Is it OK to link decoder outputs?

[DavidBird]

Will there be any harmful effects of linking the 2 decoder outputs so that the headlights (and taillights) are ON at both ends? I'm using the Hornby R8249 at the moment.

[Mr.S.corn78]

Will there be any harmful effects of linking the 2 decoder outputs so that the headlights (and taillights) are ON at both ends? I'm using the Hornby R8249 at the moment.

Hi,

 

I would advise against it just to be on the safe side.

 

You can possible change one of the function outputs to respond to the one f key.

 

Tho I'm not sure if it's possible with the Hornby chip.

 

Can I ask why you want all the lights on??

 

Cheers

simon

[loickebros]

Will there be any harmful effects of linking the 2 decoder outputs so that the headlights (and taillights) are ON at both ends? I'm using the Hornby R8249 at the moment.

 

Yes you can link the light outputs i have done this ok to power smoke units on steam locos so that it works i both directions.

Reagrds

 

DAVE

[Donw]

It might be possible using diodes to prevent back currents. However you need the decoder spec first to check what the outputs are this might also indicate that there is an output that can be configured to do what you want.

Donw

[DavidBird]

Hi,

 

I would advise against it just to be on the safe side.

 

You can possible change one of the function outputs to respond to the one f key.

 

Tho I'm not sure if it's possible with the Hornby chip.

 

Can I ask why you want all the lights on??

 

Cheers

simon

Thanks Simon

I want the lights to come on and off with the f0 function, as normal, but separate the changing ends part of the light's operation.

I am also installing a DPDT relay between the decoder and the motor controlled by a spare function output (f2 - purple flylead - on the Hornby 8249) to provide a "change ends" effect. I want this to cause the lights to change ends as well.

The result is when the loco reverses the white lights are at the rear, when the loco changes ends the white lights swap to the other end.

I watched a 67 shunting oil tanks at Fort William yesterday, the white lights were definately at the rear of the train!

[RedgateModels]

In it's first incarnation (before DCC sound) my DJH class 2 tank was controlled by a Hornby R8215 decoder (yes I know!) The glowing firebox was lit with the yellow and white wires soldered together so that it glowed in both directions.

 

I asked the same question at the time and the consensus seemed to be that it's okay to common up the outputs.

[DavidBird]

OK, so it seems to be safe to link white and yellow directly, as the Hornby decoder is fairly cheap its not too bad if it does go wrong!

 

Now I just need to come up with the circuit to make the purple wire control the lights changing ends.

Anybody got any ideas?

 

Many thanks to all who replied.

[298]

OK, so it seems to be safe to link white and yellow directly, as the Hornby decoder is fairly cheap its not too bad if it does go wrong!

 

Now I just need to come up with the circuit to make the purple wire control the lights changing ends.

Anybody got any ideas?

 

Many thanks to all who replied.

 

The last time I looked at a real loco, all of the lights were independantly controlled (although the 87's initially had their headlights linked to the direction switch so the main headlight came on if the front markers were). The simple answer is to use a four, six or eight function decoder and control all of the lights as required, depending on what the driver needs lit.

[Crosland]

Yes you can link the light outputs i have done this ok to power smoke units on steam locos so that it works i both directions.

Reagrds

 

DAVE

Decoders use open collector transistor at the output, so it's quite safe to tie them together to increase the current.

 

Andrew Crosland

[buffalo]

...

The result is when the loco reverses the white lights are at the rear, when the loco changes ends the white lights swap to the other end.

I watched a 67 shunting oil tanks at Fort William yesterday, the white lights were definately at the rear of the train!

 

Having established that it is normally ok to link decoder outputs, I wonder if it's worth asking a question in the Prototype Questions section about actual prototype practice before you go any further? The reason I mention this is that it is always possible that what you saw at Fort William may not have been normal practice at all. On the other hand, are you certain that the white lights were only illuminated at the rear? Could they have been on at both ends of the loco? I've been trying to get to the bottom of a similar question about Austrian and German practice over on the Overseas Prototype forum and others have been able to help with examples of shunting where the white lights are on at the rear. The question originated because of the behaviour of an RTR DCC model on which the lights at both ends came on together.

 

Nick

[96701]

The older multiple units and locos certainly did have separate switches for marker and tail lights. Having seen HSTs reverse at Gloucester, it looks to me as though marker, tail and head lights are all connected to independent switches.

[DavidBird]

The last time I looked at a real loco, all of the lights were independantly controlled ... The simple answer is to use a four, six or eight function decoder and control all of the lights as required, depending on what the driver needs lit.

 

Yes, that's the simple answer, but I'd like to retain the lights on/off with F0, and combine the "lights change ends" with the "driver change ends" relay-operated function.

 

...it is always possible that what you saw at Fort William may not have been normal practice at all. On the other hand, are you certain that the white lights were only illuminated at the rear? Could they have been on at both ends of the loco? ...

 

Nick

The white lights could well have been on both ends of the loco! I also noticed that there was not a red tail-light on the other end of the train...

[Sunnysa]

Yes, that's the simple answer, but I'd like to retain the lights on/off with F0, and combine the "lights change ends" with the "driver change ends" relay-operated function.

 

 

The white lights could well have been on both ends of the loco! I also noticed that there was not a red tail-light on the other end of the train...

 

If you want head lights and red tail lights on together and have them swap ends why not link the white wire forward head lights and opossite red tail lights together. Then link the yellow reverse head light and opposite end tail light together.

The lights will then change with direction of loco without the need to link function wires and the use of relays/switches etc., in loco.

Just press 0 function and away you go.

This will also leave any other function wires for other uses if required.

BTW, connecting two function wires together does no harm. I do this (white/yellow) if I want a single ended diesel loco front and rear head light to stay on irrispective of direction.

 

Cheers

 

Ian