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L.E.D. Headlight Wiring On 'P.S.C.' HOn3 Goose ?
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 Posted: Fri Jun 26th, 2020 03:55 pm
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Wayne Taylor
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I recently acquired a Precision Scale HOn3 Goose #5 (Pierce Arrow Freight),
at a reasonable price due to condition. 

The goose is unassembled,
as the previous owner had apparently been trying to replace the burned out bulbs. 

I ordered some nano LED lights, but have 2 problems:
1)  They are rated at 1.5 Volts.  Any current over that will destroy them.
2)  All the factory wiring has been removed, and leads cut at the motor terminals.

Anyone out there know how this was originally wired? 

There is an electrical post near the motor, attached to the frame,
where the current from one rail was probably picked up,
but all wiring is missing.





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 Posted: Sat Jun 27th, 2020 06:28 am
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corv8
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Re those mini LEDs...
Go by trial and error, and start with 3000 Ohms...

I have various resistors from 400 - 2000 Ohms,
and connect them in series, with a 16v DC power source,
then remove one at a time, until I feel I have found a good value.

However, maybe it's better to try at the decoder outlet directly,
as some LEDs apparently are more sensitive to the current coming from a decoder,
than to straight DC.

Guess why I know.

And, the same LED from a different supplier,
may burn out at another value.




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Gerold
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 Posted: Sat Jun 27th, 2020 10:46 pm
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Wayne Taylor
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Thanks for the reply.

I should have mentioned that this model is a DC model,
over 20 years old, from before the decoder era.

The original bulbs were incandescent and everything runs off the DC track.

The bulbs are burned out,
and the previous owner was trying to convert incandescent to LED lighting.


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 Posted: Sat Jun 27th, 2020 10:57 pm
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Steve P
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Wayne,


You need to design the circuit for both the rated Voltage and rated Amperage of your LEDs.

If you don't have an Amperage rating for them, 20 mA is probably safe.


The theory is here.

A web based calculator is here.


Steve




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 Posted: Sun Jun 28th, 2020 11:13 am
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corv8
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Had DCC in my head as I always fight the gremlins of it...

If you want to use DC only it's easier, but start high first.




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Gerold
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 Posted: Mon Jun 29th, 2020 09:26 am
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Helmut
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The best way for DC'ers to achieve an (almost) constant lighting is this:





I've drawn only four of them, the capacity of the regulator is 400mA.

The capacitor's value depends on the current you want to draw.
It is ~ 100µF/35V per 4 LEDs.

For directional lighting on the Goose (forward only),
one diode instead of the rectifier suffices, but the capacitor's value must be doubled.




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 Posted: Mon Jun 29th, 2020 12:49 pm
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Steve P
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Helmut,

Shows how much I know about "DC" setups,
I assumed that the track had DC voltage fed to it.

But this circuit implies that AC voltage is fed to the track,
and you use the bridge-rectifier + pin regulator to convert it to DC?

Steve




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 Posted: Mon Jun 29th, 2020 01:35 pm
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Steve P
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Helmut,

I thought more about this circuit.

Is the purpose of the bridge-rectifier, to keep polarity to the LEDs constant,
even when polarity reverses on the track, when changing direction?

And the step-down regulator keeps the brightness stable,
as voltage ramps up/down?

Steve




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 Posted: Mon Jun 29th, 2020 05:41 pm
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Helmut
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Steve P wrote:  
Is the purpose of the bridge-rectifier, to keep polarity to the LEDs constant,
even when polarity reverses on the track, when changing direction?

And the step-down regulator keeps the brightness stable,
as voltage ramps up/down?


Exactly.  :2t:




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