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General-purpose Relay: Indicator is Lit Slightly

FAQ No. FAQ02828

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Question

When LY2N General-purpose Relays are OFF, the indicator is lit slightly. What is the problem and countermeasure for this?

Answer

This problem may be the result of residual voltage caused by float capacitance in the wires or leakage current when Relays is OFF. This may also cause reset failure.
Check with the cable manufacturer for how much float capacitance the cables retain. Also check the amount of leakage current with connected sensor.

If needed, connect a bleeder resistor in parallel with Relays coil.

Example: Countermeasure against Leakage Current when Using Proximity Sensors and Relays

Connect the bleeder resistor and so that the leakage current that normally flows through the load (Relays coil) is by-passed.

AC RelayDC Relay
Bleeder resistance connection
Formula for calculating resistance
Place these values in the formulaP = Bleeder resistance W
(Actual value must be larger by a few multiples.)
Vs = Power supply voltage
I = Relay rated current (mA)iR = Proximity sensor leakage current
iOFF = Relay OFF current
Recommended Resistor Value
with Margin Not Calculated
Using the Formula
At 100 VAC
R = 10 KΩ max.
P = 3 W (5 W) min.
At 200 VAC
R = 20 KΩ max.
P = 10 W (20 W) min.
If heat generation becomes a problem,
use the value within the parentheses.
At 12 VDC
R = 15 KΩ max.
P = 450 mW min.
At 24 VDC
R = 30 KΩ max.
P = 0.1 W min.