
Reader - Voltage Requirements and Distance
iSTAR Ultra Installation and Configuration Guide
5–29
Reader - Voltage Requirements and Distance
To operate properly, each reader requires the following minimum voltage:
A standard RM Series Reader or RM-4 board requires at least
7.5
volts
.
An RM-4E board requires at least 11 volts
.
The iSTAR Ultra supplies 12 volts at its reader connectors; however, the amount of voltage
that reaches the reader is affected by the following:
Number of devices on the bus
Current draw of each device
Wiring length between the devices and iSTAR Ultra
Wire gauge that connects the devices
State of the battery (if running on apS)
Tolerance if sourced by an external power supply.
To determine the maximum distance of a reader from an iSTAR Ultra, calculate the voltage
that reaches each reader. If the voltage is insufficient, you can shorten the wire length, use a
heavier wire, or add UL294 power-limited power supply.
Wire resistance is as follows:
• 24 AWG = 26.0
per 1000 ft.
• 22 AWG = 16.5
per 1000 ft.
• 20 AWG = 10.2
per 1000 ft.
• 18 AWG = 6.5
per 1000 ft.
lists the general wiring requirements for an iSTAR Ultra and its
components.
NOTE
You must consider the wire length both to and from the reader, in the calculation.
Example:
The RM-4 is 500 feet away. (1000' round trip)
The RM-4 draws 250 mA. and is connected with 20 AWG wire.
The equation to calculate voltage drop is:
E= I*R
I = .25 A (250 mA)
R= 10.2 ohms (from the table)
E= .25 * 10.2
E= 2.55 (voltage drop)
12 Vdc - 2.55 Vdc = 9.45 Vdc
The connection meets the requirement.
Summary of Contents for tyco iSTAR Ultra
Page 8: ...Table of Contents viii iSTAR Ultra Installation and Configuration Guide...
Page 66: ...Visual Indicators 4 10 iSTAR Ultra Installation and Configuration Guide...
Page 98: ...Readers and Accessory Boards 5 32 iSTAR Ultra Installation and Configuration Guide...
Page 102: ...Overview 6 4 iSTAR Ultra Installation and Configuration Guide...
Page 110: ...Firmware Upgrades 7 8 iSTAR Ultra Installation and Configuration Guide...
Page 118: ...GCM Battery Replacement 8 8 iSTAR Ultra Installation and Configuration Guide...