Use of CDU and relay panels for DCC points

[96RAF]

Mainly for Chris and Flashbang but open to suggestions from other experts in the field...

 

Ref Chris’s various posts about using relays to allow DCC to gain the advantage of a CDU to fire solenoid point motors and Brians diagrams on his website.

 

I have decided to bin my very reliable centralised but metre long huge car relay points panel . . . 

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. . . in favour of regionalised points decoders and one of these miniature 8-relay panels for each PAD.

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... unfortunately although I thought I had ordered 12v relays the ones that came are 5v and although directly compatible with Arduino or Ras-Pi, etc may give me grief for use with DCC PADs output.

 

My question about using these relays is ...

.... will they take the momentary 12v thump from an R8247 (PAD) point and accessory decoder like my old car relays did.

If not what do I need to do to tame the PAD output so as not to kill my new relay panel.

 

[Chrissaf]

They look to be more sophisticated than just straight forward relay interface boards. It is not clear from the image what the quad leg semi-conductor blocks are. Although the relay itself may be able to take a very brief 12 volt pulse. There is a lot of additional component circuitry there on show too, that could very well be optimised for Arduino . PI processor board 5 volt logic. If those quad semi-conductor blocks are 5volt VCC logic operation, then 12 volts would blow them.

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To offer any more of a detailed assessment, I would need to see some form of product circuit schematic and a list of semi-conductor part numbers to research their data-sheets. Even magnified I cannot read the part numbers directly from the photo image.

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EDIT: After a closer look.

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You could possibly use opto isolators. These are 4 (or 6) pin devices that can have 12 volts on their input and 5 volts on their outputs. This would require your boards to have a +5volt VCC input on them in addition to the individual +5 volt trigger inputs. This would involve having a separate 5 volt power supply to power the boards. Looking at the pin terminal strip in the photo it has Gnd, In1 to In8 plus VCC. This infers that an optical isolation solution might be possible. I will dig a little deeper and come back with a further update later.

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UPDATE:

Rob sent me the full product information for his relay board privately via the ComMod email system. As a result of reviewing the documentation he sent, it appears Rob's requirement is doable. This is a copy for completeness of info in the thread of what I sent back to him. Rob needs to test this tentatively to confirm it is OK as I didn't have the actual relay HW kit myself to play with. It relies on the circuit schematics he sent me containing accurate and up to date information. It turned out that the quad semi-conductor blocks I was querying were on-board Optical Isolator chips.

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[96RAF]

Thanks Chris

It makes more sense reading the documentation through a different pair of eyes.

[Chrissaf]

Interesting, that the really useful documentation was in the docs for the quad relay board, the same information was not replicated in the octo relay board. Conversely, there was some info in the octo board docs that were not in the quad board docs. It took reading all the docs and mixing and matching the document contents to get the full picture of the product capabilities. It seems as if the two boards were developed at different times, and the documentation written separately as well.

[Northome]

I have several of the 2 module versions of these boards currently on my layout,  there are several Versions of these boads available, as well as 1,2,4,6,8 and 10 module boards in 5,12,24 volt, there is also 2 different variants,  One of which is purely optical input for Arduino/pi (lo switching), and the other variant has both Hi and lo switching controlled by jumper setting this is mainly the variant I use in the 12v version and thus far has no issues bieng thrown by 18v Aux power supply.  

 

I do have a couple of the Opto 5v version and found a modification to covert to Hi v Switching but this meant "butchering" the Printed circuit by cutting some of the trace's and all though they do work fine, Its not really best practice i suppose, again these are 5v modified to hi switch and seem to work fine with the 18v.

Hope this may be of use?

Rob

[Northome]

If you do a google be sure to include "High/low level" in your search they come in all module formats.

[96RAF]

A pity I hadn’t known about these variations before I ordered, but they will come in handy for other things, maybe I can use them with an Arduino to automate my layout wiring or operate my signal lamps instead.