Wiring an Atlas 6924 N-D Board w/ #57 Switch Control

Are you planning on using the closure rails?

Jan

Stewart - Just starting to wire my layout and am practicing on a couple of 072 atlas switches joined to form a simple (and short) siding.  I have the 6924 non-derail board and a dwarf signal kit 6931 which comes with a circuit board.  After looking at the Atlas wiring instructions for this combination, it appears I do not need the board supplied with the 6931 kit because I should be able to control the dwarf signal directly from the 6924 - J3.  Can you confirm this? That is correct, be sure to enable jumper JP1.   Com1/C1(1)/C2(1)Terminals can not be used for anything else.

I used the small boards provided with the 6931 dwarf lights for two reasons.

(1.) My 6924 boards are centrally located. It was easier to hook the 6931 dwarf lights directly to the switch motor as the diagram shows.

(2.) By not using the Com1/C1(1)/C1(2) relay for the dwarf lights, it was still available for power routing.  Some of my switch cross over combinations required the used of both relays on the board, there were two track circuits involve in the cross over.

A few more questions - The instruction say the 6924 will work for 2 switches, but I don't think I see how to wire a second switch (Paired cross over switches (2)), is where this function is normally uses.  Both switches have to be either diverged or straight at the same time.  The Outputs from the 6924 board can power both switches at the same time either Through or Out. It is interesting to note that You will probably not have to hookup the diverge non-derail input for a very short cross over.     and last, if I am reading the diagram right, I must connect 2 wires to the isolated rails right near the switch convergence, which seems like last second switching when the derail detection occurs.  Is there a way to move detection out further with an isolated rail prior to actually getting on the switch track?  Yes, You can cut an isolated rail section further back on the track.

Between the two switch motors to the right are two isolated sections for the (3way) switch pictured.  Note the small white piece of styrene used when the Gargrave track was cut to provide the isolated section. The isolated sections are non-derail inputs for the left "Y" and the right "Y" of this three way switch.  Note that the two isolated sections are staggered, you need outside rail common via the train axle to activated the non-derail.  Two isolated sections across from each other would not work.

 Usually this input location works well for quick-acting snap switches.  Slow moving tortoise switches may require either slow moving trains through the switch or as you suggested moving the non-derail input back away from the switch frog.

Thanks,

Mike Monjure

Sorry - One more question, when the derail is detected and it throws the switch, does it continue to pulse the switch each time a trailing car hits the isolated rail and if so, is there a way yo prevent that?  Usually the time delay built into the board will inhibit the pulsing and protect the switch motor from burn-out do to extended power.   

Just to make sure, are these the correct locations for the J1 - 1a and 1b leads to connect and do I need insulated rail joiners where indicated?

Though technically the answer is yes, you don't have to limit the size of the isolated section to the size of just one piece of track.  You can add another section of track and then place an insulated rail joiner on that piece of track.  You can make that isolated section of track as long as you want.  A longer section of isolated track will limit how often the circuit board relay trips.  If you just have a short section of isolated track, the relay trips every time a new truck passes onto that isolated section.  

Note that sometimes the rails marked in the picture can touch the frog.  Be sure that the rail sections are isolated. 

Yes, thanks.  I think this has been the source of my problem.  They are connected and the drawing on the Atlas diagram shows them as isolated.  Should have checked with a meter right out of the shoot.

You're welcome

Mike CT

Hey Gang,

I'm editing the post to make this tutorial a little more user friendly. This tutorial will assist in wiring the Atlas 6924 non-derail board with the Atlas #57 switch control. It will not cover powering the closure rails. I'll be breaking down the wiring into two parts covering power and common, and isolated rail detection and switch machine control. I'll also include a testing and troubleshooting section at the end should you encounter any problems as I did.

The wiring will follow Atlas' schematic with the following exceptions: the color of the wires will be different and all power will come from the accessory side of the transformer.

Materials Used

• Atlas 6924 Non-Derail Board
• Atlas #57 Switch Control Box
• Atlas #312 5 Conductor Ribbon Wire
• Barrier Strips

The 5 conductor ribbon wire is optional, but I found very useful. It provided 5 different colors which made keeping track of each wires function easier and helped reduce any confusion during wiring. The barrier strips are also optional. This was a personal decision of mine as I found it easier to assist in troubleshooting rather than splicing wires together and then having to undo the splice.

Wire Reference

• Power - Red (exception: red wire running from the switch motor to 6924)
• Common - Black
• Isolated Rail Detection and Direction Control -Blue and Yellow
• Switch Motor - Red and Green
• Switch Motor Common - Black 

The color scheme was changed to fall in line with my layout wiring in which red is used for power and black is used for common. It made more sense to me that if I were holding a red wire, it was meant to power something. If you already have a layout built and used different color wiring, simply substitute your wiring color scheme.

Wiring Power and Common

In order to operate, the 6924 n/d board requires a power supply of 6v - 22v AC/DC supplied to J6. I chose the accessory side of my transformer for all power inputs into the 6924 to eliminate the need for a second power source.

Power (red) is routed to the following terminals:

• 6924 terminal J1 - SW PWR IN
• 6924 terminal J5 - COM 2
• 6924 terminal J6 - PWR

Common (black) is routed to the following terminals:

• 6924 terminal J6 - COM
• #57 Switch Control terminal labeled C - Take special note and care when wiring to the #57. Connecting to the posts with the red X will damage the 6924 n/d board.
• Switch Machine terminal labeled BL

This tutorial only covers the use of one 6924. The 6924 can be daisy chained to supply power to additional 6924's. To enable this function, install the jumper on JP 1. refer to the Atlas instructions for further wiring. 

Isolated Rail Detection and Switch Machine Control

Through Route Detection (Yellow)

The through route isolated rail detection wire and the wire from the #57 switch control terminal labeled 1 will be connected. (In my case, I used a barrier strip.) The connected wires are then run to the 6924 terminal J1 IN A. Next, connect the #57 switch control terminal labeled 3 to the 6924 terminal J5 C1-2.

Diverging Route Detection (Blue)

The diverging route isolated rail detection wire and the wire from the #57 switch control terminal labeled 2 will be connected. The connected wires are run to terminal J1 IN B. Next, connect the #57 terminal labeled 4 to the 6924 terminal J5 C2-2.

Switch Machine Control (Red, Green)

Connect the wire from the switch machine terminal labeled G to the 6924 terminal J4 OUT A. Connect the wire from the switch machine terminal labeled R to the 6924 terminal J4 OUT B.

Testing and Troubleshooting

Before turning on the power supply, ensure the power is set to within the 6v - 24v range. (Since I am using TMCC, my power preference is 18v to keep things logical and in order for my taste. The transformers I will be using allow me to set a custom voltage. Other transformers may have a set output. Just ensure it is within range.)

Turn on the transformer and look for the LED located on the 6924. If it is lit, the 6924 is receiving power. If it is unlit, check for proper voltage and any loose connections.

Set the #57 Switch Control for the through route*. Move the lever to N** and press the activation button. The green indication light should be lit. If the red indication light is lit, reverse the wires to the 6924 terminal J5 C1-2 and C2-2. Cycle the #57 Switch Control by moving the lever to R**, press the activation button, and then move the lever back to N and again press the activation button. Once the green light is synced, check the points of the turnout. The points should be aligned as follows: green indication light with the through route and red indication light with the diverging route. If the points and indication lights are out of sync, reverse the wires to the 6924 terminal J4 OUT A and OUT B.

* The through route is the route the train would normally travel. In most cases, the through route would have the points set to straight and the diverging points would be turned out. In some cases, the modeler uses the points turned out as the through route and the points set as straight for the diverging route.

** For those of you asking what the N and R stand for, I had the same question and did a little investigating. N  "Normal" is the main track route and R "Reverse" is the diverging route. If you are looking for more information on CTC control, would like to build your own CTC panel, or want to look at some eye candy, the CTC Parts website is a great read.