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22. TROUBLESHOOTING
Situation Cause Countermeasure
Example 8
The load is
momentarily turned
ON when the external
supply power is
started up.
(Transistor output)
Incorrect output due to the floating capacitance (C)
between the collector and emitter of the
photocoupler
This does not affect normal loads, but in case
of highly sensitive loads (such as solid state
relays ), incorrect outputs may occur.
Photocoupler
(1) If the external supply power is suddenly started
up, current Ic flows due to the floating
capacitance (C) between the collector and
emitter of the photocoupler.
(2) Current Ic flows to the base of transistor Tr1 in
the next stage, and output Y0 turns ON for
about 500 s.
(1) After checking the external supply power takes
at least 10ms to start up when turned it ON/
OFF, set the switch SW1 at the primary side of
the external supply power.
(2) If setting the switch at the secondary side of the
external supply power is required, connect a
capacitor and resistor so that the start-up of the
power is slowly performed (Longer than 10ms).
Example:
R1 = 40 , C1 = 300 F
Calculate the time constant as follows:
R1: Several tens of ohms
Power capacity (External supply power current)
2*1
Resistive value (3 to 5)
*2
C1: Several hundreds of F, 50 mV
*1 For the current consumption of the external supply
power, refer to the manual attached to the module
to be used.
*2 Select the resistance for power capacity in the
range of between 3 and 5 times higher than the
actual power consumption.
C1 R1 = 300 10
-6
40
= 12 10
- 3
S
= 12ms
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