T-REX 2006 Hot-Wire Interface


NOTE: this document is evolving as of 2/13/06 since the motor-control system is not yet finalized.



Prometheus  DAQ Connector – Motor controls and feedback assignments. 2

Connector Pinouts from Prometheus Manual 2

Diamond Analog Connector – Input Signal assignments. 3

Connector Pinouts from DMM-32X-AT Manual 3

Bulgin Pin Assignments:  Not Yet Finalized. 4

Bulgin Connector Layout: 4

DC Motor: 4

Interface Board Layout: 5

Components: 5


File Reference:

Word Doc:  /net/isff/projects/TREX/doc/TREX­_HotWire_Interface.doc

Web Doc:   /net/www/docs/rtf/projects/trex/isff/HotWireInterface.htm


Description: This document outlines the interface and wiring used for the Hot-Wire to Prometheus data system for TREX.  The interface board fits a standard NDAQ footprint of ~3.5x6” to fit on the existing bulkhead panels.   Because only 1 board is needed it will be built as a prototype PCB and coated ‘by hand.’   Components used for the interface are referenced at the end of this document.


Power Connections: +12VDC Power for the interface panel is provided via connector J1 from the PC104 stack power supply.


Ground Planes / Bonding: There are two isolated ground planes on the interface panel: one for power/digital ground and the other for analog ground.   These planes are not bonded to each other or to earth via the mounting hole pads.    Bulgin connectors have pin-8 and pin-2 (shield) directly connected to the dig/pwr. ground plane.   



Prometheus  DAQ Connector – Motor controls and feedback assignments.

The Prometheus 50-pin connector J14 is attached to J2 on the interface panel.  The following table summarizes the signal and pin assignments for this connector.

Note:   PortA=Input,  PortB=Output,  PortC=Input



Dir. (+5) Control

Motor +12 Control


Bulgin – Pin 1

Stepping Clock

Photo-2  Bulgin – Pin 2

Left Limit

Photo-3  Bulgin – Pin 6

Right Limit

Photo-4  Bulgin – Pin 7

Right Limit

Photo Interrupter +5 Vcc

Motor - 1

B6 – 15

B7 – 16

C4 – 21

C6 – 23

C0 – 17

C2 - 19

B4 - 13

Motor - 2

B2 – 11

B3 – 12

A4 – 5

A6 – 7

A0 – 1

A2 – 3


Motor - 3

B0 – 9

B1 – 10

A3 – 4

A1 – 2

A7 – 8

A5 - 6




Connector Pinouts from Prometheus Manual



Diamond Analog Connector – Input Signal assignments.

The Diamond MM-32X-AT 50-pin connector J3 is attached to J3 on the interface panel.   Inputs are routed as differentially with the option of jumpering the ‘shield’ pin to the analog ground plane if needed.  The following table summarizes the recommended signal and pin assignments for this connector.  These can be obviously changed by plugging in the BNC cable connectors elsewhere!




Signal - +/- pins



Motor - 1

VinO – 3,4

Vin1 – 5,6

Vin2 – 7,8

Motor - 2

Vin3 – 9,10

Vin4 – 11,12

Vin5 – 13,14

Motor - 3

Vin6 – 15,16

Vin7 – 17,18

Vin8 – 19,20




Connector Pinouts from DMM-32X-AT Manual




Bulgin Pin Assignments:  Not Yet Finalized


Bulgin Pin



A = Red


Input: Photo Interrupter -1

Stepping Clock

B = Bare



Direct connect to Ground Plane

E =


Switched +5

Vcc for Photo Interrupters

D =


Motor Gnd – Default direction

Relay Pin-6.  +12 with Dir.Control high

C =


Motor +12VDC – Default direction

Relay Pin-3.  Gnd with Dir.Control high

F =


Input: Photo Interrupter -2

Left Limit Position

G =


Input: Photo Interrupter -3

Right Limit Position

H = Black



Direct connect to Dig.Ground Plane



Bulgin Connector Layout:



DC Motor:

DC Motor w/Encoder: One motor is used for each of the 3 hot-wire arrays, rotating the probes horizontally.


Excel Spreadsheet to calculate pulse rates and angular resolution:

Motor Specifications Sheet



Interface Board Layout:

The layout was done without a schematic….due to simplicity ahem...  



When using the FETs, a pullup resistor is used to enable the output.   The data system must turn off the FET by pulling the lines low, floating lines will be pulled high.


MosFET IPS521: There are 3 uses of these FETs on the board.  First is turning on +12 power for the DC motor, Second is turning on +5 to toggle the direction of the relay for reversing the motor.  This is overkill because only 40mA is needed however, we have many of these parts on hand and they work well from logic levels.  Third is to turn on the +5 Vcc supply to the PhotoInterrupters all at once.


PhotoInterrupter: There are 3 IR optical switches for each motor.  Two used for the direction limits and a third for the stepping clock as the motor rotates the hotwire direction.


Reed Relay:  There is one reed relay used for switching each motor direction.


Bulgin Connector: Same connector used in NDAQ.


+5V Voltage Regulator: This SOT-223, 500mA, UA78M05 optional part is suggested provide +5 in lieu of the 5-volt provided by the Prometheus I/O connector.   Even though that signal is apparently tied directly to the main PC104 supply, the 7805 provides a backup capability if for some reason the current draw is more than provided via the Prometheus.  Digikey p/n = 296-12290-1-ND