Manual 26166V1 MicroNet Simplex & MicroNet Plus
Woodward 99
8.4.4—Troubleshooting
Fault Detection (Module Hardware)
Each 48Ch DI module has a red Fault LED that is turned on when the system is reset. During initialization
of a 48Ch DI module, which occurs after every CPU module reset, the CPU turns the Fault LED on. The
CPU module via the VME bus turns off the Fault LED when the CPU has started execution of the
application program and verified that the board is present.
Figure 8-15. Discrete Input Module Block Diagram
Figure 8-25 is a block diagram of the Discrete Input module. The module receives information from as
many as 48 field switches and relays. Field wiring is isolated from the MicroNet circuitry by optical
isolators in each channel; the state of each discrete input is passed through an optoisolator to the buffers.
The CPU then obtains the data for each channel through the VME interface.
If during normal control operation all of a chassis’ 48 DI modules have Fault LEDs on, check the chassis’
CPU module for a failure.
If a discrete input is not functioning properly, verify the following:
1. Measure the input voltage on the terminal block of the FTM. It should be in the range of 16–32 Vdc.
2. Check the wiring. If the inputs are reading open, look for a loose connection on the terminal blocks,
disconnected or misconnected cables, or a missing jumper on the terminal block.
3. Check the application software configuration to ensure that the input is configured properly.
4. If the other channels on the 48 DI module are not working either, check the fuse on the 48 DI
module. See the instructions in Chapter 15 for replacing the module. This fuse is visible and can be
changed through the bottom of the module. If this fuse is blown, fix the wiring problem and replace
the fuse with another fuse of the same type and rating.
5. After verifying all of the above, exchange the J1 and J2 cables. If the problem moves to a different
channel, replace the cable. If not, replace the 48 DI module.
6. If replacing the module does not fix the problem, replace the FTM. See the instructions in Chapter 15
for replacing the FTM.
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