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Update to Data Acquisition System

A project log for The PVC Scanning Tunneling Microscope

An easy-to-build scanning tunneling microscope.

Tom EkkensTom Ekkens 01/15/2018 at 03:370 Comments

As the PCI connectors disappear from computers, the price on the National Instruments PCI-6229 card is beginning to fall. In January 2018, Ebay had several listings for sale in the range of $375. If a computer with a PCI connection is available, this now the preferred solution. In addition to the card, a way of connecting to the microscope is needed. A single $50 “12 foot Shielded VHDCI Male Cable” http://www.daqstuff.com/100768_vhdci_mm_cable.htm can be purchased and cut in half. Headers can be added to the following conductors and plugged straight into the STM. The wire color is correct for the 100768 cable only.

J2

Plug1

Wire Color

1

22 – X

Center bundle: White with pink stripe.

2

21 – Y

Tan with yellow stripe.

J5

Plug0

Wire Color

1

21 – Z

Tan with yellow stripe.

2

55 – Ground

Yellow with brown stripe (paired with 21).

3

68 - Tunnel Current Read

Purple with pink stripe.

4

34 – Tunnel Current Ground

Pink with purple stripe (paired with 68).

5

22 – Bias

Center bundle: White with red stripe.

BigEasy

Plug0 – Motor

Wire Color

GND

18: (D GND) Ground

White with blue stripe (paired with 52).

STEP

17: (P0.1) Motor step

Tan with brown stripe.

DIR

52: (P0.0) Motor direction

Blue with white stripe (paired with 18).

The connections are explained more fully in the electrical section of the build instructions. The only change between this list and the connections listed in the electrical section is that the digital ground for the stepper motor moves from pin 50 to pin 18. The reason for this change is that pin 50 is close to pin 52 on the connection box but pin 18 is twisted with 52 in the cable. This solution moves the total cost of the data acquisition system down to just over $400.

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