Choosing an electric screwdriver
Before giving specific advice on choice, let us first clarify what you need the tool for. According to their purpose they are divided into household and professional.A household electric screwdriver is designed for occasional use. That’s why electric tools are designed to be relatively cheap, low-powered, compact and lightweight. In favor of a low price and less weight they often sacrifice functionality. For example, drilling or even drilling with a hammer function is often present in more expensive models of household screwdrivers. Constant use or heavy use leads to premature wear and tear of the inner workings of the tool.Professional electric screwdriver is designed for frequent use, has an increased internal wear life. Professional models are noticeably more powerful, have higher battery capacity and functionality. They can undo any screw, and they can even make a hole in plaster with a hammer drill. It makes sense to buy a professional electric screwdriver if you need it for work. There is also such a kind of tool as electric screwdrivers. Smaller size and less power than a traditional electric screwdriver. They are designed for tightening/screwing in hard-to-reach places, which a standard electric screwdriver cannot reach. Electric screwdrivers cannot drill.
Which battery is better in lithium or nickel cadmium?
This question about what battery is better for an electric screwdriver is not precisely posed. It all depends on the situation and the length of time for which the tool will be used.
The variety of battery packs is due to the fact that different chemical elements can be used as electrodes and electrolytes. On the right choice of energy storage depends on the quality of operation of the power tool used. The following 3 types are the most common in the field of power tools:
Lithium battery pack weighs less for the same capacity as cadmium. But this is not the main indicator on the basis of which you should choose a battery for an electric screwdriver.
Of course, the number of charge-discharge cycles for cadmium cells is many times less than for lithium cells. The standard for Ni-Cd is 500, and for Li. 1500, which, of course, at first suggests that lithium batteries are much better and lighter in weight.
When choosing batteries it is important to consider the fact that the aging of nickel cadmium batteries depends solely on the cycles they have completed, not their actual age!
The service life of lithium ion batteries, in contrast to cadmium batteries, depends directly on the age of the battery pack. After 3 years they are already out of service, even if they have not been used.
Nickel-cadmium batteries, on the other hand, will last a long time even if they are rarely used.
For example, when buying a used electric screwdriver, do not get one with lithium batteries. There is a good chance that if the tool has not been used for a long time, or has been subjected to frequent freezing, its battery pack is no longer fit for use.
If, on the other hand, a “screwdriver” is sold with cadmium batteries, they can retain up to 60% of their charge, regardless of whether the tool was working or not.
If an electric screwdriver is not used very often, lithium batteries are more likely to “age” than serve their intended 1,500 cycles. Therefore, for occasional domestic use, it does not make sense to buy a tool with lithium batteries.
Cadmium can last from 3 to 5 years, whether the batteries are used or not. It can also safely lie in storage, preserving its properties, unlike lithium. Unless you plan to use your electric screwdriver often, the answer to the question of how to choose a battery is short and true: choose cadmium.
By the way, at freezing temperatures of up to.20°C cadmium “behaves” better than lithium batteries, which do not like extreme cold. Lithium should be kept at least 60% charged. They need constant recharging when not in use. Otherwise, they begin to deteriorate.
So it’s clear that nickel cadmium batteries are in fact no worse than lithium batteries. The main issue is only in the scope of application of both types of chemical batteries.
When used at the right time and in the right place, both can be equally useful and good.
Nickel─metal hydride batteries are less common than nickel cadmium batteries for screwdrivers.
Their advantages are the absence of toxic components, environmentally friendly production, little “memory effect” and lower self-discharge than that of Ni-Cd batteries.
In addition, when compared to Ni─Cd batteries, nickel─metal hydride batteries have a higher capacity and withstand a greater number of charge-discharge cycles.
Ni-MH batteries have the following advantages
- They have almost no memory effect;
- No toxic components are used in their production;
- easy disposal; capacity 30% higher than that of nickel-cadmium; light and compact; not afraid of mechanical damage.
- long charge; 500-600 charge-discharge cycles;
- after 300 cycles it is possible to observe a decrease in capacity;
- can not be operated at negative temperatures;
- Can not be fully discharged; higher cost than the previous type.
Nickel-metal hydride batteries should be stored half charged and in a cool place.
Lithium-ion (Li-ion). The most advanced batteries
Thinking about how to choose a cordless electric screwdriver, we should note that the most modern lithium-ion batteries also have their advantages and disadvantages.
- Low weight and size;
- Specific capacity is twice as high as that of Ni-Cd;
- no memory effect;
- High number of charge-discharge cycles (up to 700);
- low self-discharge: (3-6% per month);
- Easy maintenance (do not require strict observance of charge and discharge modes);
- fast charging (30-40 minutes on average).
They also have disadvantages, and they are quite serious:
- Do not work at negative temperatures;
- Do not recover;
- Low life span (maximum 2 years). over, the battery age is not counted from the date of commissioning, but from the date of production (so buy only “fresh”).
- Explosion and fire hazard;
- Completely discharging them will damage the battery (trying to recharge them again can cause them to explode);
- Sensitivity to overheating and shocks;
- High cost.
Another important nuance to remember is the storage of a cordless electric screwdriver. Nickel-cadmium batteries can be stored in a discharged state. Nickel-metal hydride, on the contrary, before long storage (several months) it is necessary to charge it fully.
Lithium ion batteries should be mentioned separately: they do not care whether you store them charged or discharged. However, remember that they “age” rather quickly. Therefore, buy a tool with such power sources not for one-time work, but for intensive use. After only 1 year a lithium battery will lose about 30% of its original capacity, and after 2 years the battery will have to be thrown away.
How to choose a drill. electric screwdriver
If you are reading this article, it means that you are confused by the variety of tools, which are presented in the Internet and offline stores. We will not push you to choose a particular brand, but only explain what parameters you need to pay attention to when choosing a cordless drill-electric screwdriver.
In this article we will pay more attention to the tool for domestic purposes (for home work), t.к. Professionals know without us which tool to choose.
How to choose a screwdriver. what characteristics to pay attention to
Modern technology, equipment and tools have greatly simplified some construction operations. This is especially true in processes where brute human force is used. For example, tightening/unscrewing screws or bolts. There’s a problem today. screwdrivers. We understand. how to choose an electric screwdriver, what characteristics you should pay attention to.
The body of an electric screwdriver
The power tool is “packed” in a housing made of plastic, a material that has the following advantages:
- Plastic acts as a natural insulator against electricity, it does not conduct electricity. Consequently, it is safe.
- It is lighter than metal, and thus reduces the weight of the tool.
- And finally, in production, it is easier to give the necessary shape to plastic than to metal.
The body is divided into three parts. The upper part contains all the rotating mechanisms. Handle with soft pads. By it the master holds the tool in the process of work. The pads reduce shock absorption, making it more comfortable and easier to work. The lower part, the support, inside which is the compartment for storing bits.
Power supply for cordless screwdriver
An acquaintance asked me to build an outdoor power supply for the screwdriver. Together with a screwdriver (fig.1) I brought a power transformer from an old Russian burner-grinder “Ornament-1” (fig.2). see if it can’t be used?
At first, of course, we disassembled the battery compartment, looked at the “banks” (fig.3 and Fig.4). At first we disassembled the battery compartment and looked at how each “bank” was working (fig.1). With the charger we checked how each “bank” worked by several charge-discharge cycles. Out of 10 of them, only 1 was not bad and 3 were more or less ordinary, while the rest were dead. Means, exactly have to make an external power supply unit.
READ What electric screwdriver is suitable for ice drills
To assemble the power supply, you need to know what current draws the screwdriver in operation. After connecting it to the laboratory source, we find out that the engine starts to rotate at 3.5 V, and at 5-6 V there is decent power on the shaft. If you press the trigger when it receives 12 V, it triggers power supply protection. which means that the current consumption exceeds 4 A (protection is set to this value). If you start the screwdriver on a low voltage, and then increase it to 12 V. it works fine, the current consumption of about 2 A, but at the moment when the screwdriver goes halfway into the board, the power supply protection has worked again.
To see the complete picture of the current consumption, we connected the screwdriver to the car battery and put a resistor of 0,1 Ohm in the gap of the plus wire (Fig.5). The dropping voltage was fed into a computer sound card with an open input and for viewing we used the program SpectraPLUS. The resulting graph is shown in figure 6.
First pulse on the left is the starting pulse at power on. You can see that the highest value is 1.8 V and it indicates a current flow of 18 A (I=U/R). Then, as the engine speeds up, the current drops to 2 A. In the middle of the 2nd second the head of the screwdriver is clamped by hand until the “ratchet” engages. the current at this time rises to about 17 A, then falls to 10-11 A. At the end of the 3rd second the start button is released. It turns out that to work the screwdriver requires a power supply with the ability to give 200 watts of power and current up to 20 amps. But, considering that the battery compartment says that it has 1.3Ah (Fig.7), then, most likely, everything is not as bad as it seems at first sight.
Let’s open the burner power supply and measure the output voltages. The highest is about 8.2 V. Not enough, of course. Taking into account the voltage drop across the diodes of the rectifier, the output voltage across the filter capacitor will be about 10-11V. But there is no way out, let’s try to assemble the circuit according to Fig. 8. The diodes used are KD2998B (Imax=30A, Umax=25V). Diodes VD1-VD4 are mounted hinged on the pins of burner contact sockets (fig.9 and Fig.10). As a high-capacitance capacitor we used a parallel connection of 19 pieces of smallest capacitance. the whole “battery” is wrapped with masking tape and the capacitors are selected to such a size, that the whole bunch could hardly penetrate into the battery compartment of the screwdriver (fig.11 and Fig.12).
In the burner is very awkwardly stand a fuse block, so it was removed, and the fuse is tucked “directly” between one of the wires 220V and the lead of the interference suppression capacitor C1 (Fig.13). When closing the housing, the power supply cable is tightly crimped by a rubber ring and this prevents the wire from dangling on the inside when bending it from the outside.
Checking the performance screwdriver showed that everything is working fine, the transformer after half an hour of drilling and screwing screws is heated to about 50 degrees Celsius, diodes are heated to the same temperature and the radiator is not needed. The screwdriver with such a power supply has the lowest power in comparison with charging it from the car battery, but this is understandable. the voltage at the capacitors does not exceed 10.1 V, and during the growth of the load on the shaft is further miniaturized. By the way, decently “lost” on the supply wire length of about 2 meters, even using its cross section of 1.77 square.mm. To check the drop on the wire, a circuit was made according to Fig. 14, and the voltage across the capacitors and the drop on one conductor of the power wire was monitored. The results in the form of graphs at different loads are shown in Fig. 15. Here in the left channel is the voltage at the capacitors, in the right channel. the drop on the “minus” wire, going from the rectifier bridge to the capacitors. you can see that when you stop the screwdriver head with your hand, the supply voltage drops below 5V. At all this the power cord drops about 2,5 V (2 times 1,25 V), the current is pulsed and is connected to the work of the rectifier bridge (fig.16). Changing the power cord to another one, with a cross section of about 3 sq.mm resulted in increase of heating of diodes and transformer, that’s why we reversed the old wire.
We looked at the current between the capacitors and the screwdriver, using the circuit shown in Figure 17. The resulting graph is in Figure 18, “chunky”. is the ripple at 100 Hz (same as in the last 2 drawings). You can see that the starting pulse exceeds the value of 20 A. most likely this is due to the least possible internal resistance of the power supply because of the use of parallel connection of capacitors.
At the end of measurements have looked at the current through the diode bridge, having switched between it and one of the leads of the secondary winding resistor 0,1 Ohm. The graph in Fig.19 indicates that when braking the motor, the current reaches the value of 20 A. In Fig.20. time-spanning section with the highest currents.
Which Type of Motors Used in Drill Machine? || Electro Repaireing
As a result, we decided to work with a screwdriver with the power supply described above, but if there will be “not enough power”, it will be necessary to find a more powerful transformer and put diodes on the radiators or change to other.
And of course, you should not take this text as dogma. there is absolutely no obstacle to the production of PSU by any other circuit. For example, the transformer can be changed at ТС-180, ТСА-270, or you can try to power up a screwdriver from a computer pulse PSU, but most likely the ability of a 12 V circuit to give out current of 25-30 А would be useful to check.
What are they and what are they for??
An impact electric screwdriver is a special power tool that allows the most efficient drilling of walls for the purpose of screwing in screws and installing other fasteners. Unlike the hammerless models, this relative novelty on the domestic market makes a hole not only through the rotation itself, but also through directional blows. The latter usually do not have a permanent nature. the appropriate mode is turned on at will of the operator or automatically if the drill bumps into an obstacle of particular hardness. In a sense, it is a small demolition hammer.
An electric impact screwdriver is a more complex and “smart” device in itself, so a certain versatility should not surprise. This means that the tool is usually fully compatible with various attachments, so that the scope of its potential applications is significantly expanded. instead of a drill, you can attach, for example, a circular saw or a mixer attachment.
A distinction should be made between an electric impact screwdriver and such a drill. The latter, being focused on making holes, assumes a longitudinal direction of blows, while the electric screwdriver beats as if in a longitudinal direction, due to which it significantly increases the torque.
It is logical that such a tool is somewhat more expensive than hammerless models, but its purchase is often justified even in the home. the external, load-bearing walls of multi-storey buildings usually have the highest strength, which only an electric impact screwdriver can overcome.
The device is also appreciated by professionals who drill walls or various parts every day. in their words, for all its assertiveness drill impact electric screwdriver usually does not cause significant damage to the elements of fasteners, increasing their longevity. This characteristic is especially valuable in the context that the same tool is often used for furniture assembly.
The classification of impact screwdrivers is not so extensive, but still able to baffle many inexperienced consumers. the most confusing logic in the division of tools into drills, screwdrivers and screwdrivers, but in fact everything is very simple: the mechanism is generally the same for all, and the exact name depends on the nozzle.
For example, a drill is usually equipped with a drill bit for making holes, while an electric screwdriver and a screwdriver also know how to screw fasteners. Some models assume a simple change of attachments, so they can have complex compound names like “electric screwdriver-drill”, but if such versatility is not provided, the unit is called the most accurate term.
Often beginners are also confused when choosing between electric and pneumatic screwdrivers. Electric models are the most common, especially in the home, but the pneumatic. is except that very rare models, which at home just will not be in demand, the main places of their use. different stations and tire companies.
Since the electric screwdriver is powered by electricity, it is impossible not to specify that it can be both networked and cordless. The former is good for small home repairs or daily work in a well-equipped workshop, because it is lighter, and the handyman does not have to constantly remember to charge the battery.
However, the battery version is the only solution during construction or for outdoor use when the work site does not imply the presence of functioning outlets.
Speed regulator: a little nuance
The speed regulator is also made according to a very simple scheme. It involves pulse-width controller and a switch, which is made on the basis of a field-effect transistor. As for the control, it uses a variable resistor. Its resistance, and therefore the speed of rotation, is directly related to the force of the push button. It is also sometimes called a trigger. Reversing in this case only affects the direction of the voltage applied to the motor. Here, special flip contacts are used for this purpose. The whole process is automated, so a person does not have to do anything manually.