NI 9758 Manual
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© National Instruments
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7
Figure 5.
Connecting Port Fuel Injectors to the Driver Module
Note
A CompactRIO controller may be powered by the same power source or by
an isolated power source. If the Compact RIO controller is powered by the same
battery used for cranking the engine, then it is possible that the battery voltage
will drop below 9 V during cranking, causing the CompactRIO controller to reset.
This can be prevented by using a small backup battery and a diode pack for the
CompactRIO controller. Visit
ni.com/info
and enter Info Code
PFI
for
recommended parts and connections for the NI 9758.
Low-Side Drivers
The low-side drivers are capable of driving a wide variety of automotive relays and actuators.
Examples of actuators include EGR valves, turbo wastegate valves, fuel pressure regulators, or
any single-solenoid-actuator which draws less than 1.2 A at the highest expected battery voltage.
Caution
Do not attempt to drive low impedance injectors or solenoids with the
general purpose low-side drivers. The low-side drivers are only rated for 1.2 A
continuous. Higher current levels could damage the low-side drivers.
Each channel is independently controlled within the module via pulse-width modulation
(PWM). PWM duty cycle from 0% to 100% is possible. Software on the RIO FPGA device
communicates several parameters for each channel to operate. Those parameters are Enable,
Period and PulseWidth. All parameters are communicated serially at 200 µs intervals. Each
PWM controller utilizes a 20-bit timer operating at 2 MHz. This provides a resolution of 500 ns
and a minimum PWM frequency of 2 Hz. Since 0% and 100% duty cycles are possible, relays
and actuators may be controlled in continuous on or off states.
