• The
Gated
trigger mode is active as long as there is a high TTL signal (4 V or more) on the input modu-
lation BNC. This signal comes from a different light source or device driver. When the TTL signal is low
(0.4 V or less), the sequence stops and waits for another high TTL signal to continue.
• If the
TTL Output
option is checked, the output BNC channel can be used as a TTL generator. The mon-
itoring signal will provide a TTL signal instead of an analog voltage output proportional to the LED cur-
rent. The output will send out a 5 V signal whenever the input current is
>
0 mA. This can be used even if
a light source is not connected.
3. The
Sequence options
box (Fig.
) is where sequence options are defined depending on the mode. The
Contin-
uous wave, External TTL
and
External Analog
modes have no additional sequence options.
Figure 3.3:
Constant Current Mode Driver Signal
a) The
Continuous Wave
mode (Fig.
) produces a continuous signal at the chosen current. This mode can
only be triggered manually. When this mode is active, the driver channel will show
CW
under
MODE
. This
mode has no additional sequence options.
Figure 3.4:
Driver Signal Response to External Source in External TTL Mode
b) The
External TTL
mode (Fig.
) has the light source follow a TTL signal provided by an external source
connected to the
BNC Input
. When this mode is active, the driver channel will show
TTL
under
MODE
. This
mode has no additional sequence options.
c) The
External Analog
mode (Fig.
) is similar to the External TTL, except that the current will be set by the
voltage on the BNC input (Fig.
, top). On the input BNC, a maximum voltage signal corresponds to a max-
imum driver current. Should the current set on the light source be less than the maximum current, any volt-
age corresponding to a higher current will clip the output waveform (Fig.
, bottom). To avoid any clipping
of the output waveform, the maximum current setting must be equal to or greater than the corresponding
maximum analog input voltage. See the corresponding light source manual to find the voltage/current rela-
tionship. This mode has no additional sequence options.
Chapter 3. Doric Neuroscience Studio
12
