technical reference
38
Synrad Firestar f-Series operator’s manual
Controlling laser power
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 µs and low for 100 µs, it
has a 50% duty cycle; if the amplitude is high for 190 µs and low for 10 µs, it has a 95% duty cycle. Figure
3-4 illustrates PWM Command signal parameters while Table 3-2 lists PWM signal specications.
VDC
VDC
100 µs
190 µs
5 kHz Command Signal at 50% Duty Cycle
5 kHz Command Signal at 95% Duty Cycle
Figure 3-4 PWM Command signal waveform
Firestar’s User I/O PWM input consists of a high-speed optoisolator LED with a forward voltage drop (Vf)
of 1.5 VDC. The PWM input frequency can range from DC (0 Hz) to 100 kHz. Table 3-2 provides mini-
mum, maximum, and nominal PWM signal specications.
Table 3-2 PWM Command signal specications
Laser State Minimum Nominal Maximum
Laser O 0.0 VDC 0.0 VDC +0.8 VDC
Laser On +3.5 VDC (3 mA) +5.0 VDC (6 mA) +6.7 VDC (10 mA), continuous
Frequency Range 0 Hz (DC) 5 kHz 100 kHz
Duty Cycle 0% — — 100%
Operating modes
External control
In addition to controlling the Firestar laser using a UC-2000 Controller, control of Firestar externally,
without a UC-2000, is also possible. The two primary elements of laser control are gating, the ability to
turn the laser on and o at the appropriate times, and power, the ability to control the laser’s output en-
ergy. Both gating and power can be handled by a device such as a personal computer, Programmable Logic
Controller (PLC), or function generator capable of sending PWM pulses at the proper time (gating) and
with the proper duty cycle (power).
Analog voltage or current control
Although Firestar f-Series lasers cannot be controlled directly by analog voltage or current signals, this
type of control is possible when using the UC-2000 Controller. The Controller is connected normally to
the laser and analog voltage or current signals sent to the UC-2000’s ANV/C connector then control both
laser gating and power.
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