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Mynis Cule Magna - a BPRC adventure
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 Posted: Sat Feb 14th, 2015 05:15 pm
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Geoff L
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Apologies for the long initial posting to set the scene for an excursion into the construction of a battery powered radio controlled model railway layout. The post has been opened in this section because, whilst embracing many topics, the main purpose of the layout is to test bprc..


In July 2014 the EM (eighteen millimetres) Gauge Society announced a challenge to members to build a new layout within 12 months restricted to an area of 60 inches by 18.2 inches, these representing the 60th anniversary of the Society and the established EM track gauge (in mm). Layouts were to be to EM or P4 (finescale) track standards and the idea, apart from creating new exhibition layouts, was to stimulate innovation and (as a later aside) discourage the usual branch terminus. So that settled it!


There may be some ingenious ideas amongst the reported 27 entries but there isn’t much new in railway modelling track plans, particularly given the exposure of micro layouts on Carl Arendt’s web site, coverage in Model Trains International, topics on Freerails and a number of recent books. So the emphasis may be on the setting and materials used rather than on the track plan. A branch line terminus therefore may not cut it.


However, the challenge has been seen as an opportunity to replace an aging boxed 00 diorama 48 inches by 16 inches or to condense an ongoing 19 feet long GWR EM gauge branch line on which progress has stalled. Considerable effort would be put into trying new techniques: DCC, computer control, electronic communication systems, radio control…….Battery powered radio control (as the future) was chosen, not only for the motive power but also for controlling the layout, and my initial thoughts and request for assistance appeared in the DelTang thread. 


So six months in, how far has been travelled? The attached plan is a general arrangement of the proposal which depends on the fiddle (staging) yard being on view at the front, which is convenient for home use, and the use of a sector plate substituting for half of the loop. Conventional operation from the front, however, would impede the view of spectators at exhibitions and impact on the area of the layout, making remote control desirable.




A two section laser cut baseboard kit has been purchased, assembled and painted, some radio control modules sourced from DelTang, membership of the Model Electronic Railway Group (MERG) taken out giving access to a printed circuit board with construction details for a stepper motor operated turntable controller and track, signal and coupler kits stockpiled.


Concentration has been on the ‘new’ technologies of radio and electronic control as lack of success in these areas would mean a re-appraisal of the proposal.

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 Posted: Sat Feb 14th, 2015 05:39 pm
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mwiz64
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This looks like a good one to watch. That's about all the more space I have these days.



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 Posted: Sat Feb 14th, 2015 08:07 pm
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Geoff L
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Radio control

David Theunissen (DelTang) has supplied a Tx24 kit, Tx3, 2 x Rx62-22 and 6 x Rx105. The two transmitters have been installed in a redundant multi-tester case along with two rotary switches, 3 potentiometers, 2 on/off switches, 2 bind buttons and 20 assorted on-on / (on)-(on) switches and 2 multiplexing boards! In theory 30 accessory channels are available but this is reduced to 24 functions because some are duplicated to operate items on each board, e.g. crossovers and signals, and up to 12 locomotives can be selected.

Two locomotives have been successfully run but the available power for the line is a diesel railcar as that has a body large enough to take a reasonable battery (PP3 size); tank locos are a problem as I have not yet located small enough, powerful enough batteries.

The controller is capable of being used with more than one layout subject to the maximum 12 locomotives and there should be sufficient channels for most small and medium sized layouts. The photographs,when I can upload them, should show the rather cramped contents of the layout controller which came out a little larger and heavier than originally envisaged.

I suspect that it might be possible to have a much simplified controller if a Selecta type feature could be used selecting between functions with a limited number of switches but I do not have the experience or time to experiment with this.

Geoff L



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 Posted: Sat Feb 14th, 2015 09:09 pm
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NevadaBlue
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Sounds like fun, I'll be watching from here. I have never heard of "18.2" gauge. Do you have to make your own track or... ?

hmmm... I looked it up. Now I know, learning all the time...

watching. :)

Last edited on Sat Feb 14th, 2015 09:10 pm by NevadaBlue



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 Posted: Sun Feb 15th, 2015 06:45 am
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Helmut
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Well, the true gauge for Brititsh 4mm scale would be 18.8mm, heaven forbid 3/4in! That's only what  the Americans had done in the 50's when there was still US 00 gauge around.
The Brits invented EM gauge as an in-between.



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 Posted: Sun Feb 15th, 2015 08:15 am
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Geoff L
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Yes, Helmut. The P4 standards have a track gauge of 18.83mm and I would have liked to have adopted that but already had a quantity of EM wheelsets and gauges, otherwise everything else is scaled at 4mm to 1ft (are we a bridge between Europe and USA?) An extra 1mm between the frames would have been more than handy for installing batteries!

Geoff

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 Posted: Sun Feb 15th, 2015 04:39 pm
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Geoff L
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Sector plate driver
With some setbacks the turntable driver board has been altered to suit its simplified role and the inputs arranged to take the signals from the Rx105. The operation has been successfully bench tested and the sector plate works with a simulated load merely cantilevered out from the motor housing, which looks promising. The disappointment is that there is a slow response in picking up the signals which means that the LED might need to be visible to prompt use of the momentary run switch.

Again, the photographs show the test rig. These have proved too large to upload so hopefully can be seen at

https://plus.google.com/photos/110290454705104886186/albums/6116179726810916369?authkey=CPPeterIyKSm_wE

The turntable driver unit produces both12v and 5v outputs, the latter being used for the Rx and hopefully the former for the electro-magnetic uncouplers.
Whilst the whole could have been run from 12v batteries, a mains fed 16v ac input will be used which will mean two wires to link the boards (hopefully via the two securing bolts!)

Geoff

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 Posted: Mon Feb 16th, 2015 02:33 pm
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DavidT
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Geoff, Neat installation but makes my head hurt trying to absorb everything! You may need to try to optimise aerial placement to improve radio reception. A receiver aerial that is flat on a dense board and surrounded by metal objects may benefit from being more in clear air. TX aerials also need minimum obstruction. Signal strength is best when aerials are parallel and overlapping (like fingers).

You asked in the other thread: "Would your revised arrangement help with the speed of execution and cope with the requirements of the turntable driver? The present arrangement is presumably to cater for the stepper motor drive and control from a distance; a different arrangement could make use of the Selecta for a direct drive but would need some form of indexing unless it was being eyeballed."

I think you are referring to my 'Menu' feature which can control up 12/24/36 options with one channel depending on how used. That feature probably would be another option for you. At this time my Rx65 has 15 on/off outputs (P+F). I expect to make an 'Rx105' type receiver that can use the 12-position channel but I don't expect to do this soon.

You mentioned turntable and steppers. I did not have any deliberate intent for them. I'm not familiar with how they are controlled now to have a sensible view.

Control of layouts is at a very early stage for me so I will be pleased to hear more observations and views to move it forward. I think we will have to stick with 7 channels max per transmitter. Dividing each channel into 14 segments is convenient due to the availability and compactness of 12-position rotary switches, and the 13th and 14th positions can be convient to use as triggers. But used in this way the channel can only be in one position at any time and the receiver has to have the right cleverness to convert that into up to 36 actions per channel. Typically they probably need to be 'latching' in nature.

The position of each channel is just a numeric value between 0-1023. In binary terms it is 10bit which means each bit could represent an independant on/off 'channel' on it's own. Used in this way one channel could control 10 two-position actions. This might be an option for future evolution. This level of detail is available now in various products but requires 'arduino' type controllers or new products from me/others to convert it into useful actions.

I may have missed questions in your text so let me know please if you want better answers/more detail on anything.
Regards, David.

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 Posted: Mon Feb 16th, 2015 06:07 pm
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Geoff L
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Thanks for your advice, David. At this stage it is far too technical for me! Whilst each channel can be used for a number of actions there must presumably be some form of trigger for each? For a conventional control panel on a model railway this would not be a problem as there would be similar hardware but it would communicate by radio rather than wire, although there might not be any advantage in doing so on a small layout ; connections would still have to be made to the Tx and from the Rx to the servo, for example. On a large layout there would be savings on wire and the absence of problematical plug connections between boards.

I am assuming that your proposed controller would be used by selecting say one turnout position on the rotary switch and then using one of the switches as appropriate or would you see another way? This would certainly save on switches but could mean memorising a lot of positions. The advantage might be a saving in the number of Tx required.

I probably rambled on a bit, but my comment on the turntable driver control was for information as the operation was slightly different to other uses. My main question was whether your new controller would operate the switching more quickly than the Tx3 with MUX boards? I do not know much about stepper motors either but they seem to operate in a similar way to servos in having a power supply and pulsed instructions. The controller is a PIC that can be programmed to memorise the various track positions and conventional operation is by setting a HEX switch and pushing the run button. The way I am using it requires only four ordinary switched inputs and a run button. Luckily the driver operates on the inputs changing high in the same way as the Rx105 whereas most of the MERG products rely on changing low. On operating the position switch there seems to be a lag until the changed position is recognised before the run switch can be pressed and released. However, this might improve when properly installed and further experimenting can take place.

What I am looking for in control is simplicity in the amount of hardware and intuitive use for rookie operators, but having said that, it is probably no worse than DCC where one needs to remember (or have access to, with a delay,) an individual 2/4 digit code for each item and then input it without error.

Keep up the good work.

Regards

Geoff

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 Posted: Tue Feb 17th, 2015 01:56 pm
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Herb Kephart
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David

YOUR head hurts?

What about us mortals???

Herb



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