LKM LKM75X User guide

Handbuch zu den Komponenten des Systems
März 2017

Manual relating to the system components
March 2017

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The radio system type LKM75x
Table of contents
1. General
2. International standard IEE 802.15.4
3. Receiver LKM751
4. Analogue unit LKM752
5. Transmitter EEPROM
6. Transmitter with I2C-bus LKM753
7. Radio transmitter LKM754
8. The program WPAN868
9. Appendix 1
Interface protocol USB and RS485 (not Modbus)
10.Appendix 2
Terminal assignment of the receiver LKM751

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1. General
The radio system type 75X is a system designed for transmitting physical quantities
as, for example, temperature, moisture, light intensity and pressure. The sensors
used are partly compatible with our multi measuring device type DTM 4000, and they
can also be employed in systems like Rasberry and Co. It has a very flexible
structure and can easily be extended to other sizes. Several digital and analogue
channels are available for evaluation purposes. The transmitters are powered by
batteries which, depending on the transmission frequency, have a lifetime of about 2
years.
The devices operate in the licence-free frequency band of 868/915MHZ, thus also
covering the American frequency band. The permitted transmission capacity enables
distances up to 500 m to be bridged.
2. International standard IEE 802.15.4
The standard IEE 802.15.4 has been developed for the installation of low-power
radio networks for the short-range radio data transmission, and serves particularly to
automate the industrial and building technology. The development started
approximately in the year 2000.
The standard describes the bit transmission layer (layer 1, PHY-layer and the data
link layer, layer 2, MAC- layer). The ZigBee-protocol is also based on this standard.
The transmission band is split up into several channels. If needed, the user can
switch between them. The data transmission takes place primarily in the licence-free
868 MHz band (Europe, Asia), and in the 2.4 GHz-band (worldwide).
The radio system type LKM75X operates in the 868/915MHz-band.
2.1 Structure of the system
Each transmitter is identified via an IEEE-number. This number is firmly assigned by
the manufacturer of the modules. For identifying the network, the PAN-ID must be
applied. It is fixed in the receiver, however, it is possible to change it. Before a
transmitter is put into operation, it has to be told –via the WPAN868 software –with
which PAN-ID it is allowed to register. Thus, during each transmission, the IEEE-
number, the PAN-ID, the kind of the transmitted data (temperature,
temperature/moisture, light), and the corresponding values are sent. In the Appendix,
the structure of the protocol which is output by the receiver via the interface is shown.
If no PAN-ID is input into the transmitter, the PAN-ID 0x1000 is used. However, the
data transmission can also take place via transmitters located in the network,
provided they are supplied with sufficient energy. In this case, routing will be
automatically effected.

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3. Receiver LKM751
3.1 General
The receiver is mounted in a standard rail housing and supplied with 24 V. It is
provided with several serial interfaces. The LKM751 device is able to communicate
with other components via a bus system which is integrated in the rail. At present,
this is the analogue unit. No external connections are required any more.
Furthermore, the receiver is equipped with an illuminated LCD which allows the
values of 2 or 4 channels to be displayed. The display mode is configured via the
software. Figure 3.1 shows the position of the various function elements. If the
jumper for the write protection of the EEPROM is removed, the existing
configuration cannot be overwritten any more!
3.2 USB interface
The receiver is provided with a mini-USB interface by means of which it can be
configured, and the data can be read out. A corresponding program developed for
these tasks, as well as a suitable cable are supplied with each receiver. These
programs are described separately. The structure of the data sets is shown in the
Appendix. The USB interface enables the receiver to be supplied with voltage, too.
However, the analogue unit cannot be operated with it.
3.3 RS485 interface
This interface allows the data to be transmitted over longer distances. In addition,
also other evaluation units (PLC etc.) can be connected. This interface is also
designed as Modbus interface (switchable via software). Some more detailed
information can be found in the Modbus manual.
3.4 LCD
The LCD is backlit. Up to 4 measuring values can be displayed. The first four
registered transmitters are automatically displayed. Via the WPAN686 program, the
user may fix whether 2 or 4 values are displayed.

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3.5 Alarm-/Low battery relay
The receiver includes 2 potential-free semi-conductor relays whose contacts are led
out. They can arbitrarily be interconnected. The LowBat-control is triggered when the
battery voltage of one of the registered transmitters falls below 2.7 V. Thus, also in
small autonomous systems a signal can be released to inform the user about an
incident to be counteracted. The alarm relay is an additional option. Up to 4
transmitters can be selected. In case a pre-defined limit value is exceeded, the relay
will be triggered. The relays can cope with a voltage of maximally 60 V and a current
of 0.5 A.
3.6 LED
The receiver also includes 3 LEDs serving the following functions:
LED1 Operation display
LED2 Network available
LED3 Radio signal
LED1 lights up green when the operating voltage is on.
LED2 lights up when at least one receiver is registered.
LED3 flashes briefly when a message is received.
Fig. 3.1
Position of the single objects

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4. Analogue unit LKM752
Up to 2 analogue units can be connected via the internal bus. Each analogue unit
has 4 outputs 0...10V and 4...20mA. A current output and a voltage output
correspond with one another in each case. This means, they operate in the same
measuring range. The measuring range is again set via the WPAN686 program. A
total of up to 8 analogue outputs can be used. Due to its modular structure, the
system is very flexible. The outputs are short-circuit proof. However, it is not allowed
to supply external voltage to them. If 2 analogue modules are coupled, the jumper of
one of them must be removed to allow module recognition.
Fig. 4.1
Analogue module LKM752
5. Transmitter EEPROM
The EEPROM incorporated in the transmitter is of special importance. It saves a
possible offset and also the PAN-ID of the receiver to which the transmitter can log
on. On the circuit board, there is a jumper for write protection. If it is plugged, the
write protection for the EEPROM is unlocked. Now, using the WPAN868 program,
the various values can be configured. At the same time, this jumper prevents the
transmitter from going into sleep mode when being switched on. In other words, the
PC has immediate access to the transmitter without having to wait for the sleep cycle
of the transmitter. Please take care to remove this jumper after setting the values
as the battery will be exhausted after a few days!

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6. Transmitter with I2C-bus LKM753
The LKM753 device is provided with a standard I2C interface. For this, a large
number of sensors are available. So far, we have implemented a temperature sensor
and a combined temperature/moisture sensor. An EEPROM incorporated in the
sensor allows accuracy to be improved drastically. These sensors are also
compatible with our multifunction meter type DTM4000. The sensor type will be
recognized automatically.
As energy source a lithium battery type CR123 is used. The transmission frequency
being 1min, its lifetime will be approximately 2 years. Also, there is the option to
include further sensor types.
Fig. 6.1 Position of the operating
elements
On the circuit board, there are
2 potentiometers which can be used –
according to the sensor - for offset
corrections.
7. Radio transmitter LKM754
The LKM754 device is a programmable transmitter designed for various
thermocouples and resistance sensors.
Fig. 7.1 Position of the operating
elements
The following types can be
implemented:
Thermocouples: K, N, J, T, S, B
Resistance sensors:
Pt100/1000
Depending on the sensor used, various
assignments and jumper positions are
possible.