Snack - Based Troubleshooting and Repair Guide
1670065 Page 12 of 54 September, 2002
Each Column line receives a signal from the control board. These lines are strobed 60 times per
second so that when column 1 is on, all other column lines are off. When column 1 turns off col-
umn 2 line turns on, and so on through each of the Column lines. When the last column line turns
off column 1 turns on again and the process is repeated.
The three Row lines are used to detect when a button has been pressed by sending the line low
(ground). The microcomputer sees the strobed signal from column line being fed back through
the low row line and determines which button has been pressed. For example, if the control board
observed the column line 3 strobe on the row 2 line it would be determined that the number 2 but-
ton had been pressed.
F. Motor Matrix
1. Since a matrix cannot directly control AC motors, the snack merchandiser uses 24 vdc
motors. For the matrix to work, both Row and Column signals are needed. In this case,
the Row controls the DC ground to the motor while the Column controls +24 vdc power.
2. The 5 wide snack is capable of handling up to 7 trays with 5 or 10 selections per tray or 4
to 8 selections per tray (depending on tray configuration). In addition, a 5 selection gum
and mint unit, and 5 additional selections (not presently used) are available for a total of
80 possible motors. The matrix consists of 5 Column lines and 16 Row lines.
a. In order for any motor to run, both Column and Row signals are needed. Candy trays
use 2 row lines for control. The motors are organized in terms of “odds” and “evens”.
The even numbered row is connected to all “even” numbered selections. For example,
Row A0 is connected to A0, A2, A4, A6, and A8. “Odd” numbered rows are con-
nected to “odd” selections. So Al is connected to A3, A5, A7, and A9. This system is
very effective with snack trays. A factory-built snack tray only uses 5 motors, but
rather than numbering the selections as 1 through 5 each snack selection uses an even
number (0, 2, 4, 6, and 8). This means that only a single (even) row line is necessary.
b. In standby, the Row lines will read approximately +12 vdc. When a motor runs, the
Row line goes to a ground (0 volts) level. For example, to run the motor for the A0
selection, Column 1 is energized, putting +24 vdc at all “0” and “1” selections. Row
A0 Even goes low, putting DC ground at even motors A0 through A4. Since motor A0
is the only one having both +24 vdc and ground applied, motor A0 runs. Note that A0
is the only motor in the entire matrix where Row A0 even and Column 1 meet, so it
is the only motor that can run. The entire motor matrix is set up so that only one
motor can possibly run when any pair of Row and Column lines are active.
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