How to make an 18 volt mains powered electric screwdriver

How to turn a cordless screwdriver into a cordless screwdriver

The cordless electric screwdriver was created primarily to provide mobility. It’s much more convenient to work with the tool without worrying about whether the wire is long enough, whether it gets snagged, etc. д.

But without batteries, such a handy tool like an electric screwdriver becomes a simple piece of metal, even though it is fully functional. Battery life is about 3 years, and it is often impossible to find a complete or similar ones on sale. For example, the manufacturer has already stopped producing such a model, and other batteries do not fit according to different parameters.

It is a shame to throw away a tool that you have paid money for, sometimes a lot of money, at the time. Besides, the cost of batteries is often up to 80% of the price of an electric screwdriver, and it would make more sense to buy a new tool. As a rule, an old tool is sent to a distant shelf and remains there without any use. But there is a way to make it work again, to convert it to 220 volt power supply.

Is mobility important?

Once the rechargeable battery becomes incapable of holding a charge, the electric screwdriver becomes a completely useless tool. Buying a new charger is not reasonable, because its price is often up to 50% of the price of a new model. So the idea of converting your tool to mains power is perfectly justified.

It is possible to restore the characteristics of the battery, but this option is still a half-measure, because in the future the situation will be repeated. But before choosing a solution, it is necessary to consider what to do with the mobility of the tool. Is it so necessary? There are 2 options for the potential modification of an electric screwdriver:

  • A tool with an external power supply. In this case a separate device is made. This is not so bad, because even the bulky construction can be placed in close proximity to a socket. But you have to put up with the limitation associated with the length of the power supply cable and the mains cord.
  • An electric screwdriver with a PSU built in place of a battery. This way of modification will give the opportunity to avoid the assembly of a bulky structure, significantly limiting the use of the tool. But in this case the length of the network cable can also pose an access problem. But it is possible to use compact devices in this way. They can be purchased or existing power supply units, if they fit the characteristics.

The ways to “revive” an electric screwdriver are very different. Nevertheless, each of these options finds supporters, as it meets the different needs of owners of cordless tools, whose operation has suddenly become impossible.

Basic materials:

To transfer the power of an electric screwdriver from the battery to the mains, you need to get to its power contacts. To do this, you need to disassemble the body of the battery pack. The batteries present in it are removed.

Since the battery contacts remain on the removed batteries, it is necessary to modify the case in order to return them. To do this, I cut 2 short tubes from a 20-gauge polypropylene pipe. Their length should correspond to the height of the battery pack removed. It is necessary for the segments to fit into the electric screwdriver battery case.

Most likely one of the edges of the tubes will have to be trimmed a bit, as it will rest against the protrusions on the cover.

Next, you need to remove the contact plates from the batteries and move them to the tubes. To make them fit tightly, each tube should be wrapped with electrical tape, thus increasing the seating diameter. After that, a cable of a convenient length is soldered to the contacts and they are finally attached to the tubes.

Now you need to connect the cable from the terminals of the electric screwdriver to the wire of the power supply. Here it is important to observe the polarity. The plus side of the block must be connected to the plus terminal and the minus side to the minus terminal. For reliability, it is better to solder the twist. It can be insulated with electrical tape or heat shrink.

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Next, the contacts with tubes are placed in the battery case. To do this, a side hole is made in it right at the junction with the cover to introduce the wire. To prevent the tubes with contacts from shifting and falling out, everything is fixed with hot melt glue. To ensure reliability, it can be applied to the joint between the housing and the cover, so that it does not open.

Now when you plug in the power supply the electric screwdriver can work from the mains as long as you want without recharging.

4V power supply with its own hands from Chinese devices

Cheap way to build the power supply for an electric screwdriver with voltage of 14V. remaking from Chinese PSU. Their input voltage is slightly higher: you should replace the resistors.

  • Desolder R10 resistor from the circuit diagram of Chinese PSU. Resistance of the constant resistor is 2320 Ohm.
  • Solder old PSU resistor into PCB.
  • Set the resistance at 2300 Ohm.

The current strength must not exceed 9A, or the PSU for your electric screwdriver will soon stop working.

make, volt, mains, powered, electric

Next, the resulting circuit is mounted in the housing of an electric screwdriver, pre-insulate the radio elements to prevent short circuits. In the case of an electric screwdriver power supply make ventilation holes. Next, the tool is connected to the mains 220 V and checked for proper operation.

In the same way you can make BPP from any resistor you buy. It is easiest to convert the circuit by soldering in additional diodes. The Chinese resistor is unsoldered and replaced with analog with the possibility of indirectly lowering the input voltage.

Independent power supply for the screwdriver

Work can also be done with a hand-held tool in a building where there is no electricity. In such cases, the device is connected to a car battery or any other power source appropriate for the operation of the screwdriver.

To connect the car battery you must take the wire with crocodile clips, stripe one end and solder directly to the contacts of the electric motor of the tool. The other end is clamped to the battery terminals, observing the polarity.

The connection principle of the portable battery is similar to that of a car battery. Only the ends of the wires are fitted with copper clamping terminals suitable for attachment.

An electric tool lasts much longer than a cordless tool. Therefore, you should not throw away the screwdriver if the batteries have expired. A handy man will be able to convert his power tool to mains power, thereby prolonging its life.

Work steps

The first step in converting a screwdriver for mains power is to solder the electrical wire to the charging terminals of the appliance. The connection can be tricky. the wire is largely made of copper, and the charger contains brass terminals, which makes them difficult to solder. Acid, which is excellent as a connecting element, will just help in this. To do this, you need to treat the brass charging terminals with it and solder the power cord to the contacts. Qualitatively performed soldering will ensure the smooth operation of the screwdriver for a long time.

Next you need to remake the faulty battery. To do it completely disassemble and remove all the insides, against the manufacturer’s recommendations. It is forbidden to throw the innards into the general trash garbage can. It is not necessary to throw out the housing. a weight for counterweight is placed inside it.

The next step is to solder the pins of the cord to the battery terminals, which are located inside the case. When working, it is important to observe the polarity, otherwise the screwdriver will screw in the opposite direction. This can be corrected with a normal switch.

After that the cord is led into the battery from the outside of the case, for which you must make a hole for the diameter of the wire. To reliably secure the wire in the case, it is recommended to wrap it with insulating tape inside and outside, making a special lock, which will reliably secure the resulting design.

The last step will be the direct installation of the finished battery case into the screwdriver from the mains and its subsequent operation.

The unit from the PC

If the power supply itself is broken, there are several options for replacing it to operate the device. The easiest and most convenient way is to use a useless power supply from a PC with at least 250W of power.

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On modern power supplies you usually need to short-circuit the wires, the color of which can be different. You can find out the correct sequence on the Internet or try to figure it out. The connector on the power supply for a screwdriver 12 V is located in the four-pin connector: minus for black, plus for yellow. Such models are equipped with a fan that should be installed outside of the device. To maintain the aesthetics and convenience when remaking a screwdriver from the computer power supply wires are hidden in the case.

The car battery

Another interesting and practical option. this is how to make a screwdriver from 220v with a car battery charger. The only disadvantage of this solution is the rapid discharge of the car power supply, so you can not work for a long time. This option is great for those who have failed the regular power supply of the device, which happens quite often. After spending a few hours, an experienced craftsman can remake the device for battery-powered operation, and the screwdriver will work even more effectively than the original battery.

Power Supply Options

Any electric screwdriver requires much less voltage than a regular outlet. That’s why you’ll need a special converter for the power supply, the output of which will produce the necessary voltage. All power supplies are divided into two big groups: pulsed and transformer. Let’s look at each of these points individually.

Pulsed

The principle of pulsed systems is that the voltage is first rectified and then converted to a special pulse signal. It’s important to have a stable voltage. A transformer coil or resistors might help.

Switch mode power supplies are quite efficient and can be used in many applications. And they have a high level of protection against short circuits and similar effects. But the switched mode systems clearly loses out to the transformer ones in terms of power. Besides such units are very picky about the input voltage. If it is lower than the set voltage, the element can simply not work.

Transformer

common power supplies that have proven reliable and efficient in many applications. This consists of a step-down transformer and a rectifier, through which a low voltage is passed. Rectifiers can be different, depending on the number of diodes used.

Such elements are simple to make, cheap and reliable. Therefore they are often preferred. They provide a stable voltage without interference with a high maximum output. But there are a few disadvantages. The main disadvantage is the cumbersomeness, with a much lower efficiency than a pulsed power supply. This fact requires to pick up a power supply for an electric screwdriver with a power greater than that needed by the tool. Since some of the power will go to side processes.

Powering an electric screwdriver from a 220V mains supply

I have finally embarked on the implementation of my longtime plan, namely, to provide power for an electric screwdriver from 220 volts. Surely some of you also have a screwdriver that has a worn out, unusable battery that no longer takes a charge. At my location I had two.

The first (black) has a working voltage of 18 volts. That’s what I originally wanted to plug in.к. It fits well in the hand and is quite powerful. But there is no button. Perhaps in the future I will cut the handle and make it like a drill. The second device is designed for 12 volts. Has been in service for quite a long time. Of course you can buy a new battery or you can replace the cans if needed. But still I want to have always a ready-made tool at hand, especially since it is not always convenient to use an electric drill.к. It’s heavy. We can do it with a power transformer.

I used a step-down transformer TS-250-36. “250”. is its rated power, and the number 36 means that the output voltage will be 36 V. It has an O-shaped magnetic core. Its windings are located so that half of the primary is wound on the left side and the other half on the right. The secondary winding is wound the same way and is located on top of the primary. The windings of a step-down transformer are easy to distinguish from each other, t.к. the secondary is made of a thicker wire, and the one that receives the line voltage is made of a thinner wire. That’s because it carries less current.

The windings are symmetrical and the two halves of 18 Volt are connected with a wire (you can see the connection place in the picture below). I will use one half.

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But before you rewind the transformer you have to measure. I urge you to be careful when working with current, do not touch live parts, and always check if the measurement limit is set correctly on the multimeter.

On the right you measure the voltage at half of the secondary. As you can see, the voltage is slightly above the nameplate values, i.e.к. There is no load connected.

So I separated one half and now let’s disassemble the transformer. Between the layers of paper there was a large amount of paraffin.

The secondary winding in my case is wound in two layers, separated by a layer of paper. To reduce the secondary voltage from 18 volts I had to remove almost half of the turns.

When you determine the required voltage you must take into account that after the transformer there will be a diode bridge, which will reduce the voltage by about a couple of volts. But adding a smoothing capacitor would cause a voltage increase of about 1.4 times. Т.е. in absence of load, rectified voltage on capacitor will be equal to amplitude value.

As you unwind the secondary, take measurements. Soon, I settled on 11.2 volts, i.e.к. was afraid of sagging when connecting the load.

When the transformer is prepared (although some can use a ready one with the right parameters), now it’s time to get acquainted with the circuit.

To the output of the transformer it is necessary to solder a diode bridge (VDS) to convert the AC current into a DC pulsating current. The diode bridge can be assembled from a separate diode or you can use a ready made diode. When sizing it, you need to consider how many amps your electric screwdriver consumes (choose a bridge with a reserve).

Wires from the secondary winding solder to the leads of the diode bridge, where the letters AC (alternating current).

Well, after the bridge it is necessary to solder a capacitor to smooth the ripple. Its voltage should be at least twice that of the electric screwdriver. And the capacity is from 470 uF to 2200 uF.

If you want you can add a switch and a fuse in the circuit before the transformer.

So, after connecting the circuit, I made measurements. The no-load voltage at the output of the power supply (when the load is not connected) is 15 volts. When you start the electric screwdriver, it sags to 11.5 volts, which is the norm, so it’s not a big deal. A fully charged new battery gave 13 volts.

This is what the tool looks like from the inside. Here you can find the limiting parameters of the button, and you can also notice that the motor is controlled by a powerful field effect transistor.

To have a comfortable connection to the power supply I took the battery apart. From it we need the contacts. This part needs to be tinned. I soldered with rosin, but in some cases you might need flux for aluminum soldering.

Of course when soldering the wires from the power supply do not forget about polarity, usually it is marked on the battery. The compartment became very light. The wire was sealed with hot melt glue.

The tests showed that the electric screwdriver performed well on the power supply.

This article has a video that shows in detail the process of building a power supply, transformer rewinding, connection and test.

List of radio elements

Designation Type Nominal Quantity NoteMy NotebookVD1-VD4

C1

C2

C3

C4

C5

F1

Tr1

Figure
Diode KD2998B 4 Store search Ottron In pad
Capacitor 1.0 μF 1 400 В Search Ottron Store Notepad
Capacitor 0.47 uF 1 160 В Search in Otron store In the notebook
Electrolytic capacitor 2200 uF 15 16 В Store locator Ottron In the notepad
Electrolytic capacitor 1000 μF 4 16 В Store search Ottron In the notebook
Capacitor 1.0 μF 1 160 В Search in the Otron store Notepad
Fuse 3.16 А 1 see. text Search for Otron products To Notebook
Transformer 220/8 В 1 see. text Search in Otron store In the notebook
Add All

r9o-11 Published: 04.12.2015 0 1

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