Month: November 2015

The jargon I feel good to know for lighting.

 

Watt and Lumen

Watt indicates the amount of power a bulb uses to provide light, while lumen is the unit used to measure the light output of a light bulb.

Most people think that the wattage (W) of a bulb tells you how much light it gives. But wattage only tells you how much power a bulb uses. The light output of a bulb is actually measured in lumen (lm). For example, some bulbs, like LED, give the same light output (in lumen) as a classic bulb, but for a much lower wattage. So, to see how bright a bulb is, think in lumen, not watt. The higher the lumen value, the greater the light output. The fact that some bulbs are brighter than others means they are suitable for other purposes.

For example, dimmer bulbs are for bed-side lamp, medium for living room, bright for bathroom.

I see my project lamp to have dim to medium bulbs.

 

Cap Type

There are different types of caps to fit your light fixture because one size doesn’t fit all.

The cap is the bridge between the bulb and the power-source fitting, providing just the right amount of current to make the bulb glow.

 

Wide and Focused Light (link)

The shape of a bulb has a big impact on the light effect it delivers. This is because the shape determines the width of the light beam. Standard bulbs can achieve a 360-degree distribution of light. Spots can deliver a focused light distribution at a 25-35-degree beam angle.

Probably, the standard bulbs is better for my project because the cover shape for my design is semi-sphere. By having a 360-degree light distribution, the reflecting properties of the overall lamp will be better.

 

Switch Cycles

Switch cycles indicate the number of times a bulb can be switched on and off before it fails. The room a bulb is being used in can make a big difference to the light bulb’s lifespan. The room a bulb is being used in can make a big difference to its lifespan. For example, bulbs in a living room often stay on all evening, whereas those in a bathroom may get switched on and off much more regularly. Halogen bulbs typically have a switch cycle of 8,000. Energy savers up to 30,000 and LED bulbs about 50,000.

 

Color Temperature

Color Temperature is indicated in units called Kelvin and its value determines whether light bulbs produce warm or cold light. Bulbs with a low Kelvin value produce a warm yellow, more cozy light, while those with a higher Kelvin value produce a cool blue, more energizing light.

Around 2700-3000 K will be good.

 

Color Rendering Index (link)

The sun is the most natural light we have and therefore is the standard of comparison for any other light source. Natural outdoor light has a Color Rendering Index (CRI) of 100 – and therefore is the standard of comparison for any other light source. The higher the CRI (based upon a 0 – 100 scale), the more natural the colors appear.

 

Run Up Time

For some bulbs it takes longer to reach their maximum light output level. Some bulbs are faster than others – because they have a shorter
‘run- up time’. This is how long it takes for a bulb to reach its maximum light output level. Halogen and LED bulbs have the fastest run-up time – of less than one second – for almost instant illumination. While some energy savers need 5-30 seconds to reach their maximum light output.

 

Here is a comparison of bulbs that I have taken from the website based on what I would like to have for the light bulbs.

I am looking at LED light bulbs instead of Halogen bulbs as of now.

 

Source:

http://www.philips.com.sg/

From wikipedia

Most fans used in computers are of the axial-flow type; centrifugal and crossflow fans are sometimes used. Two important functional specifications are the airflow that can be moved, typically stated in cubic feet per minute (CFM), and static pressure. Given in decibels, the sound volume figure can be also very important for home and office computers; larger fans are generally quieter for the same CFM.

Dimensions

The dimensions and mounting holes must suit the equipment that uses the fan. Square-framed fans are usually used, but round frames are also used, often so that a larger fan than the mounting holes would otherwise allow can be used (e.g., a 120 mm fan with holes for the corners of a 90 mm square fan).

The width of square fans and the diameter of round ones are usually stated in millimeters; common sizes include 40 mm, 60 mm, 80 mm, 92 mm, 120 mm and 140 mm (my current design diameter is 160 mm), although 8 mm,^[5] 17 mm,^[6] 20 mm,^[7] 25 mm,^[8]30 mm,^[9] 35 mm,^[10] 38 mm,^[11] 45 mm,^[12] 50 mm,^[13] 70 mm,^[14] 250 mm^[15] and 360 mm^[16] sizes are also available. Heights are typically 10 mm, 25 mm or 38 mm, but this is usually not an important dimension as it does not affect mounting holes or apertures in the case.

Typically, square 120 mm and 140 mm case and power supply fans are used where cooling requirements are demanding, as for computers used to play games, and for quieter operation at lower speeds. 80 mm and 92 mm fans are used in less demanding applications, or where larger fans would not be compatible. Smaller fans are usually used for cooling CPUs, graphics cards, northbridges, etc.

Rotational speed

The speed of rotation (specified in revolutions per minute, RPM) together with the static pressure determine the airflow for a given fan. Where noise is an issue, larger, slower-turning fans are quieter than smaller, faster fans that can move the same airflow. Fan noise has been found to be roughly proportional to the fifth power of fan speed; halving the speed reduces the noise by about 15 dB.^[17] Axial fans may rotate at speeds of up to around 19,000 rpm for smaller sizes.^[18][19]

Fans may be controlled by sensors and circuits that reduce their speed when temperature is not high, leading to quieter operation, longer life, and lower power consumption than fixed-speed fans. Fan lifetimes are usually quoted under the assumption of running at maximum speed and at a fixed ambient temperature.

Air pressure and flow

A fan with high static pressure is more effective at forcing air through restricted spaces (do I need this too?), such as the gaps between a radiator or heatsink; static pressure is more important than airflow in CFM when choosing a fan for use with a heatsink. The relative importance of static pressure depends on the degree to which the airflow is restricted by geometry; static pressure becomes more important as the spacing between heatsink fins decreases. Static pressure is usually stated in either mm Hg or mm H₂O.

Air pressure is most important for cooling. It indicates cooling power per unit area. If the diameter of a fan is constant, then more air pressure indicates more air flow. A simple relation of air flow with air pressure is(fan diameter)² * (air pressure)² / (100 * 28.51875) = air flow, where the diameter of the fan is in millimeters, air pressure is in mmH2O, and air flow is in cubic feet per minute.^{[citation needed]}

 

Additional reading

Bearing types

The type of bearing used in a fan can affect its performance and noise. Most computer fans use one of the following bearing types:

• Sleeve bearings use two surfaces lubricated with oil or grease as a friction contact. They often use porous sintered sleeves to be self-lubricating, requiring only infrequent maintenance or replacement. Sleeve bearings are less durable at higher temperatures as the contact surfaces wear and the lubricant dries up, eventually leading to failure; however, lifetime is similar at relatively low ambient temperatures.^[20] Sleeve bearings may be more likely to fail at higher temperatures, and may perform poorly when mounted in any orientation other than vertical. The typical lifespan of a sleeve-bearing fan may be around 30,000 hours at 50 °C. Fans that use sleeve bearings are generally cheaper than fans that use ball bearings, and are quieter at lower speeds early in their life, but can become noisy as they age.^[20]

• Rifle bearings are similar to sleeve bearings, but are quieter and have almost as much lifespan as ball bearings. The bearing has a spiral groove in it that pumps fluid from a reservoir. This allows them to be safely mounted with the shaft vertical (unlike sleeve bearings), since the fluid being pumped lubricates the top of the shaft.^[21] The pumping also ensures sufficient lubricant on the shaft, reducing noise, and increasing lifespan.

• Ball bearings: Though generally more expensive, ball bearing fans do not suffer the same orientation limitations as sleeve bearing fans, are more durable at higher temperatures, and are quieter than sleeve-bearing fans at higher rotation speeds. The typical lifespan of a ball bearing fan may be over 60,000 hours at 50 °C.^[20]

• Fluid bearings have the advantages of near-silent operation and high life expectancy (comparable to ball bearings), but tend to be the most expensive.

• Magnetic bearings or maglev bearings, in which the fan is repelled from the bearing by magnetism.

Connectors

Connectors usually used for computer fans are the following:

Three-pin Molex connector KK family

This Molex connector is used when connecting a fan to the motherboard or other circuit board. It is a small, thick, rectangular in-line female connector with two polarizing tabs on the outer-most edge of one long side. Pins are square and on a 0.1 inch (2.54 mm) pitch. The three pins are used for ground, +12 V power, and a tachometer signal. The Molex part number of receptacle is 22-01-3037. The Molex part number of the individual crimp contacts is 08-50-0114. The matching PCB header Molex part number is 22-23-2031.

Four-pin Molex connector KK family

This is a special variant of the Molex KK connector with four pins but with the locking/polarisation features of a three-pin connector. The additional pin is used for a pulse-width modulation signal to provide variable speed control.^[22] These can be plugged into 3-pin headers, but will lose their fan speed control. The Molex part number of receptacle is 47054-1000. The Molex part number of individual crimp contacts is 08-50-0114. The Molex part number of the header is 47053-1000.

Four-pin Molex connector

This connector is used when connecting the fan directly to the power supply. It consists of two wires (yellow/12 V and black/ground) leading to and splicing into a large in-line four-pin male-to-female Molex connector. This is the same connector as used on hard drives before the SATA became standard.

Dell proprietary

This proprietary Dell connector is an expansion of a simple three-pin female IC connector by adding two tabs to the middle of the connector on one side and a lock-tab on the other side. The size and spacing of the pin sockets is identical to a standard three-pin female IC connector and three-pin Molex connector. Some models have the wiring of the white wire (speed sensor) in the middle, whereas the standard 3-pin Molex connector requires the white wire as pin #3, thus compatibility issues may exist.

 

Common noise reduction methods

• Replace fans with low-speed, large diameter fans with low bearing and motor noise. Larger fans can move more air oer revolution than smaller fans.
• Cover the case with sound insulation material such as rubber, foam or fiber mat, although this method has limited effectiveness. The material can (because of its weight) dampen case resonance, and can also absorb some high-frequency sound. Care must be taken to be sure the soundproofing does not interfere with airflow.

I was thinking about using the solar power. Maybe this can be an improvement after settling down the design and everything.

An interesting product http://www.solight-design.com/ which I found.

 

The Muji fan is using dual rotor.

“Compared with single rotor small axial flow fans, dual-rotor small axial flow fans is better regarding the static characteristics. But the aerodynamic noise of dual-rotor small axial flow fans is worse than that of single rotor small axial flow fans …. the noise of fans with perforation blades is reduced. Additionally, the noise of the fans decreases with the increase of the number of perforations.” —

http://link.springer.com/article/10.1007/s11630-015-0764-4

 

Additional info

“Noise generated by an axial fan is mainly composed of two types. One is rotational noise which has discrete frequency components, and the other is turbulent noise which has a broad band frequency component. Generally the pressure change due to blade passage causes rotational noise, and the pressure and velocity fluctuations cause turbulent noise.”  —

https://www.researchgate.net/publication/274288022_Study_of_Fan_Noise_Estimation._1st_Report