Gear Test: Sensibulb LEDs

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Sensibulb is a refined approach to 12-volt DC lighting that was achieved by combining innovative thinking and existing technology with engineering assistance from NASA.

Sensibulb is a refined approach to 12-volt DC lighting that was achieved by combining innovative thinking and existing technology with engineering assistance from NASA.

Most of us are familiar with the trend of replacing traditional filament light bulbs in many applications with more efficient LED, or light emitting diode, technology.

 

The solid crystalline structures of LEDs use less current and remain cooler than incandescent bulbs, but they do have drawbacks. LEDs typically don’t provide the same wide coverage or the warm light associated with standard bulbs. With their narrowly focused beams, conventional LEDs need to be ganged together to provide any degree of broad light. An LED’s critical operating temperature is around 140 F, and the numerous LEDs required in this configuration can create enough heat within a fixture to affect their reliability.

The folks at Sailor’s Solutions felt they had a better idea and spent more than two years developing the Sensibulb. Unconventional in appearance, the Sensibulb light consists of six tiny LED crystals mounted on a printed circuit board. The board is attached to an anodized aluminum heat sink, and the entire unit measures a little more than 1-1/4 inches square by 3/8 inch thick. Designed for the marine environment, the visible circuitry and diode crystals are conformal coated, while the balance of the circuitry is encapsulated in a black temperature-transfer epoxy.

There are two wire pigtails connected to the light: white for 12-volt DC power and orange for the available dimmer, but more on that later. Installation into almost any fixture is easy using the peel-and-stick foam tape provided or by using an available “G4” socket mount. Wiring is a simple plug-in design, and the built-in logic circuit eliminates polarity issues. The Sensibulb pigtail can be plugged directly into the popular halogen G4 socket or installed in older fixtures by using the available G4-to-bayonet adaptor. The adaptability of Sensibulb to a variety of fixtures eliminates the need to replace the entire fixture when upgrading lighting.

The issues of LED brightness and wide focus were addressed by a Japanese company, while a local engineering firm worked on developing a color spectrum that is similar to a halogen light but with the warm, gold overtone of more conventional tungsten lamps. The difficult part was in controlling the diodes while maintaining them at peak operating temperature. Sailor’s Solutions applied for and received a grant for engineering assistance from NASA, and the task of refining the heat sink design was taken over by Boeing Aerospace at the Johnson Space Center, according to the company. The circuitry and heat sink work together to optimize the LED operating temperature at around 140 F, says Sailor’s Solutions.

My test setup for the Sensibulb consisted of a 12-volt cabin light, digital volt/ammeter, analog light meter reading in foot-candles, and a constant 12-volt power source. This is no laboratory set up by any means, but it provided general data to show circuitry operation. In theory, as the lamp is turned on the LED crystals emit light and begin to heat up. This heat is transferred to the heat sink and monitored by the internal circuitry. As the temperature approaches the upper limit of around 140 degrees, the circuitry will decrease the current being supplied to the diodes, allowing them to cool slightly. The cycle is repeated for the duration of the lamp’s usage.

I installed the assembly into a dome light and switched it on, supplying 12.83 volts DC. The lamp was drawing 0.24 amps at 66 degrees and produced 50 foot-candles of illumination, measured 1 foot from the meter. By comparison, the standard 21-candlepower incandescent bulb it was to replace drew 1.49 amps at 277 degrees and produced 42 foot-candles of light at the same distance from the meter.

After five minutes the Sensibulb’s amperage dropped to 0.21, the LED rose 101 degrees, and foot-candles dropped to 48. Ten minutes into the test, the LED was 135 degrees, the heat sink was 101 degrees, and the output had dropped to 42 foot-candles. It took 20 minutes for the LED to reach 140 degrees, at which time the heat sink was 110 degrees and the light output 40 foot-candles. The current draw at this point was only 0.16 amps. I introduced a cool breeze across the heat sink for a short time (canned air used for computer keyboard maintenance) and watched the amperage draw and foot-candle readings increase, indicating good thermal control.

Although the foot-candles dropped to 40 during the test period, the visible difference in light output was negligible. The color of the light was pleasing, comparable to a standard 100-watt incandescent tungsten lamp — not an easy task for LEDs. Light output was even and without hot spots, covering at least 100 degrees of arc. I prefer the Sensibulb’s light characteristics to the 10-watt incandescent bulb that was supplied with the dome fixture.

As mentioned earlier, the orange pigtail can be used to connect the available lamp dimmer. I also found that by jumping across the two orange wires, the light output is cut in half, but the current drops .025 amps. I would think that if the leads were connected to a double-pole toggle switch, you could have two levels of light output at your fingertips.

Sensibulb is thoughtfully designed and well-constructed. Although not inexpensive, it should prove to be a worthy investment if you are concerned about conserving battery power and light quality.

Sensibulb is available in red or white from Sailor’s Solutions for $39.95 each. A reading light bracket sells for $3.95, the bayonet socket adaptor $1.95, and the dimmer $19.95. For more information, contact Sailor’s Solution at (631) 754-1945 or visit www.sailorssolutions.com .