Neurotechnology Research Systems
© Plexon Inc
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In current mode, there are additional delays associated with the current generation circuit and the
LED turning on. 300mA and 1000mA LEDs were tested at 100mA and their respective maximum
currents. The worst case observed time between the digital input and the light reaching 90% of its
maximum was 320µs. The rise time of the light output from 10% to 90% was up to 180µs, and the
fall time was up to 300µs. In general, rise times were actually shorter for higher currents.
Additionally, orange modules had shorter rise times than blue modules. Fall times were
approximately the same across different the current values for a given module. The blue modules
had longer fall times than orange ones. These delays are still small relative to the kinetics of the
opsins that are available at this time.
10.2
Synchronization of multiple Controllers
The Radiant GUI supports connecting up to four controllers to a single computer. It should be noted
that each controller has its own internal clock and this will result in slight timing variations
between Controllers. This variation will be most noticeable during very long stimulation protocols.
The crystal that generates the clock has 50 ppm stability. In the worst case, if your pattern is an
hour long, it could potentially finish 0.36 seconds earlier or later than the same pattern running on
a second controller that was started at the same time (assuming one clock is 50 ppm fast and one is
50 ppm slow). This is a worst-case scenario, but there will certainly be some drift between
different controllers.