MG3 specifications

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.

Motion2 axesX 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.1mm-400mm/secTested to 400mm/sec. Higher speeds may be possible but not guaranteed. Wider speed ranges available via microstep settings. See MG3 details.
Stepstick compatibilityA4988 supplied by default, DRV8825 also suitableCustom micro-step speed/ resolution combinations configurable via DIP switches, see MG3 details.
Maximum motor current1A 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 driversPossible via inserting jumpers between stepstick sockets and external stepper drivers.See external stepper driver setup.
Laser operation  
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.
PWM polarityDefault is active high, configurable via firmwareConfigurable via $98, see $ settings. PWM Output available via pin header.
LO polarity (LO = laser on or enable)Default is active low, configurable via firmwareConfigurable via $99, see $ settings
LO electrical output pinLO connection sinks up to 40mA.LO Output available via power connector compatible with K40 power connector layout.
Connectivity 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 functionsAir-assist can be paused/resumed automatically during machine pause/resume operationsConfigurable via $96, see $ settings
Air-assist invertable/ polaritySupported by $ settingConfigurable via $95, see $ settings
Pause, Resume, Reset button input pins (optional)Supported 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 typeSafety 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 switchesFor standard and non-standard configurations see MG3 details. Limit end stops are available via JST connector which is compatible with k40 limit connector layout.
USBUSB Type Mini BAutomatic Baudrate, no need to configure. See MG3 details
Personal computerWindows, Mac, Linux 
SoftwareLightburn, and most other gcode senders UGS, LaserWeb.More details to follow
Controller firmwareCurrent 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 supply24V 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.
ProtectionAutomatic reverse connection protection featureProtection against reversed power plug connection.
Power availability sensing24V 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.
Microcontroller supplyVia USB, drawing up to 150mA 
User and physical interfaces  
Indicator LEDs10 in total, displaying USB power, USB communications, air assist, PWM, LO (laser on), motor operations, 24V, 5V, X limit switch and Y limit switchSee MG3 LED indicators (colour and position description)
Mounting holes4 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

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