I have just purchased a Bachmann Baguley Drewry diesel and am interested in fitting lights. Has anyone had a go at this who could provide advice on type of resistors required and suitable LEDs?
Thanks
Peter
This sounds like a job for the Electronics SIG. :-)
There are online LED resistor calculators such as this one.
LED resistor calculator (https://uk.rs-online.com/web/content/discovery/tools-and-calculators/led-resistor-calculator?srsltid=AfmBOooOVr4KbucJ1yni1s7FR3FoMccJjyfcCyK_k4RmPm9wxixnXc6E)
White LEDs have a forward voltage of about 3 V or a bit more. How much current will depend on the LED and how bright you want it. Often the typical current values for LEDs is too bright for model railway use. 5 mA may be ample. Operating voltage is another matter. Nominally model railway motors are 12 V maximum. , but not many controllers put out a constant voltage for a given throttle setting. Many are pulsed and give out peaks considerably higher. Also pulsed supplies make LEDs look brighter than ones powered by supplies that have a constant supply of equivalent average voltage.
You can probably start with the assumption of 12 V even if you rarely if ever drive at maximum speed.
That suggests starting with a resistor of about 1 k and see how it goes.
There are surface mount LEDs that are available pre-wired in a variety of sizes, e.g.
pre-wired LEDs (https://www.ebay.co.uk/itm/125497393326?var=426535053247&gad_source=1&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338723872&toolid=20006&customid=FCx5FMIiAAAAkOWvkqD5vBbRduMyAAAAAA)
Thanks for this advice Graeme!
On DCC I use surface mounted leds with a 47k resistor.