Need some LED education

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Just Lou

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Dec 25, 2005
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I was convinced by the BRAINS of the forum to use LED replacement bulbs in my TOAD signal lights for improved visibility (brightness).  I'm looking for a bulb that will essentially be in parallel with the incandescent bulbs already in the MH since I use the "extra bulb" method. 

I again, have more questions than answers.
  • If a LED bulb says it's a replacement for an 1157, does that mean I don't need any of the "load resistors" or "special flashers" every vendor want's to sell me?
  • Most on-line LED bulb vendors say to order the color (white, amber or red) matching the vehicle lens color.  Why wouldn't I want to use a white light behind a Red lens?  Why would red be best?
 
Good question, Lou.  Have been trying to wrap my brains around it...so far no luck. In this case no help from me is better than me trying to guess.
  Hope someone will have the REAL answer. 


 
Just Lou said:
I again, have more questions than answers.
  • If a LED bulb says it's a replacement for an 1157, does that mean I don't need any of the "load resistors" or "special flashers" every vendor want's to sell me?
  • Most on-line LED bulb vendors say to order the color (white, amber or red) matching the vehicle lens color.  Why wouldn't I want to use a white light behind a Red lens?  Why would red be best?

If the Led light is in the same circuit with conventional bulbs, no flasher or load resister is required.  If it is alone or there are all LEDs on a flashing circuit, you will probably need either a load resister or the new flasher.  The standard flasher is a heat device.  The switch inside heats a bar of material and the bar deflects deflects and closed the circuit.  The flasher works just like some thermostats.  You need the load resister or new flasher because the low current needed for the LEDs is not enough to heat the flasher switch.  The resister approach defeats the reason most want LEDs, low power.

If I recall correctly, my optics physics class was in 1958  :), the color of the lens allows the efficient passage of the corresponding light and thus less lumens are required from the colored light source as compared to a white source.  Hopefully some or the photographers will have the real story.

 
I ran into this site that shows the difference in LED colors with different colored lenses.  Makes sense to me.

The need for a resistor when used as a turn signal bulb is because the LED doesn't draw enough current to activate most flashers.  I would think if you have regular 1157 bulbs in parallel with the LEDs, the load of the 1157 would take care of that.  In my case, I have separate bulbs mounted inside the same light assembly as the Jeep's lights.  They do not use the Jeep wiring, but connect to the MH 7-pin plug.  The MH signal lights provide the load for the flasher, so I shouldn't have to do anything but insert the 1157 LED replacements.
 
I swapped all my interior 1156 bulbs with cheap LED bulbs.  This is the cheapest place on earth to get LED bulbs:  Miniinthebox.com .  You can replace every single interior bulb in your RV for less than $40.  They are tinted a little purple, but for me, it's well worth the sacrifice.  Now my battery isn't getting any drain, and more importantly, the lights don't heat the place up like an oven in the summer!
 
Molaker said:
I ran into this site that shows the difference in LED colors with different colored lenses.  Makes sense to me.

The need for a resistor when used as a turn signal bulb is because the LED doesn't draw enough current to activate most flashers.  I would think if you have regular 1157 bulbs in parallel with the LEDs, the load of the 1157 would take care of that.  In my case, I have separate bulbs mounted inside the same light assembly as the Jeep's lights.  They do not use the Jeep wiring, but connect to the MH 7-pin plug.  The MH signal lights provide the load for the flasher, so I shouldn't have to do anything but insert the 1157 LED replacements.
Thanks Tom,  all good info.  The red-on-red makes sense.

Your setup is identical to mine.  I'm hoping it works the way we are thinking.  I did fire off an e-mail to the folks in Ned's post so we will see.  thanks again.
 
If you are using the "extra bulb" method, the lights are actually operating on the motorhome circuit rather than the toad's light system, so no problem with the toad flasher. And your motorhome probably has enough incandescent bulbs on the turn signal circuit to keep the flasher happy.

I would use whatever color bulb the toad had in the same socket. If the light is designed to use a white bulb behind a red lens, why change?

As to an LED being brighter or more visible than an incandescent, I am skeptical. It may or may not be, depending on the lumens of the bulb. Depending on  the number and type of leds used in the bulb, it could be dimmer, brighter,or the same as an incandescent 1157.
 
Gary RV Roamer said:
If you are using the "extra bulb" method, the lights are actually operating on the motorhome circuit rather than the toad's light system, so no problem with the toad flasher. And your motorhome probably has enough incandescent bulbs on the turn signal circuit to keep the flasher happy.
Gary, I understand all that.  The subject bulbs have NO connection to the toad so I wasn't worried about affecting anything in the toad.  My initial objective was just to increase the voltage reaching the bulbs to, hopefully, increase the brightness.  Everyone immediately proffered the LED idea as being a superior solution.
I would use whatever color bulb the toad had in the same socket. If the light is designed to use a white bulb behind a red lens, why change?
That information comes from the "web".  Many automobile LED vendors make this suggestion. :-\
As to an LED being brighter or more visible than an incandescent, I am skeptical. It may or may not be, depending on the lumens of the bulb. Depending on  the number and type of leds used in the bulb, it could be dimmer, brighter,or the same as an incandescent 1157.
Again, I understand the need to use a quality LED bulb.  But, I also feel the 1157 would suffice with a good solid 12v applied.

Maybe I'll just try to improve the existing wiring arrangement.
 
Lou, here is something you may not know.... On my old Bago I had 4 pin connector but it also had a diode block underneath the rear of the RV chassis.  That of course would lower the voltage a bit. So that would isolate the toad wiring from the RV wiring.  Why...Haven't got a clue.

Just trying to confuse you more but it is true in my case. I never had a brilliance problem on my Jeep toad with extra bulb in the rear lamps, The only thing that would now work was that extra, new-fangled stoplight at the top at the roof line.

  Sorry to give you more headaches..  ;)

 
carson said:
Lou, here is something you may not know.... On my old Bago I had 4 pin connector but it also had a diode block underneath the rear of the RV chassis.  That of course would lower the voltage a bit. So that would isolate the toad wiring from the RV wiring.  Why...Haven't got a clue.

Just trying to confuse you more but it is true in my case. I never had a brilliance problem on my Jeep toad with extra bulb in the rear lamps, The only thing that would now work was that extra, new-fangled stoplight at the top at the roof line.

  Sorry to give you more headaches..  ;)

Thanks Bud,  I suspect the Diode pack you saw at the rear of your motorhome may have been there to convert from separate bulbs (amber-turn and red-stop) in the MH to the single bulb concept used by the 4-wire plug.  ??? :-\

BTW - you can't confuse me more than I already am.

I probably need to do some additional experimenting with bulb placement and alignment inside the toad taillight housing and optimize the wiring as best I can.  The taillight lenses on the toad are a bit cloudy as well, so maybe I can make some improvement there.
 
If I understand what you're trying to do, run a set of tail/brake/turn lights, that are installed independent  from toad electrical system, and your problem is dim lights on toad. You may simply need a good ground from MH directly to toad tail lights. Grounding to toad may not work well.

Bill
 
driftless shifter said:
If I understand what you're trying to do, run a set of tail/brake/turn lights, that are installed independent  from toad electrical system, and your problem is dim lights on toad. You may simply need a good ground from MH directly to toad tail lights. Grounding to toad may not work well.

Bill

The ground is the one part that was easy to check and verify.  The ground is good.
 
My initial objective was just to increase the voltage reaching the bulbs to, hopefully, increase the brightness.  Everyone immediately proffered the LED idea as being a superior solution.

Using leds will reduce the amp load on the circuit, but that may or may not result in increased voltage. My guess is that it will not.

You can undoubtedly find an led bulb that will have more lumens (be brighter) than a standard 11157 incandescent. If bright is what you want, I would focus on the lumen ratings and forget the color and voltage questions.

I believe a typical 1157 bulb provides 400 lumens in the high output filament and 32 on the low output filament. I think the standard measurement is at 12.8v, but I'm not positive of any of those numbers (I haven't found an ANSI standard source for specs).
 
Gary RV Roamer said:
Using leds will reduce the amp load on the circuit, but that may or may not result in increased voltage. My guess is that it will not.
Gary, I think I may have confused you a bit by spreading this subject over two topics (threads).  My initial approach was to develop a method for decreasing the voltage drop from the front of the coach to the rear of the toad.  I solicited comment on a relay based circuit to do just that.

I never expected the use of LEDs to increase the voltage.  The use of LEDs was suggested as a way of getting more brightness (lumens) from the existing source voltage than the incandescent bulb was providing.  This approach would, of course, require the use of an LED capable of putting out maximum light at minimum voltage.  Some claim to operate efficiently on lower operating voltages than others.
 
Hey Lou, I don't think you ever published the actual voltage you find at the bulb. Both on the small and large filament. (Running and Stop light).  In other words what is the voltage drop you are experiencing.

  Just trying to keep you busy.
 
On our old WinnieBago I had about 10.5 volts at the tail lights and turn signals.  I assume that it was a bad ground but I could never find it.  I replaced the incandescent bulbs with LEDs and they were a world brighter.  I kept the LEDs when I traded the rig off, but they don't fit the new unit.  They were not 1157s but a wedge type bulb.
 
Just Lou said:
I was convinced by the BRAINS of the forum to use LED replacement bulbs in my TOAD signal lights for improved visibility (brightness).  I'm looking for a bulb that will essentially be in parallel with the incandescent bulbs already in the MH since I use the "extra bulb" method. 

Ok.  I have had mixed results with LEDs but perhaps they'll work for you.

If a LED bulb says it's a replacement for an 1157, does that mean I don't need any of the "load resistors" or "special flashers" every vendor want's to sell me?

To build upon what others have pointed out, you don't need either the load resistors or the special flashers, because you're leaving the existing T&T bulb on your motorhome in place.

Most on-line LED bulb vendors say to order the color (white, amber or red) matching the vehicle lens color.  Why wouldn't I want to use a white light behind a Red lens?  Why would red be best?

The red vehicle lens makes the light look red by filtering out and absorbing light of other colors.  White LEDs, like regular incandescent bulbs, produce a good deal of light of colors other than red, which the lens ends up throwing away.  Red LEDs only produce red light, so nothing gets thrown away by the lens,  and the result is brighter for the same number of watts.
 
On our old WinnieBago I had about 10.5 volts at the tail lights and turn signals.  I assume that it was a bad ground but I could never find it.

I'll bet if you measure the voltage with the LEDs in place, it'll be somewhere around 12 volts. 

LEDs use about 1/10th the current of regular light bulbs.  That means instead of losing 2-3 volts through the wiring, you're only losing 0.2 - 0.3 volts.  Even though the wiring (or bad ground) stays exactly the same.
 

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