Published:2013/6/7 21:19:00 Author:muriel | Keyword: Simplified Incline Railway, Control Circuit Schematic
IC 3 is part of the L.M.R.G. circuit and therefore was left in for this article. IC 3 can be omitted from the circuit and the mechanical contacts connected directly of the bases of Q1 and Q2 if desired. This would simplify the circuit but would not change its operation in any way. A schematic of the circuit without IC 3 follows. (View)
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Published:2013/6/6 21:00:00 Author:muriel | Keyword: Incline Railway, Control Circuit
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Published:2013/6/6 20:59:00 Author:muriel | Keyword: Audible Train , Approach Warning Circuit
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Published:2013/6/6 20:57:00 Author:muriel | Keyword: Toggle Switch Type, Protection Circuit
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Published:2013/6/6 20:56:00 Author:muriel | Keyword: Push Button Type, Protection Circuit, 'SCR' Output
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Published:2013/6/6 20:56:00 Author:muriel | Keyword: Push Button Type, Protection Circuit , 'Relay' Output
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Published:2013/6/6 20:55:00 Author:muriel | Keyword: L.M.R.G., Diamond Protection Circuit Schematic
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Published:2013/6/6 20:54:00 Author:muriel | Keyword: L. M. R. G., Diamond Protection Circuit
The original Crossing Diamond Protection circuit is used in several places on the London Model Railway Group's - O Scale layout. The first installation was at the main line and trolley crossing. In this location the main line cab operators cannot see a trolley approaching until it is just inches from the diamond.
The circuit shown here is a later and simpler version of the protection circuit. Included are signal lights, these are optional but do indicate who has the diamond.
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Published:2013/6/6 20:54:00 Author:muriel | Keyword: DCC BOD , Diamond Protection Circuit
The circuit in the first schematic is for a diamond protection circuit that used two transformer type DCC Block Occupancy Detectors.
NOTE: if there is a car in the protected section but it is not drawing any current the diamond will not be protected. With photosensors, if a car is on the diamond it will be seen by the circuit at all times.
The train must have detectable cars at least at both ends and the block must be as long as the longest train. (View)
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Published:2013/6/6 20:53:00 Author:muriel | Keyword: Day and Night, Detector Circuit
The detector for this circuit uses a voltage comparator the same as those on the Visible and Infrared Light Detectors page at this site.
The major change is the mounting of infrared emitters mounted at ceiling height above the detectors phototransistor. (View)
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Published:2013/6/6 20:51:00 Author:muriel | Keyword: Model Railroad, Odometer Car Schematic
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Published:2013/6/6 20:51:00 Author:muriel | Keyword: High Current , Crossing Light Flasher , LM556
This following circuit shows a simple grade crossing flasher with enough current capacity to drive 12 Volt lamps with 2 Amps current draw. The circuit could be used for open house displays, etc.
The flasher is driven by an LM556 dual time configured in a Push-Pull arrangement.
The flash rate can be adjusted by varying the value of the 500K ohm variable resistor. The flash rate is calculated as being from 0.54 to 3.1 Hertz.
The only real concern with this circuit is the need for a 12 volt power supply large enough for the current required by the lamps. The #1156 automotive lamps specified are rated at 2.1 amps but as only one light is on at a time the current draw for the circuit would be just slightly above 2.1 amps. Other lamps such as the #1141 draw less current.
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Published:2013/6/6 20:50:00 Author:muriel | Keyword: Push-Pull, Crossing Light Flasher
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Published:2013/6/6 20:50:00 Author:muriel | Keyword: Synchronous Crossing Light Flashers
In the synchronous flasher control the oscillator is running at all times and the power to each set of flashers is turned on or off by the control circuit for that crossing. This allows any number of flasher sets at different crossings to controlled individually and yet flash in unison.
Two versions of the flasher output control are shown.
In OUTPUT 1 the lights are turned on when the control circuit goes to the common of the circuit.
In OUTPUT 2 the lights are turned on when the control circuit goes to the positive supply of the circuit or some other supply source.
In either case the PNP and NPN transistors above and below the LED's are turned on and the crossing lights will flash.
IF more than one set of flashers is used at a particular crossing the LED's could be wired in series so as to keep the number of output control circuits to a minimum. This is shown on the basic flasher schematic.
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Published:2013/6/6 20:49:00 Author:muriel | Keyword: Basic Crossing Light Flasher
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Published:2013/6/6 20:48:00 Author:muriel | Keyword: 4 , Infrared Detectors Schematic
The schematic shows how the LM339 can be used to build a multiple detector unit.
In order to reduce on the total current needed for the circuit the infrared LED's can be wired in series and the value of the series resistor adjusted to supply the needed current. In this way the LED's use the same 17 milliamps instead of needing 17 milliamps each.
The parts values shown on the schematic are guidelines that should work in most situations but may have to be adjusted for your particular needs.
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Published:2013/6/6 20:47:00 Author:muriel | Keyword: Long Range, Track Infrared Detectors
The method shown below has been tested with sensor gaps as wide as 12 inches but a distance of 8 inches or less is more practical.
There is also a method that can be used for longer range across track detection that could be used for yard throats. A detector circuit of this type is in use at the London Model Railroad Group's club layout and spans seven O Scale tracks using one infrared LED and a lensed phototransistor.
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Published:2013/6/6 20:47:00 Author:muriel | Keyword: Basic Infrared, Detector Schematic
This page presents information on infrared - Above The Track and Across The Track train position detection circuits. The circuits are designed around the LM339 quad comparator chip and can use a wide assortment of matched infrared - emitter / detector pairs.
The circuit bellow is the basic voltage comparator based detector circuit using the LM339 Quad or LM393 Dual comparator ICs.
The LED will turn on when the infrared beam is broken. The value of the resistor R1 determines the sensitivity of the phototransistor Q1. In most cases a value of 1 Meg or 470K ohm with good results but every situation is different and some experimentation might be needed.
Circuit Operation - When a train breaks the infrared beam the phototransistor will conduct less current. The voltage at the MINUS input of the comparator will rise above the reference voltage at the PLUS as determined by R3 and R4. The output of the comparator to turn ON and the LED will be lit. (View)
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Published:2013/6/6 20:46:00 Author:muriel | Keyword: LM339, quad compartor , pinput diagram
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Published:2013/6/6 20:45:00 Author:muriel | Keyword: LM339, quad compartor, pinput diagram
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