Below are the draft specifications for the MG3. Please leave a comment with any questions. References to ‘see’ in the Notes column indicate forthcoming webpages with more detail.
|X and Y axis control is default configuration. Either axis could provide switched control of rotary (see rotary setup) via the Awesome Tech rotary switch. Each motor connection is available via JST connector, with X axis also available via ribbon connector.
|Gantry speed (assuming the gantry is physically capable) at full step resolution.
|Tested to 400mm/sec. Higher speeds may be possible but not guaranteed. Wider speed ranges available via microstep settings. See MG3 details.
|A4988 supplied by default, DRV8825 also suitable
|Custom micro-step speed/ resolution combinations configurable via DIP switches, see MG3 details.
|Maximum motor current
|1A RMS total continuous for 1 second at 25’C in still air.
|This is more than sufficient for light weight gantries like the K40. For custom requirements, see external stepper drivers. Derate to 800mA in 40’C still air. Note: k40 power supply is only rated 1A maximum.
|External stepper drivers
|Possible via inserting jumpers between stepstick sockets and external stepper drivers.
|See external stepper driver setup.
|PWM frequency (pulse width modulation)
|Default frequency is 1500Hz, configurable between 60Hz – 80 kHz.
|Configurable via $28, see PWM configuration instructions. Configure via assigned numbers per frequency e.g. 5=1500Hz.
|Default is active high, configurable via firmware
|Configurable via $98, see $ settings. PWM Output available via pin header.
|LO polarity (LO = laser on or enable)
|Default is active low, configurable via firmware
|Configurable via $99, see $ settings
|LO electrical output pin
|LO connection sinks up to 40mA.
|LO Output available via power connector compatible with K40 power connector layout.
|See also connector specifications
|Air-assist output pin
|Supported, up to 150mA to source/sink from Solid State Relay.
|Wiring shown in MG3 details. See standard (M7/M9) and advanced configurations (M8/M9).
|Air-assist can be paused/resumed automatically during machine pause/resume operations
|Configurable via $96, see $ settings
|Air-assist invertable/ polarity
|Supported by $ setting
|Configurable via $95, see $ settings
|Pause, Resume, Reset button input pins (optional)
|See pause, resume and reset connection and configuration. Reset input enable/disable configurable via $94, see $ settings
|Safety door / check door input (optional)
|Supported. Connector type
|Safety door/lid input enable/disable configurable via $97, see $ settings and check door instructions
|Limit switches polarity
|Mechanical and optical X and Y limit switches supported. Multiple circuit options supported via DIP switches
|For standard and non-standard configurations see MG3 details. Limit end stops are available via JST connector which is compatible with k40 limit connector layout.
|USB Type Mini B
|Automatic Baudrate, no need to configure. See MG3 details
|Windows, Mac, Linux
|Lightburn, and most other gcode senders UGS, LaserWeb.
|More details to follow
|Current version is MG3_0003.
Updateable via 10 pin IDC cable and notched connector, ST Link v2 programmer dongle, and ST-Link Utility software
|MG3 Firmware updating instructions will be provided when new firmware is available.
|Stepper motor and driver logic level supply
|24V and 5V DC.
|The K40 power supply can supply 1A at each voltage, which is sufficient for a K40. Alternatively, 24V DC can be supplied externally, see MG3 details.
|Automatic reverse connection protection feature
|Protection against reversed power plug connection.
|Power availability sensing
|24V and 5V DC inputs are sensed and triggers user warnings: ‘Mini Gerbil 3 does not detect 5V supply from Laser!’
‘Mini Gerbil 3 does not detect 24V supply from Laser!’
|See MG3 installation guide.
|Via USB, drawing up to 150mA
|User and physical interfaces
|10 in total, displaying USB power, USB communications, air assist, PWM, LO (laser on), motor operations, 24V, 5V, X limit switch and Y limit switch
|See MG3 LED indicators (colour and position description)
|4 x M4 holes on rectangle 87mm x 54mm. Plastic standoffs recommended and included. Recommended not to use metal bolts in K40 case.
|See mounting instructions