DIY LED Daytime Running Lights for the Miata NA

If you are like me, you've been noticing that a lot of new cars have really cool LED running lights - or DRLs (Daytime Running Lights). Well, they seemed like something that would look slick on a NA Miata. But could I do this myself? After some research, I realized it wasn't as easy as I first thought -

the parking lights/blinker assembly is a sealed unit - you can't just unscrew the lens and install a row of LEDs.
how to handle the blinker (directional indicator function)? Two rows of LEDs? Install another bulb for the blinker? Make the whole thing blink somehow?
What about the emergency function? The lights need to blink without the key on.

Well, I noodled on it for a while and came up with this idea.

Use single row of LEDs - as many as I could fit - that would span the entire parking lights/blinker assembly
find the brightest LEDs possible, but not surface mount - go old school to simplify assembly
for turn indicators, just blink the entire row using a relay hooked to the blinker circuit.
Tie another relay into the emergency flasher to activate the LEDs.

The plan was to run a new wire to the LEDs that was switched 12v - on when ever the key is on. This will allow the LEDs to light whenever the car is running, rather than just when the parking lights are on. Because we want the LEDs to blink when the indicator is on, we connect it to the Normally Closed (NC) position of a relay (so the LEDs are lit when the relay isn't) and to 12v ground to the other side. The wire that would normally go to the blinker goes to one side of the relay coil and the other side goes to ground. This allows the relay to activate when the blinker turns on, opening the circuit to the LEDs causing them to blink. The parking light lead isn't connected since the LEDs will be lit whenever the key is on anyway. So there are a total of 3 connections on each side. This all works fine when the key is on, but your emergency flashers need to work with the key off. I added another relay in from of the other two that switches the input to the flasher when it's activated.

Just to summarize, In driving mode, the LEDs are lit. When the blinker is activated, the relay closes and opens repeatedly causing the LED strip to blink. Since both LED strips are independent, while one is blinking, the other side stays lit. When you hit the emergency flasher, another relay kicks in to power the LEDs.

I ordered a kit of 100 super-bright LEDs and resistors from Parts Express. They also carried automotive grade 12v relays, so I ordered 3 of those. I bought a Perf Board (a perforated sheet of plastic for building electronics) at Radio Shack to assemble the LED strips.

With all of the parts in hand, and a wiring plan in my head, I began the work.

Step One- assemble the LED strips

Find the perf board and the LEDs and resistors. Insert the LEDs into the perf board making sure you get the polarity the same for all -doesn't matter which way at this point, but make sure the long lead or flat edge of the housing is all pointing the same way. You want the LEDs as close to each other as possible to get the most LEDs in the housing - more LEDs = more light. I ended up laying the LEDs in the pref board at an angle and got 39 in the row.

Next install the resistors beside the LEDs. Don't share the hole with the LED so that you can twist the leads together on the back side. This makes for a solid connection and holds both parts in the board. You can angle the resistors so that they are tight to the LEDs, or lay them out vertically (this just makes the resulting board bigger. If you angle the resistors you will run out of room at the end of the strip. I put half the resistors above the LEDs and half below to make the board as compact as possible. It doesn't matter which side of the LED the resistor is on.

Now flip the board over an twist the LED leads to the resistor leads making sure the the LEDs are polarized right (long lead on the same side). You can add another wire for the outside edge of the LEDs and resistors or simply flatten them into a long strip that will be soldered together later.

Trim the excess leads from the twisted connections and solder.

Apply solder to the bundle of leads or your new lead that runs along the outside edges.

This picture is actually from a couple of steps later,
but I wanted to show the twisted leads down the center
and the leads at the top and bottom soldered together.

Step Two - test the LED strips and fix any loose wires

Solder a couple one lead to the top leads of the strip and one to the lower. Make them longer than you need so you can test it. Find a 12v source to test with - I used a electric tire pump that has a 12v cigarette lighter output. Take note of which are the positive and negative wires and make sure every LED lights. If one is out, check the connections and resolder until they all light reliably. Do this for both strips/

Step Five - cut the strip to size
Your perfboard is probably too big to mount. We want to cut it down to something we can fit into the flicker housing. Mark the perfboard outside of the soldered area and give your self some extra room for mounting it to the wire retainers. Cut the excess.

Step Six - dissect the parking lights/blinker assembly

We only need the lens for our LED blinkers/DRLs. Pull the two parking/blinker lights from the car by removing the two screws on each and them pulling out the bulb/socket assembly from the back of each.

As you can see the lens is attached to the reflector with tabs on the plastic lenses and a gray adhesive filler.To deal with the tabs, we are going to cut the reflector side so that the tabs don't have anything to hold on to.I used a dremel to do this, but I'm sure there are other ways.

Next I removed the gray putty that glued the lens to the reflector. For this I used a spray solvent. It turned the hardened putty into a soft gooey mess...

And after some prying with a large standard screwdriver...

The lens came loose.

After some scraping with the screw driver and a razor blade, it came pretty clean.

Step Seven - trim the ends of the lenses

The lens interlock with the reflector where they mount to the car. I needed to be able to reach the mounting holes on either side, so this interlocking bit needed to go...

First I cut either end of the section that needed to be removed...