The resistor can be anywhere in the circuit. But..

If you put it on the + (long leg) lead of the LED, if the leads get crossed or grounded, you get a short circuit but then the resistor is still in the power feed line and won't let the circuit overheat, blow a fuse or damage the diode.

If the resistor is "downstream" from the LED and you get a short at the LED leads, you can have a straight short circuit, probably fry the diode and pop a fuse, since the resistor is being bypassed to ground.

They will work with resistor anywhere in the line. Just less likely to be damaged with resistor in the plus side, if they get shorted to ground.

My comment earlier about not worrying about polarity was AFTER the resistor is inline. Diodes never conduct backwards and once the resistor is there you can't damage anything with excessive forward current, they either light or they don't depending how they're connected.

Kevin, you're right about Radio Shack. No place to buy in bulk! I only bought 6 LEDs for under $10. Not a bad price for 4 aisle lights but no good for bulk pricing! (BTW, cool link for calculating resistor values!)

I used Radio Shack because they are local and quick. Ebay is always better for prices.

This has been a great thread!

quote:

My comment earlier about not worrying about polarity was AFTER the resistor is inline. Diodes never conduct backwards and once the resistor is there you can't damage anything with excessive forward current, they either light or they don't depending how they're connected.

Yes it is true that the LEDs will not light when connected in reverse, BUT-----

All diodes have a reverse voltage rating and if exceeded will blow. In the case of LEDs, the reverse voltage rating is 5 VDC, YES only 5 volts. If you have ever taken apart a commercial LED assembly with a single LED, you will find not only a resister but another diode, This prevents reverse voltage damage to the LED. Reverse voltage has a bit of time domain, a brief reversal probably will not damage them but sustained reverse voltage will definitely cause trouble either a blown LED or shortened life. A resister in the line does not necessarily protect a LED from reverse voltage damage. Reverse voltage damage is a voltage breakdown of the diode material, not an over current (heating) breakdown.

If you put 3 LEDs in series and using a single resister to limit the forward current, all LEDs will see the same current. Just add the forward conduction voltage of all LEDs in series and then calculate the resister needed for the desired operating current. Also if this LED string is reversed, the total reverse voltage now would be 15 volts. Less chance for damage (maybe none).

There are 12VDC lights with the standard Edison base - I have a couple 12VDC CFLs with that base, and both my boats had Edison sockets.

Thanks for the help rusty!

Kevin, I got my 3mm LEDs off Ebay too since I could buy them in bulk there. The ones I ordered from Illustra are for my overhead lights.

I’ll just let you guys know how they turn out and if they can really lessen the electric load once they arrive.

quote:

Originally posted by Kevin:

quote:

Originally posted by lesliemorris85:
Thanks for the help rusty!

Kevin, I got my 3mm LEDs off Ebay too since I could buy them in bulk there. The ones I ordered from Illustra are for my overhead lights.

I’ll just let you guys know how they turn out and if they can really lessen the electric load once they arrive.

Leslie,
You will indeed cut your lighting costs. What exactly did you order from Illustra for your overhead lights? I have not upgraded my overhead light fixtures yet, except for the one by the driver cabin. There is another nice post at: https://www.barthmobile.com/eve...263946677#4263946677

I have nice dome in this post and just put an LED bulb in it.

Be sure to calculate the proper resistor at ledcalc.com. I used 15 volts for the input current. May be Ed (mwrench) could let us know if that was a good choice. I wanted to error on the safe side. The gentleman at Radio Shack told me to use at least 13.8 volts for the input current. I have found you can be off. It will vary the brightness. I have not had any of them in use long enough to see if it affects the life of the LEDs

I got their recessed lights to replace my existing Cans. That project looks awesome, and an ingenious solution too. Maybe I’ll try that later on, though I’m not much of an electrician lol

Here's another take on led lighting.http://www.leevalley.com/en/hardware/page.aspx?p=70323&cat=3,43629,70322

Kevin
I recognize those lights! Looks really good and I appreciate all your help. Thanks for posting the photo. You should be receiving a letter from me sometime early next week.

Fred
1990 32' Regency, Cummins

Ain't this Barth stuff fun! Looks like we got another one infected with the LED virus.

I replaced the instrument lights with type 194 LED and the turn signal indicators and bright indicator with the individual 3mm type. Works great. Where does it all end? Maybe some blue undercarriage lights? Lighted exhaust pipe? Backlit toilet seat? Somebody help me...

Cruise through the forum archives, there is a lot of good stuff in there. For a real thrill, check out my old posts for many photos of naked Barth parts!

I was planning on going with a 18 SMD LED 1157 bulb. I'd rather not put in resistors as I plan on adding running/ side marker lights and if necessary license plate white light ? due to the tail/brake light lighting my plate and if its red I need another white light to be legal.

Good morning, Kevin;

I am also in the process of converting my inside coach lighting to the new LED lighting. I am not sure that my completed job will look at all like what is in your photograph. The outside lighting will be later.

The things that people have heard about the LED lighting conversion are probably true. I can say that when we converted our traffic signals to LED lighted displays, we also literally cut our intersection electrical power consumption by 90%, or to say it in another way, we dropped our electrical power consumption down to 10% of what it had been with the older 1950 Lumen or 165 Watt incandescent light bulbs in the larger 12 inch diameter traffic signals. While the LED conversion inserts were expensive, it really does turn out that we will save enough to pay for them. And now it really is practical to have a battery back-up for an intersection so that we can have the more important intersections continue to run for a few hours, which might get us through many power outages.

My own justification for the conversion is to drop the load on the motor home coach batteries. With the LED lighting, I can make the batteries feel much happier in the Spring and Fall nights and a lot of the Summer nights also. For a lot of things that we are doing in our motor homes, it does make the proposition of having photovoltaic solar panels on the roof of the motor home a useful and practical thing to do. I have the 80 Watt and 60 Watt solar panels in place now, and the chore of locating the smaller size panels that will fit into the spaces between the air conditioners, air vents, refrigerator vent shaft, TV antenna mast, and other things, has begun. My goal is about 350 Watts total capability. That will be enough to fully run the main radio when transmitting.

I will admit that this motor home has become an extended project, and there are many more things to be done with it.

Enjoy;

Ralph
Latte Land, Washington

SALE
https://www.superbrightleds.co...ers_day_2015_ma.html

Here's a video of hazards, one side incandescent, one side LED. Cross-posting because this seems to be the primary thread on the subject.

LED Hazards - Video

Thanks Quinn. I meant to do a side by side comparison like that but I forgot. Great argument for a conversion!

More on LED (Light Emitting Diodes) Some of my Airplane light sockets, the light sockets under the cabinets will accept a LED light bulb but, most will not accept a wider LED bulb. The problem is the LED light bulbs I purchased are too wide to fit inside the heat shield of the bulb socket. The wider bulb is shown here.

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The heat shield is what will not permit wider bulbs to seat in the base of my under cabinet lights.

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I have designed a fix for the members here. Take wire cutters and cut the inside heat shield like this.

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Use a strong needle nose pliers to tear and roll the aluminum heat shield out of the bulb holder, being careful not to damage the socket base.

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Shown here is the heat shield removed.

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Install a new low current draw multiple mini LED light bulb. This will save your house battery bank for longer off the grid living.

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There are LED lamps that are smaller in diameter and will fit in that application without cutting the reflector. Tom King turned me on to this.

The part number from Superbrightleds is 67-W15

There are a whole series (67) of this reduced diameter LED forward firing bulb.

I replaced all of mine in that same fixture with no issue. Plenty bright for its purpose.

HTH