SMD82 - Switch
Machine Driver Application
Information
Solenoid Type Switch
Machines:
The following switch machines have been tested:
Atlas HO snap
NJI
Peco PL-10 "black"
Rix Twin Coil
Kato N unitrack - requires two external resistors
All the machines were tested with a Digitrax DB150
Command Station set to the appropriate scale. The Rix
twin coil machine requires tension on the swing arm to
keep the internal weight from bouncing off its end stop
when the pulse of power is applied. Operating the machine
without tension on the arm gives the impression that it
is not working correctly.
The Kato unitrack electric turnout is a special case
since it only has two electrical connections as compared
to three for the others. The SMD82 provides power on the
common connection, so two resistors are required from the
common to power the machine. Figure 1 below shows how the
resistors are electrically connected. Warning: the SMD82
output configuration must be set to solenoid type
operation for proper operation.
Most solenoid type machines require a large pulse of
power. The design intent of the SMD82 was to have
enough power to be able to activate "snap" any HO/N scale
solenoid type switch machine even when they were some
what "sluggish".
There are several factors that can contribute to
poor "sluggish" performance. A few include
electrical connections at the driver and the machine,
size and length of wire used for connection and
mechanical linkage from machine to switch. If you are
having problems check these areas.
The SMD82 uses screw type terminal connectors for
connecting to the switch machines. Wire size
recommendations are as follows: If you use the 26 gauge
wire try to keep the wire length to each switch machine
to under 12 feet. With 24 gauge you should stay under 18
feet. With larger size wire you can have longer wire
lengths.
Route Features:
The internal route feature of the SMD82 is well suited
for controlling yard switching. With a single switch
command up to eight switches can be controlled at a time.
Up to 16 individual routes can be configured, so there is
a wide range of combinations available. See figure 2 for
an example of route usage in a yard.
Local Input:
The SMD82 has a number of inputs for local control. You
can connect push buttons or toggles switches to control
the outputs in a variety of ways. The routes shown in the
example in figure 2 could be controlled by push buttons
as well from the throttle.
You can connect our DBD22 block occupancy detector to the
SMD82 inputs to provide some unique capabilities. Figure
3 shows a diagram of how the SMD82 could be used to
control siding switches (turnouts). Using primary input 1
and auxiliary input 1 a conditional route can be set up
were auxiliary input 1 is dependent on the state of
primary input 1. When a train is in a siding and another
train crosses the trigger section, the two switches can
be correctly aligned. If the siding is not occupied the
trigger section has no effect. Figure 4 shows a more
detailed diagram for connecting the DBD22 and SMD82.
The primary input connector is a 10 pin flat ribbon cable
(IDC) type. If you prefer screw type connectors you can
use the TSA.
Using the SMD82 without track power:
The SMD82 requires track power (DCC packets) connected to
the Rail A and Rail B terminals for remote control and
for programming via the main track or programming track.
However, once programmed, operation via inputs is
possible without connection to the track. In this case
only the inputs will control the outputs.
If you are using the SMD82 to drive tortoise type switch
machines then 12 volts DC will work. If you are using it
to drive solenoid switch machines then use 9 volts AC.
Don't use 12 volts AC or you may over stress the SMD82.
The capacitor discharge unit requires AC voltage to
obtain the correct power for solenoid switch machines.
Track power (DCC) is a type of AC with a peak of about 14
volts for HO scale. 9 volts AC has a peak of about 14
volts so it is about equivalent to the track voltage.
The TKDC (rectified track voltage) and GND terminals are
available for powering external loads. These terminals
could be used for powering the SMD82 but there is really
no reason for doing so.
SMD82 Known Problems:
10/21/06:
Various outputs are closed or thrown after 'power on'
even though option 1 or 2 has not been set. This problem
is caused by any of the inputs being configurated as
active with a 'low to high' transition or a 'on change'
transition. When configurated as active with a
'high to low' transition this problem does not occur.
SMD82s with this problem can be identified by a single
silver mark (1) on the integrated circuit (IC). For
solution to the problem contact us.
5/1/07:
Push buttons or other devices connected to inputs respond
intermittently or not at all. This problem is caused by
loco addresses 111 to 127 confusing the SMD82. The work
around is to use long addresses for any loco requiring an
address in that range.
