User guide

P/N: 021-00154, Rev. A.6 - updated for V4.7 Tools Page | 33
Analog inputs can be noisy or have abrupt voltage swings (i.e. joysticks). To help the application developer with
these problems the DVC5/7/10 support smoothing functions or ramps and noise filtering. Noise filtering is
effectively accomplished by the 10ms input sampling period of the DVC hardware and the deadband facility
provided. Ramps allow successive 10ms voltage measurements to be damped. For example, rather than
returning the percentage of the min/max range the raw voltage represents, the returned percentage value will be
determined by the ramp up/down rate over the min to max voltage range.
The purpose of ramps is to slow (damp) the voltage transitions as seen by the application program. Ramps are
especially useful for joystick control. If the joystick is moved abruptly in one direction or another the ramp
mechanism will effectively slow down the movement and enable the system to respond more gracefully.
Another joystick control filter is the deadband specification. When the analog voltage read from the joystick is in
the range of Center Volts – deadband to Center Volts + deadband the returned percentage value is 0. So if the
joystick moves slightly from the center it will have no effect on the system until it exceeds the deadband range.
Note: The ramp up or ramp down time used depends on the difference between the last two input voltage
samples within the min to max range. Ramp time between any change in input voltage is the product of the
User Selected Ramp Time and the difference between 0% to 100% of the User Selected Calibrated Voltage.
For example a 5 second ramp entered for an input calibrated to .1 to 4.5 Volts would return a 2.5 second ramp
with an instantiations voltage change between 1 Volt and 3.2 Volts.
The setting of the analog input characteristics is done using the DVC5/7/10 Programming Tool: Analog Input
window on the previous page. The configuration input fields are divided into logical sections. Some input fields
may be disabled depending on the boxes checked (i.e. Enable Center and Enable Ramps). First, give the input
a name that allows you to reference the specific input and its properties in your application. If the input has a
center, put a check in that box, and enter the direction names. When Enable Center is checked you must use
the Min Volts to Center Volts and Center Volts to Max Volts names in your application. If the analog input needs
voltage ramps, check that box. Calibrate the input with a voltage meter or the Program Loader Monitor and fill in
the Voltage Calibration Min, Max, and Center. Enter the Voltage limits and Reference limits. These values are
used to detect an open or short circuit condition or excessive voltage on the input. To set the voltage limits click
on the Auto Set Voltage Limits button. The Invert Output selection will make the program variable value equal
to 100% at MIN Volts and 0% at MAX Volts.
The following subsections give the definition as well as an overview of each of the fields in the Analog Input
screen:
Name
Variable name used in the application program to access this input’s value as a percentage of the voltage range
or true/false for a digital input and it’s associated properties.
Range: 16 Characters with no spaces. Valid characters are A-Z, a-z, 0-9, and "_".
Rules:
The first character cannot be a number.
Compiler keywords or other names already in use are not valid. A valid example is "Steering".
Min volts to Center volts
Name: Access word for the % of Center + Deadband to Min value
Range: 16 Characters with no spaces. Usable characters are A-Z, a-z, 0-9, and "_".
Rules:
The first character cannot be a number.
Compiler Keywords or other Names already in use are not valid. A valid example is "Steer_Left".
Ramp Down:
PWR COM