LED current draw limits


tootnkumin

tootnkumin

Well-Known Member
Staff member
The Tsunami2 decoder document says each of the function outputs is capable of 100ma. I want to attach 4 smd's (factory fitted) to a single function tab (f0 headlights) using 1k Ohm resistors on each SMD's negative lead. Is any overload of the output likely? Or any dimming of the brightness of the LED's collectively or individually?
 
nope, no problem ..
at an average of 20ma [max current], it should give 80ma or less ..
using individual dropping resistors is a good idea ..
 
wvg_ca said:
nope, no problem ..
at an average of 20ma [max current], it should give 80ma or less ..
using individual dropping resistors is a good idea ..
Click to expand...
I thought it would be. I have read elsewhere that you should always use individual resistors for each LED. The main reason for doing it this way is because on the club layout where there are sometimes shorts caused by derailments, the break in the track power turns off the lights and if they were separated onto other outputs, I have to turn each one back on. There's not enough room for a current keeper.
 
i used a function output to drive a small motor that opened a HO scale coupler .. i had to be careful to stay under 100ma
 


I used a lot of LED's on my layout for signals. Tomar's Dwarf green over red signals are by the turnouts to indicate position, while in some locations I have the three color block signals. The Tomar signals' instructions indicate the use of a resistor for each LED while I have signal animators from Logic Rail and their instructions show one resistor on the common lead.

Also, Tomar's grade crossing signals require a resistor for each LED.

Greg
 
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