What is an R7s light bulb

An R7s bulb is a double ended, recessed single contact (RSC) linear lamp. The R7s is the base designated for J type linear halogen lamps having a T3 shape. The tubular shape of the bulb is 3/8 inches in diameter and the length measures either 118 mm or 78 mm. Some less common lengths are 189 mm, 254 mm and 331 mm. The J type halogen lamps of different sizes and voltages are found in variety of applications. They’re used in flood lighting system for both indoor and outdoor applications, stage and studio lighting systems, cabinet lights, under the counter lights, closet lights, desk lamps, and ceiling lamps. Most of J type halogen lamps require use of enclosed fixtures and operate on AC mains power (120 V in U.S., 230 V in Europe).

Retrofit R7s LED bulbs

R7s LED bulbs are replacement lamps for J type linear halogen lamps. They come with the same RSC base on both ends and have the length of the J type linear halogen lamps that are to be replaced. Not all R7s LED bulbs have a T3 shape due to the complexity that LED technology brings. Therefore, an R7s LED bulb is not necessary a J type lamp but has the same electrical interface and length with its predecessor.

Light distribution

R7s LED bulbs are provided with light emitting patterns in various forms and light emitting surfaces in various sizes. High power R7s LED bulbs for use in outdoor flood lights typically come with multiple light emitting surfaces in order to generate a wide beam angle while reducing optical loss that occurs when omni-directional lamps are used. An R7s LED bulb with T3 or cylindrical shape usually produce omni-directional illumination to mimic the light pattern of halogen lamps. R7s LED bulbs use either mid-power SMD LED packages or COB LED arrays. J type tubular R7s LED bulbs almost exclusively use COB arrays since COB technology allows LED packaging in narrow spaces.

Thermal management

While R7s LED lamps are assumed to deliver huge energy savings over a long operational period, their performance, efficiency and reliability may vary widely. Of particular concerns during the design of an R7s LED bulb are thermal management and AC-DC power conversion. R7s LED bulbs are typically used in an enclosed system where convective cooling is not present. The conductive cooling of the LED bulb is limited by the thermal conductivity of the RSC bases. Thermal buildup within the LED lamps is very likely to happen in high wattage systems. Operating LEDs at elevated junction temperatures will inevitably shorten the lamp life as a result of lumen depreciation and color shift. In J type tubular R7s LED lamps, the driver design is significantly challenged because of the space constraint. Oftentimes, the reliability and efficiency are traded for a small form factor.