

Good to know. Yeah Cloudray also sells on amazon and the one they were selling was actually a little more expensive than the one I got, but I just looked and it’s now cheaper! lol

(Ned Hill) #11

@funinthefalls Oh and thanks for the New User of the month award :smiley: Still can’t create new posts for another 5 hrs though :frowning:

(0.45 NACL) #12

I have gone through two blue power supplies in one year. I think I will try a Cloudray next time.

(Anthony Bolgar) #13

@Nedman I will bump you up a level. :slight_smile:

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