Live Steam article showing capacitor in parallel with LEDs in Signal Head

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Atkinson_Railroad
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Re: Live Steam article showing capacitor in parallel with LEDs in Signal Head

Post by Atkinson_Railroad » Thu Aug 17, 2017 9:54 pm

Good info Bryce.

I myself am not worried about the circuit, just trying to understand the purpose of the capacitor because the author
of the article failed to explain the reason for it "shunting" the LED. Also agree the value rating of the capacitor is pretty small
for purposes of doing much else.

Again, Thanks!

John

Krigare1
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Re: Live Steam article showing capacitor in parallel with LEDs in Signal Head

Post by Krigare1 » Fri Aug 18, 2017 12:00 am

From the LSOR related author: This is my first posting on this forum and hope you will excuse any errors in procedure I maybe committing. After learning of the posted discussions about the purpose of the capacitors connected in parallel with the LEDs used in my block signal face plate article ( 2017 Mar/Apr issue of Live Steam and Outdoor Railroading ) "Iconic Railroad Fixture Gets a Redo", I thought I would help clarify their usage. The face plate circuitry is connected to a controller circuit board via a dedicated underground cable run. The LEDs are switched by an IC on the controller board which has multiple open collector style outputs with active LOW states. The capacitors in question are indeed "overkill" and rarely used in most applications, however in this instance I added them to simply serve as another level to dampen or suppress any potential RF or EMI radiated energy from nearby cell towers and multi use transmitters that could to cause the LEDs to flicker from the cable runs which in turn act like antennas thanks to the floating or "open" inactive state of the IC outputs. There is a negligible benefit of transient protection with the capacitors. During daylight ops the flickering should not be noticeable, however when night running occurs and keeping in mind the high optical magnification of the semi-spherical lens, there would be an increased possibility for some LED flickering to be seen near the front of the face plate. This flickering would be somewhat awkward at night especially when the signal system is off. I hope my explanation here has satisfied all on this subject and sincerely appreciated the attention it has drawn, THANKS to those members that posted about these capacitors. - Dan

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Atkinson_Railroad
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Re: Live Steam article showing capacitor in parallel with LEDs in Signal Head

Post by Atkinson_Railroad » Fri Aug 18, 2017 5:23 am

Excellent! Thank you so much Dan for taking the time to sign on to the forum and share your clarification
related to the Live Steam magazine article. Your further explanation of the capacitors is greatly valued.

The bulk of the discussions on the board fit a place devoted to fabrication and or working with materials and machining in nature.
At the root of many of the projects however is "Railroad". And signaling fits [railroad] as well as the study of steam; casting metal,
civil engineering, mechanical movements, machining, welding, repairing, and all of the other disciplines required to make something happen.
The subject of signaling tends to be at the very end of the list however for most pursuing the hobby which I've long ago understood and continually remind myself.

Two LONGS, a Short, and a Long : )

Welcome to the chaski board.

John D. Atkinson

Krigare1
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Re: Live Steam article showing capacitor in parallel with LEDs in Signal Head

Post by Krigare1 » Sun Aug 20, 2017 3:12 am

Thanks John for the welcome, I truly appreciate it.

As a brief employee (student brakeman) of the ATSF RR I can assure you signals are extremely critical when your are long freight train traveling at 70 MPH on M/L...you won't have time to check switch points and react accordingly so you have to totally rely on signal aspect indications to guide your upcoming track movement. As a member of a live steam club for over 30 years and working with our signal system it is amazing the integral role they play. They also visually enhance the riding experience for the public train passengers as I have noticed when approaching both turnout and block signals whenever I was the engineer. In some respect they add a level of realism to the club's layout.

Likewise John --.-
- Dan

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BigDumbDinosaur
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Re: Live Steam article showing capacitor in parallel with LEDs in Signal Head

Post by BigDumbDinosaur » Sun Aug 20, 2017 8:45 am

Krigare1 wrote:As a member of a live steam club for over 30 years and working with our signal system it is amazing the integral role they play.
I'm amazed you can get your members to obey them. At our club, passing signals at STOP is the norm.
Science makes it known. Engineering makes it work.

Krigare1
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Re: Live Steam article showing capacitor in parallel with LEDs in Signal Head

Post by Krigare1 » Sun Aug 20, 2017 1:40 pm

From the LSOR related author: This is my first posting on this forum and hope you will excuse any errors in procedure I maybe committing. After learning of the posted discussions about the purpose of the capacitors connected in parallel with the LEDs used in my block signal face plate article ( 2017 Mar/Apr issue of Live Steam and Outdoor Railroading ) "Iconic Railroad Fixture Gets a Redo", I thought I would help clarify their usage. The face plate circuitry is connected to a controller circuit board via a dedicated underground cable run. The LEDs are switched by an IC on the controller board which has multiple open collector style outputs with active LOW states. The capacitors in question are indeed "overkill" and rarely used in most applications, however in this instance I added them to simply serve as another level to dampen or suppress any potential RF or EMI radiated energy from nearby cell towers and multi use transmitters that could to cause the LEDs to flicker from the cable runs which in turn act like antennas thanks to the floating or "open" inactive state of the IC outputs. There is a negligible benefit of transient protection with the capacitors. During daylight ops the flickering should not be noticeable, however when night running occurs and keeping in mind the high optical magnification of the semi-spherical lens, there would be an increased possibility for some LED flickering to be seen near the front of the face plate. This flickering would be somewhat awkward at night especially when the signal system is off. I hope my explanation here has satisfied all on this subject and sincerely appreciated the attention it has drawn, THANKS to those members that posted about these capacitors. - Dan

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