My first LEDs project (Cargo Area light change)

[Pescakl1]

After playing with some Plug and Play LEDs, I decided to do my own for better results (and that is less expensive too).Since I am still not sure I will keep the car, the only projects done on this car for now has to be Plug and Play (so headlights and tail lights retrofits are on hold for now).The first project was to change the cargo area light.Thanks to many members of a specialized forum, I learnt a lot on LED chips, schematics and control.At first, I did not even know how to solder (I did some soldering at school but not this type), so my wife had to teach me... and let me have some free time to do this.

Now, here is the challenge and the competitors:The space available is about 2cm x 3cm, so I could only fit 6 white Cree P4 LEDs on this small board.They are voltage regulated at 12V and each in series with a 33 ohms resistor (so they run at about 30mA, their nominal rating). I purchased a specific bin code, so they suppose to be in the 6-6500 K range).This is to compare with the OEM halogen bulb and a 9 LEDs PnP bulb I bought on Ebay.

Here is a shot of the back of the array, but the voltage regulator hides almost everything. I designed the array to install a blocking diode on the negative connection, but when I dremelled the board, I cut it too small, eliminating one row of holes, so I did not have anymore space to install it. I even had to change the wiring routing as the little green bridge was not planned at first.

First is a light output comparison between the three competitors. The pictures are taken with exactly the same setting with the camera in manual mode and the white balance predetermined (about 5600K).

It is easy to see that the homemade LEDs are more powerful than the other two. The only gain of the PnP LEDs over the OEM is its white light output (a little bit, too much for me, on the cool side as it looks like about 7-8000 K) compare to the yellow halogen (3200 K).

Now, the most important, the light output in situation: Same type of comparison as previously, but the bulbs are installed on the car, cargo door opened about one third (blocked by the garage door), the only other available light being the garage lighting.You can see that the PnP LEDs are far from being interesting options when you purchase them to get good light outputs as the light is probably too focused compare to the halogen bulb (and there is no reflector in this comparison).The homemade LEDs beats the others hands down.

Here is a shot of the homemade LEDs installed in the housing.If I knew for sure that I keep the car, I would have try to take advantage of the free space around the array to install even more LEDs, but for now, I am quite pleased with what I did.
Modified by Pescakl1 at 1:39 PM 7/28/2009

[Leo2005]

nice mod. i like it.

[Elton Noway]

After playing with some Plug and Play LEDs, I decided to do my own for better results (and that is less expensive too).

At first, I did not even know how to solder (I did some soldering at school but not this type), so my wife had to teach me... and let me have some free time to do this.

Wow! For someone who claims they didn't even know how to solder... designing and building your own LED array is an impressive undertaking. Very nice.

How about posting a complete component list. i.e., part numbers, where you purchased the LEDs and Reg from etc. Even a snapshot of your rough schematic if you have one.

BTW... I like your nail polish (okay... so I know your wife was probably the model)

[Pescakl1]

Wow! For someone who claims they didn't even know how to solder... designing and building your own LED array is an impressive undertaking. Very nice.

It seems I learn fast, skill that I acquired to survive my professional life (my resume is three pages long now ).I knew how to solder from school, but strangely not with these tools. So I did not need too much practice to do what I need, using my wife's tools.In general, when you are interested in something, you learn fast and I learn a lot by reading forums of others' projects, and most importantly for me, seeing them.

How about posting a complete component list. i.e., part numbers, where you purchased the LEDs and Reg from etc. Even a snapshot of your rough schematic if you have one.

I can do that, no problem. I will have to search my papers at home for the part numbers, so I will post the specifics later.Most of the parts I bought come from Newark as they are cheaper for us Canadians. You can also check at Digi-Key. Radioshack has also some electronic stuff but they are usually more expensive, but for solder materials and boards, it is a good place.Today, I will draw on the computer the design of the array. In fact, I will draw the two, the designed one and the one I ended with.

BTW... I like your nail polish (okay... so I know your wife was probably the model)

In fact, it is one of my step daughter, always intrigued of what I am doing in the garage.Mines are the big ones on the last pics (and with four girls at home, I may end up with some polish on my nails, you never know ).

[takeshi]

Nice work! If anyone doesn't want to take the do-it-yourself approach I highly recommend these:http://nigel-jdmparts.com/LED.html

I haven't used them in the Rogue but I do have 4 of them installed in my other car. There are other retailers and other brands of these "LED board lights" as well.

[Pescakl1]

For those of you interested, here are the schematics.Feel free to ask for any clarification.
Modified by Pescakl1 at 8:59 AM 7/22/2009

[SenorPayne7]

very nice! can you tell me how you took the light off the car?

[philipa_240sx]

Pescakl,

Your wiring diagram does not clearly show the current limiting resistor.

Very good job though. It's great to see someone experimenting!

Your design is very simple, but being constant voltage based you may not be getting the most light from them. You may want to try a dedicated LED driver which provides a constant current for maximum brightness. Some constant current drive chip also have very low power consumption so you won't have the heating issues you may experience using linear voltage regulators.

[Pescakl1]

very nice! can you tell me how you took the light off the car?

For this one, it is quite easy:- Open the trunk,- Put your fingers on the right side of the light when looking at the inside side of the trunk (side facing the outside of the car).- Pull to the inside of the car and then towards you.

As you can see on the picture of the housing, there are only two tabs holding the light in place and four small tab for guiding purpose.

[Pescakl1]

Pescakl,

Your wiring diagram does not clearly show the current limiting resistor.

Very good job though. It's great to see someone experimenting!

Change done.I thought that with the picture, it was quite obvious so I did not indicate them.

Your design is very simple, but being constant voltage based you may not be getting the most light from them.

Quite the contrary:Without voltage regulation, you have to choose the resistor value for about 14V to be on the safe side (voltage in a car moves from about 12V (engine not running) to 14.4V (engine running) depending of the state of your alternator, meaning these values will change with time).By doing this, when you car is at about 12.6V (engine not running), your LEDs will be under driven and you will have less light.If you design your array for 12V without voltage regulator, you will overdrive your LEDs when the car is running and kill them prematurely (that is what happens to bad designed PnP LEDs).

With a voltage regulator, you know that for sure, your voltage is and will stay at 12V. With the Ohm law, you can precisely calculate your resistor to not overdrive your LEDs but at the same time use them at their nominal value, getting the most light from them.

You may want to try a dedicated LED driver which provides a constant current for maximum brightness. Some constant current drive chip also have very low power consumption so you won't have the heating issues you may experience using linear voltage regulators.

Constant current drivers are generally used for high power LEDs (0.5W and more).It is more complicated to work with them as the biggest problem is the heat generated by these little LEDs (the other one being the soldering as they need as specific designed board). So you spend more time designing a way to pull out the heat from the LEDs than designing the electrical circuit.

The ones I use here, are usually denominated as Superflux LEDs (4 legs LEDs), pulling less than 100mA, therefore not needing heatsinking to work properly.For these types of LEDs, the best to design a array is to voltage regulate them as it is simpler to design (parallel series type of design) than to current regulate them, giving the same result (thanks again to the ohm law).From what I understand, with a current regulated driver, you have to put all your LEDs in parallel and not in parallel-series. Since voltage is limited (about 12V), you will be limited in the number of LEDs you can install (each LED takes about 3.5V, so about 3 to 4 LEDs). It is interesting for high power LEDs as you don't need a lot to get the output you want.With a voltage regulation, you can install LEDs in series of 3 for about 10.5V, giving to evacuate only about 1.5V in heat, and since these drivers can pull up to 2A, you can regulate about 80 LEDs with only one regulator which is quite interesting when you retrofit tail lights for example.

Is all this understandable? Did I make a mistake ( I am quite still a newbie in this)?

[philipa_240sx]

Pescakl,

I did not mean to point fault at your design, I was merely suggesting another alternative. Your voltage regulator design is probably the simplest way to get the job done.

My background is Electronics Engineering Technology, so I am keenly interested in this stuff.

[Pescakl1]

How about posting a complete component list. i.e., part numbers, where you purchased the LEDs and Reg from etc.

The problem with posting all this information is that it can be inaccurate for someone wanted to do only a small project.Me, I want to change every light in my car, interior and exterior, so I bought about 630 LEDs (300 ambers, 300 reds, and about 30 white and need to buy more of the whites), a lot of electronic parts (resistors, capacitors, blocking diodes, bridge rectifier, timer, etc...) to build PWM (Pulse Width Modulation) to get dual brightness with the same LEDS, and a lot of experiment phenolic boards to install the LEDs on.I think I bought for about 300 $CAD in parts.By buying in big chunks, I got better prices than if you buy just one small board, two resistors and six LEDs.

So if you just want to experiment and do a small project, you better buy all your stuff at Radioshack, except the LEDs and the voltage regulator, which can be buy at either Newark, Mouser, or Digi-Key.

If you want to buy in bigger portion, here are the suppliers I found to be the cheapest:- Experimental phenolic boards: Futurlec. Large boards are only $2.90 compare to about $7 at Radioshack (PN: EXPBRDLGPHEN), shipping is about $4. Shipping is quite slow, so order in advance.

- Electronic parts: Newark. Not that easy to find the parts you want as they have tons and tons of parts (use their filter tool). Resistors are about $0.015 to $0.14 each when you have a box of mixed resistors for about $2-3 at Radioshack. PNs: Whatever the cheapest.

- LEDs: Newark or Digi-Key. Newark are cheaper (about $0.3 for amber or red, $0.6 for white) compare to Digi-Key ($0.8 for white), but the advantage of Digi-Key is that they sort the LEDs when they receive them so if you want a specific bin codes, they can provide you exactly what you want. That is not that important for red or amber, but for whites, LEDs are usually around 8000K (blueish white) but some are at about 6-6500K (really white), so if you are picky like me, that makes a difference. As for PNs, I can give you the one I have now but new and improved LEDs (more lumens for the same current used, better light temperature control) go on the market every day. The most important is to stay with established names, so order either Cree, Nichia or Lumiled. Me, I use Cree P4 LEDs and for the white, the PN is LP377FWH1.

- Voltage regulator: The top notch (the one used here) is the SHARP voltage regulator (PN: PQ05RD21J00H). It is a low drop voltage (max 0.5V compare to about 1.5V for a transistor) so it is what you want for LEDs used when the car is not running (car voltage at about 12.6V). I bought them from a member on another forum but you can find them at about $2 at Digi-Key.

If you need more specific, do not hesitate to ask.

[Pescakl1]

Pescakl,

I did not mean to point fault at your design, I was merely suggesting another alternative. Your voltage regulator design is probably the simplest way to get the job done.

My background is Electronics Engineering Technology, so I am keenly interested in this stuff.

Don't worry, I did not take it as an attack, therefore my question at the end.

I was guessing that it is your field of expertise, and since I am still learning, I am interested in your opinion and suggestions.

I based my answer on my research on the internet and specifically on a specialized forum. With Superflux LEDs, they only use this type of design (so there must be a reason: simple, less expensive, less complicated for newbies, etc...), and for high power LEDs (not yet in my field), they use current drivers... and that is basically where I get lost .

[Pescakl1]

Second step: the Dome light.

Here, I had more space to work, so I took advantage and put more LEDs, 18 in total.

With a different design, I was able to put the reversing diode that I couldn't on the cargo light, and a small capacitor between the positive and negative legs of the regulator to avoid flickering and problem with the dimming effect of the dome light.

The third design on paper was good enough to find space for everything, and in practice it works fine too.

I got some problem with the soldering this time as the tip was too hot and a little bit too big for this type of application.If I want to continue this hobby, I will have to invest in a more specialized tools, I think.

Here are the pics:

Some problem encountered: When I bought the LEDs at Digi-Key, I ordered a small quantity of different batches, so they delivered them in one tube. Then my toddler found them and mix them up, so on close look, you can see they are not from the same batch (not same color).