GENERAL
INTEREST
37
11/2002
Elektor Electronics
In order to transform a normal train detec-
tor module into a genuine address program-
ming module, you need a rotary switch with
one wiper contact and eight positions.
Although the well-known Lori switch has
twelve positions, it can be converted into an
eight-position switch by relocating the end
stop.
This switch is then used to select one of
the eight manual controllers, following which
a binary address between 1 and 255 is set
using switches b0–b8. Don’t forget that the
most significant bit (b7) must be connected
to input 0!
Now hold pushbutton switch S2
depressed for a few seconds. After this, the
address of the selected controller will have
been modified. Make sure that the same
address is not assigned to more than one
manual controller. The master controller will
allow this, but it will lead to confusing results
on the track.
The purpose of the transistor with the two
resistors is to invert the controller selection
signal.
This train detector module should be the
first module connected to the controller. If you
do not need to modify the addresses of the
manual controllers, but you do want to use
keypad functionality, a ‘dummy’ train detec-
tor module (which is a train detector module
with nothing connected to its inputs) must be
connected at this location. (In Figure 2, every-
thing except the train detector module has
been omitted.)
When modified manual controller address-
ing is used, the addresses are always ‘soft
programmed’. This means that the settings
are obliterated by a reset, so the master con-
troller restarts with the default addresses.
Deluxe manual controller addressing
Quickly programming a binary address into
your favourite manual controller so you can
command an express train to stop before an
impending collision is something best left to
‘bit fanatics’ with nerves of steel. However,
for model railway owners with lower stress
tolerance, we can offer a more luxurious ver-
sion of the address programmer.
This version is shown in
Figure 3
. By and
large, this circuit does the same thing as the
simple version. An 8-position switch is used
once again to select the controller, and even
the pushbutton switch is still present,
although here it is hidden inside the rotary
switch that is used (contacts 4 and 5 are
closed if you press on the knob).
This rotary switch (S1), which is called a
‘rotary encoder’, consists primarily of two
changeover contacts with a common connec-
tion (pin 1). If the knob is turned to the right,
as it moves between two positions contacts
reserved for address programming
and the keypad;
– the last 32 (8-bit) modules can still
be used as needed as return mod-
ules (with addresses 1–32).
Controller addressing
Simple controller addressing
With the new master controller, loco-
motive addresses can be set within
the range of 1 to 255. For a return
module (8 bits), all of these
addresses can be set in binary form,
and in principle eight of them are
needed to address all eight manual
controllers. Although reserving eight
modules for controller addresses
would have the advantage of making
it very easy to set the addresses, it
would drastically reduce the number
of possible keypad/return modules.
However, there are other options.
Since address setting is intended to
be done near the master controller,
we can take advantage of the eight
controller selection lines, which can
be found on connector K2 of the mas-
ter controller circuit board.
The controller selector lines are
normally all Low, but when one of
the eight controllers is selected, the
processor sets one of these lines
High (see
Figure 1
). During the
selection interval, the function
inputs are read, and thus it takes
only a small additional effort to look
at the S88 bus at the same time to
see whether a new address for the
controller may be present there.
To try out address setting, all you
actually need is a single EEDTS
detector module. The circuit shown
in
Figure 2
shows this quite clearly.
K2 - 1
K2 - 2
K2 - 3
K2 - 4
K2 - 5
K2 - 6
t
K2 - 7
K2 - 8
020125- 12
Figure 1. Timing diagram for the selection lines.
S1
1
2
3
4
5
6
7
8
S2
4k7
4k7
BC547
b7
b6
b5
b4
b3
b2
b1
b0
0
1
2
3
4
5
6
7
K2
EEDTS
train detection module
PCB 87291 - 8
020125-13
S88
Figure 2. The simplest version of the address setting circuit.
Summary of Contents for EPROM
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