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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The documentation for the current wiring is patchy, out of date, and wrong.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.

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.
MERG DCC steady state decoder.
Kit 53 firmware in C.

The end boards have a 3 position switch, local control, off, and remote control. The 2 latching push buttons work when in local control. The middle off position puts both crossovers straight to give 4 parallel tracks. The remote control position allows DCC control of the crossovers.

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. 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.
2. These may get changed to Cobalt IP point motors.

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

An 18 volt switched mode power supply at about 7 amps should be fine, but we need to test this before the show. All but 2 or 3 points work on 18 volts, these 2 or 3 need some work to fix them.

There is a Lenz command station and a booster, the booster is probably not needed most of the time. The output is a 37 way D connector:

Pins	Connection
1, 2	Command station J
5, 6	AC Transformer 1 winding 1
8	Xpressnet L
9	Xpressnet M
10	Xpressnet A
11	Xpressnet B
13, 14	AC Transformer 1 winding 1
17, 18	Booster J
19, 20	Command station K
23, 24	AC Transformer 1 winding 2
25	C from CS
26	D from CS
27	E from CS
29	D to booster
30	C to booster
31, 32	AC Transformer 1 winding 2
35, 36	Booster K

The CDE lines don't need to go up the main cable to the layout. The 18 volt supply wiring from the transformer is now protected by a 3 amp polyfuse. This device is a low resistance (0.5 Ohm) at normal current and room temperature, but at high current it gets hot and the resistance increases to reduce the current.

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. The front yard may need to be another protected area.

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

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 at least 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

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