In the magazine “Radio Amateur” No. 3, 2001, I read an article by S. Gordienko “A device for testing semiconductor zener diodes” with a simple circuit. But I was not satisfied with the power supply from 6 volts, as well as the transformer from the network adapter, which has significant weight and dimensions.
Therefore, I made a version of the zener diode identifier, in which I used a pulse transformer on a ferrite ring and reduced the supply voltage to 1.5 volts:
With a supply voltage of 1.5 volts and a current consumption of about 36 mA, the open circuit voltage at the output of the set-top box was about 150 volts. When powered by a 1.2 volt battery, the output voltage drops to 130 volts.
The set-top box remains operational when the supply voltage is reduced to 0.4 volts (at the same time, the output voltage is correspondingly reduced), but this allows, in many cases, to use even dead elements to power it.
The transformer is wound on a K10x6x5 ferrite ring. The primary windings are wound in two wires PELSHO 0.31 2x10 turns. The secondary winding is also wound in two PETV wires 0.19, 105 turns each. Then the windings are connected in series (the beginning of one and the end of the other). The diameter of the wire can be taken smaller than in my version.
I removed the transistor and diode from the flash of a disposable camera. But you can also use other n-p-n transistors (preferably with a low saturation voltage). In this case, you only need to select the value of resistor R1. Decreasing the resistance of the resistor leads to an increase in output voltage and current.
The diode can be replaced with any high-voltage rectifier with a short recovery time (capable of rectifying at frequencies of hundreds of kHz).
I tried installing a KT315G transistor and a 1N4007 diode. But with them, the output voltage and efficiency of the device decreased by a third.
The set-top box parts were placed on a printed circuit board measuring 60x23 mm:
The body of the console was glued together from sheet plastic 2 mm thick:
The battery compartment cover is secured to the case with two M2 countersunk screws.
To connect to the multimeter, I used plugs from its probes, which I soldered directly into the board. To connect zener diodes, I soldered sockets from the 2RM connector into the board, into which you can also insert remote probes or toothed alligator clips:
To check the zener diode, it is first connected to the set-top box, and then its power is turned on. The multimeter should be set to a 200 volt pedal. Its readings will be equal to the stabilization voltage of the zener diode:
There is no need to be afraid of mixing up the polarity. In this case, the device will only show a direct voltage drop across the zener diode of 0.6...0.8 volts (if it is not double-sided).
Using this attachment, you can also test low-voltage diodes to determine their breakdown voltage. Such diodes can be used in reverse connection instead of high-voltage zener diodes.
I used this zener diode probe for a long time. It has only one single drawback - it requires a landline telephone line, because it is powered from it, from its 50 volts with a unique current of 20 milliamps. It is obvious that the line voltage covers the entire visible voltage range of zener diodes used in practice by radio amateurs. There are no words for how convenient it is.
But the phone was gone, but the need for measurements remained, a new probe had to be made, and the circuit underwent changes only in terms of the number of electronic components involved, and in the direction of reduction. The probe will be powered from a laboratory power supply with an adjustable output voltage of 0 - 30 volts.
The kit required for manufacturing includes:
Holes are pierced in the covers with an awl, in one at a distance of 19 mm from each other and pins are installed in them, in the other at an arbitrary distance for connecting contacts. Electronic components are connected to each other by soldering (look at the photo and diagram).
The component assembly is installed in place and secured with nuts. One of the caps is screwed onto the thread, the second is put on “tightly” on the opposite side of the neck (it turns out like a latch, you just need to trim the edges correctly to “catch” the required diameter). And don’t forget to organize a power supply.
We put information stickers on the top cover of the finished probe body and it can be used. The probe circuit and method have been tested over five years of operation. This is exactly the case when a product is characterized by the saying “both cheap and cheerful.” The time required for its production is no more than an hour.
The procedure for using the probe is as follows: the probe is inserted with pins into the corresponding sockets of the multimeter, the measurement limit is selected “20” or “200” volts DC depending on the expected stabilization voltage of the zener diode. Next comes the connection to a DC source, the best option is a power supply with adjustable output voltage from zero and current up to 1 ampere. We correctly place the tested zener diode on the contacts, slowly increase the output voltage and look at the multimeter display. There we will see the stabilization voltage of the zener diode we are interested in. But everything will work out, even if there is no regulated power supply, you can use ordinary batteries, connecting them in series until the required voltage is reached.
I made a video a long time ago on the topic of a tester for zener diodes, the device is quite popular and is in demand among radio amateurs, so I decided to write this article.
Unlike the previously mentioned video, this project uses ready-made modules from China, which makes assembly easier.
So, first of all, about the components, looking ahead, I’ll say that the cost is only a couple of dollars, and all the links to purchasing the necessary components will be at the end of the article.
We need a boost DC-DC converter based on the MT3608 chip.
The board allows you to get an output voltage of 28-30 Volts, a minimum input voltage of 2-2.5 Volts.
The second board is also from China, it is a charge controller for one can of a lithium-ion battery with protection, built on the basis of the TP4056 microcircuit.
Lithium ion battery, any standard will do, even from a mobile phone.
In my version, the battery was replaced with a rechargeable nickel-metal hydride battery, AAA batteries, I took 3 of them, then connected them in series, and in the end I got an analogue of one can of a lithium-ion battery. This decision is due to the limited space in the housing.
I decided to make the case itself compact; a cheap power bank for a dollar served as the donor; later the case was sharpened in places so that the filling would fit.
We also need a mini digital voltmeter, in my case this voltmeter measures voltage up to 32 volts, and does not have a third wire (measuring), i.e. connects directly to the power source, in our case to the zener diode, in order to measure the stabilization voltage of the latter.
It must be remembered that the voltmeter consumes some current, therefore, in order not to overload the zener diode, it is advisable to use a voltmeter with three wires - two power wires and one for the meter.
It is my voltmeter that can easily be converted to three wires; the Chinese simply connected the plus power supply with the measuring wire.
By the way, to operate such voltmeters you need a voltage of at least 4 volts; in order for the readings to be correct, the minimum supply voltage should be around 4.5-5 volts, the maximum - 32 volts, so the voltmeter is powered directly from the output of the boost converter , the battery voltage is insufficient.
In this regard, our device can test zener diodes whose stabilization voltage is no more than 30 volts.
A switch or button without locking, for any current, you need a button to turn on the device, the test takes a couple of seconds.
An electrolytic capacitor of 50 volts with a capacity of 10 to 47 μF, it is connected to the output of the converter and is designed to smooth out ripples, this is necessary for the correct operation of the voltmeter.
A 2kOhm resistor is needed to limit the current through the zener diode, otherwise the latter will burn out. The calculation of this resistor is made based on several values; for our case, we need a resistor from 2 to 2.2 kOhm, a power of 0.25 watts.
Solderless mounting panel for microcircuits in DIP8, DIP14 or DIP16 housing, there is not much difference.
The zener diode to be tested is placed in this socket.
So, the boost converter module on the MT3608 chip, as already said, can provide a maximum output voltage of 28-30V, which can easily be raised to 40V.
Let's look at the diagram of the modules of this scarf. We see a constant resistor connected in series with the trimmer.
Now we unsolder it and put a jumper in its place.
The next step is to apply a voltage of about 4 volts to the input of the board, simulating a connected lithium battery, connect a multimeter to the output of the board, then rotate the trimming resistor 10 steps counterclockwise.
I should note that only after 10 steps the module will begin to increase the voltage (yes, strange, but I didn’t come up with that). Then we boldly rotate the trimmer to a voltage of 35 volts, after 35 we rotate it very carefully and slowly until the multimeter shows a voltage of 40 volts, if we increase it further, the current consumption instantly increases and the microcircuit will burn out (this will happen at a voltage of 45-50 volts).
Thus, our 30-volt board began to produce as much as 40 volts, but I strongly advise against doing this; it’s better to leave everything as it is.
It's just a matter of small things, we'll put everything together according to the diagram.
The switch was installed on the side, the socket and voltmeter were located on the back cover, which now became the front panel.
In amateur radio practice, many small glass diodes often accumulate, the designations of which are not always clear; among them there may also be zener diodes. A similar tester is designed to find these, as well as to identify more accurate stabilizing data of the zener diode being tested. The purpose of this device is to test unknown zener diodes, which may have a voltage higher than 30 volts, which means that they cannot be tested with a regular power supply or tester.
The circuit was copied from another one taken from the Internet, simplified and drawn to resemble a 0-100 V digital indicator from China, with the pins marked since not many people understand how to connect it here. Of course, if they are on sale and inexpensive, then why not use them, you get a compact and functional device that is useful for a radio amateur, which is sometimes very necessary.
The tester was based on the housing from the MIP-R alarm power supply unit; you can take any other one that is suitable in size. On the front panel it is planned to attach a board with a socket for microcircuits, and another board for checking cmd zener diodes. Since the device itself is very compact, it can be built in conveniently; the dimensions will depend only on the battery used.
A small scarf has been developed for the device, on which all the parts are installed. The transformer is taken ready-made from a cell phone charger, the secondary step-up winding on it is marked with the highest resistance.
Above, look at the result of checking the operation of the device, a 5.1 V zener diode test.
Information for beginner radio amateurs:
There is no function for checking zener diodes in multimeters.
And don't look for a multimeter with a Zener meter. But it is clear that it is necessary to check. Moreover, even a serviceable component must be tested for the actual stabilization voltage parameter. The truth is simple. Just how, so as not to assemble a separate device and not to use one of the existing methods, which take, albeit not very much, but a relatively long time, and not only in terms of the time of the test, but also in preparation for it. But one well-known humorist turned out to be right, claiming that throughout the entire post-Soviet space people have no problems with “thinking”.
I decided to assemble the device as an attachment to a multimeter, and a compact one at that. Housing from packaging of safety blades " Schick" The socket for the end of the telephone cable matched both in size and color, and we managed to attach the power button to it. Given some of the uniqueness of the case, the assembly had to be done, so to speak, in a “step-by-step” manner.
Step one
Step two- removing all of the above into the housing niche and installing the pins in place (forming an improvised plug for connecting the probe to the multimeter) by using a threaded connection on them and two M4 nuts for each. The distance between the centers of the pins is 18.5 mm.
Step three- installation of LEDs and limiting resistors.
I hid the contents “out of sight” and screwed on top suitable contacts for connecting the zener diodes being tested. The contacts can be rotated around their axis and thereby change the distance between them depending on the length of the component being tested. I'll try it out:
Imported zener diode BZX85C18- fell just short of the stated parameter.
But domestic KS515A didn’t disappoint, as they say, “right on the bull’s eye.” And now I have it in my arsenal Schick arny zener diode tester.))
The multimeter itself, of course, can be replaced with any voltmeter, even a dial voltmeter - this will be useful if you often have to check such parts while working in the workshop. I wish you success, Babay. Russia, Barnaul.
