About This Web Site

  Welcome to a page of electronic circuits that are mostly for model railroads. Shown are circuits that were developed to solve certain problems or achieve a desired control function. There are throttle, train detection, animation, control and general purpose circuits on this page.

  Following this section is a list of the circuits that appear on these pages. Select one of the internal page links or scroll down the page until you find something of interest.

  The link under the paragraphs in each section will take you to the document from which the text is taken. These documents will provide more detailed explanations and schematics for the circuits.

  The circuits listed in the index sections appear in no particular order but have been loosely grouped by the type of function they perform. The Numbers to the left of the index listings are arbitrary. There is also a "Miscellaneous Items Index" that features circuits that may not be model railroad related and non electronics related pages.

  Some of the circuits on this site, in their original form, are or were in use by the London Model Railroad Group. This large, 'O' Scale club layout is located at 69 Holbourn Ave., London, Ontario, Canada. Public viewing nights are the first Tuesday of the month from October to May.

  Note: The terms NORMAL and REVERSE for turnout alignment on the pages listed in this section are arbitrary and will depend on the actual needs of the user of the circuits.

• DIVERGING Speed: A speed not exceeding twenty five (25) miles per hour.

• LIMITED Speed: A speed not exceeding forty five (45) miles per hour.

• MEDIUM Speed: A speed not exceeding thirty (30) miles per hour.

• REDUCED Speed: A speed that will permit stopping within one-half the range of vision of equipment.

• RESTRICTED Speed: A speed that will permit stopping within one-half the range of vision of equipment, also prepared to stop short of a switch not properly lined and in no case exceeding SLOW speed.

  When moving at RESTRICTED speed, be on the lookout for broken rails. When a broken rail is detected, the movement must be stopped immediately and must not resume until permission is received from the RTC or signalman.

• SLOW Speed: A speed not exceeding fifteen (15) miles per hour.

  This circuit is a driver for up to three radio controlled servo motors that are availble from many sources. The circuit uses 556 Timer ICs to generate the pulses that control the position of the motor outputs.

Triple - Servo Motor Driver Circuit (LM556) (PCB)

  This page has information on power supplies for Rapido's RailCrew Switch Machines. Other possible control circuits are also shown.

Rapido RailCrew Switch Machine Power Supplies

  This circuit is a simple 3 light signal that uses a BOD to detect a train and timers to hold the signal at RED and then YELLOW for a period after the train has left the block.

3 Light Signal Animator

  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.

Reversing Control Circuit

  The purpose of this circuit is to allow signals circuits that rely on the track's polarity to determine the direction that the train is traveling.

  The circuit uses four, or more, photosensors placed along the track to start and hold the detection circuit.

Train Direction Sensing Circuit

  This page shows information for a Controls Only version of the MK VII Automatic Reversing Circuit. This circuit does not have a throttle section. It uses optoisolators as its outputs which then control an external throttle.

  This diagram illustrates the principle effect of rotating an arc eccentrically away from a similar arc. The net result is an increasing gap between the circumferences of the two arcs.

  The object of this project was to replace the 11 watt, low voltage, incandescent lamps used in these outdoor lighting fixtures, 8 fixtures in total, with LEDs. The lamps normally used in these fixtures either burned out or often would became loose and would go out.

  This page features simple and inexpensive, stand alone UNIPOLAR stepper motor driver using parts that are available from many sources.

  The driver is designed for medium and low speed applications with motors that draw up to 1.0 amp per phase. Higher current motors can be driven by adding external transistors.

  This page features simple and inexpensive, stand alone BIPOLAR stepper motor driver using parts that are available from many sources.

  The driver is designed for medium and low speed applications with motors that draw up to 1.0 amp per phase. Higher current motors can be driven by adding external transistors.

  This page features a Unipolar Stepper Motor driver that uses an EDE1200 (Unipolar) Stepper Motor Controller IC produced by eLab Digital Engineering to provide 5 control functions, including half-stepping.

  This a 3 Light type model railroad block signal circuit that can produce solid - Red, Yellow and Green signal aspects. The signals can be connected for NORMAL or APPROACH Green lighting for the signal.

  The basic circuit can also be used for 2 Light signals, PRR - position light type signals and can be adapted for Searchlight type signals that use 3 lead, bicolour LEDs.

  This circuit is for a switch machine controller for reversing loops. The circuit is light activated and designed to automatically operate stall type switch machines.

  The circuit on this page is designed to control a Single - Three Light (Green - Yellow - Red) traffic light assembly. The the length of time that each light is lit is independently adjustable between 4 and 40 seconds for the parts values specified.

  This circuit automatically controls crossing signals and gates in a prototypical manner.

  The circuit uses a bidirectional time delay that staggers the gates and lights so that they operate as would be seen at a typical crossing.

  The DCC booster shown on this page uses the LMD18200 motor driver H-bridge IC. The booster's designed output rating is 3 amps at 15 volts.

  This booster is designed to power stationary DCC decoders used to control off-track accessories, switch machines and signals.

  The circuit on this page is for a visible and infrared light detector circuit board. The input is sensed by a LM324 operational amplifier and the outputs is from a LM555 timers.

  The circuit on this page is for a visible and infrared light detector circuit board that has 8 detectors. LM339 voltage comparators are the active element.

  The circuit on this page is for a visible and infrared light detector circuit board that has 8 detectors. LM339 voltage comparators are the active element.

  This circuit is a driver for a mechanical - Grade Crossing Bell Ringer - that was originally built for the London Model Railroad Group.

  The circuit on this page is for a fast acting electronic circuit breaker for use with fixed and variable, low voltage AC and DC systems such as model railroad throttles. The circuit breaker's trip current setting has an adjustable range of 0.5 to 10 amps.

  The circuit on this page is for a visible and infrared light detector circuit board that has 4 detectors. The inputs are controlled by an LM339 voltage comparators and the outputs are from LM556 timers.

  The outputs have settable delayed release and can source or sink up to 200 milliamps. The output's release delay can be controlled by selecting the desired values for the resistors and capacitors at the input terminals of the LM556 timers.

  The DCC booster shown on this page uses the LMD18200 motor driver H-bridge IC. The booster's designed output rating is 3 amps at 15 volts.

  In these circuits a transformer is used to isolate the detector circuitry from the track power circuit.

  The circuits on this page are for an Infrared - Proximity Detector using the Vishay Electronics - TSOP4830 "IR Receiver Modules for Remote Control Systems".

  The circuit shown on this page allows inexpensive digital multimeters to measure currents in DCC systems. The 2010 circuit is designed to use a 20 milliamp DC milliammeter to monitor the current but other types of meters could also be used with this circuit.

  This page features a circuit that has twenty open collector outputs that turn on one at a time in a continuous sequential manner. The circuit make use of the 74LSxx family of TTL integrated logic devices. The circuits are designed to drive light emitting diodes or low current, low voltage incandescent lights but can also drive other loads of up to 80 milliamps.

  The circuit breakers on this page make use of the Zetex - ZXCT-1009 "High Side Current Monitor' integrated circuit. The circuits have variable trip current settings and are designed for low current applications.

  Two circuit breaker designs are shown; The first has its power isolation device on the Low or common side of the circuit while the second has it isolation device on the High or supply side of the circuit. Both designs use MOSFET isolation devices.

  The circuits on this page are switch machine drivers that can be used to operate Stall-Motor type switch machine motors. The circuits use LM324 Quad or 358 Dual operational Amplifier chips to provide a PUSH-PULL output to reverse the polarity of the supply to the switch machine motors.

  "AT" type computer power supplies are often used by model railroaders to provide accessory power for their layouts. These supplies are reasonably inexpensive due to their age and have been removed from old personal computers.

  This block occupancy detection circuit uses a current sense transformer to isolate the detector circuit from the track power circuit. The output section of the circuit takes its power from an external power supply and uses a LM555 timer to provide the release time delay and both an Open Collector and Bipolar output each detector.

  Two block occupancy detectors using diodes and voltage comparators.

  This page presents block occupancy detector designed for general purpose use on systems where the polarity of the power to the track is reversible.

  This page is about a block occupancy detector that uses an optoisolator to electrically separate the track from the detector output. Four variations of the detector are shown.

  Some simple signals circuits that do not have pages of their own.

  This page shows a less expensive alternative to screw type terminal blocks for use on printed circuit boards. These are described as "Push-In Terminals for 0.042" Dia. Holes" and require soldering of external connections.

  The images shown on this page show circuits that can used to measure and record with a LEGO® RCX Brick that comes with the LEGO® MINDSTORMS and LEGO® ROBOLAB robotics sets

  The circuit on this page is for a rechargeable battery tester using a LEGO® RCX Brick to gather voltage verses time data and then upload the data to a PC using the ROBOLAB Software.

  This page features a replacement circuit for the LM3909 LED Flasher / Oscillator. The replacement circuit uses discrete components and is essentially the same as the internal circuit of the LM3909.

  This is an inexpensive way to make a stepped resistance box using a Single Pole - Twelve Position rotary switch and eleven resistors for each switch.

  This pages in this section of the site will present basic information about electronics for Model Railroaders. Pages will be posted with information on various components and simple circuits that a model railroaders are likely to use in their hobby.

  These circuits allow an ON-ON type DPDT toggle switch to control a twin coil switch machine motor. The handle of switch can then be used to indicate the route selected. The circuits are also able to control LEDs that could be used to indicate the selected route.

  This circuit allow an ON-ON type DPDT toggle switch to control a single coil switch machine motor such as those made by Kato®. The handle of switch can then be used to indicate the route selected. The circuit is also able to control LEDs that could be used to indicate the selected route.

  This circuit is for a "F.R.E.D." that is designed to be used with DCC control systems. The circuit is based on the LM555 timer chip.

  The circuit on this page is a 6 Aspect driver for a bicolour LED type Searchlight Signal. The available signal indications are; SOLID - RED, YELLOW, GREEN, and FLASHING - RED, YELLOW and GREEN. The circuit can also turn the signal OFF for approach lighting if desired.

  This page attempts to show the voltage waveforms associated with model railroad DCC systems as they would be seen with an oscilloscope. Also methods of measuring DCC system voltages and currents are shown.

  This page shows schematics and diagrams for a MiniDCC© system that was built for my personal use.

  This page features schematics and diagrams that are for use with the MiniDCC© system. - A DCC ( Digital Command Control) do-it-yourself project....

  This page features H-Bridge circuits used for controlling direct current motors. Several designs are shown using both CMOS and bipolar power devices.

  This page presents a new version of the - 'Modernized "Toy" Throttle' circuit that is shown on the 'Various Transistor Throttles' page at this site.

  This version was specifically design to be used by a handicapped person and is controlled by a single axis joy stick that operates microswitches at each end of its arc of travel.

  This circuit controls a Searchlight type signal head and produces solid - RED, YELLOW or GREEN indications.

  This circuit would be used to hold a BLOCK OCCUPIED condition as a train passes out of the block even if the normal detector is not sensing a train.

  The calculators on this page can be used to find current limiting resistors and currents for Light Emitting Diodes.

  The first calculator determines the resistance for a desired LED current while the second calculates the current for a given resistance.

  Some power supply and control options for Stall-Motor switch machines

  This page shows some methods of track routing control for Stall-Motor type switch machines. The principle method uses a 2 Pole - Multi Position rotary switch while an alternate uses optoisolators and transistors to select the routes.

  Some pictures of the tunnel boring machine used to dig the second railway tunnel under the St. Clair river and between Sarnia, Ontario and Port Huron, Michigan.

  This page presents general information and tips for the LM555 timer. If you would like to try any of these ideas please take time to do some experimenting before using them in an actual circuit. All of the solutions on this page can be applied to the LM556 Dual timer chip as well.

  Also on this page are calculators that will give the output times of LM555 timers for a given set of component values.

  This page presents a low tech, low cost and reasonably simple automatic reversing circuits. They uses toy train set power packs to control the top speed of the shuttle while diodes in the track circuit provide a method of stopping the shuttle at the ends of the track as well as crude control of the trains acceleration and deceleration.

  This page is for an automatic direction reversing circuit that will control the point to point operation of a "shuttle" such as an RDC car or a short train. The shuttle will travel from one end of the track to the other wait for a preset time and then return to its start point, wait and then repeat the cycle.

  This page is for an automatic direction reversing circuit that will control the point to point operation of a "shuttle" such as an RDC car or a short train. The shuttle will travel from one end of the track to the other wait for a preset time and then return to its start point, wait and then repeat the cycle.

  The circuit is also capable of being controlled by one or more automatic station stops as the SHUTTLE travels along the track.

  The circuits on this page are basic designs for "Diode Matrix" switch machine control systems that can be used to operate "Stall-Motor" switch machines in 'Ladder' type storage yards or other multiple turnout areas.

  The driver circuits themselves use LM556 dual timer chips to reverse the polarity of the voltage to the switch machine motors.

  The circuits on this page are switch machine drivers that can be used to operate Stall-Motor type switch machine motors. The circuits use LM556 dual timer chips to provide a PUSH-PULL output to reverse the polarity of the supply to the switch machine motors.

This train detector makes use of hand held laser pointer devices that are widely available to detect trains over long distances.

  This page is about automatic reversing loop control circuits. The first switch machine controller is very basic. More complicated circuits will be added as they can be thought up and tested out.

  The "Automatic Station Stop Circuit" brings a train to a station stop in two braking steps and then sends the train on its way after a set period of time.

  The first braking step slows the train gradually until it is at the station. The second brake step then stops the train just quickly enough to allow the first or second coach to stop in front of the station.

  This page features a simple, three IC unipolar stepper motor driver that can be used to drive relatively low speed applications at currents up to 1 ampere per phase. The circuit is made with parts that are available from a variety of sources.

  This page features a Bipolar stepper motor driver using three ICs. The circuit can be used to drive relatively low speed applications at currents up to 1.0 ampere per phase. The circuit uses parts that are available from a variety of sources.

  This page features basic, visible light photodetector circuits that can be used to detect trains. These methods would normally be used with the photo sensor mounted between the rails.

  This page presents various capacitor discharge power supply circuits for use with twin coil switch machine motors. Also shown are some optional wiring methods that can be used to enhance the availability and control of these supplies.

  The following diagram shows the pinouts for some of the integrated circuits and transistors used on these pages.

  This page presents information on infrared - 'Above And Across The Track' train detection circuits. The circuits are designed around the LM339 comparator chip and can use a wide assortment of matched infrared - emitter / detector pairs.

  The following are Low Power - Grade Crossing Flasher circuits based on the LM555 and LM556 timer chips. They are designed to drive Light Emitting Diodes but could be used to drive low current incandescent lamps.

  Here is a way to use old wire coat hangers to make simple and efficient wiring harness guides that can help keep your layout wiring neat and tangle free.

  This page features a photo and schematic from an article that was published in the August 1994 issue of Model Railroader Magazine. The article was titled "Build a model railroad odometer car".

  The following is a method to allow day and night detection using Infrared/Visible light sensitive phototransistors and a simple LM339 voltage comparator circuit.

  The Crossing Diamond Protection circuit is designed to prevent collisions where one rail line crosses another. Using phototransistor sensors to detect a train the circuit will disconnect the track power from the line that crosses the occupied line.

  The circuits presented here will prevent turnouts from being thrown while a train is on the switch, ideal where the switch cannot be seen by the operator. They use phototransistor sensors to detect the train and have a short time delay to compensate for gaps between cars. The circuit can also be used to protect crossovers and ladder tracks with the addition of more sensors.

  This is a circuit that will give an audible warning that a train is entering a particular section of track. The detector also has a LED that indicates when a train is entering or leaving the block.

  The drawings and photos below are for an operating incline railway that was built by the London Model Railroad Group for its 'O' scale model railway club located at London, Ontario, Canada. This is a single car model loosely based on a double car incline that operated at Port Stanley, Ontario.

  This page will show a number of variations on DC, transistor type throttles. The throttles range from 'tried and true' types to 'experimental' designs.

  The schematic above is of a Three Terminal Regulator (TTR) design based on a LM350K regulator which has a 3 Amp current rating as opposed to the LM317K with a 1.5 Amp rating.

  The following is a schematic drawing of a Silicon Controlled Rectifier type throttle for use on larger scale model railroads. Three versions of this throttle are shown on this page. They are not sophisticated designs but work well and are tough and reliable.

  The following are examples of home made solid state relays that could be used to replace mechanical types in many model railroad circuits.

  The 5 Times Around circuit was designed to automatically let an N Scale locomotive and car travel around a loop 5 times and stop for approximately a minute and then repeat the cycle.

  This page will provide some basic information about voltage comparator integrated circuits and and to act as reference material for other circuits. These circuits are based on the LM339 Quad Voltage Comparator chip.

  The circuits on this page are for various type of voltage regulated power supplies.

  The Circuit is for a 'Shunt' type ammeter that allows a meter movement with a small current rating to be used to measure a much larger current. In this example 1 milliamp through the meter coil will represent 1.5 amps by shunting most of the current through the 0.1 Ohm resistor.

  Some diagrams related to various aspects of science in general.

  The circuits in the following list do not have a detailed page dedicated to them. The schematics have little, if any explanation accompanying them. Some of the circuits are experimental in nature.

  The circuits in this group are:

1. Prefab Infrared Position Sensors - January 2019

2. Op Amp Voltage Divider

3. Common Capacitor Switch Machine Power Supply Test

4. Fixed Current - Solenoid Type Switch Machine Power Supply

5. Toggle Switch And LEDs For Flieshmann Switch Machines

6. Parallel Transformer Secondaries Phasing

7. RC Servo Motor Test Circuit (LM555)

8. Circuits That Have Been Reimagined

9. LM3914 - 10 Step Sequential Traic Trigger Driver

10. Simple Yet Functional Grade Crossing Flasher Circuit

11. Light Range Response Test Of An ALS-PT204-6C/L177 Ambient Light Sensor

12. Multiple Location Control For Single Coil Switch Machines - 2016

13. Multiple Location Control For Twin Coil Switch Machines - 2016

14. Hall Effect Switch - Turnout Position Detector

15. Tri-State Bridge Circuit

16. Bicolour LED Signal

17. Photo Sensor - Direction Sensing Circuits

18. Traffic Light Control Switching Circuit

19. Red / Green Bipolar LED Signal Controlled By SPDT Contacts

20. Cascade Delay Circuits Using 556 Slow-Motion Switch Machine Drivers

21. Common Cathode LEDs To Common Anode LEDs Signal Driver Adapter

22. Ir Receiver Modules for 37 to 58KHz

23. Trackside Camera Flash Circuit (LM555)

24. HIGH or LOW power switch

25. DCC Booster Anti-Fault Transition Block

26. Ash Pit Dimmer

27. 2 Sets Of 2 Inputs To 4 Discrete Outputs

28. Roundhouse Track Power Cutoff Circuit

29. 7474 Bipolar Stepper Driver Generators

30. DCC - Inrush Current Limiter

31. AC Only - Block Occupancy Detector

32. ULN2803 H-Bridge Circuit

33. 3 Level Battery Voltage Alarm

34. Low Voltage Power Supplies For LEDs Or Lamps

35. Lighting Circuits For Locomotives

36. Current Regulators For Light Emitting Diodes

37. High Current Switch Machine Motor Driver    (Fulgurex® Machines)

38. PUJT & Voltage Comparator - Power On - Delay Circuits

39. PIR Video Camera Control

40. Team digital - SCR16 - Twin Coil Switch Machine Adapter

41. N.O. Magnetic Reed Switch ON /OFF Circuit (SCR Equivalent)

42. Preselect Twin Coil Switch Machine Circuit

43. UNIPOLAR Stepper Motor Driver - Power Miser Version

44. Model Railroad - Infrared Proximity Switch (2005)

45. Back And Forth Stepper Motor Driver

46. 5 Second Ramp Generator

47. LM311 Thermostat Circuits

48. Adding Meters to DC Throttles

49. DCC To DC Power Supplies For Accessory Circuits

50. Train Mounted Camera Battery Charger

51. 10, 8 And 6 Step LED Circuits (CD4017)

52. LED Out Circuits For Tortoise Switch Machines

53. Snubber Diodes Across Relay Coils

54. School Bus Signals Circuit

55. Grade Crossing Bell Ringer (LM555)

56. Using Common Cathode Or Anode Leds As Bipolar LEDs

57. Transformer Secondary Voltage Reduction

58. Incandescent LED Circuit

59. Bad And Good Circuit Board Solder Joints

60. High Side Current Monitors (ZXCT-1009)

61. Light Activated Detector Circuit (LM393/LM555)

62. Special Function Timer Circuits (LM555)

63. Timed DC Throttle

64. Various LED Blinker Circuits

65. Finding Bad Joints In Track Wiring

66. Current Vs. Voltage For Various Automotive Lamps

67. Timed Uncoupling Ramp Driver (LM555)

68. Grouped DCC Block Occupancy Detectors

69. High Impedance Voltmeter Adapter

70. Finding The Resistance Of Meter Coils

71. DCC - Zero Stretching Simulator (LM555)

72. Push Button Stop / Start Motor Control Circuits

73. Colour Shifting for Bi-Colour LED's (LM555)

74. Using 1 Transformer For 2 Throttles - Why It Cannot Be Done

75. CA4060B Timer Circuits

76. Low battery Voltage Cutout Circuits

77. First Across The Line - Race Timers

  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.

  All HTML code, images, and page design, hereafter referred to as "content," contained within this site are the copyrighted property of Rob Paisley and shall be acknowledged as the copyright holder and author.

  Unless specifically stated, Rob Paisley grants no license to any party for the use of the content in this site for the manufacture and sale of goods, nor any other commercial utilization.

  Rob Paisley assumes no liability for any damages, direct, or consequential, which may arise from the dissemination, application, or misapplication of the content contained in this site. The User of the information provided in this site assumes all responsibility for any damages, direct or consequential, which may arise from its use. Rob Paisley retains the right to alter the content within this site at any time without notice.

  References to registered trademarks within this page are provided for informational use only, and are not intended as an endorsement for any service or product. Any such trademarks are the property of their respective owners.

  By clicking the links on this site, you, the User agrees to the above stated terms.

Recent Revisions And Updates To This Site

Triple - Servo Motor Driver Circuit (LM556) (PCB) Posted - February 2019

556 Timer Stall-Motor Switch Machine Drivers Added to - February 2019

3 Light - Model Railroad Signal Driver New Twin Circuit Board - November 2018

Circuits Without Detailed Pages Of Their Own <--> Full List of Circuits with links Here

• Prefab Infrared Position Sensors - January 2019

• Op Amp Voltage Divider

• Common Capacitor Switch Machine Power Supply Test

• Fixed Current - Solenoid Type Switch Machine Power Supply - March 2018

5 Amp - DCC Ammeter - Panel Meter Information Added - March, 2018

555 Timer Circuits Page - Section 45 Added March, 2018

Rapido RailCrew Switch Machine Power Supplies

Controlling Single Coil And Twin Coil Switch Machines Using SPST Toggle Switches

Controls For Single Coil Switch Machines Using Push Button Switches

4 Track - Switch Machine Ladder Matrix Using DPST Push Button Switches

Capacitor Discharge Power Supplies For Twin Coil Switch Machines

Interesting Track Arrangments Added To - January 2018

Power Supplies And Safety

London Model Railroad Group

Early Film Of The Old St. Clair Tunnel Starting At Minute 3:58 (Youtube)

Raking Leaves (Youtube)

19 January, 2019