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Discussion Starter · #1 · (Edited)

THIS ENTIRE CIRCUIT/MOD can be replaced by a commercial product i discovered on this website, for a mere $25 dollars
this mod therefore is redundant and should only be attempted for bragging rights.

My first post here! :yes:

As my vehicle did not come with factory bi-xenons, i wanted to ensure proper operation of my after market HID's under all conditions and add a few features i though the car was missing.

The following are the problems i aimed to solve with my custom circuit:

1 - When the engine starts, in order to allow proper current and ensure no misfire on the bulbs under all weather conditions, i wished to allow a delay time before the HID's trigger on.

2 - During daytime driving when the low beams (HID's) are off, using the flash to pass function (multiple sequent high beam flashes) causes the HID's to strike several times as the high beams are wired to the low beams as well. This is not very good for the HID's, and while a proper hot re strike may not damage quality bulbs/ballasts, several cold strikes may very well do harm quickly. The circuit will ensure that during the day, HID's will ignite and stay on only if the high beam stalk is held in the on position for more then a few seconds.

3 - To implement a delay off timer, which at night, continues to run the HID's after the car has been turned off and locked, in order to illuminate the surrounding for a short duration (typically 30 seconds to 1 minute). This is a feature found on many other vehicles with factory xenons.


After multiple designs, using analog timers, digital timers and plain old analog circuitry, i constructed three circuits that would preform these tasks. The two final circuits are shown below in their schematic form. The simpler circuit was chosen for its ease or replication. However, this has some implications. Because of the fully analog nature of this circuit, variation in certain components will create the need to vary two resistors in order to achieve desired timing intervals.

The following is a more complex design that i did not go with, due to its higher complexity, in case any members actually attempted to reproduce this for their vehicle.


After long thought, i was able to redesign this circuit in its simplest form possible. Using only several components that are readily available at all electronics hobby stores and online. This circuit is shown below. A note, that in the below circuit, the 100 Ohm resistor in the bottom right corner actually represents the relays coil pins. The upper right square is the +12 terminal of the cars battery, and will be spliced into the relay harness, and the upper left square is the +12 power from the headlight socket of the vehicle. All will be explained further down.

All components required are listen below.

2 Pieces of 2N3904 NPN Transistor

Assortments of resistors (will be explained later):
100, 1K, 5K, 10K, 40K, 100K (Ohms)
Note: Standard resistors sizes are not exact to these and are okay

2 Pieces of 1N4007 Diode, or (equivalent generic diode)

2 Pieces of 1uF Capacitors (16 Volts or higher)

1 Piece of 470uF Capacitor (16 Volts or higher)

1 Piece low power compact sized relay (12VDC, any will work)

1 HID Relay harness required

If your still reading, your either really interested to see the outcome, or your actually going to build this!


After prototyping the circuit, pictured below, i decided to go ahead and build a final tester.

You can aquire small hobby PCB project boards from most electronics suppliers to make the circuit more clean. I started by soldering the components, as compact as possible onto such a board. Here is the the result.

The components will connect at the bottom of the board, by simply soldering the tracks together as seen below.

Once complete, the circuit was put into a small box. These relatively weather sealed project boxes can be found at many electronic hobby stores in different shapes and sizes.

Next, the circuit will need to be spliced into the relay harness for proper operation. Here is the wiring diagram, which includes the splice points and the relay harness.

and the final spliced circuit

After wiring the circuit up and making sure that all connections are okay (i recommend testing the circuit using any 12V power supply lying around in the house from dead electronics), the circuit may be installed in the car for testing.

And now as for customization, the delay time ON, after engine starts, is decided by RCharge. Varying this resistor will change this time. Lowering it will reduce the time and increasing it will increase the delay. I decided to go with approximately 4 seconds. And RTimer will vary the delay off time, after which the HIDs will turn off. I picked approximately 1 minute for my setup. lowering and increasing the resistance has the same effect explained above. Getting timer values above one minute may be unreliable and difficult. The resistor values given will not replicate the values i got, due to the fact that different relays have different coil currents. And as such you will need to play with these two resistor values in order to achieve desired timings. You may use potentiometers, and even fine pitch potentiometers if your crazy about exact timings.

If you decide to give this a try, good luck, and remember,


I will post a video of the circuit functioning in the upcoming days. This circuit can be applied to most any vehicle with generic headlight design and is not Mazda exclusive.


49 Posts
Please repost pictures~~

Squats nd Oats
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