Re: Lighting question
- --- In AirWire@yahoogroups.com, "Bob Small" <rds@...> wrote
> I have added a diagram in the Files section.
I built a board as per your diagram, and it works. However, when I use
5mm warm white LED's on the headlight circuit they glow very dimly when
they are supposed to be off. I am not sure they are supposed to do
this (I don't see any information in the airwire decoder that allows it
to conform to Rule 17--dimming of the headlights). Interestingly, when
I place a 3mm super bright white LED in its place it goes off properly.
I am using the following components: the diodes you reccomended
1n4001, the resistors on the headlight circuit are 470 ohm resistor in
series with 2 7000mcd 20mA 3.2V warm white 5mm leds (this is with the
lamps glowing) or the same resistor with 2 3000mcd 20mA 3.6V regular
white 3mm leds (off completely). Any thoughts as to why this is
happening. Oh yah, I am running a 14.4 V NIMH battery pack.
Hope I gave you enough information.
Thanks for everyones help--I am really having fun with this, and I was
so impressed with myself when the lights came on and went off with the
throttle! What a blast.
- Hi Matt,
Glad you enjoy it.
I had a close look at my NW2. And I see exactly what you describe.
The "off" light is actually very slightly on. Instead of being totally
clear it is a sort of milky white.
Obviously there is a very slight current leak somewhere, and, as you
have discovered, some LEDs will be slightly "on" with this small
I don't know if I can measure this very small current (I only have very
basic electronic equipment) but I'll setup a test AirWire with a couple
of LEDs and investigate.
- --- In AirWire@yahoogroups.com, "Bob Small" <rds@...> wrote:
> Hi Matt,
> Glad you enjoy it.
> I had a close look at my NW2. And I see exactly what you describe.
> The "off" light is actually very slightly on. Instead of being
> clear it is a sort of milky white.Glad I am not imagining it. It is actually somewhat prototypical, if
not exactly right for something called "Rule 17." If I understand
the rule correctly it requires the dimming of the headlight when a
train is sitting idle--not copletely off. So for my pruposes I am
not sure I will correct the "problem." Though I would like to know
where the problem is--though if it is in the airwire board, not much
I could do about that I guess.
Thanks for the reply, I await the results of your tests.
When this thing is done I'll try and post some pictures--maybe next
- I had a quick look but don't know that I've come up with much.
I don't think the problem is with the AirWire. If the lights are
switched off (F0) then there is no "whiteness" in the LEDs, so I assume
that there is no current leakage through TM4-1 or 2.
So the only other leakage path is through one of the "constant lighting
diodes". The 1N4148 has a reverse leakage around 25nA and a 1N4001 is
around 5uA. The white LEDs must be sensitive to this very small current.