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Monday, June 27, 2016

K40-S DC Power Systems Design


This post outlines the design for DC power in the K40-S

The  K40-S BUILD INDEX with schematics


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Your donations help fund additional research, tools and parts that I will return to the community as information and how-to's. 

General K40 DCPS design configurations

The LPS capacity:

  • +24VDC @1amp
  • +5VDC @ 1amp
Internally these are created from separate sections of the LPS so they have a total capacity of 29VA.
I do not know the power requirements for K40+smoothie when under full dynamic load and therefore
I am skeptical that 24VDC@1 amp can run everything in this box at full power.

I have not measured the dynamic load so at this point it is a suspicion. Power budgeting & verification is on my list of to-do's.

What configuration to use?

How you wire the DC power depends on what your expected full load will be.
Your full load includes DC current drawn from any/all of these:

  • Smoothie
  • Local Control panel (GLCD)
  • Steppers
  • Z table
  • Finder LED
  • DC pumps

DC Power Budget

Coming soon

Typical configurations

You can configure DC power to the Smoothie in three basic ways:

Way #1

+24VDC from the LPS
+5VDC from regulator installed on-board smoothie
Capacity: 24VA
Pro's: simple two wire connection
Potential Con's: marginal power for anything else, local display, finder led, Z table, pump etc.

Way #2 

+24VDC from LPS
+5V from LPS
Capacity: 29VA
Pro's: more capacity 5VDC + 12VDC
Potential Con's: marginal power for anything else, local display, finder led, Z table, pump etc.

Way #3

+24VDC from external supply with selected capacity
+5VDC from regulator installed on-board smoothie
Capacity: based on external supply choice
Pro's: full DC capacity for K40 + expansion. Simple 2 wire DC wiring
Potential Con's: more complex wiring of AC mains (to add on supplies) and purchase cost of external supplies.

What works?

Many of the K40 conversions use Way#1 and 2, so it seems to work, I just do not know if it is marginal.

I chose Way#3 because:
  1.  I want as much isolation as possible from the HV laser supply. In my configuration only the grounds are common.
  2. I wanted to make sure that the motors had full capacity under dynamic loads. I do not know the actual loads so I took the safe route :).
  3. I wanted extra capacity for future accessories like the local GLCD and driving the stepper for the lift table. 
BTW: I currently use the LPS 24VDC & 5VDC  for other accessories such as external lift table and the finder LED.

You can employ Way#1 or 2 and then measure the PS voltage to insure that it is not drooping.

My Current Design


The design is incomplete and is being documented here:


Separate 24vdc supply to smoothie to run the board and motors.

5VDC Power:

Integrated 5VDC regulator on smoothie and Display adapter provides all 5VDC.

Laser Power Output:


Separate 12VDC supply: pump, cabinet lights, temperature alarm.


All DC supplies will be fused using: 

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