Folder The madness of grandeur

The management of the Alexiens will today try to enlighten you on the notions of sizes that we find associated with our connected objects. We see scrolling W, A, V or lm ... But kékeussé !? kekidit !?
Don't panic, the Alexians are going to give you a quick refresher course in physics. Ready ? So follow us!

We will enlighten you on the bulbs

When you go on characteristics of connected bulbs, you very quickly find data with Watts, lumens, volts or even information on the bases.

Let's get rid of the pellets before we go ahead.

It exists several types of sockets. The most common being the E27. What does this figure correspond to? The E27 has a diameter of 27 mm. And for the E14 ? 14 mm! And the E? This means that they are screw bulbs. Bayonet bulbs are BXXs (B22 with a diameter of… 22 mm, that's it !!). And then we find more specific bases such as GU10 (the spots with the two specific pins, for 230 volts specifically) or more confidential like the GU4, 2 pins… G refers to bases with two or more pins.



What do the watts teach us on a light bulb?

So in principle, everything and nothing ... For example, a 7 Watts (W) bulb will consume 7 W, but it has nothing to do with the restored power. For information, the Watt corresponds to the power or the energy flow of a circuit, a bulb ... 1 W = 1 joule per second! For information, 4,18 d = 1 calorie = quantity of energy necessary to raise the temperature of 1 gram of water by 1 ° C ... In short, with LED lamps, this value will have to be multiplied by 10, approximately, to have equivalences with incandescent lamps.

So 7W = 70 W. The more Watts there are, the more powerful the bulb will be. But this is not enough to get an idea of ​​the rendering, especially with LEDs. To be taken into account more for consumption than for the result.

Here are other sizes to consider. First of all, the color temperature of the light will be given to you in Kelvin (K). The higher the K, the more the light will draw on the blue, so it will be cold. Conversely, the lower the K, the more the light will draw on the orange.


Color temperatures in Kelvins (K)


You will also find lumens or lm ... This will represent the luminous flow. And there, be careful, because an LED bulb, with the same number of Watts can have 40% less lumens than another even if on average, 10W corresponds to 100 lm (therefore 1 W in LED). Gold, the more lumens, the more it lights up. Lux are lumens per m². But what does this correspond to?


Lux = Lumens x m²


It is not easy to give the necessary power in lumens per room to choose your bulbs, but logic does the rest ...


Some indications

Do you know about the outlets?

The outlets are often associated with the notion of Watts and / or Amps and Volts.

But do the manufacturers mean to us?

First of all, the volts. The volt is the unit of electromotive force or voltage. For information, a nerve cell "works" with a voltage of 0,075 V and the TGV with 25000 V ... In Europe, wall outlets have a voltage of 220 to 240 V (alternating). Confirm that your devices have a usable voltage range of 220-240V. Which is normally the case, but be careful if you buy products abroad.



The second point is amperage. Amperage is the intensity of the electric current, that is to say the quantity of current which passes or which can pass in a device or a circuit or the flow of electrons which will cross the conductor. It is the equivalent of a flow of water through a pipe. The sockets are given for a maximum amperage that they will withstand without problem. But often, it is not easy to make the link between this amperage and what we can connect to it because we only have Watts at our disposal.

The Watt, it is the equivalent of the flow of water in a pipe multiplied by the pressure. And we understand why we must pay attention to what we plug into it. If you only have Amps listed on your outlets, do this simple calculation: current (16 A for example) x voltage (250 v). In this case, it gives 4000W not to be exceeded. It's a bit like when you increase the flow of the garden hose fully and it disconnects from the faucet because too much pressure, too fast.

For the speakers, we listen to you?

Have you wondered why the power of a speaker is expressed in Watts (W) and not in decibels, which is a measure of loudness?

First of all, a decibel (dB) is a tenth of Bel and does not belong to the international system of units because it is a logarithmic scale. That is, when the value increases by 3 dB, the sound intensity is multiplied by 2. So 50 dB is half as loud as 53 dB. And 16 times louder than 38 dB.




Okay, the dB we know, but why are we only talking about Watts (again) for the power of the speakers?

First of all because we are talking about power and dB is not a power, but an intensity (like the Ampere for electricity). In fact, this power is the mechanical power of the speaker. The higher the Watts (W), the louder the sound will be.


Analog display of an amplifier simultaneously showing Watts and decibels
Analog display of an amplifier simultaneously showing Watts and decibels


But there is no simple link between W and dB ... Why? Because the dB have no unity and from there, difficult to find links between the two. However, we can find data provided by the manufacturers making a link between these values, given for a particular voltages (2,83 V for example), a given sensitivity at 1 m from the enclosure. For a 15W speaker, like an Echo, we could be around 96 dB if the efficiency level is 85 dB… But we couldn't find this data…

And there you have it, thanks to this file, you can now shine in society or choose your future connected devices with complete peace of mind. Aren't we nice ?!

Did i choose Alexa or did she choose me? Let's say that as a beta tester, it's a bit of both! And I do not regret having met our favorite assistant nor this adventure undertaken with Alexien Modo. Technophile, self-taught and loving popularization, I try to make our common passion easy to access!