Model PMDX-126 Revision C
Multi-Mode Breakout Board
PMDX-126 board pictured as delivered.
(click on image for higher resolution version)
PMDX-126 pictured with PMDX-107, SmoothStepper, and cables.
(click on image for higher resolution version)
The PMDX-126 is a motion control breakout board for interfacing with the parallel port(s)
of an IBM-PC style computer or to the USB or Ethernet Smooth-Stepper.
New features of the PMDX-126 Rev C
- Separate and fully isolated Error and Reset terminals for servo drives now
work with almost all industrial servo drivers as well as the Geckodrive
G320X. Revision C can still be used as direct electrical and
mechanical replacement for revision A or revision B versions of the PMDX-126
New features of the PMDX-126 Rev B
- Drop-in replacement, electrically and mechanically, for previous version
- Jumbo Mode supports up to 5 axes from single parallel port
- Added hardware to slave a second motor for driving tandem axis configurations.
This together with Jumbo mode makes it possible to drive up to 6 motors with one parallel port.
- One additional input available as pin 10 of 2nd parallel port (can be
a general purpose input or act as "Machine Hold"). A total of 10
inputs are now supported.
- Input for pin 15 now offers a jumper option for strong pull-up resistor
for use with passive touch probes
- Improved E-Stop circuitry with better noise filtering
- E-Stop output now works even when PMDX-126 does not have power
- Supports the new PMDX-179 Remote Display Board with indicators for E-Stop,
Outputs Enabled, Steps Activity, Spindle On, Probe Active, Error Status
Codes, Motor Power ON, and Control Power ON
New features of the PMDX-126 (vs. older PMDX-125)
- NEW feature - Inputs can now accept 24 volt PNP sensor signals directly.
Many commercial routers and other machines that are upgrade candidates were
originally delivered with PNP proximity sensors and this feature makes it
much simpler to upgrade them. No external resistors are required. The inputs still directly support NPN
sensors, electro-mechanical switches, and logic signals without external
resistors or power sources being needed.
- NEW feature - Touch probe signal merge feature allows an active high
digitizing probe and an active low tool touch-off probe signal to be
combined into a single "probe" signal presented to Mach or other
CNC software. No more needing to juggle software configuration based on the
task at hand. Designed to work well with the probing features in the new MSM
(MachStdMill) screen set.
- NEW feature - K2 relay can be reassigned to pin 14 of port 2 so it can be
used even when pin 14
of port 1 is needed as the direction control bit for a PMDX-106 or PMDX-107.
- NEW feature - Option card slot improvements to allow new types of add-on
interfaces in the future.
- Connects to host using a two parallel ports or a single parallel port when
using expanded I/O modes. A DB-25 female connector is available for the
first parallel port. Additional 26 pin ribbon headers support use of a
second parallel port or direct connection to a SmoothStepper. The second port supports 4 input and 4 output signals. The remaining 8
data bits of the second port can be supported as input or
output by adding a PMDX-108-Input or
- Supports all signals present on the primary standard printer port. (8 data, 5 input, 4 output)
- Supports 4 additional high speed inputs using multiplexed I/O (Enhanced
Input Mode with single port and our Mach plug-in), or a second parallel port, or
the second port of the SmoothStepper
- Supports 4 additional high speed outputs using a second port or the SmoothStepper
- The additional high speed outputs can be used as step and direction for
greater than 4 axis operation when using two ports or the SmoothStepper
- On board LED indicators on all signals
- Terminal strip outputs provided for external LEDs showing status of Power On, E-Stop,
Charge Pump, and step signal activity
- All status inputs are optically isolated
- All parallel port signals are terminated and filtered to help resist noise
- All step, direction, and control output signals are buffered with 16 mA drivers
- Special isolated interface to sense ERR/RST signal used by Geckodrive
- Special isolated interface can reset and enable Geckodrive servo products
from the computer
- The special isolated interface for error sense and reset can also work
with many brands of servo drivers other than Gecko.
- E-Stop, Fault, ERR/RST, and "Charge Pump" timeouts turn off all
outputs without assistance from host software
- Provides one 30 ampere rated electromechanical relay useful for spindle
- Provides one 10 ampere rated electromechanical relay for auxiliary
- Relays have MOV arc suppressors for longer life of contacts
- Can directly connect with and provide power for PMDX-104
to provide 4 additional 5 ampere relay outputs
- Powered directly by AC mains 115 or 230 volts, switch selectable
- Self resetting poly-fuse protects mains power input
- Can provide +5 power to SmoothStepper through ribbon cables
- Can mount SmoothStepper as a daughter board using standoffs
- Has provision for option card mounting directly (PMDX-107
spindle speed control) or using a ribbon cable to
the PMDX-106 and other future products
- Screw terminal blocks with Step, Direction, +5 volts, and Ground for
outputs to drivers
- Buffered step and direction available as ribbon header for connection to
the PMDX-133/134 simple motherboards for Gecko stepper drivers or to other driver boards with ribbon header inputs for parallel port signals
- Screw terminal blocks for isolated status inputs also provide +5 volts and
+12 volts to power sensors such as the PMDX-170,
PMDX-171, and NPN proximity sensors
- Status sensor inputs work with mechanical switches, NPN sensors, 5 volt
logic signals, and 24 volt powered PNP sensors or PLC outputs
- For mechanical switches and NPN sensors the inputs work by
pulling the input to ground and no external resistor is needed
- For logic signals the inputs can be driven by 5 volt CMOS or
- For PNP sensors the input is pulled up to 24 volts by the sensor and no
external resistor is needed
- Pulse stretch circuit to allow narrow pulse encoder outputs to be used as
lathe index signal
- Built in test for generating step signals without need of a host computer
- Built in test step signals run at proper speed for Geckodrive stepper
driver smoothness adjustment
- "Charge Pump"/watchdog function has enhanced timing algorithm to
avoid teasing by Windows boot process
- Designed for easy interconnection with PMDX-104 and
provide solid state isolated outputs to connect with PLC systems, and power
- Designed for easy interconnection with PMDX-108-Input
to provide 8 additional isolated inputs when using a second port parallel
port or SmoothStepper
- Microprocessor and programmable logic allow for the future addition of
PMDX Breakout board feature comparison
Note: The step and direction signals used to run this board
as a real time CNC device require precise timing. These signals are normally provided by a
personal computer motherboard with an onboard parallel port, a parallel port interface
card plugged into a motherboard with ISA, PCI, or PCI-Express slots, or by an external
device such as the PMDX-410, PMDX-411 or
PMDX-422 with Mach4, or the SmoothStepper.
You cannot use a USB to printer adapter because
it will alter critical timing of CNC control signals. Laptop computers, even
those with parallel port interfaces, are not recommended as CNC control
computers due to design features that can alter critical timing. If you must use
a laptop be prepared to deal with these design issues and/or plan on using an
external pulse generating device such as the PMDX-410,
PMDX-411 or PMDX-422 with
Mach4, or a SmoothStepper.
Download the full manual in PDF format here
(revision 1.9, 27 Nov 2013, 381 KB for Rev C boards only).
(for manuals for rev B and rev A boards, see the User's Manual Archive page.
Click here for application notes on using the
Download the Mach3 Plug-In driver for the
(NOTE: You only need this plug-in if you are using Expanded Mode.)
(Most people do not need this plug-in.)
The PMDX-126 is priced at $188.00
Cables are sold separately, please order the ones that you need.
Note: Due to the many possible combinations of connecting
the PMDX-126, no cables are included.
If you are using a SmoothStepper, you may want to order 2 each PMDX-HDR26Ribbon cables.
If you plan to use a single shared parallel port, you may want to order 1 each PMDX-DB25MtoM cable.
If you plan to use two standard parallel ports, you may want to order 1 each PMDX-DB25Ribbon
cable, and 2 each PMDX-DB25MtoM cables.
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