Power to R8247 Points Decoder

[Jonty66]

 

Hello and good afternoon,

I have recently installed elink/railmaster and to control the points a R8247 decoder.

I have installed the decoder according to the pdf document to the letter.

As I read on previous articles, I updated railmaster to the current version as I was having trouble getting Railmaster to communicate (not read) the decoder. Anyway, that is now all fine and I can read from and write to the decoder. However, when I then go to the track mimic and activate the require point I find that nothing happens. Could this be either of these three scenarios:

• the numbering of the various points - I notice on the mimic that the point numbers are 0001, wheras on the decoder set-up screen they are e.g. 1 to 4 etc. would this make the difference as they are not EXACTLY matched (however I canot change this on the mimic as they default to 0001).
• power to the decoder - I'm using a 1 amp supply to the track and accessory bus i.e. all power for everything comning from the 1 red and black bus (no sepearte bus for accessories). As I have over 20 'dropper' locations to the bus from the track, is it a case that the amount of droppers is starving the decoder of the 1 amp power, although I'm not running any locos when attempting to operate the decoder?
• I have diodes attached to the Gaugemaster seep point motors as they were previously installed for use with a Gaugemaster PCU1 DC set-up. Would they be interfering with the power to the decoder?

Many thanks again,

Jon

[St1ngr4y]

Hello Jon,

When you created the "mimic", you needed to allocate an address to each set of points which you added to the diagram. This address will correspond to the port on the decoder to which the points are wired physically. If you didn't do that, then edit your layout diagram, and for points 2, 3 and 4, right click on the points icon on the diagram and a small configuration window should appear, where you can enter the correct address for that point. Having done that, save the diagram and exit from the editor.

The number of droppers should not adversely affect the supply to the decoder.

I will leave your 3rd question to someone with more electrical knowledge than me, to answer.

Ray

[Chrissaf]

I concur with the advice given by Ray. The 0001 is the default address displayed on screen in RM. If all points on the mimic are all showing 0001  then you haven't yet allocated point addresses to the points on the mimic in 'track plan' design mode. Right click the point switching icon and fill in the menu that appears in a pop-up.

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With regard to the numbering. Yes 0001 is the same as 1, 0002 is the same as 2 (all leading zeros are ignored).

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With regard to the third point regarding diodes. This is something I researched before to help another forum user. As long as they are wired in as per the instructions for the PCU1 (analogue point control switch unit) then they will be in series with the firing wire of each solenoid coil. Both the PCU1 and the R8247 use positive common return. Thus the diodes will not stop the current flowing, but they will have a voltage drop across them (if based on silicon, the diodes will drop 0.6 volts). This doesn't seem like much, but the output of the R8247 is a relatively low voltage, compared to that of the PCU1. There is a risk, albeit small, that the 0.6 volt voltage drop may be enough to prevent the Seep solenoids operating robustly. Whether to remove them (the diodes) or not will depend upon how your Seeps operate in your particular layout. You will need to make that assessment yourself, once you have got basic operation configured with RM correctly.

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Even if solenoid firing is affected by the diodes, your solenoids should still have some movement and make a click. Sufficient enough for you to ascertain that the Railmaster mimic setup has now been correctly configured. i.e you can hear that the Seeps are trying to operate when you click the appropriate RM mimic icon.

 

 

[Jonty66]

 Thanks Ray,

I have used the drop down box to allocate the point numbers on the track plan to those on the decoder that also correspond to the accessory set-up screen. My question is do they have to match exactly? On the accessory set-up screen and drop down box they appear as 1, 2 etc, whilst on the track plan they appear 0001, 0002 etc. Should this make a difference?

Jon

 

[Chrissaf]

No

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PS - Jonty, I've just realised that it was your previous post that I did the PCU1 research for. In that post, you indicated that removing the diodes would not be impossible but would be difficult.

[Chrissaf]

Jonty, although not directly related to your issue. This previous dialogue I had with another user demonstrates the importance of perfect Seep alignment when using Seeps with the R8247. Your original PCU1 contained a very powerful CDU. This additional power would easily compensate for any Seep poor alignment introduced during their original installation. The forum user in the linked post, did successfully use Seep with a R8247, but it took careful alignment to get the operation reliable (albeit in his case his issue was with using the Seep frog switch).

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I have included this additional information just in case you find yourself in a situation where you get RM / eLink to fire the Seep, but not robustly.

[Jonty66]

 Hi Chris, now you come to mention it I did hear a slight click when attempting to activate from the track plan. Would it be worth my while upgrading from a 1 to 4 amp power supply to overcome the decoder's low power output? If not it looks like a check of the alignment is next!

Jon

[Chrissaf]

I'm afraid not Jonty. The R8247 will draw just the current it needs. It doesn't matter whether the power supply can supply 1 amp or 100 amps you won't see a difference. In this scenario it is the voltage that is the crucial electrical parameter. The voltage output of the R8247 is constrained by the DCC input voltage, coupled with (presumably to keep costs down) a not very powerful internal CDU.

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The R8247 draws about 15-20 mA in idle, peaking to about 150-220 mA during charging (after firing a point). The R8247 uses the stored energy in its internal CDU to fire the solenoid point. Thus the amount of current the power supply can provide is irrelevant.

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If you can find one point where removing the diodes is more easily feasible, then you can observe the difference between the circuit having and not having the additional voltage drop introduced by them. Assuming, that you now have RM configured correctly to operate the points, if you can hear a click but the point doesn't throw, then I would suspect alignment as being the culprit (or wiring see last paragraph below). I appreciate that they probably worked fine with the PCU1, but that is a much more powerful device compared to a R8247.

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I believe others on here have indicated that perfect alignment of the motors is a crucial requirement as well when using the R8247.

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There is another alternative. Connect relays to the output of the R8247 and use the relay contacts to fire a dedicated CDU with separate external power supply to operate your Seeps. I appreciate that this adds more complexity, but would be a fall back solution if all other options fail to deliver a working solution. This is the one I ended up adopting to reliably fire my so called low energy PL-10WE Peco solenoid point motors. These PL-10WE motors have much higher resistance coils. Yes, this does reduce the current (making them lower energy), but I found I had to increase the firing voltage to 19 volts to get them to fire reliably and robustly. The output of the R8247 is nearer 15 volts (peak) and just couldn't hack it.

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Also, make absolutely sure that you have them wired correctly. The Seep C tag goes to the R8247 C terminal. The Seep A & B tags go to the R8247 + & - terminals. It has been known for people who experience just hearing a click but no noticeable movement to have cross wired the wire on the C terminal with one or other of the other two.