Flicker Free lights using a Super Capacitor and Fibre Optics.
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See
suppliers of
fibre optic cable.
Lights
in passenger coaches and vans have the annoying tendency due to their light
weight and possible poor track pickups, to flicker while operating in a moving
train. Using a similar circuit as the one below will reduce this flicker
completely in LED installations in vans.
The circuit below is from a
This
circuit can be used on both DC and DCC to power
all the LEDs and will allow any form of cheap easy pickup to be used (see
photo). This circuit could be tried on a passenger coach with incandescent
lamps but due to their higher current requirements may require more capacitors
or use the 1 farad Super Capacitor that is now available. Also if passenger
coaches with lamps that are causing problems with booster circuit breaker
resets (see below) this circuit could be modified to supply the lamps.
This circuit if used on DC is not polarity dependant. If requiring
directional tail lights on a guards van, some form of switching selecting one
of two LEDs that will have the fibre optic cables attached to. This will be
left to each individual to determine how to do this.
Incandescent lamps draw 15 to 40 mAs and LEDs only
draw, 2 – 5 mAs if high intensity LEDs are used by adjusting LED “series”
resistor. In passenger coaches incandescent would better due their better
overall 360 degrees radiating pattern where as LEDs have a very directional
beam.
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The components soldered together and attached to the wagon floor or
suitable location with Blu Tak. Blue cylinder is the Super Capacitor. Note: The black stripe on the zener diode is connected to the positive
supply. |
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Drill holes the same diameter of the fibre optic cable in the body
where lights are to be located. 0.7 mm in this case. With the fibre optic cables located, apply the barrel of the soldering
iron to mushroom over the end so that the cable does not “disappear” into the
wagon. |
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Drill 2 holes in the LED to locate the fibre optic cable. This must be
a tight fit. Do not “super glue” the cables in the LED. Be careful not to drill too far into the LED body and damage the LED
element. The resistor used for the LED is not critical. 1,000 ohms will be
sufficient, but if using a few LEDs for coach illumination, you may need to
increase resistance to decrease the current. |
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Make some easy simple pick ups for the wagon. These do not need to be
great as the circuit will compensate for poor power pick up. As shown, I used 0.4 mm phosphor bronze wire and just drilled a 0.4 mm
hole through the bogie bolster. Solder wire to pick up and through hole to the bridge rectifier. Remember to have the axles reversed on the other bogie. |
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This is the final product on the track and running around the layout,
no evidence of flickering. See how you go. |
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Passenger Coaches.
Many
modellers have bought coaches, with all the relevant components installed,
place them on the layout and everything works well. This is true with DC, but
when using these coaches on DCC, they can cause problems due to the “inrush”
current preventing the booster or circuit breaker from resetting. This problem
is well documented with sound locos and all manufactures are working on a
solution. A solution to “fix” this problem, now, is to place a 12 volt 21 watt lamp or 1156 in parallel with
the booster or circuit breaker.
Some
modellers don’t like this approach, due to the fact that when there is a short,
there is 1.5 – 2.0 amps current still flowing. This will not cause any problems
if this short is attended to immediately.
Other
modellers have wired in, at the points or turnout, an 1156 lamp in series with
the frog power wiring.
At
Joe Fugate’s fantastic Siskiyou Lines, Joe has wired in
1156s to divide all his layout into “train length” power zones. See his web
site and the below message that he posted on the Digitrax group. Using the 1156
in this fashion will prevent the booster from ever shutting down.
The problem with these coaches and sound decoders.
With
the lamps in a coach or the capacitor in the circuit that provides power to
these lamps, when supplying power to the layout initially or after a short,
there is a surge “inrush current” that is much larger that normal operating
current. The cold resistance of a lamp cause about 10time the normal amount of
current to flow initially. The same for charging a capacitor in any circuit,
including these coach lighting ones and sound decoders. This “inrush current”
is sufficient enough, and depending on how many coaches or sound decoders on
the particular power zone, to prevent the booster or circuit breaker resetting.
With some adjustments to the response time and trip current of the circuit
breakers this can be reduced, but other still have problems with their
“combinations”.
Combinations
include, how many coaches and sound decoders in a power zone and the system
characteristics. These include the booster, circuit breaker and the overall
layout. A lot of layouts don’t have any problems, but some do. This “problem”
is not consistent.
There
is not a great deal we can do with sound decoders, boosters, circuit breakers
and “lighting circuit boards” that are fitted to our layouts NOW apart from
fitting the above “parallel lamp fix” In the case of coach lighting circuits
boards, we can modify the input circuitry to the coach.
This
can be done with the flicker free circuits BUT the input inrush current has to
be reduced.
Normal
low cost bridge rectifiers can have an effect on the shape of the DCC signal
but in these circuits it does not matter due to the power “downstream” from the
bridge rectifier not needing a DCC signal component, only rectifying the DCC to
provide DC. The inrush current to charge the capacitor is reduced by the series
resistor to an acceptable level, but this will take time to charge the
capacitor.
In
the Super Capacitor flicker free circuit, the DCC track voltage provides the
normal light globes or LEDs power requirement plus extra for keeping the super
capacitor charged. When the power is interrupted, the super capacitor provides
this current. The bigger the capacitor, the longer the time or greater the
current. The bridge rectifier isolates the rest of the track from the super
capacitor.
Experimenting
with the super capacitors and the input resistor to give the required operating
current of all the lights in a passenger coach, will allow you to isolate the
inrush current problem. The more load (lamps) here is the input resistor value
has to be reduced, but this when having a lot of coaches may impact on the
overall inrush current. Experiment here and see what happens.
Below
shows a coach with 8 LEDs using a resistor for current limiting. This resulted
in a flickering lighting effect. The above circuit was recommended to the
modeller to give flicker free operation.
Using
LEDs instead of incandescent lamp could be set up like in this coach, with the
LEDs facing reflecting tape that has been secured to the coach roof to give a
better diffused light. This is just another example for coach lighting that has
been used. Experiment here. For the next installations I will use Prototype
While High intensity LEDs that don’t have the blue tinge that will be more
suitable for incandescent lighting that is in our coaches.
Someone
please add this circuit to incandescent lamps and let me know how it works.
Joe’s
message.
-----Original Message-----
From: Digitrax@yahoogroups.com [mailto:Digitrax@yahoogroups.com] On Behalf Of
Joe Sent: Sunday, 24 July 2005 1:34 AM
To: Digitrax@yahoogroups.com Subject: [Digitrax] Re: Using #1156 bulbs in
series with the points
--- In
Digitrax@yahoogroups.com, "Joe Batson" <joebmcse@m...> wrote:
> Own
our layout we run multiple units MUed together on 3% grades. Using
> the
light bulbs in series with the power distribution drops the voltage
> on
the track so low that the head lights don't glow any more. Even with
> 3
narrow gauge locomotives working on the 4% grade the voltage on the
>
track is down to about 8 volts instead of the normal 14 volts and the
> bulbs
are noticable glowing, some pretty bright.
>
> We
have tried to us the 1156 bulbs but the results on our layout were
> not
very good.
>
> JoeB
For the
bulbs to work effectively, you need to make sure each section protected by the
bulbs will rarely approach 2 amps load, or the bulbs will intervene and start
doing what they do well -- limit the current to 2 amps.
On my
Siskiyou Line, I run diesel lashups of 3-4 locos at the head end, and 2-3
diesels as mid-train helpers. At typical HO amperage draw of .2 amps per loco
times 7 locos in one train, that's 1.4 amps.
My
earlier experiments with the bulbs lead me to conclude that splitting the
layout up into train-length blocks -- so that at most you would typically only
have the current draw from one train's worth of locos going through a single
bulb -- then the bulbs would work well.
Trying to
protect and entire power district with a single 1156 bulb will generally be too
much railroad because you will be protecting multiple trains all through one
bulb. If you get between 1.5 amps and 2 amps current draw, the bulb will start
to glow and it will interfere with loco performance.
One
solution is to use the bulbs only on the power feeds to frogs, then if you run
a turnout wrong, the bulb will prevent the booster from seeing a short.
Another
solution is to do what I have done and gap the track similar to how you do for
cab control and protect each block with a single 1156 bulb in series with the
feeders for that block. I can tell you from experience that this technique
works very well and more or less "short proofs" your DCC layout. It
took one other fellow and me three 8 hour days to cut the gaps and rewire my
large HO layout to have the bulbs in place like this, and the result was
*excellent*.
Yet
another possibility that I have not investigated much would be to try two or
more bulbs in parallel, since this should increase the current limit.
And
finally, you can get 12V appliance bulbs for RVs that run at higher wattages
than the 1156 bulbs. The 1156 bulb is about 12V 25 watts. You can get RV
appliance bulbs that are 12V 50 watts for $2-$4 each, and they should have a
higher current limit. Some experimenting could provide useful data.
I can say
this much: my experience with the 1156 bulbs on my HO Siskiyou Line has been so
overwhelmingly positive that I am absolutely sold on the bulbs as a way to
"short proof" a DCC layout.
--Joe
Fugate