Guide Cold Lights

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Correlated Colour temperature (CCT) in lighting describes how the colour of the light appears from a lamp, measured in kelvins (K). Imagine a scale from K.
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A cool white light may not make the product look as appealing but it would be a good idea to do some trials to see what works best. There is no reason why you could not have a mixture in the same setting. For example, warm white for the main room lighting and cool white for task lighting over work areas. It would also be a good idea to buy spares — as LED technology as with other technologies such as mobile phones is always improving and changing. Given their cost, cold lights are often shared among many babies, and could therefore be a vector of hospital-acquired infections similar to stethoscopes.

New methods such as infra-red devices are being developed to overcome these issues, but are even more expensive and their effectiveness has not been consistently demonstrated [ 7 , 8 , 12—14 ]. Ultrasound is emerging as a useful method for obtaining longer term IV access in deeper veins, but is also expensive and less useful for standard peripheral IV access in superficial veins in neonates [ 9 ].

Therefore, there is a need for low-cost, user-friendly and safe devices with minimal infection risk—particularly in low-income countries where the majority of neonatal deaths occur [ 10 ], and where all currently available transillumination devices are unaffordable. Red silicone LED bicycle lights, which have anecdotally been used for IV cannulation and venepuncture, as well as arterial access and peripherally inserted central lines, are a possible low-cost alternative method for transillumination.

They are also easily portable, and owing to their small size can be completely enclosed inside clinical or sterile gloves unlike most cold lights , reducing the risk of transmission of infection. In terms of safety, the red silicone LED bicycle lights used in this study use similar LED technology to many of the cold lights currently in use.

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Furthermore, purely red lights are thought to be safer than white lights which are often used in cold lights [ 11 ]. To our knowledge, there are no published studies looking at low-cost methods of transillumination, as most research has been driven by new development of expensive medical devices. We set out to test the quality of transillumination provided by low-cost red silicone LED bicycle lights in neonates by comparing them with a standard cold light currently in use.

An online survey comparing the visibility of bicycle lights and cold lights was conducted.

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Babies who were clinically unstable or whose parents did not provide consent were excluded. Sets of three photographs were taken of hands and feet i with no transillumination control , ii with transillumination with a cold light, and iii with a red silicone LED bicycle light Figs 1 and 2. Babies remained in their incubators, the background lighting being dimmed to the same level for the cold lights and bicycle lights, and kept at normal room lighting for photos without transillumination.

The bicycle lights were enclosed in a clinical glove, which is how we propose they should be used in practice to reduce infection risk.

Cold Lights | Instruments Of Discipline

Photographs were taken by a team of two researchers with an iPhone 4s. One researcher held the hand or foot of the baby, without a tourniquet, and the other took the photographs. Strict infection control procedures were adhered to throughout.


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The best quality photograph was selected among several of the same limb and transillumination approach. Sixty photos of 20 hands or feet with a control, cold light and red LED light picture of each were used in a pilot survey with 12 independent respondents.


  • Cold cathode.
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We designed an online survey including 10 sets of three photographs one control, one cold light and one bike light from each hand or foot. The best quality photographs from each limb were chosen to limit variation in quality. All photographs were reshuffled randomly for each respondent, who were asked to rate the ease of visibility of veins for intravenous cannulation invisible, barely visible, moderately visible or easily visible.

Respondents were blinded both to the method of transillumination in the photographs, as well as to the purpose of the study. For statistical analysis, the data were considered to be clustered and non-independent at the levels of the observers and individual body parts, as a given observer may rate photographs in a certain way, and there are likely to be similarities in the way observers rate particular body parts. A multilevel logistic regression model with random effects was carried out, with a cross-classified structure for both body part and observer.

The multilevel regression model also included skin colour black or white as an explanatory variable. We tested the hypothesis that the effect of bicycle light on visibility would differ by skin colour by examining the p -value for an interaction term between skin colour and type of light. Statistical analyses were carried out using Stata Version This survey was conducted within the context of a randomized controlled trial comparing the use of cold lights and bicycle lights for intravenous cannulation, which received ethical approval from the NHS Research Ethics Committee Ref: Screening on the same IRAS system provided written confirmation that separate ethical approval was not required.

Written consent was obtained from parents after being given an information leaflet, and given the opportunity to ask questions. It was ensured that no photographs contained identifiable information on any of the babies. Ten sets of three photographs control, cold light and bicycle light of hands or feet from five neonates were included in the final survey. The characteristics of these five babies are presented in Table 1. The online survey was sent by email to pediatric doctors in training in the south London deanery, of whom responded. Both electrodes alternate between acting as an anode and a cathode when these devices run with alternating current.

A cold cathode is distinguished from a hot cathode that is heated to induce thermionic emission of electrons. Discharge tubes with hot cathodes have an envelope filled with low-pressure gas and containing two electrodes. Examples are most common fluorescent lamps , high-pressure discharge lamps and vacuum fluorescent displays. The surface of cold cathodes can emit secondary electrons at a ratio greater than unity breakdown. An electron that leaves the cathode will collide with neutral gas molecules.

Warm white or Cool white?

The collision may just excite the molecule, but sometimes it will knock an electron free to create a positive ion. The original electron and the freed electron continue toward the anode and may create more positive ions see Townsend avalanche. The result is for each electron that leaves the cathode, several positive ions are generated that eventually crash onto the cathode. Some crashing positive ions may generate a secondary electron. The discharge is self-sustaining when for each electron that leaves the cathode, enough positive ions hit the cathode to free, on average, another electron.

External circuitry limits the discharge current. Cold-cathode discharge lamps use higher voltages than hot-cathode ones.

cold light

The resulting strong electric field near the cathode accelerates ions to a sufficient velocity to create free electrons from the cathode material. Another mechanism to generate free electrons from a cold metallic surface is field electron emission. Cold cathodes sometimes have a rare-earth coating to enhance electron emission. Some types contain a source of beta radiation to start ionization of the gas that fills the tube.

Nixie tubes too are cold-cathode neon displays that are in-line, but not in-plane, display devices. Cold-cathode devices typically use a complex high-voltage power supply with some mechanism for limiting current. Although creating the initial space charge and the first arc of current through the tube may require a very high voltage, once the tube begins to heat up, the electrical resistance drops, thus increasing the electric current through the lamp.

To offset this effect and maintain normal operation, the supply voltage is gradually lowered. In the case of tubes with an ionizing gas, the gas can become a very hot plasma , and electrical resistance is greatly reduced. If operated from a simple power supply without current limiting, this reduction in resistance would lead to damage to the power supply and overheating of the tube electrodes.

Cold cathodes are used in cold-cathode rectifiers , such as the crossatron and mercury-arc valves , and cold-cathode amplifiers , such as in automatic message accounting and other pseudospark switching applications. Other examples include the thyratron , krytron , sprytron , and ignitron tubes.

A common cold-cathode application is in neon signs and other locations where the ambient temperature is likely to drop well below freezing, The Clock Tower, Palace of Westminster Big Ben uses cold-cathode lighting behind the clock faces where continual striking and failure to strike in cold weather would be undesirable. Large cold-cathode fluorescent lamps CCFLs have been produced in the past and are still used today when shaped, long-life linear light sources are required.