Power regulator on the triac BTA16-600

Power regulator for various loads, such as incandescent lamps, heating elements, etc. It is possible to regulate the speed of the electric motor, but is the power lost?

The thyristor is designed for a current of up to 16 Amperes, it is without a snubber and therefore in the diagram R3-C2 perform the function of a snubber

 

Longwave radio transmitter on one transistor 2SK30A

Long wave radio transmitter at a frequency of approximately 170 kHz with a range of no more than 10 meters with a ferrite antenna. Transistor 2SK30A. Winding L1 contains 60 turns and winding L2 contains 20 turns, wire with a diameter of 0.14 mm. Ferrite core with a diameter of 8-10 mm and a length of 8 centimeters, but these data on ferrite can be changed, this will only change the frequency.

When you turn it on for the first time, the transmitter should start working immediately, otherwise swap the terminals of the L2 coil or wind and unwind the turns of the wire.

 

How to assemble and configure SSB power amplifier 3.5-30 MHz

Today you can buy on the Internet a rather popular kit for assembling a homemade power amplifier for a radio station or a homemade radio transmitter, which operates at frequencies from 3.5 to 30 MHz (SSB + CW, with amplitude modulation I have not tested) and has a maximum output power of 70 W, but such power will not be in the entire frequency range. With this amplifier I conducted radio communication at a distance of 3100 kilometers at a frequency of 7 MHz. I will show you how to assemble and configure this amplifier.

This kit does not have a radiator to remove heat from the transistors, you need to find it yourself. Also required is a power source up to 14 volts and a current of 6-8 amperes. Transistors used IRF530N two pieces. First, you need to wind two high-frequency transformers: input and output.

You need to break off four plates from the board. The input transformer is wound on a ferrite core, similar to a pair of binoculars. Insert two metal tubes into the ferrite and solder the plates to their ends. These two tubes are just the secondary winding with a tap from the middle. Wind two turns of insulated wire through these tubes - this will be the primary winding of the transformer. Solder the finished transformer to the board.

The output transformer is assembled from two ferrite tubes, into which two metal tubes are inserted, to the ends of which two plates are soldered. Everything is exactly the same as in the input transformer. Three turns of insulated wire must be inserted and wound into these tubes.

You can wind the wire after you solder the transformers to the board

Next, we solder the electronic components onto the board; the relay contacts need to be bent

The power choke contains two turns of wire in varnished insulation. Since such a wire is inconvenient to wind, I wound two turns of wire in insulation that I found on my own.Jumpers JP1 and PTT should be plugged. If you have an output filter, then jumper JP1 should not be plugged. You can connect the filter to the LPF in-out contacts.

Here is the aluminum radiator I found. I drilled holes for the transistor flanges. The transistors need to be isolated from the radiator, for this purpose the kit includes thermal pads and plastic bushings into which you need to insert screws and secure the transistors. These plastic bushings are very important and you need to be careful and check whether the transistor drains are isolated from the radiator.

Here is the amplifier assembled

I soldered two pieces of coaxial cable with a wave resistance of 50 Ohm to the input and output of the amplifier. I have not soldered special SMA connectors yet.

Now we set up the amplifier. We supply 13 volts. Just in case, connect a load to the amplifier output - a 50 Ohm resistor. No signal is supplied to the amplifier input. The trimmer resistor must be set and adjusted to a voltage of 3.5 volts on the gate-source of two transistors, the current consumption will be about 70 mA. When switching on for the first time, it is advisable to set the rotor of the trimmer resistor to a position in which the lowest voltage will be supplied to the transistor gates.

This is my 50 ohm resistor rated for 40 watts. It consists of 20 1k ohm resistors in parallel, each dissipating 2 watts. This resistor has the lowest inductance, wirewound resistors are not suitable.

After the voltage on the transistor gates has been set, you can now check the operation of the amplifier. I have a homemade radio transmitter with a power of 200 mW at a frequency of 27 MHz. I connected the output of this radio transmitter to the input of the amplifier, and connected a device measuring power to the output of the amplifier. As you can see, the output of the amplifier will be 7000 mW or 7 W of output power with an input of 200 mW.

Next, I connected the transceiver output to the amplifier input. I received my La-La-La signal at a distance of 3100 kilometers in the city of Oslo, Norway.

Field effect transistor 2n7002.60V 120mA (smd 702)

2n7002 (SMD702) is an n-ch field effect transistor  that can be found on old computer motherboards

drain-source voltage - 60V

drain current-120mA (pulsed 800mA)

gate-source voltage-20V

 power dissipation 200mW (25C)

gate threshold voltage 1-2.5V

Rds 1.2-7.5 Ohm (10v 500mA)

 

DIY Interturn short circuit tester for anchor or stator of electric motors

With this simple tester, you can find an interturn short circuit in the anchor or stator of an electric motor, even if one turn in the windings is shorted.

A transmitter is assembled on the VT1 transistor, a receiver on VT2, a detector on the diode, and a signaling device on VT3-5. Coils L1-L2 are in the same plane at a distance of 3 cm from each other and are well fixed. If you bring the anchor with a closed turn to these coils from the side, the LEDs will switch and show in which groove the coil with a closed turn is wound.

Coils L1-L2 are wound on ferrite dumbbells 10 mm long with an unknown ferrite. You can wind the coils on the dumbbells that you have, the magnetic permeability of the ferrite can be different. I took ready-made chokes. Choke L1 with an inductance of about 990 μH, L2 - 9.8 mH, a difference of ten times. This inductance can be different, there is no clear data on these coils here. The transmitter coil must emit a signal of sufficient strength, and the receiver coil must also receive it with sufficient strength. A diode of the 1n4148 type can be used, etc., but the voltage drop on silicon will be greater. It is advisable to use transistors VT2 and VT3 with a high gain.The device can be tested, adjusted and configured in a cascade by surface mounting. First, you need to assemble a signaling device on transistors VT3-5 and a diode. The anode of the diode is not connected anywhere. When power is supplied, the LED on the right according to the diagram lights up. Touch the anode of the diode and the power plus with your finger, the LEDs will switch, the transistor VT5 will be open by the closed transistor VT4.

The transmitter on VT1 can be checked with a long-wave radio receiver; by bringing the receiver to the L1 coil, the hissing will be quieter. This is a generator of a sinusoidal signal with a frequency of approximately 30-35 kHz and a peak-to-peak amplitude of about 8 volts.

The device is adjusted by the trimmer resistor R4. The operating mode can be set in different ways. If you check closed turns without a core, then you need to make sure that the LED on the right side of the diagram initially lights up. Bring one closed turn to the coils L1-L2, the device will respond by switching the LEDs. If you check closed turns with a magnetic circuit, that is, an anchor or stator, you need to set the LED glow on the left side of the diagram with a resistor, and the LED on the right side should not light up

Now, slowly rotating the anchor near the coils, you can find the short circuit of the turns in the anchor. When the turn is closed, the LED on the right will go out, and the left one will light up. In this case, you can determine in which slot the winding with the closed turn passes. Since the winding passes through two slots, the LED on the left will light up twice.

Simple direct conversion receiver with dual diode mixer BAT85

I present a simple direct conversion radio receiver, with which you can receive radio stations with amplitude modulation, one sideband and telegraph. It works on short waves at the frequency to which you will have the input filter and generator tuned, I made it for the 80 meter range. You will need to connect a tunable generator to the receiver, this can be done on one transistor or connect a ready-made generator like I did. How does such a receiver work? The signal from the antenna goes to the filter L1 C2, which is tuned to a frequency range of approximately 3400-3700 kHz, this filter will suppress all other frequencies. The mixer is assembled on two Schottky diodes BAT85. The signal from the filter L1-C2 and the signal from the generator go to the mixer, and the frequency of the generator should be two times less than the received signal, since the mixer "multiplies" the frequency of the generator by two, I will describe its operation below. If one of the frequencies differs from the other by, say, 1000 Hz, you will hear these 1000 Hz in the speaker and this is called beating. There will be different signals at the mixer output, and 1000 Hz must be passed through the speaker and everything else must be filtered out. This is done by a two-link low-pass filter on two coils L2-L3 and three capacitors. It filters the high-frequency signals and passes the desired low-frequency signal. The sound signal is amplified by a preamplifier on a transistor. 2sc3198 and then goes to the low frequency amplifier.

The L1 coil is wound on a 6mm diameter frame with a ferrite core. It contains 46 turns of 0.12mm diameter wire with a tap from the 6th turn. I will tell you how to make a low-pass filter on L2-L3 in another article, but you can also make a single-link filter or another filter altogether from the circuits of other similar receivers. In the evening, with a 5-meter antenna, I received AM broadcasting stations and an SSB signal from amateurs. You can also receive AM signals at 2900 kHz; to do this, you need to adjust the ferrite in the coil and change the capacitance C2

Here's how the mixer works on these two diodes: when the generator voltage passes through zero, two diodes are closed. At the peaks of the negative or positive half-waves, one of the diodes opens and the L1-C2 filter is connected to the low-pass filter. The mixer closes and opens with a double generator frequency. At the generator frequency of one million Hertz, two diodes switch two million times. This is how the generator frequency is "multiplied". The diodes operate from the generator signal and its amplitude should be at least 1 Volt, I checked this in practice. But you can find the optimal generator voltage yourself, it also depends on the antenna. For good reception, turn off all sources of interference near the antenna and receiver. The signal from the generator must be shielded. I did not select the diodes. It can also work with a rectangular signal

DIY GSM power amplifier on RF3140 chip from cell phone

There are chips in cell phones that amplify a weak high-frequency signal by power, and one of these chips is RF3140. This chip was used in old cell phones, today it is no longer in production, but you can still buy it

Based on this microcircuit, you can assemble a microwave power amplifier for the frequency ranges: 824-849 MHz (GSM850), 880-915 MHz (EGSM900), 1710-1785 MHz (DCS 1800), 1850-1910 MHz (PCS1900). Power supply from 3 to 5.5 V. The output power with a power supply of 3.7 V at a frequency of 1785 MHz is 2.2 W with a current consumption of 1.1 A. The output power can be adjusted.

A weak DCS / PCS signal is supplied to pin 1, from pin 11 this amplified signal goes to the antenna. A weak GSM/EGSM signal is fed to pin 7 and from pin 9 to the antenna. Pin 2 is used to switch ranges. At a high level, DCS/PCS will be connected, at a low level, GSM/EGSM. According to the diagram, the DCS/PCS range is connected. Pin 3 is connected to the plus through a resistor, pin 4 is the plus of the power supply. Pin 5 is used to adjust the transmitter output power. A signal from the DAC is fed to pin 6, but it is not used in the diagram.

The photo shows the pinout. All the pins that are not indicated are the negative pin, including the large rectangle, to which I connected the negative power supply.

Since I do not have a weak signal source for these frequencies, I connected a 4 cm long wire to pin 1 to generate a signal and test the microcircuit. At frequencies in the 1710-1910 range, the microcircuit will begin to generate a signal that can be taken from pin 11. I connected a 3.5 cm antenna to this pin through a 2.5 V*150 mA incandescent lamp. The microcircuit will heat up with such a non-standard connection, part of the power does not go to the antenna but dissipates as heat. The microcircuit must be installed on a radiator through heat-conducting paste.

I adjusted the power to the minimum with a trimmer resistor...

... and to the maximum. With proper connection of this microcircuit, and this is the installation of capacitors on the power supply, input-output matching, you can assemble a microwave power amplifier for various applications.

Why do they put a diode in parallel with the relay coil. What is it for?

In the diagrams, in which the relay coil is installed in the load on the collector or drain of the transistor, you can see that a diode is installed parallel to the coil relay, with the cathode to the positive power supply. With this connection of the diode, the current through it will not go to the transistor. Then what is it for?

This diode is necessary to bypass the relay when the power is turned off, when the transistor opens. When the power is turned off, an EMF pulse (electromotive force of self-induction of the coil) is formed at the coil terminals, the voltage of which can reach tens of volts, which can lead to failure of the transistor, which is not designed for such voltage. These pulses can simply disrupt the operation of the device. The diode, closing, bypasses the relay, since at the moment of the EMF pulse, the polarity changes at the coil terminals and the diode closes, that is, minus EMF appears on the cathode, and plus on the anode.

These self-induction pulses can be seen on an oscilloscope. I assembled a simple circuit consisting of a 3.7V power supply, a button, and a relay coil with a diode. I connected the oscilloscope probe to the coil terminals.

First check without diode, if there is no diode installed in parallel with the relay coil. You will see that individual pulses can reach 82 volts.

Now I connected the diode and the pulses disappeared. This means that the diode works in this circuit, the main thing is that the diode is designed for such voltage.If the transistor can withstand high voltage, then the diode probably doesn't need to be installed.

The computer mouse wheel has become poorly working. How to fix this

The computer mouse, namely the scroll wheel, started to "glitch". If you

scroll the wheel down, the cursor on the monitor screen will jump up and down, this also applies to scrolling the wheel up. At first I thought that the problem was in the

radio channel, because the mouse has a Bluetooth system. I brought the mouse closer to the receiver and

the same thing, I also checked the 1.5V battery. As a result, having disassembled the mouse, it became

clear that the problem was in the wheel itself. It is a contact with the

slider, which can become dirty or oxidized over time, or

the contact can loosen. I solved the problem simply, I took and replaced the encoder

with another one from another mouse

How to recognize an original or counterfeit MOSFET transistor

Recently I bought two IRF3205 MOSFET transistors in one store. I also bought the same IRF3205 transistor in another store, but cheaper. And I had suspicions about the cheap transistor. Is it really a fake? But how can I tell if there is a good inscription on the case and it is impossible to determine a bad transistor by its appearance.

You can distinguish an original MOSFET from a fake by measuring its input capacitance. The IRF3205 datasheet indicates its input capacitance of 3700 pF on average. I touch the gate-source of the transistor with measuring tweezers and the capacitance is about 4300 pF. This is normal.

Now I measure the input capacitance of a fake transistor, which was cheaper. It is 1570 pF. About two and a half times less than the capacitance. What does this mean? And this means that the crystal area of ​​such a transistor will be less than the crystal of the original transistor. Such original transistors are formed using HEXFET technology, this is when thousands of field-effect transistors are connected in parallel in one transistor and therefore such a transistor has a large current and open channel resistance. The capacitance of the transistors will be as indicated in the datasheet. The counterfeit has a smaller capacitance, which means the crystal will be smaller, and this means that the transistor can withstand less current than the original. Put the counterfeit in the equipment and after a short period of works, replace the counterfeit transistor again, it will fail.

Broke the original and the fake transistors to see the crystal and measure it. The original has a semiconductor crystal area of ​​about 4.5 mm * 4 mm

You can see the fake crystal in the photo. Its dimensions are approximately 2 mm. Although this is also a MOSFET, it is clearly not for 110 Amperes but much smaller.

Conclusion. Cheap transistors can be fake and you need to check the input capacity, so we will know that the crystal area is normal or less. But there is another nuance, this concerns the purchase of high-voltage field-effect transistors. The crystal of the original and the fake can be approximately the same size and normal capacity, but the fake cannot withstand high voltage