Mitsubishi Electric MELSEC Q Series User Manual page 24

(b) At momentary power failure of remote I/O modules
If momentary power failure occurs in the power supplied to remote I/O modules (24VDC), incorrect input may
occur.
Remote I/O module
(Module power supply and
input external power supply)
Remote I/O module
(Inside: 5VDC)
Input (Xn)
22
Downloaded from ManualsNet.com
• Cause
The hardware of a remote I/O module internally converts 24VDC (module power supply) into 5VDC.
If momentary power failure occurs in a remote I/O module, (Time until the internal power of the remote I/O
module (5VDC) turns off) > (Time until the input module turns off) is met.
Therefore, if data are refreshed within the time shown in 1) in the figure below, incorrect input may occur
(This situation especially occurs when the input response time is set to high-speed response).
• Measures against incorrect input
Use the same power supply for a power supply module, stabilized power supply, and input external power
supply (AC input).
DC input
TO
Stabilized
power supply
Stabilized
power supply
AC input
TO
Stabilized
power supply
search engine
When the input external power
supply is turned off, the input (Xn)
turns off after the input module
turns off.
CPU
module
Power supply
24VDC
adapter
24VDC
CPU
module
Power supply
24VDC
adapter
1)
When the input external power
supply is turned on, the input (Xn)
turns on after the input module
turns on.
Remote I/O module
Input external
power supply
Remote I/O module
Input external
power supply