37
Wiring
• Analog Inputs
– Potentiometer
– P 203 is Min – Max or –Max to +Max
– P 215 sets offset, may be negative
In the diagram to the left, parameters are indicated to show the relationship between
the signal coming from the pot and the reference. The signal from the pot is indicated on the
left of the graph. Notice that parameters 309 and 310 set the voltage range. Parameter 308
sets the function for this signal, in this case the reference.
On the bottom, the reference is indicated. Parameters 204, minimum (0Hz) and
parameter 205, maximum (60Hz) set the speeds if parameter 100 is set to Speed Open
Loop. In the diagram above the reference is indicated in %, which is one of the displays
readable from the LCP, Reference [%]. Notice that parameter 203 is set to Min – Max.
Parameter 214 is set to Sum and parameter 215 is set to 0%. This arrangement is used
frequently.
The pot however, can be setup to give a negative reference which causes the drive
to go in reverse if programmed correctly. Observe the graph to the right. It is not possible to
change the minimum reference, parameter 204 to a negative number, but a negative number
can be added to the minimum by using parameter 214 set for Sum and parameter 215 set to
–50%. This shifts the reference from 0 to 100% to –50 to +50%. Parameter 203 must be set
to –max to +max and parameter 200 must be set to Both Directions in order for this to work.
Now when 0Vdc comes in from the pot the reference goes to –50% and when the pot goes
to 10Vdc the reference goes to +50%. The maximum reference, parameter 205 must be
have a value that covers the complete range from –max to + max. Example: To make the
speed go from –50Hz to +50Hz and value of 100Hz must be placed in parameter 205.
When the voltage coming from pot reaches 5Vdc it might oscillate between forward
and reverse. Parameter 123 can be set to give a deadband around 5Vdc. In the example
above 3Hz might be selected, which means that the drive goes for 50Hz forward down to
3Hz, stops, the goes reverse from 3Hz back up to 50Hz.