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Ted Rapp's

Solid State Relay System
For Automatic Train Control

www.track2.com/rapp

This Ted Rapp web page consists of these 6 sections:

Purpose Of This Web Page:

This web page presents information on what I will refer to as the "Ted Rapp System". This is an alternate method of constructing relay logic type of automatic train control systems, used by Ted Rapp on his G scale railroad in New Jersey.

This system uses NIAS solid state latching & non-latching relays, Mintronics miniature reed switches, and Tortoise slow-motion switch machine motors; in place of the commonly-used LGB reed switches, switch motors, and relays.

Ted sent me a sketch that shows an example of how you wire these relays, so you can try using them for your own control designs. The advantages of this system is that the components are cheaper, may be more reliable, and should be easier to adapt to smaller scales.

Section 1. Sample Wiring Sketch

This sketch shows an Automatic Passing Siding, where 2 trains alternate running around the loop. Note that this sketch does not provide for any kind of slowdown section.

Item 1 -- Latching Relay

Item 2 -- Non-Latching Relay

Item 3 -- Reed Switch

Item 4 -- Tortoise Switch Machine Motor

Section 2. Possible Pros & Cons Of This System

Question: What are the possible advantages of this Ted Rapp system, versus using the more familiar LGB components?

Answer: The possible advantages are:
  • Components are cheaper cost.
  • The system may be more reliable.
  • Easier to adapt to smaller scales.

Question: What are the possible disadvantages of this Ted Rapp system?

Answer: The possible disadvantages are:
  • Tortoise switch machines should not be used outdoors
  • The components are unfamiliar to us; most of us have no experience working with them.
  • The solid state relays do not allow manual adjustment of the relay state when the control power is off. (With the LGB switch motors, you simply push the little "arm" to the other side when you need to manually change their state.)
  • The wiring may be a bit more complicated.

Question: What makes you think this Rapp system may be more reliable?

Answer: With the LGB system, the reed switch must conduct enough current to "push" the relay and switch motor to the new position. I.e., the current through the reed switch has to acutally move a mechanical mass of the switch motor mechanism, plus often the 1203 relay points.

The most common failure modes I have observed with my "Ingram Autocontrols" systems which use the standard LGB components are:

  • When the normally-open reed switch is activated (closed), you sometimes don't get enough "oomph" to fully throw the switch motor. (LGB's Booster addresses this problem.)
  • After you "crank up" the voltage so you get enough "oomph", after a while some of your reed switches may start sticking in the closed position. To correct this, you have to replace them.

With the Ted Rapp system, the reed switches need to pass only enough current to "notify" the solid state relay (they don't have to push any mechanical mass). So you can use 9 volts to reliably control the 12 volt relays, instead of the 18 volts - 24 volts we typically use to activate our LGB switch motors.

Question: Will this work with other scales, besides G scale?

Answer: This system should also be usable on O, S, and HO gauges.

The problem with adapting the LGB components to smaller scales, is getting the reed switch positioned "just so", and having a large enough magnet, to get sufficient "oomph" to activate the electromechanical relays. With the solid state relay, you should be able to use any reed switch in any position with any magnet that will activate the reed switch.

Question: Speaking of complicated wiring, brings up another question: Why would I even want to consider building one of this sytems, with all these wires, when I can now purchase an electronic "black box" that "does it all", and all I have to do, is hook up is half dozen or so wires?

Answer: The "black boxes" are fine. In fact, you could argue that they are superior, as some of them provide slowdown and accelerate features that gradually decrease and increase the speed of the trains. The only disadvantage of them is that if you want to modify it or need to repair it. and the person who made it is no longer in business, you may have a problem.

With these "homemade" systems, whether it be the "Ted Rapp style" or the "Ingram Autocontrols", you can probably modify it yourself or fix it yourself, since you have built it up piece by piece yourself, using fairly basic components.

Section 3. About This Wiring Sketch

Question: Why does this system operate on 9 volts?

Answer: The solid state relays are rated for 12 volts input to the coil. The reason Ted Rapp operates them on 9 volts, is that 9 volts is the maximum allowable voltage for the Tortoise switch machines.

If you were constructing a single-track automatic block (no switches and no Tortoise), you whould be able to operate the system on 12 volts.

Question: Where do I get the 9 Volts to operate this control system?

Answer: Ted Rapp says he uses inexpensive HO DC transformers, and just adjusts the voltage to 9 volts, or even slightly less.

He says you just have to be careful not to send more than 9 volts to the Tortoise switch motors, or they can be damaged by overstressing their internal gearing system, and then the gears start to slip.

The relays are rated for 12 volts DC, but he says they operate fine on 9 volts.

Question: Are there any other voltages that you can design this control system to operate on?

Answer: Ted says you can get these relays in 5 volt coil ratings also. He says the Tortoise switch motors will operate on 5 volts, but they just take a little longer.

Ted says he thinks using the 5 volt system versus the 9 volt system may make the reed switches last even a little bit longer. But currently he is using 9 volts.

Question: In the sketch, the reed switches appear to be on the side of the track, outside of the rails, not the center. Why is this?

Answer: Ted says you can place the reed switches on the sides of the track or in the centers. He says for G scale, he can use 5 different positions, so he can in-effect create up to 5 different signalling circuits that operate independently.

Question: What kind of a logic system does this sketch show?

Answer: The sketch shows what the "Ingram Autocontrols" refers to as an Automatic Passing Siding. This is where 2 trains operate. One train waits on Track 1 until the other train pulls in on Track 2. The train on Track 1 starts up and the train on Track 2 stops. They keep alternating. Note that this system in the sketch does not provide for any kind of slowdown section.

(You can view the logic diagram for this type of system by going to the Ingram Autocontrols web area titled "Section 1 Overview", scroll down to "Figure 1d -- Logic Diagrams For Automatic Controls", and on that figure find "Figure d -- How an Automatic Passing Siding Controls 2 Trains".)

Question: What if I want a wiring diagram for a different type of system, such as a single track block, or what some sort of slowdown section?

Answer: Right now this diagram is the only one we have.

Section 4. How The Components Operate

Question: What actually turns the track blocks On and Off?

Answer: The solid state latching relay--shown on the right side of the sketch--does this.
  • When the reed switch in Track 1 sends a pulse to the latching relay, it connects the common terminals (C) to the normally closed terminals (NC), which connects track power to Track 2 and disconnects Track 1.
  • When the reed switch in Track 2 sends a pulse to the latching relay, it connects the common terminals (C) to the normally open terminals (NO), which connects track power to Track 1 and disconnects Track 2.

Question: O.K, but what's not so obvious: How are the track switches controlled?

Answer: The solid state latching relay (shown on the right side of the sketch), holds the non-latching relay (shown on the left side of the sketch) in either the open or closed position.

This non-latching relay applies continuous current to the Tortoise switch machine, which causes the track switch to be in either the straight or curved position.

Question: You mentioned you're applying continuous current to the Tortoise switch motor. Doesn't This Damage It?

Answer: Tortoise switch motors are designed for this, and will not be damaged.

Question:. Can you describe what happens when an engine with a magnet passes over the reed switch in Track 1?

Answer: When a magnet closes this (normally-open) reed switch:
  • The reed switch in Track 1 sends a pulse of DC to the latching relay
  • The relay connects the common terminals (C) to the normally closed terminals (NC).
  • This sends ZERO current to the non latching relay (since there is no wire connected to the (C) terminal on this pole). Thus the non-latching relay remains in the normally OPEN position
  • This sends current to the Tortoise switch motor to set the switch to the STRAIGHT position
  • This routes the next incoming train onto Track 2.

Question: Can you describe what happens when an engine with a magnet passes over the reed switch in Track 2?

Answer: When a magnet closes this (normally-open) reed switch:
  • The reed switch in Track 2 sends a pulse of DC to the latching relay
  • The relay connects the common terminals (C) to the normally open terminals (NO).
  • This sends current to the non latching relay. Thus the non-latching relay held in the CLOSED position.
  • This sends current to the Tortoise switch motor to set the switch to the CURVED position
  • This routes the next incoming train onto Track 2.

Section 5. About Ted Rapp

Question: Who is Ted Rapp?

Answer: Ted Rapp is a G scale model railroader who has been using relays systeems for control for about the last 10 year.

Orignially he used Radio Shack relays, and made his own latching relays by wiring of non-latching relays (which is cumbersome). For about the past 6 years, he has been using the NAIS solid-state relays. He has used these relays systems with N, HO, O, and G gauge.

He used this solid state relay system to construct a automated 4-track Zellner Yard in May 1998. (Zellner yard is described in the Ingram Autocontrols section.) He also uses these relays to control other automated switching, plus automated raising and lowering of train shed doors.

Question: You said in the "Disadvantages" section that the Tortoise switch motors cannot be used outdoors? Does this mean Ted's G scale layout is indoors?

Answer: No, Ted's G scale layout is outdoors. But he has all his switches on a porch, so they are protected from the weather.

Question: What does Ted Rapp provide?

Answer: Ted Rapp provides information. He has simply given me (Jim Ingram) permission to put this information on this website, for the benefit of other "Autocontrollers" who may be interested. (He is not in either the equipment nor drawing business.)

Question: Can I talk to Ted Rapp if I have questions not answered on this web page?

Answer: You can telephone Ted Rapp, as long as you give him permission to return calls COLLECT if you get his answering machine.
Ted Rapp
314 Bridgeboro Road
Moorestown NJ 08057-1406
Phone (609) 235-1332 ; call 6 pm to 9 pm Eastern Time (fax 609-786-3220)

Section 6. Alternate 5 Volt Relays

Note that the wiring sketch shows 12 volt relays (operated at 9 volts). Ted Rapp says you can also use 5 volt relays (operated at 5 volts) as an alternate. The following specifications show part numbers for the 5 volts relays. (NOTE: I believe you can also obtain these relays in 6 volt models and other voltages as well.)

Item 1 (Alternate) -- Latching Relay

Item 2 (Alternate) -- Non-Latching Relay


7/1/98 -- Initial draft of Ted Rapp page

This page modified 10/09a/2003 by (bottom include)

JamesRobertIngram.com , Williamsport Pa, Voice Mail 570-322-7597