DCC and LEDs

  • Thread starter CharlieBear
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CharlieBear

CharlieBear

Registered
7 Apr 2020
31
Didsbury
I have two buffer stops with lantern now if an LED is inserted into the lantern and power taken from the track (20v) I assume the LED will flash (but not noticeable) but I also assume track power will blow the LED how would I get around this?
 
dunnyrail

dunnyrail

DOGS, Garden Railways, Steam Trains, Jive Dancing,
25 Oct 2009
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St.Neots Cambridgeshire UK
Two possible ways there may be more. Best bet would be to get a suitable rated LGB Bulb.
Other option would be to make an Ac/Dc converter but even then you would need a resister to reduce the voltage to that of the Diode.
 
PhilP

PhilP

G Scale, 7/8th's, Electronics
5 Jun 2013
26,184
Tamworth, Staffs.
I have two buffer stops with lantern now if an LED is inserted into the lantern and power taken from the track (20v) I assume the LED will flash (but not noticeable) but I also assume track power will blow the LED how would I get around this?
Yes, in theory, it will 'flash', but the frequency is such that you will not notice it..

It is frowned upon, to reverse-bias a LED (for the half-cycle it is 'off') but it should not do any damage.
You need to limit the current through the LED.. A 1K resistor should be adequate for this. - You can vary this, a little, if the LED is too dim or too bright.

If you are making the LED brighter, then you are increasing the current through it, so it would eventually fail if you reduce the resistor value too much.
Without knowing the specifications of your LED's, I would not go below 820 ohms. - Brighter.. It is better to use a 'high-intensity' LED that can be run at a lower current, then over-drive a standard LED.
To make the LED dimmer: Try values of 1.5 - 2.7 K.

K = kilo-ohm (1K = 1000 ohms)

HTH?

PhilP.
 
CharlieBear

CharlieBear

Registered
7 Apr 2020
31
Didsbury
Thanks PhilP and Jon
I'll give it a go with the LED on the basis that if it works it shouldn't need replacing.
 
D

Dan

Registered
28 Jan 2010
305
Eastern MA
In large scale, 1k resistor is only good for the 20ma led. you need 2K (2.2k is better) for a 10ma led!!!! And this assumes a 3 volt led. I go slightly higher with my resistors as I have a dcc system with 25 volts at the track.
 
Greg Elmassian

Greg Elmassian

Registered
8 Mar 2014
4,053
San Diego
www.elmassian.com
to protect from reverse voltage, put a normal 1N4002 (or greater) in series with the LED and resistor. LEDs do not have a high PIV rating like normal diodes, as Phil mentioned.

Greg