Here are the Mini Gerbil connections.
Powering the Mini Gerbil
The Mini Gerbil is supplied via 5V pin on the large power connector. The stepper motor supply (typically 24V) and the 5V share a common ground.
Stepper Motors and endstops
Laser systems which use stepper motors can be connected via the X and Y axis motor outputs. You can power the stepper motors with 35V maximum on the large power connector.
Next to the power input connector are the X- and Y-end stop or limit switch inputs. For a DIY machine, it’s easier to use the 5 pin connector rather than the ribbon cable connector. 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 Mini Gerbil’s laser fire output is valid when its:
- the LO (“Laser On”) is low, and,
- the PWM is a non-zero value.
So you need to work out how to utilise these two outputs to drive your laser system.
For example, the LO pin could be used to switch on the laser (e.g. laser diode power module’s CS or EN enable pin), while the PWM output is used to modulate the laser strength.
Example project 1 – DIY Laser Diode engravers
To interface to the Mini Gerbil, the laser diode must have a TTL level PWM input.
The image below is from a small 500mW diode laser.
Example project 2 – CO2 laser
This Trotec laser came with brush motors with rotor encoder feedback. Paul customised the motor mounts and replaced them with standard NEMA17 stepper 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 project used an RF excited laser which is driven by a 1.9kHz PWM – mode 2 (see the customised $28 – link: parameter in Grbl)
|PWM Laser freq||Value||PWM mode||Remarks|
|244 Hz||0||fast pwm||great engraving|
|61 Hz||1||fast pwm||dither effects|
|1.9 kHz||2||fast pwm||just b/w|
|15 kHz||3||fast pwm||just b/w|
|Default||0||fast pwm||Default mode|
|122 Hz||4||phase-freq correct||great engraving|
|1 kHz||5||phase-freq correct||just b/w|
|7.5 kHz||6||phase-freq correct||just b/w|