The mantle in some Coleman lanterns are radioactive. Bring your Geiger counter to a local hardware store and check them out.
Uranium ore should also emit sufficient radiation to trigger the counter. It is available from a number of sources including our online store.
A more reliable source is to purchase a radioactive source. Small amounts of radioactive materials are available for sale encased in 1 inch diameter by ¼" thick plastic disks. The disks are available to the general public license exempt. This material outputs radiation in the micro-curie range and has been deemed by the Federal government as safe.
The cesium-137 is a good gamma ray source. The cesium 137 has a half-life of 30 years.
Turn on the Geiger counter. If you have a radiation source bring the GM tube close to it. The radiation will cause the Geiger counter to start clicking. The LED will pulse with each click. Each click represents the detection of one of the radioactive rays; alpha, beat or gamma.
Background radiation, from natural sources on earth and cosmic rays will cause the Geiger counter to click. In my corner of the world I have a background radiation that triggers the counter 12-20 times a minute.
Separating & Detecting Beta and Gamma
By placing shields of different materials in front of the GM tube we can filter out some radiation. For instance placing a paper shield in front of the GM tube will block all the Alpha radiation. The Geiger counter will now only detect beta and gamma radiations.
If we place a thin metal shield in front of the GM tube that would effective block the alpha and beta radiation, allowing the detection of gamma radiation.
The complete parts list including case and GMT-02 is available as the GCA-01 kit for $84.95.(1) PCB-66
(1) 1K 1/4W Resistor - R1
(8) 10K 1/4W Resistors - R2, R4, R5, R6, R7, R8, R12, R19
(1)15K 1/4W Resistor - R9
(2) 1 Mega Ohm 1/4W Resistor - R3, R11
(1) 100K 1/4W Resistor - R13
(2) 330 Ohm 1/4W Resistors - R15, R21
(1) 10 Mega Ohm 1/4W Resistor - R16
(1) 5.6K 1/4W Resistor - R17
(1) 4.3K 1/4W Resistor - R18
(1) 470 Ohm 1/4W Resistor - R20
(2) 1 Meg 25-Turn Potentiometers - R10, R14
(3) 0.1uF 50V Capacitors - C1, C2, C10
(3) 0.01uf 1KV Capacitors - C3, C4, C5
(1) 220uF 10V Capacitor - C6
(1) 22uF 50V Capacitor - C7
(2) 0.01uf 12V Capacitors - C8, C12
(1) 0.0047uf 100V Capacitor - C9
(1) 0.047uF Capacitor - C11
(1) 1N751 5.1V Zener Diode - D2
(1) Red Subminiature LED - D3
(2) 1N4007 Diodes - D4, D5
(1) 1N5271 Diode - D6
(2) 1N5281 Diodes - D7, D8
(1) 1N5817 Diode - D9
(1) 1N914/1N514 Diode - D10
(1) LM339 - U1
(1) W01M - Bridge Rectifier - U2
(1) 7805 Voltage Regulator - U3
(1) 4049 - U4
(1) LM555 Timer - U5
(3)2N3904 Transistors - Q1, Q3, Q4
(1) IRF830 - Q2
(1) Plastic Case
Components that are sold separately (click for more info or to purchase):
Radioactive Sources (click for more info or to purchase):