technical reference
314 Synrad Firestar ti-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-
fied 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 specifications.
Pin 2 Remote Reset/Start Request
Apply a positive or negative voltage (±5–24 VDC) with respect to Pin 11, Input Common, to
disable the laser. The laser remains disabled while voltage is applied to this pin. Removing voltage
from the Remote Reset/Start Request pin causes the laser’s RDY indicator to illuminate and
begins a five-second countdown after which lasing is enabled. Because all DC power is removed
from the laser’s RF board when this input is active, no lasing can occur until voltage is removed
from Pin 2. Refer to Table 3-4 for input circuit specifications.
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, first 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 five-second delay after which lasing is enabled.
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 pin must be connected to a
voltage source in the range of ±5–24 VDC. Refer to Figure 3-8 for a diagram showing how the
Remote Interlock input is factory-jumpered. Because all DC power is removed from the laser’s RF
board when this input is inactive, no lasing can occur until voltage is applied to Pin 3. Refer to
Table 3-4 for input circuit specifications.
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 five-second delay during which lasing is inhibited.
On OEM lasers, the Remote Interlock input is not latched. Re-applying a signal to Pin 3 enables
the RDY indicator and lasing is possible after the five-second delay, provided that the Shutter
Open Request signal is also present (SHT indicator illuminated).
Pin 9 PWM Input
Connect your PWM Command signal (+5 VDC, 5 kHz nominal, 25 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 specifications.
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