LD (Loco Detection) v BD (Block Detection)

[RB51]

My visual detection is OK - at the moment - my concern would be my command interface recognising the event trigger and converting it to a digital component (I've got 10 of these already) instruction in time to prevent a collision. R-

[Fishmanoz]

Also, for BD, a loco is detected and then the system feeds commands back to not only the loco, but signals, points and any other device you have connected to your layout/system.

 

Is this what RM will do?

 

Yes it is hosh. If you are using RM, add a detector to your layout then right click on it to see all the options you have. Or go to one of the LD titled threads where the allowable commands are listed. 

[RB51]

That looks pretty impressive Phul. Do you mind if I ask a few questions?

 

1. Was the retro fit of sensors pretty straight forward? (I think I saw one in the embankment wall) what wiring is needed?

2. DId you get the Starter Kit? I imagine at 36 sensors you must have purchased a combination of sensor boards.

3. If you did get the Starter Kit, does that really contain all you need to get started? If, not, what did you have to get?

Thanks, R-

[hosh]

If I'm a customer I want the low cost option of LD that simply detects - never mind about tags, speed, direction.

 

Speed on the other hand I see as important to control. With clear blocks things seem simple but with several locos on a length of track, one running faster than another speed control linked with correct signal aspects, Y proceed with extra caution, YY proceed with caution, then reducing speeds accordingly aids to more realistic train control. Speed control to sidings, speed control in the blocks before sidings and stations etc, etc, will I think, be very important and with sensors in stations and sidings to stop locos, approaching at a suitable speed will mean the loco will stop more accurately in the same place each time. With the use of programmed routes stopping in the same place each time is very important. I think.

 

 

BD can do all this, but I do admit that for all the fiddly bits it would be good to have sensors, especially for sidings.

 

Btw, do we know whether the Hornby detectors will be wired or wireless? IIRC, Hornby had proposed a box that handled 4 sensors and then relayed back to the Elite. So were the sensors connected to that wirelessly or not?

[hosh]

Here's some other historical info I found in my travels -

 

Dec 2013 - Railmaster Loco Detection System 

R8306 Pack contains: LD Module, 1Pk LD Tag Strips, 4 x LD Track sensors. £79.99R8307 LD Module £69.99R8308 LD Track Sensor £ 7.50R8309 LD Tag Strip £ 9.99R**** LD Track Sensor Transformer £ 9.99

 

Hornby magazine May 2014DCC Handbook - page5Hornby loco detection system is made up of 3 components, a loco detection module, track sensors and locomotive detection tags.Each LDM is designed to plug into a USB port on a PC and can read up to 48 track sensors. Additional LDM's can be connected to read more sensors.The track sensors require a 1mm hole to be drilled through a sleeper for installation.The detector tags can be fitted to the underside of the locomotives, and the system will work with up to 106 encoded tags at any one time. As a tag passes a sensor it passes data to RM about which locomotive. If you have more than 106 locos you can duplicate the detection tags on other models not in use at that time. Loco detection is expected to be available later this year. Prices are yet too be confirmed, but it is anticipated

track sensors 10 GBP,

detection tags 30 GBP (for all 106),

loco detection module 80 GBPLoco detection will be able to switch signals as a train passes the sensor, stop or alter train speed according to signal state etc.

[hosh]

 

Btw, do we know whether the Hornby detectors will be wired or wireless? IIRC, Hornby had proposed a box that handled 4 sensors and then relayed back to the Elite. So were the sensors connected to that wirelessly or not?

 

So obviously I didn't remember correctly - each LDM can handle 48 detectors.

 

Looks way too pricey though!

[PJ_model_trains]

From what has been discussed and made known so far I expect LD will be as follows

 

Sensors will be installed in the positions we choose on our track. They will have two wires which will probably for easiness will be be wired to a LD Bus, the Bus wires go back to the LD controller which is connected by a USB cable to a computer.

 

When an item goes over the sensor the tag is read and two items of data are sent back to the LD controller, which in turn passes the data to RM to process and check if there are any pre-programmed instructions for the data transmitted.

 

A basic example would be... tag number (system knows what this number is allocated to) sensor number (system knows which sensor it is), therefore Loco with tag number ...... passed over sensor number ...... RM knows the tag number is for this train and instructions were pre-programmed to, change signal to red if this train passes over it (or if all trains pass over it), there may also be instructions pre-programmed to change a previous signal to Y, YY or G, an instruction may also be if train ...... sound horn, change speed, etc.

 

I personally, just my opinion, doubt if the sensors will be wireless, the fact that dirt and dust can affect sensors, wireless could just be another risk, wired in seems more logical to me, probably with its own LD Bus would be the simplest. As far as I am aware nothing has been stated regarding the possibility of the sensors being wireless.

 

[Howbi]

PJ..............this is the type of TX/RX sensor that Hornby illustated in their handbook............It has 4 wires to connect to the Module, 2 for the transmitter and 2 for the receiver......... http://www.littlebluepigs.com/electronics/sensors-modules/10-x-tcrt5000-reflective-photoelectric-infrared-optical-sensors-tx-rx.html     HB.

[Fishmanoz]

If each sensor is wired separately to the LDM, it could be very simple with all the digitisation done in the LDM.  I'm betting though that the sensors will be on a bus, an LCC bus, and therefore more complicated as they will have to digitise the data and modulate it onto the bus.

 

Hosh, that stuff you looked up was already in the forums twice in previous threads. It got a lot of coverage here in May 14 due to its being in the DCC Supplement in the Hornby Magazine. If you want to see the full instruction set available, it was last posted by PJ in a thread titled Loco Detection (note both the words are capitalised, unlike the recent thread of that name).  The instructions allow you to do things to one loco, a group of locos or all locos and, as well as setting points and signals, you can run a program. 

[hosh]

PJ..............this is the type of TX/RX sensor that Hornby illustated in their handbook............It has 4 wires to connect to the Module, 2 for the transmitter and 2 for the receiver......... http://www.littlebluepigs.com/electronics/sensors-modules/10-x-tcrt5000-reflective-photoelectric-infrared-optical-sensors-tx-rx.html     HB.

 

So this is like active sonar - i.e. the "transmitter" sends out a signal and the reciever sees what comes back?

 

So what I see so far is -

• Costly
• Maintenance
• Sounds like every sensor needs it's own wiring making it little easier than BD to install.

For comparison, a BD system needs you to use 1 wire to run from the detection module out to the blocks. Rail A remains wired from the power supply as normal from Output A and Output B runs to the module with individual wires running from there out to the blocks just for Rail B which is where you put your plastic joiners.

 

So the wiring might be actually easier for BD. And I don't really see pulling up a bit of track and installing a few plastic joiners for Rail B as all that much of a big drama even for existing layouts. Sounds like LD will require similar fiddling with the installation of the sensors. For my money, BD is a no brainer for someone doing a layout from scratch and maybe even for existing layouts!

[PJ_model_trains]

So it appears you have made your decision hosh

I haven't and will for the time being keep my options open, technology is moving on.

[hosh]

Just a note about the barcodes for LD - are they symmetrical? Reason I ask is I was wondering what happens when a train is moving backwards and so it's barcode would be read from the backside first.

 

Or maybe not. Maybe they can be read backwards and thus also then know the direction of the train's motion. If all the barcodes are the same length then speed is obtained by how long it takes for the barcode to be read I guess.

 

I guess I've just worked out for myself how LD will work. Now I just need to work out why I need any of this! LOL.

[PJ_model_trains]

I guess I've just worked out for myself how LD will work.

Now I just need to work out why I need any of this! LOL.

 

Gosh hosh, so you are not a 'total' BD  ;o)

 

[PJ_model_trains]

Just a note about the barcodes for LD - are they symmetrical? Reason I ask is I was wondering what happens when a train is moving backwards and so it's barcode would be read from the backside first.

 

Or maybe not. Maybe they can be read backwards and thus also then know the direction of the train's motion. If all the barcodes are the same length then speed is obtained by how long it takes for the barcode to be read I guess.

 

All these things have been discussed in great detail, [over and over again WTD will say]  ;-)

 

• Train speed - this is already known by RM
• Train direction - this is already known by RM (forward or reverse)
• Bar code - a series of bars thick and thin referring to numerical values.
• Loco/tender/last carriage/guards van passing over sensor is known by code we have already programmed
• Sensor - loco (or other part of train) is known by the item we programmed to the tag

 

A bar code (numerically may be for example) 02469318 so if read 81396420 direction of loco is also known by the direction barcode is read. Assuming bar codes are the method LD uses  ;o)

 

We know which loco has passed over which sensor because we designed our schemeatic plan and are sat in front of it.

 

We do not have LD yet... coming soon or 2017 still awaiting confirmation! But here is a thought for LD PRO (LOL)

 

A loco goes over a sensor, we pre-programmed it, the change signal it passed changed to Red/Stop. Data passed back from LD to RM could change the colour of our track icons. At some stage in the future it would be easy for HRMS to program and for us to group layout pieces so that a live Block could have different colour layout icons. e.g. leave track piece colours as they are for un-occupied blocks and change to say white centre with same colour border for occupied blocks. This is only a basic consideration at  this stage, it is to early to make suggestions to a scheme not yet launched. But once LD has been launched and run for a short period I am sure we will be looking at more ideas and a Pro version. I am sure Hornby will too.

 

[Howbi]

Hi PJ........further to your interesting summary re: LD...........Hornby's info was that the Tags would be numbered up to a max of 106 only............It was interesting to find Wand type Bar Code readers where the tips are very small and conceivebly could be manufactured in the size necessary to fit between sleepers as shown by Hornby as a light source and receiver paired together...........this statement is copied from WickiPedia........

Pen-type readers consist of a light source and photodiode that are placed next to each other in the tip of a pen or wand. To read a bar code, the person holding the pen must move the tip of it across the bars at a relatively uniform speed. The photodiode measures the intensity of the light reflected back from the light source as the tip crosses each bar and space in the printed code. The photodiode generates a waveform that is used to measure the widths of the bars and spaces in the bar code. Dark bars in the bar code absorb light and white spaces reflect light so that the voltage waveform generated by the photodiode is a representation of the bar and space pattern in the bar code. This waveform is decoded by the scanner in a manner similar to the way Morse code dots and dashes are decoded.

The output from the reader is then deciphered by the LD Module and resultant data sent to RM.....possibly, HB.

[Howbi]

Well, magfan.......you are obviously far cleverer than the electronic experts employed by Hornby so maybe you should email the MD and tell him where he's going wrong..........!  :o)     HB.

[PJ_model_trains]

Hi PJ........further to your interesting summary re: LD...........Hornby's info was that the Tags would be numbered up to a max of 106 only............

...in a manner similar to the way Morse code dots and dashes are decoded.

 

Hi howbiman

 

The barcode example was included as an example. if I had put 106 or 601 it may not look like a barcode so I included 8 digits as to me it seemed to make more sense. May be maybe not.

 

I also noted... assuming it is a barcode, at the present time we do not know.

 

Interesting comment you made regarding the use of morse code though... I am now wondering if they are using it!

 

Not for the LD system but maybe regarding the date it will be launched, coming soon or 2017.

 

Possibly they are using the following         . . .    - - -     . . .

 

[Howbi]

@magfan............sounds like you've got some pretty smart kit, perhaps you could post a photo one day.........Regarding Hornby LD, maybe the Bar Code reader circuitry is what is built into the LD module and converted into language that RM can understand.   HB.

[PJ_model_trains]

if railmaster already knows the speed and direction and which loco passed what other information is needed ,?

so if railmaster knows all this already all r.m needs is the loco is covering the sensor , so only needs a single bit of information,

hence photo reflective sensor 

one system or t'other ,why both ? 

 

 

LD will only pass back two items of data as a tag passes over it

 

• the sensor code
• the tag code

 

Tag code could be on loco, tender, last wagon, last carriage or guards van

 

RM processes the information sent back subject to pre-programmed instructions we have added.

 

If there is no pre-programmed instruction in RM the loco continues. The sensor code and tag code will always be sent to the LD controller and then to RM to see if there are any instructions to carry out.

 

[Fishmanoz]

While you are all thinking about how LD works, can I just reiterate some points from previous threads that may assist this thinking.

 

1.  Most important point - as it is currently implemented, RM has no idea where anything is, only you do.  If you were to remove all the straights  and curves from your RM schematic (not including the ones that contain LD sensors), it would not change by one wit what RM knows about your layout.  When LD is added, this remains true with an important unless ............ unless HRMS make a fundamental change to the way RM works, and I think this unlikely anytime soon.

 

2.  Given 1, RM cannot make any sense out of having read a loco tag forwards or backwards.  Knowing a direction would mean it knows where things are and what sequence they occur in along a track.  And it doesn't know either.  The only direction it can know when a detection is made is whether the throttle for that loco is set to Forward or Reverse.  And that tells you nothing about where the loco has come from or is going to.

 

3.  Knowing speed on detection.  Hosh, you mentioned determining speed by reading how long it takes for a loco tag to pass over a sensor.  I wondered whether the accuracy you can achieve doing this would be sufficient to give a good speed reading, and I think maybe it can.  The other way to try to do it would be from the speed step the throttle is set to when the detection occurs.  But it may not be travelling at the nominal speed for this speed step as it may be accelerating or decelerating at the time.  So I think that leaves tag passage time as the only feasible way to do it.

 

4.  PJ has talked about having tags not just on locos but also on tenders and last carriages/wagons in a train.  The importance of these is knowing when the entire train has passed a sensor so he can use that information for his signal operation, and others will want to know this too.  If you look in RM loco setup, you will see where you can enter the tag number for the loco, which is how RM can know which loco has been detected.  But there is nowhere you can set up a tender or wagon this way.  To achieve PJ's desired result at present, you would have to set up tenders and wagons etc as dummy locos and then include the tag ID in that setup.  And that really puts the kybosh on throttle setting for determining speed as you won't be using throttles on dummies.

 

Thats all I have for now, I hope this helps your LD understanding. 

[MetmanUK]

@Fishy, 

Your 2 above is correct but don't forget the same is true about point settings.  All you need is a 'reverse' checkbox for that LD decoder and it will know the direction.

[Fishmanoz]

My point Metman is that direction is meaningless given you don't know where anything is, even if you know it's set forward or reverse.  It only becomes meaningful to you as you can see where everything is on the schematic and the layout, but RM can't. 

[hosh]

My point Metman is that direction is meaningless given you don't know where anything is, even if you know it's set forward or reverse.  It only becomes meaningful to you as you can see where everything is on the schematic and the layout, but RM can't. 

 

So this means that RM will not be able to fully automate a layout as it stands?

 

Are there any "IF THENS"? For example, can RM know that Train A is in block A and tell train B, in block B that's headed toward block A, to stop?

 

If not, then this is not an automation system of any worth at all!

[Fishmanoz]

Hosh, yes LD will allow full automation as there are If Thens.

 

In fact, the full instruction set as posted by PJ 4 months ago on page 3 of the Is This How LD Work? thread is:

 

Loco Detection:

On signal green

On signal red

For Locos;

For train type(s)

For forward direction

For reverse direction

For any direction

Stop loco

Stop loco on signal

Resume loco on signal

Reduce loco speed to

Increase loco speed to

Set to cruise speed

Switch right point

Switch left point

Set clear signal

Set danger signal

Activate loco function

Play sound file

Run program file

 

[RDS]

... yes LD will allow full automation as there are If Thens ...

 

 

 

Now that is powerful, I did not realise IF / THEN was included.