Help needed with wiring leds

[richg1998]

Generally three LED's max for 12 volts with a 1k resistor.

Rich

[richg1998]

Trainmedic

 Hey all,

 I'm thinking about setting up my control panel so that when I flip a turnout there will be a line of leds going down the selected path on the panel. I'm confused about how to wire them thou.

 If I wire them in series does each led voltage get added together?

 In other words if I use four leds rated at 3.3v I need to supply13.4v to make the set work?

 If I put them in parallel would I then need to use a resistor on each led?

The parts I'm using are:

 Power supply rated at 12v or 5v (using PC supply)

 leds are 3.0-3.4v and 25ma.

I've tried to research this but it has me all messed up.Any help anyone can give would be appreciated.

Thanks

Trainmedic

 

 

It would help you to understand more about how LED's really work. They are current operated devices, not voltage operated.

http://www.members.optusnet.com.au/nswmn1/Lights_in_DCC.htm

http://www.wiringfordcc.com/gorhlite.htm

Rich

[richg1998]

Trainmedic

Thanks Lion.

Now can some tell me why my post are double spaced when they show up on the boards? 

Trainmedic

 

I copy my text to a Open Office document, spell check and copy and post back into the message. I post and sometimes have to edit the post by moving the cursor to the beginning of the first word. I hit the back space for each paragraph.

Once correct, re-post.

Works for me as I am a bad speller.

Rich

[CSX Robert]

gmpullman

...

Wired in series you might have one LED drawing slightly higher current than the rest and that one is going to burn noticably brighter.

...

No, current is constant in a series circuit.

[CSX Robert]

Trainmedic

...

 If I wire them in series does each led voltage get added together?

 

In other words if I use four leds rated at 3.3v I need to supply13.4v to make the set work?

 ...

If wired in series, then yes, the voltages add; however, you do not want the total voltage drop of the LEDs to be equal to the supply voltage, you want it to be LESS.

For example, if you are powering 3 volt LEDs with a 12 volt power supply, instead of having four LEDs in a series, use three or less and the appropraie resistor to limit the current to the desired level.

Trainmedic

...

If I put them in parallel would I then need to use a resistor on each led?

 ...

Yes, each parallel circuit would need it's own resistor.  You can mix things up if so desired.  For example, if you want to power five 3 volt LEDs off a 12 volt supply you could have three in one series circuit with one resistor and two in another series circuit with another sigle resistor and the two series circuits wired in parallel to each other.

[rrinker]

 I would think each LED would be controlled by the switch motor contacts or the toggle, so you wouldn;t have strings of them in series or parallel. As you went along the panel setting the toggles to line the route, the LEDs would change and light up along the route.

 With Tortoise motors, you can simply put the LEDs in series with the motor power - the wire that goes to either pin 1 or pin 8. Use either bicolor LEDs, or two ordinary LEDs connected back to back (anti-parallel - the + of one LED to the - of the other LED, and the - of the first LED to the + of the second LED). One will light when the switch is thrown one way, the other will light in the opposite position. If you use bicolor LEDs, you can have everything lit up, with the selected path in green and the blocked off tracks in red.

 As for double spacing, the text of each paragraph does not appear double spaced when I read your posts. Just the extra space between paragraphs. Which I don;t think is bad, it's easier to read.

                      --Randy

[Trainmedic]

Thanks Lion.

Now can some tell me why my post are double spaced when they show up on the boards? 

Trainmedic

[Trainmedic]

Thanks everyone!

 

gmpullman, I like the idea of the bi color leds. I'm using switch tender and Tortoise switch motors. I plan to change to all Tortoise at a later date.

 

texas zephyr, I'm not sure what a diode matrix is so I guess it must be the latter.

 

hon30 critter, I like your idea of using fiber optic cable. I watched a you tube video where a gentle man used the same idea to split an led to make two headlights on an engine. The side fiber optic cable sounds like a great idea I;I'll get some and try it out.

 

Thank you all for your input. I know just enough about electronics to make me dangerous so I had to check with some one who know what they're doing!

 

I'm going to upgrade my current control panel which is just toggle switches.

 

once again thank you,

 

Trainmedic

 

 

 

[BroadwayLion]

LEDs are not consumers of voltage: They do not significantly reduce the voltage of current flowing through them. That is why you can put your Tortoise machine in series with an LED. 

LION has rows of LEDs, mostly used for station lighting, but it is what you seem to have in mind, just a different application.

Each LED has its own resistor. The are wired between +12v DC on the long lead and through a resistor to Ground on the short lead. A 1/4 Watt, 1000 ohm resistor should work just fine with all LEDs, just toss out the formulas and the math books and do it my way. LION buys resistors by the thousand. An 1/8 Watt resistor would work just as well, but they are seven times more expensive, so stick with the 1/4 watt, you wallet will appreciate it. 

Yes, LEDs will light up in series without a resistor, and yes, you could wire four or five in series this way IF YOU ENJOY REBUILDING the project every two or three years. LEDs live virtually forever if you treat them well, they will bite you in the tail if you do not.

ROAR

[Mark R.]

To save yourself a bit of wiring, you could even use 12 volt LEDs that already have a built-in resistor ....

http://www.led-switch.com/12%20volt%20LED.htm

Mark.

[hon30critter]

Trainmedic:

I am going to suggest an alternative to using multiple LEDs that may have some potential. You could use a single light source with fibre optic cables to illuminate multiple points along the route.

There is also a type of fibre optic cable that emits light from the sides of the cable, not just the end. Here is an example:

http://www.ebay.com/itm/5m-2-3-4-5-6-8-14mm-Water-Resistant-Plastic-Side-Light-Glow-Fiber-Optic-Cable-EC-/331048713563?pt=US_Lighting_Parts_and_Accessories&var=&hash=item4d140a7d5b

I'm not sure how bright the light emitted from the sides of the cable is, but if it works it would work rather like a neon light. How cool would that be?

If you do use LEDs I would suggest wiring them in parallel with a resistor for each LED. It is a bit more work perhaps but the results will be both more consistant and more reliable. This is an example of LEDs wired in parallel, each with its own resistor. I used .010 phosphor bronze wire for the busses:

Just a few ideas to consider.

Dave

 

[Texas Zepher]

Trainmedic

I'm thinking about setting up my control panel so that when I flip a turnout there will be a line of leds going down the selected path on the panel. I'm confused about how to wire them thou.

How you wire them is going to depend on how the panel is wired.   Are you using a diode matrix to activate the line of leds?  Or do you really mean each turnout is going to have its own set of lights and they just happen to be in a line on the panel?

[gmpullman]

Hi Trainmedic

Your best bet is to have a resistor for each LED. Wired in series you might have one LED drawing slightly higher current than the rest and that one is going to burn noticably brighter. 1K resistors in bulk are less than a penny-a-piece. Some LED sellers throw them in with the deal.

I just use two bi-color LEDs at each diverging route so when one shows red the other will show green. Doesn't have the "wow" factor of a whole string of lights along the route but it gets the idea across.

For simplicity in wiring, you don't have to have each resistor AT the LED but you could make up a buss, say a short piece of solid copper wire OR a piece of PC breadboard and mount all your resistors there and just run the wire to the LED.

I wired about two dozen LEDs in a structure once and had all the resistors hidden in a first floor "room" so I just wired one side of the circuit to the resistors then fed each LED off this bundle. Just made it a little easier to insulate the wire at the LED.

The LEDs that trickle down to us modelers, the cheap ones on Ebay and found at surplus joints are ones that don't quite pass stringent QC tests so their current draw and brightness may vary slightly.

Are you going to use a motorized turnout (like a Tortoise?) they have auxiliary contacts that can be used for your purpose. otherwise you can use a DPDT switch and wire the LEDs to one side of the switch and the other to the turnout coil but you would also need a momentary contact pushbutton for the twin coil machine.

This chap uses a lot of route indicators... https://www.youtube.com/watch?v=sk-TV6Ptpy4

Ed

[Trainmedic]

Hey all,

 

I'm thinking about setting up my control panel so that when I flip a turnout there will be a line of leds going down the selected path on the panel. I'm confused about how to wire them thou.

 

If I wire them in series does each led voltage get added together?

 

In other words if I use four leds rated at 3.3v I need to supply13.4v to make the set work?

 

If I put them in parallel would I then need to use a resistor on each led?

 

The parts I'm using are:

 

Power supply rated at 12v or 5v (using PC supply)

 

leds are 3.0-3.4v and 25ma.

 

I've tried to research this but it has me all messed up.Any help anyone can give would be appreciated.

 

Thanks

 

Trainmedic