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Data Acquisition Project

Information and Data was submitted to Parallax by Mark Johnson:

The Granular Science Laboratory at NJIT (New Jersey Institute of Technology) in Newark, NJ needed to collect data for an experiment. A Data Acquisition System was developed to feed and drop small balls (3mm OD) of various metals (brass, steel and aluminum) onto a Galton’s Board using a pair of microprocessor (PIC16F84) controlled solenoids. The solenoids were activated by a TTL signal from a manual start switch. Omron Infrared photo eyes were used to detect the balls entering and exiting the board. The PIC also controlled a servo which agitated the balls housed in a storage hopper and started/stopped an LED timer. Balls were dropped manually, 1 ball at a time. Data was collected manually as the balls exited the board (50 possible cells), the cell number and time were hand written in a log book. This MANUAL MODE made up the initial phase of the Data Acquisition System and collected ~ 200 data points per day.

The lab required many more data points than had been collected manually. A BASIC Stamp® 2 network was added to the system above to automate the ball drops and automatically log data. The 50 cells were fitted with cell detector switches made up of an IR LED which directed light vertically through the cell to an IR collector. The active low TTL signals from the collectors were used as BS2 inputs. The 50 cell detectors were wired to 4 ‘DETECTOR’ BS2’s and communicated using SEROUT w\flow control to a ‘MASTER’ BS2. The existing Red Lion timer would not interface with a microprocessor directly so a separate timing device was also added (11 frequency clock kit from Peter H. Anderson). The Red Lion timer and the frequency clock kit are within ~2ms of each other.

Download the Source Code for:
Detector 1
Detector 2
Detector 3
Detector 4
Master

The ‘Master’ Would:
  1. Trigger a ball drop by toggling the TTL drop signal to the PIC listed above
  2. Start and stop the new timer by toggling the enable bit
  3. Count the pulses from the timer using COUNT
  4. Receive the cell number from the ‘DETECTORS’ using SERIN
  5. Write the data to a message file using debug (Stamp Plot Lite)

The ‘Detector’ Would:

  1. Scan for active low cell detection
  2. Send the cell number to the ‘MASTER’ using SEROUT

‘Ball Drop’ PIC Accepts Input for:

  1. Manual start (through a 2 position slide switch) from a hand triggered release switch for manually dropping balls.
  2. Auto start (through a 2 position slide switch) from the BS2 Master for automatic ball release operation.
  3. Timer start from a start photo eye located at the point of  release.
  4. Timer stop from a stop photo eye located at the point of exit.
  5. Fill tube empty/full from fill tube photo eye.

'Ball Drop’ PIC Controls Output for:

  1. Reset Red Lion time display.
  2. Activate release solenoid and load solenoid.
  3. Starting Red Lion time display.
  4. Stopping Red Lion time display.
  5. Hopper servo control.

Automatic Mode Components

Timer Components-

(1) ‘Auto Mode Timer’ PIC16F84 used to provide an accurate time input to the BS2 Master. (In Auto mode the Red Lion display is used for information purposes only).

‘Auto Mode Timer’ PIC accepts input for:

  1. Timer start from BASIC Stamp 2 module ‘Master’.
     

‘Auto Mode Timer’ PIC controls output for:

  1. Accurate millisecond resolution time base to BASIC Stamp 2 module ‘Master’.

(4) BS2 ‘Detector’ used for cell detection. Transmit serially on BASIC Stamp network as Clients. ‘Detectors’ use 14 I/O pins to detect ball drops and 2 I/O pins to transmit the cell id number to the ‘Master’ using SEROUT w/flow control.

BS2 ‘Detector’ accepts input for:

  1. Individual cell detection from cell photo eyes.

BS2 ‘Detector’ controls output for:

  1. Transmits cell id number to ‘Master’ using SEROUT w/flow control.

(1) BS 2 ‘Master’ used to control Auto mode functions and collect and transmit time and cell data to a PC file using Stamp Plot (debug).

BS2 ‘Master’ accepts input for:

  1. Timer start from a start photo eye located at the point of release.
  2. Timer stop from a stop photo eye located at the point of exit
  3. Cell id number transmitted serially over Basic Stamp network from ‘Detector’.
  4. Ball drop time from ‘Auto Mode Timer’ PIC16F84 using COUNT.

BS2 ‘Master’ controls output for:

  1. Starting ‘Auto Mode Timer’ PIC16F84.
  2. Stopping ‘Auto Mode Timer’ PIC16F84.
  3. Activating ‘Ball Drop’ PIC16F84.
  4. Transmit cell id number and ball drop time to PC file using Stamp Plot (debug).
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