Taig Micro Mill Breakout Board, SCHP, Pendant, Tach & Relay Box

Breakout Board, Safety Charge Pump, MPG Pendant, Spindle Tachometer & Relay Box

Breakout Board

Mounted C1 breakout board (BOB) having opto-isolation on all lines; independent PC (USB) & stepper-side
power supplies. This board is in between the PC & the stepper controller. The smaller card is the LPT2
C22 pendant interface which uses USB supplied power. The box has a metal cover.

In the BIOS, I turned-off the two RS232 serial ports & configured the two LPT ports to EPP+ECP.
LPT1 is on the motherboard (Hex 0378) & LPT2 is a PCI card (Hex D000). The first port address
is usually standard but the second port address can vary so examine the computer's devices menu.

LPT1 (steppers), LPT2 (pendant) & three power cables; two are USB & the mini-DIN is an external power supply.
The separate external power supply energizes the non-computer, equipment side of the opto-isolation board.

Opto-isolated LPT1 stepper-motor controller, spindle/mist/vacuum relay box control, limits/homing,
E-Stop inputs, & MPG2 pendant. The right ribbon cable seemed to have allowed electrical noise
from the steppers into the pendant circuit so it has since been made into a direct connection.

Breakout board detail. The LEDs are helpful but an oscilloscope is better for diagnostics.

Safety Charge Pump

Safety charge pump with the tachometer buffer chip mounted off the corner.

The LPT1 pin out logic states are unknown when they are not under direct control of a program, e.g., Mach3.
I/O can change during a system reboot or if the OS/Mach3 become corrupted, possibly causing unexpected
signals to be sent to the CNC motors. To eliminate this potentially dangerous problem, Mach3 can generate a
12.5kHz square-wave signal output (pin 1). This signal is only present when Mach3 has control of the motors.
The safety charge pump circuit monitors these pulses but if they are turned off or disrupted, it opens a relay in
the E-Stop circuit, drops the enable signal to the opto-isolation board & signals Mach3 to halt all LPT1 signals.
To activate the charge pump, a momentary (NO) switch is needed to enable the breakout board. Under Mach3
General Configuration window, the Charge Pump On in EStop is selected to allow a quick push/release of the
BOB enable button turning on the pump, otherwise, the momentary enable switch has to be held down while
simultaneously clicking on Mach3's master reset button. The tachometer input buffer chip is now held by the
plastic screw mount at the corner of the safety charge pump circuit board. C4 safety pump manual & wiring.

LPT2 pendant C22 interface board powered via USB. The C1 breakout board's +5V enable signal goes
through the two, NC E-Stops & this board's NO (blue) relay which is controlled by the pendant's E-Stop
button. The E-Stop circuit now also goes through the NO (blue) relay of the safety charge pump circuit.
In the BIOS, turned-off the two RS232 serial ports & configured the two LPT ports to EPP+ECP.
LPT1 is on the motherboard (Hex 0378) & LPT2 is a PCI card (Hex d000). The Port #1 address
is standard but the Port #2 port address can vary so examine the computer's devices menu.

Mini-DIN chassis bracket.

A collar with four small set screws holds the mini-DIN connectors together more securely than friction, alone.

MPG Pendant

This Manual Pulse Generator (MPG2) has 4 pulses/detent. There are 100 detents/dial revolution. Handy Pulser specs.
It is very important to perform the Mach3 jog control CAL. Disable any Mach3 brains (see setup guide) that are not in use.

Pendant stored in its supplied bracket.

Used extra scale brackets to allow hanging the pendant at three different bench edge locations.

Varies from the instructions.

PENDANT BRAIN SETUP
BRAIN	STATUS
Axis JogRes Selector.brn	Enabled
Enable.brn	Enabled
Disable.brn	Enabled
E-Stop W AutoReset.brn	Disabled
E-Stop WO AutoReset.brn	Enabled
ModIOMPG.brn	Disabled

Spindle Tachometer

Fairchild QRB1114 E-O sensor, Delrin tachometer pick-up housing & back plastic cover.
This is an updated design from an earlier DRO project. E is the emitter & S is the sensor.

Tachometer pick-up housing (back). The cover keeps out debris & prevents electrical shorts.

The Fairchild QRB1114 E-O sensor was first glued in using water-proof silicon & then wired.
Buffer/Tachometer circuit. Philips 74HC/HCT244 octal buffer driver used in the tachometer circuit.

The Fairchild QRB1114 940nm E-O sensor housing was mounted using Taig, pre-existing 10-32 tapped holes.

Aimed directly at the pulley center hub with a 0.2875" gap. It easily detects the dark set screw.

MEASURED RPM

# 100% RPM

1 555

2 950

3 1456

4 2174

5 3333

6 5555

7 8160

8 25000

Motor shaft turns 1795 RPM. Measured spindle speeds. Mach3 pulley assignments for the Taig Micro Mill.
Unless Mach3 is controlling the spindle speed, leave it on defaults (25000 RPM) so no error is generated.

Instead of gluing, a black plastic screw now retains the sensor.

Infrared Reflectivity

A near-infrared (NIR) camera picture, using the Sony DSC-F717 night shot mode, showing
the Fairchild NIR emitter glowing at 940 nanometers (nm) which is invisible to the naked eye.

Note how the Delrin & sensor housing appear dark but the black plastic retaining screw is white indicating high
reflectivity in the NIR. Objects that appear light or dark to the eye can exhibit either high or low NIR reflectivity.
This characteristic must be taken into account when selecting materials for use in NIR reflective tachometer
pick-up assemblies. For example, if the pulley's black set screw had high NIR reflectivity, it would not have
activated the sensor properly. This principle applies to all materials including: plastic, metal, paint, tape, etc.
Selecting a material based solely on its visual appearance may cause a sensing failure.

Added an index pulse card to sense a slotted disk for the Taig CNC lathe.

The tachometer pick-up cable was run along with the limit-switch cable, inside the same protective sheathing.

Tachometer (3-conductor stereo type) input jack & Teflon-covered cable.

Tachometer Buffer Chip

The 74HC/HCT244 (octal buffer driver) signal is inputted to LPT1, pin 15 (LED on). Tachometer/buffer circuit.
The mill tachometer index is now on pin 11 & the lathe tachometer index is on pin 15.

The original Parallax USB oscilloscope used to make the signal measurements.

Tachometer/buffer signal output at 555 RPM (9.25 Hz x 60 seconds/minute).

Tachometer/buffer signal output at 5555.4 RPM (92.59 Hz x 60 seconds/minute).

Tachometer input signal setup via Mach3's ports & pins, input signals, index enabled, LPT port 1, pin 15, active low.
The mill tachometer index is now on pin 11 & the lathe tachometer index is on pin 15.
In General Logic Configuration, do not have high debouncing/noise rejection values as they affect the higher RPM readings.

PropScope

The PropScope USB storage oscilloscope is supplied with two, 1x/10x BNC probes & expansion card.

Upgraded USB PropScope by Parallax has many more measurement capabilities than their original USB oscilloscope.
The plug-in DAC expansion card has connections for the function generator (FGN), an external trigger (TRG) & the Logic State Analyzer (LSA).
Channel 2 is disabled when the DAC card is plugged-in. See the startup document & user manual for the PropScope. Also see XYZs of Oscilloscopes primer.

An example of the PropScope generating & then measuring a 1kHz square-wave signal. The probe has a trimmer that is adjusted until the square wave is flat-topped.

An example of a PropScope hybrid screen displaying the oscilloscope, spectrum analyzer, & XY plot of the two, exactly the same, in-phase signals.

Another example of a PropScope hybrid screen displaying the oscilloscope & Logic State Analyzer.

Relay Box

A relay box for Mach3 control of the spindle motor, mist/coolant, vacuum, etc.

Modeled after Tom Benedict's relay box design. Since I used a plastic enclosure instead of metal, I mounted the two
Crydom D2425 solid-state relays onto a �" aluminum heat-sink plate. Heat-sink compound was thinly spread over the
entire back of the relays. The thick plate allowed for tapped holes to mount both the devices (8-32) & the plate to the
enclosure using (10-32, flush-mounted, 100� flat-head screws). Over specification on the relays obviates any heat
problem as the 1/3-hp motor draws 11A maximum on start (5.7A running) at 120V & the relays are good for 25A at 240VAC.
Each relay controls two sockets. These relays are perfect for this application as they use TTL with built-in opto-isolation.
The plastic enclosure is 4�" x 4�" x 2⅜". Four felt stick-on feet on the bottom complete the box.

The plastic cover was supported during milling by clamping the entire assembled box in the vise.
The domed galvanized metal cover gives good durability & extra room for wiring.

Note: Maximum off-state leakage current at rated voltage is 10 mArms. It can affect certain circuits.

The Mach3 tutorial explains how to setup, enable & test the pin outs. Uses LPT1 output pins 16 & 17.
Test the relay box to make sure the motor stops when the E-Stop is pressed.

Added two LEDs to indicate the status of Mach3 output signals calling for spindle and/or mist/flood AC power.