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preliminary_fcc_lca-500_manual_en_896322_v200428_rev_3.docx
5.5
RS-485 Terminator Switches
Termination can be activated by flipping the termination switch to the “ON” position. This must be done if
the device is on either end of the bus. Most RS-485-buses require termination resistors across the conduc-
tor pair. The need for termination has to be checked for each installation. Especially for high data rates or
long cables, the resistors are absolutely necessary. Only the ends of the main cable require termination
resistors, additional resistors load the driver excessively. The resistor value matches the cable's differential-
mode characteristic impedance (100-120 Ohm). On the RS-485-bus you need a controller with fail-safe
biasing, meaning a pull-up and a pull-down resistor on the cable. The fail-safe biasing provides a known
state in case there is no active driver on the bus and therefore it is essential, independent from data rates
and length of the cable.
Controller
without termination resistor
B
A
Locator
Locator
Locator
120 Ohm
(with fail-safe biasing
incl. termination resistor)
with termination resistor
B
A
+5 V
130 Ohm
680 Ohm, 0.5 W
680 Ohm, 0.5 W
stubline max. 5 m (16 feet)
cable length max. 1200 m (4000 feet)
Example:
(680R+680R) || 130R = 119R
Technical data (for baud rates up to 115 kBaud):
Max. cable length:
1200m (4000 feet)
Recommendation
for the cable:
twisted pair, cable-cross-section at least 0,22mm² (AWG 24)
Differential-mode characteristic impedance 100-120 Ohm
6.
Signalization (Factory settings)
1) Yellow LED: Line voltage indicator
After connecting the power supply, the device shows that it is ready to operate by permanently activating
the yellow LED.
The yellow LED is off for 200ms, when a transponder has been read.
The yellow LED is off during configuration via DeisterConfig.
The yellow LED is off during a firmware update.
2) Green LED: Read indicator
The green LED activates after connecting the power supply during initialization phase.
The green LED is permanently off in operating mode.
The green LED is on for 200ms, when a transponder has been read.
The green LED is flashing during configuration via DeisterConfig.
3) Red LED: Status indicator
The red LED activates after connecting the power supply during the initialization phase.
The red LED is permanently off in operating mode.
The red LED is flashing during configuration via DeisterConfig.
The red LED is on during a firmware update.
