Autonomous indicator of radioactivity without batteries

The article proposes a variant of the design of a radioactivity indicator built, for the most part, from the simplest and most widespread parts. The proposed design of the radioactivity indicator receives energy from a hand-held electric generator, which is used as a stepper motor with a gearbox. The device uses a sensor type CTC-5.

Autonomous indicator of radioactivity without batteries with head phones TON-2M

Autonomous indicator of radioactivity without batteries with head phones TON-2M

Now you can buy a wide variety of models of indicators of radioactivity [1]and electronics lovers have developed a large number of designs for self-assembly from simple “rattles” [2-6]to devices that are not inferior to factory samples [7-8]. But most designs require either a chemical current source or a connection to the mains for their operation. Thus, in the event of any truly great disaster, many of these devices will either immediately become useless, or quickly exhaust the energy reserve in their autonomous power supplies, for which replacements will be difficult to find. Strictly speaking, there is an electroscope-based dose rate meter design that uses a PVC tube and woolen fabric as an energy source. [9]. But this design is very demanding on the quality of manufacture and is suitable for assessing only very high dose rates of ionizing radiation, such as those that occur during radioactive fallout in the first hours and days after a nuclear explosion. [10].

In general, the radioactivity indicator consumes relatively little energy, so that it can be powered from a hand-held electric generator, as was done in the DP-62 device. [11].

Autonomous indicator of radioactivity without batteries

Autonomous indicator of radioactivity without batteries

As an electric generator, the author used a stepper motor from a CanoScan 4400F scanner with a standard gearbox. The color marking of the motor leads is shown in the diagram. A transformer T1 is connected to the electric motor, which increases the voltage generated by the generator to about 150-200 V (depending on the shaft speed). The transformer was taken ready-made from the author’s amateur radio reserves, it is marked 1.702.087-01. The primary winding has a DC resistance of about 30 ohms, and the secondary about 1500 ohms. After the transformer, the voltage is fed to the input of a voltage doubler, assembled on capacitors C1-C2 with a capacity of 0.1 μF, rated for a voltage of 630 V and diodes VD1-VD2 of the HER108 type. The voltage doubler charges capacitors C3 and C4 of the K73-11 type with a capacity of 0.47 microfarads, designed for a voltage of 630 V. From them, through the resistor R1 of the MLT-0.5 type with a resistance of 2.7 MΩ, the Geiger counter B1 of the STS-5 type is powered. The terminals for connecting the Geiger counter B1 are cut out of tin. In parallel with the resistor R1, TON-2M headphones are connected through a mica capacitor C5 of the KSO-2 type with a capacity of 1000 pF, designed for a voltage of 500 V. Of course, it is not necessary to use a capacitor of the KSO-2 type, it can be seen with any film capacitor of suitable voltage and capacitance. The socket X1 for connecting telephones is a standard electrical socket without a cover.

Most of the components are placed on a pseudo-printed board.

device pseudo-printed circuit board

device pseudo-printed circuit board

A section of a cable channel with dimensions of 175x60x35 mm was used as a housing. A stepper motor with a gearbox is placed outside, for which a special hole is made in the body.

Placement of a stepper motor with a gearbox

Placement of a stepper motor with a gearbox

Inside the case there is a transformer, a board, a Geiger counter and a block for connecting headphones.

Placement of Radioactivity Indicator Parts

Placement of Radioactivity Indicator Parts

The ends are closed with L-shaped elements cut from the same cable channel.

end cap

end cap

The end elements are held in place with furniture corners MK 16x16x12 mm. The tube of the Geiger counter STS-5 is fixed with clamps cut out of packaging plastic. A fully assembled device starts working immediately, it does not require any settings. During operation, it is necessary to rotate a large gear, which through the intermediate gears drives the shaft of the stepper motor. In principle, this can be done with a finger, but experience shows that in this case a patch must be glued to the fingertip, otherwise the user is guaranteed a corn on the finger. Another option would be to wind several turns of a thin, strong cord around the gear shaft. In this case, the rotation of the generator shaft is ensured by the gradual winding of the cord. With some skill, you can wind a few turns back onto the large gear shaft quickly enough so that the capacitors C3 and C4 do not have time to discharge.

Device for uniform rotation of the generator shaft

Device for uniform rotation of the generator shaft

Since the sensor is located inside the body of the device, the device is sensitive to gamma radiation. The author has neither cesium-137, nor cobalt-60, nor even strontium-yttrium control source B-8 at home [12]therefore, the performance of the device was tested on uranium glass beads [13]which were located directly on the meter case, since they give weak beta radiation, which does not penetrate well through the device case.

Testing the instrument with uranium glass beads

Testing the instrument with uranium glass beads

With this placement of the “control source”, the increase in the number of clicks in the phones is clearly visible. The number of clicks in 40 s should approximately equal the dose rate in microroentgens per hour [5]. A similar exemplary method for estimating the dose rate of ionizing radiation is used not only in home-made designs, but is also found in the designs of industrially produced devices. [14-15]. Of course, counting clicks in headphones is much less convenient than just reading the readings on the screen, but this inconvenience is the downside of the simple design of the device.

In addition, it should be noted that although the considered construction is very simple (maybe even too simple), it still has two very scarce components. Nothing can be done with a Geiger counter, if you are going to detect ionizing radiation, then a particle detector of ionizing radiation is necessary, but now high-resistance TON-2M headphones, although they are not some kind of special rarity, but, to put it mildly, do not lie on counter of every electronics store.

In conclusion, I would like to note that the history of previous radiation accidents and disasters clearly indicates that in an emergency many people are ready to go to extremes, some argue in the spirit of the fact that since we do not see radiation, then it will not do anything to us [16], while others, on the contrary, panic from each click of the Geiger counter. However, there is nothing surprising in this, given that sociological surveys demonstrate a monstrous level of scientific illiteracy of a significant part of people, even on the most elementary issues. [17]. In general, the issues of dosimetry and the biological effect of ionizing radiation are very difficult. [18-22] and only a good understanding of the problem will make it possible to understand what should be avoided at all costs, what should be feared, and what gives risks that are less than those that most people usually ignore [23-24]. At the end of the article, I would like to wish everyone that in ordinary life we ​​all come across only sources of radiation such as uranium glass [25]potassium fertilizer [26] and similar items.

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