Upgrading the stock LPS

Installing a Non-stock LPS in the K40

Better quality and higher power LPS's can be obtained from companies like Cloud Ray.

The K40 can be modified to accommodate this kind of supply if:

• A 24vdc supply is added 
• The K40 is rewired to accommodate the new supply

Arguably this is a lot of change for a K40 but the machine will be better off because you will end up with:

• Better quality LPS
• Higher power 24V supply

Alternate LPS type

This type of supply is typically compatible with these instructions. Check the signals on the new supply to see if they match the schematic below.

Alternate LPS

The connectors typically look something like this:

Adding the 24VDC supply

You will have to purchase a 24VDC supply and mount it somewhere. The schematic below shows how it is wired in but not how to mount it. The mounting will depend on the actual supply you buy.

The stock 24vdc supply only handles about 1 amp @24vdc. So purchase a supply with more than this capacity.

Here is a supply with enough capacity to power your K40 even if you upgrade the controller later on.

24VDC @ 5A supply

Adding the alternate LPS

The schematic below is for a HY-T50 LPS but any supply with the same signals as shown in the schematic will work.

Remove and replace the stock supply

• Unplug the K40
• Unscrew the stock supply 
• Unplug the input connectors (either green or white)
• Cut the HV lead on the back of the stock supply leaving approximately a 4" pigtail so the stock supply can be used elsewhere.
• Procure a high voltage connector and add it both to the new LPS and the HV lead in the machine. Here is a good one: high voltage connector. Your supply may come with one.
• Mount the new supply to the floor within reach of the wiring harness and the HV cable.

Wire in the new supply

Using the schematic below modify the wiring harness to accommodate the new supply. You may have to cut off the existing connectors (white) to accommodate the new connectors types which typically are the green screw terminal type.

Ideally use pin crimps for better reliability. Here are the pins with crimp tool: Wire terminal connection kit.

Power on and test

This is a basic test procedure to verify your wiring.

• Unplug all the green connectors
• With a DVM on the ohms scale check the connections to the laser switch and laser test switches.

• The WP connection should read 0ohms to gnd when the Laser Switch is pushed.
• The TH connection should read 0 ohms to 5V when the Laser Test Switch is pushed. 
• Plug in the machine and power on [all connectors are unplugged]
• On the 3 pin AC plug verify the correct AC voltage with a DVM. CAUTION: Be careful not to short out the pins with your meter. 
• Power off the machine
• Plug in the 3 pin AC connector
• Plug in the remaining green connectors
• Power on the machine
• With a meter verify the voltages on the LPS connectors are correct per the schematic.
• Rotate the pot, the IN pins voltage, when measured to grnd, should vary from 0-5vdc
• The TH pin should read 5vdc when the Laser Test Switch is pressed
• The WP pin should read 0vdc when the Laser Switch is pressed.

Please Donate!

If this post helped you solve a problem, saved you time or was otherwise useful consider donating. Use the link in the upper right of the site.
Donations fund some of the expense of tools and materials for my shop and lab so I can bring you more content like this. 

Also let me know if there is other content you would like to see me explore!

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Thanks and please comment

Don

K40 Laser Power Control Characterization

Laser Power as a Function of Operator Controls

Recently +Ned Hill replaced his digital control panel with an analog one.

In the process he was thorough enough to take some measurements of the digital panels effect on laser power. Since Ned replaced the laser and the LPS this data may well describe an ideal K40 machine.

• %PWM, 
• Control Voltage (on the LPS-IN pin)
• Laser Current 

The +Ned Hill post and associated data are here and copied below for reference:

 

This data shows the important relationship between the digital panels setting [%] and its relationship to the control voltage [V(G-IN)] on the LPS-IN pin and in turn the lasers power level. The LPS-IN signal results in the laser current seen at the ma meter [mA]. 

Observations About the Data

Multiple Linear Regression models can be constructed that more show us these relationships in mathematical form. Perhaps these simple math equations can help us predict the K40's performance and therefore more accurately choose settings.

I ran linear regressions on the above data to see if rational models could be derived to describe the laser powers behavior.

How Digital Panel Setting Control Laser Current Behavior

A regression was calculated using column 1 and 2 in the data above. The below equations represent a model of the relationship between panel settings and the resulting laser current.

equation 1: Tube Current = Digital Panel % * .2784 {R^2 = 0.996}**

equation 2: Digital Panel % = Tube Current/.2784

You can use these equations to estimate the laser current for a given digital panel setting or alternately estimate what panel settings will result in a what laser current.

The **R^2 value and this graph shows that the equations above should be pretty good predictors of laser current for a given panel setting. 

Note: the equation above predicts that at 100% Neds laser should draw approx 28ma of current.

How The Pot*** Setting Controls Laser Current Behavior

A regression was calculated using column 3 and 2 in the data above. The below equations represent a model of the relationship between panel settings and the resulting laser current.

equation 3: Tube Current = Control Voltage * 5.24 {R^2= .999]**

equation 4: Control Voltage = Tube Current/5.24

You can use these equations to estimate the laser current for a given pot setting or alternately estimate what pot settings will result in a what laser current.

The **R^2 value and this graph shows that the equations above should be pretty good predictors of laser current for a given panel setting. 

Note: The equation above predicts that Neds laser should draw 26.2 ma with the IN voltage at 5vdc.

*** the pot is sometimes called "Current Regulation" on stock machines that come with a pot.

How Do I Know What the Pot Setting Is?

Good question! The equation above uses "Control Voltage" as one of the variables so how do you know that value? Install a DVM on the POT. It tells you the control voltage it presents at the LPS-IN pin.

To use this schema read or set the pot until the DVM reads the voltage [control voltage] you calculated using equation 4 above. 

Your Mileage May Vary?

Statistical models are based on empirical data like that given in this post can be in error in a few ways, garbage-in-garbage out. 

+Ned Hills data is likely "IDEAL" since it was taken with a new tube and LPS. As such it should be a great reference as to what a K40 machine can do.

Here are some sources of error (assuming I did the math right):

• Your LPS is weaker than Neds new one
• Your Digital panel is defective 
• The 5v supply used to drive the LPS-IN pin is an incorrect value
• Your tube is weaker than Neds new one
• Your mileage may vary

Local vs Programmatic Control

When firing the laser from the control panel the power is entirely controlled by the Digital Panel or Pot Settings. Therefore the equations above apply. 

However when under programmatic control from a PWM signal on the LPS-L pin the lasers power control is more complex. Its power is the product of the controller PWM % and the control voltage on the LPS-IN pin.

Using the Digital Panel To Set Laser Power

Laser current = (PgmPwr/100) * (DigitalPanel * .2784)

whereas: 

• PgmPwr = the power setting in the control software as a percent
• DigitalPanel = the setting on a K40 digital panel as a percent

Simple Example:

- DigitalPanel is set to 100%

- Lightburn power setting is 50%

     Laser current = (50/100) * (100*.2784)

     Laser Current = .5 * 27.8

     Laser Current = 13.9 ma

With the above settings when you push the test button you should see the meter read 27.8 ma

When running from program control you will run much less than 27.8 since the static value set by the digital panel will be reduced by any program setting less than 100%. 

Using The POT To Set Laser Power

Laser current = (PgmPwr/100) * (ControlVoltage* 5.24)

whereas: 

• PgmPwr = the power setting in the control software as a percent
• ControlVoltage = the voltage on the LPS-IN pin as set by the pot

Simple Example:

- Pot is fully on i.e. LPS-IN = 5vdc

- Lightburn power setting is 50%

     Laser current = (50/100) * (5*5.24)

     Laser Current = .5 * 26.2

     Laser Current = 13.1 ma

Is This Academic Knowledge?

If you expect your system to act exactly like +Ned Hill's then yes this may just be interesting information about Ned's machine. If however you value this information as a model of an ideal K40 machines laser power control behavior more value can be extracted. 

Ideas I have for using this knowledge are:

After taking a few settings *** on a machine you may;

• See how close it performs to ideal
• Create a model to match your actual machine by factoring the ideal model
• Use the model to aid in choosing operational power settings
• Attain a gauge to track your machines performance as it wears out
• Troubleshoot laser control problems without electrocuting yourself  

*** take 3 measurements of laser current vs control voltage or digital panel settings.

Donate?

If this post helped you solve a problem, saved you time or was otherwise useful consider donating. Use the link in the upper right of the site.
Donations fund some of the expense of tools and materials for my shop and lab so I can bring you more content like this. 

Also let me know if there is other content you would like to see me explore!

_____

Thanks and please comment

Don

Replacing the K40's Digital Panel with an Analog one

Why replace the panel?

It is not uncommon for the K40's digital panel to fail and more and more users are realizing the value of having a pot for control and an analog meter read laser current.

The digital panel

Understanding the k40 digital control panel

Adding an analog meter.

Adding-analog-milliamp-meter-to-k40.html

Converting the Digital Panel to Analog

Recently +Ned Hill had a LPS failure and tube replacement and decided to replace the digital panel and do a C3D upgrade.
We thought posting the conversion would be useful to others in the community

Schematic

I added a conversion diagram to the existing schematics I had for the digital panel.
It is located on the tab "Convrt 2 Analog".
https://www.digikey.com/schemeit/project/k40-powerled-v30-PM4QJBO303GG/

Conversion Instructions:

These conversion instructions are for supplies with all GREEN connectors. I can add the equivalent for other supplies upon request.

This conversion entails replacing the digital panel with an analog equivalent. The new analog panel has a switch, momentary push-button, pot, and digital voltmeter. The harness that goes from the LPS to the digital panel can be reused with the addition of two wires. These instructions refer back to the schematic.

-Build and mount the new analog panel (blue area)
-Remove the connector from the digital panel (orange area)
-Cut off the connector and strip back the wires
-Reconnect the 4x digital panel wires as shown in the schematic to the new panel (blue area)
-You will have to add 2x wires to the harness the G and the 5V

Note: this schematic also shows an installed pot and an associated control voltage DVM

Extracted from the schematic

Pictures From +Ned Hill Conversion

https://drive.google.com/file/d/1KdXSq2Fd41eVhH5xcn1moszJs72KrvJ7/view?usp=sharing

+Ned Hill Provided These Panel Designs

Panel with GLDC
Panel w/o GLDC

Supply Connections

Purchase Links

Please buy your parts using my affiliate links. It costs you nothing and it helps fund my activities. I defined a kit for this project which contains all the parts and links to amazon.
The entire kit is here and points you to these parts on Amazon.

Contributors

Thanks to +Ned Hill for his contribution to this post.

Donate?

If this post helped you solve a problem, saved you time or was otherwise useful consider donating using the link in the upper right of the site.
Donations fund some of the expense of tools and materials for my shop and lab so I can bring you more content.

----

Thanks, and please comment,
Don