# How Many Amperes Does A 12 Volt Screwdriver Consume

Power supply instead of a battery for a screwdriver Power supply instead of a battery for a screwdriver I want to replace the batteries in a small electric screwdriver with a power supply. Trance plus vip straightener. Battery voltage 3.6 V. Battery.

## Power supply instead of battery for screwdriver

I would like to replace the batteries in a small electric screwdriver with a power supply. Trance plus vip straightener. Battery voltage 3.6 V. Battery. These are three series-connected Ni-Cd AA type batteries, 1.2 V each with a capacity of 600 mAh. I took a medium-sized transformer, wound two dozen turns of wire with a diameter of 0.5 over all the windings. I connected a diode rectifier with a capacitor. The output received 4 volts DC. I connected it instead of the battery. The screwdriver hums and barely turns. Measured the resistance of the engine. 4 Ohm. The voltage at the motor terminals dropped to 0.5 V.
Question: how to replace the battery with a 220 V power supply? I suspect a powerful trance is needed. Over there, a welding machine is used to light the car instead of the battery. Or maybe use a thicker wire to wind the required winding?

Vicselc: medium sized transformer
Not informative.
Try rewinding with at least 1mm wire.
Ideally, first connect to a laboratory power supply unit with an ammeter and see the consumption under maximum load (up to stopping by hand).
And select the rectifier based on the max. Current.

Wind a dozen more turns

Such screwdrivers can consume up to 5 Amperes under a maximum load.
Based on this, the power supply must be calculated. The tension, for complete happiness, can be slightly raised.

Agn: maximum load up to 5 Amperes
Those. Wires 0.5. 1.0 will obviously be small.

Vicselc: Battery voltage 3.6 V. Battery. These are three series-connected Ni-Cd AA type batteries, 1.2 V each with a capacity of 600 mAh.

Not certainly in that way.
You have on a fully charged battery 31.34 or even 31.4 = 4.2V
otherwise, you will greatly limit yourself in torque.

The resistance of a motor designed for 4V and having 4 ohms is hard to believe.
Is this not a child’s toy for an hour?

Somewhere here I was creating a theme using my screwdriver.
With a battery voltage of 12V, the current consumption is greater than 10A.
What should it be at 3.6V.

True, I have AA batteries, but still, a lot.

Graciano: Those. Wires 0.5. 1.0 will obviously be small.
I experimented with a screwdriver that says FULL TECH HOBBY, Model FT-2145, NiCd, 4.8 V, 1.4“, 150 rpm. Made, like in Germany. Generally cheap. Presumably, there are 4 batteries of 1.2 V. The capacity did not even look. Enough for a very short time.
So, when powered from an external source, if you stop it completely, which happens all the time, then at 5 Volts of power, the current is about 5 Amperes. If there are 3 batteries in a screwdriver, with a comparable power it should eat even more. If its power is less, then you can expect about the same consumption. The batteries in them are used mercilessly, as a result, when it is needed, they are always discharged. Even if not used, they are dead after a week. I have it.
For myself, I found a way out. I use an external stabilized power supply unit. Collected it on VIPer100a. According to the typical scheme. I just had these mikruhi in stock. Others and less powerful ones can be used. My size is about the size of a pack of cigarettes. There are no problems, it works comfortably.
My opinion is that without stabilization, at such a low voltage (3.6. 4.8 Volts) with such fluctuations in current consumption, one cannot do without stabilizing the output voltage. Maybe not right. Thicker wire, stronger diodes, do not regret it on iron, maybe there will be no problems. With the inevitable increase in idle voltage, as a result of the speed, the engine will probably cope.
Yes, if my memory serves me, the screwdriver consumes more than 1 Ampere at idle.

Vicselc: I measured the resistance of the engine. 4 Ohm
vicselc: Battery voltage 3.6 V

3.6 / 4 = 0.9A. And It is in locked rotor mode.
Or The owner of the topic made a mistake with the measurements or is it really a toy.

Agn: then at 5 Volts of supply, the current is about 5 Amperes.
I believe.

DWD: Somewhere here I was creating a theme using my screwdriver.
Similarly. I have an old DeWalt. So here he Knocks out 15A protection on the power supply
when trying to turn something like a 5150 screw practically
swirled into an oak board.

(I specifically set up the protection, otherwise this monster BP would give all 20A,
at 13.2V. But this was not necessary at all. )

Gentlemen, you should not compare an electric screwdriver and a screwdriver, these are devices that are completely different in power.

Agn: Collected it on VIPer100a. According to the typical scheme

Also spoiled. The impulse power supply is asked for here, small size and weight, because of the repeated short-term operation, you can do without radiators.

The smallest and deadliest 12v Makita on XX, in principle, somehow turns the blocks on viper22 But ess-but does not start normally from it, it is also impossible to work. Protection is triggered when the engine starts abruptly, even with a block on torus227 (13v / 12a). But if you raise the current limit more than 20A, then you can work normally.

Forum about radio site dedicated to the discussion of electronics, computers and related topics.

## Power supply of the screwdriver from the 220V network

Finally, I started to implement my old idea, namely to provide power for the screwdriver from a 220 volt network. Undoubtedly, some of you also have a screwdriver, with a worn out, unusable battery that no longer takes charge. I had two copies at my disposal.

The first (black) has an operating voltage of 18 volts. It was him that I originally wanted to power from the network, tk. Fits comfortably in the hand and is quite powerful. But the button is missing. Perhaps in the future I will cut off the handle and make something like a drill out of it. The second copy is designed for 12 volts. Served for quite a long time. The battery can of course be purchased with a new one or, in extreme cases, replaced by banks. But all the same, I want to have a ready-made tool at hand, especially since an electric drill is not always convenient to use. It is heavy. A power transformer will help us implement this idea.

A step-down transformer TS-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 circuit. His 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 is wound in a similar way, which is located on top of the primary.
It is not difficult to distinguish the windings from each other in a step-down transformer, because the secondary is made of a thicker wire, and the one to which the mains voltage is supplied from a thinner wire. This is due to the fact that a smaller current flows through it.

The windings have a symmetrical arrangement and the two halves of 18 volts are connected with a wire (the connection point is clearly visible in the bottom photo). I will use one half.

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

On the right, the voltage is measured across half of the secondary winding. As you can see, the voltage is slightly higher than the rated values, because no load is connected here.

So I separated one half and now we proceed to disassemble the transformer. There was a large amount of paraffin between the layers of paper.

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 borne in mind 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. Those. In the absence of load, the rectified voltage across the capacitor will be equal to the peak value.

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

With the transformer ready (although some may use the ready-made one with the desired parameters), now it’s time to get familiar with the circuit.

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

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

Well, after the bridge, you need to solder a capacitor to smooth out the ripple. Its voltage must exceed the supply voltage of the screwdriver at least twice. And the capacitance is from 470 μF to 2200 μF.

If desired, a switch and a fuse can be added in the circuit in front of the transformer.

So, after connecting the circuit, I made measurements. The idle voltage at the output of the power supply (when no load is connected) is 15 volts. When you start the screwdriver, it sags to 11.5 volts, which is normal, so it’s okay. A fully charged new battery produced 13 volts.

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

In order to conveniently connect to the power supply, I disassembled the battery. We need contacts from him.
This detail needs to be tinned. I have brazed about Bosch using rosin, but in some cases I may need flux for aluminum brazing.

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 melt glue.

Tests have shown that the screwdriver coped with the tasks when working from the power supply.

## Power supply of the screwdriver from the 220V network

Finally, I started to implement my old idea, namely to provide power for the screwdriver from a 220 volt network. Undoubtedly, some of you also have a screwdriver, with a worn out, unusable battery that no longer takes charge. I had two copies at my disposal.

The first (black) has an operating voltage of 18 volts. It was him that I originally wanted to power from the network, tk. Fits comfortably in the hand and is quite powerful. But the button is missing. Perhaps in the future I will cut off the handle and make something like a drill out of it. The second copy is designed for 12 volts. Served for quite a long time. The battery can of course be purchased with a new one or, in extreme cases, replaced by banks. But all the same, I want to have a ready-made tool at hand, especially since an electric drill is not always convenient to use. It is heavy. A power transformer will help us implement this idea.

A step-down transformer TS-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 circuit. His 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 is wound in a similar way, which is located on top of the primary.
It is not difficult to distinguish the windings from each other in a step-down transformer, because the secondary is made of a thicker wire, and the one to which the mains voltage is supplied from a thinner wire. This is due to the fact that a smaller current flows through it.

The windings have a symmetrical arrangement and the two halves of 18 volts are connected with a wire (the connection point is clearly visible in the bottom photo). I will use one half.

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

On the right, the voltage is measured across half of the secondary winding. As you can see, the voltage is slightly higher than the rated values, because no load is connected here.

So I separated one half and now we proceed to disassemble the transformer. There was a large amount of paraffin between the layers of paper.

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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 borne in mind 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. Those. In the absence of load, the rectified voltage across the capacitor will be equal to the peak value.

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

With the transformer ready (although some may use the ready-made one with the desired parameters), now it’s time to get familiar with the circuit.

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

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

Well, after the bridge, you need to solder a capacitor to smooth out the ripple. Its voltage must exceed the supply voltage of the screwdriver at least twice. And the capacitance is from 470 μF to 2200 μF.

If desired, a switch and a fuse can be added in the circuit in front of the transformer.

So, after connecting the circuit, I made measurements. The idle voltage at the output of the power supply (when no load is connected) is 15 volts. When you start the screwdriver, it sags to 11.5 volts, which is normal, so it’s okay. A fully charged new battery produced 13 volts.

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

In order to conveniently connect to the power supply, I disassembled the battery. We need contacts from him.
This detail needs to be tinned. I have brazed about Bosch using rosin, but in some cases I may need flux for aluminum brazing.

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 melt glue.

Tests have shown that the screwdriver coped with the tasks when working from the power supply.

## Power Supply

We will not consider buying any blocks or transformers, if we do buy a new battery! We will consider using what is at hand. I’ll tell you right away. The charger from the same screwdriver is only suitable for drilling ripe bananas, its power is too low.

Ideally, a step-down, powerful 12 V transformer is suitable, for example, from a computer UPS. The power of such a transformer is usually 350-500 watts. But I didn’t have such a transformer available, but I had a lot of computer power supplies. I am sure that if someone has various electronic junk, computer ATX is sure to be lying around in it.

A computer ATX unit is quite suitable for a screwdriver, the load capacity on the 12 volt bus allows you to remove currents of 10-20 amperes. I would like to dispel a little myth. It will not work to cram the unit into the battery case of the screwdriver, the ATX board is too big. We’ll have to make the unit a separate case or leave it in its native metal case. Lack of native corpus. Sensitivity to dust, and even the smallest repairs. It’s a lot of dust.

## Connecting a 12 volt screwdriver to the ATX power supply

Cordless screwdrivers are very convenient to use and are widely used by both professionals and DIYers. The battery is usually the first to fail. At the moment, all manufacturers of power tools have switched to lithium batteries and it is becoming more and more problematic to purchase a new nickel-cadmium battery for an old screwdriver, and the prices for these batteries are much higher than for lithium batteries.

## What current does the screwdriver consume?

Before choosing a suitable power supply, you need to understand what current consumption you need to count on. Unfortunately, manufacturers of cordless screwdrivers do not indicate the current drawn by the motor. The capacity of the battery itself in ampere-hours, which is necessarily indicated on the battery, does not make it possible to understand what is the current consumed by the screwdriver in operating mode. The maximum that the manufacturer can indicate is the power in watts, but this is very rare, usually the power is indicated directly in the torque force.

If the power in watts is still indicated, we can have an idea of ​​the current consumption and select the appropriate power supply with a small current / power margin. To calculate the current strength, it is enough to divide the power in watts by the operating voltage of the screwdriver, in this case it is 12 volts. So, if the manufacturer indicated a power for example 200 watts. 200: 12 = 16.6 A. This current is consumed by the screwdriver in operating mode.

However, the indicated power is very rare and there is no universal figure that characterizes all 12-volt screwdrivers. It should be understood that with full braking of the motor shaft, the currents can significantly exceed the rated ones and it is very difficult to calculate this value. At the same time, analysis of various forums and their own experience showed. For a screwdriver to work, a current of 10 A is often enough, this is enough to perform many screwing and drilling functions. At the same time, it is known that current surges with full shaft braking can exceed 30 A.

So what conclusion can be drawn from all this? For a screwdriver, a 12 V power supply giving 10 A of current is suitable, if it is possible to use a 20-30 A unit, this is even better. These are average figures that apply to most screwdrivers.

29 Oct 2013 | Section: Radio for home

Hello dear readers of the sesaga.Ru website. Every radio amateur, in his home laboratory, must have adjustable power supply, allowing to issue a constant voltage from 0 to 14 volts at a load current of up to 500mA. over, such a power supply must provide short circuit protection at the exit, so as not to burn the checked or repaired structure, and not to fail yourself.

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I bring to your attention the scheme simple regulated power supply, which was assembled by me back in the 80s (at that time, I was in the 8th grade), and the diagram was taken from the supplement to the magazine Young Technician №10 for 1985. The circuit is slightly different from the original by changing some germanium parts to silicon ones.

As you can see, the diagram is simple and does not contain expensive details. Consider her work.

## 1. Schematic diagram of the power supply.

The power supply is connected to the socket using a two-pole plug XP1. When the switch is turned on SA1 voltage 220V is applied to the primary winding (I) step-down transformer T1.

Transformer T1 reduces the mains voltage to fourteen17 Volt. This is the voltage taken from the secondary winding (II) transformer, rectified by diodes VD1 VD4, connected in a bridge circuit, and smoothed by a filter capacitor C1. If there is no capacitor, AC hum will be heard in the speakers when powering the receiver or amplifier.

Diodes VD1 VD4 and capacitor C1 form rectifier, from the output of which constant voltage is supplied to the input voltage regulator, consisting of several chains:

1. R1, VD5, VT1;
2. R2, VD6, R3;
3. VT2, VT3, R4.

Resistor R2 and zener diode VD6 form parametric stabilizer and stabilize the voltage across the variable resistor R3, which is connected in parallel with the zener diode. With this resistor, the voltage at the output of the power supply is set.

Variable resistor R3 maintained constant voltage equal to stabilization voltage Ust this zener diode.

When the variable resistor engine is in the lowest (according to the circuit) position, the transistor VT2 closed, since the voltage at its base (relative to the emitter) is zero, respectively, and powerful transistor VT3 also closed.

With the closed transistor VT3 resistance to its transition collector-emitter reaches several tens of megohms, and almost all rectifier voltage falls at this crossing. Therefore, at the output of the power supply (clamps HT1 and XT2) there will be no voltage.

When is the transistor VT3 open, and transition resistance collector-emitter is only a few ohms, then almost all the rectifier voltage goes to the output of the power supply.

So that’s it. As you move the variable resistor slider up to the base of the transistor VT2 will come unlocking negative voltage, and current will flow in its emitter circuit (EB). Simultaneously, the voltage from its load resistor R4 fed directly to the base of a powerful transistor VT3, and a voltage will appear at the output of the power supply.

Than more negative turn-on voltage at the base of the transistor VT2, themes more both transistors open, so more voltage at the output of the power supply.

The highest voltage at the output of the power supply will be almost equal to the stabilization voltage Ust zener diode VD6.

Resistor R5 simulates power supply loading when applied to terminals HT1 and XT2 nothing is connected. To control the output voltage, a voltmeter is provided, composed of milliammeter and an additional resistor R6.

On the transistor VT1, diode VD5 and resistor R1 assembly of protection against short circuit between the sockets HT1 and XT2. Resistor R1 and forward resistance of the diode VD5 form a voltage divider to which the transistor is connected by its base VT1. Operational transistor VT1 closed with a positive (relative to the emitter) bias voltage at its base.

In case of a short circuit at the output of the power supply emitter transistor VT1 will be connected to the anode of the diode VD5, and a negative bias voltage will appear at its base (relative to the emitter) (voltage drop across the diode VD5). Transistor VT1 will open and the site collector-emitter shunts the zener diode VD6. As a result, the transistors VT2 and VT3 will be closed. Plot resistance collector-emitter regulating transistor VT3 sharp will increase, voltage at the output of the power supply will fall almost zero, and so little current will flow through the short-circuit circuit that it will not harm the parts of the unit. Once the short circuit is removed, the transistor VT1 will close and the voltage at the output of the unit will be restored.

## 2. Details.

The most common parts are used in the power supply. A step-down transformer T1 Anyone can be used that provides an alternating voltage of 14-18 Volts on the secondary winding at a load current of 0.4 0.6 Amperes.

The original article uses a ready-made transformer from the frame scan of Soviet televisions of the type TVK-110LM.

Diodes VD1 VD4 may be from a series 1N4001 1N4007. Diodes designed for a reverse voltage of at least 50 volts with a load current of at least 0.6 amperes are also suitable.
Diode VD5 preferably germanium from the series D226, D 7 with any letter index.

Electrolytic capacitor of any type, for a voltage of at least 25 volts. If there is no one with a capacity of 2200 microfarads, then it can be made up of two 1000 microfarads, or four 500 microfarads.

Fixed resistors are used domestically MLT-0.5, or imported with a capacity of 0.5 watts. Variable resistor 5-10 kOhm.

Transistors VT1 and VT2 germanium any of the series MP39 MP42 with any letter index.

Transistor VT3 from the series KT814, KT816 with any letter index. This powerful transistor must be installed on the radiator.

The radiator can be used homemade, made of aluminum plate with a thickness of 3 5 cm and a size of about 60x60mm.

Zener diode VD6 we will select, since they have a large spread in stabilization voltage Ust. You may even have to make up two. But this is already during adjustment.

Here are the main parameters of the D814 A-D series zener diodes:

Use the milliammeter what you have. You can use indicators from old receivers and tape recorders. In one word, put what you have. And you can even do without the device altogether.

This is where I want to end. And you, if you are interested in the scheme, select the details.
In the next part, we will start drawing and making a printed circuit board from scratch, perhaps we will solder parts on it.
Good luck!