Dock Green

[chaz]

I know I ought to kick off a topic of my own at some stage, but if it's okay with you I'll post them here. They'll most likely be links to where they get hosted. I hope they come out - having bright backlighting against a window wasn't very helpful at times!

 

Agreed. I did hope to get a spot with a wall behind us, rather than windows but it didn't happen......

[chaz]

I was thinking of an auttostop on a wander lead so it could cope with different length cassettes, fitting into a slot each side of the cassettes where poswer would be applied. A hinged piece of ply as a stop which could activate a microswitch with a stop to prevent the nicroswitch being mangled when a heavy flywheel fitted loco enter the cassette at top speed!  You would also need a back stop as the cassette with loco could be driven back. It may have its own problems which I did not spot. This is an area where DC can be advantageous set up so the trains are driven to an operator who can see what is happening. Presumably your led will show that the DCC signal is being received. I take your point about cutting the power on a DCC loco. Good practice suggests stopping a loco otherwise you may gets a surprise later on. My test with my inital DCC set up showed a loco could remember it last speed and direction for a couple of months at least.

Don

 

 

Yes. Most of the time I rely on the operator to stop in the right place and this generally works fine. If anything trains tend to be stopped too soon rather than too late. The point of the LED indicator is that at the moment an operator has no way of knowing whether the cassettes have power or not - only an unwanted sudden stop reveals that one or more of the bulldog clips is failing in its duty.

 

"heavy flywheel fitted loco enter the cassette at top speed!"   My DJH V2, which is a very heavy model once ran at a fairly brisk pace into a Peco stop block. The loco was undamaged but the Peco item was pretty much destroyed. However if you have seen Dock Green in action you will know that top speed is a foreign concept.

 

The workings of Dock Green have been refined with small changes made from time to time in the light of experience gained at shows - Dock Green only gets operated at shows and each one seems to suggest some change or other.

 

Chaz

[HeatherKay]

Well, here are the dodgy photos...

 

 

 

 

 

 

 

 

 

 

 

Did that even work? If not, expect a swift edit! They don't make it easy to share stuff here, do they!

 

I had a link to a video, but that didn't work very well. I'm afraid you'll have to follow the URL to my YouTube channel.

 

  Edited October 20, 2014 by HeatherKay

[chaz]

Chaz

 

any reason the leds could not be mounted between the rails?  Don't need to see them when the track is occupied, only when empty.  Robust and hopefully visible.

 

S

 

Not an option I don't think Simon. The bases of the cassettes are MDF which are slotted for flangeways with brass strips as conducting "rails". Also the depth of the sides would make sighting very difficult.

 

 

 

I will probably mount each one on a strip-board plate fixed to a top strap and arranged so that it doesn't project above the top edge.

[chaz]

Well, here are the dodgy photos...

 

 

Did that even work? If not, expect a swift edit! They don't make it easy to share stuff here, do they!

 

 

 

Some interesting close-ups Heather. The shot of PC Dixon might need the services of PhotoShop to eliminate the husband and wife team doing King Kong impressions in the background!

 

I note that your nice little video, which incidentally records an instance of coupling failure, also has my fatuous comment about an appearance fee on the soundtrack.

 

On the subject of ease of posting of photos - I upload mine to Photobucket. Once on there I copy the URL using nothing more sophisticated than CTRL-C and then plonk it into my posting on RMweb with CTRL-V. Works best if both RMweb and Photobucket are running together (in different tabs). I should say that before I upload to Photobucket I compress with a little program called PIXresizer which is a freebie download. May seem a bit of a rigmarole but works well enough.

 

Hope that's some help.

 

Chaz

Edited October 20, 2014 by chaz

[HeatherKay]

Hope that's some help.

 

 

As you say, something of a rigmarole. I guess I get spoiled by other forums which let you embed images in posts on the fly. At least the video link worked properly! I seem to have missed a simple method of previewing a post before submitting it.

 

You're right about the Big Giant Heads - they weren't there as I framed up, but sneaked in as the shutter button was pressed!

 

Whatever, let's not dwell on my problems. I'm dragging things off the rails as it is!

[Donw]

Yes. Most of the time I rely on the operator to stop in the right place and this generally works fine. If anything trains tend to be stopped too soon rather than too late. The point of the LED indicator is that at the moment an operator has no way of knowing whether the cassettes have power or not - only an unwanted sudden stop reveals that one or more of the bulldog clips is failing in its duty.

 

"heavy flywheel fitted loco enter the cassette at top speed!"   My DJH V2, which is a very heavy model once ran at a fairly brisk pace into a Peco stop block. The loco was undamaged but the Peco item was pretty much destroyed. However if you have seen Dock Green in action you will know that top speed is a foreign concept.

 

The workings of Dock Green have been refined with small changes made from time to time in the light of experience gained at shows - Dock Green only gets operated at shows and each one seems to suggest some change or other.

 

Chaz

 

You mean neither you or your operators ever turn the control knob the wrong way and instead of stopping the loco speeds up at the wrong moment! I seem to have a problem with this I think it is liked to my lefthandedness. I tend to turn the opposite way if I do it with the other hand. i.e a clockwise movement in the right hand  would naturaly be done anticlockwise in the left. (When I first learned to write it was mirror image.)

I did see Dock Green at the NEC and the running was sedate.

Don

[chaz]

You mean neither you or your operators ever turn the control knob the wrong way and instead of stopping the loco speeds up at the wrong moment! I seem to have a problem with this I think it is liked to my lefthandedness. I tend to turn the opposite way if I do it with the other hand. i.e a clockwise movement in the right hand  would naturaly be done anticlockwise in the left. (When I first learned to write it was mirror image.)

I did see Dock Green at the NEC and the running was sedate.

Don

 

No control knobs, Don. I use Lenz LH100 handsets which have only buttons.

 

 

Sedate is good in a yard.

[Simond]

Chaz

 

Looking at your cassettes, perhaps surface-mount LEDs could go on a gapped bit of sleeper strip adjacent to the wooden "bridges", or the more traditional shaped ones could be poked up through a hole in the "bridge" itself. Sticky-backed copper tape could provide a simple means of connection to the rails, without reducing the structure gauge very much.

 

Best

Simon

[chaz]

Chaz

 

Looking at your cassettes, perhaps surface-mount LEDs could go on a gapped bit of sleeper strip adjacent to the wooden "bridges", or the more traditional shaped ones could be poked up through a hole in the "bridge" itself. Sticky-backed copper tape could provide a simple means of connection to the rails, without reducing the structure gauge very much.

 

Best

Simon

 

I will use matrix-board to mount the components.rather than sleeper strip as it already has conducting copper strips and holes. I don't like working with SM components and avoid these whenever possible. One of the reasons I dropped out of MERG was because of its move to SM technology.

 

Space is not that tight in the cassettes that a pair of wires along the top edge to the nearest corner where the brass contact pads are will cause problems.

Edited October 21, 2014 by chaz

[Donw]

 

No control knobs, Don. I use Lenz LH100 handsets which have only buttons.

 

 

Sedate is good in a yard.

 

Ah! I am much more at home with the LH90

Don

[chaz]

Ah! I am much more at home with the LH90

Don

 

I used to use LH90s myself. They are nice to drive with but are not too good with sound - you only have four function buttons and access to higher numbers is awkward enough to dissuade one from trying. I do have a couple in reserve but they haven't been used on Dock Green. It's a pity that Lenz haven't upgraded the LH90 with a full set of buttons.

 

Chaz

Edited October 21, 2014 by chaz

[chaz]

A little maths relating to the indicator LEDs here......

 

http://www.rmweb.co.uk/community/index.php?/topic/91670-what-equivalent-dc-voltage-should-i-use-in-calculations/

[Donw]

A quick  test seems to be the answer. Have you a breadboard? That would make it easy try a 1k resistor if a bit bright disconnect pronto if a bit dim try lowering the resistance using w.h.y till you get to a sensible result bright enough to see but not overly so. 

Don

[chaz]

A quick  test seems to be the answer. Have you a breadboard? That would make it easy try a 1k resistor if a bit bright disconnect pronto if a bit dim try lowering the resistance using w.h.y till you get to a sensible result bright enough to see but not overly so. 

Don

 

Well actually Don I have several breadboards. As an ex-CDT teacher I used to teach electronics to 11 - 16 year olds so I often modelled circuits. As far as the LED is concerned I have a bag of a couple of hundred green LEDs which are ex-equipment (and came to me from I know not where) - so if I fry one experimenting it will be of no consequence.

[Donw]

Well actually Don I have several breadboards. As an ex-CDT teacher I used to teach electronics to 11 - 16 year olds so I often modelled circuits. As far as the LED is concerned I have a bag of a couple of hundred green LEDs which are ex-equipment (and came to me from I know not where) - so if I fry one experimenting it will be of no consequence.

Apologies the words Grannies and eggs come to mind. I do rather believe in trying things out.

 

Don

[chaz]

Apologies the words Grannies and eggs come to mind. I do rather believe in trying things out.

 

Don

 

No need to apologise Don. This is an open forum and I welcome suggestions. Hope you didn't think I was point scoring?

[chaz]

Don suggested using a breadboard, I must admit it hadn't ocurred to me (!), but it was a quick way of trying out the LED indicator idea.

 

 

A green LED, a 1N4001 diode and a 1K0 resistor in series. Baseboard is up on end and the circuit model is connected to the DCC bus. The LED is bright enough but not obviously overbright! A quick check confirms that the circuit works the same which ever way it's connected to the bus. It's probably the simplest circuit I have ever modelled on a breadboard.

 

I will try some higher value resistors to see how much the brightness is affected with the current further reduced.

 

Chaz

Edited October 22, 2014 by chaz

[Simond]

Chaz

 

What do you need the diode for?

 

The led is a diode already, and the resistor will limit the current

 

My bufferstop lamps are just a led & resistor, seem to work fine, and have been since about 2005

 

Best

Simon

[Donw]

To increase the reverse voltage capability?

Don

[chaz]

Chaz

 

What do you need the diode for?

 

The led is a diode already, and the resistor will limit the current

 

My bufferstop lamps are just a led & resistor, seem to work fine, and have been since about 2005

 

Best

Simon

 

Technically the LED should be protected against the reversed polarity. In practice you can indeed omit it. However it costs very little to include it. Certainly for a test where current levels might be higher I included it.

[Simond]

Thanks guys.

 

Apparently the reverse voltage limit is of the order of 4 or 5 V but irrelevant if the current is sufficiently limited, presumably how I get away with it.

 

Options are a ) as you have, a diode in series, or b ) a diode in reverse parallel, c ) more complicated and unnecessary solutions

 

Option b would offer the potential to use two LEDs, thus more light, presumably, but I guess this is unnecessary - on the other hand, as you have an enormous bag of LEDs...

 

Best

Simon

[chaz]

 

Option b would offer the potential to use two LEDs, thus more light, presumably, but I guess this is unnecessary - on the other hand, as you have an enormous bag of LEDs...

 

 

 

Hmm, that's a thought. However I have decided to buy some new superbright fluorescent green LEDs for the job so the "enormous bag of LEDs" is no longer relevant.

[chaz]

I have been unhappy for a while with the way the signal couples up to its drive. It has been necessary to climb underneath the layout, guide a thin bit of wire into the connector while someone else gently lowers the signal into the socket from above and then tighten a couple of screws. At Wimborne this was a real pain, taking several goes to get the wire into the connector. I decided to have a go at redesigning the coupling. First thoughts were to use a pair of wire-ended magnets. These coupled themselves very neatly but separating them again was difficult and damage to the drive too likely - so that solution was abandoned.  

Here's the arrangement I have come up with. First the signal base....



I replaced the 0.6mm operating wire with 0.8mm - heavier and stiffer - and fitted it with a brass ferule.

And the change to the drive?

 

A short length of tube of a large enough diameter to receive the ferrule and with a bell-end  formed in the top to help guide it in. I retained the screw connector as it is a neat way to allow adjustment of the drive.

And here's the signal in place with the connection made.



The signal is "on" (stop position) in this photo - to put the signal "off" (clear) the drive pushes the operating wire up. When it is put back the weight of the wire and the ferrule is enough to move the arm to "on", keeping the two halves of the connector in contact.

The wire is normally more central in the square tube - this photo was taken with the baseboard on end so the weight has pulled it to one side. I rotated the photo to show the baseboard in its normal position. I deliberately left the wire that supports the tube long as it makes adjusting very much easier.

Although I haven't eliminated the need to get underneath the baseboard it should be much easier and quicker to fit and there are no screws to tighten. Of course this small improvement is invisible to any show visitor but it will make building and taking down the layout a bit more efficient.

 

Chaz

Edited October 23, 2014 by chaz

[flexible_coupling]

I'm interested to try and prototype a signal drive that has a "scaled-up" counterweight to give an authentic bounce. I know it's possible electronically with servos, but a mechanical solution might be fun to fiddle with..... of course for me it's 'horse before the cart' well and truly as my layout plans are still well and truly in the planning stage!