A cordless screwdriver is a necessary thing in the household, the main advantage of which is its mobility. However, with prolonged use, the tool requires regular recharging, which is very inconvenient. In addition, old batteries fail, and buying new ones is unprofitable or even impossible, since the model can be discontinued. A rational solution is to build a constant power source for the screwdriver.
Advantages and disadvantages of remaking
Before you begin, you should evaluate all the pros and cons of upgrading the tool from battery to network. The main drawback is the loss of mobility, which is not always convenient for working at height or far from the outlet. As for the merits, here we can highlight several positive factors:
- the problem of suddenly discharged batteries disappears;
- stable torque;
- no dependence on the temperature regime (at low values, the batteries discharge faster);
- saving money on buying new batteries.
Modernization is especially relevant when the "native" batteries are out of order, and the new ones are either not on sale or you need to travel far behind them. It also happens that the purchased device has some problems when receiving energy from the battery. This may be a marriage or a flaw in the circuit of the model itself. If, in principle, the tool suits, then it is advisable to redo it and carry out charging from the network.
Power Supply Options
Since a screwdriver requires a voltage much lower than in a centralized network, an electric adapter is needed for a power tool - a power supply that will convert 220 volts to 12, 16 or 18 volts of constant value. There are several power supply options.
Pulse devices - inverter system. Such power supplies first rectify the input voltage, then convert it to high-frequency pulses, which are supplied either through a transformer or directly. Feedback voltage stabilization is achieved in two ways:
- due to the output transformer winding in the presence of sources with galvanic isolation;
- using a conventional resistor.
Experienced craftsmen give preference to a switching power supply, since it is small-sized. Compactness is achieved due to the lack of a power transformer.
Such a power source, as a rule, has a rather high efficiency - about 98%. Impulse blocks provide protection against short circuit, which ensures the safety of the device, as well as blocking in the absence of load. Among the obvious disadvantages, the main thing is lower power compared to the transformer version. In addition, the operation of the device is limited by the lower load limit, that is, when the power is below the permissible level, the power supply will not work. Users also note an increased level of repair complexity compared to a transformer.
Transformers are considered a classic version of the power supply. A linear power supply is a symbiosis of several components.
- A step-down transformer. The winding of the power device is designed for mains voltage.
- Rectifier, the function of which is to convert the AC network to DC. Two types of rectifiers are distinguished: half-wave and half-wave. As part of the first 1 diode, in the second - a diode bridge of 4 elements.
Also, the scheme may include other components:
- a large capacitor necessary for smoothing the ripple, located after the diode bridge;
- a stabilizer, which causes a constant output voltage, despite any surges in the external network;
- protective block against short circuits;
- high-pass filter to eliminate interference.
The popularity of transformers is due to their reliability, simplicity, the possibility of repair, lack of interference and low cost. Among the shortcomings are only bulkiness, high weight and low efficiency. When choosing or self-assembly of transformer power supplies, it should be borne in mind that the output voltage should be slightly higher than the required tool. The fact is that part of it is taken away by the stabilizer. For example, for a screwdriver powered by 12 Volts, a transformer power supply with an output voltage value of 12-14 Volts is selected.
When buying or self-assembling a power supply, they are always repelled from the necessary technical parameters.
- Power. Measured in watts.
- Input voltage. In domestic networks, 220 volts. In other countries of the world this parameter is different, for example, in Japan 110 Volts.
- Output voltage. The parameter required for the operation of a screwdriver. It usually varies from 12 to 18 volts.
- Efficiency. Reflects the performance of the power source. If it is small, then most of the converted energy is used to heat the body and parts of the tool.
Necessary materials and tools
The following tools can be used to upgrade a cordless screwdriver :
- screwdrivers of various types;
- construction knife;
- tape insulation;
- electric cable (preferably multi-core), wire for jumpers;
- a soldering station including a soldering iron, solder and acid;
- case box for the power supply, which can be an old battery, a factory-made device, a home-made box.
When choosing a box, you need to take into account the dimensions of the power supply design so that it fits inside the device.
How to do it yourself
In order for the screwdriver to work from a network with a voltage of 220 volts, it is necessary to build a power supply unit that outputs 12, 14, 16 or 18 volts depending on the model of tool. Using the existing case of the battery charger, you can make a network charge, performing the steps in the following sequence.
- Determine the dimensions of the housing. The network unit must be made so that it fits inside.
- Small-sized sources are usually placed in the body of the screwdriver itself. To do this, disassemble the battery and remove all the insides. Depending on the model of the tool, the housing can be collapsible or glued. In the latter case, you will have to open the tool at the seam with a knife.
- Using marking, we determine the voltage and current strength. As a rule, manufacturers do not indicate the last parameter, but instead there is such as power, or full electrical load, expressed in watts. In this case, the current strength will be equal to the quotient of the division of power by electric voltage.
- At the next stage, the wires must be soldered to the contacts of the charger. Since the terminals are usually made of brass and the cores are made of copper, this task is difficult to accomplish. For their connection, special acid is used, which is treated with a brass surface before soldering.
- The return ends of the wire connect to the battery outlet. An important point is the observance of polarity.
In order for the power supply to work correctly, you must connect the cable with the following rules:
- a hole is made in the structure to get a wire there;
- cable fixing inside the housing is carried out using electrical tape.
Of course, it would be easier to connect to the network directly using a plug and socket. However, in this case, the device will refuse to work. Firstly, because it is designed for a constant small voltage, and in the network an alternating and large one. Secondly, it’s safer. The necessary elements for the electric circuit (diodes, resistors, etc.) can be bought, or you can borrow from unnecessary household appliances, for example, from an energy-saving lamp. It happens that the power supply is more appropriate to do completely with your own hands, and sometimes it is better to buy a ready-made one.
The easiest way to assemble a charger is to use a housing from a native battery that has become unusable. In this case, either a 24 Volt Chinese power supply, or some ready-made PSUs, or a power supply of its own assembly will be useful for internal filling. The beginning of any modernization is the electrical circuit. It is not necessary to draw it according to all the rules, it is enough to depict the sequence of connecting parts by hand. This will reveal a number of elements necessary for work, and will also help to avoid mistakes.
Alteration BP Chinese-made
A similar source is designed for an output voltage of 24 volts. It can easily be bought at any retail outlets with radio components, it is affordable. Since most of the screwdrivers are designed for operating parameters from 12 to 18 Volts, it is necessary to implement a circuit that reduces the output voltage. This is pretty easy to do.
- First of all, you should unsolder the resistor R10, which has a constant resistance of 2320 ohms. It is responsible for the magnitude of the output voltage.
- Instead, an adjustable resistor with a maximum value of 10 kOhm should be soldered. Since the power supply protection is integrated in the power supply unit, before installing a resistor, it is necessary to install a resistance of 2300 Ohms on it. Otherwise, the device will not work.
- Next, the unit is supplied with electricity. A multimeter determines the values of the output parameters. Remember to set the meter to a constant voltage range before measuring.
- Using adjustable resistance, the required voltage is achieved. By using a multimeter, it is necessary to check that the current does not exceed 9 amperes. Otherwise, the converted power supply will fail, as it will experience large overloads.
- The device is mounted inside the old battery, having previously removed all the insides from it.
Alteration of purchased blocks
Similarly, the Chinese device can be built into the battery box and other off-the-shelf power supplies. They can be purchased at any radio parts store. It is important that the selected model is designed to work with a 220 Volt network and has a suitable operating voltage at the output. Modernization in this case will be carried out as follows.
- First, disassemble the purchased device.
- Next, the design is redone for the necessary parameters, similar to the reconstruction of the Chinese power source described above. Solder resistance, add resistors or diodes.
- The length of the connecting wires should be selected based on the dimensions of the battery compartment of the power tool.
- Carefully isolate soldered areas.
- It is better to equip the board with a radiator for cooling.
- It is more expedient to place the transformer separately.
- The assembled circuit is mounted inside the battery compartment and fixed. For reliability, the board can be glued.
- Connect an electric cable taking into account polarity. All conductive parts must be insulated to avoid short circuits.
- Several holes must be drilled into the housing. One is for the outlet of the power cable, the other is for the removal of hot air, to ensure circulation and reduce the degree of heating of the screwdriver during operation.
- Upon completion, check the operation of the device.
Self-designed power supplies
Parts for assembly are taken either from various household electrical appliances or energy-saving lamps, or purchased at amateur radio outlets. It must be understood that the electrical circuit will also depend on the set of elements. Its assembly requires certain radio engineering knowledge and skills. Graphic options for schemes can be found on the Internet or in specialized literature.
In the simplest case, you need a ready-made electronic transformer with a power of 60 watts. Experts advise choosing a device from Taschibra or Feron. They do not need alteration. The second transformer is assembled by hand, for which a ferrite ring is purchased, the dimensions of which are 28x16x9 mm. Then corners are ground using a file. Upon completion, it is wrapped with electrical tape. As a board, it is better to choose an aluminum plate with a thickness of 3 mm and above. It will not only carry out the supporting function of the base for the entire circuit, but also simultaneously conduct current between circuit elements.
Professionals recommend incorporating an LED light bulb into the design as an indicator. If its dimensions are sufficient, then it will also perform the task of highlighting. The assembled device is fixed in the battery of the screwdriver. When designing, it must be remembered that the dimensions of a home-made power source must in no case exceed the dimensions of the battery pack.
Remote power supplies can be designed based on the power supply from a laptop or computer.
From computer PSU
As a rule, craftsmen use AT-type blocks. They have a power of about 350 watts and an output voltage of about 12 volts. These parameters are enough for the normal operation of the screwdriver. In addition, all technical specifications are indicated on the housing, which greatly simplifies the work of adapting the power supply to the tool. The device can either be borrowed from an old computer, or bought in a computer salon. The main advantage is the presence of an on / off switch, a cooling cooler and a protective system against overloads.
The following is the sequence of actions.
- Dismantling the case of the computer unit.
- The elimination of protection against inclusion, which consists in connecting the green and black wires that are present in the specified connector.
- Work with the MOLEX connector. It has 4 wires, two of which are not needed. They must be cut off, leaving only yellow at 12 volts and black - grounding.
- Soldering to the left wires of an electric cable. Particular attention should be paid to insulation.
- Dismantling a screwdriver.
- Connection of tool terminals to the reverse end of the power cable.
- Tool assembly. It must be ensured that the cord inside the screwdriver case does not twist and is not tightly pressed.
As a disadvantage, the adaptability of such a power supply unit only for an instrument with an operating voltage of not higher than 14 volts can be highlighted.
The power source for a screwdriver can be a laptop charger. Its refinement is minimized. It should be noted that any device with 12-19 volts is suitable for use. The action algorithm is as follows.
- Preparing the output cord from the charger. With the help of wire cutters, the connector is cut off and the ends are stripped of insulation.
- Dismantling the tool body.
- The bare ends of the charger are soldered to the terminals of the screwdriver, observing the polarity. You can use special plastic ties, but professionals advise you not to neglect soldering.
- Isolation of compounds.
- Assembly tool body.
- Performance Testing.
Alteration of the finished charger is simpler and accessible to everyone.
An excellent option for powering a screwdriver is a car battery. Especially in cases where repair is required in an area devoid of electricity. The negative point is that the tool can be powered from the car battery only for a short time, since the vehicle runs the risk of discharging and will not move. To start a screwdriver, an old analog-type car battery is sometimes redone. Such a device is characterized by manual control of the current strength and output voltage.
Instructions for modernization.
- At the first stage, you should choose a pair of multicore cables. It is desirable that they be in a winding of a different color for distinction, but of the same cross section.
- On the one hand, wires are attached to the wires in the form of "crocodiles", on the other hand, they strip the insulating layer by 3 centimeters.
- The bare ends are crocheted.
- Next, proceed to disassemble the screwdriver case.
- Find the contact terminals by which the tool is connected to the battery. The bent stripped ends of the cable are soldered to them. You can do without soldering, using special plastic ties, but professionals prefer a soldering iron.
- The connections must be well insulated, otherwise there is a risk of short circuiting.
- Both ends of the cable are neatly laid inside the housing and out through the handle. You may need to drill additional holes for this.
- Next, assemble the tool.
- After all the manipulations, the device is tested. With the help of "crocodiles" a screwdriver is connected to a car charger, observing "+" and "-".
Such an analog power supply is convenient in that it allows you to smoothly adjust the parameters, adjusting to any model of a screwdriver.
Inverter welding machine
Creating a power source from inverter welding is a more complex type of modernization, since it implies the presence of certain theoretical knowledge in the field of electrical engineering and practical skills. Alteration entails structural changes in equipment, which will require skills to make calculations and draw up diagrams.
When working with any electrical device that has undergone modernization, certain safety rules must be observed.
- First of all, when remodeling, in no case should you neglect the good insulation of the contacts and grounding.
- The screwdriver needs short breaks every 20 minutes. During the alteration, the technical characteristics changed, which were laid down by the manufacturer and were designed to work on battery power. The increase in power led to an increase in the number of revolutions, which causes the tool to heat up. Small breaks will extend the life of the screwdriver.
- It is recommended that you clean the power supply regularly from dust and dirt. The fact is that during the modernization, the tightness of the case was broken, so pollution and moisture get inside, especially when working in the open.
- The power cable must not be twisted, pulled or pinched. It is imperative that you ensure that it is not exposed to any negative influences during operation that could lead to a circuit.
- Experts do not recommend using a homemade power screwdriver at a height of more than two meters. Since this automatically entails pulling the wire under its own weight.
- When adjusting the output parameters, it is necessary to select a current of 1.6 times greater than the electric capacity of the battery.
- You should know that when a load is applied to the device, the voltage can decrease from 1 to 2 Volts. In most cases, this is not important.
These simple recommendations will extend the life of the screwdriver and protect its owner from trouble.
As practice shows, the independent alteration of the power supply requires experience and good theoretical knowledge in electrical engineering. Therefore, before choosing it is necessary to decide whether you are ready to spend your free time drawing up a circuit, assembling a power source, especially in the absence of proper skills. If there is no confidence, then experts advise buying ready-made chargers, especially since their cost in the market is low.
About how to make a network screwdriver network, see the next video.