Chernobyl, exports from Eastern Europe, the dumps, the lack of screening services, ignorance, are all factors that make the sometimes increases in radioactivity proportions that go well beyond safety limits. The Geiger counter that we propose in this article will help you protect yourself from its harmful effects by allowing you to control, among other things, your food and your environment.
Although many years have passed since the catastrophic explosion of the Chernobyl nuclear reactor accident in 1986, the invisible radioactivity spread on this occasion, still continues to produce its harmful effects.
Few people know that different countries of the East have continued to export to Western Europe amount of grain, livestock and scrap metal at low prices only because they were contaminated by radioactivity.
Not so long ago, a English company has acquired recklessly metal debris which, when put into blast furnaces, have produced an invisible radioactive cloud that has joined the South of France and northern Italy.
In October of last year, officials from the customs Niirala in Finland found in a train from Russia, trunks containing radioactive uranium.
These same customs, shortly after, intrigued by an unusual passenger on a bus direct, Germany, France, Italy, were checked with a Geiger counter, charging toys and transported from small enterprises of Belarus and Ukraine. They noted the presence of radiation 4 times above the limits set by international standards. If these toys were entered their destination, they would surely endanger the wholesalers, merchants, families and children.
exist in Finland and Germany specialized groups that control, using Geiger counters, all scrap metal, grain and finished products from outside. Many are unaware that there
Serbia new locations that are stored radioactive uranium waste.
If these sites had been hit, even unintentionally, by a missile, it would have meant to spread immediately looks a radioactive cloud, which event we would have surely been informed late.
recently in Kosovo, it was found an increase in radioactivity caused by projectiles with depleted uranium used because they are more penetrating than ordinary bullets.
We can not ignore that France has a lot of radioactive material from hospital and industrial waste. Newspapers have often reported that the companies responsible for their treatment, instead of storing them in landfills specially made for this, were dumped in landfills Wild counting on the lack of verification systems and control.
We would not want to appear alarmist, but if we were going to inspect them with a Geiger counter abusive scattered all landfills in our area, we could face a radioactivity of 20 to 30 times greater than that of natural radioactivity.
Several carriers have confessed having discharged into the sea all the radioactive slag that had been given, apparently without realizing the seriousness of their actions and consequences that may result in the form of pollution of the flora and fauna Aquatic. Ask the authorities
of Commons if they have a Geiger counter, the answer is negative.
In some cases, they do not even know what it is or how to use it and where to get one! If in our country, the number of people with tumors is steadily increasing, we must, in part to the presence of the radioactive pollution, which unfortunately is invisible.
For all these reasons, we believe it is timely to present a draft Geiger counter. With this device you can check if the food you put on the table are more or less radioactive, and if you are interested in ecology, you can check the "health" of your environment.
If your research lead you to discover a radioactive source, you should immediately notify local authorities (police, gendarmerie, mayor ...).
Do not be surprised to find radioactivity in many everyday objects, such as sleeves used in lamps to camping gas, money and some quality dishes. There are still a little time, industries using thorium and radioactive cobalt to make these products more durable!
Radioactivity
Before proceeding to the wiring diagram and the practical realization of this project, we would like to explain what extent a Geiger counter and for that, compared to a nuclear emery wheel, like that found in all mechanical workshops, also called bench grinder.
When you press the wheel a piece of metal (see Figure 1) it separates from the latter a thin incandescent filings, which, in our example, can be compared with radioactive isotopes.
He who is very close to the wheel will be burned, one that is furthest will receive a small amount chip, it will feel discomfort but it will not be burned.
If we can see and feel on our skin the effects of iron filings glowing when we met, we can not say the same in the case of radioactive isotopes. They are, precisely because we can neither see nor feel, much more dangerous because they damage, without our knowledge and irreversibly, the immune system of our body.
We still say that if iron filings off shortly after falling to the ground, it is not the same for fine radioactive dust which remains "on" beyond 30. Throughout this period it behaves like a tiny radioactive source.
If this invisible radioactive dust falls into a pasture, all the vegetation that will grow radioactive and cows, sheep and goats could feed on it will produce radioactive milk, then slaughtered, will provide the meat and radioactive on.
Radioactive isotopes are invisible to detect the radioactivity using a special tube called "Geiger tube", named after the German physicist who, during his experiments, found that while some gas mixtures were excited by a radioactive isotope they became conductors of electricity.
Making a Geiger tube is not easy, because you have to find a metal that lets smaller radioactive particle and also because you must choose a particular mix of gases that can diffuse rapidly and begin to count all successive isotopes.
The type of metal and the mixture determine the sensitivity of the tube. Thus, a given type of tube can not be substituted for another. Geiger counters in modern we find it a microprocessor which converts the number of radio-isotopes counted milliröntgen / hour (mR / h).
Returning to our example of the emery wheel. The tube Geiger count every grain of filings that incandescent reach.
must indicate that the quantity of radionuclides that reach the tube, as well as iron filings, is not regular. If in the first second reach six isotopes in the next second it can not happen that 4 in the third second 10 in the fourth second 5. For this reason, in our Geiger counter, we integrated a memory that indicates the maximum amount of Isotopes captured.
On the display, we do not want to read the number of isotopes captured, but the value of radioactivity expressed as milliröntgen / hour. The first operation that must be done is to freeze the number of pulses captured in 1 hour in the presence of a determined value of radioactivity.
Knowing that the tube selected, subject to a radioactivity of 0.1 for 1 hour counts milliröntgen 23,760 pulses, to know how much it would count pulses in one second, divide this number by 3600, that for the entire second contained in 1 hour.
23760: 3600 = 6.6 pulses per second the measure in a time of one second is not very precise because the number of isotopes varies. We chose for our sample, a period of time of 10 seconds during which we will count 66 pulses well.
If we wanted to know what value is a pulse of radioactivity, we must divide by 66 and 0.1 milliröntgen we get: 0.1: 66 = 0.0015 IC2 milliröntgen The microprocessor used in the Geiger counter, give the conversion of pulses counted in the space of 10 seconds milliröntgen / hour by multiplying by 0.0015.
Thus, if the counter has 8 isotopes, the display will show the number of: 8 x 0.0015 = 0.012 milliröntgen / hour If has 20 isotopes, we have on display: 20 x 0.0015 = 0 , 0030 milliröntgen / hour So every 10 seconds, we will see on display the exact value of radioactivity without having to wait 1 hour.
It is true that for the most accurate measurement possible, proceed to 3 or 4 steps and employ average.
Figure 1: To explain what a Geiger counter measuring radioactive isotopes compared to the tiny chip incandescent dispersed by emery wheel which rotates on a piece of iron. Whoever is near the wheel will be achieved through a multitude of glowing particles and will be burnt by cons, one located farthest receiving less than glowing particles incur no risk. The Geiger counter totals the amount of "incandescent particles (radioactive isotopes) that reach the body within 1 hour. 
Figure 2: On the top of the case we have reproduced a table with the values of dangerousness milliröntgen / hour. The left pushbutton is used to find the maximum value of radioactivity measured during the day and the right is used to reset the stored values.
Electrical diagram
Figure 5 shows the wiring diagram Complete the Geiger counter.
Geiger tube to be supplied with 400 volts, the first step is to raise the 6 volts of power (4 x 1.5 V) at 400 volts. For this we use the floor consisting of transistors TR1 - TR2 - TR3 and the ferrite transformer T1.
In the secondary winding of T1, to the left, we take an AC voltage of about 140 volts with a frequency of 12 kHz. This voltage is then raised by the rectifiers DS1 - DS2 - DS3 and capacitors C8 - C9 - C10. Therefore we obtain the output voltage well above the 400 volts required. To stabilize
the tension on the exact value of 400 volts, we connected between the output of the Geiger tube feeding and the base of TR1, four 100-volt zener diodes connected in series which realize a function similar to a zener diode of 400 volts. The zener diodes
polarize the base of transistor TR1 with the excess voltage from the 400 volts.
Thus, the transistor becomes conductive, will modify, through TR2, the bias on the base of transistor TR3 in order to establish the rectified voltage on the exact value of 400 volts.
Do not attempt to measure this voltage with a voltmeter usually because you could get there. Indeed, the voltmeter has lower internal resistance than the Geiger tube and for this reason you will read only a few volts. This
voltage of 400 volts is applied to the positive pin of the Geiger tube through resistor R 5 to 10 megohms. The battery negative is connected to ground through a resistance of 220 ohms.
Each radioactive isotope present in the air cause the conduction of the Geiger tube and in this way, across the resistor R1 we get a small positive pulse. This tension is not sufficient to drive the ST6 microcontroller.
For this reason, this pulse is applied through resistor R2 the input of NAND gate IC1 / A mounted inverter. Then follow the two NAND IC1 / B - IC1 / C used as monostable oscillator.
On the output of this shot, we have a large enough positive momentum that we can apply on input pin 10 of microcontroller IC2 ST6 a suitably programmed for the Geiger counter.
This microcontroller is the brain across the counter because it converts the pulses recorded directly milliröntgen / hour and visualized on the display.
In addition to this function, the microcontroller also stores the maximum radioactivity found during the day. Thus, in the evening, home from work, if you read 0.009 mR / h and that pressing the button P2 "MAX" will read 0.030, then there was a slight increase in radioactivity may be due to rain or radioactive to sunspots or cosmic winds. The P1
push "RESET" is used to erase the memory without having to turn off the circuit, so you can control, from the following, if the radioactivity has increased or if it has lessened. The same microcontroller
still provides other functions. For example, it constantly monitors the battery voltage and when discharged it shows on the display with "b-Lo" which means low battery (low battery).
If you open the switch S1, connected to pin 7 of microprocessor, we can note that the buzzer sound is not as a value of 0.039 mR / hn has not been exceeded.
When the radioactivity reaches the value of 0.040 mR / h, which indicates a low radioactivity, the buzzer will sound pre-alarm in the form of 5 consecutive beeps. Shortly after, the sound ceases and if the second reading is identical to the first or values above are detected, the buzzer will resume.
This additional function is useful for all control stations who wish to keep working 24 hours on 24 Geiger counter to see if the atmospheric radioactivity exceeds a certain threshold because of an unexpected leak of radioactivity in any nuclear plant.
We think, given the proliferation of nuclear, it will not happen until shortly before we were in every house beside the traditional thermometers and barometers, a Geiger counter to check that the radioactivity increases above the natural level.
To perform this monitoring, it simply set the Geiger counter near the window and to avoid having to constantly change the batteries, we can power the camera with a stabilized voltage of 5 volts levied on a diet as LX.1335 model example.
The circuit is operating normally, even with a voltage of 5 volts, because the microprocessor IC2 indicates that the battery is discharged only if the voltage drops below 4.5 volts.
As you can see the wiring diagram, the tab 9 of the microprocessor IC2 is fed by a small integrated circuit (see IC3), which behaves like precision Zener diode and causes a voltage drop of 2.5 volts.
When the batteries are discharged, we have on this pin voltage from 6 to 2.5 = 3.5 volts, if the batteries only provide 5 volts to this pin we will have 5 to 2.5 = 2.5 volts.
If this voltage drops below 2 volts, the microprocessor turns off the display and shows the inscription Lo-b to indicate the batteries are discharged and should be replaced.
It is noteworthy that the current consumed by the circuit is about 5 mA. Using four 1.5 volt batteries these will change approximately every two months, provided not to leave the power on 24 hours 24.
To complete the description, we add the three integrated circuits IC4 - IC5 - IC6 are driven in series by the microprocessor to turn on all counts of the LCD.
Note that this counter, unlike many others, needs no adjustment, which eliminates any difficulty.
Figure 3: Photograph of the plate of the Geiger counter for the display side. It may be noted at the top of the circuit, the two plastic spacers to fix the circuit board inside the cabinet. 
Figure 4: Photograph of the plate of the Geiger counter for the component side. Note, left, and the Geiger tube, bottom, the plastic battery holder for 4 x 1.5 volt. 
Figure 5: Diagram of the Geiger counter. The microprocessor IC2 shows directly the value milliröntgen / time on the LCD and as you can see, this counter is able to measure a radioactivity of only 0.001 milliröntgen / hour. We recall that the two electrodes of the Geiger tube are polarized. Thus, the positive electrode, which is the farthest some rings on the body of the tube is connected to resistor R5, and the negative electrode, which is closest, is connected to the junction of resistors R1 - R2.
Figure 6: The LCD is inserted into the two connectors 20 points in guiding the benchmark represented by a drop of glass or a notch to the left, as shown in Figure 8. If this display is oriented in the opposite direction, there appear no figures.
Figure 7: Pinouts integrated circuits as seen from above and those transistors BC.547 - BF.393 and small integrated circuit LM.336 seen from below, so the side or out of the 3 son connection. 
Figure 8: Implementation Plan components seen on the side of the display. The benchmark of the display is positioned on the left. 
Figure 9: In this photo you can see what is installed inside the enclosure, the printed circuit of Geiger counter. On the metal panel from the top you should screw the buzzer after drilling a hole to escape the sound of crackling radioactive pulses being detected. 
Figure 10: Implementation plan of components of the other side of the PCB. As you can see, the implementation does not present any difficulty.
Once editing is complete, the meter will run immediately, provided that you do not err in construction.
Note: To set the Geiger tube on the PCB must use both plastic hangers shaped ring.
Figure 11: Because the radioactive dust from falling on the earth on a regular basis, it is can be measured on two adjacent values of radioactivity significantly different. Iist R1 = 220 kΩ
R2 = R3 = 10 kilohms
27 kΩ R4 = R5 = 10 kW 10 MW
R6 = 22 MΩ
R7 R8 = 2.2 MΩ
= 1 MΩ
R9 = 10 kilohms R10 = 33 kΩ
R11 = 10 kilohms R12 = 680 Ω
R13 R14 = 3.3 kΩ
= 10 Ω 1 / 2 W
C1 = 100 nF polyester
C2 = 100,000 pF polyester
C3 = 39 nF polyester
C4 = 22 pF ceramic
C5 = 22 pF ceramic C6 = 100 pF
ceramic C7 = 2200 pF polyester
C8 = 10 nF cér. 1 000 V
C9 = 10.000 pF cér. 1 000 V
C10 = 10 nF cér. 1 000 V
C11 = 100 nF polyester
C12 = 100 nF polyester
C13 = 100 nF polyester
C14 = 100 nF polyester
C15 = 100 nF polyester
C16 = 1 μF. électrolytique
C17 = 22 microF. électrolytique
C18 = 100 nF polyester
C19 = 100 nF polyester
C20 = 100 nF polyester
C21 = 10 μF. électrolytique
XTAL = quartz 8 MHz
DS1 = diode 1N.4007
DS2 = diode 1N.4007
DS3 = diode 1N.4007
DS4 = diode 1N.4148
DS5 = diode 1N.4148
DZ1-DZ4 = diode zener 100 V 1 W
LCD = afficheur LC.513040
TR1 = transistor BC.547
= NPN NPN transistor TR2 TR3 = BC.547
BF.393
NPN transistor integrated circuit IC1 = C / Mos
4093 microcontroller IC2 = IC3 = EP.1407
LM.336
regulator integrated circuit IC4 = C / Mos 4094
integrated circuit IC5 = C / Mos 4094
integrated circuit IC6 = C / Mos = transformed T1
4094. mod. TM.1407
CP1 = piezo buzzer
switch S1 = S2 =
switch
P1 = P2 = push button
Geiger Tube CBM20
Practical realization
As you noted, the realization of the Geiger counter does present any difficulty. Once in possession of the printed circuit LX.1407, which is a double sided plated through holes, we recommend you first insert on the face visible in Figures 3 and 8, the two female connectors 20 points as supports for LCD display. After soldering the two connectors, printed circuit and the return on the other side, solder the 5 media integrated circuits (see Figures 4 and 10).
At this point, you can ride all the resistors, ceramic capacitors, polyester and electrolytic respect to the latter, the polarity of the two legs. If the body of electrolytic you do not find the + sign, remember that the tab from the positive pole is longer than the negative.
continue with the installation by inserting diodes, directing their reference ring as we can see from the layout diagram of Figure 10. Thus, the white collar of the diode DS2 is oriented capacitor C9. By cons, those diodes DS1 - DS3 are oriented to the capacitor C10.
Above the transformer T1, insert the zener diodes that you agree with the number 100 marked on their bodies with the side black to left.
On the right side of the PCB, insert the body diode DS4 Glass is directing the black ring to the left. For cons, the black ring of LED DS5 will be directed to the right.
At this point, take the two transistors BC.547 and insert them in slots TR1 - TR2 by orienting the flat side of their body to the transformer T1.
Down by capacitors C12 - C14, insert a small integrated circuit IC3 orienting to the right the flat part of his body. The marking of this circuit can be LM.336 or REF.25Z.
After these operations, insert the two integrated circuits IC1 - IC2, the 8 MHz crystal, fixing on the PCB by a drop of tin, up, the transformer ferrite T1.
Now return back the PCB (see Figure 8), mount the two pushbuttons P1 - P2 and the two switches S1 - S2. Then, insert the display on its two supports 20 pins.
This display is oriented so that its reference (see Figure 6) is left. If it had gone differently, no sign may appear. This marker is materialized by a small drop of glass or a small notch on the inner frame of the display.
If the legs of the display does not fit easily into the holder, it must align with the pressing lightly on the table. When inserting the display, be careful not to press the center of it with your finger because the pressure could break it.
To complete the construction, enter in their respective supports the 5 integrated circuits, taking care to guide their positioning mark as indicated on the wiring diagram in Figure 10.
On the body of the microprocessor IC2, you find a label that indicates marked EP.1407 ST6 microcontroller that is programmed for the Geiger counter.
In both holes left, install the two plastic hangers shaped ring that will be used to fix the Geiger tube.
Note: The pin positive Geiger tube is easily recognized because it is one that is farthest from the first ring on the body of this tube. Both son
supply are attached to the ends of the tube with two small clips or small pods. Do not weld the two son directly on the tube as it would be irreparably damaged.
As last operation, must be soldered to the printed circuit son both buzzer and those of CP1 battery holder that will be held on the printed circuit by the metal support in the form of U.
All this done, set the circuit board inside the cabinet using the two spacers adhesive (see Figure 3) then, on top of the box, press the top panel, which includes screen printing and secure using the nuts of the two switches S1 - S2.
After inserting 4 x 1.5 V type R6 in the battery holder, observing the + and - you can test the installation.
As we have already mentioned, the reading is taken every 10 seconds and the radioactivity you will find the cosmic radiation which can vary from a minimum of 0.001 mR / h to a maximum of 0.020 mR / h. If after half an hour you press the P2 button, you will see on the display indication of the maximum radioactivity detected by the Geiger tube.
As the saying goes "it is proud, not to be trusted is better." Thus, at home with a Geiger counter, you will not find more under the same conditions of the April 26, 1986, the day of the explosion of the Chernobyl nuclear power plant where we were informed with a delay of 10/12 days that a radioactive cloud had reached southern France and northern Italy and that is advised not to consume vegetables, fruits, mushrooms, cheese, meat and milk because they were radioactive while the majority population had consumed in peace all these products for almost two weeks.
thresholds radioactivity
After completing this Geiger counter, everyone will be interested to know the level of radioactivity beyond which we must begin to worry about acting. We submit below some useful information.
0.001 to 0.0030 mR / h = It should be noted that for millions of years man is constantly bombarded by radiation from the cosmos which never exceeds 0.020 mR / h. In the high mountains, it can reach a value of 0.030 mR / h value tolerated by the human body.
0.040 to 0.050 mR / h = Where in the atmosphere, we find these values, this indicates a slight increase in radioactivity should not even be considered dangerous. By cons, if such value is found on vegetables, meats, cheeses, etc.. It is advised not to consume.
0.060 to 0.070 mR / h = is the limit that we can rise into the air, but this is not a concern because it may mean a slight leakage of nuclear material occurred in any Central Nuclear. This can diminish in a very short time.
By cons, consider this threshold to be very dangerous if these values are measured on any food, because, by ingestion, we introduce into our body a small radioactive source.
0.080 to 0.090 mR / h = When air shows these values, we reach the critical threshold.
If we measure on meat, fish, milk or cheese it is advisable to store them in plastic bags and assign them to a local health agency should be enclosed in containers specially designed for this use.
0.100 to 0.150 mR / h = At these values of radioactivity, we can stay exposed approximately 1 month without it manifests itself in serious problems for the organization. Remain exposed for more than three months would, cons, very dangerous.
0.200 to 0.350 mR / h = We treat this value is already very dangerous. It is advisable not to remain exposed over a month and it is even possible to see manifest symptoms such as malaise and severe headache. Above
of 0.350 mR / h = We are already seeing significant damage to the body: hair loss, vomiting, increased anemia and possible malignancies.
It should be noted that the dose of radioactivity that our body can tolerate depends on exposure time.
If, in waste landfill, it is measured radioactivity than 0.350 mR / h we can stay close for a couple of hours because if we move away, the radioactivity rapidly back down below the minimum values of 0.020 mR / h.
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