☰

West Exchange Sidings

Problems

This layout was designed with 4 NX panels, one in each corner. This makes operating the layout hard work, either a lot of walking or a lot of shouting. So it has been decided to go to a single panel operated by JMRI, with and optional front panel to operate the yard for shunting. This will involve replacing all the point controls so that they can be operated by DCC using a separate DCC power district.

The documentation for the current wiring is patchy, out of date, and wrong. Even the tag numbering cannot be relied upon. Also some of the D connector to tag strip wiring is different and needs correcting.

Lastly the operation of some of the points using Seep point motors is at best patchy, those near the power supply working better than those at the other end of the layout. This clearly needs to be fixed.

Finally, there has been an issue with bending of D connector pins. This could be due to trying to force 2 male D connectors together, in this case eliminating one set of connectors would help.

Solutions

The 2 short 3ft straight boards at the end of the layout are used for the test track, so need local control as well as remote DCC control. The plan is to use the current control switches on the top of the layout, the single capacitor point CDU's will be replaced by the MERG design dual capacitor design and a MERG DCC steady state decoder module. The MERG CDU's need 24 Volt dc, so need a convertion of ac to dc.
MERG DCC steady state decoder.
Kit 53 firmware in C.

The fiddle yard points, 12 at each end, can be controlled by 6 MERG pulse decoder modules, controlling 4 points each.
MERG DCC pulsed decoder.

The scenic front of the layout, has 7 points and one end and 8 at the other.

1. One possiblity is to use the Cobalt IP point motors. This would make the point movement quieter, but they are fairly expensive at £25 each, 18 for £450.
   There is an issue with the address being forgotten. DCC Concepts reported "We did have a part batch of Cobalt Digital IP point motors that could suffer an address memory loss when a high voltage spike occured on the DCC bus. Most commonly as a result of a short, but in the case of some systems - when they are turned on/off.
   A separate clean DCC power district may help with this.
2. /initially we will use the same MERG pulse decoder modules as the fiddle yard, with the current Seep point motors, Some points are on the next baseboard, so using the steady state board and CDU's will be necessary.

Track circuits

For the fiddle yard and front yard its helpful to know which track are occupied. To do this four MERG 2ch DCC only Current Transformer Block Detector DTC2 and one 8ch DCC only Current Transformer Block Detector DTC8 will be used. These operate from 5 volts, and need some way to feed the states back to JMRI. The CBUS CANVINP 16 input module look good, it provides 5 volts out as well. To get the information to a PC we will also need a MERG CBUS USB Interface CANUSB4, probably fitted near to the Lenz command station or fitted in a box and plugged into the CBUS connection.

For the main lines, the signal modules can provide a block occupied signal. This probably means having 3 or 4 CBUS CANVINP modules around the layout.

Power supply

The power supply is used by several layouts, so cannot be changed.

Inside the box are 2 x 160VA torroidal transformers, giving 4 outputs of 18 Volts at 4.44A. Each of these are connected to multiple pins on a 36 way D connector. Transformer 1, output 1 is connected to pins 1/2 and 20/21, and connected to 5/6 and 13/14 on the next D connector. Output 2 is connected to 6/7 and 25/26, and then to 23/24 and 31/32 on the next. Transformer 2, output 1 is connected to pins 13/14 and 31/32, then to booster U and V. Output 2 is connected to 18/19 and 36/37, then to command station U and V.

There is a Lenz command station and a booster, the booster is probably not needed most of the time. The output 36 way D connector has pins 1/2 command station J. 5/6 AC T1:1. Xpressnet L M A B is connected to D pins 8, 9, 10 and 11. 13/14 AC T1:1. 17/18 booster J 19/20 command station K. 23/24 AC T1:2 Lenz C D E from CS is on 25, 26 and 27. CD out is on 29 and 30. 31/32 AC T1:2. 35/36 booster K.

There are 10 fiddle yard tracks, 10 stationary trains at less than 100mA each, is less than 1 Amp. 6 running trains at less than 500mA is another 3 Amps. So the booster is probably not actually needed for running. What is needed is isolated power districts to allow some operation to continue when there is a derailment. We can have a switch so the fiddle yard DCC can be either from the command station or a booster.

New Wiring

Each baseboard has 2 x 25 way D connectors, connected to a 36 way tag strip. So some connections are on 2 or 3 D pins to carry more current. It looks from the list, as if the first 4 on each connector may have at least 2 pins.

The MERG CDU's take a short pulse of about 500mA to recharge, the pulse decoders only take about 30mA to recharge and 15mA normally. The CobaltIP's are 5mA and 40mA when moving. LED lights may be 10mA each. So after converting all the points to DCC operation, we can convert the power back to dc. This should then make the signal operation easier by having a fixed 0 Volt line. It should be possible to eliminate one of the 25 way D plug and sockets on some boards.

32/0.2 wire will have a resistance of 0.57 ohms for 100 feet, so fine for the DCC to the rails. 16/0.2 will be 1.14 ohms for 100 feet, so fine for 24 Volt dc which will only carry about 1 Amp. 7/0.2 will be 2.6 ohms for 100 feet, so fine for the Xpressnet A and B, or the track section data. The wires to the 20 D connectors and D connectors will increase the resistance a little, 20 x 0.03 = 0.6 ohms, and the DCC pins have 2 or 3 pins in parallel.

The control DCC should come directly from the command station, and must be protected from any rail connection. This is done by MERG DCO's(District Cutouts). Peco insulated frogs can cause shorts as the wheels of some locos pass over them, 54ms cut out delay is faster than the Lenz command station.
Kit 57, MERG DCO.

Tag strip connections

Tag	Main Connector	Tag	Fiddle Yard Connector	Front Connector	D pins	D pin Colours	Alternate D pin Colours
1	DCC common, Black 32/0.2	19	DCC common, Black 32/0.2	DCC common, Black 32/0.2	3	Black+Red, Black+Blue, Black	Black+Red, Black+Blue, Black
2	Main DCC, Red 32/0.2	20	Main DCC, Red 32/0.2	Main DCC, Red 32/0.2	3 or 2	Red, Red+Brown, Blue	Red, Red+Brown
3	Fiddle yard DCC, Orange 32/0.2	21	Fiddle yard DCC, Orange 32/0.2		2	Green, Yellow	Blue, Green
4	Signal outer CW	22	FY track 1	Fuel siding	2 or 3	Yellow+Red, Yellow+Blue	Yellow, Yellow+Red, Yellow+Blue
5	Signal outer CCW	23	FY track 2	Siding 1	2 or 1	White, Brown	White
6	Signal inner CW	24	FY track 3	Carriage 1	1	Purple	Brown
7	Signal inner CCW	25	FY track 4	Carriage 2	1	Orange	Purple
8		26	FY track 5	Siding 2	1	Pink	Orange
9		27	FY track 6	Siding 3	1	Turquoise	Pink
10		28	FY track 7	Point 39	1	Grey	Turquoise
11		29	FY track 8	Point 40	1	Red+Blue	Grey
12	CBUS Low, Yellow TP 7/0.2	30	FY track 9	Point 47	1	Green+Red	Red+Blue
13	CBUS High, Blue TP 7/0.2	31	FY track 10		1	White+Red	Green+Red
14	Xpressnet A, White TP 7/0.2	32			1	White+Blue	White+Red
15	Xpressnet B, Purple TP 7/0.2	33			1	Orange+Blue	White+Blue
16	DCC control, Green 16/0.2	34			1	White+Green	Orange+Blue
17	24 Volts DC, Pink 16/0.2	35			1	Yellow+Green	White+Green
18	0 Volts DC M, Brown 16/0.2	36			1 or 2	Orange+Green	Yellow+Green, Orange+Green

Where TP is a Twisted pair to reduce interference from the DCC.
The test track oval has the first D pin connections, the fiddle yard and main boards have the alternate connections. These are not compatible so the end fiddle yard and main boards have one of each to convert from one to the other.

Wire colours

There is a main bus of 10 wires running around the layout:

• Black 32/0.2, the DCC common. 7/0.2 wire can be used within a basboard.
• Red 32/0.2, the main track DCC, isolated by a MERG District Cutout.
• Orange 32/0.2, the fiddle yard DCC, isolated by a MERG District Cutout. We may need to split this into 2 power districts. Can be powered by a DCC booster.
• Blue and Yellow 7/0.2 twisted pair, MERG CBUS data using Bosch CAN.
• White and purple 7/0.2 twisted pair, Xpressnet A nd B. RS485 data.
• Green 16/0.2 (with Black DCC common), DCC control network direct from the command station.
• Pink and Brown 16/0.2, 24-28 Volt DC supply.

For local connections within a baseboard wires can be 7/0.2.
Local 12 volts supply for CBUS modules, Xpressnet L and M, lights etc is provided as necessary by a 12 Volt regulator. The wires are usually red and brown twisted together, red the positive (Xpressnet L) and brown the 0 volts (Xpressnet M).

DCC track sections over a baseboard joint need to use 16/0.2 wire.

JMRI Screen, with added DCC point addresses.

25 pin D connector wire colours

Pin	Test Track Colours
1	Black+Blue
2	Black
3	Red+Black
4	Red
5	Red+Brown
6	Blue
7	Green
8	Yellow
9	Yellow+Blue
10	Yellow+Red
11	White
12	Brown
13	Purple
14	Orange
15	Pink
16	Turquoise
17	Grey
18	Red+Blue
19	Green+Red
20	White+Red
21	White+Blue
22	Orange+Blue
23	White+Green
24	Yellow+Green
25	Orange+Green

TOP