Construction of a lamp with diodes LED

Diode LED

LED diode is the Light abbreviations   that is, LED. Therefore, it is a device that belongs to the family of the diodes and in addition emits light.

As they are the benefits of so popular element?

We have already seen them in the new models of vehicles (audi was of first), in buildings of design and now in the homes. Unlike the traditional light bulbs, that what they do are to put very hot a filament and that heat is what gives the light, or the fluorescent ones that uses mercury within the bulb (very polluting Element).

Technology LED contributes, on the one hand, under consumption, discharge luminance efficiency in a reduced space and on the other, the use of nonpolluting materials. In addition, when average a traditional light bulb it is of 1000 hours or fluorescent one 5000, the LED offers an average life of 50,000 hours.  (this of life mediates is what they say the manufacturers, and we already know that almost all have the nose a rather long one€ as the one of our Pinocho friend.

We are going to see as we can work with them and who characteristic we must understand to realise ours prioyecto.

First of all, already in our hands we have is an element that has one patita but it cuts and another one but releases. (€“) It releases must be connected to the negative polarity and (+) it releases to pole + of the battery. If we do it on the contrary, the diode does not work. We are going to explain this with the characteristic line of this device.

 

In the image of the right one is the parts of the LED.  Of them but the important ones they are To - > Anode b - > Cathode and 4 semiconductor.

We have two axes that represent the tension (vertical axis) and the current (horizontal axis). In addition they appear two curves for two temperatures. The black represents the room temperature and in her we concentrated.

The right part sample as the current evolves with respect to since it makes the tension. If we took 0.5 volts and we drew up a vertical until it touches the line we see that the approximately 20 current is mA. If we continued increasing the tension to 1 volt, the current jumps to 50 mA. It arrives a little while that if the tension is high, by the diode for so current that the burning fire€, leaves it KO.

In order to avoid this, usually one puts some limitor resistance of current that already we will see.

If we do the same but with inverse polarization (to the short leg we put + to him of the battery and for it leaves it long €“ from the battery) when increasing the tension we have current it as soon as it varies (almost horizontal line) and in addition the value to the same is very small, of the order of 20 micro Amperes.

When continuing increasing the tension the effect takes place avalanche and the current goes off (the diode suffers damages)

If we increased to the Temperature (T2) everything is accelerated, everything happens before. The graph reasons using it.

We are going to buy some diodes of high luminosity and we do not know that curve must to be able to work with them. First that we will do it is to obtain the direct curve in the factory.

For it we needed:

1 a power supply, that can varies the exit tension

2 a resistance to limit the current

3 Two voltmeters

Explanation of the circuit. In the example of above, we have a tension of 9 volts and one 10 resistance of k. This means that for that diode, where falls 1.83 Volts, the current that happen is the current that happens through the resistance (circuit series)

As in the resistance it falls 7.17 or what is the same, the 9 of the battery except the 1.83 of the diode, we can calculate the current of the resistance by the law of Ohm

I = 7.17 V/R = V/10.000? = 0.717 mA

Process:  1 Ajustamos the tension from exit to 1 volt

2 Tomamos the tension from the diode

3 Tomamos the tension from the resistance either we reduced the tension of the source the less the tension of the diode

4 Dividimos the tension of the R between its value, to obtain the current

5 Hacemos this until the value of 9 volts increasing 0.5 volts in each step. To take all the values to a table where the luminosity of the diode is included

6 Construimos the graph in graph paper

The graph will be to us useful to determine that tension falls the diode when the maximum light with the minimum consumption of current. It is necessary to find out the maximum current of the diode (given by the manufacturer) not to exceed that limit

If we do not have it we can obtain increasing it the value of the source until the diode spoils. The value that has the R divided by its S-value the Im¡x

2 Step. We already have the optimum value of work of the diode, that is the tension that must have between its legs. Now to avoid to put limitor resistance, we are going to combine them so that it is not necessary the resistance. If we cleared the resistivo component, we avoided energy losses.

3 Buscar at home a current feeder, is worth the one of the mobile (shipper), the feeder of router, etc. All have a sticker that indicate the tension of exit and its tension. We come from the following way

a ) If the fall in the diode calculated in the previous point is 1.5 volts and our source has an exit of 4.5, Voal¡, we put three diodes in series and at each it arrives the 1.5 volts to him. If we want that our lamp has 6 diodes, then we make two connected identical circuits in parallel

b ) If the source has exit of 6.5 volts, so that it falls 1.5 in each diode we must put a value resistance

  R = (6.5 €“ (4*1,5)) /I     Where the value of I am obtained from the previous graph

3 Step. We construct the lamp with CD. In this case we are going to use 4 CD, two for base and two for the iluminaria. Both CD of the part inferior is used for the base of the lamp. They must be separated certain distance to incorporate a switch. The separation can be done by means of three points of silicone, screws with pasamuros, felt with adhesive of double slide, etc. The method is free. In the CD superior it is necessary to make the perforation for the switch.

 4 On 3 CD becomes the perforations so that patitas of the diodes so that the part of the CD but shining east downwards. It is possible to be made perforations with reel of diameter of 1 mm (two by diode) or one of 5 mm to enter all the body of the LED.

On the other expensive the connections become of the diodes (each on the basis of the circuit that it obtains from the previous calculations).

4 CD serves as cover. Between 3 and 4 CD is united of the form that 1 and 2.

The two pairs of CD are united by a tube whose interior passes feeders.

If we have difficulty in understanding the differences between Intensity, tension and Resistance, I have made a story where a little is explained better. If you want you can see it in

The Chocolate Small house

To see http://es.calameo.com/read/0005207894ac4a82b5c3a