This page shows information for a Controls Only version of the Mark VII - Automatic Reversing Circuit shown on this site.
The operation of the Controls Only - Automatic Reversing Circuit's timing system is functionally the same as that of the Mark VII - Automatic Reversing Circuit.
However, the Controls Only - Automatic Reversing Circuit does not have a built in throttle.
The diagram show the equivalent outputs of the circuit board. These outputs are used to interface with the external throttle.
The circuit board does not have a throttle section. The circuit board only has adjustments for the wait times at the ends of the track.
The time that the SHUTTLE waits at each end of the track can be individually adjusted from approximately 30 seconds to 6 minutes.
The BRAKING distance can be as long as 1.5 meter (5 feet) with an HO scale locomotive traveling at approximately 20 MPH.
The SHUTTLE can be a single car or a train of any length.
Optoisolators are used as interfaces between the timing circuit and an external throttle. The circuit can control any type of throttle with the proper adapter circuitry.
The circuit times and reverses the shuttle the same as the Mark VII - Automatic Reversing Circuit but does not have its own trottle section.
The circuit uses optoisolators at its outputs that can interface with almost any type of throttle, including a DCC system, using adapter circuitry.
The Reversing Circuit can be disabled so that the controlled throttle can be used as a normal throttle.
The Controls Only - Automatic Reversing circuit can be controlled by one or more Automatic Station Stop circuits shown on this page and the Mark VII - Automatic Reversing Circuit page.
Four IR/visible light sensitive phototransistors are used to sense the position of the shuttle and set its braking and stopping.
The next diagram shows how the phototransistor sensors are placed along the SHUTTLE track.
To start: The SHUTTLE is sitting over the EAST end STOP sensor (Q1). LED 1 is ON - Timer IC 3B is active.
When B timer completes its cycle its OUTPUT will go LOW and LED 6 will turn ON. The direction output will be set for EAST to WEST travel and the SHUTTLE will begin to accelerate as set by the external throttle.
The SHUTTLE will continue to accelerate to the maximum voltage set by the external throttle.
When the SHUTTLE covers the BRAKE sensor Q3, LED 3 will turn ON. The IC 3B timer is reset and the IC 3A timer is activated.
At the same time as SHUTTLE covers sensor Q3 the the SLOW brake output will be activated and the SHUTTLE will decelerate as set by the external throttle.
When the SHUTTLE covers the STOP sensor Q4, LED 4 will turn ON and the QUICK brake will be activated. The SHUTTLE should stop in a distance of approximately 1/2 car length or less as set by the external throttle.
The SHUTTLE will wait at the WEST end of the track until the IC 3A timer completes its cycle.
When the IC 3A timer completes its cycle its output will go LOW and LED 5 will turn ON. The direction output will be set for WEST to EAST travel and the SHUTTLE will begin to accelerate.
When the SHUTTLE covers the BRAKE sensor Q3, LED 3 will be ON but there will be no change in the circuit.
The SHUTTLE will continue to accelerate to its maximum as set by the external throttle.
When the SHUTTLE covers the BRAKE sensor Q2, LED 2 will turn ON. The IC 3A timer is reset and the IC 3B timer is activated and begins its timing cycle.
At the same time as SHUTTLE covers sensor Q2 the the SLOW brake will be activated and the SHUTTLE will decelerate.
When the SHUTTLE covers the STOP sensor Q1, LED 1 will turn ON and the QUICK brake will be activated. The SHUTTLE should stop in a distance of approximately 1/2 of a car length or less.
The SHUTTLE will wait at the EAST end of the track until the IC 3B timer completes its cycle.
The cycle will now repeat itself with the SHUTTLE traveling between and waiting at each end of the track.
NOTE: The accelerate and braking rates are set by the external throttle. The controls only circuit only controls the waiting times and direction of the SHUTTLE.
The BRAKE sensors (Q2, Q3) control the direction of the SHUTTLE and activate the braking that gradually slows the SHUTTLE. The BRAKING distance can be as long as 1.5 meter (5 feet) with an HO scale locomotive traveling at approximately 20 MPH.
The STOP sensors (Q1, Q4) activate a QUICK braking action that will bring the slowly moving SHUTTLE to a stop over a distance of less than 1/2 of a car length. The STOP sensors should be positioned just short of where the front of the SHUTTLE should stop.
No specific distances are given as these will depend on the length of the track, the distance desired for braking and the operating characteristics of the SHUTTLE's motor. The SHUTTLE track itself can be of any length desired.
The brake sensors might have to be placed unequally to compensate for differences that the SHUTTLE motor may have when slowing in one direction versus the other. The only way to determine the exact placement of the sensors is by experimentation but with good quality motors this should not be a large factor in setting up the circuit.
Diode stopping sections at each end of the track are optional and provide runaway protection should the circuit not operate properly.
Light Emitting Diodes (LED 1, 2, 3, and 4) indicate when the phototransistor sensors are covered and braking will begin. Light Emitting Diodes (LED 5, and 6) indicate which direction the SHUTTLE will travel when the wait timer has run out.
The circuit uses a CD4011, Quad NAND logic IC to provide a memory function for the circuit. One half of this device controls the timers that determine how long the SHUTTLE will wait at each end of the track while the second half remembers the SHUTTLE's direction and controls the throttle's reversing relay.
If the SHUTTLE stops before it reaches a STOP sensors, (Q1, Q4) the circuit will still function correctly and reverse the SHUTTLE when the wait timer completes its cycle. Stopping short may occur until the motor has warmed up.
If the room lights are turned OFF the reversing circuit will go into a QUICK braking mode and stop the SHUTTLE.
When the lights are again turned ON the circuit will resume normal operation, however, depending on the direction of travel and how long the lights were OFF the SHUTTLE may have reversed itself when operation resume.
The QUICK brake is only active when one of the STOP sensors, Q1 and Q4, is covered by the SHUTTLE. Therefore, the throttle's braking rate setting (R29) should be adjusted so that the SHUTTLE is moving slowly enough for it to stop in less than the length of the first car.
The reversing relay is controlled by the top half of the CD4011 IC. The circuit is designed so that the direction of travel is changed when the SHUTTLE is ready to leave its stopping point. This is so that the relay cannot change the direction direction before the SHUTTLE is fully stopped.
The SHUTTLE does not have to be covering any of the four phototransistor sensors when the circuit's power is turned ON. However, the SHUTTLE must be between the STOP sensors to ensure proper circuit direction control.
The waiting times for the reversing circuit are controlled by R12/R13/C5 for the IC 3A timer and R18/R19/C6 for the IC 3B timer. For the values given, the calculated waiting times are from 33 seconds to approximately 6 minutes. Actual times may be longer.
The specifications of phototransistors Q1, 2, 3 and 4, are not critical and any that respond in the infrared and visible light ranges should work for this circuit.
The phototransistors use normal room light to control the circuit but the circuit could be adapted for day and night operation by using infrared LEDs to supply artificial light. For one possible method of doing this refer to the Day and Night Infrared Detection page at this site.
There are 1.0 microfarad capacitors (C1, 2, 3, 4) at the sensor input terminals to reduce the chance of electrical noise causing the circuit to operate improperly. Careful routing of the phototransistor wiring can reduce many noise problems.
If noise problems still persist, a 10K ohm resistor can be placed in series between the input terminals and the phototransistors.
The STOP sensor Q1 receives its power from the output of the IC 3B timer (PIN 9) while the STOP sensor Q4 receives its power from the output of the IC 3A timer (PIN 5).
This is so that the STOP sensor that a SHUTTLE is covering, is disabled when the circuit changes direction at the end of its wait. This causes the QUICK brake to turn OFF when the SHUTTLE is ready to leave its stopped position.
The SHUTTLE can cover both the BRAKE and STOP sensors simultaneously without affecting the operation of the circuit. This allows the SHUTTLE to be longer than the braking distance.
The control portions of the circuit operate at 5 Volts DC allowing the AC power input to the circuit to be as low as 10 Volts without affecting the overall operation of the circuit.
The throttle has a designed current capacity of 0.8 Amps. Resistor R32 sets the current limiting level for the throttle.
The Automatic Reversing Control Circuit is a stand alone circuit board designed to connect to existing throttles.
Connections for three DC throttles example are shown. The circuit can be connected to other types of thottles by adapting the circuitry of the throttles.
The Automatic Reversing Control Circuit controls the direction, waiting times, braking and quick brake. The throttle's controls are used to set the acceleration and braking rates for the shuttle.
In two of the examples, provision has been made to disable the reversing circuit and allow the throttle to be used as a stand alone throttle if needed.
The parts values shown for the throttle speed control and braking are suggestions only. Testing will be needed to find the best values for a particular shuttle or track arrangement.
The next diagram shows a more detailed view of how IC 2 is configured and its basic memory functions. The use of a CD4011, Quad NAND gate as a dual - SET / RESET type of Flip-Flop is a text book example of a memory device.
Depending on which BRAKE phototransistor is covered the bottom half of the CD4011 chip activates the corresponding timer.
When the output of one of the IC 3 timers goes to a LOW state, the top half of the CD4011 sets the direction the SHUTTLE will travel via the direction control relay.
The following picture is an example of an assembled circuitboard. The board is approximately is 6 inches by 4 inches. They are commercially made and have been tinned.
1 - Controls Only - Automatic Reversing Circuit circuit boards without parts are 21.00 dollars US each, plus postage.
1 - Assembled - Controls Only - Automatic Reversing Circuit circuit board is 55.00 dollars US, plus postage.
1 - Kit - Controls Only - Automatic Reversing Circuit circuit board with all parts is 50.00 dollars US, plus postage.
If you are interested in printed circuit boards please send an email to the following address: firstname.lastname@example.org Subject: Controls Only - Reversing Circuit
|CIRCUIT PART NUMBER||-||DESCRIPTION||-||DigiKey Part||-||Qty|
|IC 1||-||LM339 QUAD Comparator||-||LM339NFS-ND||-||1|
|IC 3||-||LM556 Dual Timer||-||LM556CNFS-ND||-||1|
|7805||-||5 Volt Regulator (TO-220)||-||LM7805CT-ND||-||1|
|Q1, 2, 3, 4||-||Phototransitors||-||160-1030-ND||-||4|
|LED5, 6||-||LED GREEN DIFF 3MM||-||754-1210-ND||-||2|
|LED1, 4||-||LED RED DIFF 3MM||-||754-1211-ND||-||2|
|LED2, 3||-||LED YELLOW DIFF 3MM||-||754-1212-ND||-||2|
|OI-1, 2 3||-||OPTOISO 2.5KV TRANS||-||160-1300-5-ND||-||3|
|D1, 2, 3, 4, 5, 6, 7, 8||-||Small Signal Diode||-||1N4148DICT-ND||-||8|
|R1, 4||-||390K ohm - 0.25W||-||390KQBK-ND||-||2|
|R2, 3||-||470K ohm - 0.25W||-||470KQBK-ND||-||2|
|R5 , 6. 13, 14||-||100K ohm - 0.25W||-||100KQBK-ND||-||4|
|R7, 8, 9, 10, 11, 14, 17, 20, 25||-||470 ohm - 0.25W||-||470QBK-ND||-||9|
|R15, 16, 22, 23||-||10K ohm - 0.25W||-||10KQBK-ND||-||3|
|R12, 18||-||1M Potentiometer||-||3352T-105LF-ND||-||2|
|C1, 2, 3, 4, 7||-||1.0uF / 50V||-||399-6596-ND||-||5|
|C5, 6||-||330uF / 35V||-||P5167-ND||-||2|
|C8||-||10uF / 50V||-||P5178-ND||-||2|
|Terminal Block||-||2 Position - 3.5mm||-||ED2635-ND||-||2|
|Terminal Block||-||3 Position - 3.5mm||-||ED2636-ND||-||3|
The explanations for the circuits on these pages cannot hope to cover every situation on every layout. For this reason be prepared to do some experimenting to get the results you want. This is especially true of circuits such as the "Across Track Infrared Detection" circuits and any other circuit that relies on other than direct electronic inputs, such as switches.
If you use any of these circuit ideas, ask your parts supplier for a copy of the manufacturers data sheets for any components that you have not used before. These sheets contain a wealth of data and circuit design information that no electronic or print article could approach and will save time and perhaps damage to the components themselves. These data sheets can often be found on the web site of the device manufacturers.
Although the circuits are functional the pages are not meant to be full descriptions of each circuit but rather as guides for adapting them for use by others. If you have any questions or comments please send them to the email address on the Circuit Index page.
22 April, 2017