My dentist occasionally gives me a lecture about practicing sound dental hygiene: by which he means brushing “properly” (which he demonstrates), flossing (I ain’t goin’ there) and the use of teeny weeny little brushes that look like tiny pipe cleaners of the type my mother used to clean her cigarette holders with when I was a sprog and she wanted to look like Rita Hayworth.
Of course, as he’s giving me the run down on “sound dental hygiene”, I diligently nod my head and as soon as I’m out of the place diligently ignore him till the day before my next visit when I use the tiny brushes to clean the crud from between my teeth.
An exchange of emails between myself and Marcus Ammann about 6 months ago put me in mind of my dentist because in them Marcus was warning me about the dire consequences of not using a common ground between the boosters on my DCC system. A common ground is really just a white connected to the negative side of the bridge rectifier in your DCC boosters that allows them to work together by eliminating electrical incompatibilities. If that last part sounds a bit vague then I’m willing to fess up and admit that this is deliberate because I’m buggered if I really understand what these “electrical incompatibilities” are. However when someone like Marcus Ammann or Mark Gurries tells you you need to install a common ground when you have a layout large enough to need electrical districts on your layout then you ignore them at your peril.
After Marcus gave me this warning and provided me with a link which led me to a bloody curdling story of a modeller who ignored this advice, he informed me that if I wanted to install this common ground wire I couldn’t use the Wangrow/System 1 booster I’d been using up till then. I diligently nodded my head (this was virtual nodding because Marcus couldn’t see me, this exchange being via email) and then I diligently ignored him. My thinking was that if I was going to implement sound DCC hygiene on my layout I would have to discard my perfectly good SYS1 booster and fork out approx $250 for a new NCE booster (a PB5 to be precise) to allow this to happen. PB5s are set up in such a way as to allow them to be connected in the required way. So nothing on the Morpeth line changed until…
During the most recent gathering of the Borderline Operators I got a recurrence of a problem with my control panels that I decided it was time to address. The problem was that about 50% of the time on starting up my DCC system my control panels simply refused to operate. I’d power the system down and start it up again and sometimes this would fix the problem but other times it didn’t. So last week I posted a description of the problem on the NCE-DCC Groups IO group and waited for a flood of responses. I got one response from Dennis DeGroff in the US who said he was having the same problem and that he’d contacted NCE about this and was waiting for their solution. Another modeller has since made contact with us and he has the same issue. So at least I could take heart from the fact that this wasn’t just my dodgy control panel building practices.
However quite a number of other responses ran along the lines of “have you got a common ground installed between the boosters?” Eventually I admitted that the answer to this was a no but could someone point in a direction of how to do this??? I was a little surprised when no one replied to this as I thought installing a common ground was common practice and that knowing how to do this would be common knowledge but evidently no it isn’t. Then Mark Gurries’ responded and pointed me to one of his excellent DCC web articles https://sites.google.com/site/markgurries/home/nce-info/nce-boosters/pb110-booster-grounding-issue which contained a description of how to modify my SYS1 booster so I could install the common ground and not have to fork out $250! Hoo-bloody-ray!
After I made this modification to my SYS1 booster I took a trip to the hardware store and purchased 12 meters (about 39′) of solid core wire to install as the common ground. When I originally installed my boosters under the layout it seemed logical to me that they needed to be as close as possible to the section of the layout they were powering, rather than all being gathered in one place. Having all your components in one spot would certainly have made running a common ground between boosters easy, as they would have been only a few inches apart, but mine were either side of an aisle with a wiring run needing about 12 meters of cable.
You see a booster is a sort of receiving station that communicates with your command station and which has its own dedicated power supply. The power supply for the Queens Wharf section of the layout on the right in the above photo is located under that section so that power for the trains only has to travel a couple of meters, not the 12 meters that would be required if I’d installed all my DCC components together in the cupboard labelled A. At heart you have separate boosters and their associated power supplies so as to reduce voltage drop from one section of a larger layout to another. It seemed to me that for this to make any sense the booster needed to be where the power was required. Anyway what this led to is that I needed a 12 meter long common ground to connect my boosters. I did enjoy reading in one of Mark Gurries’ articles that he can’t work out why people place all their DCC components in one spot unless it’s to impress visitors with their large rack of DCC components. I don’t want to impress anyone with my large rack so I spent this morning crawling around under my layout running my common ground wire.
After I got the common ground installed I turned the whole system on and got a short on the Queens Wharf side of the layout but this was cured by simply swapping the leads from the power pack over. This brought the two DC power supplies into phase on both sides of the layout. One of the quirks of a layout with separate boosters and districts but with no common ground is problems at the track boundary between the districts. In my case I occasionally got locos running over the boundary after which they’d slow and hesitate for a moment and then continue. A common ground cures this. After I got the system running I tested a loco over the boundary and there was a very small buzz and hesitation which I put down to a difference in the voltage between the QW and Morpeth districts. I was getting a reading of just over 17 volts at QW and 12.3 volts in Morpeth. The SYS1 booster has a switch on it that allows you to select a suitable voltage for large scale, HO or N so I switched this down to HO and this dropped the voltage at QW to 12.5 volts. This isn’t exactly the same voltage as Morpeth but it’s a lot closer and it cured the buzz and the very slight hesitation of the loco at the boundary.
Did installing the common ground cure the problem with the control panels? No but at least I can sleep at night knowing I’ve followed Marcus’ advice faithfully. Following my Dentist’s advice is a work in progress.
I’d like to thank Marcus Ammann, Mark Gurries, John Parker and Dennis DeGroff for their help and advice in getting this job done and hopefully eventually coming up with a solution to the issue around my control panels. All mistakes, misunderstandings and departures from sound DCC hygiene are totally mine and should not be sheeted home to the various DCC gurus I’ve consulted in the preparation of this blog post.