Lg Electronics 120S User Manual

11-9 

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Possible troubles with various circuits and their corrective actions are explained. 

 

 

The followings describe possible troubles with input circuits, as well as corrective actions. 
 

Condition 

Cause 

Corrective Actions 

 

Input signal 

doesn’t turn off. 

Leakage current of external device 
(Such as a drive by non-contact switch) 

 

 

 

 

 Input signal 

doesn’t turn off. 

 (Neon lamp 

may be still on) 

Leakage current of external device 

(Drive by a limit switch with neon lamp) 

y

 Connect an appropriate register and capacity, 

which will make the voltage lower across the 

terminals of the input module. 

 

 

 

 

y

 CR values are determined by the leakage current 

value. 
− Recommended value C : 0.1 ~ 0.47 ㎌ 
    R: 47 ~ 120 

Ω (1/2W) 

Or make up another independent display circuit. 

 Input signal 

doesn’t turn off. 

Leakage current due to line capacity of wiring cable. 

y

 Locate the power supply on the external device 

side as shown below. 

 Input signal 

doesn’t turn off. 

Leakage current of external device (Drive by switch with 

LED indicator) 

 

y

 Connect an appropriate register, which will make 

the voltage higher than the OFF voltage across the 

input module terminal and common terminal. 

 Input signal 

doesn’t turn off. 

y

 Sneak current due to the use of two different power 

supplies. 

 

 

 
 

 

 

 
y

 E1 > E2, sneaked. 

y

 Use only one power supply. 

y

 Connect a sneak current prevention diode. 

DC 

input

L 

E1 E2 

C

External device 

AC 

input

 

R

Leakage current 

DC 

input

 

R 

E1

DC 

input

L

E

External device 

DC 

input

R 

Leakage current 

C 

AC 

input

R 

~

AC 

input

External device

~

External device 

AC 

input

Leakage current

~

C

External device 

AC 

input

R 

Leakage current 

~