onto the power mains. Depending on the frequency and amplitude of these fields
they could result in failure to meet CENELEC conducted emission regulations.
If noise from parasitic coupling is suspected, it can be confirmed by inserting a 10cm
(4”) twisted wire pair in series with one of the inductors in question. If the conducted
noise spectrum varies by more than a few dB when this inductor is moved closer to,
and farther from, other components, then parasitic coupling may be the source of the
problem.
If stray coupling is a problem, regulations can usually be met by adjusting the
location or orientation of the radiating device relative to the coupling circuit
inductors. Alternately, shielded or toroidal inductors may be used to reduce coupling
as long as all electrical parameters specified in the example coupling circuit tables
given later in this chapter are met. If, however, a toroidal or shielded inductor is
used in place of L2, then the selected part must handle the maximum 1App output
current of the PLT-22 transceiver without approaching saturation. If L2 even
approaches saturation it can add harmonics of the PLT-22 transmit signal which
may result in failure to meet CENELEC emission regulations (in this instance, due
to inductor distortion instead of a stray pickup). For this reason, a shielded or
toroidal inductor used for L2 may need to have DC current rating two or three times
higher than listed in the example circuits given later in this chapter. The
recommended open frame axial inductor does not need this extra operating margin
due to the linearity provided by its magnetic path being partly in air.
Safety Issues
This guide is intended only as an introduction to some of the safety issues associated
with designing circuits using the PLT-22 transceiver. This document is not a primer
on electrical safety or electrical codes, and it is the responsibility of the user to
familiarize himself or herself with any applicable safety rules or regulations. A
review of all designs by competent safety consultants and the pertinent regulatory or
safety agencies is strongly recommended.
Safety Isolation Considerations
Many products include an isolation barrier in the form of an insulated enclosure
between a user and any hazardous conductors. A typical product of this type is a
light switch in which the PLT-22 transceiver and all of the associated electrical
components are contained inside the switch enclosure. The type of coupling circuit
that can be used in these applications is called a
non-isolated coupling circuit
. A
non-isolated coupling circuit generally requires lower cost components, making it
especially desirable for use in price-sensitive consumer products and wiring devices.
All of the coupling circuit examples that have been shown so far are of the non-
isolated type.
Some products cannot practically incorporate an enclosed isolation barrier and an
alternate method of safety isolation must then be provided. For example, a circuit board
that uses a PLT-22 transceiver, a non-isolated line-to-neutral coupling circuit, and a
Neuron Chip whose I/O pins are user-accessible presents a potential electrical shock
L
ON
W
ORKS
PLT-22 Transceiver User’s Guide
4-11
Summary of Contents for LONWORKS PLT-22
Page 6: ...iv Echelon...
Page 14: ...1 8 Introduction...
Page 67: ...LONWORKS PLT 22 Transceiver s User Guide 5 7 Figure 5 3 Capacitor Input Power Supply Schematic...
Page 92: ...6 10 Design and Test for Electromagnetic Compatibility...
Page 110: ...7 18 Communication Performance Verification...
Page 114: ...8 4 References...
Page 118: ...A 4 Appendix A...
