# "Rock Light" 4x4 Project - Need Help from the Experts



## ozzy702 (Apr 25, 2011)

I'm a newb when it comes to electrical and modding things. I found this forum when I was looking for a decent flashlight and after purchasing several fenix and 4sevens lights (all I can afford ) I'm convinced you guys know what you're talking about, especially after I build two P7 maglites using instructions I found here and they work great. 

I'm into offroading and want to build some "Rock Lights" which are lights that light up the ground below and around the truck so you can see well at night. 








I will have access to a mill and lathe soon so the body and construction of the light isn't a problem. My main concern is, which emitters would you recommend and how do I adapt them to the 12V system on my truck? I just want to use one switch to light up all 6-8 pods like the one pictured above. 

Obviously the more light the better but I'd also like more of a flood type beam (I'm assuming that the two factors involved in that are both the emitter itself and then a diffusing lens or something along those lines.

So to sum it up I need your help with the following. 

1) What emitters to order? I want at least 200 lumens per pod but also want more of a flood beam than a focused spot. I'd be fine with even using P7's like these or any others that you recommend. 

http://www.dealextreme.com/p/ssc-p7-c-bin-led-emitter-with-21mm-heat-sink-base-3-6v-3-7v-12721

Edit: I'd also be up for possibly using multiple P4's or something like that if you think it's a better idea for flood coverage. It would be more work but doable. 

2) How do I drive the lights using 12V? I want to use one switch for 6 to 8 different lights but don't understand how to bump it down to the proper voltage per light.


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## Codiak (Apr 25, 2011)

Your design requirements leave you a lot of flexablity, rarely seen here ;-)

Size... NA 
Heat Disapation... NA (Heat sink can be larger, and 200 lumens is low build up anyway)
Power... NA (Altenator!)
Focusibility... NA 

For LEDs vs the price list on that P7 I'd suggest saving a few bucks and going with Cree XM-L's they can be sourced in the US from ledsupply.com for 11$ a pop.

As for drivers for you application they may be overkill take a look at taskled.com. 

You can always wire 3 parallel loops from the power through a single switch on dash, each loop powering a driver and each driver tied to 3 LEDs.


If you want flood... don't use any reflector... just let the LED Shine.


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## ozzy702 (Apr 25, 2011)

Codiak said:


> Your design requirements leave you a lot of flexablity, rarely seen here ;-)
> 
> Size... NA
> Heat Disapation... NA (Heat sink can be larger, and 200 lumens is low build up anyway)
> ...


 
Thanks for the info. I'll check out the Cree XM-L's. So you would suggest using drivers to drop the voltage from 12v to whatever the recommended LED specs are? I'm looking for the cheapest way to do it too since I'm a broke college student. Are there resistors or anything else that's cheap out there that could drop the 12v down as well but also handle the amps needed to run 8+ individual lights?

Edit: Any idea of actual light output on the Cree XM-L's vs the P7? I know the P7 is rated at up to 900 lumens but doesn't actually hit that high a mark.


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## Codiak (Apr 25, 2011)

I'm quite sure you can do it without drivers, I'm sure someone can/will post a more cost effect wiring solution.


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## ozzy702 (Apr 25, 2011)

Thank for the help Codiak. That cree XM-L looks like it would work perfectly! Does anyone else have any input regarding wiring everything up. I want to make sure I'm driving the LED's at their maximum safe rating but not over-driving them.


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## JohnR66 (Apr 25, 2011)

Check out Bridgelux emitters here:
http://www.bridgelux.com/products/ledarray_productselectionguide.html
The ones you want are the 400+ lumen emitters that come on the hexagan shaped board. You can get them for as low as $7 a pop for cool white or still under $10 for neutral or warm white at Digikey. They are arrays and the voltage requirement is 9.6 so it is easy to integrate them into the 12 volt automotive system. They can operate fine at around 400ma, so given that you'll need to drop around 4 volts, a 2 watt 10 Ohm resistor is all you need. This would be about as low cost as you can get.


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## ozzy702 (Apr 25, 2011)

JohnR66 said:


> Check out Bridgelux emitters here:
> http://www.bridgelux.com/products/ledarray_productselectionguide.html
> The ones you want are the 400+ lumen emitters that come on the hexagan shaped board. You can get them for as low as $7 a pop for cool white or still under $10 for neutral or warm white at Digikey. They are arrays and the voltage requirement is 9.6 so it is easy to integrate them into the 12 volt automotive system. They can operate fine at around 400ma, so given that you'll need to drop around 4 volts, a 2 watt 10 Ohm resistor is all you need. This would be about as low cost as you can get.


 
Ok, so power to a switch, then from the switch to one 2 watt 10 Ohm resister and then to the LED pod? Would each LED need a resistor or would one resistor be ok for several (6to8)? Sorry, I really need to learn more about electricity, I understand some but not nearly enough. Give me a welder and some steel and I'll build you a hi-tech suspension for a 4x4 or race car but I'm still trying to pick up the electrical. I really appreciate all your help.


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## JohnR66 (Apr 26, 2011)

That is correct. Each pod needs its own resistor, but they are cheap. If coming from a non fused source, add a fuse before the switch. I'd do it anyway. A 4 or 5 amp fuse would be fine. Don't forget that power LEDs need heatsinked. Use thermal epoxy to mount each hexagon (star) to an aluminum heatsink. The heatsink in turn should be mounted to the vehicle's metal chassis for further dissipation (like in your picture).


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## Codiak (Apr 26, 2011)

JohnR66 said:


> Use thermal epoxy to mount each hexagon (star) to an aluminum heatsink.



Use screws too, while the epoxies are good given the environmental stresses you might as well over engineer.

When you mount to the chassis, sand the spot and use thermal epoxy or thermal paste between the heatsink and the chassis as well.


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## Capt. Nemo (Apr 26, 2011)

I see your rig of choice is an XJ - having owned 6 and wheeled the Rubicon for over ten years and the Hammers, for your purposes - the cheaper the better. I've used rock lights extensively, but they have always been standard generic automotive type incandescent lights from the local auto parts store. I figure something like those have a greater risk of being damaged, and i didn't want to spend a lot of time/money on something worrying about them. If you're wheeling trails like Fordyce, there's water crossings to consider also.

Check these out, as well as the lights on the bottom of the page: 
http://www.polyperformance.com/shop/Trail-Gear-Durable-Waterproof-Silicon-LED-Strips-p-21126.html 

There's also these:
http://www.polyperformance.com/shop/Vision-X-LED-Pod-p-2499.html

There are a lot of inexpensive options without spending a lot of time and money on something that you're going to worry about. Spend the money on lockers, winch, suspension, etc


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## purduephotog (Apr 26, 2011)

JohnR66 said:


> Check out Bridgelux emitters here:
> http://www.bridgelux.com/products/ledarray_productselectionguide.html
> The ones you want are the 400+ lumen emitters that come on the hexagan shaped board. You can get them for as low as $7 a pop for cool white or still under $10 for neutral or warm white at Digikey. They are arrays and the voltage requirement is 9.6 so it is easy to integrate them into the 12 volt automotive system. They can operate fine at around 400ma, so given that you'll need to drop around 4 volts, a 2 watt 10 Ohm resistor is all you need. This would be about as low cost as you can get.


 
I'd have to agree here. You've got a couple of simple requirements here- you could go with some bridgelux emitters and a buckpuck or bucktoot (or boost buck) from ledsupply. Picking a pair or more of bridgelux emitters from newark and that's as simple as you've got- cut off a chunk of aluminum, tap two 4-40 holes, mount the bridgelux. If you use buck toots, you could get 1 for each puck (10$) for regulated and get quite a bit of flood light.

That said, simple and cheap may not be compatible... the other option is getting some really small dies on stars and soldering them. That's pretty simple too... but if I were to go down this road and had unlimited amps, I'd look at a boostpuck and a 350ma bridgelux die.


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## ozzy702 (Apr 26, 2011)

Capt. Nemo said:


> I see your rig of choice is an XJ - having owned 6 and wheeled the Rubicon for over ten years and the Hammers, for your purposes - the cheaper the better. I've used rock lights extensively, but they have always been standard generic automotive type incandescent lights from the local auto parts store. I figure something like those have a greater risk of being damaged, and i didn't want to spend a lot of time/money on something worrying about them. If you're wheeling trails like Fordyce, there's water crossings to consider also.
> 
> Check these out, as well as the lights on the bottom of the page:
> http://www.polyperformance.com/shop/Trail-Gear-Durable-Waterproof-Silicon-LED-Strips-p-21126.html
> ...


 
Thanks for the Info. My rig of choice is actually a 93' Toy pickup with a solid axle conversion. Already have the winch, lockers, gears, t-cases etc. :huh: My buddies run XJ's though and they work great.

The problem with both the products listed above is the light output really isn't that impressive. I've been on the trail with people with Vision-X setups and also the light strings and while they get the job done I'd like more. The standard ncandescent lights (I have several tractor lights on my truck right now) just take up too much room and suck down too much power for my taste but on the other hand they do put out a good deal of light.

Will it cost me the same or more than some of the prebuilt setups out there? Yep, but it will also be 4X brighter and I can have the pride of saying I built them myself. 

So the bridgelux emitters are decent? I've never heard of them before, only Cree and other a handful of other brands. Yes I plan on using a thermal paste of some type. In the past I've used a few different products. Anyone recommend one that's extremely sturdy? I'll either use an aluminum machined chunk or possibly a clear plastic pot with a heat sink attached to the back. Just depends on if my buddy gets his mill and lathe hooked up sometime soon.

Edit: How do these guys look? http://www.newark.com/jsp/search/productdetail.jsp?SKU=45P5615&CMP=AFC-OP&CMP=AFC-OP From what I can tell I should be able to run them at 1000ma for over 500 lumens.


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## ozzy702 (May 3, 2011)

Unfortunately my buddies motor on his lathe is not working so I'll have to do something a little less bling. I'm thinking some 2" x 1/2" thick aluminum flat bar. Then I could screw it into the body of the vehicle, hopefully drawing more heat out of the heat sink. 

Would that be enough for the bridgelux led's linked above? How about if they were overdriven at 1amp? I figure it should be, the heatsink I used for my P7 maglite is a whole lot smaller than what I'm thinking.


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