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7.11.4
Motor Drive
The second microcontroller on the RD-378 receives data from the CC-2000
communications chip, and generates the appropriate control waveforms for pan, tilt and
lens motors.
Connections
Connections for pan and tilt motors are made at PL16 and PL15 respectively. The motor
speed is varied using pulse-width modulation. The slowest speed generates a waveform
with mark space ratio of 1:9, whilst the maximum speed generates 10:0 (i.e. the DC level
of ±28V). A brake output is also provided to release the motor brakes as the motor drive
waveform starts, and to re-apply the brakes when a halt command is received.
The motor drive and brake outputs are protected with a current limit of 5A. Should a
current spike pass this threshold, the output drive will switch off until a new output is
generated from the motor drive processor. In addition re-settable fuses are used to
protect the output. These become open circuit after a few seconds if excess current (but
less than 5A) is drawn from either motor drive output. After a few seconds these fuses
automatically reset.
The zoom and focus drive is output from PL9. Speed is again controlled using pulse-
width modulation, and this time the output is current limited to 80mA.
Preset Connections
If the pan/tilt motors and lenses used are fitted with position pots, up to 100 preset views
can be programmed into the RD-378 site receiver. The board provides a 5V reference
that is output to the pan/tilt pots at PL12, and to the focus/zoom pots at PL14. The
return voltage is then dependant on the position of the associated pot, and is input at
PL11 for pan/tilt and PL13 for focus/zoom. The views are set and recalled from the
system keyboard.
Rev. C
7.11-5
HMXMU001018
10/06
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