LAOS Laser

h1. PWM

PWM stands for Pulse Width Modulation and is used to control the power of the laser. On the HPC3020 you will see a mA meter and a turn knob that will allow you to control the power of the laser by hand. With PWM the Laos board can take over this function, which allows for e.g. engraving of pictures or controlling the right power settings for certain materials. 

Based on the laser power supply, there are different connections required.

In general we can identify 3 cases:

# Only "Laser ON" signal connected to the power supply

# Seperate "Laser ON" signal AND "Analog power" (PWM) input used on the laser power supply

# "Laser ON" and "PWM" signal combined (not covered in this description) 

The outputs of the Laos board have opto-couplers that need to be connected to the right pins of the power supply. Usually a pull-up resistor is required between the collector of the opto-coupler and 5VDC. The emitter of the opto-coupler is connected to ground. In some power supplies the pull-up resistor is already present, on some inputs an additional resistor is required.

h2. Example of enabled laser PWM

To use the power control from the LAOS board, you need to connect the _laser PWM_ output  to the _ANALOG_ input of your power supply. 

Note: There is a difference between the PWM connections of boards with revision<3 and board revision >= 4!

Revision 3 boards: "Laser PWM" output is actually on the "Exhaust enable" connector (J37 PIN 1 and 2)

Revision 4 boards: "Laser PWM" output is correctly on the "Laser PWM" connector (J39 PIN 3 and 4)

On the LAOS board this is _J39_, together with _laser on_. You need to make a two wire cable with a 3 pin JST on one side, and a 4 pin JST on the other side.

* Use a 470 ohm (0.25W or more) pull-up resistor between +5V and analog in at the laser power supply side. 

* "C" connects to the analog in pin (and resistor)

* "E" connects to GND   

!pwm-connector.jpg!

(This image is slightly confusing because the 4 pin JST already contains 2 cables for the _laser on_ connection, right?)

h2. HPC3020 laser

hpc side, very much a poc (a what?) (How do I recognize the analog input? The image doesn't really help)

!IMG_1154.JPG!

An alternative image of a power supply, could someone highlight the analog input?

!powersupply.jpg!

laos side

!IMG_1157.JPG!

h2. KIII laser

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