How to make a speed controller: do-it-yourself converter, how to choose the right 12V circuit

When using an electric motor in various devices and tools, it is invariably necessary to adjust the speed of rotation of the shaft.

It is not difficult to make an electric motor speed controller on your own. You just need to find a high-quality circuit, the device of which would fully fit the features and type of a particular electric motor.

Using frequency converters

Frequency converters can be used to adjust the speed of an electric motor operating from a network with a voltage of 220 and 380 volts. High-tech electronic devices allow, due to the change in the frequency and amplitude of the signal, to smoothly adjust the speed of the electric motor.

Such converters are based on powerful semiconductor transistors with wide-pulse modulators.

The converters with the help of the appropriate control unit on the microcontroller allow you to smoothly change the engine speed.

High-tech frequency converters are used in complex and loaded mechanisms. Modern frequency controllers have several degrees of protection at once., including the load, voltage current indicator and other characteristics. Some models are powered by a single-phase 220 volt power supply and can convert the voltage to three-phase 380 volts. The use of such converters allows the use of asynchronous electric motors at home without the use of complex connection schemes.

Application of electronic regulators

The use of powerful asynchronous motors is impossible without the use of appropriate speed controllers. Such converters are used for the following purposes:

• The step-by-step acceleration and the ability to lower the engine speed when the load is reduced allows to reduce energy consumption. The use of frequency converters with powerful induction motors can cut energy costs in half.
• Protection of electronic mechanisms. Frequency converters allow you to monitor pressure, temperature and a number of other parameters. When using the motor as a pump drive in a container into which liquid or air is pumped, a pressure sensor can be installed, which is responsible for controlling the mechanism and preventing it from leaving building.
• Ensuring a smooth start. When starting the electric motor, when the motor immediately starts to run at maximum speed, the drive has an increased load. The use of a speed controller ensures smooth start-up, which guarantees the maximum possible durability of the drive and the absence of its serious breakdowns.
• Costs for maintenance of pumps and the power units themselves are reduced. The presence of speed controllers reduces the risk of damage to individual mechanisms and the entire drive.

The operating scheme used by frequency converters is similar to that of most household appliances. Similar devices are also used in welding machines, UPS, power supply for PCs and laptops, voltage stabilizers, lamp ignition units, as well as in monitors and LCD TVs.

Despite the seeming complexity of the circuit, it will be quite simple to make a 220 V electric motor speed controller.

How the device works

The principle of operation and the design of the engine speed controller is simple, therefore, having studied the technical points, it is quite possible to perform them yourself. Structurally, there are several the main components that make up the speed controllers:

• Electrical engine.
• Converter block and microcontroller control circuit.
• Mechanisms and drives.

The difference between induction motors and standard drives is the rotation of the rotor with maximum power indicators when voltage is applied to the transformer winding. At the initial stage, the indicators of the consumed current and the power of the motor increase to a maximum, which leads to a significant load on the drive and its rapid failure.

When the engine is started at maximum speed, a large amount of heat is generated, which leads to overheating of the drive, winding and other drive elements. Thanks to the use of a frequency converter, it is possible to smoothly accelerate the motor, which prevents overheating and other problems with the unit. The electric motor can, when using a frequency converter, start at a speed of 1000 V minute, and subsequently smooth acceleration is ensured, when 100-200 rpm is added every 10 seconds engine.

Making homemade relays

Making a homemade 12 V motor speed controller will not be difficult. For such work, you will need the following:

• Wirewound resistors.
• Multi-position switch.
• Control unit and relay.

The use of wire-wound resistors allows the supply voltage to be varied, respectively, and the engine speed. Such a regulator provides stepped acceleration of the engine, has a simple design and can be performed even by novice radio amateurs. Such simple home-made step regulators can be used with asynchronous and contact motors.

The principle of operation of a homemade converter:

1. Mains power is directed to the capacitor.
2. The capacitor used is fully charged.
3. The load is transferred to the resistor and bottom cable.
4. The thyristor electrode, connected to the positive terminal on the capacitor, receives the load.
5. A voltage charge is transmitted.
6. The second semiconductor is discovered.
7. The thyristor passes the load received from the capacitor.
8. The capacitor is completely discharged, after which the half-cycle is repeated.

In the past, the most popular were mechanical governors based on a variator or gear drive. However, they did not have the required reliability and often failed.

Homemade electronic regulators have proven to be the best. They use the principle of changing a step or smooth voltage, are distinguished by their durability, reliability, have compact dimensions and provide the ability to fine-tune the operation of the drive.

Additional use in circuits of electronic regulators of triacs and similar devices allows you to ensure smooth change in voltage power, respectively, the electric motor will gain speed correctly, gradually reaching its maximum power.

To ensure high-quality control, variable resistors are included in the circuit, which change the amplitude of the input signal, providing a smooth or step change in the number of revolutions.

PWM transistor circuit

It is possible to regulate the speed of rotation of the shaft in low-power electric motors using a bus-transistor and a series connection of resistors in the power supply. This option is simple to implement, however, it has low efficiency and does not allow smoothly changing the engine speed. It will not be particularly difficult to make a 220 V collector motor speed controller with your own hands using a PWM transistor.

The principle of operation of the regulator on a transistor:

• The bus transistors in use today have a sawtooth voltage generator with a frequency of 150 Hertz.
• Operational amplifiers are used as a comparator.
• The change in rotation speed is carried out due to the presence of a variable resistor that controls the pulse duration.

The transistors have a constant constant amplitude of pulses, identical to the amplitude of the supply voltage. This allows you to adjust the speed of the 220 V engine and maintain the operation of the unit even when the minimum voltage is applied to the transformer winding.

Due to the possibility of connecting the microcontroller to a PWM transistor, it is possible to automatically configure and adjust the operation of the electric drive. Such converter designs may have additional components that expand the functionality of the drive, ensuring fully automatic operation.

Implementation of automatic control systems

The presence of microcontroller control in regulators and frequency converters allows to improve the parameters of the drive, and the motor itself can work in fully automatic mode when the used controller smoothly or stepwise changes the speed indicators unit. Today, processors are used as microcontroller control, which have a different number of outputs and inputs. To such a microcontroller, you can connect various electronic keys, buttons, all kinds of signal loss sensors, and so on.

On sale you can find different types of microcontrollers, which are distinguished by their ease of use, guarantee high-quality adjustment of the operation of the converter and regulator, and the presence of additional inputs and outputs allows you to connect to processor, various additional sensors, on the signal of which the device will decrease or increase the number of revolutions or completely stop supplying voltage to the windings electric motor.

Various converters and motor controllers are on sale today. However, if you have even minimal skills in working with radio components and the ability to read diagrams, you can make such a simple device that will smoothly or stepwise change the engine speed. Additionally, you can include a control triac rheostat and a resistor in the circuit, which will allow you to smoothly change turns, and the presence of microcontroller control fully automates the use of electrical engines.