Wiring of R406 signal lights to R8247 Decoder

[Chrissaf]

pictures of the unit and packaging for referance, this was bought from a Hornby stockest so hope its an orignal (got the correct codes on back).

 

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[Fishmanoz]

Welcome to the forums Bird.  Chris will be along soon to sort you out and move this topic to the DCC forum where it would be better posted.

 

However, if you only have a Select controller, you will need to use relays as the Select cannot adjust the 8247 to continuous output for signals. Elite or RM can do it very simply.

[Chrissaf]

Bird50, welcome to the forum. I am sorry to read that one of my previous posts, made some considerable time ago and now out of date, has caused you a problem.

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The original R406 Hornby Signals have incandescent bulbs. Being bulbs, testing them with a 9 volt battery is perfectly safe. However, there seem to be a few of these R406 signals floating around that have been modified with LEDs. There is no current evidence that these LED modifications have ever been done by Hornby themselves. Most likely, third party modifications have been performed as replacement R406 incandescent bulbs are very hard to find. Peter's Spares sell them, but even they state that their bulbs are not genuine Hornby replacement bulbs - see images below.

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Images taken from the Peter's Spares web site.

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The thing with LEDs, is that unless a current limiting resistor is in series with the LED, then a 9 volt battery directly connected to an LED without the resistor will damage it. It would be desirable that whoever has modified these R406's to replace the bulbs with LEDs has included the resistor within the R406 housing, but this can not be assumed (albeit the evidence in your post infers that a protection resistor is in series with the Green wire).

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Therefore, if testing R406s suspected of or known to be modified with LEDs then I would use an external resistor (1,000 ohms) in one of the supply wires to be on the safe side. With the 1,000 ohm resistor as LED protection (preventing them from being damaged) in the supply circuit then you can then safely apply the 9 volt battery voltage across the various wiring combinations to see what is what i.e. what wiring combinations light up and what combinations don't.

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One thing that will prove whether the R406 is fitted with bulbs or LEDs without taking the signal apart. LEDs will only light up when the voltage polarity is the right way round, whereas bulbs will light up with the voltage polarity either way round. But clearly, your R406s would appear to be LED modified ones.

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If whoever has modified the R406 to fit LEDs has done it correctly, then the Green wire should connect to the common positive (C terminal on the R8247) and the Black & Red wires should go to switched negative polarity (+ & - on the R8247). A 1,000 ohm resistor should then go in series with the Green wire. This resistor may however already be fitted within the R406 housing - see later comments in this reply further below.

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The quote you have lifted from a previous post of mine (duplicated below) contains an error. The post as written is based on a belief that the Black wire was the common return and not the Green wire. Hornby use Black as the common return for their Black, Green & Red point wiring. It subsequently transpired that Hornby changed this accepted wiring convention for their R406 signals and used the Green for the common return instead of the Black (why they did this is unknown). This only came to light significantly later than when the original post was published. Ideally the original post that you have quoted from should be deleted, if you can provide a link to it, as a Community Moderator I can now do that.

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"Test your signals first before connecting them up with a PP3 (UK) 9 volt battery. If testing the R406, the battery can go either way round between the Black & Green wires for the Green Lamp and the Black & Red wires for the Red Lamp"

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.....when I had Green on the + terminal and then put black to - and then swapped to red to - all lights worked......

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This would indicate that whoever did this mod included a resistor in series with the Green wire, but it is only an indication. Test with an additional protection resistor in the voltage supply to be safe. If you are intending to take the R406 apart to replace one or other of the LEDs then look for the resistor at the same time. I believe the modified R406s used standard 5mm round Green and Red LEDs. This statement also shows that the Green is indeed the common return and not Black as discussed further above.

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Putting the 9v battery across the Black and Red wires would have excluded any resistor that might be included in the Green wire from the circuit, thus the LED resistor protection that might be present in the Green wire would have been circumnavigated.

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Note: to aid diagnostics and LED replacement. The long leg of a brand new unfitted round LED is the one that connects to the positive supply voltage (Green wire). The negative side of a round LED that has been soldered to a circuit board has a flat side in the bottom rim (edge) of the LED. Thus a visual inspection of a standard LED can be used to determine polarity orientation.

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Finally....posting images and photos.

In answer to your question about posting images. This forum software does not support pasting an image directly into a reply. To post an image, it first needs to be an image file (preferably a .JPG or .JPEG). You then use the 'image upload' icon in the reply text box. This is the black and white 'hill & moon' icon that sits between the tree and smiley face icons. Click that icon and follow on screen prompts. Note newbie poster images need to be checked by Admin before they are posted. Image approval only occurs during normal UK office weekday office hours. So there may be some delay before the image / photo will appear.

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EDIT: Just seen Fishy's previous reply. He is correct. If you have a Hornby Select controller. You will not be able to re-configure the R8247 for continuous output. There is a previous post on this topic (recent this time, less than a fortnight old). You can view it here.

[Chrissaf]

 

 

 

Hi All

First time on forum, i have been looking at past posts for the Wiring of the R406 signal lights and to be honest they got a bit confusing as some replys was they dont have LED's. well i have purchased a set and they defently have LED's and NOT screw bulbs.

So can a direct answer be given for this please as i ant no electrician but do understand quiet abit, i have blown them as even using a 9v battery, all was well when i had Green on the + termainal and then put black to - and then swopped to red to - all lights worked, but on a post that was up from Jan 16, "Test your signals first before connecting them up with a PP3 (UK) 9 volt battery. If testing the R406, the battery can go either way round between the Black & Green wires for the Green Lamp and the Black & Red wires for the Red Lamp" this was from Chrissaf. However do not put the Red & Black across the + & - as this blows 'the what i know now as LED's'. so what is the correct wiring for these to the R8247 and do these require a resistor of 1k and if so what wire is this to go on.

I dont want to go and by another one so i am going to search for the Led's and see if i can repair.

 

I have some pictures which i will post seperatly as cant seam to add at the bottom of this, can anyone assist me in getting the correct setup.

[Bird50]

 Fish and chris

Thanks for your reply its usfully to know that there is a third party changing the OM's design and not communicating it out, Fish i am running on elite and have change the CV's for this so i am cool with that.

 

Chris i have had to remove the LED board from the housing to get to the LED's, and i have removed the Red and Black from the mast and there is no resistor in the unit what so ever. it was very hard to get the cables out the mast as i had to remove as when taking the LED board out the Black and red broke away as it was all very tight.

This has caused the part of the copper strip on the board to seperate ( hopfully it can be put back) giving that a go in morning, however have you got any idea where i can just get the board from incase i can not repair it?

I have a few 1k resistors so once i get it going i will ensure that there is one in the Green wire for sure.

The pictures were uploaded but they have gone for vetting so they may turn up at some point, would be good to see what you think of the change.

 

The date that you posted the comment i mentioned was either 16th Jan or 26th Jan 2016, i would have to search it again to send link as i closed it down.

i wait your response to the question s i have asked and thank for your reply on the wiring much clearer

 

les

[Chrissaf]

Armed with that date. I can probably find it again. There are some post searching techniques I can use that are not obvious to most forum members.

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Just hypothetically. If Hornby had done the modification, then on the basis that an external resistor is needed (as far as your dismantling has shown, it is not integrated internally) then I can't in all honesty see that Hornby would not include an updated R406 instruction sheet that mentioned it. Not only that, but if a resistor is needed (which it is) then Hornby would have without a doubt included one with the R406 product.

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As to your question about replacement LED board. As a non Hornby mod, then without knowing who did indeed perform the mod it is near impossible to answer your question. At the end of the day, it is just two LEDs and three wires. It might be possible to use a small off-cut piece of copper strip board. I will post a picture of a strip-board sample just in case you are not familiar with what it looks like.

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I have also posted a drawing of how it should be wired.

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EDIT: Using the dates you gave me I tracked down that old post to 25th Jan 2016. I've now hidden it, plus some others around it in the same thread in order to make the replies make sense as a result of my one being missing. At least it now won't trip anybody else up now its gone. Sorry that it caused you a problem.

[Chrissaf]

PS - Closer inspection of the printed circuit board of your R406 may reveal a SMD (Surface Mounted Device) resistor. SMD resistors are tiny but obvious, if you know what you are looking for. Here is an example image of some SMD resistors.

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[Bird50]

Thanks chris for the info above.

On closer inspection i have found the smd ristors on the board (2x102) i have searched for these and they are a

SMD SMT 0805 Chip Resistors Surface Mount 1K 1Kohm 1 K 102 +/-5% 1/8W RoHs

so if it isnt the LED blown it may be SMD. hope this also assists others at the same time

Thanks for your assistance

 

Les.

[Chrissaf]

Bird50

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Looking at your photographs I would say that they show that Hornby have indeed changed the product design and replaced bulbs with LEDs in the current R406 version. This is the first time any tangible evidence has been seen on the forum for this design change. The change of product design is not documented on any product description that I have seen. The evidence for this now being the new official Hornby design is:

 

• That printed circuit board (close up replicated in image below) is a manufactured board and not some 'heath robinson' after market modification lash up. I can see that there are some SMD resistors mounted on that board (circled in Green). This would make the product compatible with the wiring diagram as included in the packaging that has not been updated to reflect the product design change. In other words, there is no need to add an external resistor with the revised design product, the resistor is integral to the design. Of course, looking at the circuit board damage, you will need to add an external resistor for this one particular signal if it is repaired with strip-board. I can also see two SMD rectification diodes (circled in Red) to make the signal compatible with the 16 volts AC support stated in the instructions. Replacement of the rectification diodes would not be needed when used with an R8247 as the output of that is DC.
• It was supplied in an official Hornby 'blister pack' therefore it should be same as it left the factory (no access to it from a third party modifier without damaging the packaging).
• It was purchased brand new from a reputable Hornby dealer.

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What does concern me though, is that you were able to damage it by applying a modest 9 volts across the Black & Red wires. If the product was susceptible to damage this way. Then Hornby should have updated the Instructions with a caveat about being careful with wiring. It think it very unlikely that the SMD resistors will be damaged, they are far more robust than a LED. LEDs are relatively fragile semi-conductors by comparison.

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It may be possible to repair the broken track with some very thin solid wire and a fine tipped soldering iron as part of the LED replacement activity.

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Looking at what components are placed on the circuit board. Then the schematic below is my (logical) deduction of how they are connected on the board. The (black) diodes provide the current path for when an AC supply is in the negative half cycle. They prevent the LED reverse bias voltage limits from being exceeded. If this deduced circuit is correct, then putting the 9v battery across the Red & Black wires should not have caused any damage, as the current is passing through both resistors and not none of them (if there had been a single resistor in the Green wire circuit for instance).

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