CENELEC Access Protocol
To allow multiple power line signaling devices from different manufacturers to
operate on a common AC mains circuit, the CENELEC standard EN 50065-1
specifies an access protocol for the C-band (125kHz to 140kHz). The frequency
132.5kHz is designated as the primary band-in-use frequency that indicates when a
transmission is in progress.
Every power line signaling device must both monitor the 132.5kHz band-in-use
frequency and be able to detect the presence of a signal of at least 80dBµVrms
anywhere in the range from 131.5kHz to 133.5kHz which has a duration greater
than or equal to 4 milliseconds. A power line signaling device is permitted to
transmit if the band-in-use detector shows the band to have been free for at least 85
milliseconds. Each device must randomly choose an interval for transmission, and at
least seven evenly distributed intervals must be available for selection. A group of
power line signaling devices is allowed to transmit continually for a period less than
or equal to one second, after which it must cease transmitting for at least 125
milliseconds.
The PLT-22 transceiver incorporates the CENELEC access protocol and the user can
enable or disable the CENELEC access protocol at the time of channel definition.
When enabled, the PLT-22 transceiver enforces the CENELEC access protocol while
still maintaining the benefits of the LonTalk protocol. When the CENELEC access
protocol is enabled, overall network throughput is reduced by 11%.
Power Management
The PLT-22 transceiver incorporates a power management feature that supports the
design of very low cost power supplies in low cost consumer applications such as
networked light dimmers, switches, and household appliances. This class of
consumer applications have low transmit duty cycle operation requirements. These
low cost power supplies take advantage of a number of PLT-22 features: the low
receive current requirements of the PLT-22 transceiver; the 9:1 difference between
the PLT-22 transceiver transmit and receive mode currents and the wide (+8.5VDC
to +16VDC) V
A
operating voltage of the PLT-22 transceiver.
A low transmit duty cycle implies that the device transmits packets infrequently,
e.g., the product waits for a minimum of 10 packet times between transmitting each
packet - a 10% transmit duty cycle. A power supply design that takes advantage of
this duty cycle can store energy on a capacitor during the relatively long period
between transmissions, when the PLT-22 transceiver draws minimal current, and
then consume the stored energy to transmit a packet. This type of power supply,
referred to as an “energy storage power supply,” stores energy by charging an energy
storage capacitor to a relatively high voltage (e.g., 15V) while in receive mode. The
voltage on the capacitor then falls or "droops" toward a lower limit (e.g., 9.0V) while
transmitting. The energy storage capacitor is then slowly recharged to the higher
voltage during the relatively long time between transmissions. Traditionally, the
proper design of such a power supply required knowledge of the maximum transmit
duty cycle to be supported, and an implementation that accounted for all worst case
L
ON
W
ORKS
PLT-22 Transceiver User’s Guide
3-3
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...
