Ian-1301567 Posted September 24 Share Posted September 24 Hi there, I have a small technical issue in regards I set up some lights for a loco of mine with front and rear lights now I followed the hornby wiring guide for a 8 pin decoder which seemed pretty straight forward now when it came to the V+ Common I connected the 2 wires together and soldered them to the V+Common connection and soldered Yellow to Pin 2 and White to Pin 6 but when I came to test it only the rear lights came on straight away but couldn't switch them off using the Elite Controller and the front lights don't work at all. Please could you clarify?. Link to comment Share on other sites More sharing options...
Brew Man Posted September 24 Share Posted September 24 And this would be better posted in the DCC forum. It will get better and more relevant responses. Mod note - moved across and merge with the duplicate thread. Link to comment Share on other sites More sharing options...
dBerriff Posted September 24 Share Posted September 24 Which decoder are you using? It is not possible to work out the precise connections circuit from your narrative. It might be better to include an image or sketch of the installation. If an LED does not light at all then the first thing to check is polarity. Link to comment Share on other sites More sharing options...
Ian-1301567 Posted September 24 Author Share Posted September 24 19 minutes ago, dBerriff said: Which decoder are you using? It is not possible to work out the precise connections circuit from your narrative. It might be better to include an image or sketch of the installation. If an LED does not light at all then the first thing to check is polarity. The decoder is a Hornby 8 pin decoder but I'll try and send an Image of the connection on my train the thing is if I had a short this would of burnt out the decoder. Link to comment Share on other sites More sharing options...
Ian-1301567 Posted September 24 Author Share Posted September 24 47 minutes ago, Ian-1301567 said: The decoder is a Hornby 8 pin decoder but I'll try and send an Image of the connection on my train the thing is if I had a short this would of burnt out the decoder. Pictures of connections now not sure whether it's a hornby decoder thinking about it has this loco came with decoder already connected. Link to comment Share on other sites More sharing options...
ntpntpntp Posted September 24 Share Posted September 24 (edited) Some iffy looking wiring joints on that first photo, and also those strips of 3 LEDs may draw rather more current than is expected for a typical decoder's lighting output. Those LEDs are meant for under-cabinet lighting etc. For testing just use a single small LED with a 1k resistor. Edited September 24 by ntpntpntp 1 Link to comment Share on other sites More sharing options...
Ian-1301567 Posted September 24 Author Share Posted September 24 Hi there, Now I've been told to come onto the DCC area has I have this bit of a dilemma and I have wired up a loco inline with the hornby directions for a 8 pin decoder and I have an issue with the front and rear lights as once the power to the Elite Controller is connected the rear lights just light up but can't switch them off with the controller and the front lights don't light up. Link to comment Share on other sites More sharing options...
Rog RJ Posted September 24 Share Posted September 24 I think more details of exactly how you have installed and connected the decoder would help, also photos of the installation please. OK now seen the other thread has pics. Installation looks dreadful. I would rip it all out and start again. Mod note - both threads merged. Link to comment Share on other sites More sharing options...
dBerriff Posted September 24 Share Posted September 24 As @ntpntpntp says. I don't recognise the decoder but typically they are only designed to drive simple head and tail LEDs so 2 to 4 in parallel with current-limiting series resistors. Link to comment Share on other sites More sharing options...
dBerriff Posted September 24 Share Posted September 24 (edited) If you find one set of lights stays permanently on it is possible you have overloaded and short-circuited the switching transistor for that function. I have seen this happen in a different context. Decoders are not designed to deliver more than a few 10s of milliamps for each function. It is not possible given the board size, nor is it necessary. Edited September 24 by dBerriff Link to comment Share on other sites More sharing options...
Ian-1301567 Posted September 24 Author Share Posted September 24 16 minutes ago, dBerriff said: If you find one set of lights stays permanently on it is possible you have overloaded and short-circuited the switching transistor for that function. I have seen this happen in a different context. Decoders are not designed to deliver more than a few 10s of milliamps for each function. It is not possible given the board size, nor is it necessary. So is that likely the lighting circuit that is broken so you just have a permanent light on all the time so I could probably use that as a cabin light as the train still runs normally. Link to comment Share on other sites More sharing options...
dBerriff Posted September 24 Share Posted September 24 (edited) I am only speculating on what might have happened. I cannot be sure. If it turns out that this output has indeed been damaged I would not use it for anything. You cannot be sure what else has been damaged. Test everything with a single diode and 1KOhm resistor in series as @ntpntpntp suggested. Make sure you get the LED polarity correct because it will not light up in reverse as next to no current will flow. Edited September 24 by dBerriff Link to comment Share on other sites More sharing options...
Ian-1301567 Posted September 24 Author Share Posted September 24 2 minutes ago, dBerriff said: I am only speculating on what might have happened. I cannot be sure. If it turns out that this output has indeed been damaged I would not use it for anything. You cannot be sure what else has been damaged. Test everything with a single diode and 1KOhm resistor in series as @ntpntpntp suggested. Make sure you get the diode polarity correct because it will not light up in reverse as next to no current will flow. So what would have caused the overloaded of the switching transistor if that was the case. Could me connecting 2 blue wires together and not individually may of cause the problem but having thought about it your just doing the same connection if you connected them individually. Link to comment Share on other sites More sharing options...
96RAF Posted September 24 Share Posted September 24 The blue is a common positive so yes you can connect both together. The yellow wire in the diagram is a switched negative for the rearward running lights which will show when the loco is in reverse. The black line in the diagram is the white wire which is a switched negative for forward running lights which will show when the loco is in fwd. These directional lights come under control of F0 and as stated which are on depends upon selected direction. Link to comment Share on other sites More sharing options...
Bulleidboy Posted September 24 Share Posted September 24 Is this of any help? Link to comment Share on other sites More sharing options...
dBerriff Posted September 24 Share Posted September 24 As I have tried to imply, we do not know that there is a fault on the decoder. It could be the LED strip or a solder joint that is faulty so more testing and measurement is required. We can only point you in the right direction. As has already been said you should not be trying to drive that kind of load with a DCC decoder so ditch the strip and use a single LED and series 1K Ohm resistor. 1 Link to comment Share on other sites More sharing options...
dBerriff Posted September 24 Share Posted September 24 As an aside, the now famous HM7000 manual has a good section on adding lighting to a decoder-board function outputs. 1 Link to comment Share on other sites More sharing options...
Darren-373700 Posted September 24 Share Posted September 24 On the first picture, the common + blue wires at the front of the loco you have soldered to the - pad of the LEDs so this light will not work. Swap them over see if you get any joy. Link to comment Share on other sites More sharing options...
dBerriff Posted September 25 Share Posted September 25 (edited) We advised against using the strips at all, or if we were going to be ignored, at least include a series 1KOhm resistor to limit the current draw. As the other channel is now permanently on, just swapping the connections (which I agree are reversed) could just lead to the same result for this channel. Reverse-biasing the diodes might have saved the decoder from further damage. Edited September 25 by dBerriff 1 Link to comment Share on other sites More sharing options...
Ian-1301567 Posted September 25 Author Share Posted September 25 7 hours ago, dBerriff said: We advised against using the strips at all, or if we were going to be ignored, at least include a series 1KOhm resistor to limit the current draw. As the other channel is now permanently on, just swapping the connections (which I agree are reversed) could just lead to the same result for this channel. Reverse-biasing the diodes might have saved the decoder from further damage. You see I thought the small markers in between the LEDs where diodes.So I understand when using single LEDs it is best to use resistors and diodes are these used in series together?. Link to comment Share on other sites More sharing options...
96RAF Posted September 25 Share Posted September 25 1 hour ago, Ian-1301567 said: You see I thought the small markers in between the LEDs where diodes.So I understand when using single LEDs it is best to use resistors and diodes are these used in series together?. Those led strips usually have a resistor for every three leds. When I used them for carriage lighting I planted another 1K resistor in series for every carriage length to fetch the brightness down - i.e. the limiting current. As suggested several times set up a token led and 1K resistor to use as a test lamp. Link to comment Share on other sites More sharing options...
ColinB Posted September 25 Share Posted September 25 I suppose you could have blown the output port that drives that channel. They do seem to stay on if the port gets blown. Normally I would test it on a decoder tester to check if the decoder is still working ok. This may seem a silly question but is the decoder inserted in the socket around the right way. That sometimes gives the effect that you are seeing. Link to comment Share on other sites More sharing options...
ntpntpntp Posted September 25 Share Posted September 25 (edited) 4 hours ago, Ian-1301567 said: You see I thought the small markers in between the LEDs where diodes.So I understand when using single LEDs it is best to use resistors and diodes are these used in series together?. LEDs are are form of diode. You only need an additional diode (connected inverse parallel to the LED) if you're feeding AC to the circuit, to protect against too high inverse voltage (LEDs don't like that and cannot withstand it like an ordinary diode can). You should always use a series resistor with an LED as it's a current driven device. You need to calculate the resistor needs to limit the current to within the LEDs specification (eg. for a small diode you might find on a model railway street light or a loco headlight 10mA is plenty, and the really small LEDs need less than that). There are online calculators to help you find the resistor given the supply voltage and current requirements etc. The reason we often suggest a 1K resistor (1000 ohms) is because it's a common value that's generally suitable and safe for an LED in a 12V-15V DC circuit as we find on model railways. You can go higher resistance if you want to dim down the LED. The small black components you see on the LED strips are resistors (not diodes) as @96RAF says above. The problem is those strips are designed to draw a lot more current because they're for much brighter uses (eg. under-cabinet lights as I mentioned in a previous reply), so you may have blown the decoder's function output by drawing too much current. I use these strips sometimes for things like lighting in engine sheds and workshops but that's directly from a supply which can handle 1Amp or so, not a decoder's output 🙂 Even then I add another resistor in the circuit to reduce the current and brightness. Bottom line is DON'T use those LED strips for testing decoder lighting, as several of us have said above 🙂 [edit] I "borrowed" a segment of LED strip from my son's stores 🙂 Similar to yours. At 12V DC it draws 50mA, actually a little less than I expected but still 3-4 times more than (say) a pair of small loco headlights. Remember also the decoder output could be running at somewhere nearer to the DCC track voltage so the current draw of the strip could well be more. At 15V that same strip drew 90mA (many decoders have a maximum rating of 100mA for a function output). Edited September 25 by ntpntpntp Link to comment Share on other sites More sharing options...
ColinB Posted September 25 Share Posted September 25 (edited) 41 minutes ago, ntpntpntp said: LEDs are are form of diode. You only need an additional diode (connected inverse parallel to the LED) if you're feeding AC to the circuit, to protect against too high inverse voltage (LEDs don't like that and cannot withstand it like an ordinary diode can). You should always use a series resistor with an LED as it's a current driven device. You need to calculate the resistor needs to limit the current to within the LEDs specification (eg. for a small diode you might find on a model railway street light or a loco headlight 10mA is plenty, and the really small LEDs need less than that). There are online calculators to help you find the resistor given the supply voltage and current requirements etc. The reason we often suggest a 1K resistor (1000 ohms) is because it's a common value that's generally suitable and safe for an LED in a 12V-15V DC circuit as we find on model railways. You can go higher resistance if you want to dim down the LED. The small black components you see on the LED strips are resistors (not diodes) as @96RAF says above. The problem is those strips are designed to draw a lot more current because they're for much brighter uses (eg. under-cabinet lights as I mentioned in a previous reply), so you may have blown the decoder's function output by drawing too much current. I use these strips sometimes for things like lighting in engine sheds and workshops but that's directly from a supply which can handle 1Amp or so, not a decoder's output 🙂 Even then I add another resistor in the circuit to reduce the current and brightness. Bottom line is DON'T use those LED strips for testing decoder lighting, as several of us have said 🙂 Actually I looked at his circuit he does not need any additional diodes it is DC only. Most of those diodes take 20 mAmps, so 3 is 60 mAmps, the port on a decoder is rated at 100 mAmps so shouldn't be an issue although I can't remember if that is for one or all of them. If so then two lots of 3 leds would be a 120mAmps which might have killed it. Now for simplicity I would normally use a single diode to test it, but I see no reason why it won't work with three. As to 1 kiloohm resistor, you use ohms law to do it properly which is R = V/I where V is 12 volts minus the drop across the diode (about 2.2 volts) and the current which normally you want at about 5 milliamps, although it depends on the type of diode used. Some of the high visibility tower diodes you will find they are still too bright. As I said in my previous post he has wired it up correctly, so possibly one of those stray wires killed the port or it is something like it is not plugged in properly. The Hornby decoders don't have any protection on these ports so you have to be very careful with them. Trouble is you can blow the port but the decoder still works, so that could be what has happened. It might be that V+ is 15 volts rather than 12 Volts but the extra 3 volts shouldn't make that much difference. Edited September 25 by ColinB Link to comment Share on other sites More sharing options...
ntpntpntp Posted September 25 Share Posted September 25 38 minutes ago, ColinB said: It might be that V+ is 15 volts rather than 12 Volts but the extra 3 volts shouldn't make that much difference. Actual measurement of my example (looks to be the same design of LED strip) draws 90+ mA at 15V DC. So getting up near the max 🙂 Link to comment Share on other sites More sharing options...
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