Jump to content
 

Directional Lighting on DCC Without Using a Decoder


Recommended Posts

As a thought experiment rather than anything serious, I'm designing a circuit that could be plugged into a 6-pin decoder socket and enable dummy loco directional lighting on a DCC layout without using a decoder. It'll probably never reach fruition as the cost of the components may well exceed the price of a cheap and nasty decoder.

I'm thinking a socket to wired decoder adaptor, a rectifier chip, two latching reed switches and (omitted from diagram) a capacitor, resistor and optional protection diode for anti-flicker. The reed switches would be attached to pins 5 (forwards lighting) and 6 (reverse) and would have to be mounted far enough apart that a magnet could operate one without affecting the other. An optional development would be a lighting bar connection.

I've assumed that on a Class 153 (as an example) when 'forwards' is selected, pin 5 (white, but light grey in the circuit diagram) goes live and is connected to one set of white LEDs and the corresponding red LEDs at the other end of the loco. Likewise pin 6 (dirty yellow for clarity) is connected to the alternate LEDs at each end. Given the LEDs are hard-wired to the track when in DC mode, I assume their directionality comes from each pair (one front set, one back set) being connected with opposite polarity to the other.

There are things to establish before a working circuit could be built, much of which I could no doubt get from DCC reference material, e.g. whether the decoder has resistors on pins 5 and 6 and if so, what their values are, or whether the loco has current limiting resistors built into it.

 

I'm surprised nothing of the sort has been manufactured already but maybe my googling skills just haven't found it yet.

 

DCC-Directional Lighting.jpg

Edited by alphonsus
Link to post
Share on other sites

2 minutes ago, WIMorrison said:

I find that the decoder in the loco does an excellent job of switching the directional lights and cant see why another circuit is required.

I was thinking more for the dummy cars in a multi-car set (e.g. a Class 156) as a true decoder is only needed in the motorised car.

Link to post
Share on other sites

  • RMweb Premium

Unless you can decode the DCC messages and recognise the address of the loco or consist there is no indication as to what direction the vehicle is moving unless you actually sense the wheel movements. At a gross level the DCC signal will always look the same.

 

Cheers

Dave

 

  • Like 2
Link to post
Share on other sites

2 hours ago, Nigelcliffe said:

I've built a DCC function decoder for about £2 (from a published public DIY design) which can do lights "properly" from the DCC instructions. I'm not sure what the problem is that's being chased here.

 

 

As per first line of OP: "a thought experiment [to] enable dummy loco directional lighting on a DCC layout without using a decoder". I'd appreciate a link to the design you mention as finding it in your 4k+ posts might take a while.

Best wishes,

Alph

Link to post
Share on other sites

6 hours ago, alphonsus said:

As per first line of OP: "a thought experiment [to] enable dummy loco directional lighting on a DCC layout without using a decoder". I'd appreciate a link to the design you mention as finding it in your 4k+ posts might take a while.

Best wishes,

Alph

 

http://dccdiy.org.uk/function.html

 

The site's homepage seems faulty at present.   The "downloads" for the function decoder includes the Hex files to load into a PIC processor.  

  • Like 1
Link to post
Share on other sites

  • RMweb Premium
20 minutes ago, WIMorrison said:

I would just buy this - only £10 and no hassle :)

 

LaisDcc Decoder Chip 7 Wire 4Fn No Motor

I agree Iain, but the OP looks like he wants to re-invent the wheel.:D

I keep my discarded loco decoders (Hornby etc.) to use for lighting.

 

Both Nigel's and Rudy's offerings would give you a cheaper decoder but with the hassle of more DIY.

 

  • Like 1
Link to post
Share on other sites

14 hours ago, melmerby said:

I agree Iain, but the OP looks like he wants to re-invent the wheel.:D

I keep my discarded loco decoders (Hornby etc.) to use for lighting.

 

Both Nigel's and Rudy's offerings would give you a cheaper decoder but with the hassle of more DIY.

 

Wheel-reinventing is my forte :D

In my defence, daytime TV isn't fantastic and the dog's not a great conversationalist so I need something to occupy my mind, and thought experiments are cheaper than devising new timetables that require new locos...

I'm liking the £10 decoder price point, far more justifiable for lighting a rake of coaches than something twice the price, but I also like the idea of using an Arduino for the job as I've played with them in the past. I suspect I'll go down the decoder route since the amount of space available inside an n-gauge coach ain't high and shoehorning in an Arduino, rectifier, plus a stay-alive circuit with capacitor large enough for the Arduino as well isn't likely. DCC control of model domestic and street lighting using an Arduino with a permanent power connection is another matter though...

Thanks all for your thoughts!

Link to post
Share on other sites

1 hour ago, melmerby said:

You could look at this for inspiration:

https://learn.sparkfun.com/tutorials/tiny-avr-programmer-hookup-guide/all

 

Certainly do-able in an N scale vehicle

(the AT tiny is a microprocessor from a similar family as the ones found in most Arduinos)

That looks most impressive for such a tiny package. Worth investing in. Shall have to see if there's a UK supplier before mucking around with importing one. Thanks for the pointer

Link to post
Share on other sites

  • RMweb Premium
4 minutes ago, alphonsus said:

That looks most impressive for such a tiny package. Worth investing in. Shall have to see if there's a UK supplier before mucking around with importing one. Thanks for the pointer

You can program it with an normal Arduino:

https://create.arduino.cc/projecthub/arjun/programming-attiny85-with-arduino-uno-afb829

 

Look on e-bay for thechip itself

https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2380057.m570.l2632&_nkw=attiny85&_sacat=92074

  • Like 1
Link to post
Share on other sites

  • 4 weeks later...

I have seen YT of a guy in USA who used an ATTiny to take a single output from a decoder to create a rotary beacon.

 

Depending upon era a coach might need interior lights, central door locking lights and a driving trailer control of the head/tail lights.

 

Like many I have a few spare decoders as a few sound chips have been fitted.

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...