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.
The circuits on this site are purposely designed to be as simple and efficient as possible. In most cases they perform only one function but do it well.
The circuits use basic electronics that the average person can find parts for and build on their own. Computers and microcontrollers have largely been avoided.
Some circuits and pages don't have a particular use but are meant only to be educational or informative.
Some of the circuits are of general interest, generally mine, and may be of little use. They are functional however and at the very least, a useful waste of my time.
A few 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 Holbourne Ave., London, Ontario, Canada. Public viewing nights are the first Tuesday of the month from October to May.
I am not an electronics professional, although I play one on the web, and only design these circuits as a hobby.
Therefore I can make no claims to the quality or usefulness of the circuits shown on this page. They should however work as stated and will not be dangerous to persons or property when used in their intended manner.
If you see any problems with the circuits or have any suggestions please let me know.
If you have questions, comments or need some help regarding the circuits on these pages you may contact me via email at: Rob Paisley. (firstname.lastname@example.org)
If this is your first visit to this site, please read the sections above for general information about the site. Thank you.
Pages in English and French are denoted by the addition of (E+F) at the end of their links.
These pages are best viewed with the browser of your choice and an open mind.
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.
This diagram illustrates the principle effect of rotating an arc excentrically away from a similar arc. The net result is an increasing gap between the circumfrences of the two arcs.Cam Action - Swing Gate Illustration
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.Garden Lights With LEDs
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.Unipolar Driver Information
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.Bipolar Stepper Information
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 type lighting for the Green signal.
The basic circuit can also be used for 2 Light signals, PRR - position light type signals and can be adapted for search light type signals that use bicolour LEDs.Block Signals Circuit Information
This circuit is for a switch machine controller for reversing loops. The circuit is light activated and designed to automatically operate stall type switch mahines.Switch Machine Controller Information
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.Traffic Light Driver Information
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.2011 - Grade Crossing Circuit Information
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.DCC Track Booster Information
This booster is designed to power stationary DCC decoders used to control off-track accessories, switch machines and signals.DCC Accessory Booster Information
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.Photo-Detector Circuit Information
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.Inverting Photodetector Information
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.Non Inverting Photodetector Information
This circuit is a driver for a mechanical - Grade Crossing Bell Ringer - that was originally built for the London Model Railroad Group.Bell Ringer Information
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.Circuit Breaker Information
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.Stepper Driver Information
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.4 Photo-Detector Circuit Information
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.Track Booster Information
In these circuits a transformer is used to isolate the detector circuitry from the track power circuit.Occupancy Detector Information
The circuits on this page are for an Infrared - Proximity Detector using the Vishay Electronics - TSOP4830 "IR Receiver Modules for Remote Control Systems".IR Proximity Detector Information
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.DCC Ammeter Information
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.Sequencing Circuit Information
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.Electronic Circuit Breakers Information
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.Switch Machine Drivers
"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.AT Power Supplies information
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.Block Occupancy Detector information
Two block occupancy detectors using diodes and voltage comparators.Block Occupancy Detector information
This page presents block occupancy detector designed for general purpose use on systems where the polarity of the power to the track is reversible.General Purpose Block Occupancy Detector information
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.Optoisolator Block Occupancy Detector information
Some simple signals circuits that do not have pages of their own.Miscellaneous Signals information
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.Push-In Terminals information
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 setsVoltage Recorder information
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.Battery Tester information
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.LM3909 Replacement information
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.Substitution Box information
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.Basic Electronics information
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.Toggle Switch Control information
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.Toggle Switch Control information
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.Flashing Rear-End Device information
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.6 Aspect - Searchlight Signals information
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.DCC Waveforms and Voltage information
This page shows schematics and diagrams for a MiniDCC© system that was built for my personal use.My MiniDCC© System information
This page features schematics and diagrams that are for use with the MiniDCC© system. - A DCC ( Digital Command Control) do-it-yourself project....MiniDCC© System information
This page features H-Bridge circuits used for controlling direct current motors. Several designs are shown using both CMOS and bipolar power devices.H-Bridge information
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.Joy Stick Controlled Throttle information
This circuit controls a Search Light type signal head and produces solid - RED, YELLOW or GREEN indications.Search Light Signal information
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.Block Occupancy Detector Helper Circuit information
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.Current Limiting Resistor Calculator information
Some power supply and control options for Stall-Motor switch machinesStall Motor Switch Machine Circuits information
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.Route Control information
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.Canadian National Railways - St. Clair River Tunnel Construction Photos
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.LM555 Timer information
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.Automatic Reversing Circuits - Inexpensive
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.Automatic Reversing Circuit - Mk IV information
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.Automatic Reversing Circuit - Mk VII information
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.Matrix Systems For Stall-Motor Switch Machines information
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.556 Switch Machine Driver information
This train detector makes use of hand held laser pointer devices that are widely available to detect trains over long distances.Laser Pointer Train Detector information
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.Automatic Reversing Loop information
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.Automatic Station Stop Circuit information
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.Stepper Motor Driver information
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.Stepper Motor Driver information
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.Photocell and Phototransistor - Detector Circuit information en français
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.Switch Machine Power Supply information en français
The following diagram shows the pinouts for some of the integrated circuits and transistors used on these pages.Integrated Circuit and Transistor Pinout diagrams
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.Above And Across Track Detection information
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.Crossing Light Flashers information information en français
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.Coat Hanger Cable Guide information en français
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".Model Railroad Odometer Car information
The following is a method to allow day and night detection using Infrared/Visible light sensitive phototransistors and a simple LM339 voltage comparator circuit.Day and Night Detection information
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.Rail Crossing Diamond Protection information
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.Turnout Anti-Derail Protection information
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.Audible Train Approach Warning information
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.Incline Railway Circuit information
This page will show a number of variations on DC, transistor type throttles. The throttles range from 'tried and true' types to 'experimental' designs.Transistor Throttle Circuits information (Top of Page)
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.TTR Throttle Circuit information en français
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.SCR Throttle Circuits information
The following are examples of home made solid state relays that could be used to replace mechanical types in many model railroad circuits.Solid State Relay information en français
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.5 Times Around Circuit information
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.Voltage Comparator information
The circuits on this page are for various type of voltage regulated power supplies.Power Supply information en français
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.Shunt Ammeter Circuit information
Some diagrams related to various aspects of science in general.Science information
The circuits in the following list do not have a specific page dedicated to them. The schematics have very little, if any explanation accompanying them. Some of the circuits are experimental in nature.
The circuits in this group are:
HIGH or LOW power switch
DCC Booster Anti-Fault Transistion Block
Ash Pit Dimmer
2 Sets Of 2 Inputs To 4 Discrete Outputs
Roundhouse Track Power Cutoff Circuit
7474 Bipolar Stepper Driver Generators
DCC - Inrush Current Limiter
AC Only - Block Occupancy Detector
ULN2803 H-Bridge Circuit
3 Level Battery Voltage Alarm
Low Voltage Power Supplies For LEDs Or Lamps
Lighting Circuits For Locomotives
Current Regulators For Light Emitting Diodes
RC Servo Motor Test Circuit (LM555)
High Current Switch Machine Motor Driver (Fulgurex® Machines)
PUJT & Voltage Comparator - Power On - Delay Circuits
PIR Video Camera Control
Team digital - SCR16 - Twin Coil Switch Machine Adapter
N.O. Magnetic Reed Switch ON /OFF Circuit (SCR Equivalent)
Preselect Twin Coil Switch Machine Circuit
UNIPOLAR Stepper Motor Driver - Power Miser Version
Model Railroad - Infrared Proximity Switch (2005)
Back And Forth Stepper Motor Driver
5 Second Ramp Generator
LM311 Thermostat Circuits
Adding Meters to DC Throttles
DCC To DC Power Supplies For Accessory Circuits
Train Mounted Camera Battery Charger
10, 8 And 6 Step LED Circuits (CD4017)
LED Out Circuits For Tortoise Switch Machines
Snubber Diodes Across Relay Coils
Ir Receiver Modules for 37 to 58KHz
School Bus Signals Circuit
Grade Crossing Bell Ringer (LM555)
Using Common Cathode Or Anode Leds As Bipolar LEDs
Transformer Secondary Voltage Reduction
Incandescent LED Circuit
Bad And Good Circuit Board Solder Joints
High Side Current Monitors (ZXCT-1009)
Light Activated Detector Circuit (LM393/LM555)
Special Function Timer Circuits (LM555)
Timed DC Throttle
Various LED Blinker Circuits
Finding Bad Joints In Track Wiring
Current Vs. Voltage For Various Automotive Lamps
Timed Uncoupling Ramp Driver (LM555)
Grouped DCC Block Occupancy Detectors
High Impedance Voltmeter Adapter
Finding The Resistance Of Meter Coils
DCC - Zero Stretching Simulator (LM555)
Push Button Stop / Start Motor Control Circuits
Colour Shifting for Bi-Colour LED's (LM555)
Using 1 Transformer For 2 Throttles - Why It Cannot Be Done
CA4060B Timer Circuits
Low battery Voltage Cutout Circuits
First Across The Line - Race Timers
N.B. - 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 "Above And 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.
All HTML code, images, and page design, hereafter referred to as "content," contained within this site are the copyrighted property of Rob Paisley, and can not, under any circumstances, be cached, retransmitted, copied, or altered without his explicit written permission, in which case, he shall be acknowledged as the copyright holder and author.
Unless specifically stated in a written contract, 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.
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Automatic Reversing and Station Stop Circuits - DWDC Output Schematic Added - April, 2013
Automatic Reversing and Station Stop Circuits - Circuit Boards Available - April, 2013
Circuits Without Pages Of Their Own <--> Full List of Circuits Here
HIGH or LOW power switch
Low Battery Voltage Cutout Circuits
Retrofitting Garden Lights With LEDs Using License Plate Lights - February, 2013
Cam Action - Swing Gate Illustration - February, 2013
556 - Searchlight Signal Circuits (PCB) - Updated - February, 2013
3 Light - Model Railroad Block Signal Circuit (PCB) - Updated - February, 2013
LM555 Timers - Circuits and Calculators - Section 37 Added - February, 2013
Various Transistor Throttles - Section 11 Added - January, 2013
2011 - Grade Crossing Circuit (PCB) - Updated - December, 2012
VT-5 DCC Block Occupancy Detector - Source for coils in Europe - October, 2012
Reversing Loop Switch Controller (PCB) - Added to - October, 2012
UNIPOLAR Stepper Motor Driver (2012) (PCB) - New - May, 2012
BIPOLAR Stepper Motor Driver (2012) (PCB) - New - May, 2012
London Model Railroad Group (2006)
20 April, 2013