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Thursday, July 14, 2016

K40 Dynamic Laser Response testing

K40 Laser Response Testing:

This post tracks activities related to testing the laser light response to various control inputs to the Laser Power Supply (LPS).
This testing was prompted by the confusion surrounding how to control the laser  and it's power from aftermarket controllers, more specifically, the Smoothie.

Test equipment:

There are three artifacts of the testing environment.

1. PWM generator:

The PWM generates a 5v, low or high true PWM signal with variable frequency and duty cycle.

Mode switch PWM position:

  • This switch must be in the "PWM" position to output a pwm signal.
  • In the Pulse position the momentary button is enabled.

Signal polarity:

The polarity of the pwm signal is selected via jumpers on the breadboard. See schematic.

Freq. & Duty cycle:

The frequency and duty cycle are set using two potentiometers on the control panel.

The PWM generator

2. Interconnect: 

The cable from the breadboard connects to the LPS supplying power to the tester which in turn supplies PWM and pulse control signal's to the Laser Power Supply.

3. IR Receiver Module (IRRM):

The IR receiver module contains a reverse biased photo diode mounted below a small water reservoir made from a drilled acrylic plate. The water is expected to be an attenuator at high power.
The detectors output varies proportional to the laser light providing an electronic signal that correlates with the dynamic and static characteristics of the lasers output. This signal can be connected to an oscilloscope showing the dynamics of the lasers output and timing. A voltmeter can also be connected to the IRRM to measure static outputs.
Top "Laser: View
Perspective view
The IR sensor (from RS)

Test plan:

Potential Sources of Error:

  1. IR detector response: if the IR sensors light response is slower than the lasers output response we could be measuring the response of the sensor and not the laser [unlikely but be aware]
  2. Peak Measurements: the IR sensor module is not capable of accurately measuring the output in watts as this is a dynamic peak measurement device.[this test is not attempting to measure static power output].
  3. High Power: at various power levels the attenuation characteristics of the water drop could non-linear-ize the amount of light the IR sensor detects.[test repeat-ability]
  4. Optical reflections: the optical characteristics of the water drop could reduce the repeat-ability of the IRRM measurement. [test repeat-ability]


I can see where an Arduino based PWM controller might be advantageous:

  • Better isolation between DF setting and frequency (in 555 designs it is hard to isolate these controls)
  • More accurate and wider frequency range
  • Ability to control the number of PWM cycles making it safer and more predictable measurements. Not advertenlty left with PWM running.
  • DSP measurement of IRRM output in more sophisticated version
  • Automated data collection 
  • Automated control of the laser analog power.

Enjoy and comment

K40 Coolant


After flailing for a few days with what I thought was a bad power supply or tube it dawned on me that I had never used distilled water (I am always tearing it apart and how conductive can the water be anyway?) and I knew that I had some algae in the tank.

I knew better from listening to others but seriously arching through the glass jacket through the water to ground in the tank? You better believe it, I have now proven it, to my satisfaction that is. I should have known better because I worked with someone that was blowing supplies every month and it turned out to be CAR antifreeze (that's definitely a no-no).

The symptoms was an intermittent screeching noise when the laser was in operation. It did not do it continuously and it did not do it every time. I thought it was coming from the LPS and finally was about to conclude that it was a failing winding inside the fly-back transformer. What bothered me was I could see no evidence of an arc even in a dark room. What I did notice was the flux beam shifting and changing shape at the anode end.

So I cleaned the system put in distilled water (3 Gal) and RV antifreeze (1/2 gal), powered it up and from then on no screeeeeeching just smooth wood smoking power. 

I wonder how many good supplies and tubes have been replaced or fry'd do to this problem.


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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. 

The Simplest Cooling System Approach

"The simplest and safest for humans and machines it to use pure distilled water in a closed system which prevents contaminates that might encourage algae growth. Change water every 6 months with other maintenance." 

From +Arthur Wolf 

The underlying principle is that pure uncontaminated distilled water does not grow algae.

Coolant Conductivity Data

Here is some actual data for cooling water conductivity. I don't know why I never thought of measuring this before. I wish I had measured the water before emptying it.
I used a HM Digital COM 100.
The temp was about 60F-65F
Distilled water = 2.6 uS
Distilled/RV mix:6:1 = 142 uS
RV antifreeze = 414 uS
Don's tap = 370 uS Prestone (ethelene glycol) = 633 uS
Vinegar: 137 uS
"Purified" water: 10uS
Aquarium algaecide: See below

uS = micro-siemens

Algaecide for Algae Prevention

Algaecide: Tetra Algea Control
Active ingredients: 5% Poly [Oxyethylene (Dimethyliminio) Ethylene (Dimethylimino)
Ethylene (Dimethylimino) Ethylene Dichoride]
Recommended dose for Aquariums: 1ml per 12 gallons, 1 drop (.084ml) per 1 gal (3.8L)
Conductivity measurements: 1 drop added to 1 gallon of fresh distilled water.
  • Reading before algaecide control = 4.8uS
  • Reading after adding algaecide = 4.9 uS
Conclusions: this brand of algae-cide does not raise the conductivity of distilled water. (continuing tests to be conducted).
Expectations: adding 5 drops, (.42ml) per 5 gallon bucket of distilled water will not increase the conductivity of the water but will prevent algae growth.

Clorox for Algae Prevention

Clorox: mostly sodium hypochlorite

Sodium Hypochlorite Conductivity (note: these measurements were made with an ohmmeter and that will not work so do not use this data). A meter will not work to measure conductivity because DC polarizes the solution. AC is used to solve this problem so insure your meter or measurement method uses AC.

Here is a better method for calculating.

Estimating Practical use of chlorine:

How much Clorox needed to kill algae?

1/4 teaspoon per gallon of water = .042 oz/gal
.042 * 5 = .21 oz/5 gal = 6.2 ml/5 gallons

Measurements to attain conductivity at relevant concentrations:

  1. 2.5 gallons distilled water was added to bucket. Conductivity = 2.2 uS
  2. Added 3 ml Clorox. Conductivity = 44.9 uS
  3. Added additional 2.5 gallons. Conductivity = 22 uS
  4. Added 3 ml Clorox. Conductivity = 46 uS

Final (for now) formula:

Mix 6 ml of Chlorox with 5 gallons of water and expect the conductivity to be in the 40's uS.

Long Term Testing of Water Conductivity

I started a test of tap water conductivity to see what the conductivity does over time and as algea grows. I am also monitoring my main tank (B).

Test setup:
A. Water in bucket: from my tap sitting indoors in open container
B.  Water in my K40 tank

My K40 tank (B) has the formula from above.

Tracking my water conductivity over time

Water bubble treatment

Clearing bubbles after a water replacement makes water replacement a chore as I have to lift (quite high) and rotate the machine to clear them.
If I could find a way to clear the bubbles I would be more motivated to change the water more often.

Rotate the tube:

I can do this but it will require an optical realignment and it increases the chances for HV arc to the case as the anode swings closer to the cabinet.

Add Water Wetter

I tried adding "Water Wetter" @ 1oz per 3 gallons. It raised the water conductivity from 4.0 us to 410us making the coolant unacceptably conductive. The bad part is that it did not remove the bubbles much at all.
Water Wetter measured without dilution is very conductive and read infinity on my meter. Even after I rinsed a bottle that had the wetter in it and then added distilled water it raised the conductivity from 4.0us to 40us.
The bottle suggests 1oz per gallon so I was using only 1/3 the amount recommended for car cooling systems.

Add Dish Detergent

I added 1/4 oz of Dawn to 3 gallons after the test above. It did not change the conductivity and it did not stop the bubbles.


Water as a Coolant for Lasers

Enjoy and comment,
Maker Don

Saturday, July 9, 2016

K40-S Wiring

Smoothie conversion cables and connectors

 This post describes collects information about various connectors and cables

The  K40-S BUILD INDEX with schematics


Please consider donating (button to the right of this post).
Your donations help fund additional research, tools and parts that I will return to the community as information and how-to's. 


This connector listing is worth its weight in gold ....

Four position VBB connector:

The Smoothie came with 2 pin Terminal Block Lug 5mm connectors. I found these four pin versions that I prefer so that I can insure that nothing it plugged in wrong:

Friday, July 1, 2016

My Maker Spaces

"A clean shop is an unused shop!"

The "Shed"

At the door

Looking left to assembly, code and test areas

The assembly/test bench

The code and test chair

Looking back from my chair at K40 and parts shelves

Looking back from my chair to 3D print and cutting machines

The shop

From the door to the fab shop

Sharp tools are safe tools, air filtration for my lung health

Main work area on shop made bench

Secondary bench, drill press and parts storage

My Stubby lathe from Australia

Miniature machine shop and carving area

Looking back from machine shop

Wood storage, table and metal saw. Paint booth.

Band, & chop saws. Surface sander

View from garage door.

K40-S Motors


Identifying motors in my K40-S as part of my conversion

The  K40-S BUILD INDEX with schematics


Please consider donating (button to the right of this post).
Your donations help fund additional research, tools and parts that I will return to the community as information and how-to's. 

What steppers are in my machine?

Y stepper: 17HM4410N-03AD-Z
X stepper:17HM3448N-15AD

K40 X stepper in my K40.
Motor specs

+Frederick Deryckere  over @ man made mahem found the vendor and specs for the motor.

From his blog: "After a while though I got lucky and stumbled upon the website of the original manufacturer of the motor: In the end, the ‘dragon’ logo was a dead giveaway. I contacted their support team, and they proved surprisingly helpful. Below is the spec sheet they sent to me, accompanied by the sheet of the replacement motor I bought (not from them ;-)). Seems close enough to me."

Y motor: 

Vendor; Spec sheet, Mech Drawing

X Motor

Others I know of








( Max)
Holding Torque
( min)



Motor Replacements

I have not used these motors but collected the links from others who have.

Pictures of K40 tension adjustment assy: