T419S Indicator Service Manual 125
13.6.3 Outputs
There are a variety of interfaces for output control:
Relay Electro-mechanical switching device capable of switching multiple voltages or currents
Opto module Solid state switching device capable of switching multiple voltages or currents
Transistor Low voltage/low current switching device, typically not more than 5VDC or 100mA
You must determine, from the customer, the voltage and current that will be switched.
Be sure the indicator capabilities match the customer need.
Below is an example of output wiring.
Figure 13.1 Transistor output driving an external relay
Relays
There are many types of relays. Match the customer need to the relay types available.
Opto module
Opto modules are available in a variety of types. Make sure that the Opto in the machine is compatible with the customer’s voltage. There
are AC Optos, DC Optos and Optos with reed relay contacts. As well as Optos of various voltage ratings, they may be polarity dependent.
Transistor outputs
You must be cautions when you work with transistor outputs as they usually behave in either common emitter or common collector arrangements.
Transistor outputs usually switch low voltages and they are limited in voltage and current so you must not exceed their values. There may be a diode for back EMF protection (CR8 in the circuit shown in Figure 13.1) available. It is also possible that the 0 volts
line is not isolated. Transistor outputs would have difficulty operating in a circuit where they are expected to switch positive voltages.
Relay Power IN signal provides protection for the transistor circuit against power
supply spikes.
Relay
Relay
Voltage IN
Output #
1, 2, or 3
System Ground
External
DC Power Source
+5V to 40VDC
for output control
Indicator
Max Current
250 mA
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