EF-3K Electronic Flare Kit, retail $37.88
Manufactured by Build-It Electronics (No longer in business)
Last updated 04-23-06

The EF-3K is an electronic flare kit that uses nine high-intensity red LEDs instead of fire to attract attention.
From the website, comes this:
  • Nine big RED Super Bright 10 mm Light Emitting Diodes or LEDs, not the usual puny 5 mm ones that are barely visible in daylight
  • LED flickering with rapid ring-around lighting of three strings of 3 LEDs each with a one-tenth of a second pause between lighting for bright and attention-getting flashing
  • Despite the high frequency of flashing, up to 50 hours of operation powered by a typical 9V rectangular alkaline battery
  • Some light output visible from three sides of the flare
  • Case made of thick and tough polycarbonate plastic with a rubber waterproof seal around the electronics, measuring only 4.5 inches X 2.6 inches X 1.6 inches
  • On/ off switch that might otherwise compromise waterproofing comes with a rubber boot.
  • Two mounting holes at diagonal corners through bottom of case accepting #8 machine screws are exterior to sealed interior - that simply means that no leakage will occur there.
It is a kit designed for you to assemble. No SMD components are used; all components are through-hole, and the PCBs come pre-drilled, so all you need to do is insert the components and solder them in place.

When completed, the flare runs from one 9 volt transistor radio battery (that you supply yourself).

The battery is not included, but shipping is free.

The EF-3K replaces the EF-12K, as it has a sturdier, more robust design; and it uses LEDs which may offer better daytime visibility than the LEDs in the EF-12K did.


To use the flare, first you'll need to put it together. Yes, you need to assemble it, but you only need to do this once.
Follow the instructional material included with the kit to solder all of the components to the PCBs (printed circuit boards).

Press the black rubberised pushbutton firmly until it clicks and then release it to turn it on.

Repeat this process in order to turn it off.

If you need to turn it back on right away, you'll want to wait at least 15 seconds from the time you turned it off, or else the blink rate will increase substantially, and battery drain will also increase by a significant amount.

To administer food to this flare, use a small or medium phillips screwdriver to unscrew and remove the four screws from the corners of the transparent lid; set them aside. Remove the transparent lid, and set that aside too.

Gently remove the used 9 volt battery from the clip, and unsnap the battery snap

Dispose of or recycle the used battery as you see fit.

Snap the battery snap onto the terminals of a new 9 volt transistor radio battery. The larger terminal of the battery snap goes to the smaller terminal of the battery, and vice-versa.

Place the battery back into the clip.

Place the transparent lid back on the front of the body, and screw in the four screws you removed earlier.

Using an alkaline 9 volt battery, the estimated battery lifetime is 50 hours.

Photograph of the front of the assembled unit.

Due to the way this product was constructed (it has an all-plastic body), the beat test would not be very appropriate.

Water-resistance was tested by throwing the product in the cistern (toilet tank). It floats with the LEDs facing either up or down. No leakage was detected.

The flare's light output is quite directional; when you place this device on the roadway, aim its LEDs to the rear if you put it near the back of your car, or forward if you put it near the front of your car.

The LEDs in the kit are 10mm red lamps. Their viewing angle is not known, but appears to be ~15.

The LEDs don't just flash at the same time; they flash in groups of three, and the entire cycle time (between the time the first three LEDs in the group of 9 LEDs flash and the time the last three LEDs in the group of 9 LEDs flash) is 100mS (100 milliseconds or 1/10th of a second).

I'm not an electronics expert, and I don't play one on TV or on the internet, so I can't tell you *exactly* how the circuitry works.

The screws for the front cover fit into threaded female METAL receptacles. not plastic ones. This substantially reduces the chance of you accidentally stripping the screw receptacles.

Beam photograph at ~12".

Spectrographic plot
Spectrographic analysis of the LEDs in this product.
Ocean Optics USB2000 Spectrometer on loan from TWO-CUBED.

Quicktime movie (.mov extension) showing the flare in use.
This is approximately 3.6 megabytes (3,953,084 bytes) in length; dial-up users please be aware.
It will take no less than fifteen minutes to load at 48.0Kbps.
I cannot provide it in other formats, so please do not ask.

The flashing is much more uniform than it appears from this movie.

Test unit was sent by P.L. of Build-It Electronics and was received on the afternoon of 01-21-06.

UPDATE: 03-02-06
The Build It Electronics website will be closing its doors on 03-26-06; so if you need anything from that website, now's the time to go and snag it. I'll be removing the URLs on this web page then.



    MANUFACTURER: Build It Electronics
    LAMP TYPE: 10mm red LED
    No. OF LAMPS: 9
    BEAM TYPE: Medium spot with coronal ring
    SWITCH TYPE: Pushbutton switch on/off
    BEZEL: LEDs protected by clear plastic housing
    BATTERY: 1x 9 volt transistor radio battery
    CURRENT CONSUMPTION: Unknown/unable to measure
    SIZE: 2.6" wide, 4.45" long, 1.55" deep
    WARRANTY: Unknown/not stated


    Star Rating

EF-3K Electronic Flare Kit *

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