LED Wiring

[WIMorrison]

I have some bi-colour LEDs that I want to use for directional lighting in some old locos which are using MX617N decoders. 

 

I think that I can use the white and yellow outputs of the decoder to the cathode (white at one end and red at the other) with the return through the black wire for half wave lighting, but that suggests to me that the red and white would both be on at the same time at each end because the polarity of the output from the decoder is constant - clearly this is not acceptable

 

What I really want to do is have the white and red on (directional) when the loco is running free (and like this always in a single carriage railcar) but I want to be able to switch off the red tail llght when the loco is in a train.

 

I have fried my brain tonight trying to work it out and and happy to admit defeat - here hoping that someone here has the circuit to hand and can post it here for me

 

Thanks

[pauliebanger]

 

Are the bi-colour LEDs common cathode or common anode?

 

Best regards,

 

Paul

[WIMorrison]

Paul

 

The are Common Anode

 

Iain

[pauliebanger]

Then I think this should work.

 

If you are able to control each colour individually, common anode,  what you desire is normally achieved using 4 function outputs. White and Yellow wires provide 2, use FO1 and FO2 from the decoder for the others.

 

Blue wire is positive - connect to common anode. Yellow wire and white wires are open collector so connect one to each of the cathodes.

 

This will give full wave power.

 

There are a couple of ways to do this,

 

This is what I would recommend.

 

Use yellow and white at one end for red LED and White/yellow LED respectively. As the F key 0 is directional by default, the lamps will show only white or only red depending upon direction.

 

At the other end, use FO1 and FO2 for red and white LEDS. Use ZIMO Swiss Mapping to allocate a single F key as operator for lights at this end, and for FO1 (red) to only illuminate in the forward direction and FO2  (the whites) to illuminate in only the rearward direction.

 

With both F key 0 and the F key assigned by Swiss Mapping engaged, white LEDs will show at on end, red at the other and colours will reverse when direction is reversed.

 

With only F key 0, whites will illuminate at one end, and change to red with direction change. There will be no lights illuminated at the other end whatever the direction.

 

With only the assigned F key, the light at the other end will illuminate directionally, either red or white.

 

This you can easily select 'no illumlnation' at whichever end is connected to the train, and the other end will show correct colours whether drawing or propelling.

 

Paul

[John ks]

13 hours ago, WIMorrison said:

I have some bi-colour LEDs that I want to use for directional lighting in some old locos which are using MX617N decoders. 

 

I think that I can use the white and yellow outputs of the decoder to the cathode (white at one end and red at the other) with the return through the black wire for half wave lighting, but that suggests to me that the red and white would both be on at the same time at each end because the polarity of the output from the decoder is constant - clearly this is not acceptable

 

What I really want to do is have the white and red on (directional) when the loco is running free (and like this always in a single carriage railcar) but I want to be able to switch off the red tail llght when the loco is in a train.

 

I have fried my brain tonight trying to work it out and and happy to admit defeat - here hoping that someone here has the circuit to hand and can post it here for me

 

Thanks

My understanding is that the MX617N is a 6 wire, 2 function decoder & as such I don't think it is possible to do what you want

EDIT after seeing Pauls next post & doing a more thorough look I see that the 617 has more functions than I first saw

Follow Paul's next & previous posts 

 

Edit no longer relevant With a switch between the black wire & the common anode you could switch off either bicolour LED

 

Edit The following should help explain how half wave rectification works with 6 pin decoders 

The diagram is a representation of a 6 wire 2 function decoder showing only the relevant parts to help understand how the functions are switched

 

When the black wire is positive the current flows from it through the LED, then through the sw in the micro (if closed) to negative, through D4 to the red wire which will be negative

When the black wire is negative the anode is negative & the cathode is negative (its connected to the negative of the bridge rectifier through the micro if closed)

With anode & cathode both negative no current will flow

 

 

Don't forget resistors for the LEDs

 

Hope this helps 

John

 

 

 

 

 

 

 

Edited January 19, 2020 by John ks
mistake

[pauliebanger]

 

The ZIMO MX617 is a 6 Function Output decoder.

 

FO 0 (front light)

FO 0 (rear light)

FO 1

FO 2

FO3

and FO 4

 

Sometimes described as two lighting and 4 Aux.

 

All are common collector (a.k.a. full power or 'normal') and provide the switched return from the common positive.

 

In fact it has enough FOs to add a pair of cab lights as well.

 

 

 

Edited January 19, 2020 by pauliebanger