Chapter 12 Troubleshooting MASTER-K
12-10
(Continued)
Condition Cause Corrective Action
The load does
not turn OFF
• Sneak current due to the use of two
different power supplies
• E1 < E2 : sneak current
• E1 is switched Off and E2 is switched
ON : sneak current
• Use only one power supply
• Connect a sneak current prevention
diode(Figure below)
If the load is the relay, etc, connect a
counter-electromotive voltage
absorbing code as show by the dot
line
Off response
time of the load
is long
• Over current at Off state
[when a large current fluid load (L/R is
large) such as solenoid is directly driven
with the transistor output]
• The off response time can be delayed by
one or more second as some loads make
the current flow across the diode at th e off
time of the transistor output
• Insert a small L/R magnetic relay
and drive the load using the same
contact
Output
transistor is
destroyed
Surge current of the white lamp
A surge current of 10 times or more when
turned ON.
• To suppress the surge current make
the dark current of 1/3 to 1/5 rated
current flow
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