Re Lighting Issues

[Ian-1301567]

1 hour 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 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).

Hi there Ntp,

Yeah I had been using these strip lights on my carriage coaches so no decoder requirement. So if I do use these strip lights with a decoder it's best to connect a 1k resistor in series with the LED.So diode requirement is only if being used on AC circuit. If I test the decoder on my LiasDCC what will I notice if the lights are not switching will there be nothing happening. 

[Ian-1301567]

3 hours ago, ColinB said:

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.

Hi Colin,

If I test the decoder using my LiasDCC what generally happens if the switching circuit has blown on the decoder will there be any lights lighting up or will there be nothing happening. 

[ntpntpntp]

24 minutes ago, Ian-1301567 said:

If I test the decoder on my LiasDCC what will I notice if the lights are not switching will there be nothing happening. 

Depends if the output has blown to open circuit or a short.  If it's failed the LED on the tester will either stay on or off and not react to you switching the headlights on or off.   So make sure the motor is responding (to confirm you have the correct address).   If this were a connection with more pins I'd also test the other function outputs light up in response, but the 8 pin socket only drives the front/rear lights.

[96RAF]

6 minutes ago, ntpntpntp said:

but the 8 pin socket only drives the front/rear lights.

The green wire reacts to F1 and the flying purple lead on the decoder reacts to F2.

[ColinB]

2 hours ago, Ian-1301567 said:

Hi Colin,

If I test the decoder using my LiasDCC what generally happens if the switching circuit has blown on the decoder will there be any lights lighting up or will there be nothing happening. 

By LaisDCC do you mean the LaisDCC tester. If so then it should illuminate the leds on the test board that is how I test my decoders. You are using the F0 function looking at your circuit then you don't need to connect anything else. So press F0, run the motor forwards and the F led on the board will illuminate, run the motor backwards and the R led will illuminate. If there is anything wrong with the F0 functions, this won't happen. the only other thing to check if they don't work turn the decoder round and see if it works. The other that I have had happen is if the flying lead isn't insulted properly and it accidentally touches something metal which will kill the ports.

[Brew Man]

12 hours ago, Ian-1301567 said:

Hi there Ntp,

Yeah I had been using these strip lights on my carriage coaches so no decoder requirement. So if I do use these strip lights with a decoder it's best to connect a 1k resistor in series with the LED.So diode requirement is only if being used on AC circuit. If I test the decoder on my LiasDCC what will I notice if the lights are not switching will there be nothing happening. 

Can you not take the advice of several people here and ditch the strip lights. Test your circuit with one LED only.

[Ian-1301567]

3 hours ago, Brew Man said:

Can you not take the advice of several people here and ditch the strip lights. Test your circuit with one LED only.

Yeah I'll do that instead of using strip lights. 

[Ian-1301567]

16 hours ago, ColinB said:

By LaisDCC do you mean the LaisDCC tester. If so then it should illuminate the leds on the test board that is how I test my decoders. You are using the F0 function looking at your circuit then you don't need to connect anything else. So press F0, run the motor forwards and the F led on the board will illuminate, run the motor backwards and the R led will illuminate. If there is anything wrong with the F0 functions, this won't happen. the only other thing to check if they don't work turn the decoder round and see if it works. The other that I have had happen is if the flying lead isn't insulted properly and it accidentally touches something metal which will kill the ports.

Hi Colin,

It's seems that I have been quiet fortunate in the decoder being OK as everything seems to be functioning in regards the testing system LiasDCC.So I get the feeling I may of connected the decoder the wrong way round. 

[ColinB]

7 minutes ago, Ian-1301567 said:

Hi Colin,

It's seems that I have been quiet fortunate in the decoder being OK as everything seems to be functioning in regards the testing system LiasDCC.So I get the feeling I may of connected the decoder the wrong way round. 

It is so easily done especially when a lot of the decoders don't have pin 1 marked clearly. Done it loads of times. I am really glad you haven't blown up the decoder. Those testers are really useful.