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Wiring help with fiddle yard throat

paul.b

By paul.b
in Hornby DCC

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paul.b

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Hi just a quick update with the fiddle yard throat got all points fitted and connected to a new ads8sx and it works perfectly took a while to do but very pleased ....

On a side note now that i have connected another ads8sx to my layout when i power on the elite the green light blinks and i get an error as if i have a short, if i switch the elite off and on it powers up ok, could this be down to  5 ads8sx and 4 ads2sx on the layout i`m using a hornby 4amp psu with the elite

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This exact issue has been raised before:

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The ADS..... products have inbuilt CDUs (Capacitor Discharge Units). At the instant of the initial power up these capacitors will all be fully discharged. Electronically they individually look like a 'short circuit' at the instant of powering up. As the capacitors charge, the internal impedance rises rapidly. The rise in impedance makes the current through them fall. You have quite a lot of ADS ports, thus an equally high number of capacitors all sucking current from your 4AMP supply. As the capacitors charge up, the current drawn from the power supply rapidly reduces.

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This initial in-rush current of all the individual capacitors is aggregating together to attain the current level that the Elite uses to detect a 'short circuit' condition.

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However, when you reset the Elite and power it up the second time, the CDUs in the ADS.... decoders will have a partial charge already in them. Thus the new in-rush current will be at a far lower level than the initial power up and fails to reach the 'short circuit' trigger current. Thus why the Elite power up is successful at the second attempt.

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How to rectify this issue is not something for which a guaranteed solution can be offered. There are a couple of things that might work, but each possible solution has a significant cost association with it and would be subject to a certain amount of trial and error.

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If you can still get them from old shop stock (they are actually obsolete by Hornby) you could use the Hornby R8239 Booster. Being obsolete, you may need to shop around to find a supplier with stock.

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The R8239 comes with another 4AMP Hornby P9300 power supply. Either ALL or some of your ADS....decoders would then connect to a separate dedicated DCC Bus powered by the R8239 power supply.

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I would suggest putting the 5  x ADS8SX on the second DCC Bus powered via the R8239 and leave the 4 x ADS2SX connected on the existing DCC Bus powered from the Elite as they currently are. By distributing all the ADS decoders across TWO power supplies you have a higher chance of success. If on the other hand, you put all 9 x ADS.... on the R8239 Bus circuit then it might be possible that they will still draw more in-rush current than a single 4 AMP supply can handle.

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Alternative solution only applicable if you have RailMaster software. Some on here will probably suggest using a two A & B controller solution with your Elite as Controller A controlling your track and locos, and an eLink as Controller B connected to the ADS decoders. This approach has issues.

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  • Firstly, this only works with RailMaster.
  • Secondly, the eLink 1AMP power supply would probably need to be upgraded to 4AMPs anyway (additional cost of the higher current supply).
  • Thirdly, all the ADS decoders will have to be controlled by Controller B. Because the way that RailMaster handles the use of a TWO controller configuration requires ALL the point decoders to be connected to Controller B.
  • Fourthly, because ALL the decoders have to be via Controller B, then that controllers power supply has to have enough current to power ALL the decoders. That is to say that you will not be able to split your decoders across two power supplies as you can do using the R8239 solution.

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The R8239 solution is expandable. If you were to find (but I think that this would be unlikely) that one additional 4 AMP supply via an R8239 was not enough. Then the total number of ADS decoders could be further split into three blocks of  3 decoders each, with the third block powered by a second R8239 using its own dedicated 4 AMP power supply. Thus you would potentially have access to 12 AMPs of current.

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The drawing below only shows the first R8239 being used i.e total of 8 AMPs. If the 2nd R8239 was implemented (dotted lines). Then all the ADS decoders could be potentially evenly distributed across two or three power supplies.

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/media/tinymce_upload/2a6313621ba60a12b4d0ef80b0d67051.jpg

 

 

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Thank you Chris for such a full explanation,i have had a look for a booster found a few on ebay but at £90 its a bit much as long as i will not damage my elite everytime i power up and reset to get it running i might leave as is 

paul..... 

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Well making any Elite go into 'short circuit' error mode is going to stress it electronically, including the 4 AMP power supply itself. The accumulative stress is going to be higher in the longer term if this happens at each and every start of session power up.

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Before someone else suggests it. As a really cheap solution. You could put your ADS decoders into two banks as suggested in my first reply. Then feed the DCC Bus connection into the second bank of ADS decoders via a double pole toggle on/off switch. So what would happen then is, you power up the first bank of ADS decoders via the Elite power supply (with the second bank isolated via the on/off toggle switch). Then once the first bank of ADS decoders are fully charged up, throw the switch to bring the second bank of ADS decoders online so that they can charge up as a separate activity via the Elite power supply. In other words, you are reducing the initial in-rush current into two separate peak loads a few seconds apart as opposed to all the current being required in one single hit.

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The potential issues with that are:

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  1. Remembering to disconnect the second bank of ADS decoders at the end of a play session so that they are not in circuit at the next power up.
  2. DCC data signals could possibly in my opinion be temperamental when passed through switches. But it is a simple enough solution to trial first to see if it gives a complete robust long term solution.
  3. If you add even more ADS decoders at a later date, you might find the Elite 4 AMP power supply still struggling to cope with the normal background current load when also operating a number of simultaneous locos pulling trains.

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Hattons used to sell the R8239 for less than the cost of a P9300 4 AMP power supply (about £35) but they have now sold out.

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Hi Chriss i had a little play around today and the new ads8sx and ads2sx i add this week i wired them to a double pole switch so now when i power on the elite it powers up ok once powered up i throw the switch to the other ads sx and everything is ok no issues so far, but i might invest in a booster and do as you suggested about the 5 ads8sx 

 

paul....

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Guest Chrissaf

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Paul, it is really nice for a change to have someone who just needs a little nudge in the right direction, goes away and implements a working solution with little further guidance. There are some who need to be spoon fed every single step of the way. Take for example your ADS decoders. Not once did you raise any issues about configuring their DCC addresses (well not in this thread anyway). Then you also took my guidance on the RLM issue and successfully implemented that without further assistance. Then you took Ray's guidance on configuring the throat points in RailMaster and it seems you have also turned that into a working solution without further drama. It has been a pleasure to help you.

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Chris

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PS - I'm really glad to hear that your custom fiddle yard throat points worked first time for you. They did look really complicated.

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EDIT: Found these.....might interest you.

https://www.ebay.co.uk/itm/HORNBY-R8239 (truncated URL)

https://railsofsheffield.com/products/7729/hornby-r8239(truncated URL)

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TIP: If you do buy and fit a R8239 Booster. Do not use the RJ11 cable connection to the Elite. This has proven to be a little unreliable. Use the option documented in the instruction sheet (extract image below) where you connect the R8239 to the Elite Track A&B output (via the DCC Bus) connection instead.

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In principle the same as below, but without using the track or the track power clips. The 'Main Power Area' in the drawing represents the layout DCC Bus that powers the layout track. The 'Secondary Power Area' in the drawing represents the separate DCC Bus connected just to the ADS decoders.

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/media/tinymce_upload/6193719253fe062a2da64ae509a1b5ee.jpg

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Thanks again chriss your explainations were very clear and easy to follow i have learned alot this past week or so with your and Ray... my next task is to use railmaster and program the points so that i can with the click of a button on screen set the points from each throat entrance to any fiddle yard siding  as in the pic below 

program  A1 A2 A3 A4 A5 and B2 B3 B4 B5 B6 if you get what i mean 

/media/tinymce_upload/5a1fc9622d80969d867f857c3c033eda.jpg

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Well that video does confirm 100% that the CDU capacitor in-rush current is the issue. I have looked on the DCC Concepts website and can find absolutely no mention of this 'short circuit fix' product. The You-Tube video is somewhat unhelpful in not stating the product order code for it or availability.

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So I assume that you will be contacting DCC Concepts next week to chase them for the product details. I have posted a product image taken from the video for the information of forum members reading this thread, but if you could come back and fill in the details about how to source these (with part numbers) if you get some. Then that will be extremely helpful for others.

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/media/tinymce_upload/7d71b6f0173ea39902a5502511e580e0.jpg

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Fishy will be pleased as he suggested that DCC Concepts should provide a 'short circuit fix' device to add into the DCC circuit in his earlier reply.

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I am rather surprised that DCC Concepts are aware of this issue (since they have developed a solution for it) but do not appear to have documented it at all on their website or in the online AD-Sxxxxx product manuals.

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For readers that do not feel like wading through the 12 minute YouTube video. The product in the plastic bag goes in series with the DCC input feed to the AD-S decoders and presumably restricts the peak value of the CDU capacitor in-rush current flow. For readers that are going to watch the You-Tube anyway, the product is discussed from 5 minutes 45 seconds into the video.

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I have had a response from Dcc Concepts as follows 

 

 

Hi Paul

  It looks like the Elite, (albeit with 4 Amps at its disposal) is overloading when it tries to charge up 48 mini-CDUs' capacitors in one go.   A quick solution is to put a switch between the bus and every two ADS-8s, the remaining ADS-8 and the four ADS-2s (or variations of this to suit the geography of your layout wiring). Boot up the Elite and then switch in each set of ADS' in sequence - give each about 30 seconds to charge up.   A bit like starting up a four engined aircraft!   You will probably find that, if you turn everything off to go to the shops and return within a few hours, the system will boot up nicely without this staged approach (the capacitors will have retained their charge and so will not place demands on the system)   I have copied a colleague to see if there are any other fixes    Best regards   Chris

 

  I have replied to this and sent them a pic of the gizzmo that Chriss posted and a link to the youtube video   paul....

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Interesting that they offered the same cheap solution that I suggested, that is to say the isolating double pole switch. Will also be interesting to see what they come back with regarding the picture you subsequently sent them. Rhetorical question: why didn't they mention this fix product in their first reply?......could it be that they are not offering that fix product any more !!

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Hi Chriss i just had another reply from Dcc Concepts 

 

Hi Paul

 Yes indeed - these can cure the problem but I was a bit cautious recommending them for your 5 x ADS-8 and 4 x ADS-2.  I shall confer with my colleagues tomorrow !!  I will contact you either way  and, if they are indeed suitable, I will send some off to you !! Worse case is that your ADS' defeats them and we need to revert to staged switching on Kind regards Chris
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It seems as if the reason he may be being cautious is 'Yes' individually they reduce the in-rush current of a single AD-S decoder. But as you have 9 of them, he may be concerned that even with these fitted, the aggregated initial current draw for 9 units is still too high. Hence why he wants to consult with colleagues first.

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On a positive note: this in-rush current issue does indicate that the CDUs included in the DCC Concepts AD-S decoder products are powerful ones and have higher capacitor values than your average accessory decoder. Which is good for consistent reliable solenoid point switching. If I recall correctly, I vaguely remember a DCC Concepts Marketing claim that these decoders were the most powerful available in the market (at the time that they made the claim).

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Hi Chriss

Dcc Concepts has just sent this email

 

Hi Paul

 These will indeed sort out the problem between the Elite and ADSs. Let me know your address and I will post them to you FOC Best regards Chris Looks like this problem maybe sorted for free  😀
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Good to hear, any chance of a close up photo of both the front and the rear when you get them. I would like (for my own interest) to try and 'back enginneer' the circuit (tracing pcb component tracks) to try and see how they work.

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Hi Guys 

i have this all set up and all was running fine till last night when i put my R1155 Pendolino on the layout it didnt do it all the time but now and again it would stop and trip the elite the elite would reset and the loco would set off again. I have included a pic that Chrissaf uploaded to show where this is happening as i said its not everytime but now and again

/media/tinymce_upload/87191e38c9f7bed4d484f50eec74bb7a.jpg

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