LED stands for Light Emitting Diode and is a semiconductor light source that has been around since 1962 in red indicator form. A diode is an electronic device that passes current in one direction and sees common usage as a rectifier. The LED, however, consists of a chip of semiconducting material doped with impurities to create a p-n junction. As in other diodes, current flows easily from the p-side, or anode, to the n-side, or cathode, but not in the reverse direction. Charge-carriers (electrons and holes) flow into the junction from electrodes with different voltages. When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon which emits light. Hence the name light emitting diode.

Recently, improvements in the LED have seen a super bright family of devices capable of providing light of blinding intensity. Early forms of these super bright LEDs produced very cold and unattractive light. Now versions of the device are available that produce "warm" white light. My experience with these has been very good as replacements for conventional G-4 10 watt incandescent lamps. Before deciding to replace your incandescent lamps make sure you understand the details. I hope this article answers some of your questions.

A collection of light sources in G-4 style base. They all have their place.

We have JC halogen T-3 10 watt 12V clear lamps throughout our bus. Several years ago we replaced some of the soffit lamps with LEDs (see middle device in picture above) as an experiment. The light was very cold and they didn't dim properly. Overall a disappointing light source for us. Recently a brand called Scintiluna warm white LEDs came out with a side pin G-4 base at 140 lumen. These were purchased from Amazon at $9.25/ea SKU: 16-TULZ-ZPKE. The experience was very positive with this product and I'd recommend these LEDs for general lighting requirements. They provide significantly more light, run much cooler, draw less power, burn longer - all with a pleasing spectrum of light.

Here's a comparison of current draw @ 12VDC:

1) 10 Watt Incandescent - 830 mA
2) 6 segment LED older version - 150 mA, 23mm diameter
3) 10 segment LED new version - 150 mA, 30mm diameter

As you can see, the LEDs draw less than 20% as much power compared to a conventional incandescent lamp. Their cooler operation means less deterioration of the sockets, reflectors, lens and electricals. I also think they are safer owing to just running cooler.

As for the warm white light, they are close to an incandescent but still run slightly cold. Not an objectionable characteristic in my opinion. Some of the coldness comes from their increased brilliance. Over sinks and counter tops the extra light is really nice to have. It far outweighs any slight spectral differences. The power saving is HUGE and a clear advantage for those running off battery/solar power.

LEDs have no filament and thus no thermal inertia. This means they dim much differently than incandescent lamps. You'll notice them not dimming as much. Some of the older versions of LEDs will strobe which is very obnoxious. Dimming circuits use what's called a pulse width modulation scheme. Power is rapidly turned on and off maybe 2,000 times per second. By varying the ratio of time on to time off the average power to the lamp can be controlled. In a filament lamp, the dwell time between full on causes the filament to cool and thus dim. The thermal inertia in the tungsten filament smooths out the light. Our eye sees a constant warm low light. LEDs, however, have no filament and can track rapid power fluctuations which is disturbing to the eye. Newer LED driver circuits include a small capacitor to smooth out the bumps. It really improves the dimming effect but it still isn't quite the same as a filament lamp.

Overall I'd rate the newer warm white LEDs as an excellent product. Keep in mind they won't mount in fixtures where the socket is vertical in the housing. Fixtures with horizontal sockets are required for the units shown in this article. As for life expectancy, I haven't had a chance to evaluate this yet. I'll post an update in a couple of years.

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