Nigelcliffe Posted October 20, 2015 Share Posted October 20, 2015 Maybe my questions will be a bit out of the thread but I m considering fitting a large layout with cobalt digital decoders to spare wiring time , but I have read some experiences of decoders being out of order after a short period of time could some owners state about the long term reliability of those digital decoder ? Many thanks in advance for your reply My concern about the Cobalt Digital and the Cobalt IP Digital is the maker's intention that they are wired with track power. Whilst this looks attractive (saves wiring), it creates a minefield of problems in use - any short which shuts down the track feed also shuts down turnout control. The usual recommendation for wiring is to run two different DCC bus feeds around the layout. One for accessories (turnouts, signals, etc), and one to the track. The track feed should go through a circuit breaker which will trip on a short, leaving the accessory bus fully operational. For larger layouts, the track feed can be split into different zones, each with its own breaker, thus a short in one area only shuts down that area, and the remainder of the layout remains operational. Unfortunately, as shipped, the Cobalt Digital and the Cobalt IP Digital has the "looks simple, but creates problems" contact for the turnout crossing (frog). This is connected to the DCC signal input, so using that output means that wiring onto a separate accessory bus is broken as soon as the crossing is connected (the track system is now cross-connected to the accessory). One of the most common DCC short circuits is driving a train into the crossing of a turnout set against a train, so the power breaker is bypassed and the short occurs. The problem can be got round by using the other contact switch on the device, but that's now used up a set of contacts. In most cases, that's fine, but you may have cases where the second contact is required. Finally, again as shipped, the Cobalt Digital (but not the newer IP model) in some markets had some extra wiring advice. Apparently on some DCC systems the Cobalt Digital would be over-voltage and burn out. So, to fix this a series resistor is recommended with the track feed to limit the current. This is fine, except that it also seriously limits the current to the crossing (frog) output, so much so that the crossing is effectively a "dead frog" ( Doh!! ). To switch the crossing (frog), it is therefore essential to use the other contacts. The newer Cobalt IP Digital seem to have removed the power issue (last point above). But still has the over-simplified crossing (frog) output, which shorts the accessory bus, or you have to use the other contacts on the switch to operate the crossing correctly. So, in summary, my concerns are not about the reliability of the product, but how it is installed. It can be installed so that the problems above are all removed. But this means knowing which bits of the maker's instructions are best ignored, and which should be followed. - Nigel Link to post Share on other sites More sharing options...
portsladepete Posted October 20, 2015 Share Posted October 20, 2015 Hi there, I've just got a Cobalt IP type,sorry if you have aleady tried this but in my instructions it says the following: To swap over direction of throw Put the switch into Set position Set cobalt address to 197 Then use same procedure as for activation Pete Link to post Share on other sites More sharing options...
barrowroad Posted October 20, 2015 Share Posted October 20, 2015 My concern about the Cobalt Digital and the Cobalt IP Digital is the maker's intention that they are wired with track power. Whilst this looks attractive (saves wiring), it creates a minefield of problems in use - any short which shuts down the track feed also shuts down turnout control. The usual recommendation for wiring is to run two different DCC bus feeds around the layout. One for accessories (turnouts, signals, etc), and one to the track. The track feed should go through a circuit breaker which will trip on a short, leaving the accessory bus fully operational. For larger layouts, the track feed can be split into different zones, each with its own breaker, thus a short in one area only shuts down that area, and the remainder of the layout remains operational. Unfortunately, as shipped, the Cobalt Digital and the Cobalt IP Digital has the "looks simple, but creates problems" contact for the turnout crossing (frog). This is connected to the DCC signal input, so using that output means that wiring onto a separate accessory bus is broken as soon as the crossing is connected (the track system is now cross-connected to the accessory). One of the most common DCC short circuits is driving a train into the crossing of a turnout set against a train, so the power breaker is bypassed and the short occurs. The problem can be got round by using the other contact switch on the device, but that's now used up a set of contacts. In most cases, that's fine, but you may have cases where the second contact is required. Finally, again as shipped, the Cobalt Digital (but not the newer IP model) in some markets had some extra wiring advice. Apparently on some DCC systems the Cobalt Digital would be over-voltage and burn out. So, to fix this a series resistor is recommended with the track feed to limit the current. This is fine, except that it also seriously limits the current to the crossing (frog) output, so much so that the crossing is effectively a "dead frog" ( Doh!! ). To switch the crossing (frog), it is therefore essential to use the other contacts. The newer Cobalt IP Digital seem to have removed the power issue (last point above). But still has the over-simplified crossing (frog) output, which shorts the accessory bus, or you have to use the other contacts on the switch to operate the crossing correctly. So, in summary, my concerns are not about the reliability of the product, but how it is installed. It can be installed so that the problems above are all removed. But this means knowing which bits of the maker's instructions are best ignored, and which should be followed. - Nigel Hi Nigel, Thank you for pointing out the problem with these units. I am currently wiring my Bristol Barrow Road layout for DCC and having purchased 24 of the Cobalt Digital units I would be grateful if you could clarify which of the 8 terminals I should use for connecting the crossing. I intend using seperate DCC bus feeds for the Cobalt Digital motors. I assume I should use terminals 1 and 2 to connect to this BUS. Which of the remaining terminals should I use for the crossing - obviously not terminal 3 [the frog crossing]. Robin Link to post Share on other sites More sharing options...
Nigelcliffe Posted October 21, 2015 Share Posted October 21, 2015 Hi Nigel, Thank you for pointing out the problem with these units. I am currently wiring my Bristol Barrow Road layout for DCC and having purchased 24 of the Cobalt Digital units I would be grateful if you could clarify which of the 8 terminals I should use for connecting the crossing. I intend using seperate DCC bus feeds for the Cobalt Digital motors. I assume I should use terminals 1 and 2 to connect to this BUS. Which of the remaining terminals should I use for the crossing - obviously not terminal 3 [the frog crossing]. Robin Just to confuse things, DCC Concepts seem to have changed the terminals between the Cobalt Digital and the more recent Cobalt IP Digital. So, be sure which you are using ! For both, the input (DCC from turnout/accessory bus) is terminals 1 and 2. According to the manual I have for both, the Cobalt Digital has switch terminals on 6,7,8. The common crossing (frog) being 8. The Cobalt IP Digital has switch terminals on 4,5,6. The common crossing is on 6. - Nigel Link to post Share on other sites More sharing options...
Talltim Posted October 21, 2015 Share Posted October 21, 2015 I'm looking into this too. I'd originally wired up using the track bus, but realised the problem when I ran a loco onto the V of a wrongly set point.My original thinking was that as I was building a Freemo module it would be good to not need any external power supply (track power being supplied through the bus from adjacent modules) but a short in this situation can obviously shut down a large section of layout with other people's modules, more embarrassing than just shutting down your own layout.I actually used the module in anger set up using track bus power as I didn't have time to change it and it didn't cause a problem, even with 40 different operators who had never seen my module before, but I would like to change it before next time.Of course running beyond the V onto incorrectly set blades will still cause a short, but at least the point can be changed to end the short. To make things complicated I only have two points, but one has an original digital and one a new IP digital... For the original Digital the instruction are on page 7 https://clarahost.clara.net/www.bromsgrovemodels.co.uk/assets/own/cobalt_digital.pdf 1 DCC Accessory bus or external power supply 2 DCC Accessory bus or external power supply 3 Not in use 4 Push button (if used) 5 Push button (if used) 6 DCC Track bus 7 DCC Track bus 8 Point frog/V For the Digital IP http://www.dccconcepts.com/vamr/owners-manual-cobalt-ip-digital-point-motors 1 DCC Accessory bus or external power supply 2 DCC Accessory bus or external power supply 3 Not in use 4 DCC Track bus 5 DCC Track bus 6 Point frog/V 7 Push button (if used) 8 Not in use 9 Push button (if used) Link to post Share on other sites More sharing options...
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