Other Lasers

The following steps you through the key connections required to connect a Mini Gerbil to your system.  Some example implementations for DIY Laser Diode engravers and CO2 Laser cutter implementations follow.

Powering the Mini Gerbil

The Mini Gerbil is supplied via 5V pin on the large power connector.  The stepper motors and 5V share a common ground.  The bridge jumper should remain in its standard position (centre and 5Vext).
If you don’t have a 5V supply, you can power the Mini Gerbil from your computer via the USB.  Set the bridge jumper to non-standard position (centre and 5Vusb)

Stepper Motors and endstops

Laser systems which use stepper motors can be connected via the x and y axis motor outputs. You can feed the steppers with maximum of 35 Volt on the power connector on the Mini Gerbil or original Gerbil.
Next to the power input connector are the X- and Y-end stop or limit switch inputs.  Limit switches are Normally Closed (NC), meaning that when when activated, they will stop conducting between their C (common) and NC (normally closed) contacts.

Enabling the laser

The LO (“Laser On”) pin on right side of the Mini Gerbil’s large power connector can be used to switch on the laser (e.g. laser diode power module’s CS or EN enable pin).
The PWM output is the corner-most pin of the small connector next to the another small 4 pin connector.
The ribbon connector would typically not be used for non-K40 implementations.

Example project – DIY Laser Diode engravers

Laser diode schematic

Example project – CO2 laser

This Trotec laser comes with analog bush motors with rotor encoder feedback. I customised the motor mounts so I could replace them with standard stepper nema17 motors.
Above is the new replacement bracket for the NEMA17 motor and the old bracket for the brushless motor.
The installed NEMA17 replacement stepper motor driving the X-Axis.
The laser itself is an RF excited laser which is driven by a 1.9kHz PWM – mode 2 (see the customised $28 – link: parameter in Grbl)
PWM Laser freqValuePWM modeRemarks
244 Hz0fast pwmgreat engraving
61 Hz1fast pwmdither effects
1.9 kHz2fast pwmjust b/w
15 kHz3fast pwmjust b/w
Default0fast pwmDefault mode
122 Hz4phase-freq correctgreat engraving
1 kHz5phase-freq correctjust b/w
7.5 kHz6phase-freq correctjust b/w
Also the laser is way narrower than the K40 hence you see small lines. A diode laser needs driver electronics (constant current/voltage) with a TTL input that accepts PWM.
I have ran a small 500mW laser diode with Gerbil.
The laser driver here is a homemade circuit based on LM317 voltage regulator.
Two pictures, one above with the K40 and below one with a diode laser.
The Diode based laser and its big brother the K40 next to each other.
Simple setup with 12V and 5v inputs
Hope you enjoyed this write up and inspires you to build your own laser!

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