The APB2 -Absolute Permissive Block Signaling System

New for 2011 - Available July 2011

page under construction - keep checking back here, it'll be complete soon!

I started to design this circuit back in 2001. It's been an "on again, off again" project, but now it's finally done and it works like a charm.

Have you taken a good look at the model railroad traffic management signaling systems out there recently? Nice stuff, however, it's just waaaay too complicated. You want a system that's easy to install and easy to maintain, right? Do you have the time, the patience, and the money, to install a huge computer interface with 100% prototypical operation? Or can you deal with a system that's functionally correct for modeling?  I've been working on this system for years, on and off, and I've finally nailed it. This is a very simple system to install, yet it emulates the Absolute Permissive Block signal system quite accurately.  Before we get into the actual circuit, lets get familiar with some of the operational aspects of APB signaling.


 

The APB2 system currently supports the following signal rules

9.50 (230) - Clear. Proceed with at least two clear blocks ahead. Green

9.54 (234) - Approach Medium. Proceed prepared to pass next signal not exceeding 40 MPH. This indication basically means that the next signal indication to be encountered is Approach. Flashing yellow

9.56 (236) - Approach. Proceed prepared to stop before any part of train or engine passes the next signal. Reduce speed to 40 MPH or less. This indication means that the next signal indication to be
encountered is Stop or Stop and Proceed.
Yellow

9.61 (241) - Stop and Proceed. Stop, then proceed at restricted speed. This is known as a permissive stop. Red (w/mileage marker on mast)

9.62 (242) - Absolute Stop. Stop before any part of train or engine passes the signal. This is known as an absolute stop. Red (w/"A" on mast or w/o mileage marker)

Plans are in the works for the DRA1 - Diverging Route Adapter interface card to provide

9.57 (237) - Diverging Clear. Proceed on diverging route not exceeding prescribed speed through turnout. Red over Green

9.58 (238) - Diverging Approach Medium. Proceed on diverging route not exceeding prescribed speed through turnout prepared to pass next signal not exceeding 40 MPH. This indication means that the next signal indication to be encountered on the diverging
route is Approach. Red over
Flashing Yellow

9.59 (239) - Diverging Approach. Proceed on diverging route not exceeding prescribed speed through turnout prepared to stop at next signal, reduce speed to 40 MPH or less. This indication means that the next signal indication to be encountered on the diverging route is Stop or Stop and Proceed. Red over Yellow

 


 

FOLLOWING MOVEMENTS

Scroll down and observe the light blue train as it is followed by the dark blue train in figures 1 through 7. Watch the signals and how they display in an Absolute Permissive Block system

 

 

 

 

 

 

 


 

OPPOSING MOVEMENTS

Figures 8 through 11 show the signal aspects for opposing movements. Observe the block signal aspects as the blue train and orange train approach the siding from opposite directions. Double approach signals (yellow) at the headblocks will flash. With this system you will have a fully automated traffic management system. Follow the signal rules and you'll never again have unresolved meets!

 

 

 

 


 

THE APB2 PRINTED CIRCUIT BOARD - A "PLUG AND PLAY" SYSTEM

The printed circuit board measures only 2" X 3". But don't let it's small size fool you. This circuit is a complete Absolute Permissive Block signaling card and is capable of powering up to 2 pairs of 3 aspect signals within a block of track. That means you'll be able to use a set of signals at the each end of a block and have a duplicate set of outputs available for schematic or fascia indicators! Let's look at the different features. 

- APB2 circuit cards are a complete block detection and signaling system. In a multi-block environment each card will sense direction of travel and traffic conditions and activate the appropriate signal aspects. All card to card (block to block) communication is handled through standard 10 conductor IDC ribbon cable and terminations. You won't find your self asking "where the heck do all these wires go?"

- Setup consists of wiring to a source of 12VDC power and inserting the cards in your track power feed lines. Once this has been accomplished you will be able to check the performance of your system and assign "TUMBLE" and/or "DOUBLE APPROACH" functions using the solderless jumpers supplied with each card. The on-board status indicators will show you signal displays and affirm that the direction of travel is correct.

- The APB2 system cards can be configured at manufacture to accommodate COMMON ANODE LED or COMMON CATHODE LED signals. 12V incandescent lamp signals can be used with either configuration. Check with the manufacturer of your signals if you are not 100% clear on what type you have. On-board current limiting resistors for each set of signals ensure that you do not accidentally damage your signals and provide 10ma operating current for LED signals. These resistors can be bypassed if you prefer to use outboard limiting resistors or use incandescent lamp signals. Each signal output is capable of supplying 250ma of continuous current to signals. Be sure to order the correct card configuration to match your particular signals. 2 pairs of identically functioning outputs labeled "1A & 1B" and "2A & 2B" are available at each end of the block allowing you to use trackside signals and a duplicate set of signals to display in your control panels or fascia, and you won't have to figure out a whole lot of wiring to make it happen! NOTE - APB2 cards are not supplied with connectors for signals. You can, at your option, install any 0.1" pitch SIL or DIL header and plug combination. Solder signal wires directly to the APB2 card for a permanent installation.

- The heart of the system is the PIC16F627 microcontroller chip. This part is socketed for easy removal and replacement and can be re-programmed in the future. You will receive lifetime no-charge updates to the firmware. Simply remove the chip and send it in. It will be returned to you with the new code programmed. When updates are available it will be posted on this page.

 



 
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