Red Lion GEMINI 2 - Manual (Page 16)

DUAL PRESET COUNTING & PROGRAMMING APPLICATION EXAMPLE
A typical industrial application for Gemini 2000 will require both a slow down
output and a final stop output. The Gemini can easily be programmed to solve this
requirement. For instance, let’s look at a textile web process that requires a dual
output as the web progresses to the proper length. A typical length of material for
this application is 10,000 feet for total length, and a slow down output 500 feet
prior to the end of the 10,000 foot length. In this case, it would be best to set the
unit up as Manual Reset to Preset 2. Preset 2 would be set at 10,000, and Preset 1
would be set for 500. The counter would count down to 500, and output 1 would
activate and cause the process to slow down until 0 is reached at which point
Output 2 would activate and latch for final stop. The advantage of using manual
Reset to Preset 2 is that when changing the total length it is only necessary to
change Preset 2 (length). Preset 1 (slow down) would remain the same, assuming
the same amount of slow down is required.
The accompanying drawing shows an LMPC sensing a 60 tooth gear which is
attached to a 2.5 ft. circumference drum. Since the unit of measure is a foot, the
first step is to find the number of pulses per foot that will be used. The following
formula is used.
Pulses/ft. = 60 pulses/rev. = 24 pulses/ft.
2.5 ft./rev.
Since the desired readout is in feet, and there are 24 pulses per foot, it is
necessary to scale the count. To determine the multiplier that is needed, the
formula below is used.
K =
“desired reading”
=
1
=
0.0416667
“# of pulses” 24
To get the maximum amount of decimal point accuracy a scale multiplier of
0.01 (divide by 100) is used which would give us a scale factor (rounded off) of
4.1667. If we used the multiplier as the scale factor, and used a scale multiplier of
1, the scale factor would round off to 0.0417, in which case 2 decimal places of
accuracy would be lost.
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