Abstract:
A radiation detector that utilizes an unregulated power supply as opposed to a regulated power supply, since quantitative results are not required, only an audible signal, and an unregulated power supply is less expensive than that of a regulated power supply. The radiation detector includes a Geiger-muller tube, a nine volt DC power supply, a solid state oscillator with an output of 2 kilohertz, a high voltage power supply, and an audio amplifier.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a radiation detector. More particularly, the present invention relates to a radiation detector utilizing an unregulated power supply. 
     2. Description of the Prior Art 
     Nuclear contamination can stalk the land, leaving little indication of its presence until it is too late. Radiation is a silent phantom-like killer, in that it&#39;s usually not visible and is never audible. 
     If the area one lives in has been defiantly identified as a contaminated area, one may Just up and leave, taking one&#39;s family and all one&#39;s worldly possessions with them. In doing, however, one must also know whether one is carrying away contamination that might possibly harm one and one&#39;s household over a period of time. It could be in one&#39;s clothing, in one&#39;s hair, on one&#39;s body, and even inside one&#39;s body. One has to seek it out and then work on the problem of separating it from one&#39;s body before its has a chance to do serious damage. 
     If one lives in an area where nuclear contamination is a definite possibility, then one may have considered purchasing one of the store brought Geiger counters, retailing for at least $400, which can communicate exact amounts of radiation, in calibrated units, present within a given area either by means of an analog or digital readout. 
     The sensing device used in radiation detectors is something called a Geiger muller tube. Recently, the manufactures of the Geiger muller tube developed a version that is small and economically priced at $58. 
     Numerous innovations for radiation detectors have been provided in the prior art that will be described. Even though these innovations may be suitable for the specific individual purposes to which they address, however, they differ from the present invention. 
     A FIRST EXAMPLE, U.S. Pat. No. 4,197,461 to Umbarger et al. teaches a miniaturized radiation chirper for use with a small battery supplying on the order of 5 volts. A poor quality CdTe crystal which is not necessarily suitable for high resolution gamma ray spectroscopy is incorporated with appropriate electronics so that the chirper emits an audible noise at a rate that is proportional to radiation exposure level. The chirper is intended to serve as a personnel radiation warning device that utilizes new and novel electronics with a novel detector, a CdTe crystal. The resultant device is much smaller and has much longer battery life than existing chirpers. 
     A SECOND EXAMPLE, U.S. Pat. No. 4,229,733 to Tulenko et al., teaches an exposure detecting device comprising a radiation detector means providing an output signal responsive to the intensity of received ultraviolet radiation, a storage means receiving the output signal of said detector means and providing an output signal which increases as a function of the signal received and its duration, and decreases in the absence of a received signal as a predetermined function of time. A sensitivity control means provides a reference signal, and comparing means receives the output signal of said storage means and the reference signal of said sensitivity control means and delivers an output signal when the storage means output signal exceeds a predetermined value with respect to the reference signal. Alarm means is activated upon receiving an output signal from said comparing means providing an alarm. 
     A THIRD EXAMPLE, U.S. Pat. No. 4,695,73 to Noda et al. teaches a local radiation exposure alarm having a radiation detector used in the course of operations in nuclear power plant, a radiotherapeutic center for treatment for cancer, etc., a preamplifier for transmitting with an excellent S/N ratio a detected output signal from said detector, and a measuring unit measuring an exposure and provided with an alarm operating when the exposure exceeds a set permissible dose, and in which these detector, preamplifier and measuring unit are connected together electrically. The detector unit is shaped in a ring to be set on a finger or a toe, has a semiconductor element highly sensitive to radiation such as gamma rays incorporated therein so as to be sufficiently protected from vibrations and moisture, and is connected to the preamplifier unit through a lead wire. The preamplifier unit is provided with a fitting easy to set on and remove from an arm or the like and is connected electrically to the measuring unit also through a lead wire, and the measuring unit has a display and the alarm. The preamplifier unit has a space for holding the detector therein, and the measuring unit has a space for holding the preamplifier with the detector. 
     A FOURTH EXAMPLE, U.S. Pat. No. 4,963,747 to Thacker teaches an ionizing radiation detector which is based on the principle of analog electric integration of radiation sensor currents in the sub-pico to nano ampere range between fixed voltage switching thresholds with automatic voltage reversal each time the appropriate threshold is reached. The thresholds are provided by a first NAND gate Schmitt trigger which is coupled with a second NAND gate Schmitt trigger operating in an alternate switching state from the first gate to turn either a visible or audible indicating device on and off in response to the gate switching rate which is indicative of the level of radiation being sensed. The detector can be configured as a small, personal radiation dosimeter which is simple to operate and responsive over a dynamic range of at least 0.01 to 1000 R/hr. 
     A FIFTH EXAMPLE, U.S. Pat. No. 5,045,700 to Crowson et al. teaches a visual display for indicating a level of ionizing radiation that is mounted on a portion of an item of headwear, such as safety goggles, at a position within the peripheral field of vision of a wearer. Such a display advises a wearer of a level of radiation, including warning levels, in real time without requiring activity on the part of the wearer. In one embodiment, an ionizing radiation detector, accompanying circuitry, and the visual display are mounted on the glasses, such as on the frame. In another embodiment, a commercially-available detector is used to provide an output from a location remote from the headwear to actuate the visual display on the headwear. Various circuit embodiments are also disclosed. 
     A SIXTH EXAMPLE, U.S. Pat. No. Des. 325,171 to Laffaille teaches the ornamental design for a personal dosimeter badge. 
     It is apparent that numerous innovations for radiation detectors have been provided in the prior art that are adapted to be used. Furthermore, even though these innovations may be suitable for the specific individual purposes to which they address, however, they would not be suitable for the purposes of the present invention as heretofore described. 
     SUMMARY OF THE INVENTION 
     The present invention is an electronic blood hound that sniffs out radiation in and around one&#39;s home. 
     If one lives in an area in which nuclear accident is likely to occur, perhaps in close proximity to Three Mile Island, and is concerned that radiation could contaminate life essentials, such as water, food, and air supply, the present invention can restore some degree of security to one&#39;s existence by alerting one to contamination. 
     The present invention will sniff out the source of contamination and bark its warning to indicate the presence of radiation. Needless to say such a device, under some circumstances, can mean the difference between life and death. 
     If, however, like the average citizen one is more concerned with knowing where the contamination is then one is with knowing how much, then the present invention can certainly handle that task. 
     If a nuclear emergency does occur, one can feel secure in knowing that one is prepared to deal with it in one&#39;s own small way with the radiation detector of the present invention. 
     ACCORDINGLY, AN OBJECT of the present invention is to provide a radiation detector utilizing an unregulated power supply that avoids the disadvantages of the prior art. 
     ANOTHER OBJECT of the present invention is to provide a radiation detector utilizing an unregulated power supply that is simple and inexpensive to manufacture. 
     STILL ANOTHER OBJECT of the present invention is to provide a radiation detector utilizing an unregulated power supply that is simple to use. 
     BRIEFLY STATED, STILL YET ANOTHER OBJECT of the present invention is to provide a radiation detector that utilizes an unregulated power supply as opposed to a regulated power supply, since quantitative results are not required, only an audible signal, and an unregulated power supply is less expensive than that of a regulated power supply. The radiation detector includes a Geiger-muller tube, a nine volt DC power supply, a solid state oscillator with an output of 2 kilohertz, a high voltage power supply, and an audio amplifier. 
    
    
     The novel features which are considered characteristic of the present invention are set forth in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of the specific embodiments when read and understood in connection with the accompanying drawing. 
     BRIEF DESCRIPTION OF THE DRAWING 
     The figures of the drawing are briefly described as follows: 
     FIG. 1 is a schematic diagram of the circuit of the present invention; 
     FIG. 2 is a simplified schematic diagram of the circuit of the present invention shown in FIG. 1 with the power supply of FIG. 1 being shown simplified; and 
     FIG. 3 is schematic diagram to connect an optional Jack that will automatically connect and disconnect the speaker whenever a plug is inserted. 
    
    
     LIST OF REFERENCE NUMERALS UTILIZED IN THE DRAWING 
       10  radiation detector utilizing an unregulated power supply of present invention 
     C 4  first capacitor—0.005 μF,  1000  WVDC ceramic disc 
     C 5  second capacitor—50 pf, 1000 WVDC ceramic disc 
     D 1  first diode—IN4007 1-A, 1000 PIV 
     D 2  second diode—IN4007 1-A, 1000 PIV 
     G-M Geiger-muller tube 
     J Jack 
     J 1  power Jack—RS 276-1567 
     LD 1  light emitting diode—Jumbo red 
     Q 1  power transistor—2N3055—RS 276-2041 
     R 1  trimmer potentiometer—½ watt, 5% unit, 1000 ohm, 15 turn 
     R 4  second resistor—470,000 ohm, ½ watt, 5% unit 
     R 5  first resistor—4,700,000 ohm (4.7 mega ohms), ½ watt, 5% unit 
     S 1  power switch—single pole, single throw subminiature toggle 
     switch—RS 275-662 
     SPKR 1  loud speaker—8 ohm 500 mW loudspeaker—RS 400-245 
     T 1  step-up transformer—117 volt AC primary to 24-volt AC, 450 mA center tapped secondary—RS-273-1366 
     U 1  audio amplifier—LM 386  integrated circuit—RS 276-1731 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIGS. 1-3, in which like numerals indicate like parts, the radiation detector utilizing an unregulated power supply of the present invention is shown generally at  10 . 
     The radiation detector utilizing an unregulated power supply  10  comprises a Geiger-muller tube, a nine volt DC power supply, a solid state oscillator with an output of 2 kilohertz, a high voltage power supply, and an audio amplifier. The power supply can be as simple as six batteries connected in series for portability and stationary use or can be a wall mounted power pack. 
     A Transistor Q 1 , which is configured as a variation of a Hartley oscillator, generates a low voltage AC signal. The low voltage AC signal is fed across a primary of a step-up transformer T 1 , creating a rising and collapsing field which is in turn inductively transferred to a secondary of the transformer T 1  as high-voltage AC. The voltage at the secondary of transformer T 1  is fed through a first diode D 1  and a second diode D 2 . The first diode D 1  and the second diode D 2  form a voltage doubler/full-wave rectifier to provide an extra boost to the output voltage. The magnified/rectified voltage is then filtered by a first capacitor C 4  into 500 volts DC, which is then fed to a Geiger-muller tube G-M that has a window. 
     Inside the tube G-M is a gas that ionizes, i.e. conducts, whenever a pulse of radiation enters the window of the tube G-M. Each pulse causes a brief voltage drop across a 4,700,000 ohm first resistor R 5 . A second capacitor C 5  passes that pulse into an audio amplifier U 1  which in turn sends its amplified output to a loud speaker SPKR 1 , where-its converted into a pulse of sound. 
     The 500 volts DC on the tube G-M is not regulated. It will drop slightly whenever the tube G-M is busy, but that wont have a noticeable effect on the sound one hears. The transistor Q 1  is capable of dissipating up to 115 watts of power and hums along at ten percent of that maximum and doesn&#39;t need a heat sink. A trimmer potentiometer R 1  in Q 1 &#39;s base circuit varies the oscillator&#39;s frequency just enough so that one can get 500 volts DC for the tube G-M at the point where a second resister R 4  and the second capacitor C 5  join. 
     The transformer T 1  must be a center tapped 24-volt unit capable of handling at least 450 milliamps of current. A different one may not work at all, or worse, it could put out too much voltage and burn up the G-M tube. 
     The audio amplifier U 1  is a LH 386 , which is an 8-pin chip that saves lots of assembly time and is capable of driving 400 milliwatte of audio power into a 500 milliwatt 8-ohm loudspeaker. 
     Included in the circuit is a bass-boost which is used to emphasize the low-frequency pulses and to de-emphasize the high-frequency components of the 2-kHz oscillator that might otherwise leak through to the audio amplifier. 
     The loud speaker SPKR 1  can be any 500-mW unit that should be protected from damage by covering it with a wire screen or perhaps a grille. 
     A pair of low impedance earphones from a portable FM-radio headset can be used as a substitute for the loud speaker SPKR 1 . No one else, however, will be able to hear the radiation pulses except the wearer of the headphones, so one may want to use a normal through jack J, also called a closed-circuit Jack by hobbyists. When an earphone plug is inserted into the Jack J, the audio signal is rerouted to the earphones, and when removed, the signal is once again fed to the loud speaker SPKR 1 . 
     FIG. 3 illustrates how to connect such a Jack J. As shown, the loud speaker SPKR 1  is connected to the circuit. But when the plug is inserted into the Jack J, the loud speaker SPKR 1  is disconnected and the audio signal is re-routed through the earphones. 
     The radiation detector utilizing an unregulated power supply  10  can be built using a construction method of preference—printed circuit, perfboard with point-to-point wiring, or pre-etched experimenter board- and. components laid out in an arrangement most convenient to the builder. 
     Start by placing the IC socket and other components on the board and securing them in place by temporally bending the leads. Use short lengths of insulated wire to make the Interconnection between components, beginning with the passive components connected to the IC socket. Note that the light emitting diode LED 1 , the SPKR 1 , the power switch S 1 , and the power Jack J 1  are mounted on the front panel of the housing. Accordingly, those parts are put aside until the board components have been installed and the work checked for correctness. 
     After completion of the board, the board is put to the side and work on the panel mounted components is begun. First, drill and cut appropriate size holes in the panel to accommodate the parts. For the speaker hole, depending on what the cabinet is made of, metal, plastic, etc. one may be able to use a hole cutter, like those used by locksmiths. 
     After cutting the holes, mount components. Be careful when soldering to the light emitting diode LED 1 . While it can withstand quite a bit of heat for a semiconductor, it is nonetheless, thermal sensitive. Once that&#39;s complete, the next thing is the housing for the tube G-M. 
     An old microphone case has plenty of room inside, once the on-off switch is removed. Radio Shack sells a microphone for $7. Remove the dynamic mike element and the on/off switch, and very carefully place the tube G-H behind the front grill. 
     The tube G-M itself is small, measuring only 0.59 inches in diameter and 2.12 inches in length. Pack some plastic foam into the space behind it so that nothing rattles around, after you&#39;ve soldered the cable&#39;s center conductor and shield to the tube G-M. For added protection, surround the tube G-M in silicone within the microphone housing. 
     When assemblage of all the parts on the perforated board is complete, make connections from the board to the panel-mounted components, and make absolutely sure that there are no shorts or opens in the 9-volt power supply circuit. 
     You&#39;ll need to obtain a harmless source of radiation for test purposes. Every good radiation detector carries one for quick tests. 
     Obtain an alarm clock face with luminous paint on it. The luminous paint is a radioactive compound of radium. Tie a 12-inch length of string or nylon cord to the dial face, and anchor it to the carrying handle on your chassis box. 
     Before the cabinet is closed, hook up the internal 9-volt DC source. AdJust the trimmer potentiometer R 1  until 500 volts DC is measured at the Junction of the second resister R 4 , the first resistor R 5 , and the second capacitor C 5 . Do not allow the voltage fed to the tube G-H to remain higher than 550 volts for very long. Such will shorten its life. The voltage fed to the tube G-M must fall within the range of 490 and 550 volts. The tube G-M won&#39;t work at any voltage higher than the recommended 550 volts. 
     After the tube G-H feed has been set at 500 volts, remove the batteries and plug in the 9-volts, remove the batteries and plug in the 9 volt adaptor for external DC power. Make sure that the positive and negative polarity is wired in correctly. The adaptor will put out a slightly higher voltage than the batteries do, so the 500 volt setting now reads 530 volts. Set the audio volume control for 90% of maximum and close up the cabinet for the final check out of the radiation detector  10 . 
     To operate the radiation detector  10  turn it on and give it 10 seconds to charge up. Place the clock&#39;s dial face about one inch away from the window of the tube G-M tube. A good volume of sound should come from the loudspeaker SPKR 1  if the cabinet is closed up. 
     To get a working idea about the effective range of radiation, collect a few insulators, such as a sheet of paper, a piece of lead plate, a piece of aluminum, all three should be Just big enough to cover the dial face, and make a laboratory type test. Keep the dial face always separated from the tube G-M face by one inch space. 
     A radiation count of about 5000 counts per minute should be heard. Now place the paper insulator between the two and notice the slightly reduced radiation count. Replace the paper insulator with the piece of lead plate. Notice how much more reduction is made by the lead plate than was made by the paper. Then replace the lead plate with the aluminum plate. Notice that the aluminum is not as good as insulator as lead, but it is much better than the paper as an insulator. Naturally, the thicker the metal plate the greater its insulating quality. 
     While still testing, notice that the Inverse Square Law is at work. That means, doubling the distance between the tube G-M and the source of radiation re the radiation count by 75% not 50%. So the best insulator that can had between you and the contamination is plenty of distance. 
     It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above. 
     While the invention has been illustrated and described as embodied in a radiation detector utilizing an unregulated power amply, however, it is not limited to the details shown, since it will be understood that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and its operation can be made by those skilled in the art without departing in any way from the spirit of the present invention. 
     Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute characteristics of the generic or specific aspects of this invention.