Transcript Train Speed Control Unit

INTROUCTION
New Waltham is a flattened dumbbell, 1/2 of which is scenic and 1/2 of which is hidden using traditional DC. When I started I
decided I wanted to be able to sit and watch trains go by. This defined the layout as being a roundy round. However, I
did not want a tail chaser and living where I do a multi operator layout was not going to happen. Accordingly I
developed my automatic hidden siding system. This system lets me run 6 trains on the up line and 6 trains on the down
line together in a fixed sequence at realistic speeds. Thus, express trains go by at speed and slow trains go by slowly.
All this without any input from me. A complete cycle is about 14 minutes with gaps where there is nothing to see, just
like the real thing.
DESCRIPTON - Sidings
There are six hidden sidings on each of the up and down lines, each with its own assigned train, e.g. an express passenger
hauled by an A4, an empty coal train hauled by a WD 2-8-0 or a stopping passenger train B1 hauled. As an individual
train enters its assigned siding, a small magnet attached to the underside of a vehicle close to the train end activates a
reed switch mounted in the track as it passes over. The “pulse” generated by the reed switch is fed to the low voltage
side of a cheap auto auxiliary equipment relay that fires a capacitor discharge unit to change the appropriate point
motors and activate the train in the next track. All points are self isolating PECO so as the points are changed they
automatically isolate the incoming train and power up the outgoing train. This process is repeated for each siding so that
each train comes out of the hidden section into the scenic section and back into the hidden section to send out the next
train.
The hidden siding operation is not especially graceful since trains come to a sudden stop and immediately start at speed.
At first I was a bit nervous that this instant on/off would damage the loco motors, but after about 8 years and many
sessions, some of which have been over two continuous hours, there appears to be no negative impact. For the up line,
where the hidden sidings are on a curve, the momentum caused by the instant off caused the rear coaches of a fast
express to push those in front off the track. I used a simple resistor arrangement to mitigate the off effect.
DESCRIPTION - Speed Control
Each siding has its own speed controller that is always on and is pre-set to a speed appropriate for the train in the siding it
controls. A common in two out micro switch (lever switch) is activated either by the point blade tie rod or the upper rod
coming from the top of the Peco point motor. The micro switch is connected to a double pole double throw micro relay
in the control box. Using what I call linear ladder logic, the appropriate power from the designated controller is fed to
the track. Thus, just like the automatic siding operation, the train in activates the speed of the next train out.
I have installed an indicator light so that I know which controller is in use at any one time
GENERAL
Initially, I used a circuit from a hobby book that used things like silicon controlled rectifier circuits. This sort of worked, but
was subject to stray currents and would activate a train at any time it chose. This resulted in some interesting conflicts
and more than a bit of bad language. In the end I adopted the KISS system described here. Apart from burning one
relay out when a magnet sat over the reed switch keeping it activated, the system has operated flawlessly for over 8
years now.
The biggest single problem I had was learning about the operation of “traditional” reed switches. I had put the magnet at the
back of the train so that as the train came to a stop there was sufficient momentum to take up the coupling slack and
move the magnet past the reed switch. For express trains this worked perfectly, however for slow trains I would get the
train sitting over the reed switch causing chatter stopping the automated sequencing process. Eventually, I discovered
that the traditional reed switch has two “on” positions if placed longitudinally in the track. This is because the actual
ferro magnetic iron is the contact on either side of the centre lever. Thus, as the magnet passes over there is one pulse as
it hits the first wire of ferro magnetic iron, then after a short off a second on pulse again as it hits the second ferro
magnetic wire. On a fast train there was enough momentum to propel the vehicle carrying the magnet past both
contacts. On a slow train there was insufficient momentum. The solution was simple, stick the damm reed switch in
from the side so that only one side is activated. As a matter of note I was able to purchase a number of home security
reed switches that are used to monitor windows, etc. These are about 1/4” diameter and fit nicely between the track and
do not have this double on situation. Also, for one pick-up freight that I run very slowly I found it necessary to put a
small downhill “hump” after the reed switch to ensure that the vehicle with the magnet runs past the switch. At some
point I may try to use the power from the activated track to push the train well clear of the reed switch and then stop it in
an isolated section in front of the out point.
FUTURE
Upgrade to 9 trains in each directions. This should give me a running time of 20+ minutes and more importantly will let me
run all the must have locos they I continue to buy
Install a station stop sequence for stopping passenger trains. I have a module and think I have a plan. TIP
TIP
I have a RF panic switch that switches the power of to the main power bar. When I was setting all this up, somewhat
surprisingly there were times when I got something wrong resulting in two or more trains heading out at the same time.
After a while of sprinting from one room to another, banging my head as I ducted under the table and putting endless
wagons back on the track when I wasn’t fast enough I can now stop everything at the press of a button from anywhere
in the house. Technology is great.
Down Road Typical Track Loading
Track 1, Express Passenger, A4 hauled - Fast
Track 2, Long Empty Coal Train, WD 2-8-0 hauled - Slow
Track 3, Semi Fast Passenger Train, A3 hauled - Intermediate fast
Track 4, Iron Ore Train, 2-10-0 hauled - Slow
Track 5, Stopping Passenger, B1 hauled - Intermediate
Track 6, Pick-up Freight, J39 or O4 hauled - Slow
Low Voltage Side Point (Switch) Motors
12V DC Source
Relay
Track 1
Relay
Track 2
Relay
Track 3
Relay
Track 4
Common
Reed Switch Track 1
Reed Switch Track 2
Reed Switch Track 3
Reed Switch Track 4
Reed Switch Track 5
Reed Switch Track 6
Notes:
1, Relays are cheap auto auxiliary fog/driving lamp relays
2, Green lines are low voltage low current relay input connections
3, Red lines are high voltage high amperage Capacitor Discharge Unit circuit
Relay
Track 5
Relay
Track 6
Capacitor Discharge Side Point (Switch) Motors
Only one side of siding point motor connections shown for simplicity
16 to 24
VAC IN
Relay
Track 1
Relay
Track 2
Relay
Track 3
Relay
Track 4
Relay
Track 5
Relay
Track 6
Capacitor
Discharge
Unit
Track 1
Track 2
Track 3
Track 4
Track 5
Common
All point motors are self isolating
Track 6
Point Motors. . Arrow
indicates point throw
(pull) direction
Thus, CD unit pulls point tie bar in this direction
To set points for straight ahead
Train Speed Control Circuit
Train Siding Identifier Process
12 V Power Source
in from master control unit
Point Tie Rod (Bar)
Return lines to controller
selection relay array in
master control unit
Micro Switch or lever switch, as it is also known,
Activated by point tie rod or point motor top pin
Train Speed Control Unit
Track
Track 6
Controller
Power
source
Input from
microswitch
for track
1
2
3
4
12 VDC
Source
5
6
Common out to microswitch
Ladder Logic Circuit for Speed Control Relay Circuit
Point tie bar
Common In
1
2
3
4
5
6
Siding Slow Down Section
Train Direction
Isolating Gap
Simple Variable Resistor (Potensiometer) going from
Zero to 10/20 Kohms
For a slow freight train set resistor to 0. For a high speed express passenger train adjust resistor as
appropriate so that the train slows down mitigating the impact of the sudden power loss as the points
are switched. Reverse effect when power is abruptly switched on when the points are opened and
starts up at a slower speed. I find this essential to avoid derailing a set of 10 close coupled coaches
when using a curved storage siding
Notes on Reed Switches
Reed Switch
Direction of (magnet) travel
1st contact
2nd contact
Wrong! On a slow
moving train this will
give two pulses
Moving Contact
Correct, only gives a
single pulse
Ferro magnetic iron
(Tricky to solder to)
For slow moving trains, where there is minimum momentum to propel the
wagons past the reed switch effective magnetic field area,I have put a small
hump - about 1/16” high - to ensure the wagon with the magnet rolls clear
Loco motion lost
At this point as wagon
passes over reed switch
Wagons roll down hill taking up
coupling slack and clear magnetic
field area when loco stops
Reed Switch
Direction of travel
Track