I want to share a circuit that is very useful for every radio amateur, found on the Internet and successfully repeated. This is really a very necessary device that has many functions and is assembled on the basis of an inexpensive ATmega8 microcontroller. There are a minimum of details, therefore, if there is a ready-made programmer, it is assembled in the evening.
This tester determines the numbers and types of outputs of a transistor, thyristor, diode, etc. with high accuracy. It will be very useful for both beginner radio amateurs and professionals.
It is especially indispensable in cases where there are stocks of transistors with half-erased markings, or if you can’t find a datasheet for some rare Chinese transistor. Scheme in the figure, click to enlarge or download the archive:
Types of tested radioelements
Element name - Display indication:
NPN transistors - display "NPN"
- PNP transistors - on the display "PNP"
- N-channel-enriched MOSFETs - on the display "N-E-MOS"
- P-channel-enriched MOSFETs - on the display "P-E-MOS"
- N-channel-depleted MOSFETs - on the display "N-D-MOS"
- P-channel-depleted MOSFETs - on the display "P-D-MOS"
- N-channel JFET - on the display "N-JFET"
- P-channel JFET - on the display "P-JFET"
- Thyristors - on the display "Tyrystor"
- Triacs - on the display "Triak"
- Diodes - on the display "Diode"
- Dual cathode diode assemblies - on the display "Double diode CK"
- Dual-anode diode assemblies - on the display "Double diode CA"
- Two series-connected diodes - on the display "2 diode series"
- Diodes symmetrical - on the display "Diode symmetric"
- Resistors - range from 0.5K to 500K [K]
- Capacitors - range from 0.2nF to 1000uF
Description of additional measurement parameters:
H21e (current gain) - range up to 10000
- (1-2-3) - the order of the connected pins of the element
- Presence of protection elements - diode - "Diode symbol"
- Forward voltage - Uf
- Opening voltage (for MOSFET) - Vt
- Gate capacitance (for MOSFET) - C=
The list provides an option to display information for the English firmware. At the time of this writing, Russian firmware appeared, with which everything became much clearer. to program the ATmega8 controller, click here.
The design itself is quite compact - about the size of a pack of cigarettes. Powered by a 9V "crown" battery. Current consumption 10-20mA.
For the convenience of connecting the tested parts, it is necessary to choose a suitable universal connector. A few are better various types radio components.
By the way, many radio amateurs often have problems checking field-effect transistors, including those with an insulated gate. Having this device, you can find out in a couple of seconds both its pinout, and performance, and the capacity of the transition, and even the presence of a built-in protective diode.
Planar smd transistors are also difficult to decipher. And many radio components for surface mounting sometimes fail even to roughly define - either it's a diode, or something else ...
As for conventional resistors, here the superiority of our tester over conventional ohmmeters, which are part of DT digital multimeters, is evident. Implemented here automatic switching required measuring range.
This also applies to testing capacitors - picofarads, nanofarads, microfarads. Simply connect the radio component to the device sockets and press the TEST button - all the basic information about the element will immediately be displayed on the screen.
The finished tester can be placed in any small plastic case. The device has been assembled and successfully tested.
Discuss the article TESTER OF SEMICONDUCTOR RADIO ELEMENTS ON THE MICROCONTROLLER
This is another article dedicated to a beginner radio amateur. Checking the performance of transistors is perhaps the most important thing, since it is a non-working transistor that is the cause of the failure of the entire circuit. Most often, novice electronics enthusiasts have problems checking field-effect transistors, and if you don’t even have a multimeter at hand, then it’s very difficult to check the transistor for performance. The proposed device allows you to check any transistor in a few seconds, regardless of type and conductivity.
The device is very simple and consists of three components. The main part is a transformer. As a basis, you can take any small-sized transformer from switching power supplies. The transformer consists of two windings. The primary winding consists of 24 turns with a tap from the middle, wire from 0.2 to 0.8 mm.
The secondary winding consists of 15 turns of wire of the same diameter as the primary. Both windings are wound in the same direction.
The LED is connected to the secondary winding through a 100 ohm limiting resistor, the power of the resistor is not important, the polarity of the LED is also, since an alternating voltage is formed at the output of the transformer.
There is also a special nozzle into which the transistor is inserted in compliance with the pinout. For direct conduction bipolar transistors (type KT 818, KT 814, KT 816, KT 3107, etc.), the base goes through a 100 ohm base resistor to one of the terminals (left or right terminal) of the transformer, the middle point of the transformer (tap) is connected to the plus of the supply, the emitter of the transistor is connected to the minus of the supply, and the collector to the free terminal of the primary winding of the transformer.
For reverse conduction bipolar transistors, you just need to reverse the power supply polarity. The same is with field-effect transistors, it is only important not to confuse the pinout of the transistor. If, after power is supplied, the LED starts to glow, then the transistor is working, if not, then throw it in the trash, since the device provides 100% accuracy of checking the transistor. These connections need to be made only once, during the assembly of the device, the nozzle can significantly reduce the time for checking the transistor, you just need to insert the transistor into it and apply power.
The device, in theory, is the simplest blocking generator. Power supply 3.7 - 6 volts, just one lithium is perfect - ion battery from mobile phone, but you need to unsolder the board from the battery in advance, since this board turns off the power, the current consumption exceeds 800 mA, and our circuit can consume such current in peaks.
The finished device turns out to be quite compact, you can put it in a compact plastic case, for example, from tick-tocks, and you will have a pocket device for testing transistors for all occasions.
Probably there is no radio amateur who would not profess the cult of radio engineering laboratory equipment. First of all, these are attachments to them and probes, which are mostly self-made. And since measuring instruments there is never too much, and this is an axiom, somehow I assembled a tester of transistors and diodes, small in size and with a very simple circuit. For a long time already there is not a bad multimeter, but a home-made tester, in many cases, I continue to use as before.
Device diagram
The probe constructor consists of only 7 electronic components + printed circuit board. It assembles quickly and starts working absolutely without any configuration.
The circuit is assembled on a microcircuit K155LN1 containing six inverters. When the outputs of a working transistor are correctly connected to it, one of the LEDs lights up (HL1 when N-P-N structure and HL2 for P-N-P). If faulty:
- broken, both LEDs flash
- has an internal break, both do not ignite
The tested diodes are connected to the terminals "K" and "E". Depending on the polarity of the connection, HL1 or HL2 will light up.
There are not many circuit components at all, but it is better to make printed circuit board, troublesome to solder the wires to the legs of the microcircuit directly.
And try not to forget to put a socket under the chip.
You can use the probe without installing it in the case, but if you spend a little more time on its manufacture, you will have a full-fledged, mobile probe that you can already take with you (for example, to the radio market). The case in the photo is made of a plastic case of a square battery, which has already worked out its own. All it took was to remove the previous contents and saw off the excess, drill holes for the LEDs and glue a bar with connectors for connecting the tested transistors. It will not be superfluous to “dress” the identification colors on the connectors. The power button is required. The power supply is a AAA battery compartment screwed to the case with several screws.
Mounting screws, small in size, are conveniently passed through the positive contacts and screwed with the obligatory use of nuts.
The tester is fully prepared. The best would be to use AAA batteries, four pieces of 1.2 volts will give the best option for a supplied voltage of 4.8 volts.
Using the device described here, it is possible to measure the reverse current of the collector junction IKB0 and the static current transfer coefficient h2)9 of low-power transistors of the p-p-p and p-p-p structures.
Structurally, the transistor tester is made in the form of an attachment to the av-meter, as well as transistor voltmeters for direct and alternating currents. For connection with the microammeter of the avometer, the attachment is equipped with a plug, which, during measurements, is inserted into the “100 μA” sockets on the front panel of the avometer. In this case, the switch for the type of measurements of the avometer must be in the “V” position.
The device is powered by a stabilized voltage of 9 V from an unregulated power supply source.
Before proceeding to the description circuit diagram tester, a few words about the principle underlying it. The vast majority of simple transistor testers described in amateur radio literature are designed to measure the static current transfer coefficient hjis at a fixed base current (usually -100 μA). This facilitates measurements [the scale of the device in the collector circuit of the transistor under test can be calibrated directly in the values hi20 = lHRB/UcB, where Ugb is the battery voltage (see Fig. 20.6)], however, such testers have a significant drawback. The fact is that the current transfer coefficient h2is largely depends on the operating mode of the transistor and, first of all, on the emitter current 1e. That is why reference books always give not only the values of the current transfer coefficient h2iв, but also the conditions in which it is measured (current Iв and voltage between the collector and emitter Ukb).
The static current transfer coefficient h2is of low-power transistors is usually measured at a current b = 0.5 mA (low-frequency low-power transistors), 1 mA (other low-frequency ones) or 10 mA (transistors designed to operate in a pulsed mode). The voltage 1Lke when measuring this parameter is usually close to 5 V. Since the coefficient h2ia depends little on Uks, for low-power transistors (except for high-frequency ones) it can be measured at the same value of Uks.
In testers measuring the static current transfer coefficient at a fixed base current, the collector (and, consequently, emitter) currents of the tested transistors, even of the same type, are almost always different. And this means that it is simply impossible to compare the measurement results with reference data (at a certain emitter current).
Devices in which it is possible to set any given collector (or emitter) current make it possible to obtain comparable values of the parameter h2iв, however, such testers are inconvenient to use, since they require the collector current to be set again for each measurement.
These shortcomings are not present in the tester of transistors included in the laboratory. It is designed to measure the static current transfer coefficient h2is at several fixed values of the stabilized emitter current. This makes it possible to evaluate the amplifying properties of the transistor in a mode close to the operating one, i.e., with a current flowing through the transistor in the device for which it is intended.
A simplified diagram of the meter of the static current transfer coefficient h2)g at a stabilized (fixed) emitter current is shown in fig. 44. The tested transistor VT, together with the elements of the tester, forms a current stabilizer. The voltage at the base of the transistor is stabilized by the zener diode VD, so a current flows in its emitter (collector) circuit, which is practically independent of the change in the voltage of the power supply GB. This current can be calculated using the formula 1b=(\Jvd-Use)/R2, where 1e is the emitter current (in amps), Uvd is the voltage across the zener diode (in volts), Use is the voltage drop across the emitter junction of the transistor (also in volts) , R2 - resistance (in ohms) of the resistor in the emitter circuit of the transistor. To obtain different currents through the transistor, it is enough to introduce a switch with a set of fixed resistors into its emitter circuit, the resistances of which are calculated according to the above formula. Since, at a fixed value of the emitter current, the base current is inversely proportional to the static current transfer coefficient h2is (the larger it is, the lower the base current, and vice versa), the scale of the RA device in the base circuit of the transistor under test can be calibrated in h2i8 values.
The radio amateur has to deal with both germanium and silicon transistors. For the first ones, the voltage Uaii = 0.2 ... 0.3 V, for the second, Shb \u003d 0.6 ... 0.7 V. In order not to complicate the device, when calculating the resistances of the resistors that set the emitter currents, you can take the average value of the drop voltage at the emitter junction, equal to 0.4 V. In this case, the deviation of the emitter current when testing any low-power transistors (and the selected voltage at the zener diode Uvd = 4.7 V) does not exceed ± 10% of the nominal, which is quite acceptable.
The circuit diagram of the transistor tester is shown in fig. 45. It is designed to measure reverse collector current Iki;o up to 100 μA and static current transfer coefficient h2ia from 10 to 100 at emitter current la = 1 mA and from 20 to 200 at emitter currents equal to 2; 5 and 10 mA. Tentatively, it is also possible to measure large values of the parameter h2i. If, for example, we consider the minimum measurable base current equal to 2 μA, which corresponds to one division of the M24 microammeter scale, then at an emitter current of 1 mA, values of the h2is coefficient up to 500 can be recorded, and at currents of 2, 5 and 10 mA - up to 1000. It should be taken into account that that the measurement error of such h2ia values can reach tens of percent.
The tested transistor VT is connected to the sockets of the XS1 socket. The emitter current at which it is necessary to measure the coefficient h2is is selected by the switch SA3, which includes (section SA3.2) in the emitter circuit of the transistor
one of the resistors R5 - R8. To obtain the indicated measurement limits for the coefficient h2ia (20 ... 200) at emitter currents equal to b and 10 mA, in the third and fourth positions of the SA3 switch, resistors R3 and R2 are connected in parallel with the microammeter PA1 of the autometer, respectively, as a result of which the current of the total deflection of its needle increases in the first case to 250, and in the second - to 500 μA.
From the mode of measuring the coefficient bce to the mode of monitoring the reverse current of the collector 1kbo, the tester is transferred by switch SA2. The first of these parameters is measured at a collector voltage (relative to the emitter) of about 4.7 V, the second - at the same voltage taken from the VD1 zener diode.
The SA1 switch changes the polarity of the power supply, the RA1 microammeter and the VD1 zener diode when testing transistors of different structures (p-n-p or p-p-p). Resistor R4, introduced into the collector junction circuit when measuring 1kV, limits the current through the microammeter in case the junction is broken. The current 1quo and the coefficient h2is are measured with the SB1 button pressed.
Construction and details. Appearance transistor tester together with an av-meter is shown in fig. 46, the layout of its front panel is in fig. 47, the layout of the circuit board and the connection diagram of the parts of the attachment - in fig. 48.
As in transistor voltmeters, the supporting element of the design is the body of the attachment, made of sheet aluminum alloy AMts-P 1 mm thick. On the front panel (top wall) there is an SB1 button, a board with clamps for connecting the transistor outputs and four brass racks with a diameter of 4 and a length of 19 mm with M2 threaded holes (6 mm deep) for mounting screws of the circuit board, on the side wall there is a plug block for connection of the attachment with the microammeter of the avometer.
A U-shaped cover (the material is the same as the body) with a plastic plate 3 ... 4 mm thick is attached to the body with M2x8 screws with countersunk heads. The screws are screwed into the M2 nuts glued to the housing shelves from the inside.
Switches SA1 - SA3 - sliding from the Sokol transistor radio. Two of them (SA1 and SA2) were used without alteration, the third (SA3) was converted into a two-pole four-position. To do this, the extreme fixed contacts were removed (one in each row), and the movable contacts were rearranged in such a way that the switching circuit shown in Fig. 49.
The conclusions of the switch contacts are inserted into the holes 0 2.6 mm of the board on the reverse side (according to Fig. 48, a) and are held on it by connecting wires soldered to them (MGShV with a cross section of 0.14 mm2) and the leads of the resistors R1-R8 (MJIT) and zener diode VD1. Resistors R5 - R8 are shown conventionally behind the circuit board, in fact they are located between the terminals of the switches SA3 and SA2.
The design of the socket block XS1 for connecting the outputs of transistors to the tester is shown in fig. 50. Its body consists of parts 1 and 3, made of sheet organic glass and glued with dichloroethane. Contacts 2 are made of sheet bronze (hard brass can be used) 0.3 mm thick. In order to be able to connect transistors of various designs and with different pin arrangements to the tester, the number of contacts was chosen to be five, and the distance between them was 2.5 mm. The block is attached to the body of the console with two M2Xb screws with countersunk heads. With the same screws on the side wall of the case, a plug block is fixed, which serves to connect the attachment to the microammeter of the avometer.
The device of the self-made button SB1 is shown in fig. 51. Its body consists of parts 2 and 5, sawn from organic glass and glued with dichloroethane. Contacts 1 and 3 are fixed to the part 2 with rivets 6. The button 4 itself is connected to the movable contact 3 with the MZX5 screw. To fasten the button to the body of the set-top box, the ends of parts 2 and 5 have threaded holes for M2 screws. Contacts 1 and 3 are made of the same material as the springy contacts of the socket block for connecting transistors, button 4 is made of polystyrene (organic glass, textolite, etc. can be used).
As in the previously described attachment devices, a two-wire cord was used to connect to the laboratory power supply, ending in plugs with a diameter of 3 mm.
All inscriptions are made on a sheet of thick paper and are protected from damage by a transparent overlay made of organic glass 2 mm thick. For fastening to the case, one of the screws for fastening the block for connecting transistors and three M2x5 screws screwed into the threaded holes of the lining were used.
Establishing a properly mounted transistor tester comes down mainly to the selection of resistors R3 and R2. The first one is selected in such a way that when it is connected to the microammeter of the avometer, the upper measurement limit rises to 250 μA, and the second - in such a way that it increases to 500 μA. In practice, it is convenient to do this by assembling an electrical circuit (Fig. 52) from an RA1 avometer microammeter, a RA2 exemplary microammeter with a measurement limit of 300 ... 500 μA, a GB battery with a voltage of 4.5 V (3336L or any three galvanic cells connected in series), shunt resistor R1, current-limiting resistor R2 and switch SA. By setting the engines of the resistors R1 and R2 to the extreme left (according to the diagram) position (i.e., to the position corresponding to their maximum resistance), they close the electrical circuit with the SA switch. Then, alternately reducing the resistance of both resistors, they ensure that at a current of 250 μA, counted on a PA2 exemplary microammeter, the pointer of the microammeter of the PAl avometer is set exactly to the last mark of the scale. After that, the circuit is broken and the prefix is \u200b\u200bdisconnected from the avometer. Switching the latter to ohmmeter mode, measure the resistance of the introduced part of the variable resistor R1 and select a constant resistor (R3) of exactly the same resistance (if necessary, it can be made up of two resistors connected in parallel or in series).
Similarly, but according to the current in the measuring circuit, equal to 500 μA, resistor R2 is selected. The selected resistors R3 and R2 are installed on the board.
The scale for measuring the static current transfer coefficient h2i9 (or a table, if there is no desire or opportunity to disassemble the microammeter of the autometer) is calculated by the formula h2ia \u003d Ie / 1b (here 1e is the emitter current corresponding to the selected measurement mode; 1b - expressed in the same units base current read on the scale of a microammeter, both currents in milli- or microamps). The values of the coefficient h2i3, corresponding to different currents of the base and emitter, are given in Table. one.
Checking the transistor begins with measuring the current of the collector junction 1yabo. To do this, switch SA1 is set to the position corresponding to the structure of the transistor under test, SA2 is set to the "1quo" position and the SB1 button is pressed ("Change"). After making sure that the transition is working properly (for germanium low-power transistors, the current of 1kbo can reach several microamperes, for silicon it is negligible), the switch SA2 is switched to the “h2is” position, the emitter current is set with the switch SA3, at which it is necessary to determine the coefficient h21e, and by pressing the button SB1, count the value of h2is on the scale of the microammeter (or convert the measured base current into a coefficient value using the table).
If a microammeter is used in the avometer with parameters that differ from those given in the description of the avometer, the resistance of resistors R2 and R3 will have to be calculated and selected in relation to the existing device.
It is desirable to have a medium and high power transistor tester in a radio amateur's measuring laboratory. It is especially necessary when selecting pairs of transistors for terminal push-pull cascades of audio frequency amplifiers with a power of more than 0.25 W.
The proposed device can be tested for breakdown of the collector junction of the transistor, measure the static current transfer coefficient h21e, check the stability of the transistor. Tests are carried out when the transistor is turned on according to the circuit with a common emitter. The indicator is a milliammeter for a current of 1 mA. The power source is a rectifier that provides a constant voltage of 12 V at a current of up to 300 mA. The reverse current of the Irbo collector junction is not measured, since for different transistors it can be from several microamperes to 12 ... 15 mA and this parameter has practically no effect on the selection of pairs of transistors for operation in a power amplifier.
The schematic diagram of the device is shown in fig. 1. The tested transistor VT is connected with the leads of the electrodes to the corresponding terminals of the device. Switch SA1 sets the structure of the transistor. In this case, a power source is connected to the transistor in polarity corresponding to its structure. Next, the transistors are checked, observing the following order: the collector junction is checked for breakdown; set the base current Ib equal to 1 mA; measure the static current transfer coefficient h 21e
Measurements of these parameters of medium and high power transistors illustrate the circuits shown in fig. 2.
The collector transition is tested by pressing the SB2 Breakdown button. At the same time, resistor R4 and milliammeter RA1 are included in the collector circuit of the tested transistor VT, the negative terminal of which is connected to the power source, and resistors Rl - R3 are connected in parallel to the collector junction (Fig. 2, a).
At this time, the sliders of the variable resistors R2 and R3 should be in the right (according to the diagram) position. The strength of the current flowing through the chain of resistors Rl - R3 does not exceed 50 μA, which practically does not affect the readings of the milliammeter. Resistor R4 limits the current through the milliammeter to 1 mA, thereby preventing its needle from going off scale in the event of a breakdown of the collector junction of the transistor.
Milliammeter readings less than 1 mA indicate that the collector junction is working, and when it breaks down, the milliammeter needle will always be set to the extreme right division of the scale. In the event of a break between the terminals of the collector and base electrodes, the device will only show the current passing through the resistors Rl - R4.
The base current /b, equal to 1 mA, is set by resistors R3 Coarsely and R2 Exactly with the SB2 button pressed. In this case, an insignificant initial collector current and current through the resistors Rl - R3 flow through the milliammeter (Fig. 2, b), which, when measuring the h21e coefficient, will be the base current Ib of the transistor under test.
The static current transfer coefficient is measured by pressing the SB4 h21e 300 button or, with a small numerical value of this parameter, the SB3 h21e 60 button. In this case, the button contacts connect the emitter of the transistor to the positive (or negative, if the transistor p-p-p structures) to the conductor of the power source, and parallel to the milliammeter - a wire resistor R5 (or R6), which expands the measurement limit (Fig. 2, c). The collector current of the transistor under test will approximately correspond to its static current transfer ratio. The error arising from the simplification of switching circuits of the device does not affect the selection of pairs of transistors for the output stages powerful amplifiers ZCH.
When testing transistors of the p-p-p structure, a milliammeter is included in the circuit of its emitter,
The design of the device is arbitrary. Resistors R1 and R4 type MLT-0.5, R2 and R3 - SP-3. Resistors R5 and R6 are made from high resistivity wire with a diameter of 0.4 ... 0.5 mm. Switch SA1 - toggle switch TP1-2, pushbutton switches SB1 - SB4-KM2-1. Power-on indicator HL1 - switching lamp KM24-90 (24 Vx90 mA).
By selecting the resistor R4 with the collector and base clamps short-circuited and the SB2 button pressed, the milliammeter needle is set as accurately as possible to the extreme right division of the scale.
To adjust the resistances of resistors R5 and R6, you will need an exemplary milliammeter for a current of 300 ... 400 mA and variable wire resistors with a resistance of 51 ... 62 and 240 ... 300 Ohms. An exemplary milliammeter, a transistor tester milliammeter, a resistor R5 and a variable resistor of 51 .... 62 Ohms are connected in series. Turning on the power source, a variable resistor sets a current in the circuit equal to 300 mA, while at the same time making sure that the milliammeter needle of the device does not go off scale. After that, by adjusting the resistance of the resistor R5, the arrow of the milliammeter of the device is set to the extreme right division of the scale. Then the variable resistor is replaced with a resistor with a resistance of 240 ... 300 Ohms, the resistor R5 with a resistor-R6 and in the same way the current is set to 60 mA in the circuit, and the arrow of the milliammeter of the device is set to the extreme right mark of the scale.
When the SB4 button is pressed, the deviation of the arrow of the tester's milliammeter on the full scale corresponds to the static current transfer coefficient of the transistor 300, while the SB3 button is pressed - 60.
