South Downs Railway

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MSC8 controller for Portsmouth engine shed

This was fairly simple: an MSC8 scenery animator to control effects in and around the engine shed at Portsmouth. The unit itself is mounted under the Portsmouth baseboard, and powered by accessory DCC track power. Its outputs are as follows:

Output DCC  Function  CVs 
573     
574  servo: engine shed door   CV10=4; CV54=220; CV55=60 
575  servo: yard gate   
4 576 on/off lighting in engine shed CV12=2
5 577 welding in shed CV13=0; CV21=1
6 578    
7 579    
8 580    

Broken Turntable!

Out turntable is a Fleischmann 9152 powered by a CML Electronics TXC1. During a recent operating session, we found the DCS100 command station beeping 24 times when it powered up; thereafter LocoNet devices including throttles didn't work. 24 beeps isn't a recognised code - what was happening?

I measured the LocoNet voltage from pin 2 to pin 3 on a LocoNet cable - around 8V. That's far too low - with no throttles attached it should sit at around 13v. The LocoNet is sectioned, so we were able quickly to isolate the problem to the Portsmouth area, then by elimination to the TXC1.

The TXC1 has an 18 ohm resistor between its power ground and LocoNet ground: that resistor was discoloured through overheating. Experience says that is a power supply problem (for example if the board power feed is biased relative to mains ground). It was a new power supply, but that wasn't the case. It turns out the 3 red/yellow/grey wires from the turntable were biased to half track voltage.

After taking off the turntable bridge and disassembling the mechanism, a possible cause was clear: there is a phosphor bronze springy strip running under each rail, and therefore under the body of the motor. The way the strip was mounted, it was springing up slightly (how far would be temperature dependent) and it could have made contact with the body of the motor. I've now attached a very think strip of plastic card to the springy strip and glued it down, so that it should remain isolated from the motor. I also took the opportunity to bypass the relay that isolates one track end on the bridge, so the full length of the bridge is now permanently powered.

turntable bridge modified

And... two days later the problem came back. I was able to remove the turntable bridge from the turntable (so it looks like the picture above) and still measure 0 ohms from a rail connection to the motor feeds: so there was conclusive proof that the turntable, not the controller, was at fault; and the problem wasn't in the slip rings. But it was the other rail that was shorted (the bottom rail as protographed above), with no obvious way for that to happen. In the end I removed the relay that isolates part of the track at the bridge ends, and all has been fine ever since. I've soldered the rail gap, so the bridge track is now powered along its full length.

 

List of Scenery outputs

This is a definitive list of all controlled scenery items on the South Downs Railway. (Note bold numbers are the ones to activate manually; the others operate automatically from that)

 

MSC8DCCItemComment
1 501 Clanfield windmill motor 50Hz motor.
1 502 Windmill light: yellow LED flickering lamp effect
1 503 Clanfield church lighting PWM lighting output
1 504 Clanfield station building lighting PWM lighting output
1 505 clanfield station platform lights PWM lighting output
1 506-508 house lights 2-4  PWM light; often on sequence
2 509 shops downstairs lights PWM light
2 510-515 shop upstairs lights 1-6 PWM light; often on sequence
2 516 house light 1 PWM light; often on sequence
3 517-524 house lights 5-12 PWM light; often on sequence
4 525

factory smoke generator

on 1 minute every 5 minutes

CV9=7; CV7=127; CV17=7

4 526

reserved for ladder raising servo

on when o/p 1 sequence active

 CV10=4; CV33=1
4 527

fire engine lights

on when o/p 1 sequence active

on when smoke generator on; flashing light sequence

CV11=0; CV19=4; CV36=1

4 528 always on downstairs light (&3 other factory buildings)

PWM light

CV12=2; CV20=0

4 529

fire light 1

on when o/p 1 sequence active

no PWM; flickering light; on when smoke generator on

CV13=1; CV21=6; CV42=1

4 530

fire light 2

on when o/p 1 sequence active

no PWM; flickering light; on when smoke generator on

CV14=1; CV22=6; CV47=20; CV45=1

4 531

fire station flashing lights,

turned on when o/p 8 sequence is active

 

CV15=0; CV23=4; CV48=128

4 532 sequence for flashing light in fire station

 on infrequently (house light 2 sequence)

CV16=0; CV24=3

5 533 Level crossing flashing light by Petersfield station.

CV9=9; CV6=64 (sets blink rate)

5 534 servo for barrier 1 (rear)

CV10=4

CV58=0 (no bounce); CV60=5 (tiny off selay)

5 535

servo for barrier 2 (front)

enabled when DCC command for output 2 is active

CV11=4

CV37=2

CV65=0 (no bounce); CV62=190 (barrier down position); CV67=5 (tiny off selay)

5 536    
5 537    
5 538    
5 539    
5 540    
6 541-8 house lights in Clanfield area

PWM lights; mix of "often on" and "less often on" sequences.

CV9=6 (DC motor); CV10-16=1 (fast PWM)

CV17,19,21,23=2 (house light 1); CV18,20,22,24=3 (house light 2, for upstairs lights)

CV32, 35, 38, 41, 44, 47, 50, 53 are random values in range 0-255

DCC gate CVs (34, 37, 40, 43, 46, 49, 52) all set to 1 so o/p 1 turns on or off all lights

7 549-556 house lights in Clanfield area

PWM lights; mix of "often on" and "less often on" sequences.

CV9=6 (DC motor); CV10-16=1 (fast PWM)

CV17,19,21,23=2 (house light 1); CV18,20,22,24=3 (house light 2, for upstairs lights)

CV32, 35, 38, 41, 44, 47, 50, 53 are random values in range 0-255

DCC gate CVs (34, 37, 40, 43, 46, 49, 52) all set to 1 so o/p 1 turns on or off all lights

8 557-564 house lights in Clanfield area

PWM lights; mix of "often on" and "less often on" sequences.

CV9=6 (DC motor); CV10-16=1 (fast PWM)

CV17,19,21,23=2 (house light 1); CV18,20,22,24=3 (house light 2, for upstairs lights)

CV32, 35, 38, 41, 44, 47, 50, 53 are random values in range 0-255

DCC gate CVs (34, 37, 40, 43, 46, 49, 52) all set to 1 so o/p 1 turns on or off all lights

9 565-572 house lights in Clanfield area

PWM lights; mix of "often on" and "less often on" sequences.

CV9=6 (DC motor); CV10-16=1 (fast PWM)

CV17,19,21,23=2 (house light 1); CV18,20,22,24=3 (house light 2, for upstairs lights)

CV32, 35, 38, 41, 44, 47, 50, 53 are random values in range 0-255

DCC gate CVs (34, 37, 40, 43, 46, 49, 52) all set to 1 so o/p 1 turns on or off all lights

10 573-581 Portsmouth engine shed  

 

 

Effects are always THROWN for ON; CLOSED for OFF.

 

MSC8 number 4 has several outputs controlled by one operation. The smoke generator is operated by a sequence; it is on for approx 1 minute every 5 minutes. When the smoke generator output is active (i.e. for that 1 minute when the building is on fire) outputs 2, 3, 5 & 6 are activated. These then have their own sequences: to flash the fire engine lights, and to flicker LEDs to look like the fire itself.

MSC8 number 4 Output 7 has 2 sequences: a sequence that flashed the lights like a fire engine; and that whole output is turned on or off by output 8, which is on infrequently. This will give the appearance that a fire engine inside the fire station has its lights tested periodically.

 

 

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