Laser Power Controller

The HackLab's Laser Power Controller controls the blower and tube, and monitors them to ensure they are working. It's located in the big box under the laser control computer.

Hardware

• Unitronics M91-2-R1 Programmable Logic Controller
  • Programmed using U90 Ladder software (in ladder logic)
• 2x Siemens contactors
  • One for blower, one for tube
• 1x 24V PSU
  • Powers most control electronics
• 1x 12V PSU
  • Powers the light outside the room
• Pressure sensor
  • 0-15" WC differential pressure input
    • + input to ambient, - input to duct where it enters the laser
    • Reading increases with increasing vacuum
  • 4-20mA output
• 10A circuit breaker for main power input
• Many terminal blocks to tie wiring together
• Knob, buttons, flashy lights, buzzer

Connections (on right side of box)

• BLOWER - Connect blower power cord
• TUBE - Connect tube power cord
• E-STOP Loop - Connect to 1/8" plug coming from laser (which integrates the power controller into the main E-STOP loop)
  • Tip/Ring connected together when everything is normal, connection broken when in E-STOP.
  • Sleeve not used
• Warning Light - Connect to 1/4" plug coming from the light outside the laser room.
  • Provides +12V when tube is powered.
• Power input - Connect to NEMA 5-15p to IEC C19 cord

Maintenance

• Pressing the red i button on the PLC when the selector is in STANDBY and nothing is running gets you into the maintenance menu.
  • Use up/down arrows to scroll through the menus.
    • First screen shows you the hourmeters for laser and tube.
    • Second screen lets you set the pressure thresholds for low and high faults, and shows you the current duct pressure in inches WC.
      • To see the duct pressure with blower running, unplug the blower from the unit and plug it directly into an AC source, since you can't get to this menu with the blower running normally.
    • Third screen lets you set the maximum length of time the blower will run to ventilate the area after a job.

Faults

• Faults will prevent the tube from starting if they happen as the blower is being turned on.
• If a fault occurs in the middle of a laser job, the system will keep functioning but sound the alarm/light the FAULT light
  • You can silence the alarm by holding the START button, if you need to finish the last tiny bit of a job or if you know for sure it is a false alarm.
• Faults can be cleared by switching to STANDBY and waiting one second.
• Current faults are:
  • DUCT UNDERPRESS - Duct pressure is lower than the threshold. Check to see if the blower has failed or the window has blown closed.
  • DUCT OVERPRESS - Duct pressure is higher than the threshold. Check to see if the duct is clogged at the laser end.
  • BATT LOW - The internal SRAM backup battery in the M91 controller is low. Replace it.

Program

• Firmware/program can be edited using the freely downloable Unitronics U90 Ladder software
• Code for it is stored at https://github.com/hacklabto/laser-power-controller

Photos