The Texas MicroCircuits MP2 pendant and Z-axis Touch-Off (ZTO) have been the subject of a detailed design process. Here at TMC, we work with a variety of CNC equipment ranging from small Sherline mills, lathes and engravers through to larger plasma gantries, so we understand the features that a pendant needs to have. We use the MP2 to control our production mill, lathe, engraver, and plasma gantry.

As any experienced machinist will know, well engineered products take time and effort to produce. The MP2 unit has been a long time in design and development. The result is a unit that we believe to be 'best of breed'.

(ZTO Specs coming soon)

Requirements

The TMC development team started out with a list of requirements and desired features.

These included:

Click on any photo below to enlarge:


 

Hardware

We scoured the market for a good joystick knob, but they were all either too big, too lightweight, insufficiently tactile or of poor quality. We even designed and made our own - but this was a costly and time consuming process. In the end, the solution was surprisingly obvious. The market for handheld game controllers is huge. Big companies, like Sony, have spent lots of cash designing joysticks that are operated by a thumb (anybody who has used a PS2 joypad controller will know that this is an excellent user interface). So, the MP2 joystick knob is a variant of this type.

The enclosure is made from anodized aluminum and is approx 5" long x 2" wide - the perfect size to fit neatly in the hand. We selected this enclosure with a view to single-handed operation of the pendant. The enclosure gives solid support for our front panel and has removable end caps. Having removable end caps allows users to open the unit to carry out 'chip swaps' for any software updates that they might want to apply.

The front panel is also a 'custom made' part. These are micro-engraved on a precision machine to give a very high quality of finish. Each front panel takes over 22 minutes to engrave. We keep the engraver feedrate low to ensure the highest quality of lettering. If you require more than a few pendants, we can even include your custom logo on the front panel design.

The pendant connects to your CNC control PC via a keyboard cable. This cable simply plugs in to a free USB port on your control PC via a supplied keyboard-to-USB adapter. The pendant is powered directly from the PC and requires no batteries or other connections. Cable lengths of 10' are supplied and we support up to 25'.  We have actually successfully tested the unit with cable lengths of up to 200'.

The 'mode' switch allows the selection of one of ten operational modes. These modes have been chosen to reflect the most frequently used operations that a CNC machinist performs. Each mode changes the behavior of the joystick and pushbuttons. The behavior is entirely configurable in that it is determined by the firmware loaded onto the pendant. Currently, we supply the MP2 pre-programmed for use with Mach3 CNC software.

The six pushbuttons are laid out in two rows of three buttons. The top row is dedicated to performing Start/Pause/Stop g-code operations. The second row of buttons are 'soft' in that their function changes with the selected mode.

Three LED indicators give visual feedback on the status of the pendant and selected jog modes.

Functions

The MP2 support the following functions:

Modes (selected by the mode rotary switch):
"Zero" - Moves all axes to their zero position according to the DROs
SafeZ - moves Z axis to safe position
ToolC - moves all axes to a tool change position
RefAll - moves all axes to 'home position'
Rewind - rewinds to start of g-code file
Macro - lower three buttons each run a user preprogrammed Mach3 macro (Mac1, Mac2, ZTO)
X/Y - joystick operates X/Y axes
Z/A - joystick operates Z and Auxiliary axes
SOvr - Spindle override - north/south on joystick overrides spindle speed
FOvr - Feed rate override - north/south on joystick overrides feed rate

Buttons:
Start - run the currently loaded g-code - same as Cycle Start
Pause - pause the currently running g-code - same as Feed Hold
Stop - stop the g-code run & reset tool (not to be confused with ESTOP - NOT a replacement for a proper ESTOP switch!)
Goto - the goto button performs a variety of functions, based on the position of the mode switch
Z1/Tog - Zero the X or Y axis (depending on currently selected mode) and toggle the Spindle On/Off
Z2/Res - Zero the Z or Aux axis (depending on currently selected mode) and resets the Feed Rate Override

Indicators:
Two green LEDs which show currently selected jogging mode (Normal/Fast/Incremental.)
One dual color LED (green/red) which shows operational status of the pendant (flashing red for disabled, solid green for running)

Joystick:
The primary input device. Freely moveable (not constrained to just N/S/E/W movement).
Depending on mode, the joystick moves the axes or controls spindle and feedrate overrides.
Features a switch that is activated by depressing the joystick knob. This is used to switch jogging modes and move the pendant between "enable" and "disabled" modes.
 

Software

The 'brains' of the pendant is held in a single chip microcontroller. The TMC team develop the software that runs on this device. This means that we have complete control over the behavior of the pendant.

The code monitors user actions such as joystick movements, switch and button presses and translates these into keyboard scan codes that are sent to the CNC Control PC. The MP2 acts like another keyboard attached to your PC.

We understand the importance of safety when working with machines. With this in mind, the software implements a 'timeout' which disables the pendant keys and joystick after a period of inactivity, placing the pendant into 'standby' mode. This prevents unwanted key presses from being sent by the pendant if a button is accidentally pressed whilst picking up the pendant from the bench. The joystick features a little switch which is activated by depressing the pendant knob. Pressing down on the joystick knob will take the unit out of 'standby' mode. It is also possible to force the unit into standby mode by holding the knob down whilst the unit is operational.

Our software is continually being enhanced. As we use the pendant, ideas for new features are generated. We evaluate these and experiment with the most interesting ones. If an idea is good enough, we will incorporate it into a future software release. User feedback is important to us. If you have a feature that you would like to see implemented, drop us a note. Performing software updates is straightforward. We send you a replacement microcontroller chip. You open up your pendant enclosure, remove the existing chip (socketed) and pop in the upgraded one.

Futures

As the MP2 goes to market, we already have plans for new features. Some of these involve new software routines, such as the ability to configure 'softkeys' to send out user-specified codes. Existing users will be able to upgrade their MP2 if they so wish.

The MP2 is the first in a range of pendants that we plan to build. Handheld units are good for environments where the operator isn't wearing heavy duty protective gloves. A gloved hand needs bigger buttons to press. With this in mind, we are designing a bench-top model that will stand alone and have larger controls.

We are thinking of producing a control panel that will have many of the functions of the MP2. Click here and tell us what you think.

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Click Here for Pricing and Shipping Info for the MP2 and ZTO