Single Line control/acquisition signaling

Chapter 5B-1 Page 27

Single Line Acquisition Signals

Here is a way to control a single line between two loops. Not prototypical but if you have two operators and the loops are not visible to each then the signals will advise if the single track is being used.

How it Works:

The first train to cross the detectors, A or B, will claim the line and turn the signals to Red. The circuit uses two 555 timers that are triggered as the train passes over the spot detectors. Spot A will trigger the top timer in the diagram and it will go into timing mode. However it will not be supplied with timing current until the train passes Spot B and its output (pin 3) goes positive. Now both timers start timing and when timed out reset each other to show green. This is unnecessary with DC power as block switching or the CAB direction controls who can use the line. The signals needed are common cathode. This allows two aspect (separate red and green LEDs) or tri-LEDs (searchlight). The Red leads from both signals connect to the Red terminal, green similarly to the Green terminal. The Red When the timer is triggered it can only be reset by the opposite timer being triggered. To stop in the middle and reverse back out would leave the signals at Red until a train passed over the other spot. The delay is adjustable by selection of C1 and C2 capacitors. It should be selected so that - LED drive includes a 270R (270 Ohm) resistor that can be changed to balance the light intensity of the Red and Green LEDs if they are uneven in output. The 560 Ohm (560R) dropping resistors are nominal for 12 volt drive.

a train running from A to B will fully pass point B before the signal changes to green. If problems are occasionally experienced and the system is not resetting then the 12 volt power could be routed through a push off switch, to force a reset.

The only other requirement is to train the operators to obey the signals.

Chapter 5B-2 Page 28

Construction:

The strip Board or Veroboard as it can be called, is cut to 14 rows by 26 hole size. You could allow a few extra rows top and bottom to make mounting holes. If you do, mask them while you mark the holes to be cut so you see only the 14 rows that will be used. This saves confusion and mistakes. Temporarily number the front and back (copper side) then using the copper side diagram put a spot on the ones to be cut using an ink marker. Check carefully twice, as it is too easy to misplace a mark. Check that 35 holes have been marked. When satisfied twist a No.31 (1/8 inch) drill in each hole to cut away the copper around the hole. Burnish the copper to clean any ragged bits and check with magnifier and/or meter that the copper round each marked hole is fully cut away. Link wires: I use a single strand insulated wire for the links, like Kynar wire wrap wire. Again mark the holes and double check before soldering the wires in. Are they correctly related to the cuts on the copper side. There are 18 wire links. Make sure that you have them correctly placed under the IC's.

Component placement:

It is best to start with the low profile resistors and diodes first, observe polarity of the diodes. Check each component against adjacent ones, links, etc before soldering.

Touch the soldering iron to the copper and the component lead for a second then apply the solder wire to the heated junction. The solder should melt and run out and along the copper and up the lead a little. Slide the iron up the lead when removing it. This prevents solder from spilling over to adjacent copper strips. Add the Integrated circuits next. I don't solder pin 3 or 6 of the 4N25s as they are not used. Some 4N25's have an internal connection to pin 6. The capacitors and connectors go on last. The outputs are on PC screw terminals and the Spot inputs on 2 pin PCB header plugs.

Chapter 5b-3 Page 29

Installation:

Checking:

When all is soldered in place get out the magnifying glass and carefully check each copper strip for solder spills over to adjacent strips. Running a craft knife blade along the gap between the strips also helps to locate spillover solder. Connect LEDs temporarily to the screw terminals. Apply 12 volt power and check with a meter between pins 1 and 8 of the timer chips that it is there. To activate the circuit without it being connected to the track short the 4N25 pins 4 and 5 which simulates a train crossing the detector strip. Install the Isolated Track section on the single track just past the turnouts. The single line should be longer than the longest train that you run but there is no limit to total length. Once triggered the delays will not start to time out until after the exit spot is crossed. The leads from the red LEDs go to the ‘Red’ terminal and the green LEDs to ‘Grn’. The common return from each goes to the terminals, return-1 and 2 (Retn).

Spot Detector Options:

Several detection methods can be used. This one, using an optical coupler, is very reliable and requires no modification to locos or rolling stock. A reed switch could be used in place of the optical coupler, with magnets on all locos. Infra-red, across the track sensing, could also be used with appropriate emitter diodes and photo transistor detectors. A grounded input is needed to trigger the timers (pin 2)

Bulb Signals Option:

To use signals with bulbs add a small 5 volt PCB relay, connected between the Red output and ground. Wire the signal lamps to the change over contacts .

Timing Capacitor Options -

C1 and C2 10 ufd gives 15 seconds, 22 ufd 34 seconds,. 33 ufd 51 seconds, 47 ufd 75 seconds, 100 ufd 155 seconds, Or (2min 35 seconds)

Block Signaling system This could be part of a signaling system. It will

Chapter 5b-4 work on single or double tracks between

Page 30 stations or loops. Each block of single track has 2 signals at the start of the block, one in each direction. These control the entry into the block. If there is already a train in the block then the entry signal is Red at both ends. When the block is clear both signals are Green. On double track only one signal is needed to control the entry into the block. There is no interlocking or power control in the system and operators need to drive on the signals Components Semiconductors: Resistors: Capacitors: 5 of 1N4004 diode , 2 of 1,200 Ohms, [1K2] 1 of 0.1ufd, 2 of 0.22ufd 2N4403 PNP transistor, 3 of 10,000 Ohms, [10K] Electrolytic, 100ufd 25volt working. 2 of 'W04' Bridge Rectifier, 2 of 1 megohm, [1M0] Optional - electros: 2 of 4N25 optical coupler, 2 of 560 Ohm , [560R] 10, 22, 33, 47ufd. - See Table. 2 of LM555N timer I.C. 1 of 270 Ohm, [270R] Strip board 26 x 14 rows 2 of 2 pin PC Connector, The tolerance band will be Gold for 5% and Brown for 1% resistors 6 way PC terminals

Resistor Color Codes

Symbol Value No. 3 band plus tolerance. 4 band plus tolerance band. 270R 270 Ohms 1 560R 560 Ohms 2 1K2 1,200 Ohms 2 10K 10,000 Ohms 3 1M0 1,000,000 Ohms 2 red-violet-brown green-blue-brown brown-red-red brown-black-orange brown-black-green red-violet-black-black green-blue-black-black brown-red-black-brown brown-black-black

redbrown-black-black-yellow