Express Models LED Lighting - Bachmann Class 37

[bluesparky]

 Hi all

 

 I purchased a DCC Head / Tail Light Unit for a Bachmann class 37 / 0 Centre Head code (32-777).

 

 I thought I had wired up everything correctly but it turns out when I applied power to the track, rear pair of the headcode lights blew up, the front headlights stay on and I’ve only got DCC control of the rear tail lights.

 

 After attaching the led boards to the headcode part of the loco I then assumed that all white cables connect together (as per my photos) and the same for the blue, orange and green etc.

 

 Have I made a mistake in this assumption and therefore explaining my problems, or is the a physical wiring error that I’ve potentially made and is shorting something out?

 

 I’m using a eHattons 8 pin, 4 function decoder for the locomotive.

 

 I have purchased several lighting kits from Express Models and I know they have a great reputation and products, this is the first one that I’ve installed, so I'm keen to be sure that I don’t make any more mistakes with the others.

 

 If anyone has any thoughts or suggestions where I may have gone wrong, then I'd really appreciate it, or if any other photos or a better description of what the lights are doing are needed to help see what I've done then I can easily do that.

 

 Thanks in advance, 

 Mark

 

[tractor_37260]

 

 Hi all

 

 I purchased a DCC Head / Tail Light Unit for a Bachmann class 37 / 0 Centre Head code (32-777).

 

 I thought I had wired up everything correctly but it turns out when I applied power to the track, rear pair of the headcode lights blew up, the front headlights stay on and I’ve only got DCC control of the rear tail lights.

 

 After attaching the led boards to the headcode part of the loco I then assumed that all white cables connect together (as per my photos) and the same for the blue, orange and green etc.

 

 Have I made a mistake in this assumption and therefore explaining my problems, or is the a physical wiring error that I’ve potentially made and is shorting something out?

 

 I’m using a eHattons 8 pin, 4 function decoder for the locomotive.

 

 I have purchased several lighting kits from Express Models and I know they have a great reputation and products, this is the first one that I’ve installed, so I'm keen to be sure that I don’t make any more mistakes with the others.

 

 If anyone has any thoughts or suggestions where I may have gone wrong, then I'd really appreciate it, or if any other photos or a better description of what the lights are doing are needed to help see what I've done then I can easily do that.

 

 Thanks in advance, 

 Mark

 

 

Normally Express models lighting kits come with fairly easy to follow fitting instructions.   The White wire (only) is connected to the White wire on the decoder, the same for the Yellow wire, depending on what other wire colours Express has used (normally Green and Purple) for the other two tail light circuits - these are connected to the Green & Purple wires on the decoder. NB: the Blue wire is the common positive and should ONLY be connected to the Blue wire on the decoder.

 

The first step if using a decoder with an 8 pin plug, is to cut the White/Yellow/Green and Blue wires ONLY off at the top of the 8pin plug and connect them to the same colour wires on the Express circuit board. The Purple wire is a separate wire (not attached to the 8pin plug) it's connected to the Purple ? wire on the Express circuit board.

You then have have to map (set) the function outputs via CV's to F keys to control the lights as required.

 

Normally the the White wire controls the marker lights at No1 fan end - the Yellow wire the opposite end, the Green and Purple wires controlling the tail lights.

 

However it appears you may have connecting some of the wires together in error and you may well have blown some of the LED's, and possibly the decoder function outputs also ? 

Edited June 28, 2017 by tractor_37260

[John ks]

I agree with what TRACTOR has said

 

From what I can make out with the way all the white wires have all been joined together you have effectively bypassed the resistor for the leds which puts 12Von the led & they shine very,very,very bright for a brief time (don’t ask me how I know)

This can also  destroy the output function of the decoder

If the decoder function outputs are damaged you may still be able to use it as a motor only decoder

 

 

I have never seen Express Models kits before but from Tractors descripyion and your photos I believe this is how the Express Models can be connected

 

 

 

 

With the way the drawing is shown  headlight at one end & taillight at the other end will be controled by the function 0 switch

If the red wire from the Express Models board go to the headcode lights the they will be controled by the F1 & F2 Buttons.

 

Tractor I have meant this to be a supplment to your post & If you can see any glearing mistakes in what I have done please correct me

 

John

[tractor_37260]

 

I agree with what TRACTOR has said

 

From what I can make out with the way all the white wires have all been joined together you have effectively bypassed the resistor for the leds which puts 12Von the led & they shine very,very,very bright for a brief time (don’t ask me how I know)

This can also  destroy the output function of the decoder

If the decoder function outputs are damaged you may still be able to use it as a motor only decoder

 

 

I have never seen Express Models kits before but from Tractors descripyion and your photos I believe this is how the Express Models can be connected

 

 decoder conect.jpg

 

 

With the way the drawing is shown  headlight at one end & taillight at the other end will be controled by the function 0 switch

If the red wire from the Express Models board go to the headcode lights the they will be controled by the F1 & F2 Buttons.

 

Tractor I have meant this to be a supplment to your post & If you can see any glearing mistakes in what I have done please correct me

 

John

 

 

John

 

Your circuit diagram should prove very useful for the OP - I've only just noticed that the Express boards have linked outputs of White/Yellow wires on each end, one of these being for presumably headlight LED's ? (hence the twin Blue wires each side), which if necessary could be controlled separately, this may well have confused the OP.  These circuits are dual fed via their own separate resistors, as normally White Headlight LED's would rob most of the available voltage if wired in common with the marker lights through a single resistor.

 

Ken

Edited June 28, 2017 by tractor_37260

[bluesparky]

Thank you for the quick response, it's appreciated.

 I'll have a close look at the diagram, 

 The kit came with white wires coming from both ends etc.

 I'll take note of all the above information and have a look at what I've done. I happen to have spare decoders and LEDS so I can hopefully replace and repair any damage.

 Once again, quick and valuable suggestions and advice.

 Thank you

[RAF96]

I found that I had to splice an additional 1K resistor into the blue wire to tame the total current draw by the directional lights - 1 x white headlight + 2 x yellow marker lights + 2 x red rear lights.

 

I asked Express Models for the spec of the leds and resistors they were using but never got a reply.

 

I have assumed 20mA per led and my decoder has a 100mA function limit without protection which meant it was operating flat out, so the extra resistor pulls the current draw down well within limits and the decoder works fine again.

 

I found their instructions to be very clear, even to the point of explaining the wiring differences for 4 to many more function decoders in order to get the lighting effect required.

[tractor_37260]

I found that I had to splice an additional 1K resistor into the blue wire to tame the total current draw by the directional lights - 1 x white headlight + 2 x yellow marker lights + 2 x red rear lights.

 

>> This I suspect would only be necessary if using an Hornby R8249  - which ideally should be avoided if at all possible.   Certainly NOT necessary with Hornby's R8245 Sapphire as each function output is rated at  200ma  -  total current limit of all 4 function outputs being 500ma.  I believe the TTS decoders are also basic R8249's with added sound components tacked on....................hence the budget price - like all things - you get what you pay for................

 

Most quality decoders have 100-150ma per function output.................... including the Hatton's one being used by the OP

 

 

I asked Express Models for the spec of the leds and resistors they were using but never got a reply.

 

>> Why the need to ask about the resistors - the SMD resistor values are already marked on their circuit boards.............. failing that, the resistor values could be checked with a meter..............

 

I have assumed 20mA per led and my decoder has a 100mA function limit without protection which meant it was operating flat out, so the extra resistor pulls the current draw down well within limits and the decoder works fine again.

 

>> Em..........R8249..........? ?

 

I found their instructions to be very clear, even to the point of explaining the wiring differences for 4 to many more function decoders in order to get the lighting effect required.

 

>> Yes I'd agree with the above, they also designed these DCC lighting circuits to work with most quality decoders, if extra resistors were required, they would have been added at the design stage .......................

Edited June 28, 2017 by tractor_37260

[bluesparky]

John

 

Your circuit diagram should prove very useful for the OP - I've only just noticed that the Express boards have linked outputs of White/Yellow wires on each end, one of these being for presumably headlight LED's ? (hence the twin Blue wires each side), which if necessary could be controlled separately, this may well have confused the OP.  These circuits are dual fed via their own separate resistors, as normally White Headlight LED's would rob most of the available voltage if wired in common with the marker lights through a single resistor.

 

Ken

Yes, I'm definitely confused. There appeared to be ONE e.g. white cable coming from board and two white cables going to either end of the loco, the instructions say "connect all wires to the corresponding decoder wires", so I cut the decoder white wire and connected both white wires to that. Obviously this would rob me of independent control.

 I did this for each colour.

 I'm still confused, there doesn't seem to be enough outputs from the Express Models circuit board.

 I've a couple of similar boards for a class 31 and 47 so I'll look at them too.

 Still confused, but I appreciate the replies and help, thank you 

[tractor_37260]

Yes, I'm definitely confused. There appeared to be ONE e.g. white cable coming from board and two white cables going to either end of the loco, the instructions say "connect all wires to the corresponding decoder wires", so I cut the decoder white wire and connected both white wires to that. Obviously this would rob me of independent control.

 I did this for each colour.

 I'm still confused, there doesn't seem to be enough outputs from the Express Models circuit board.

 I've a couple of similar boards for a class 31 and 47 so I'll look at them too.

 Still confused, but I appreciate the replies and help, thank you 

 

As supplied your Express lighting board has 5 loose wires coming from the center of it, White/Yellow/Blue /Green/Purple - connect these up as shown in "John's ks" wiring diagram above, to the same colour of wires on the decoder (after you have cut them off at the top of the 8 pin plug. (This is what is meant by "connect all wires to the corresponding decoder wires)  DO NOT connect anything to the wires coming from each end of the lighting board that go to the headlight LEDs and circuit boards that mount the the marker/tail light LED's. 

 

If you have cut the White decoder wire and connected both white wires directly to it, in doing so you have by-passed the resistors, the resulting full track voltage would have blown the LED's connected to the white wires instantly.

The same would apply to the other LED's if you connected these up in the same way.

Edited June 30, 2017 by tractor_37260

[John ks]

This image might give you another way of looking at the circuit.

 

 

 

 

 

John

 

 

[RAF96]

 

I found that I had to splice an additional 1K resistor into the blue wire to tame the total current draw by the directional lights - 1 x white headlight + 2 x yellow marker lights + 2 x red rear lights.

 

>> This I suspect would only be necessary if using an Hornby R8249  - which ideally should be avoided if at all possible.   Certainly NOT necessary with Hornby's R8245 Sapphire as each function output is rated at  200ma  -  total current limit of all 4 function outputs being 500ma.  I believe the TTS decoders are also basic R8249's with added sound components tacked on....................hence the budget price - like all things - you get what you pay for................

 

Most quality decoders have 100-150ma per function output.................... including the Hatton's one being used by the OP

 

 

I asked Express Models for the spec of the leds and resistors they were using but never got a reply.

 

>> Why the need to ask about the resistors - the SMD resistor values are already marked on their circuit boards.............. failing that, the resistor values could be checked with a meter..............

 

I have assumed 20mA per led and my decoder has a 100mA function limit without protection which meant it was operating flat out, so the extra resistor pulls the current draw down well within limits and the decoder works fine again.

 

>> Em..........R8249..........? ?

 

I found their instructions to be very clear, even to the point of explaining the wiring differences for 4 to many more function decoders in order to get the lighting effect required.

 

>> Yes I'd agree with the above, they also designed these DCC lighting circuits to work with most quality decoders, if extra resistors were required, they would have been added at the design stage .......................

 

 

My decoder was a TTS item hence the R8249 rating.

 

The only reason to avoid using an R8249 for general use is the limited CV adjustment, else they are a reliable and NMRA compliant decoder. Not to be compared with the earlier totally flaky R8215 decoder.

 

The reason I didn't spot the on board resistor values is old age and associated eyesight. I still wanted to know the led forward voltage and currents though.

 

Rob

[tractor_37260]

My decoder was a TTS item hence the R8249 rating.

 

The only reason to avoid using an R8249 for general use is the limited CV adjustment, else they are a reliable and NMRA compliant decoder. Not to be compared with the earlier totally flaky R8215 decoder.

 

The reason I didn't spot the on board resistor values is old age and associated eyesight. I still wanted to know the led forward voltage and currents though.

 

Rob

 

 

 

 

The Hornby R8249 has four function outputs, the max load per function output = 100ma   Front and rear LED lighting if using all 4 functions would not exceed  400ma 

Front markers/headlight on function 1  = 60/70ma  assuming 20ma per LED  

Rear markers/headlight on function 2  = 60/70ma     "        "     "     "       " 

Front tail lights               on function 3   = 40ma 

Rear tail lights               on function 4    = 40ma

Total load                                =              220ma      

   

However as you commented in the case of a 3 function TTS decoder it may prove a problem.

 

With both front rear markers/headlights and tail lights at each end on functions 1 and 2 =  total load = approx 220ma which exceeds the 200ma max for 2 functions.

 

However, I've fitted (ex Lima) Express lighting kits (with no alterations) to a number of Hornby TTS 37/40's also using function 3 via F25 to control new cab light LED's without only some minor issues with lights being on at the wrong end relative to direction initially. On one TTS 40  - function 3 on F25 would not work regardless of what I tried, however Hornby replaced the TTS decoder FOC as faulty.

 

Yes our eyesight becomes a problem as we all age............

 

Regards

Ken