Adding a safety switch to your laser

The purpose of a safety switch is that it prevents humans being exposed to the laser while the laser is in operation. It’s mounted on the lid, and so is sometimes called a lid switch. If a person opens the lid then the machine will halt its operation and shut down the laser beam. Closing the lid and pressing resume (either within the laser program or physical resume button) will continue the laser operation.

There are two ways of adding a safety switch, either the safety door pin or the pause button. There is very little difference except that resume on safety door waits a few seconds (dwell time) before resuming. It comes from its CNC past where a system waits for the spindle to be ready.

Adding a safety lid feature is done via a NC microswitch. NC stands for normally closed at rest. Since we mount the NC microswitch on the K40 chassis near by the lid, the lid will press the micro switch when the lid is close hence the NC contact is open. When a user opens the lid, the micro switch is release and goes to its NC state closing the contact.

The wiring is simple – the micro switch NC pin goes to the safety door pin on the Mini Gerbil and micro switch Common in goes to ground on the Mini Gerbil. The Safety Door and Ground pins are on break out connectors called J1 and J2. Make sure that you bundle the wiring neatly together and away from the laser output and return line (high tension cables also known as high voltage). Also keep the lines away from the mains AC wiring so it does not pickup any noise signals.

Aim to use KK254 Molex type connectors or similar (example from Australian retailer JayCar https://www.jaycar.com.au/4-pin-0-1-header-with-crimp-pins-2-54-pitch/p/HM3404) The pitch is 2.54mm. Farnell and Element14 and RS online have them as well. (Molex, KK 254 Female Connector, 2.54mm Pitch, 4 Way, 1 Row)

2 thoughts on “Adding a safety switch to your laser”

  1. In the picture there are 2 abort pins
    1 on j1 and one on j2.
    On mine, received last week there is only abort on j2.
    On j1 it is labeled wp.
    Which surprises me because when it is waterprotect I would have expected it to be shortens to ground.
    So my question is simple. What is the wp pin on j1 used for?

    Grt. Erik

  2. Hi Erik,

    We had a few requests for a WP output so you could use it to drive a solid state relay to switch on a pump or air assist (M7 or M8 command).
    The firmware is being upgraded to support this and other additional features like ability to invert PWM/LO logic and bug fixes. It is still under test before being released.
    Cheers, Paul

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