Operations A Train Shuttle controller for DC power

Chapter-4e-1 Page 21 A Train Shuttle

A loco and wagons moving along a side track or through a mountain pass can add to the overall effect of a layout. This shuttle controller is simple to setup and install and provides a layout feature point.

Train shuttle operation needs a DC throttle as with DCC power the train direction can not be sensed electrically, nor will a blocking diode stop the train. However a shuttle could be incorporated within a DCC layout as a separate scene. This circuit is simple and does not allow for intermediate station stops. Speed control (stop and start) is fast as power is cut immediately it enters the stop track or starts up but these areas could be hidden behind other scenery. Speed control is provided by your throttle. If you have grade changes then you could use a throttle with feedback to maintain speed. Because the detection circuit is looking for a loss of track voltage any dirt on the track or loco wheels may cause an unwanted direction change to take place.

Schematic and operation:

The blocking diodes control the stopping tracks and will only allow the loco to move back onto the main line. There is one at each end. While the loco is drawing power from the main track there is a voltage developed across the bridge rectifier in the schematic. This 1.2 volts activates one of the optical couplers, depending on the train direction. The tied collector outputs are at zero volts while the train is detected and this holds the 555 timer at 'reset', When the loco runs onto the stop track no current is drawn and the voltage is lost. The reset (pin 4) is released and the timer trigger 'TR' goes positive

to start the timeout. The timer output at pin 3 goes positive. The capacitors are to filter loco motor and wheel contact noise from the input and provide a delay to the trigger. At timeout the timer output goes to 0 volts, this turns the transistor on and the positive change at the 'CD4013' flip-flop clock input 'Cp' triggers it. This is a digital circuit and the output at 'Q' will change to the state of the input at 'D' on receiving a clock pulse. This is tied to the inverse output at 'Q/' and so the 'Q' output toggles on and off as each stop track is reached. This changes the state of the relay driver transistor and the relay is either picked or dropped. So every clock input will reverse the direction of the loco. The LED indicates when the timer has been triggered and is timing out. The timeout delay is controlled by the 2 megohm (2m0) potentiometer and the 4.7 ufd capacitor and can be varied from 9 seconds to 120 seconds with the values shown.

Chapter-4e-2 Page 22

The strip Board or Veroboard as it can be called, is cut to 17 rows by 30 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 17 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. Note copper side is flipped. Check carefully twice, as it is too easy to misplace a mark. Check that 41 holes have been marked. When satisfied twist a No.31 (1/8 inch) drill in each hole to cut away double check before soldering the the copper around the hole. Burnish wires in. Are they correctly related the copper to clean any ragged bits to the cuts on the copper side. and check with magnifier and/or There are 25 wire links. Make sure meter that the copper round each that you have them correctly marked hole is fully cut away. placed under the IC's. Another 4 Link wires: links are to be added on the I use a single strand insulated wire copper side after the topside for the links, like Kynar wire wrap soldering is done, shown in green wire. Again mark the holes and on the component layout.

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. Add the Integrated circuits next. You can use sockets for the 4013 and 555 I.C.s which will make it easier to trouble shoot later. Note that the two 4N35's are head to tail as it were. I don't solder pin 3 or 6 of the 4N35 ﾒ s as they are not used although pin 6 is isolated on the copper strip. The capacitors and connectors go on last. Leave the relay and the green link wires until the testing is done. The connections are shown on PC screw terminals but you could solder wires directly to the PCB if you plan a permanent connection.

Chapter-4e-3 Page 23

Checking:

When all is soldered in place get out the magnifying glass and carefully check each copper strip forsolder spills over to adjacent strips. Running a craft knife blade along the gap between the strips also helps to locate spillover solder. Use an ohm meter to check that the +12 to Ground terminals do not have a short and that there is no short between adjacent copper strips or across the copper strip cuts.

Apply 12 volt power and check with a meter between pins 1 and 8 of the 555 timer chip and 7 and 14 of the 4013 I.C.s that it is there. Turn the 2m0 Pot fully anticlockwise and short out pins 4 and 5 of one of the 4N35 opto couplers. The LED should come on when you release the short, after a short delay and this time depends on the pot setting. If this is correct then install the relay and do it again and the relay should click on or off. To finish put the links shown in green, on the copper side of the PCB,. Prepare the length of track by putting a cut in the same track side at each end, a train length in from the end - plus a bit. Solder a 1N4004 diode across each cut orientated as shown in the diagram. Solder wires onto the track for the power and run these to the PCB terminals, Tk-a and Tkb. Connect the CAB to the other terminals and it is ready to go. Mount a loco, switch on the 12 volts DC, set the throttle and something should happen. Cab direction is not important as the train will stop at each end track if the diodes are correctly connected.

Trouble Shooting:

With no train on the track when you apply the 12 volts the LED should come on after a few seconds delay (set by the Pot) If it doesn't, measure the voltage at the 555 pin 6. it should be 12 volts or rising toward 12 volts. If 0 volts there is a short or open circuit. If above zero but not changing more positive then the 47u capacitor could be inserted wrong way round. On the 4013 dual flip flop, pin 3 should be about 0 volts, pins 2 and 5 at the same voltage and pins 2 and 3 at opposite voltage. Any other condition then re-check for 1 of CD4013 cmos IC

copper shorts, wrong link wires etc. Verify there are link wires under Resistors, 1 of 22 Ohms (22R), 1 of 1,000 Ohms (1K0) 4 of 10,000 Ohms, 2 of 22,000 Ohms (22K) 1 trim potentiometer of 2 megohm (2m0) - this could be mounted off the board for variable timing. Capacitors, 1 of 4.7 ufd and 2 of 100 mfd at 16 volt 1 of 220 ufd at 16 volt working

3 of 1N4004 diode, 1 of LED indicator 1 of DB155G integrated rectifier 2 of 4N35 optical couplers 1 of LM555 timer IC, the I.C.

1 each of transistors 2N2907 and 2N2222 1 12 volt DPCO (DPDT) power relay 5 - 8 amp. 2 way PCB screw terminals, 3 of Strip board 30 x 17 rows

Bottom view of the green link wires.

Note this is an inverted view.

Resistor Color Codes:

Symbol Value No. 3 band plus tolerance. 4 band plus tolerance band. 22R 22 Ohms 1 red-red-black red-red-black-gold note a gold multiplier equals times 0.1 1K0 1,000 Ohms 1 brown-black-red brown-black-black-brown 10K 10,000 Ohms 4 brown-black-orange brown-black-black-red 22K 22,000 Ohms 2 red-red-yellow red-red-black-orange 2M0 2,000,000 Ohms 1 red-black-green red-black-black-yellow

The tolerance band will be Gold for 5% and Brown for 1% resistors

Chapter-5a Page 24

An Intermediate Signal

Intermediate Signals are located between two Home blocks and are normally a repeater of the Home signal, showing a cautionary aspect if the Home is at stop. However if you don't have a layout set up with blocks and signaling then this standalone signal may provide some more realism to the scenery between stations.

The signal is two aspect, approach lit, and goes to red as the train passes it, staying Red for a set time period. The circuit is for an Analog or pulsed DC power as it is direction dependent. Circuit operation is initiated when the train passes Spot A, a short isolated rail break some distance back from the signal. This activates a timer which powers the Green LED. When the train reaches Spot B, located beside the signal it changes it to Red and the timer starts timing. The time period is adjustable, see the table for maximum times. It can be held at Red once triggered by putting a ground to the Hold terminal. The signal can be 2 aspect LED's, Green and Red or a double Tri-LED type searchlight signal. Timing range with a 100 ufd capacitor is: A 500K trim resistor gives 78 seconds max. A 1M0 trim resistor gives 132 seconds.

Option for:

1. Dual LED searchlight signal Connect the two LED leads to the R and Retn terminals and connect a 1K0 (1000 Ohm) resistor between the G and Retn terminals. Reverse the signal LED leads if the wrong.colors are shown. 2. Power Control Connect a 12volt DPDT relay and a reversed diode between R and Gnd terminals to control the power on the rail before Spot B. You could use this to space trains that are running on a common CAB. In this case the spot B should be outside the controlled power section or MU'd locos will have to drag the second loco along a dead track.

Circuit description.

When the loco wheels bridge the rails at Spot A the current activates the LED in the 4N25 optical coupler. This causes the output pin 5 to send a ground to trigger the first timer, U1. Its Q output goes to 10 volts and powers the second timer U2

through pin 8. This timer powers up in a reset state and its output pin 3 is at ground. This draws current through R8 and R9 to turn on the transistor and pass current to the green LED. The train bridging Spot B sends a ground to pin 2 of U2 and triggers the second timer. Its pin 3 goes to 12 volts which stops the current to the green LED and supplies a current through the Red LED to ground. U2 pin 7 which was at ground and holding a current to the LED L1 now goes open circuit and allows the positive voltage through the LED to charge the timing capacitor through the time adjusting variable resistor.

Chapter 5a-2 Page 25

The time can be set from 2 seconds to more than 2 minutes by selecting and adjusting this control. Note L1 is part of the timimg and not just an indicator.

Construction:

Vero Board or strip board 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. Temporarily number the front and back (copper side) then using the copper side diagram put a spot on the holes to be cut using an ink marker. Check carefully twice as it too easy to misplace a mark. When satisfied twist a No.32 drill in each hole to cut away the copper round the hole. Burnish the copper to clean any ragged bits and check with magnifier and meter that the copper round each hole is fully cut. Link wires I use a single strand insulated wire for the links, like Kynar wire wrapping wire. Again mark the holes and double check before soldering the wires in. There are 17 wire links. Component placement It is best to start with the low profile resistors and diodes first, observe polarity of the diodes. Use the wire links as a check for correct component location. Touch the soldering iron to the copper and the component lead for a second then apply the solder wire to the 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. Add the Integrated circuits next. Note that pin 6 of the 4N25s is not Solder the wires onto them before soldered and it comes through at a cutting them loose with a dremal cut location. Some 4N25's have an cut-off disk. Make sure they are at internal connection to pin 6. The the same height as the adjacent capacitors, LED and connectors rails after this. It does not matter go on last. In the picture the which rail they are on but the outputs are on PC screw type connection from the right hand rail connections and the Spot inputs on 2 pin header plugs. Checking: (when running toward the signal) should go to the positive marked input pin. See ‘Short Rail Break’ chapter. When all is soldered in place get out the magnifying glass and Components carefully check each copper strip Resistors, for solder spill-over to adjacent strips. Running a craft knife blade along the gap between the strips 2 of 330 Ohm, 3 of 1,000 Ohms, 1 of 6,800 Ohms, 3 of 10,000 Ohms [330R] [1K0] [6K8] [10K] also helps to locate spill-over 1 megohm or 2.2 megohm trim pot solder. Meter the +12 to Ground Capacitors, - 2 of 0.01ufd and check the resistance is high, Electrolytics you could also meter between the 2 of 1u0 at 16v working copper strips for shorts. 1 of 100ufd at16v working Diodes, 1N4148, 1N4004 (2 of) Installing: Transistor, 2N4403 NPN If the signal wires are enameled ICs, LM555N (2), 4N25 (2) copper clean off the ends with 400 Others, LED – red 1 grit sandpaper, mount the signal PC Mount Screw Terminals 6 way, and feed the wires through and or use 3 of 2 terminals etc. solder to the PC board plug. Locate where you are going to put the Isolated rails for the spot Header socket and plug 2way (2) Strip board piece 14 rows by 26 holes or to suit. detectors. They should be two sleepers long.

Chapter 5a-3 Page 26

330R 330 Ohms 1K0 1,000 Ohms 6K8 6,800 Ohms 10K 10,000 Ohms 3

2 3 1

orange-orange-brown brown-black-red blue-grey-orange brown-black-orange

| orange-orange-black-black | brown-black-black-brown | blue-grey-black-red | brown-black-black-red