Controller
Controllers are used for the precise current control (switching on and off) of LED lighting. Even small changes in voltage can increase the LED current and light emission so significantly that they can be destroyed in a very short time. It is therefore difficult to achieve precise lighting control via the power supply alone. A controller can be used to set an output current with an accuracy of 1 mA, independent of the voltage supply. The brightness of an LED is approximately proportional to the current.
An LED controller(LED driver) offers the following advantages:
– high light stability and performance,
– highly controlled,
– flexibly configurable,
– very efficient.
LEDs are briefly flashed using LED controllers with pulse function(flash control). Flash mode refers to lighting times of < 1 ms. Longer lighting times are referred to as switching or pulsed operation, which is equivalent to permanent operation in terms of current and power.
In flash mode, an LED can be overdriven, whereby it is briefly operated with a very high current. This over-flashing enables an increase in brightness of up to 10 times that of permanent or pulsed operation. In addition, the maximum irradiance of the LED is available within a few microseconds (short latency time). The maximum permissible flash current depends on several factors: Rated power in continuous operation, characteristic curve of the LEDs, pulse duration, total cycle time, operating temperature.
Overflashing has the following advantages:
– Reduction of the influence of ambient, extraneous or other interfering light,
– Increasing the LED service life,
– Synchronization between camera, lighting and the objects to be inspected,
– Reduction of motion blur,
– Reduction of electricity consumption and
– Minimization of heat generation.
In flash mode, synchronizing the image capture with the flash lighting is particularly important. The camera’s exposure time must be set longer than the flash duration, whereby the flash duration is the actual exposure time.
Controllers are triggered via fast opto-decoupled PLC and/or TTL switching inputs. Tolerances in trigger timing, delays, adjustable current ramps and the jittering of signals must be taken into account.
Controllers can already be integrated into the lighting or are available externally, e.g. integrated into the cable.
Controllers from Büchner Lichtsysteme can be found here.
