Wavetronix Click 500 (programmable controller) (CLK-500) - User Guide - Manual (Page 88)

CHAPTER 9 • CLICK 512 87
˽ The date is January 14, 2014
˽ The time is 8:58:45.849 p.m.
˽ The rest of the 0s differentiate the heartbeat string from an event string
The timing of when alert outputs are triggered is important to the application. For example,
motorists will need to see the warning message activate several seconds before they arrive
at the warning sign.
The following information gives an overview on different trigger methods that advise mo-
torists in a timely and effective way. There are three basic methods to synchronize this
trigger:
˽ Trigger at an ETA to the sign
˽ Trigger at a point upstream of the sign
˽ Trigger as soon as possible (ASAP)
Note
If you have an overspeed application that requires an immediate trigger, but does not
require lane resolution or vehicle-length resolution, consider using SmartSensor Ad-
vance with a Click 100 and Click 120. This system will have less than 100 ms of delay.
The ETA trigger method is recommended in order to provide a uniform experience for mo-
torists traveling at different speeds. With this method, drivers will see the sign turn on when
they are a specified number of seconds from reaching the sign. The sign can remain acti-
vated until they reach it, or it can be turned off before they reach the sign (if it is no longer
in their line of vision). This method can require a setback distance of several hundred feet
between the location of the SmartSensor HD unit and the warning sign. If the setback dis-
tance is smaller, you may consider the method which triggers activation as soon as possible.
Example
A warning sign system needs to be designed for a roadway where the maximum ve-
hicle length anticipated is 100-feet long and the maximum speed anticipated is 100
feet per second (almost 70 mph). The sign should activate when a driver is 2 seconds
from the sign and deactivate when a driver is 1 second from the sign. In this case, the
setback distance will need to be 400 feet (3 seconds at 100 feet per second pulse
100-foot vehicle length).