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F3200 Installation & Programming Manual Document No: LT0122
Installation & Wiring
Page 8-22 5 July 2001 Issue 2.7
8.7 OPEN COLLECTOR WIRING
8.7.1 LED MIMIC DISPLAYS
It is expected that the most common use the open collector outputs will be to switch LEDs on
"mimic" displays. These outputs are approved for field connection, so may be used to
"drive" remote mimics. Typical connection is shown in Fig 8.7.1.
8.7.2 INTERFACING TO OTHER EQUIPMENT
Where the open collector outputs are used to switch inputs to other systems, such as an
Evacuation System or Plant Computer, there are two main options as follows:
1. Direct Coupling
The open collector output switches the equipment input to less than 1V (typically
0.6V at 1mA). E.g. it may be used to switch a 5V CMOS input, or monitored 5V, 12V
or 20V input. Refer to Fig 8.7.2.
Note that for this to work, the 0V supply of the equipment must be connected to the
0V supply of the FIP. This may not be desired, especially if the equipment has a
power supply connection to earth.
Note also that the open collector output has protection diodes to the FIP positive and
negative supplies and should not connected to inputs that could be "pulled" to a
voltage above or below these supplies, even with mains failed and battery voltage
low.
2. Isolated Coupling
The open collector output can be used to switch a relay, or an optocoupler as shown
in Fig 8.7.3. When the open collector is "on", the optocoupler transistor is also "on".
┌───┐
+VBF │ ├───────────────────────────────────────┬──────┬───────────────
└───┘ ┌┴┐ ┌┴┐
│ │ │ │ RESISTOR
└┬┘ └┬┘ E.G. 4K7
│ │
∇
∇
LED
┌───┐ │ │
OCn │ ├───────────────────────────────────────┘ │
└───┘ │
┌───┐ │
OCm │ ├──────────────────────────────────────────────┘
└───┘
FIG 8.7.1
EXAMPLE OF LED MIMIC WIRING