4
General Description
The PP420 current controller provides repeatable intensity control of LED lighting for machine
vision applications. It includes the power supply, intensity control, timing and triggering
functions required for machine vision systems.
LED lighting needs a constant current supply as small variations in voltage can cause large
variations in light output. Currents can be specified in 2.5mA steps to give very fine control of
intensity.
Three modes of operation are provided separately for each channel:
Continuous
In continuous mode the output is a continuous current.
Pulse (Strobe)
In this mode output is pulsed once per trigger. One trigger input is used as a trigger. The
delay and pulse duration can range from 20us to 1 second in 20us.
Switched
In switched mode a trigger input can be used to switch the output current on and off. The
output is only enabled when the input has a voltage on it.
Configurations are saved in non-volatile memory so that the PP420 will resume operation after a
power cycle.
The PP420 is set up using the push buttons and display on the front of the unit or using Ethernet
commands. The set up is non-volatile, so the PP420 will resume the same operation after a power
cycle.
4.1
Default Configuration
When shipped the PP420 has the following configuration:
Ethernet set to DHCP mode
Each channel set to 0.1A rating, no autosense, continuous output at 50%
4.2
Automatic Light Sensing
When a channel does not have a light connected, the PP420 continually tries to put out a very
small current. Each channel operates independently.
When a light is connected, it will flash for a short time (the light will not be damaged by this)
until the PP420 detects that it is connected.
If the AUTO_SENSE flag is set or a current rating has not been entered for this channel then the
PP420 will wait for the current rating to be set. This flag can be set using the Configuration