New DCC circuit for Independent Lights - will it work!?

[LMSFan72]

Hi, I have done a few mods now to my locos to get all with independent lights, a few of which you will have seen on here. My latest project is a Bachmann Class 37 rather than a Hornby, but it is all running on Railmaster and Elite so I hope people don't mind me posting here. The advice from Chrisaf and others on this forum has been so useful I thought I'd ask here again.

 

This time I am trying to use the existing circuitry with very few modifications other than adding in additional wiring rather than removing and replacing components. The light boards at each end are common positive and each led has it's own resistor and capacitance circuit on board, I assume to have some limited stay-alive.

 

The loco comes with two switches underneath. One turns cab lights on and off and the other switches the tail light operation on and off (so that they work in conjunction with the marker lights if on and not at all if the switch is off). Additionally the circuiut is designed to allow lighting to work on DC as well and therefore has additional components that do not get used in DCC configuration.

 

I have traced the complete circuit and drawn that up along with the modificaitons I plan. I think it will work but I have a couple of questions that I would hope someone may be able to help with.

 

Refering to the nomenclature in the diagram, and the notes on it, my questions are these:

 

1. Referring to the cab lights on the rhs of the circuit. Originally AUX1 controlled both lights together. The switch turned the DCC control on or off originally (and on or off on DC). I don't plan to remove the cab light switch, so it will be left in the open state. The result of removing the black dashed wire and connecting a new green wire to PAD5 to control CAB1 is that the C11 capacitor doesn't do anything other than remain charged (I think). I have added a new connection to AUX2 that then switches the other side of the switch (PAD6) that now control CAB2. So, the question is is there any concern on not having C11 in the CAB1 circuit? If I need a capcitor in the circuit, how would I calculate the value required?

 

2. Is there any damage that might be done if the cab light switch between PAD5 and PAD6 is closed?

 

3. I have used a similar idea to control the tail lights by wiring them to AUX4 and AUX6. Basically, witht he switch open I have been able to put new switched negative supplies to each of the tail lamps as the open switch isolates the circuits. The question this time is, if the switch was accidently closed, would any damage be done. My belief is that it would just mean that I have 2 functions that would then control the "normal" directional lighting front and rear.

 

4. I am looking to be able to turn the headlights off. I can easily add a new tail wire to the lightboard in between each headlight and it's series resistor. This idea is that turning this negative would "starve" the headlights. I have put a diode in each circuit with the tail switched by AUX5. Would this work?

 

Many thanks for any help!

 

 

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[96RAF]

My only comment is about the cab light switch.

As I see it with the switch open then purple or green will light their own cab lights only, but with the switch closed the green will light both lights, whereas the purple will only light its own.

 

Rob

[LMSFan72]

Thanks Rob. I will certainly test for that - as I don't intend to run switch closed i'm ok if that is what it does.

[96RAF]

There should be no problem running with the switch closed as it is common practice to gang function outputs to load share current such as for a marginal smoke unit, etc, providing there is no cross feed back into your circuitry.

 

The only time that could occur is if the two cab leds have different ratings in which case the hungry one would take charge, but I would expect both cab lights and associated components to be balanced anyhow.

Rob