Bi-directional lighting on HSTs

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Re: Bi-directional lighting on HSTs

Postby TimberSurf » Thu Jul 12, 2018 4:56 pm

Yep, currently have the ubiquitous FIBRE OPTIC LAMP (still readily available for £6 :lol: ) bundle in my bits box plus some very expensive industrial comms fibre cables! :D
Bi-colour LED's are two LED's "back to back" in the one package with just two leads, so changing the DC polarity across them changes the colour (AC gives both colours)
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Re: Bi-directional lighting on HSTs

Postby Bufferstop » Thu Jul 12, 2018 6:09 pm

The old UFO lamps are a useful strip for spares item, as well as the mares tail, you get a wall wart transformer usually 12v or 24v, a two pin lamp base, dichoric halogen lamp, low voltage AC synchronous motor, some LEDs, a connector that matches the transformer, and possibly a dish for a turntable well, (depends on precise design).
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Re: Bi-directional lighting on HSTs

Postby Peterm » Fri Jul 13, 2018 1:39 am

If you put the positive to the centre leg and then a negative to either leg, that colour will light up. If the direction is changed so that the decoder switches off the function output for that leg and switches on the FO for the other leg, the other colour will light up.
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Re: Bi-directional lighting on HSTs

Postby End2end » Fri Jul 13, 2018 1:51 am

Ahh I see. That makes sense to me for one LED. I take it the other LED just spurs off the 3 wires using the same wiring technique.

I think the Black cat ones are definatly tempting for ease of fitting if nothing else.

Peterm wrote:Yes. A three leg led with the common positive being the middle one. Each leg having it's own appropriate value resistor.

Just to ask, what would these be? 1KOHm on each of the 3 LED legs?
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Re: Bi-directional lighting on HSTs

Postby RAFHAAA96 » Fri Jul 13, 2018 8:09 am

Starting from scratch...
A two legged bi-colour led achieves different colours by swapping the polarity of the legs, i.e + to one leg and - to the other gets you say white light, reverse the connections and you get a red light. As stated above applying AC gets you both colours, so if it was red/green used in a signal led you would get yellow.

For DCC if using three-legged bi-colour leds they must be common anode (centre leg). The + always sits on the centre leg and switching on each - leg gets you each colour. Switching on both - legs again gets you a yellow (from red/green).

The above has ignored mention of resistors which must be installed to limit current versus led forward voltage to protect the leds. To get a balanced common colour you must fit the correct value resistors or the dominant colour will overpower the lesser colour (i.e. red/green with the same value resistors will still show red). From this you can see the resistors go in the negative legs.

One thing to remember is the power car is pointy bit facing forward, but the trailer car in train runs pointy bit facing aft so in the trailer car you would cross connect the yellow and white wires to get the logic correct. This article tells how I installed three-legged common anode red/white directional leds into my Class 395. The underlying principles apply to your HST.

http://myweb.cytanet.com.cy/honnor/page17.html

Edit: the article has a typo - talking to positive anode leds when it should say common anode leds.

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Re: Bi-directional lighting on HSTs

Postby End2end » Fri Jul 13, 2018 10:30 am

Thanks for that Rob. :)
Wouldn't just programming the decoder to show backward running be easier than swapping the wires over though?
Just to keep everything as NMRA standard.
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Re: Bi-directional lighting on HSTs

Postby RAFHAAA96 » Fri Jul 13, 2018 7:09 pm

End2end wrote:Thanks for that Rob. :)
Wouldn't just programming the decoder to show backward running be easier than swapping the wires over though?
Just to keep everything as NMRA standard.
Thanks
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Try it...
If you have a breadboard you can mock these things up and fiddle around with settings and so on before committing to wiring the locos.
My breadboard is 2000 miles away at present so I can’t help there.
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Re: Bi-directional lighting on HSTs

Postby Peterm » Sat Jul 14, 2018 1:05 am

RAFHAAA96 wrote:Starting from scratch...
A two legged bi-colour led achieves different colours by swapping the polarity of the legs, i.e + to one leg and - to the other gets you say white light, reverse the connections and you get a red light. As stated above applying AC gets you both colours, so if it was red/green used in a signal led you would get yellow.

For DCC if using three-legged bi-colour leds they must be common anode (centre leg). The + always sits on the centre leg and switching on each - leg gets you each colour. Switching on both - legs again gets you a yellow (from red/green).

The above has ignored mention of resistors which must be installed to limit current versus led forward voltage to protect the leds. To get a balanced common colour you must fit the correct value resistors or the dominant colour will overpower the lesser colour (i.e. red/green with the same value resistors will still show red). From this you can see the resistors go in the negative legs.

One thing to remember is the power car is pointy bit facing forward, but the trailer car in train runs pointy bit facing aft so in the trailer car you would cross connect the yellow and white wires to get the logic correct. This article tells how I installed three-legged common anode red/white directional leds into my Class 395. The


underlying principles apply to your HST.

http://myweb.cytanet.com.cy/honnor/page17.html

Edit: the article has a typo - talking to positive anode leds when it should say common anode leds.

Rob

Rob, I did mention the resistors needed "Peterm wrote:
Yes. A three leg led with the common positive being the middle one. Each leg having it's own appropriate value resistor."
:)
Pete.

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Re: Bi-directional lighting on HSTs

Postby RAFHAAA96 » Sat Jul 14, 2018 8:21 am

Peterm
I was referring to my own post not talking to resistors, not yours. I ignored resistors to (hopefully) make my explanation as simple as possible, but thought I should mention that in case anyone came back about it.
Sorry for any confusion.
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Re: Bi-directional lighting on HSTs

Postby Peterm » Sun Jul 15, 2018 3:55 am

Confused? wot me? What was the question?
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Re: Bi-directional lighting on HSTs

Postby End2end » Sun Jul 15, 2018 8:46 pm

Peterm wrote:Confused? wot me? What was the question?
:lol:
What would the resistors value be on a tri-legged / Bi-colour LED? 1KOHm on each of the 3 LED legs?

Just to keep you all upto speed. I won and am awaiting the arrival of a black roofed HST power / dummy car set. :D
I'll have it on Friday.

I'm leaning towards theose black cat circuits. They will make life a lot easier and reasonable too at under £12 for the pair with both white and red SMD's on.
I'm not sure but I may even have a spare decoder which I can use to drive the train once I've wired it up for DCC.
I need to have a look as to what's available for function only decoders but if it's as simple as bridging the diode (for a dummy motor load) I may get a normal decoder if it's cheaper.
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Re: Bi-directional lighting on HSTs

Postby Peterm » Mon Jul 16, 2018 1:32 am

Sorry. My last post was meant to be a quote on RAFHAAA96's post.

Anyway, the values will be different for red and green. Start with 1K and probably go higher from there. It's really a matter of personal preference as to how bright you want the lights to be.

If you use a normal decoder for lighting, put a 100Ω resistor across the orange and grey wires so it thinks there's a motor connected.
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Re: Bi-directional lighting on HSTs

Postby RAFHAAA96 » Mon Jul 16, 2018 8:56 am

If you want to make yellow from a red/green led then you need to correctly balance the forward voltage and current of each colour (see led spec sheet) and this will determine the required resistor values. There are on line calculators for this.

For loco use you can generally get away with the same resistor value on the red and white legs and likely put another on the positive leg to further safeguard the decoder against overloading of the function output (again see the led spec sheet). If the lights are too bright then increase the resistor value on that colour leg.

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Re: Bi-directional lighting on HSTs

Postby End2end » Mon Jul 16, 2018 10:13 am

Peterm wrote:Sorry. My last post was meant to be a quote on RAFHAAA96's post.
Anyway, the values will be different for red and green. Start with 1K and probably go higher from there. It's really a matter of personal preference as to how bright you want the lights to be.

Er... don't you mean red and WHITE. :? :lol: I have 1K resistors in stock but any other rating will need to be bought in.

Peterm wrote:If you use a normal decoder for lighting, put a 100Ω resistor across the orange and grey wires so it thinks there's a motor connected.

Excellent. Thanks for that nugget of information Pete. :)

RAFHAAA96 wrote:If you want to make yellow from a red/green led then you need to correctly balance the forward voltage and current of each colour (see led spec sheet) and this will determine the required resistor values. There are on line calculators for this.

No, that should be ok Rob as I would have used red/white LED's anyway rather than using 2 different colours to make up a different colour.

RAFHAAA96 wrote:For loco use you can generally get away with the same resistor value on the red and white legs and likely put another on the positive leg to further safeguard the decoder against overloading of the function output (again see the led spec sheet). If the lights are too bright then increase the resistor value on that colour leg.Rob

Yes I think I would have added 3 to be on the safe side. One reisitor on each LED leg "futureproofing" it as best I could.
Thanks
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Re: Bi-directional lighting on HSTs

Postby RAFHAAA96 » Mon Jul 16, 2018 2:27 pm

Going back to the breadboard method...

If you use a couple of vari-resistors to set up and ‘manage’ your combined colours its a simple matter to read the vari-set values of those resistors and look for the nearest standard value.

The reason I generally use an extra resistor in the ‘blue’ leg is because I found an Express Models lighting kit was overloading my TTS decoder function output (3 front and 2 rear leds lit directionally), which is quite low at 100mA per channel and unlike the motor circuit is not self protecting.

Anyhow its down to how bright you want your lights, mine were far too bright.
Rob
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