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Wiring the LEDs in a DC wired loco for DCC

dennisedgar7
 

I have a DC loco that has 4 LEDs front and rear. There are two white LEDs and two red LEDs at each end.

When running forward in DC mode the two white LEDS light up and two red LEDs in the rear light up and vice versa.
I would like to install a decoder into the loco but I am not sure how to wire the LEDs so that I get the same functionality.

The LED terminals are not all visible. I fact there are only 4 leads coming from each bank of LEDs.

I am not sure how to up load a diagram to show the existing wiring layout.
Is anyone able to assist me?

Paul O
 

 Dennis, you’ll have to give us a lot more information in order for us to help.
Is there any circuitboard involved in the wiring? Do the red LEDs only come on in reverse?
If you can, draw out the wiring on the sheet of paper, create a JPEG or some other form and upload it to the Files or photo section depending on what format you upload.

Paul O

dennisedgar7
 

Paul,

 

Thanks for the email.

 

I have uploaded a sketch of the wiring.

 

There is no circuit board involved in the wiring.

 

The red LEDs in the rear (long hood) come on when the loco is moving forward and the white LEDs in the rear (long hood) are off and the white LEDs in the front are on.

When the loco is reversing then the red LEDs in the front (short hood) are on and the white LEDs off.

 

Dennis G

 

From: w4dccqa@groups.io [mailto:w4dccqa@groups.io] On Behalf Of Paul O
Sent: 02 May 2019 02:54 AM
To: w4dccqa@groups.io
Subject: Re: [w4dccqa] Wiring the LEDs in a DC wired loco for DCC

 

 Dennis, you’ll have to give us a lot more information in order for us to help.

Is there any circuitboard involved in the wiring? Do the red LEDs only come on in reverse?
If you can, draw out the wiring on the sheet of paper, create a JPEG or some other form and upload it to the Files or photo section depending on what format you upload.

Paul O

Al Silverstein
 

Dennis,
 
You did not specify the type or scale of the engine so my comments are theoretical. Should the decoder be a basic hard wired type powering lamps then the following in theory, depending upon if you want to turn the forward and rear headlights on/off, and depending upon the decoder used, this should work for your situation. You will most likely need to add on the negative leg of each LED a resistor to adjust for brightness. 1/8 amp resistors will most likely get the job done.
 
Connect all eight of the LEDs positive lead to the blue wire of the decoder.
 
Connect the front white LEDs and the rear red LEDs to the white wire of the decoder.
 
Connect the front red LEDs and the rear white LEDs to the yellow wire of the decoder.
 
In essence when the engine is set to move forward, and the headlight function is turned on, the front white LEDs will light up and the rear red LEDs will light up. When the engine is set to move backwards, and the headlight function is turned on, the rear white LEDs will light up and the front red LEDS will light up.
 
I did something similar to a N scale doodlebug a couple of years ago.
 
You might want to test the above first to insure of the value of the resistors before you wire the headlights of your engine. It will be easier to swap out different value resistors in order to get the proper brightness of the LED.
 
Al Silverstein
 
 
 
 

From: dennisedgar7
Sent: Wednesday, May 1, 2019 1:17 PM
To: w4dccqa@groups.io
Subject: [w4dccqa] Wiring the LEDs in a DC wired loco for DCC
 
I have a DC loco that has 4 LEDs front and rear. There are two white LEDs and two red LEDs at each end.

When running forward in DC mode the two white LEDS light up and two red LEDs in the rear light up and vice versa.
I would like to install a decoder into the loco but I am not sure how to wire the LEDs so that I get the same functionality.

The LED terminals are not all visible. I fact there are only 4 leads coming from each bank of LEDs.

I am not sure how to up load a diagram to show the existing wiring layout.
Is anyone able to assist me?
 

Don Vollrath
 

Dennis,
The photo/sketch is not complete and probably not correct.
1. For DC operation... With the + polarity as marked for Forward movement It appears as though the 2 White LEDs at the Front are connected in series (starting with the anode) and also in series with the 2 Red LEDs in the rear, and there is a resistor R1 to limit the current. [Current flow from + to - ] But with the polarity reversed the 2 White LEDs in the rear (again starting with the anode) are also in series and connected to the 2 Red LEDs in the front, but there is no current limiting resistor. That's not going to work. There must be a mistake in your diagram.
It would work with the existing R1 if the rear white LED connection to the (- marked) terminal was connected to the R1 & Red LED at the (-) marked terminal in your sketch, This would place R1 in series with either polarity.

2. But with a DCC the polarity doesn't reverse. It will just turn one 'side' on or off. So the connected polsarity of the LEDs needs to be corrected/adjusted.
To use only one resistor it needs to be connected to the (+) or common (blue wire) of the decoder... [not a negative lead as shown]. Then disconnect the wire from the rear White LEDs to the (-) marked terminal and connect it to the resistor/Read Red LED side of that connection. [This should be the anode end of the white LEDs]. And disconnect the Red/+ wire of the Front LED string and connect it directly to the REAR light control of the decoder (prob. Yellow).

3. Then reverse the (external) connections to the Rear Red LEDs, and those of the Front White LEDs from that shown in your diagram to your square marked terminals. Then connect the (+) marked wire in your diagram now going only to the cathode side of the Front White LEDs to the FWD decoder lighting output (prob white wire).
Test make sure that it all works with the FWD and REV lighting outputs separately engaged. [If they are both on at the same time it may be too dim due to using the same current limiting resistor.] You may fine that they are too bright. If so, increase the Ohms value of the resistor.

For independent intensity control of Red and White lights it will take some re-wiring and separate additional resistors [but not impossible.]

DonV 

. OK, so far so good  

dennisedgar7
 

Hi Al,

Thank you for your reply.
The builder of the loco body had epoxied the LEDs in place and so I had to remove the epoxy. I used a battery powered soldering iron to do so.
Having exposed the LEDs I discovered that he had wired them in series.
Following your advice, I will be re-installing the LEDs and wiring them anode to anode etc.
Thanks again for your advice.
The loco is an HO model.

Dennis G

On Thu, 02 May 2019 at 13:34, Al Silverstein <alsilverstein@...> wrote:
Dennis,
 
You did not specify the type or scale of the engine so my comments are theoretical. Should the decoder be a basic hard wired type powering lamps then the following in theory, depending upon if you want to turn the forward and rear headlights on/off, and depending upon the decoder used, this should work for your situation. You will most likely need to add on the negative leg of each LED a resistor to adjust for brightness. 1/8 amp resistors will most likely get the job done.
 
Connect all eight of the LEDs positive lead to the blue wire of the decoder.
 
Connect the front white LEDs and the rear red LEDs to the white wire of the decoder.
 
Connect the front red LEDs and the rear white LEDs to the yellow wire of the decoder.
 
In essence when the engine is set to move forward, and the headlight function is turned on, the front white LEDs will light up and the rear red LEDs will light up. When the engine is set to move backwards, and the headlight function is turned on, the rear white LEDs will light up and the front red LEDS will light up.
 
I did something similar to a N scale doodlebug a couple of years ago.
 
You might want to test the above first to insure of the value of the resistors before you wire the headlights of your engine. It will be easier to swap out different value resistors in order to get the proper brightness of the LED.
 
Al Silverstein
 
 
 
 
From: dennisedgar7
Sent: Wednesday, May 1, 2019 1:17 PM
To: w4dccqa@groups.io
Subject: [w4dccqa] Wiring the LEDs in a DC wired loco for DCC
 
I have a DC loco that has 4 LEDs front and rear. There are two white LEDs and two red LEDs at each end.

When running forward in DC mode the two white LEDS light up and two red LEDs in the rear light up and vice versa.
I would like to install a decoder into the loco but I am not sure how to wire the LEDs so that I get the same functionality.

The LED terminals are not all visible. I fact there are only 4 leads coming from each bank of LEDs.

I am not sure how to up load a diagram to show the existing wiring layout.
Is anyone able to assist me?
 

--
Dennis G Edgar
Lead Auditor  133839
mobile: 083 6470569