The single head target signal controller...
Well, this is the basis I got started with, for a ATC Controlled single, or any number of main track blocks, which are automatically controlled. I have uploaded a PDF file of the signal head controller, of which the whole concept is based upon.
In a signal controlled system, the object is obviously, to control the flow of traffic on track lines, to make it a safer, and more efficient means of transportation. Therefore, what was needed, was a way to have a long stretch of track, that could be controlled, as efficiently as possible, control the direction of the traffic to it's destination, and points in between.
In order to make this happen, there are several things that need to be monitored, and acted upon, when trains are in the block, and coming onto the controlled area. Now, CTC, is nothing more than a added layer, of the ATC track control system. This is why I started with the ATC type system, and then, added the same basic head controller to the CTC controlled points, as they will follow normal track occupancy zones, and relay the signals to them, by the dispatcher. I will explain this in detail, even more in another post.
Looking through the schematic, you will see 2 chips. inexpensive, and reliable, and already, they are a mainstay in the Model Railroad Hobby. The have been a constant source of dependability, and are commonly available. That would be the 74LS06, 74HC05, invertors. Simply put. If you have an input to the single gate of a 'HIGH', or +5vdc,(not actually the "1" and "0" voltage minimums, and maximums, but, don’t fret this, it will be self-explanatory further down the road. As I was stating, if you have a HIGH input, it will give you a LOW output. plain and simple. and vice versa. If you have a "0" (zero), or NO voltage,( its threshold is near the 2 volt input threshold for low), you will get a HIGH, or "1" output. There are several type of invertors. I ruled out the use of 74lLS04 invertors, because I found I needed a good strong voltage, for the length of ribbon cable, connecting all of the parts of the system.at that point, you should have a power connection, no fewer than every 5 feet of length, just to maintain an operating voltage, and current, to keep the system running properly, and avoid the normal voltage drops created by resistance of the wire, and connectors used. The amperage isn't very high, but, we HAVE to keep the voltage at above 5 vdc. You can use a PC (ATX) power supply, for +/- 12VDC, and it is around 8 amps, and the 5 volt supply is a 30 amp supply. Common, even today on many large and small computer systems.
Back to the signal head. The controller is an ATtiny85. It has 6 input/outputs, and looking at the data sheet, you can see the other pin assignments given each pin such a PWM,(Pulse Width Modulation), which is how your locomotives are controlled, but, that is only the program creating the pulses. In the signal system, you cannot use PWM, for controlling the signals LED's. It just causes them to DIM, as that is the basic operation of PWM.
Each ATC signal needs to output a couple of different signals, and monitor the INPUT of a few other signals, as well as each head output signal’s, determine the way the NEXT signal, and the PREVIOUS signal, so as to determine what aspects are going to be displayed.
These signals are as follows:
1.) NEXT BLOCK FULL - as an INPUT
2.) BLOCK FULL - as an OUTPUT
3.) BLOCK OCCUPIED - as an INPUT
4.) TRAFFIC DIRECTION - AS AN INPUT
5.) BLOCK OCCUPANCY - AS AN INPUT.
The LATTER, is a VERY important signal, as it monitors and controls the single head needs to operate correctly. Let me explain further.
6.) This is the LED driver output, that allows all three colors, RED - YELLOW - GREEN. It only takes on output line to do this. Don't worry, I also have the "G" and "D" type signal controllers too! They offer three outputs for RED, YELLOW and GREEN LED's.
BLOCK OCCUPANCY is what you need to monitor, so you can signal the other signal heads in the string, AND any CTC controlled signals, that are within that string. It is nothing more than a daisy chain connection, which is the same between every signal. It reads one, and responds with another signal, either HIGH or LOW, to each controller
I can't imagine most people on here NOT knowing what these signals are, because they have been in use for so long, by the Railroads, since the inception of auto, and CTC signals.
I will make the explanation short as possible, and if you need to know more I will be very happy to explain further, and I will elaborate more, as we move forward.
For example you have 4 blocks. Each block, each block has a signal controlling traffic, in BOTH directions. Now, I will touch a bit on that in the next few paragraphs. This system, IS BIDIRECTIONAL! Controlled by the "TRAFFIC DIRECTION" input, on each signal controller.
So for simplicity sake, lets say, your train is entering a ATC block. There is no one in the block ahead, so THAT particular signal, is telling the block signal, that it is "EMPTY" or 'UNOCCUPIED'. Therefore, the 2nd block signal sends a signal back to the 1st block, telling it..."I AM EMPTY, PROCEED". Figuratively speaking.
this signal is seen by the 1st block controller, and it checks the traffic direction, to see if we have a "RIGHTBOUND" traffic direction. I almost forgot. Normally, to keep things in perspective, the railroads refer to "RIGHTBOUND", and "LEFTBOUND". If you get a chance, you can look at a dispatch panel, and you will see what this looks like. This is an important signal that controls the WHOLE operation. If you have a RIGHTBOUND train, and the signal head controller tells the CTC block you went through to enter this 1st ATC block, the dispatcher, will not be able to set the traffic to the LEFTBOUND signal head, and it will stay RED, as LONG as the traffic direction is RIGHTBOUND. EVERY CTC CONTROLLER CONTROLS THE DIRECTION OF TRAFFIC FLOW. I will let that sink in, as I explain what happens, when traffic is cleared LEFTBOUND.
When a CTC controller is set to allow a movement of traffic, it will pull this control line either HIGH or LOW. I have made it so that the signal is NORMAL when it is HIGH, being, traffic is set in the LEFTBOUND direction. I must stress to you, this signal is very important, for bidirectional traffic movements. Each controller, sets this signal, when clearing a movement through a division, block, and dark area.( Dark areas are a section of track that is not signal controlled and needs a track warrant, in order to move into, or out of the siding safely. This signal, when HIGH, will keep ALL RIGHTBOUND traffic signal heads, in the STOP aspect, where it will remain, until the dispatcher clears a movement, in the LEFTBOUND direction. Each circuit board, has marked on it, LEFTBOUND, and RIGHTBOUND, so the reference is ALWAYS the same, no matter which side of the track you are looking at it from. This keeps the system in a string loop, and makes it run properly, and enhances the movement of trains it controls.
Traffic direction, is a JUMPER selected property, so that you can set all signals to the proper traffic direction, and should be set the same, for all signal controllers used in a string of blocks.
This signal to each head controller is the KEY, to the implementation, of the CTC controlled dispatch blocks. That will become clearer, when we get in to the CTC controlled block signals.
The block occupancy signal line is ALWAYS HIGH or a 1, unless there is a train in that particular block, and such, it is also, bidirectional. A train will be detected, going either direction, LEFTBOUND, or RIGHTBOUND.
This system, does not require fast processing of data, so there is no need to worry about high frequencies, interfering with ANYTHING you may want to use on your layout. It uses internal clock signals, and does not depend on any high speed digital signals for its operation. That makes it a simple, no timing operation, that is fast, and reliable every time.
I used open SOURCE, or OPEN COLLECTOR INVERTORS, because we have to be able to control a higher current output, so that the ribbon cable between them will not have a terrible voltage drop, between power connections. I stress, you should have a few power connections to each signal block, as you would for your track. POWER feeders are easy, and essential, to a flawless operation. I use my PC supply, and I drop several feeders to the signal and detector interfaces, in a controlled block. Now, I show 8 pin make headers as cable connections. You may want to know, that, this is not the only configuration, of plugs and sockets. I have boards already designed and working, using CAT 5 connectors, and plugs, as well as CAT 5 cable between each signal and block detectors. THIS makes it rather inexpensive. You can buy a hundred crimp CAT 5 plugs, and sockets, for pennies on the dollar, online. eBay is a good source, and they WORK GOOD!!
I used the male header blocks, to design a block occupancy system, so that I had an IR transmitter and receiver, every 11 inches, under my track. I had a follower board, as I will upload a picture of, every 11 inches between ATC or CTC signals, so that at least ONE car would cover and pull the BLOCK OCCUPIED line LOW when it was activated. I encourage you to experiment with this, if you can, to see how it works. The only way to get every controller to be able to control all of the feed lines, and utilize a good strong signal, I used a "WIRED OR" capability of the open collector, or open source device. That made this all possible, without many more wires and connections. Although I still used some f my ir detectors, I am switching over to the CAT 5, because it is a bit stronger, and wire size is almost DOUBLE what is used in ribbon cable. It was not designed for very long distances, although, adding power feeders cured that, it will make an easier connection, when using a single block occupancy detector. I will be uploading those interfaces, and block occupancy detector for DCC, in a few days, as the article is explored even more.
Hopefully, I am explaining this so that most can understand. I am NOT a great writer, I AM a good orator, and I AM very excited to be able to help anyone out, who may be interested.
AND for all of you old fogies, like myself, who do NOT understand all of this, PLEASE, tell what you do not understand, and I will be extremely happy to explain it in another way, so you grasp the operation. Knowing how the internals work, will not be of great importance to those of you who are electronically challenged. Don't worry, you need not be ashamed, I think it is very cool, to be able to help y'all, without confusing you with facts, just the operation phase you need to know!
Many blessings and Thank you for reading!!
Your friend in modelling...
Taz...
PS - My real name is Kim. Yes, I know, I had a tough time growing up with it, but, I survived, and learned valuable life lessons as well.... Sure glad I wasn't named "SUE"! lol!!!!
