History of one report

One beautiful sunny day, the management received a task: to repair the device (unexpectedly, it stopped working, although of course there were no signs of trouble), figure out how it works, and think it might be worthwhile to produce and sell such products. Once upon a time, this device was manufactured by an unknown developer who was simultaneously working on electronics for spacecraft. Someone's great-grandmother was treated with this device, and maybe even great-grandfather. The treatment, as usual in such cases, was extremely effective, on the verge of fantasy, of course, according to eyewitnesses, who are unlikely to be able to see firsthand. In general, despite the high efficiency of the method, no one could provide the results of clinical trials.

When I got the device in my hands, my amazement knew no bounds, but since it was not our method to give up difficulties, I decided to approach the matter with humor. Although no one required to write reports on such issues, an exhaustive report was written. I hope he cheers you up. Actually, the report itself is below.

We disassemble the fossil device. It is difficult to date the device, according to the remains of sludge inside the body, the artifact can be attributed to the Neolithic era, however, a radiocarbon analysis of organic residues was not carried out. The device is supposedly intended for electrical neurostimulation for medical purposes. So, according to ancient beliefs, it was believed that the effect of electric current on the body can beneficially affect the health and well-being of the patient. This common opinion appeared when the ancient hominids (Hominidae) noticed that their brethren, exposed to the electric eel (Electrophorus electricus) during fishing, felt somewhat better than the others. Their physical abilities increased significantly (they jumped very high, regardless of how deep they were at the moment of contact with the Electrophorus electricus). A prolonged effect on psychophysical activity was also noted. Hominidae became much more attentive and neat. This led to the fact that at one point, acne began to be used for medicinal purposes. According to a similar scheme, the ancient hominids began to use Hirudo medicinalis, but this is a completely different story.

In the 30s of the XX century, psychiatrists recalled methods of treating distant ancestors: they began to use electroconvulsive therapy (ECT) to treat severe forms of mental illness. At the end of the 20th century, instead of an electric shock, a chemical shock was more often used, and electroconvulsive therapy was used only as a last resort. So far, progressive mankind has not abandoned ECT as a form of treatment for mental illness, which raises reasonable doubts about its progressive nature.

Let’s go over to the object of study, the photo is shown in Figure 1.


Figure 1. Photo of the device in the disassembled state

The device has a plastic case with two electrodes. The controls and the power connector are on the side. Also included with the fossil was a power supply, on the housing of which a 5V output voltage was indicated. Oddly enough, the unit produces all 9.6 volts.

At the output, there is a connector for connecting a block instead of a “crown” with innovative fasteners that deserve special attention, and possibly implementations in other projects (Figure 2).


Figure 2. Innovative power supply Velcro closures

The device is equipped with a switch, the sacred meaning of which, apparently, is to switch the operation modes of the device, however, the connection point of one of the contacts (archaeologists accidentally cut off the wiring) is not obvious. The switch itself merely adds a resistor to the circuit. In general, the control panel of the device is very ergonomic, made according to all the canons of sensualism. The signal generator itself is made using a wall-mounted installation, a tangle of parts lies in a box and even pretends to work (Figure 3).


Figure 3. Mounting

Restore the circuit of the device. It is presented in Figure 4. As you can see, the device is a generator with two transistors. The method of signal generation would clearly raise questions from electric eel, but this is not about that now. One of the contacts of Switch1, as we see, is broken. Presumably, resistor R3 shunts either resistor R2, or the entire chain of R2-C2, or maybe something else. We will try to start the device and see if it works in principle, and if it works, then it gives out to its wonderful electrodes, which are held on a powder that once was glue (Figure 5).

The device worked, and even began to issue high-voltage pulses to the electrodes.


Figure 4. Restored device diagram

We determine the values ​​of the passive elements, the types of transistors and restore the device circuit completely.



Figure 5. Electrodes

One of the contacts of Switch1 was disconnected, therefore, at first glance it was not possible to restore the circuit. After clarification of all the ratings, it seems not logical to shunt the resistor 150 Om with the resistor 430 kOm. Consequently, either R2-C2 chain or, more likely, R4 resistor was shunted by this resistor. The complete circuit is now shown in Figure 6.


Figure 6. Electrical schematic

Remove the waveform from the output of the device. The signal that he gives to his electrodes. In this case, we set the minimum, there is no load on the electrodes. At the output, we see a pulse consisting of several oscillations, a pulse duration of 250 μs. If there is no load on the electrodes, the signal amplitude at the output is about 700 volts. The waveform is shown in Figure 7. The first burst has a rather bizarre shape, it is shown in detail on the last waveform in Figure 7. In general, the signal at idle resembled the signal received from the device N (we remove the brand of the device for electrical neurostimulation from the report, let us advertise ourselves).


Figure 7. Waveform at the electrodes. Idling

We will carry out the same measurements under the “load”. The first phalanx of the index finger of the right hand acts as a load. As you can see, the pulse sagged, now with a minimum output power, the signal amplitude is about 50 volts, the signal shape has also changed. You can admire the signal itself in Figure 8. We will not check at maximum power, we are sorry for the fingers, they will print a report as well.


Figure 8. Waveform at the electrodes. Electrodes on the skin

Let's see what happens on the output transistor. Figure 9 shows the waveform of the collector voltage of the transistor and the current through it. Based on the waveforms, we can say that the transistor opens at 50 μs. All other vibrations are due to the oscillatory circuit formed by the transformer winding and capacitance C3.


Figure 9. The voltage at the collector of the output transistor and the current through the transistor.

Let's look at the base signal of the transistor VT2. The oscillogram from it is presented in Figure 10. As you can see, there it saw. At the moment when the voltage at the base of the transistor decreases to the unlocking level, the transistor opens, causes a pulse opening of the transistor VT1, and then closes. The voltage at the base with the help of circuit magic rises, after which the capacitor C2 is discharged through the resistor R4. Thus, we get pulses with a period of 100ms (frequency 10 Hz). If you close the switch switch1, the resistor R3 will also participate in the discharge of the capacitor. Then the output pulses will go about 5 times faster (about 50 Hz).


Figure 10. Voltage based on VT2 transistor

Well, in the end, the device was successfully repaired and can continue to shock patients with new and not very new patients.