Woodland Scenics stick-on LEDs

[MattR]

I recently picked up some of these on sale at the hobby shop. I have an analog DC Bachmann controller (I live in the U.S.) that has wire hookups on the front that provides 12V power for accessories. The question is, can I cut off the Woodland Scenics light hub connector from the end of the led wires and hook the leads straight into my controller as is, or will I need to add a resistor first? Some sources I've read online say that these already have resistors built into the LED unit, but I'm not 100 percent certain and don't want to blow the LEDs. Anyone have any experience with these? Thanks!

[dhjgreen]

2 hours ago, MattR said:

I recently picked up some of these on sale at the hobby shop. I have an analog DC Bachmann controller (I live in the U.S.) that has wire hookups on the front that provides 12V power for accessories. The question is, can I cut off the Woodland Scenics light hub connector from the end of the led wires and hook the leads straight into my controller as is, or will I need to add a resistor first? Some sources I've read online say that these already have resistors built into the LED unit, but I'm not 100 percent certain and don't want to blow the LEDs. Anyone have any experience with these? Thanks!

No experience of them, but they are each rated in mA which suggssts they have a resistor.  No harm in putting a resistor in series to try them out.

[WIMorrison]

These are designed for the woodland scenic lighting system and I think that you will need to feed these with 3v or an appropriate resistor if you are using 12v. 

 

If using 12v supply, I would start with a 1k resistor and go down to no lower than 500 ohms if 1k is too dim.

[298]

It'd be better to use a LM2596 step down transformer so the output voltage is never exceeded, regardless of the input voltage. They are a couple of quid on eBay.

[MattR]

Excellent! I have a few 1k resistors on hand and might try one and see how it does. Thanks for the advice!

[John ks]

On 23/02/2022 at 04:19, WIMorrison said:

If using 12v supply, I would start with a 1k resistor and go down to no lower than 500 ohms if 1k is too dim.

I basically agree with starting with a 1k resistor, but i have found modern LEDS can be very bright & i have used 4k7 & higher value resistors to get the required dimness

I had a look on woodland scenics web site & from the image of the stick on LEDs I could not see a resistor 

On 23/02/2022 at 03:21, dhjgreen said:

No experience of them, but they are each rated in mA which suggssts they have a resistor.

The mA rating is generally the highest current the device can carry & to me doesn't indicate that there is a resistor present 

 

On 23/02/2022 at 03:21, dhjgreen said:

No harm in putting a resistor in series to try them out.

I totally agree 

John

 

[Crosland]

11 hours ago, John ks said:

The mA rating is generally the highest current the device can carry & to me doesn't indicate that there is a resistor present 

 

 

For LEDs it does (or, less likely, some form of semiconductor current limit). If there is nothing to limit the current through a LED then the current  will be a lot higher. Until the magic smoke escapes.