Novanta v40, User Manual

Page: 52 / 104

CONTROLLING LASER POWER PAGE | 52
the UC-2000’s default Command signal frequency of 5 kHz has proven to work well. When considering
Command frequencies at 5 kHz or below, please review Marking/engraving operation later in this
section. For high-speed motion applications that cannot tolerate any ripple in the optical beam response,
but still need adjustable power levels, we recommend the use of higher PWM frequencies, up to 25 kHz
maximum. At 25 kHz, the laser’s optical beam response no longer follows the Command input and is very
nearly a DC value with just a small amount of ripple present.
Command signal
The modulated Command signal applied between Pin 9, PWM Input, and Pin 1, PWM Return, of the User
I/O connector on the v40 laser has three basic parameters: signal amplitude, base frequency, and PWM
duty cycle. By changing these parameters, you can command the beam to perform a variety of marking,
cutting, welding, or drilling operations.
The first Command signal parameter, signal amplitude, is either logic low—corresponding to laser beam
off, or logic high—corresponding to beam on. The laser off voltage, typically 0 V, can range from 0.0 V
to +0.8 VDC while the laser on voltage, typically 5 V, can range from +3.5 V to +6.7 VDC.
Base frequency, the second parameter, is the repetition rate of the PWM input signal. The standard base
frequency is 5 kHz, which has a period of 200 microseconds (
μ
s). Maximum PWM frequency is 25 kHz.
The third Command signal parameter, PWM duty cycle, is the percentage of the period that the Com-
mand signal is high. If the Command signal’s amplitude (at 5 kHz) is high for 100
μ
s and low for 100
μ
s, it
has a 50% duty cycle; if the amplitude is high for 190
μ
s and low for 10
μ
s, it has a 95% duty cycle. Figure
below illustrates PWM Command signal parameters while the following table lists PWM signal specifica-
tions.
Figure 4-4 PWM Command signal waveform
Warning: Serious Personal Injury
Always use shielded cable when connecting your PWM Command signal source to PWM Input / PWM
Return inputs. In electrically noisy environments, long lengths of unshielded wire act like an antenna
and may generate enough voltage to trigger uncommanded lasing.