© 2016 Littelfuse Protection Relays & Controls Rev: 1-A-062016
Flashers and Tower Lighting Controls
Flashers
www.littelfuse.com/fs491
FS491
Description
The FS491 is a low leakage AC flasher designed to control LED,
or resistive loads. This product offers a solid-state output and
may be ordered with an input voltage of 24V to 240VAC, in two
ranges. It offers a factory fixed flash rate of 75 FPM or may be
ordered with a fixed, custom flash rate ranging from 45 to 150
FPM. The FS491 is the perfect solution for LED lamp flashing.
Operation
Upon application of input voltage, the output energizes and
the ON time begins. At the end of the ON time, the output
de-energizes and the OFF time begins. At the end of the OFF
time, the output energizes and the cycle repeats as long as
input voltage is applied.
Reset: Removing input voltage resets the output and the
flash sequence.
Features & Benefits
FEATURES BENEFITS
Totally solid state
No moving parts to arc and wear out, up to 100
million operations under typical conditions
Fully encapsulated Protects circuitry from shock, vibration and humidity
Extremely low
leakage current
Ideal for use in LED lighting applications
Specifications
Technical Data
Operation ON/OFF solid-state flasher (continuous duty)
Flash Rate Fixed at 75 FPM ±20%
Custom Flash Rates 45 - 150 FPM ±20%
ON/OFF Ratio ≅ 50%
Input
Voltage 24, or 120 - 240VAC
Tolerance ± 15%
AC Line Frequency 50/60Hz
Output
Load Type LED or resistive
Output Bridge Rectifier & FET
Maximum Load Rating
120VAC to 240VAC 0.5A steady state; 5A inrush
Max. Load Leakage Current 250µA
Voltage Drop 2V typical
Mechanical
Mounting Surface mount with one #8 (M4 x 0.7) screw
Dimensions Dia. 23.9 mm (0.94”); D 38.1 mm (1.5”)
Protection
Surge IEEE C62.41 - 1991 Level A
Circuitry Encapsulated
Environmental
Operating/Storage
Temperature -20° to 60°C / -40° to 85°C
Humidity 95% relative, non-condensing
Weight ≅ 1.1 oz (31 g)
L1 N/L2
V = Voltage
L = Load
R = Red Wire
B = Black Wire
W = White Wire
Wiring Diagram
Function Diagram
ON time plus OFF time equals one
complete flash.
V = Voltage
R = Reset
L = Load
T1 = ON Time
T2 = OFF Time
T1 ≅ T2
