Wall Charger Screwdriver
Not a single repair is complete without a drill. This electrical appliance is powered by mains or battery. If a cordless drill is selected for work, you will also need a charger for it. It is sold complete with the device. However, such an element sooner or later fails. To avoid an unfortunate circumstance, you should study the design capabilities and a description of the charges. It is especially worth getting acquainted with the charger circuit of a drill / driver. This will help you learn how to properly repair it.
Types of Chargers
There are many varieties of devices for charging cordless drills. They differ in price, principle of operation and repair features. Each type of screwdriver should be considered in more detail.
Analog devices with integrated power supply
Such devices are quite popular due to their low cost. If the drill will not be used for professional purposes, do not focus on the duration of the work. The main condition that the simplest charger should meet is that it must provide sufficient current load to charge the battery of the screwdriver.
The operation of an analog device with a power supply is quite simple. Such a charger is operated as a stabilizer. For example, you need to consider the charger circuit for a battery from 9 to 11 V. It does not matter what type of battery is used. Cordless drill / drivers are quite common among home masters, so knowing the features of their repair will be useful to everyone.
Such a power supply, many home masters assemble with their own hands. Soldering the circuit can only be done on the universal board. To ensure heat dissipation, stabilizer microcircuits, it is necessary to find a radiator made of copper of 20 square meters. cm square.
Thanks to the output transformer, the alternating voltage decreases from 220 V to 20 V. It is possible to calculate what the transformer power will be according to the voltage current at the charging output. AC rectification is carried out by a diode bridge.
After rectification, the current is pulsating. However, this feature of the current negatively affects the functioning of the circuit. Ripples can be smoothed out with a filter capacitor (C1). As a stabilizer, the KR 142EN chip is used. Radio amateurs call her “roll”. To get a voltage of 12 V, you must have a chip with an index of 8B. Management is going to transistor VT2. In addition, tuning resistors are used. Automation on such devices is not installed. How long the battery will be charged depends on the user. To control the charge, a fairly simple circuit is assembled on the transistor VT1. In the circuit there is also a diode VD2. When the charge voltage is reached, the indicator goes out.
modern systems have a switch. Thanks to it, the voltage is turned off at the end of the charge. When buying a cheap screwdriver with it comes with a simple charger. This explains why such devices break down very often. When buying such a screwdriver, the consumer risks staying with a new, but inoperative device. However, the charger is easy to assemble with your own hands. The main thing is to have a circuit.
A homemade device can last much longer than purchased. To select the value of the battery of a drill / driver, you will need to experimentally configure the transformer and stabilizer.
Analog devices with external power supply
The charger circuit itself is quite simple. Included with such a device is a network power supply and charger. It does not make sense to inspect the power supply. Its scheme is standard. It includes a diode bridge, a transformer, a rectifier and a capacitor filter. Usually there is 18 V.
Video: Wall Charger Screwdriver
Management is carried out using a small board, which has the dimensions of a matchbox. Such assemblies do not have a heat sink system. For this reason, such devices quickly fail. Therefore, users are often interested in how to charge a cordless drill / driver without a charger.
This problem can be solved quite simply:
- One of the main conditions is the availability of a power source. With the proper operation of the "native" block, you can create a simple control scheme. If the entire kit is out of order, a laptop power supply can be used. The desired 18 V is obtained at the output. Such source may have the power that is enough for any battery.
- The second condition is the ability to collect electrical circuits. Parts are usually soldered from old household appliances. In addition, most of them are sold on the radio market.
The control unit must have a circuit, as in the photo:
A zener diode of 18 V is installed at the input. The circuit, which the charger will be controlled by, works on the KT817 transistor. To provide amplification, a KT818 transistor is installed. At the same time, it is equipped with a radiator to remove heat. Depending on what the charge current will be, up to 10 watts can be dissipated on it. It is necessary that the radiator has the required area. from 30 to 40 square meters. cm.
The unreliability of Chinese batteries is due to the economy of manufacturers “on matches”. To establish the exact charge current, you must have a trimmer 1 Com. A 4.7 ohm resistor is installed at the output. It should also provide sufficient heat dissipation. The power output does not exceed 5W.
The assembled circuit is quite simply placed in a standard charging case. The radiator is optional. The main thing is that there should be sufficient air circulation inside the case. The power supply from the laptop is still used according to its purpose.
Professional screwdrivers are designed for heavy use. Therefore, downtime during work is unacceptable. It is worth remembering that every serious device has a high price. Therefore, the price issue should be omitted. In addition, the kit usually has 2 batteries.
The switching power supply is complemented by a "smart" control circuit. Thanks to this, the battery is charged at 100% in just an hour. You can build the same analog type charger yourself. However, its dimensions will be equal to the size of the screwdriver itself.
Pulse devices are good because they are devoid of many shortcomings. They are quite compact, have high charge currents and are equipped with an elaborate protection system. There is only one problem. the circuit of such devices is rather complicated, which affects the cost of the device.
However, even such an apparatus can be built on its own. Savings come out about 2 times.
It is worth considering the option for nickel-cadmium batteries, which are equipped with a third signal contact. Going device diagram on the MAX713. This controller is quite popular. The output voltage will be 25 V. The current will be constant. To assemble such a power source is quite simple.
The charger is equipped with several features that make it intelligent. After the voltage level is checked, it is necessary to start the accelerated discharge mode. This will prevent the memory effect. The charge is carried out in an hour and a half. The main distinguishing feature of the circuit is the ability to select the type of battery and charge voltage.
When branded charging a professional device, you can save a lot on repairing a charger for a screwdriver. The circuit can be built independently.
Power supply for screwdriver
Quite often, owners of screwdrivers are faced with a situation where the device itself is working properly and the battery pack is out of order. There are many ways to solve this problem. However, not everyone will work with toxic parts.
To continue working with a screwdriver, you must connect an external power supply. If you have a standard Chinese device with 14.4 V batteries, you can use a car battery. However, there is another option. to find a transformer with an output voltage of 15-17 V in order to assemble a full-fledged power supply.
The necessary details are cheap. First of all, you need a thermostat and a diode bridge. Other structural elements perform service functions. to show the input and output voltage. The stabilizer does not need to be purchased. This is due to the undemanding screwdriver motor.
As you can see, the assembly of the charger for the cordless drill is quite simple. The main thing is not to decide to immediately throw away the appliance. With a complete failure of the batteries, the device can be converted to a network one. Such work also has many subtleties that you should get to know.
To build your own charging for a screwdriver, you will need to find out the circuit of such a device and the characteristics of the main parts. The build process itself is quite simple. The main thing is to be able to work with a soldering iron.
Even if the power supply unit of a professional screwdriver model fails, it can be made networked. If you decide to repair the device yourself, you do not have to worry about the price of parts. they cost a penny on the radio market. Knowing these features repair cordless screwdrivers will help you do the job yourself.