Posted in إلكترونيات

Don’t click if you’re electrical engineer! Extension Cables!

Last week I met a friend of mine who had completed his M.Sc. degree in computer sciences at KFUPM and while we were  chatting, he asked me a basic question of  how to know the capability

socket

of  electrical sockets at homes and how to compare these ratings with electrical appliances ratings?

Two days later, I received a call ,again from an IT guy who attended the same college, and he asked me how to select the best plug extension cable?


For this reason, I decided to write this post to let non-electrical people know how textentiono buy the best extension cables for different applications.


First, lets understand how do these things relate to each other; a socket and an extension cable.

Basically, every house has many sockets installed at almost every wall and, these sockets are connected through wires inside the walls to a main circuit breakers panel inside your house which has circuit breakers. See below fig.


Circuit Breaker Panel

Circuit Breaker












A circuit breaker is a switch that will automatically shut off the main power going to a specific socket when an overload occurs at this socket. An overload occurs when a high electrical current passes through your device which is connected to the socket and this current t is larger than the circuit breaker electrical current rating.

In other words, a circuit breaker acts like a fuse with specific electrical current rating but it’s unlike a fuse which is used for one time only. The idea behind a circuit breaker is then to protect the main power lines from a complete black out in case of a short circuit which might happen at any socket. Practically, and in many cases, more than two to three sockets are connected to one circuit breaker in the main panel, so that when one of them is subject to overload or short circuit, the complete set will be out. There are trip circuit breakers, medium voltage and high voltage fusebreakers and for every type there is a rating for both voltage and current.



So what has this to do with our socket? You just have to make sure that any appliance, equipment, tool, etc connected to any socket at the wall should have electrical current rating below the circuit breaker current rating. Normally, all electrical appliances at home are far away below the circuit breaker rating. So don’t worry about a circuit breaker.

Now, lets move to the socket.. Sometimes the wiring inside the socket itself “inside the wall” is not properly connected and here we might have a problem. The problem happens when a high load is connected to the socket like a refrigerator or air conditioner which has at least 1500 Watt. The wires inside the socket start to heat up and then boom! the socket is burned out and if you’re lucky no fire is there.

So my advice to you is to go and double check the wiring inside every socket just to make sure all sockets are okay.

The last part you should take care of is the plug extension cable. Take this example, a microwave oven rated at 220V/2000Watt connected to a good wired socket that is linked to a perfect rated circuit breaker of say 250V/20A. Now, to refresh our minds with power formula from physics:

Power (Watt) = Current (Ampere) × Voltage (Volts)

In this example: the circuit breaker power = 250×20=5000Watt  which is greater than the 2000 Watt of the microwave and this means our microwave operates on the safe side.

Say I bought an extension cable rated at: 220V/8A this means the power is 1760Watt.

Here comes the beautiful part, if we connected our microwave (2000Watt) to this (1760Watt) extension  we are then overloading it and it might take just few min. and the extension is burned out! You start then smelling some plastic perfume coming out of your extension cable.

powerThis is because the 1760 Watt is lower than 2000 Watt needed for our device.

Our lesson today is then: when you buy extension cables, watch out for electric current rating! Always take 25% of your load rating.

Another important factor that people of  Saudi Arabia forget to consider is : Operating temperature! Guys, last summer I measured around 50 C ! Can you imagine which product can withstand this high temperature?

Usually, manufacturers mention the operating temperature  & storage temperature of cables and that is truly what makes a cable expensive than the other. So always use industrial rated cables!

Out in the market, you’ll find tens of cheap products that claim high current/high operating temperature and they are not! So spend more pines and save your products at home.

One last note, some extension cables are more sophisticated and contain surge arrestors: Metal Oxide Varistors (MOV), that protect your loads against spikes, surge lightning. Don’t buy these ones unless your enviroment might be subject to lightning and surges like a cabinet in the middle of a desert.

Finally, I recommend you to buy cables from the following shops:

1. Mejdaf: Local Saudi distributor for electronic components and int’l brands. You’ll find many nice professional products. Click here

2. SACO-KSA: One of the best shops also for those who like to build their own workshops. Click here




Posted in إلكترونيات

Eye-Fi: Wireless SD card!

How many times have you transferred your photos from your memory card of your digital camera to PC? Would it be easier if I told you let’s do it remotely?

Welcome to Eye-Fi card 🙂


The Eye-Fi card is the 1st wireless memory card. It looks, stores media, and fits into cameras just like a regular SD/SDHC card. On top of that, the Eye-Fi card has built-in Wi-Fi that uses your wireless network to effortlessly transfer photos and videos.


[youtube=http://www.youtube.com/watch?v=dRM3Uje2gjM&feature=player_embedded]

It costs $79.99! You can buy it from here.

Posted in إلكترونيات

A Carpet + Human body = Radio!

It always inspires me when I watch amazing ideas that turn a simple concept into a useful consumer product. Today, I was watching this

[vimeo vimeo.com/5334661]

that shows how you can turn your body into an antenna!

DSC_2711

Yes, that’s true! The project is basically a carpet made of looms from conductive thread. By standing on the carpet, your body acts as an antenna. The carpet picks up the radio waves, which your body receives and makes them hearable. When walking on the carpet you can tune it to a certain frequency, like the tuner of a radio.

The designer of this cool idea is Florian Kräutli

He is a Swiss designer, working in The Netherlands.

He has designed some pretty good stuff.

Let’s think out of the box!