6.0 Functions of control units
6.1 Enable input or Stop/Start input
An input for interlocking with a supervisory systemm e.g. PLC or several controllers together, with a specific
relationship, e.g. paddle-switch regulation of a pre-feeder from a bowl feeder (see status output).
Inputs are usually configured for use with contacts or a 24 VDC signal. The controller runs when the contacts
are closed or 24 VDC is applied.
6.2 Status output
A contact or 24 VDC output signal to indicate if a feeder is on or off. The signal can be used to regulate
preceding or subsequent controllers, e.g. pre-feeder.
6.3 Soft start
When a feeder is turned on, the sudden thrust can cause components to be displaced or in extreme cases it
can cause the coil to hammer. To prevent this happenings the output voltage can be gradually ramped up.
The ramp up time is normally adjustable. This protects the feeder by providing a “soft start“.
6.4 Soft stop
To reduce the disturbance of components or material (in precision applications) a feeder can be slowly
ramped down to a stop. The ramp time is normally adjustable.
6.5 Coarse/fine control
To reduce overfilling when feeding material to a weighing machine, e.g. packing machines, a feeder can be
fun slower, shortly before reaching the target weight. Additional contacts are provided in a weigher for this
purpose. These contacts switch the controller to a second set-point level, which reduces the feeder through-
put. Upon reaching the target weight, the feeder switches off completely. This operating mode can be
selected in REOVIB digital controllers, as an alternative to using track control. The second set-point for “fine
feed“ is adjusted through the control panel. The sensor socket is used for the input signal.
6.6 Air valve output
Sometimes it is necessary, with troublesome components, to provide an air blast that will transfer product
from one feeder to another (e.g. from a bowl to a linear feeder). In such instances the air is only required
whilst a feeder is running. This output is configured so that the valve switches on one second before the
feeder starts and switches off four seconds after it stops.
6.7 Pulsed operation
A pulsed component flow is required for some applications, e.g. components that tangle or nest.
In digital controllers there is a function available and this has independently adjustable On/Off time settings.
See example below:-
8
1 s
4 s
Valvel
Feeder
1 s
Feeder
1,5 s
On
Off
