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Old 15-04-2018, 07:15 PM   #1
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Default Resistor values with DCC.

Hi, i wanted to have local bi-colour LED signals by my turn outs & a mirror led on an indicator board i want to make so i can see that the points have changed.
Couple of questions:
1. Is it ok to run led's of the dcc power on the points switch which will come off
the rails.
2. If i have 2 bi-colour led's to work with each other "1 on a signal & 1 on a
indicator panel" both with three legs i would normally use 2 resisters for 1 of
these led's. Now for 2 led's to work together, should i use 4 resistors &
would the resister values be the same as though just using 1 led.

Thanks
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Old 16-04-2018, 08:37 AM   #2
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LEDs need a DC supply so best you provide a separate one. Plenty of cheap mains ones available. Bi colour LEDs only need a single resistor attached to the common lead.
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Old 16-04-2018, 09:01 AM   #3
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If you want your 3-legged leds to show yellow as in when a pair of points gets out of synch thus powering both colour (outer) legs then you need to fit a resistor in each outer leg and balance their values to get the yellow else the red side will swamp the green due to different colours having different forward voltages and currents.
Stick a variable resistor in circuit, get the balance right and measure the value, then pick the best standard value match.
Rob
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Old 16-04-2018, 09:17 AM   #4
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You can use the DCC with suitable diodes inserted and resistors. I would use a 1N4148 diode or a 1N4001 or 1N4002 or an ultra fast one such as UF4001 or UF4002 etc

The basic idea assuming electrofrog points are used is shown here. Link to LEDs on DCC Adding a second LED would be to repeat the same circuit with everything being doubled.

As suggest above by TDD, a regulated DC power source is IMO too by far the best option and ensures your LEDs are running at a constant voltage and their current is controlled by their series resistor(s). Start at 1K (1000 Ohm) and work up in Ohms if too bright. So then consider fitting the Gaugemaster GM500 to the motors feed wires and use its contacts to switch the LEDs and even the frog polarity.
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Old 16-04-2018, 09:28 AM   #5
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Quote:
Originally Posted by Teedoubleudee View Post
LEDs need a DC supply so best you provide a separate one. Plenty of cheap mains ones available. Bi colour LEDs only need a single resistor attached to the common lead.
Hi, the problem i have is the switch on the turnout/points takes the +- from the track to back feed the frog via the common. So the switch is being used unless i could use this DCC track voltage or some other way.
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Old 16-04-2018, 09:33 AM   #6
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Chris have you seen the reply to your other led thread?
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Old 16-04-2018, 10:41 AM   #7
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Quote:
Originally Posted by collectors View Post
Hi, the problem i have is the switch on the turnout/points takes the +- from the track to back feed the frog via the common. So the switch is being used unless i could use this DCC track voltage or some other way.
You can use the DCC power to drive LEDs by feeding the DCC output through a bridge rectifier. I have done this myself to light a "lamp" on the back of some brake vans - see attached circuit. The capacitor is added in this case to stop flickering when the wheel pickups lose contact when the wagon is moving, this shouldn't be necessary for what you want to achieve.
Attached Images
File Type: jpg DCC Lighting.jpg (27.5 KB, 12 views)
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Old 16-04-2018, 11:11 AM   #8
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Quote:
Originally Posted by collectors View Post
Hi, the problem i have is the switch on the turnout/points takes the +- from the track to back feed the frog via the common. So the switch is being used unless i could use this DCC track voltage or some other way.
See post #4 above and use the link.
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Old 16-04-2018, 12:19 PM   #9
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Quote:
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See post #4 above and use the link.
LOL: I just posted & you must of posted a few seconds before. That link has many good diagrams & should defiantly solve it.
Thanks
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Old 16-04-2018, 12:27 PM   #10
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Quote:
Originally Posted by Teedoubleudee View Post
You can use the DCC power to drive LEDs by feeding the DCC output through a bridge rectifier. I have done this myself to light a "lamp" on the back of some brake vans - see attached circuit. The capacitor is added in this case to stop flickering when the wheel pickups lose contact when the wagon is moving, this shouldn't be necessary for what you want to achieve.
Thanks for this. But i have read on a posts that using bridge rectifier's can create a volt drop "but this was for a volt/amp meter" & with having to use this at least 10 times on the tracks points, should i be worried? or was this just in the amp meter version/situation. Thanks

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