technical reference
315
Synrad Firestar f-Series operator’s manual
User I/O connections
Input signals
A total of four user inputs allow control of Firestar lasers. Remote Interlock, Shutter Open Request, and
Remote Reset/Start Request inputs are optoisolated and bi-directional, allowing for positive or negative
polarity signal inputs. These three signals also share a common return connection, Input Common, which
is separate from chassis ground to completely isolate control signals for optimal EMI performance. The
fourth input, PWM Input, is optoisolated and has a separate return, PWM Return, to fully isolate PWM
signals from the other three user inputs. Note that throughout this manual, input voltage levels are speci-
ed with respect to their corresponding return line.
Pin 1 PWM Return
Connect the return side of your PWM Command signal to this pin. Refer to Table 3-4 for input
circuit specications.
Pin 2 Remote Reset/Start Request
Apply a positive or negative voltage (±5–24 VDC) with respect to Pin 11, Input Common, to re-
set or remote keyswitch the laser. The laser remains disabled while voltage is applied to this input.
Removing voltage from the Remote Reset/Start Request input causes the laser’s Ready lamp
to illuminate and begins a ve-second countdown after which lasing is enabled. Because all DC
power is removed from the laser’s RF driver when this input is active, no lasing can occur until
voltage is removed from Pin 2. Refer to Table 3-4 for input circuit specications.
For Keyswitch-equipped lasers in automated systems, the Remote Reset/Start Request input
can operate as a remote keyswitch. To use this “remote keyswitch” functionality, rst place the
Keyswitch in the ON position. Then after each DC power-up cycle (or to reset a fault condition),
apply a momentary voltage pulse in the range of ±5–24 VDC to Pin 2. This reset action initiates
a ve-second delay after which lasing is enabled. To prevent operator injury when using Key-
switch-equipped lasers, the Remote Reset/Start Request signal is ignored when the Keyswitch is
set to the OFF/RESET position. The manually-operated Keyswitch must be set to the ON position
before the laser can be reset from a remote location.
Pin 3 Remote Interlock
Apply a positive or negative voltage (±5–24 VDC) with respect to Pin 11, Input Common, to
enable lasing. If your system does not use a remote interlock, this input must be connected to a
voltage source in the range of ±5–24 VDC. Refer to Figure 3-7 for a diagram showing how the
Remote Interlock input is factory-jumpered on the Quick Start Plug. Because all DC power is
removed from the laser’s RF driver when this input is inactive, no lasing can occur until voltage is
applied to Pin 3. Refer to Table 3-4 for input circuit specications.
After voltage is removed and then re-applied to the Remote Interlock input on Keyswitch-
equipped lasers, the Keyswitch or the Remote Reset/Start Request input must be toggled to
restart the laser This action initiates a ve-second delay during which lasing is inhibited.
On OEM lasers, the Remote Interlock input is not latched. Re-applying a voltage to Pin 3
enables the Ready indicator and lasing is possible after the ve-second delay, provided that the
Shutter Open Request signal is also present (Shutter indicator illuminated).
Pin 9 PWM Input
Connect your PWM Command signal (+5 VDC, 5 kHz nominal, 100 kHz max) to Pin 9. This
pulse width modulated Command signal controls laser output so that a duty cycle of 50% cor-
responds to a laser output of approximately one-half rated output power and a duty cycle of 95%
corresponds to approximately full output power. Refer to Controlling laser power in this chapter
for further information on laser control signals. Connect the PWM signal source return to Pin 1,
PWM Return. See Table 3-4 for input circuit specications.
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