National Instruments NI myRIO, Справочник по основам

Страница: 70 / 163

64 CHAPTER 8. COIN COUNTER
that contains these four elements (see Create “Coin Info” Cluster Array
18
),
and then create a data highway lane for this control. Create another lane
as an array of corresponding known coin diameters. Define these values
as constants in the
(qsm) initialize state.
•
Create a subVI to produce the coin info record that is closest to the mea-
sured coin radius; remember to multiply the radius by two and to account
for the calibration scale factor. Calculate the distance between the mea-
sured diameter and all of the known coin diameters (subtract the array of
known diameters from the measured diameter and then take the absolute
value) and then use the Array Max & Min function to find the array index
of the minimum distance.
T
IP
:
Use the “Quick Drop” shortcut (Ctrl + space bar) to look up
and place a LabVIEW element by name. See Appendix C on page 139
for more LabVIEW tips.
• Create a calculate value state to sum the individual coin values with a for-
loop structure auto-indexed by the “Circles Data” array to step through
each of the detected coins. Edit the
(image) overlay state to add a similar
for-loop structure to create text labels to be placed at the center of each
coin; see
Overlay Text at X-Y Coordinates
19
and Adjust Overlay Text
Alignment
20
.
8.3 Validation Tips
Evaluate the performance of your completed application, especially these use
cases:
•
No coins in view,
• One coin moved to various locations – confirm that the coin is always
classified properly,
• One sample each for all four classes – confirm that the total value dis-
played is correct,
•
Maximum number of coins in view, various number of samples of each
class – again, confirm that the total value is correct, and
18
http://youtu.be/Yqv4u5FE8Vk
(5:12)
19
http://youtu.be/O5IIrPP_smA
(1:41)
20
http://youtu.be/rsI7fco5n_g
(2:47)