In the article we will talk about how to make a triac power controller with your own hands. What is a simistor? This is a device built on a semiconductor crystal. It has as many as 5 p-n junctions, the current can pass both in the forward and in the opposite direction. But these elements are not widely used in modern industrial equipment, as they are highly sensitive to electromagnetic interference.
Also, they cannot operate at high current frequencies, they generate a large amount of heat if they switch large loads. Therefore, IGBT transistors and thyristors are used in industrial equipment. But triacs should not be overlooked either - they are cheap, they have a small size, and most importantly, a high resource. Therefore, they can be used where the disadvantages listed above do not play a big role.
How does a triac work?
Meet the triac power controller todayit is possible in any household appliances - in grinders, screwdrivers, washing machines and vacuum cleaners. In other words, wherever there is a need for smooth adjustment of the engine speed.
The regulator works like an electronic key - it closes and opens at a certain frequency, which is set by the control circuit. When the device is unlocked, a half-wave of voltage passes through it. Therefore, a small fraction of the minimum power is delivered to the load.
Can I do it myself?
Many radio amateurs make their own triac power controllers for various purposes. With it, you can control the heating of the soldering tip. But, unfortunately, ready-made devices can be found on the market, but quite rarely.
They are low cost, but often the devices do not meet the requirements that consumers demand. That is why it is much easier, it turns out, not to buy a ready-made regulator, but to make it yourself. In this case, you will be able to take into account all the nuances of using the device.
Regulator circuit
Let's look at a simple triac power controller that can be used with any load. The control is phase-pulse, all components are traditional for such structures. You need to apply the following elements:
- Directly a triac, rated for 400 V and 10 A.
- Dinistor with opening threshold 32 V.
- To adjust the power is usedvariable resistor.
The current that flows through the variable resistor and resistance charges the capacitor with every half wave. As soon as the capacitor accumulates a charge and the voltage between its plates is 32 V, the dinistor will open. In this case, the capacitor is discharged through it and the resistance to the control input of the triac. The latter opens at the same time so that the current flows to the load.
To change the duration of the pulses, you need to select a variable resistor and the threshold voltage of the dinistor (but this is a constant value). Therefore, you have to "play" with the resistance of the variable resistor. In the load, the power is directly proportional to the resistance of the variable resistor. It is not necessary to use diodes and a fixed resistor, the circuit is designed to ensure accuracy and smoothness of power control.
How the device works
The current that flows through the dinistor is limited by a fixed resistor. It is with its help that the pulse length is adjusted. The fuse protects the circuit from short circuit. It should be noted that the dinistor in each half-wave opens to the same angle.
Therefore, there is no rectification of the flowing current, you can even connect an inductive load to the output. Therefore, a triac power regulator can also be used for a transformer. In order to select triacs, you need to take into account that for a load of 200 W, it is necessary that the current be equal to 1 A.
The following elements are used in the scheme:
- Dinistor type DB3.
- Triacs type BT136-600, TS106-10-4 and similar with current rating up to 12 A.
- Germanium semiconductor diodes – 1N4007.
- Electrolytic capacitor for voltage over 250V, capacitance 0.47uF.
- Variable resistor 100 kOhm, constant - from 270 Ohm to 1.6 kOhm (selected empirically).
Features of the regulator circuit
This scheme is the most common, but you can also find small variations of it. For example, sometimes a diode bridge is placed instead of a dinistor. In some circuits, a chain of capacitance and resistance is found to suppress interference. There are more modern designs that use a control scheme on microcontrollers. With such a circuit, you get fine current and voltage regulation in the load, but it is more difficult to implement.
Preparatory work
In order to assemble a triac power controller for an electric motor, you just need to follow this sequence:
- First you need to determine the characteristics of the device that will be connected to the regulator. Characteristics include: the number of phases (either 3 or 1), the need for fine adjustment of power, voltage and current.
- Now you need to select a specific type of device - digital or analog. After that, you can select the components according to the load power. Basically, forsimulation can use specially designed software.
- Calculate the heat dissipation. To do this, multiply two parameters - the rated current (in Amperes) and the voltage drop across the triac (in Volts). All this data can be found among the characteristics of the element. As a result, you will get the power dissipation, expressed in watts. Based on this value, you need to select a heatsink and a cooler (if necessary).
- Purchase all the necessary items or prepare them if you have them.
Now you can proceed directly to the assembly of the device.
Regulator assembly
Before you assemble a triac power regulator according to the scheme, you need to perform a series of actions:
- Rout the tracks on the board and prepare the sites on which you want to install the elements. Provide space for mounting the triac and radiator in advance.
- Install all the elements on the board and solder them. In the event that you do not have the opportunity to make a printed circuit board, surface mounting is allowed. The wires that connect all the elements should be as short as possible.
- Pay attention to whether the polarity is observed when connecting the triac and diodes. If there is no marking, ring the elements with a multimeter.
- Check the circuit using a multimeter in resistance mode.
- Fix the triac on the radiator, it is advisable to use thermal paste for better surface contact.
- The whole circuit can be installed in a plasticcase.
- Set the variable resistor knob to the leftmost position and turn on the device.
- Measure the voltage value at the output of the device. If you turn the resistor knob, the voltage should gradually increase.
As you can see, a DIY triac power controller is a useful design that can be used in everyday life with almost no restrictions. The repair of this device is cheap, as the cost is quite low.
