Gordon H

3 hours ago, Pete the Elaner said:

Hurst models made a brass one, cast using a lost was technique. I have several unbuilt ones & won't be letting them go. They are a bit rough & need work before assembly, which I want to try one day.

I have heard these were used on an exhibition layout (High Gill for those who remember it), but it was fragile & they suffered a few breakages.

You must have misheard slightly.

The working Brecknell-Willis pans used on High Gill were scratchbuilt in brass (mostly by me).

I demonstrated their construction at the first ModelRail exhibition in the early 90's at St Alban's (still got the sweatshirt!), and during the show I lent one to Hurst who were at that time considering the production of a kit.

Some time later their kit appeared using brass castings.

I did buy one to try out, but found it far easier to continue scratchbuilding instead.

20 hours ago, melmerby said:

OP states non-DCCsystem

So what?

I didn't claim my demo implementation would be directly suitable for the OP - just that you can see something akin to it at the AP show.

Nothing to stop the same principle being used with a DC system.

Indeed, the same hardware could be adapted to generate a PWM track signal instead of DCC, just needs different code.

Gentle slow down, speed determined by the 'inverse' of the distance measured when within a specified range.

The track control is implemented using a second Arduino acting as a DCC command station running 'DCC++'.

16 hours ago, Nigelcliffe said:

Also, in the Arduino theme, the acoustic range sensors in a typical Arduino starter kits are accurate enough for buffer stopping duties.  

 

If you would like to see an acoustic sensor Arduino shuttle in operation, I should have a demo on the MERG stand at Ally Pally.

It uses two HC-SRO4 ultrasonic sensors with an Arduino Uno.

Out of interest, I just checked on the BBC Genome site, where Radio Times listings can be found.

Seems the first Saturday afternoon Alan Freeman show was on 30th June 1973.

https://genome.ch.bbc.co.uk/schedules/radio1/england/1973-06-30

He took over the spot from Johnny Moran - not a name that I remember.

14 hours ago, tomparryharry said:

Alan Freeman was about 77-79, and Vance was on after Freeman retired.

Alan Freeman started his show a lot sooner than that, 73 to my certain knowledge, possibly earlier.

It was particularly notable because it was available in FM Stereo using the Radio 2 channel, long before Radio 1 had its own FM channel.

In those days, Radio 2 provided sports coverage on Saturday afternoons on its AM frequencies (the radio equivalent of 'Grandstand' on TV), allowing the higher quality FM channels to be used more effectively for music. They did a similar thing during the week after 10pm for 'Sounds of the Seventies' - and of course on Sunday at 6pm for the Top 20 as it then was, with Tom Browne.

When I first heard it, the Alan Freeman show included a game segment, called 'The Name Game', where he gave the initials of song titles and you had to work out what the songs were. Can't recall if there were any prizes though. Two example questions I can remember - 'P O M M' and 'S I T S O L'.

Later on the game format changed to something else, which again I can't recall off hand.

LSC = Linked Section Control

RLSC = Reverse Linked Section Control

They are both a means of setting up a route, usually without using section switches just the point and signal controls.

With LSC the train is driven from the sending end, and with RLSC the train is driven from the receiving end.

13 hours ago, Pete the Elaner said:

 

I agree with your calculations but where would you find a 22.5W resistor? These are not normal electronics products. Rapid don't seem to have one on their website.

 

Really? How about this whole section of their website: https://www.rapidonline.com/power-resistors

4 hours ago, Pete the Elaner said:

Never seen them on sale before, but at over £2 each, they are not something many would have lying around in a components box.

& you couldn't plonk it across the rails them move it around...not without a pair of oven gloves anyway.

 

Dare I ask...have you got one or is this just theory? ...bearing in mind you suggested 10ohms & they don't seem to have one available this size.

How about Rapid 62-8112 or RS 157-550?

Suggest you check the facts before making such sweeping statements.

I suspect what you are dealing with here a 5V logic level output from the decoder processor, followed by a diode (and probably a resistor) in series with the output  to prevent people accidentally connecting an external power source to it and causing damage. That would explain the off-load voltage that is being measured.

I would suggest you ignore the posting immediately above, and try it with a conventional LED and resistor first.

If you can, put a DMM in series with it, set to measure milliamps,  and see what comes out.

Anything in the 2 to 20mA range should be OK, then adjust the resistor value to suit the brightness you need.

It will also be at Manchester in December.

See picture here:

https://www.eventbrite.co.uk/e/the-christmas-model-railway-show-manchester-2019-tickets-71273285315

In similar vein, I think the pantograph base is on backwards. The longer legs should be towards the cab front.

22 hours ago, kevinlms said:

Making the contact isn't normally a problem,  it's whenever you attempt to break it causes contact welding. Holding the button down long enough to discharge the CDU, should prevent that.

Two potential situations arise from this which would still cause the problem I was alluding to - switch bounce and too brief a pressing. There is no way to guarantee either of these won't occur, and with the level of current involved it only has to happen once or twice to ruin the switch. Far better to use a solid state solution rated for the job.

15 hours ago, Tony Teague said:

ELEVEN points simultaneously on a single CDU does sound like a difficult ask!

Is there no way of dividing this circuit in two - otherwise I'd persoanlly doubt that there is an off the shelf CDU available with sufficient power.

 

More to the point, will your push button switches be able to cope with such a large instantaneous current of probably 15A or more?

Can you confirm whether the new signals will work using a on/off switch rather than relying on a momentary switch action like the old ones did?

On ‎19‎/‎06‎/‎2019 at 09:10, Free At Last said:

I enquired as to the purpose of the 'control unit' and whether the present range will come with one...

 

Did they say whether the switch they now include with it will be an on/off type or a momentary type?

Hopefully they have seen the error of their ways and gone for on/off this time round.

22 hours ago, RFS said:

 It's a square wave operating at approximately 7000 cycles which results on a DCC bit-stream of around 7k and this does not have any parity checking.

It most certainly does have parity checking. The final byte in every packet is an XOR checksum of the preceding Address and Data Bytes - refer to NMRA S9.2.

On ‎26‎/‎07‎/‎2019 at 22:48, Pacific231G said:

In its original form the railway pantograph does sort of vaguely resembles the drawing device (if you don't  look too closely) in that it is a parallelogram but you need the externally extended arm that railway pans. dont have to actually reproduce a shape. However, the word's been used  well beyond its original meaning. Such is the English language.

 

Surely the drawing board pantograph comparison refers to the fact that on a drawing board it keeps the ruler at the end of the moving arm parallel to the board edge at all times. The railway pantograph does a similar job by keeping its head parallel to its base throughout the allowable range of movement - hence the linkages employed.

To emphasise the point made above, here is another chart which actually uses the term 'Hook-up Wire' for sizes up to 1 AWG.

A second chart would be referred to for conversion between AWG and stranded wire nomenclature (e.g. 24AWG is nearly equivalent to 7/0.2)

On ‎13‎/‎07‎/‎2019 at 17:17, melmerby said:

I was going to say rubbish to that as I have used panel mounted solder terminal scarts*, but when I just tried to find one online I couldn't!

 

I did the same before posting my comment, then covered myself by including the word 'usually' on the basis that someone else might come up with an on-going source.

1 hour ago, john new said:

Thanks for that. Had a feeling the wires would be too thin as the flat version cables didn't look very sturdy.

 

I have some D connector pairs in hand recycled from earlier layouts, but if I use them they will need de-soldering/rewiring - the advantage of switching to SCARTS looked like the ability to buy off-the shelf, ready made, sealed, leads.

The only advantage of SCART leads is that they are available off the shelf.

Otherwise they are pretty hopeless for our use.

As has been pointed out their wire cores are typically only suitable for low current audio/video signals (not unreasonable as that is what they are intended for).

They have no latching mechanism, so are quite easily dislodged.

The panel sockets for them are usually intended for PCB use only, which makes them awkward to terminate with actual wires.

I certainly wouldn't use them on a layout.

No, this would not work as suggested. You would need to 'uncommon' one of the signals to allow its individual LEDs to be connected in series with the equivalent second signal LEDs.

Easier to wire the two signals in parallel to the single switch and add extra resistors if excessive brightness is an issue. Longevity is not a problem with LEDs if they are treated properly. They are not like filament bulbs in this and several other respects.

Should have said nothing at all.

6 hours ago, Pete the Elaner said:

Remember that the real version is operated by a chain inside the arms. Even if this could be replicated in 1/76, it would not last long.

It can be, and it does last. 

See this thread from some years ago:

Brecknell Willis Pantographs

The inclusion of connectors will allow far easier fault finding by enabling the isolation of individual baseboards.

56 minutes ago, Tony Teague said:

I have used Heathcote IRDOTs extensively (more than 100 installed and operational), and although I don't have a completely automated loop, this would be easy to deliver.

 

Is that indoors or outdoors?

Outdoor use of opto detection can be problematic given the wide range of ambient light conditions, and variable direction of sunlight that occurs throughout the day. A self modulated detector with automatic gain control would be needed if a reflective solution is used.

This is without considering the potential difficulties of installing equipment under the track in the garden - which of course largely depends on the method of construction.

This is why current detection is usually considered a better option in such circumstances.