User's Manual
7
May ’00 Chapter 1. Product Description
1.2.1 Power Supply
There are two separate 5V supplies to the Micro-reader, one for the output stage
(VSP) and the other for the logic (VSL). On power up VSL should rise faster than 0.1
V/ms to ensure a reliable operation. The Micro-reader has an on-board reset circuit
which will reset it should the supply fall below 4 V (± 0.2 V).
In order to avoid problems with noise conducted via the supply lines, we recommend
that if a single supply is used, separate connections from a common de-coupling ca-
pacitor are used to feed the Micro-reader.
1.2.2 Antenna
The Micro-reader has been designed for use with a 47 µH antenna with a Q of 10 to
20 to generate the exciter frequency of 134.2 kHz. Because of the low Q the system
does not need to be tuned.
1.2.3 Synchronization
There are two possible methods of wired synchronization:
1. Connect a pulse waveform to all RDEN- input pins of the Micro-readers to be
synchronized. The pulse would normally be at VSL, dropping to GND for 100
µ
s
every 200 ms.
2. Connect all SYNC outputs to an 'Or' and then connect this as an input to RDEN-
of each Micro-reader to be synchronized.
Wireless synchronization of the Micro-reader is very effective at synchronizing to ad-
jacent readers, however problems may occur if the antennas are positioned such that
a transponder can be within range of two readers at the same time. In this situation
one reader could synchronize with the transponder instead of the other reader.
When the WLSC input is active the Micro-reader is in wireless synchronization mode.
Wireless synchronization can also be switched on/off by a corresponding command
via the serial interface. During execution of this command it has priority over the
WLSC input. After the command execution the status of the WLSC input will be con-
sidered again.
Note:
The RF Module must not be supplied by Switched Mode Power Sup-
plies (SMPS). This is because most SMPS operate at frequencies
around 50 kHz. The harmonics of the generated field can interfere
with the TIRIS receiver. Therefore only use linear regulated power
supplies, or SMPS with a fundamental operating frequency of 200
kHz or higher.
WARNING:
C
ARE
MUST
BE
TAKEN
WHEN
HANDLING
THE
M
ICRO
-
READER
AS
HIGH
VOLTAGES
ACROSS
THE
ANTENNA
PINS
COULD
BE
HARMFUL
TO
YOUR
HEALTH
.