Do-it-yourself power supply for an 18v electric screwdriver

Electric screwdriver resuscitation methods

The main advantage of an electric screwdriver can be called mobility. The battery lasts for a long time and in addition, you can purchase another battery for this model if the amount of work is large and the deadlines are running out. Despite the fact that the battery is mainly used lithium-ion (a very high-quality type of battery), there is a possibility of failure of the power circuit, as well as the autonomous source itself.

The electric screwdriver is powered and recharged from a 220V network. A voltage of about 14V or 20V goes to the battery (it all depends on the specific model). The battery produces a supply voltage of volts, respectively.

power, supply, electric, screwdriver

If the product is often not used, then over time the battery comes into disrepair, although the lithium-ion battery is protected from reloading and fully discharge, it makes no sense to hope for this protection. The main solutions to the issue are:

  • Replace the battery with a working one (it will be quite difficult to do, although it is possible).
  • Buy a new electric screwdriver.
  • Redo electric screwdriver with network.

Very easy to redo the battery model in the network (electric screwdriver from 220 volts network). This option has advantages, for example:

  • Eliminates the need for constant battery recharging.
  • Work tool without overload due to constant torque.
  • You can make such a model that will be and recharge the battery of any type.
  • Build quality (high quality parts will be used for the power supply, because the user does this for his own purposes. It does not make sense to constantly be distracted by the repair of the electrical part. this is extra TIME, and for some. the loss of part of the income).

When converting an electric screwdriver to a network one with your own hands, its mobility will disappear. This can be corrected by converting the tool to any type of battery and to any power supply.

Rework Options

There are several options for converting an electric screwdriver, and only the user decides for himself which one to choose. Main ways:

  • Apply laptop charger (connect laptop adapter).
  • Use a computer switching power supply (hereinafter PSU) from a personal computer.
  • Use a car battery.
  • Improve PSU to power halogen lamps.
  • Build your own PSU.

Steps 1 to 4 require almost no special skill and will suit most people. Their essence lies in the use of ready-made devices, because almost all ready-made PSUs are protected from short circuits (short circuits), various kinds of overloads and interference, and a car battery is generally an ideal power source.

Laptop charger

A very simple way that requires a minimum of knowledge in the field of electronics. For the manufacture of a power supply for an electric screwdriver 12V with their own hands will suit any laptop charger. To remake, you need to find out the supply voltage of an electric screwdriver and select the appropriate charge. You need to do the following:

  • Disassemble the battery compartment and remove the defective battery.
  • On charging from a laptop, cut off the output connector (not network. incoming. It is very important).
  • strip wires.
  • Turn on the charging (the wires should not touch) and check the constant voltage with the device (any voltmeter with a measurement voltage of more than 50 V or an ordinary multimeter is suitable for this purpose).
  • After measuring the power supply parameters, it is necessary to solder the wires, observing the polarity.
  • Close the battery compartment by placing the charger in it and unplug the power cord.
  • Connect to the network and check the operation of the tool.

When buying a charger, you should pay attention to its dimensions, but it is better to take an electric screwdriver with you, after removing the battery and dismantling the battery compartment. During installation, you must follow the safety rules to avoid electric shock and prevent failure of the laptop charger.

Computer power supply

Another good option is to use a power supply from a personal computer and preferably an AT form factor. The main parameters of the PSU: power 300.350 W, voltage 12 V and current of at least 16 A. This option is not suitable for 18V electric screwdriver. The main advantages are the presence of a power button, protection against short circuits, overloads, as well as a cooling system, which is not in the factory model of an electric screwdriver. To implement this idea, you need to follow these steps:

  • Unwind the AT power supply.
  • The power-on protection is removed by shorting the green wire to any black one from this connector (when the PSU is turned on, it will not start unless the protection is bypassed).
  • On the white connectors that are inserted into the hard drive or other drive, leave the yellow and black wires, and all the rest must be cut and insulated.
  • Extend the yellow and black wires with a cable of the required length (preferably soldered, as twists can oxidize).
  • We solder the yellow and black wire, observing the polarity, to the contacts of the battery compartment and assemble it.
  • For PSU, you can use a longer wire (power cord). In addition, you need to make a casing for the computer power supply in order to comply with safety regulations when working with electrical appliances.

After all the steps taken, turn on the PSU in the network and run the tool. If everything is done correctly, then it should work. If rotation occurs in the opposite direction, it is necessary to disassemble the battery compartment and change the polarity. In the absence of power, make sure that the input and output voltages are present.

car battery

The optimal way to source electrical energy, protected from accidental short circuits, the voltage is stabilized and there are no various interferences. Significant disadvantages are its dimensions, weight and the need to charge. The usage example is very simple. You just need to power the electric screwdriver from the battery terminals, using the cable of the required length, and pre-solder the old battery.

To the car battery, you need to purchase a charger or make a homemade transformer charger. In addition, you need to protect the battery from rain and debris. To do this, a special case is made with leads for the charger and power for an electric screwdriver.

See also  Lithium Screwdriver Conversion Kit

Screwdriver conversion methods

By this time, the case should already be open, so you can start reworking the box, which previously housed the battery. The sequence of actions will be as follows:

  • Separate the cord with leads from the plug (you must use a soldering iron).
  • Place a naked power supply unit to the place of the former battery.
  • Lead the power cord to the PSU through a special hole in the case.
  • Solder the cord to the PSU.

The main task is to solder the wires from the contacts that are connected to the battery to the contacts of the new power supply. As a result, the current will go directly to them, allowing you to start the motor when you press the button.

The output of the block is connected by terminals with the obligatory observance of polarity. This whole structure should fit in the place of the former battery, which is no longer needed. If something does not converge in size, then it is better to build a new nest into the instrument handle.

A prerequisite is to connect the power supply in parallel with the supply terminals, and install a special diode in the wire break on the plus. If this is not done, then power during operation may go to the battery. The diode, in turn, is built into the circuit with a minus towards the tool motor.

Cordless electric screwdriver: we understand the design

Structurally, a cordless electric screwdriver consists of the following elements:

an electric screwdriver with a power supply will become an indispensable assistant for a homeowner. While the screwdriver unscrews one screw, the power tool will cope with ten

  • motor;
  • batteries;
  • start key;
  • regulator;
  • reducer;
  • a lever that changes the direction of movement of the device;
  • charging.

Why convert a wireless device to a wired one? Batteries inside the unit are a limited amount of time (about a year with permanent operation). Changing batteries is an expensive undertaking (one battery will cost at least a thousand and it’s not a fact that it will work for a long time).

After 3-4 months of use, the battery starts to “sit down” quickly. Then the device needs constant recharging, which, at the very least, annoys the owner.

I decided that I needed to make a mains power supply, and in the battery compartment, so as not to disturb the weight and geometric balance of the tool. I dismissed the 50 Hz transformer right away. Sh / PL of suitable power (according to my estimates 120-150VA) is problematic to place there, the torus is too bold. the cost can approach somewhere around half of the strability of the above electric screwdriver). So UPS! And then I again caught my eye “dead” energy saving. Power is clearly not enough. And what does the power of the UPS mainly depend on?? That’s right, from active elements and a “power” transformer.

Transistors change to 13007, although there are energy-saving and with such transistors. Will probably work 13005 but I haven’t tried. Let’s leave the 1N4007 bridge diodes. I think one-ampere ones in the mains supply are enough. We replace the D0 inductor with ATX. sky. we will not make noise in the power grid.

To do this, we drill an additional hole in the scarf.

We remove the L4 inductor. it is too low-power for our tasks. And instead of it we solder (of course with a mounting wire) ATX. sky “power” transformer.

Directly by “network” winding! ATH. sky trances do not burn! (almost according to Woland).

Charger for an electric screwdriver from a printer power supply

Consider, with a specific example, how to remake the IIP to fit your needs. In my opinion, manufacturing from scratch, for example, a switching power supply, is often time-consuming and economically unprofitable, in addition, the thought that you need to find a suitable case completely discourages needlework.

Another thing is the alteration of an unnecessary finished product for its purposes. The case is there, alterations and costs are minimal, the power section is made safe in the factory and has a bag of certificates.

Production of a power supply unit based on the battery compartment of an electric screwdriver

To do this, use a powerful soldering iron 100W. Plastic melting well. We remove the remains with round-nose pliers and refine the hole to the required shape with a mini-drill with the necessary nozzles.

Similarly, we make holes for the remaining two plugs.

Transformer mounting

Due to the fact that the available transformer did not enter the battery compartment a little (by 4 mm), it was decided to increase the latter by squeezing out the plastic when heated. ABS plastic noticeably softens after 100 degrees Celsius.

We fix the block together with the transformer with the help of three clamps and residues Chipboard. We gradually heat up the plastic with a building hair dryer and twist the handles of the clamps in parallel. We achieve the desired degree of extrusion and give plastic cool. After that, we remove the load.

As a result, we obtain an acceptable form of block.

Installation and testing of “electronic filling”

The connection diagram of the elements is quite simple.

Transformer. diode bridge. voltage regulator. capacitor.

A radiator was attached to the transistor to remove heat. Additionally connected fan to improve air circulation. Also subsequently made a dozen holes in the case to improve air circulation. The capacitor was placed in the vertical part of the block. The output voltage was exhibited 14.4V

Plugs and reverse polarity protection in screwdriver housings

A diode has been added to the wiring inside the screwdrivers to prevent reverse polarity.

Finishing photos


Supply voltage at the PSU output without load = 14.4V. At idle, when one electric screwdriver is connected, = 12.8V (current 1.3A) In operating mode, the current approaches 3A.

At idle when connecting two screwdrivers = 10.2V

To use the PSU, three power cables were soldered in length: 2.7 m, 4.9 m, 10.4 m. A drop in voltage when used, respectively: 0.2B. 0.3V. 0.9V (at idle, t.E. Current 1,3A)

The temperature regime during the operation of two screwdrivers in the XX mode for three minutes is satisfactory. The temperature rose to 55 degrees Celsius.

How to make a power supply for an 18v electric screwdriver with your own hands instructions and diagrams

Any household tool that can function autonomously has a significant drawback. Maintaining a battery in good condition is troublesome, during operation it requires regular charging, the shelf life is limited, and the cost of such a power source is such that purchasing a new one is quite “affordable”.

Yes, and it is not always possible to find it, especially if the electric screwdriver of the old modification. The conclusion is simple. to make a power supply for an 18-volt electric screwdriver with your own hands.

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The most rational solution is to pick up components or remake an existing power supply from any technical device. This can be done with your own hands, without outside help.

Electric screwdriver powered by 220V

Finally, I started to implement my old idea, namely to provide power for an electric screwdriver from a 220 volt network. Undoubtedly, some of you also have a screwdriver, with a worn, unsuccessful battery that no longer takes charging. There were two instances at my location.

At the first (black) operating voltage is 18 volts. It was him that I originally wanted to power from the network, t.To. fits comfortably in the hand and quite powerful. But the button is missing. Perhaps in the future I will cut off the handle and make it look like a drill. The second copy is rated for 12 volts. Served for quite a long time. Of course, you can buy a new battery or, in extreme cases, replace the banks. But still, I want to have a ready-made tool at hand, especially since it is not always convenient to use an electric drill.To. she is heavy. A power transformer will help us to realize this idea.

A step-down transformer TC-250-36 was used. “250”. this is its rated power, and the number 36 means that the output will be 36 V. It has an O-shaped magnetic pipeline. Its windings are arranged in such a way that half of the primary is wound on the left, the second half on the right side. The secondary winding, which is located on top of the primary, is wound in a similar way. It is not difficult to distinguish the windings from each other in a step-down transformer, because.To. The secondary is made of a thicker wire, and the one on which a network voltage is supplied from a thinner wire. This is due to the fact that there is a shorter current flows.

Winding have a symmetrical location and two halves of 18 volts are connected by a wire (the connection site is clearly visible in the lower photo). I will use one half.

But before rewinding the transformer, you need to measure. I urge to be neat when working with a current, do not touch the current parts, and also always check the correct measurement limit on the multimeter correctly.

On the right, the voltage is measured at half the secondary winding. As can be seen, the voltage is slightly exceeded by passports, t.To. No load is connected here.

So I separated one half and now proceed to disassembling the transformer. Between the paper layers was a large number 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, almost half of the turns had to be removed.

When determining the required voltage, it must be taken 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 will cause the voltage to rise by about 1.4 times. T.e. in the absence of load, the rectified voltage across the capacitor will be equal to the amplitude value.

As we unwind the secondary, we take measurements. Soon, I settled on a value of 11.2 Volts, t.To. I was afraid of drawdown when connecting the load.

Now that the transformer is ready (although some may use a ready-made one with the right parameters), now it’s time to get acquainted with the circuit.

A diode bridge (VDS) must be soldered to the output of the transformer in order to convert the alternating current into a pulsating direct current. The diode bridge can be assembled from separate diodes or use a ready-made. When choosing it, you should take into account how many amperes your electric screwdriver consumes (select a bridge with a margin).

We solder the wires from the secondary winding to the terminals of the diode bridge, where the letters are AC (alternating current).

Well, after the bridge you need to solder a capacitor for smoothing pulsations. Its voltage must exceed the supply voltage of an electric screwdriver at least twice. And capacity from 470 μF to 2200 μF.

Optionally, in the diagram, you can add a switch and a fuse in front of the transformer.

So, after connecting the scheme, I made measurements. The idle voltage at the output of the power supply (when the load is not connected) is 15 volts. When the electrical screwdriver is started, it seats up to 11.5 volts, which is the norm, so nothing terrible. Fully charged new battery issued 13 volts.

So 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.

In order to make it convenient to connect to the power supply, I disassembled the battery. We need contacts from him. This detail needs to be tinned. I have soldered with rosin, but in some cases it may be necessary to flux for soldering aluminum.

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

How to make a power supply for the electric screwdriver

Tests have shown that an electric screwdriver, when working from a power supply, coped with the tasks.

There is a video for this article that shows in detail the process of creating a power supply, rewinding a transformer, connecting and testing.

AC adapter for cordless screwdriver

A friend asked me to assemble an external power supply for a screwdriver. Together with a screwdriver (Fig.1) brought a power transformer from the old Soviet burner-engraver “Ornament-1” (Fig.2). see if it can be used?

First, of course, we dismantled the battery compartment, looked at the “cans” (Fig.3 and Fig.4). We checked each “can” with a charger for operability with several charge-discharge cycles. out of 10 pieces, only 1 is good and 3 are more or less normal, and the rest are completely “dead”. So, you definitely have to make an external power supply.

To assemble the power supply, you need to know how much current the screwdriver consumes during operation. By connecting it to the laboratory source, we learn that the engine begins to rotate at 3.5 V, and at 5-6 in a decent power on the shaft appears in. If you press the start button when 12 V is applied to it, the protection at the power supply is activated. which means that the current consumption exceeds 4 A (the protection is set to this value). If you start the screwdriver at low voltage, and then increase it to 12 V, it works fine, the current consumption is about 2 A, but at the moment when the screw being screwed in is halfway into the board, the protection of the power supply is activated again.

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To see the full picture of the consumed currents, the screwdriver was connected to a car battery by putting a 0.1 Ohm resistor in the positive wire gap (Fig.5). The drop voltage from it was served in a computer audio card with an open input, the Spectraplus program was used to view. The resulting graph is shown in Figure 6.

The first impulse on the left. start-up when turned on. It can be seen that the maximum value reaches 1.8 V and this indicates the current current 18 A (I = U / R). Then, as the engine is set, the current drops to 2 A. In the middle of the second second, the head screwdriver is clamped by hand until the “rattling” triggers. The current at that time increases to about 17 A, then drops to 10-11 A. At the end of the 3rd second, the launcher is released. It turns out that for the screwdriver to work, a power supply is required with the ability to deliver power of 200 W and current up to 20 A. But, given that the battery compartment says that it is 1.3 A / h (Fig.7), then, most likely, everything is not as bad as it seems at first glance.

We open the power supply of the burner, measure the output voltage. Maximum. about 8.2 V. Few, of course. Considering the voltage drop across the rectifier diodes, the output voltage across the filter capacitor will be about 10-11 V. But there is nowhere to go, we are trying to assemble the circuit according to Figure 8. Diodes used brand KD2998V (Imax=30 A, Umax=25 V). The fastening of the VD1-VD4 diodes is carried out by surface mounting on the petals of the contact sockets of the burner (Fig.9 and rice.10). Parallel connection of 19 pieces of smaller capacity was used as a large capacitor. The whole “battery” is wrapped with painting scotch and capacitors selected such sizes so that the entire bunch with a lightweight enters into the rehabative compartment of the screwdriver (rice.11 and rice.12).

The fuse block is very inconvenient in the burner, so it was removed, and the fuse was soldered “directly” between one of the 220 V wires and the output of the interference suppression capacitor C1 (Fig.thirteen). When the case is closed, the mains cable is tightly crimped with a rubber ring through, and this does not allow the wire to dangle inside when it is bent from the outside.

Checking the performance of the screwdriver showed that everything is working fine, the transformer after half an hour of drilling and tightening the screws heats up to about 50 degrees Celsius, the diodes heat up to the same temperature and do not need radiators. A screwdriver with such a power supply has less power compared to powering it from a car battery, but this is understandable. the voltage on the capacitors does not exceed 10.1 V, and when the load on the shaft increases, it further decreases. By the way, it is decently “lost” on a supply wire about 2 meters long, even using it with a cross section of 1.77 To check the drop on the wire, a circuit was assembled according to Figure 14, it controlled the voltage on the capacitors and the voltage drop on one conductor of the supply wire. The results in the form of graphs at different loads are shown in Figure 15. Here in the left channel. the voltage on the capacitors, in the right. the drop on the “negative” wire going from the rectifier bridge to the capacitors. It can be seen that during the shutter of the head screwdriver, the supply voltage is driving up to levels below 5 V. At the same time, the power cord falls about 2.5 V (2 times 1.25 V), the current is pulsed and is associated with the work of the rectifier bridge (rice.sixteen). Replacing the power cord to another, with a cross section of about 3 led to an increase in the heating of the diodes and the transformer, so the old wire was returned back.

We looked at the current in the circuit between the capacitors and the screwdriver itself, assembling the circuit according to Figure 17. The resulting graph is in Figure 18, “shaggy”. these are ripples of 100 Hz (the same as in the previous two figures). It can be seen that the starting impulse exceeds the value of 20 A. most likely, this is due to the lower internal resistance of the power supply due to the use of parallel connection of capacitors.

At the end of the measurements, we looked at the current through the diode bridge by connecting a 0.1 Ohm resistor between it and one of the terminals of the secondary winding. Graph in fig.19 shows that when the motor is decelerating, the current reaches 20A. On pic.20. time-stretched section with maximum currents.

As a result, while we decided to work with a screwdriver with the described power supply, if there is “not enough power”, then we will have to look for a more powerful transformer and put diodes on radiators or change to others.

And, of course, you should not take this text as a dogma. there are absolutely no obstacles to manufacturing a PSU according to any other scheme. For example, the transformer can be replaced with a TC-180, TCA-270, or you can try to power a screwdriver from a computer pulse power supply, but most likely, you will need to check the possibility of outputting a 12 V current 25-30 A circuit.

List of radio elements

Designation Type Denomination Quantity NoteShopMy notepadVD1-VD4








Diode KD2998V 4 Store search Otron To notepad
Capacitor one.0 uF one 400 V Store search Otron To notepad
Capacitor 0.47uF one 160 V Store search Otron To notepad
Electrolytic condenser 2200uF 15 16 V Search in Store Rock In notepad
electrolytic capacitor 1000 IF 4 16 V Search in Store Rock In notepad
Capacitor one.0 uF one 160 B Store search Otron To notepad
Fuse 3.16 A one cm. text Search in Store Rock In notepad
Transformer 220/8 B one cm. text Store search Otron To notepad
Add all

r9o-11 Posted: 04.12.2015 0 1