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Using LED lighting strips
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Electronics & Wiring
Using LED lighting strips
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Joined: Sep 25, 2010
posted on Jan 14, 2015 03:58 PM:
My Archive Category
Much has been written on these strips and many ways of using them. Here is my approach. This can also be viewed here,copy and paste the address if interested
Numerous LED kits are sold to replace incandescent bulbs in passenger cars. I use individual LEDs. For the conventional operator this is the only practical way to get constant voltage lighting at all throttle ranges. Here I posted several ways to use individual LEDs for cabooses,head lamps and passenger cars for both command and conventional.
LED lighting has many advantages. Properly circuited they should last a lifetime,especially if you are as old as me. They consume much less power freeing wattage to use to power engines on a loop. For general lighting make sure you buy warm white,not cool white unless you like the harshness of the older style LEDs.
Prewired LED strips are sold in reels and are relatively new. Please note I only recommend these for passenger car lighting for command only users who never run conventional. This is not a constant voltage circuit. For conventional variable voltage, use individual LEDs , circuits linked above. They are great for buildings and fixed voltage circuits. They are made wired in series of 3 with a resistor in series to each 3. For maximum brightness 12VDC input. They will run on AC current but it is not good practice. For hookup you can use #26 stranded wire,to keep your sanity use 3 colors. Each section has + and minus terminals that the wires can be soldered to. I used a Weller 100/140 gun but you can also us a small wattage pencil tipped gun. They can be cut to length as needed and have peel and stick adhesive backs and can be stuck to the underside of the passenger car roof. Pictured here cut for an 18 inch passenger cars,along with other common electrical components
Our transformers in O gauge generally put out AC current . DC can be made with an inexpensive bridge rectifier
For ease of installation , I selected the 4 amp version and a 220 uf capacitor. The capacitor is circuited across the + and - of the bridge in proper polarity. Space allowing up to 1000 uf can be used but 220 uf is sufficient to reduce flicker caused by intermittent roller contact. In passenger cars with interiors, the bridge,smaller capacitor and other components can usually be mounted under the floor. In other type cars also mounted to the floor. The 2 wires can be run up the opposite ends of the car connected to the LED strips. The capacitor also boost voltage by 41%, charging the pulsed current to peak. Here are some pics of the components used and the bridge and capacitor made up
18 VAC becomes 24 VDC with the bridge and cap. That is 12 volts more than the strips require. If hooked up to a single strip they would burn out. However if we cut the strip in equal halves and wire in series, the voltage will be divided equally between the 2 strips and each will receive 12 VDC and should burn at maximum brightness.
I hook it up to a TW and set the throttle at 18 volts,they burn pretty bright. In theory they should draw .08 amps. Each 3 LEDs should draw .02 amps at 12 volts, each 6 LEDs, .02 amps at 24 volts. Measured on my meter,they drew only .05 amps. The whole strip uses about 1 watt this way. A bit hard to photograph but here it is
Lighting is subjective. Shown so far should get the maximum intensity from the LEDs. If this is too bright,simply adding a resistor in series to one of the DC leads will dim them. Here it is with a 1000 ohm half watt resistor,this dims it quite a bit. After a bit of experimentation with resistor values, you can get the desired results to suit your tastes. From 470 to 10K ohm ones can be tried. They can be put in series or parallel to change values,so you don't need a large assortment. Another option from using the resistor is to wire the LED strips in series of 3 or 4,but they must be equal. I ran this and the other circuit a while,nothing got hot or even warm.
For DCS users,to reduce signal reflection install a small 22uf choke in series to one of the AC leads.
Lastly in the schematic you will notice a polyfuse installed between the rollers. This small thermal device opens around 1 amp. In a derailment,if one pickup roller is on the center,and one on the outer rail the small gauge wire connecting the rollers can burn up. This fuse can prevent that from happening.
Another method to protect this wire is to use 2 diodes instead of a full bridge rectifier. Current can not pass through opposing diodes. The downside of this is that it makes the capacitor less efficient,but the circuit uses so little current it works OK. Besides using 2 diodes,3 lead instead of 4 of the bridge rectifier can be used. This is the same as 2 diodes and easier to mount. Shown are 2 schematics alternating polarity draw. For a passenger car set wire half the cars one way and half the other. This will balance the load for the transformer instead of drawing all from one half of the sine wave. For those using light bulbs (which are often too bright in command) ,the bridge rectifier alone,wired this way will dim the light bulbs and current draw in half and protect the wire also.
Make sure you insulate leads shown so that they do not touch each other or the metal frame. I use silicone gasket compound and electrical shrink tubing. If you look through my blog of LED circuits linked in the first post,there are photos of these being used in wiring single LEDs. The DYI cost is maybe $2 to $3 per car. Once made they are as good or better than buying premade ones and you can customize lighting to your individual tastes and needs. LED reels can be purchased on Ebay and the rest from electrical supply houses. http://www.Mouser.com and http://www.Allelectronics.com are 2 I use. RadioShack is expensive,OK in a pinch if you just need a few things.
I posted this in response to some Emails I received from some OGR members who asked my opinion on lighting strips for cars.
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