1 – 4
Getting Started
Note: The shutter “logic” power supply (at
+
4.5 VDC) is always
provided to each connected shutter when the SR474 is powered on,
whether or not the channel is enabled. This is a separate power
supply from the
+
12 VDC line that provides power to the motor
(coil) in an attached shutter head.
When a channel of the SR474 is in the
OFF
state, a shutter head con-
nected to that channel is said to be in
Standby
mode. In this mode,
the logic power supply provides power for serial communications,
but the
+
12 VDC power supply is not available to change the po-
sition of the shutter blade. The shutter blade position is therefore
indeterminate.
1.2.1.3 Source key
The
Source
key for channel
n
selects the mode of control for a
shutter head connected to the channel
n
output.
Two of the indicators by the key,
TTL
and
Manual
, are mutually
exclusive and indicate which of the two possible control modes is
selected for the shutter. Pressing the
Source
key will toggle between
these two modes.
In the
Manual
source mode, the state of the shutter is controlled to
be open or closed by direct user input, as selected by the
State
key
and its indicators (
§
1.2.1.1).
In the
TTL
source mode, the state of the shutter is controlled by the
level of the rear-panel TTL input for that channel. When the rear-
panel TTL input is high (unasserted), the shutter is commanded to
be in the
Normal
state. When the TTL input is low (asserted), the
shutter is commanded to be in the
Normal
state.
The polarity of each shutter channel is either
normally open
or
nor-
mally closed
as determined by the configuration of the rear-panel
DIP switches (
§
1.3.7).
The third indicator near the
Source
key is the
Remote
indicator.
This indicates when the instrument is addressed over a remote in-
terface. The channel is then in the
Remote
mode. Local control of
the channel can be re-established by pressing the
Source
key. The
mode can also be cleared for all channels at once by pressing the
Local
key in the lower left hand coner of the front panel. See also
§
1.2.3 for more about remote and lockout modes.
1.2.1.4 Align key
The
Align
key for each channel enables an alignment mode, where
the shutter is commanded to chop (open and close) at a rate of ap-
SR474 Four Channel Shutter Driver