Continuum I/O System Reference
95
Switching Loads with Triacs
Although the Triac-based outputs of this module appear as relay contacts in the sche-
matics provided, they are actually solid-state switches that have limitations on the loads
they can switch.
AC vs. DC
The first limitation is that they cannot be used with DC loads.
A Triac switches AC only
.
Minimum Load Current
The second limitation involves the minimum load current.
In order for the Triac to
switch it must detect at least 30 ma of current from the load
. If your load is less than
30 ma you can induce the required load by connecting a resistor across the load (not
directly at the Triac!). Check the current draw specification on your field device, and if it
does not meet this minimum, add a resistor in parallel with the device being driven sized
to achieve the minimum loading. Use the following formulas to determine resistance and
wattage:
Resistance (ohms) =Voltage Power (Watts) = (Voltage)
2
Current Resistance
DO-6-TR
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