Laser Power Supply Interface PCB

Laser Power Supply Interface



I want to combine all the circuits I have created for my laser power supply into one interface PCB. This project is attempting to do that.


It is planned to have the following features.

  1. Cooling
    1. Measures the flow using the Koolance flow switch
    2. Adjustable safe flow rate through pot setting. Allows it to be stup for different flow requirements.
    3. Sets fault on power supply water pin on low flow
    4. Blinks the LEDS on the flow switch. The flow switch has some blue LEDS in it. I will hook into these and use them as a visual flow feedback. I am not exactly how I will use it yet.
  2. Laser Power Control.
    1. Digital pot sets power level.
    2. Converts Mach3's slow PWM to a real 0-5V level at the power supply.
    3. Optional external manual pot. This allows you to switch over to fully manual mode via an external pot.
  3. Power Supply Enable
    1. Monitors this line from Mach3
  4. Power Supply Status to Mach3
    1. Sets an input pin that Mach3 can monitor about status of power supply. This will let mach know when the power supply has benn shut down for flow or safety interlock reasons.
  5. Interlock Switch circuit
    1. Cover, door, Emergency switches can be looped through this circuit for safety off purposes.
  6. LCD Display
    1. Shows flow as a percentage of fault level. 120% would mean the flow is 20% above the point at which it will fault.
    2. Shows current power level.
  7. RS232 Interface
    1. Status output
      1. Flow rate
      2. Power Level
      3. Enable status
    2. Future Modbus interface


Ciruit Design

I am planning to use a Microchip PIC18F452 microcontroller.


Pic Pinout


Here is the prototype schematic. This is incomplete and will change several times before the project is done.

Schematic Thumbnail


I have just about everything working. I tested the cooling flow monitor and the power level control. I need to test a few more things, then start to layout the board.


Got parts and Switched to PIC

I finally got my digital pot. I am using a Microchip MCP41010 256 step 10K pot. I am not sure the pot is the final way I want to go. I may go with a DAC instead. The code should all be the same. I was struggling with the PsoC part. The multiple external interrupts of the PIC part are going to make this a lot easier.

I am prototyping it using my EasyPIC4 development board from MikroElectronica. I am using the CCS C-complier. These combination is a very easy way to prototype. It can compile and reload the code in about 15 seconds. The MikroE board also makes prototyping very easy. The board makes thing very complicated looking, but if you look at the schematic, it will be a very simple circuit and easy to build.

So far I have the LCD working, I have it reading the power level from the Mach3 PWM. It have it correctly setting the digital pot and I have the external pot mode working too.





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