LED christmas light

Hey B,

Look at the other thread you posted to.
I left your answer there.

David

Here's my Beep with LED head lights at night

Here the coal tower and switch tower.

Atlas station

Try to put a regular bulb in the phone booth and you'd have a blob of plastic from the heat. LED's don't put out any heat.

David

I make LED lighting for my Williams Pass. cars and use them in buildings also. Here's a few pictures. Pictures are not the best, I hope this helps. I make the single LED lights with a 1K resistor for buildings and engine lights. The Christmas lights are light blue in color, but you can get them in other colors (Yellow, red, green).

If lights are in series and the same current passes through every light,led strip lighting  disconnecting even one light will break the circuit and all lights will be off. If the lights are in parallel (each light forms its own current path between two wires) any and all lights can be disconnected (unscrewed, etc.) led strip lighting outdoor leaving on only the light or lights you choose. If you can not shut off individual lights you might run them through an opaque tube blocking all lights except the light you want (but be sure not to block heat, 12v led light bars especially on a Christmas tree!).

Of course, since you can buy a strip of 300 LED's mounted on sticky backed tape for $15 or less shipped, all the work for making your own seems somewhat pointless.  It's painless to light passenger cars with the light strips, and the cost for the LED's is less than $1 a car!

My thoughts exactly John.

The other thing that comes to mind is that its really not necessary to use rectified power.

I have used strip LED lights cut to length with only the appropriate resistor in series running off 18 VAC track power. Works great and eliminates the complexity of the rectifier circuit. Some may object to the slight flicker, but to my eyes it looks just fine.

My inspiration for this idea comes from upgrading a couple of K-Line steamers, where I noticed that the original marker LED's were connected directly to track power with a series 1K resistor. For simplicity I left them that way.

Rod

If you connect the LED's back-to-back, they'll protect each other.  OTOH, if you just connect an LED (or strip of LED's) to 18VAC, you will be exceeding the reverse voltage specification, which is 5-7 volts max for most LED's.  That's why my designs always have a diode to protect the LED's.  If you don't want the extra voltage of the diode, you can connect it across the LED's past the resistor and it'll simply dissipate the reverse polarity half of the cycle and result in no voltage drop to the LED's.  This is a consideration in conventional running, as you may not have voltage to waste.

I've lost some LED's to reverse voltage after some operational time, with diode protection, I've yet to lose one.

What prevents the led lights from shutting down on changing direction? They only work in one  direction.

Connecting LED's back-to-back allows each LED to light on half the AC cycle, the fact that it's a "diode" allows it to limit the voltage to the other LED to it's forward voltage, typically 1.5 for colored LEDs and 3.0 volts for white/blue LEDs.  It just eliminates the need for a protection diode.  If you need two LED's anyway, it saves a component and protects the LEDs from reverse bias.

The back-to-back I'm saying is anode to cathode so the LEDs are connected in opposite directions.

I get your point here John.

With the Optek LED strips you actually have 3 LED's in series with a 100 ohm resistor in each 2" section, so the total PRV limit of about 20 volts seems to be adequate. No fried LED's as yet.

I guess one could always hook the individual 3 LED sections up back to back so they protect each other. I had not thought of doing that.

I will maybe give that a try and see how it works. It's still a bunch simpler than a rectifier circuit.

Can you provide a drawing to expalin what you mean by "you can connect it across the LED's past the resistor and it'll simply dissipate the reverse polarity half of the cycle and result in no voltage drop to the LED's."

I am not quite getting that.

Rod

Here you go.  Note that on the half cycle that the LED doesn't light, the diode will conduct and keep it from seeing excess reverse voltage.  The back-to-back LED's work exactly the same way.

John;

OK I see it now.

Thanks for that explanation.

A picture is worth a thousand words.

The Best,

Rod

I want to replace the incandescents in my passenger cars with LEDs; where can I buy the LEDS (and other needed parts)you refer to in previous discussions? One 18V DCS, one track with conventional/variable transformer; any different needs for each?

       Wally

You can either do discrete LEDs, or use the strips.  I prefer the strips, a lot of the work is already done for you, and you get 300 LED's on a strip for around $15.  Here's an eBay sale of one of these sets for $13.28 including shipping: 5M SMD Warm White LED Strips.  You will most likely want slightly different configurations for cars that will run conventional and command vs. strictly command.

John,

I found that auction closed but a duplicate is on sale, with shipping included, for $12.74.  The link is:  http://www.ebay.com/itm/5M-3528-SMD-300-LED-Strip-Light-Warm-White-Home-RV-Car-/320916034888?pt=US_Light_Bulbs&hash=item4ab8161548

What do you think of these strips offered in lengths, with lead wires attached?  I looked for the lead wire attachments as a separate piece and so far have not found anything.  It must be available since the short strips are available ready made.  Here is a link for a typical section "10" LED light strip 15 piece 5050 SMD waterproof adhesive backing lead wire 25cm":  http://www.ebay.com/itm/10-LED-light-strip-15-piece-5050-SMD-waterproof-adhesive-backing-lead-wire-25cm-/261037224614?pt=LH_DefaultDomain_0&hash=item3cc707f2a6

To me it looks interesting.  Would the resistor simply be added to the strip leads?  This will make a nice project for all those passenger cars!

Thank you for the information...

Richard Snipes

4501 Safari in Jax, FL

John,

Thank you for the additional information.  I got captured of the NASA Edge live coverage from Hawaii on the Transit of Venus.  Interesting, amazing images and historical.

How do we protect the LED strips from excess voltage when running 18 volts to the track?  Is that where the limiting resistors come into play, to prevent overpowering the segments?  Obviously I need to do more reading but sure am intrigued by the possibilities of this lighting.

Richard Snipes

I use a constant current circuit to limit the current to the strips.  You'll need something or you'll cook the LED strips.  With this circuit, you can tune the current to get whatever light level you desire from the LEDs.