PF is generally only a problem in commercial applications in inductive devices which use very high power such that the delays between current and voltage add up to produce significant power losses. Other components which will cause delays betweeen current and voltage include transformers and voltage regulators and ballasts in flourescent lighting.
In residential settings such loses are relatively minimal and electricity companies will only charge for the real power anyway. However, there is still a loss so those energy conscious or green individuals may wish to examine the power factor of their LED lighting power supplies to ensure that have a PF of greater than 0. Due to the high capacitive loads required to stablise the current at very low dimming levels to avoid flicker PF is poor, generally approx 0.
However, in practice this is not a big problem given these drivers are generally used in applications where the lamps will be dimmed down to low levels for most of their life such that the real power is 2 or 3W and the Apparent power still very low at up to 4. Although as noted this is mainly an issue in commercial lighting where lamps are on for 8 to 24 hours per day.
If you are a residential user you can be less concerned. Neverthless please note the PF ratings on the speicfications tab of our products to get an idea of efficiency. If you are a commercial customer with a business that is particularly dominated by highly inductive loads such as electric motors or a large collection of capacitive loads with poor PF, then you should consider power factor correction PFC and visit our section on government rebates and schemes where such projects can be subsidised.
If you are a very high energy user then PFC can leading to very large savings in electricity and power bills. Energy Efficiency of LEDs. Building Technologies Program. Frequently Asked Questions. International Shipping Info. Send Email. Mon-Fri, 9am to 12pm and 1pm to 5pm U. Mountain Time:. This product has shipping restrictions, so it might have limited shipping options or cannot be shipped to the following countries:. Added to your shopping cart.
LEDs - those blinky things. A must have for power indication, pin status, opto-electronic sensors, and fun blinky displays.
This is a very basic 5mm LED with a red lens. It has a typical forward voltage of 2. If it requires power, you need to know how much, what all the pins do, and how to hook it up. You may need to reference datasheets, schematics, and know the ins and outs of electronics.
Skill Level: Rookie - You may be required to know a bit more about the component, such as orientation, or how to hook it up, in addition to power requirements. The centre lead k is the common cathode for both LEDs, the outer leads a1 and a2 are the anodes to the LEDs allowing each one to be lit separately, or both together to give the third colour.
Each internal LED can be switched on and off separately allowing a range of colours to be produced:. LEDs are available in a wide variety of sizes and shapes. The 'standard' LED has a round cross-section of 5mm diameter and this is probably the best type for general use, but 3mm round LEDs are also popular.
Round cross-section LEDs are frequently used and they are very easy to install on boxes by drilling a hole of the LED diameter, adding a spot of glue will help to hold the LED if necessary. Other cross-section shapes include square, rectangular and triangular.
As well as a variety of colours, sizes and shapes, LEDs also vary in their viewing angle. This tells you how much the beam of light spreads out. Rapid Electronics stock a particularly wide selection of LEDs and their website is a good guide to the extensive range available including the latest high power LEDs.
An LED must have a resistor connected in series to limit the current through the LED, otherwise it will burn out almost instantly.
For standard 5mm diameter LEDs the maximum current is usually 20mA, so 10mA or 15mA are suitable values for many circuits. The current must be in amps A for the calculation, to convert from mA to A divide the current in mA by If the calculated value is not available choose the nearest standard resistor value which is greater , so that the current will be a little less than you chose.
In fact you may wish to choose a greater resistor value to reduce the current to increase battery life for example but this will make the LED less bright. Red LEDs have the lowest voltage, yellow and green are a little higher. Blue and white LEDs have the highest voltages. For most purposes the exact value is not critical and you can use 2V for red, yellow and green, or 4V for blue and white LEDs.
For more information on the calculations please see the Ohm's Law page. If you wish to have several LEDs on at the same time it may be possible to connect them in series.
All the LEDs connected in series pass the same current so it is best if they are all the same type. The power supply must have sufficient voltage to provide about 2V for each LED 4V for blue and white plus at least another 2V for the resistor.
Avoid connecting LEDs in parallel!
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