General description

The Thumbnail stimulator was originally conceived and built by Richard H. Gracely, PhD: National Institute of Dental and Craniofacial Research, NIH, Bethesda, Maryland, and Georgetown Chronic Pain and Fatigue Research Center, Georgetown University, Washington, DC.
Minor modifications were made to the pinching apparatus itself.  The most significant changes include the addition of sophisticated pressure regulation and  computer control with associated software.

2008 Version

This version came in two models:
  1. Manual.
  2. Voltage Controlled.

Thumb Pressure Stimulator   Voltage Controlled Unit   Thumb Stimullator Manual

Photos by Mike Young.

2009 Version

  1. Manual. (same as the 2008 version)
  2. Voltage Controlled. The pressure regulated used for the 2008 version are no longer available and the system is in the proccess of being redesigned. In addition to a new pressure regulator/controller, it will be equiped with a 3 way valve that will vent out any inlet air pressure in case of a power failure.
  3. Voltage Controlled with USB DAQ. Same unit as item 2 but with the addition of a USB LabJack Data Aquisition unit to be used with the UNC software.

2010 Version

2011 Version

Mechanical Device Fabrication

Original Solid PVC

(HTML document) (Rich Text File).

Clear PVC

(HTML document) (Rich Text File).

User Instructions & Part List for Pressure Controller

By Mike Young (HTML document) (Microsoft document) (Rich Text File document).         

Software Downloads

Software for UNC controller with LabJack USB data acquisition:
(contact us at to download this software)

Visual Basic EXE file: (October, 2006 version), and a newer not fully tested version.
Initialization Files:
Main: ThumbStimulator.ini
Graph: GraphDefaults.ini
Magnitude Estimation Device:
Messages: MagEstDefaults.ini
Sounds: SoundsDefaultsOGM.ini

Software Help

UNC software information and help (HTML File).
Parameter Table Help in HTML form.
Sample Defaults File (Text File)

Computer Interface


2008 Version

Original version(GIF file) with TTL, user switches and "Magnitude Estimation Device" inputs.
Stripped down version (monochrome bmp file)

2009 Version

Full version (monochrome bmp file) with power failure safety 3way N/O solenoid valve. Vents out the air in at first sign of power failure.
Stripped down version with DAQ (monochrome png file) with power failure safety, for the "Multi Stimuli" project.
Stripped down version without DAQ (monochrome bmp file).
Board layout and wiring information (50KB GIF file).


2008 version enclosure drawings (GIF file)
2009 version not yet available.

DAQ (LabJack U12)assignments

Analog Out 0 (AO0) = Pressure command (0 to 5 volt = 0 to 30 PSI plus an optional gain of 2 => 0 to 10 volt = 0 to 60 PSI)
Analog In 8 (AI0 & AI1 in differential mode) = Actual Pressure as read by the regulator .
Analog In 9 (AI2 & AI3 in differential mode) = Pressure command feed back (to check the gain setting of 1 or 2, and the accuracy of the DAC) .
User Switches:
D0 input = User Switch A latch
D1 output = User Switch A Reset
D2 input = User Switch B latch
D3 output = User Switch B Reset
Pain Magnitude Estimation Device Potentiometer type :
Analog In 10 (AI4 & AI5 in differential mode) = Estimated Magnitude In
D4 input = Switch #1
D5 input = Switch #2
Pain Magnitude Estimation Device Switch type :
IO1 input = Switch #1
IO2 input = Switch #2
IO3 input = Switch #3
TTL input:
D6 and IO0 as inputs.  

In Case of Problems

In Edit Mode?

The intent of the edit mode is to design and test parameter tables without the pressure controller being attached to the computer interface unit.
When in "Edit Mode", the pressure gage and information text background colors become beige (See a jpeg image of the front panel in edit mode).
To revert to "Normal Mode" go to the menu "Tools" then "Thumbnail Pressure" and click on "On".
The front panel gage and information text background colors should turn blue (as seen on this jpeg image).
Should the software experience difficulties finding the interface unit an error message will appear (as seen on this image).

Testing the Computer Interface Unit.

Prior to Jan. 2009.

Should the system behave totally erratically, we recommend unplugging the electronic pressure regulator from the back of the computer interface unit and install a test jumper from pin 1 to pin 2 of the jack. Great care must be taken not to jumper the wrong pins: shorting ground or the 15 vdc supply to any other pin could cause serious damage. The jack on the interface box is a 5 pin DIN connector identical to the old IBM keyboard connector, and because the original DIN connectors only had 3 pins, the 5 pin ones have what may seem to be a strange pin lay out. It goes 1 4 2 5 3 (pins 4 & 5 were added later between the other pins).  With this jumper replacing the regulator, the software and interface box can be tested without the fear of damage to the regulator. Future units will be equipped with a wrap test switch to make testing more convenient.
Starting Jan. 2009.
A jumper was added to the circuit board as an option to wrap the "command out" around to the "pressure feed back" / "Monitor" that normally comes from the pressure regulator (See schematics and jumper J7 location a 50KB GIF file).
  & Michael G Young

2005 December 16
last update 2013 February 11