Spektrum AR7100 Series User Manual page 17

RevLimit Instructions (AR7100R only)
The Spektrum AR7100R features an integrated RevLimit limiter. The
RevLimit functions as a digital rpm limiter preventing the main rotor from
over-speeding. When the rotor speed is at or below the programmed
rpm, throttle position is controlled via the radio (i.e. throttle curves). The
RevLimit only engages when the rotor rpm exceeds the programmed rpm
reducing the throttle position preventing over-speed.
The RevLimit limiter is designed to limit engine speed between 9,500 and
20,500 rpm. Engine rpm = Rotor rpm * Main gear ratio
Servo Requirements
All common three-wire servos (analog and digital) are compatible and can
be used for the throttle servo. Note that two throttle channel outputs are
available: unregulated and regulated. The unregulated throttle operates at
the battery voltage. The regulated throttle is regulated to 5.2 volts and is
to be used when a high-voltage compatible servo is not being used for
throttle control.
Spektrum AR7100
Connections
The RevLimit is totally integrated and the target rpm is adjusted via the
Gear channel (channel 5). The only external connection needed is to
mount the backplate rpm sensor to the backplate of your engine using
two backplate screws. Note that the rpm sensor mount has two positions:
extended for .90-size engines and retracted for .50-size engines. When
installed correctly, the rpm sensor should just contact the backplate. On
some engines and specifically the YS .50 and .90, the sensors must be
spaced .5 to 1mm from the backplate. No additional magnets or brackets
are needed. The rpm sensor picks up the magnetic effect of the crankpin
as it passes the rpm sensor.
If your system is not limiting RPM in flight, re-position the sensor .5
to 1mm away from the backplate. This can be easily accomplished by
loosening the 2-56 button head screw on the sensor mount, re-adjusting
the position, and then tightening. This should resolve the issue.
Install the servos in their appropriately labeled ports. Note: The throttle
and gear channels have two outputs. Output 1 is unregulated and the
pack voltage is provided at this port. Throttle and Gear outputs 2 are
regulated to 5.2 volts when a throttle servo and gyro are used that are not
compatible with high voltage. (Most gyros require less than 6 volts.)
EN
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