One of the most frequent causes of breakdowns in our computers is the power surges of the electricity network, which is why we often consider acquiring some device to protect our equipment.
In general, rises to occur when an active phase changes a neutral period in some line repair and shake our houses with no less than 380 volts. The sources of the computers hold almost all with enough security until the 250 V, but not much less 380 V as it occurs in many cases.
In this article, we address how to make economic but adequate protection for these cases; it involves mounting varistors in parallel with the cables that power our computer.
A small theoretical explanation
Varistors are variable resistors by voltage. That is, up to 250 V (in this case) will not let any current pass through it, while when they exceed 250, V will become conductive, leaving current flowing between their terminals.
Therefore, if we put some varistors between the power cables, we will feed our computers regularly. Still, if the voltage rises dangerously (exceeding 250 V), they will become conductors and short-circuit the phase with the neutral or the stage with the grounding, so that will make the jump the protections of our house cutting the current.
That is to say; we will create a kind of “momentary electrical breakdown” that will blow up what is usually called the “automatic” or the “plumbers,” but which are technically called the differential switch and the magnetothermal switch, which is nowadays forced use in all homes.
Hands-on, we will need three varistors of 250 V and approximately 50 A. An extension cord with several plugs, which will be where we connect the computer and its peripherals. A little heat-shrinkable macaroni. A small plastic box, and a splice tab.
All these components can be found in any establishment of electronic components at very affordable prices.
The varistors come out for about 100 pts unit, the box about 400, the heat-shrinkable macaron about 200 as a strip of one meter, and perhaps the most expensive is the power strip, about 1,000 pesetas.
For this assembly, we have taken advantage of a simple strip, but we recommend one with a switch.
First steps and more theory
Preparation of the box: it does not have significant difficulty, we will perforate by the two ends so that it can pass the feeding hose (7.5 mm approx) and make the connections inside the box.
Then we will peel the hose exposing the three internal conductors (being very careful not to cut the insulation of the inner cables ), and peel the tips of the same leaving the bare copper cable to make the connections in the splice tab.
We already have the cables connected to the card, each one with its color.
The three conductor cables that we appreciate in the photograph are:
- The active phase ( brown or black cable on some occasions), this phase is the one that carries the 250 V of alternating voltage, that is to say, that between this phase and the neutral or earth, the 250 V circulate. This clarification is useful for any device or an electrical connection box. We must be cautious when working with this phase in any repair of plugs or home switches because if we make contact with it and the floor, circulate the 250 V through our body.
- The neutral (always blue ) is the 0 Volt connector, that is, it is the one that creates the potential difference with the phase so that the 250 V circulate among them. With this one, there is no need to have so many looks because Take positive tension, will not give us cramps “rarely.” (Just in case we have to prevent because in outdated facilities we do not know what we can find, nor if the color code has been respected.)
- The earth connector (always yellow and green ), is the conductor to discharge the voltage that may come to circulate when there is a leak due to a fault. It is an excellent connection to 0 V, so if we touch the broken device, the leakage voltage that it has will go through the ground conductor, saving us from an unpleasant and dangerous discharge.
At the entrance of our homes, we have a small electrical panel with a differential switch, and at least one circuit breaker. The differential has a lever to activate it again and a test button, and the magnetothermic has a fatter bar that goes up to connect and low when jumping or disconnected.
In this way, if a short circuit occurs (joining the brown and blue wires between them), there would be excessive consumption, the magnetothermic would overheat and jump. But for the use to be raised because of a device, in our case, the computer means that the magnet will jump when our laptop may already be done a penalty, and the damage is already irreparable. So we are going to mount a varistor between the two, so if the voltage rises above 250 V, it will become conductive, causing a cut between the phase and the neutral, instantly jumping our magnetothermic.
Disadvantages? That some sporadic time the voltage limit is exceeded, we will have a momentary blackout in the whole house, but we will save our equipment quickly from an overvoltage that could damage it more than a power cut and a Scandisk when starting again.
Another way would be that the neutral (blue) or the phase (brown) made contact with the ground connector (yellow-green), in this case, the differential switch or “lifesaver” would come into operation. Nowadays, it is a mandatory assembly in any low voltage electrical installation.
How does it work?
As he is the security guard of the house, he continually verifies that the current that flows through the phase (brown), returns through the neutral (blue); thus, when there is a loss of current for any reason (a discharge to a person, or ground due to a breakdown), it automatically jumps and can not be activated until the loss ceases.
They are so sensitive that sometimes, in old installations, they come to jump by the rain, since the humidity produces leakage of current. But the important thing is that if for any reason, any of us receive an electric shock, the differential would jump safely, saving a life.
In this way, we are going to take advantage of this valuable homemade device to make it jump if the tension rises.