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Home > Articles >Build Your Own Geiger Counter, Page 6
Continuing Construction
Finish the construction of the circuit by adding the 555 timer,
capacitor C6, resistors and transistor. Mount and solder resistors R4
(10 mega-ohm bands brown black blue), R5 (470K bands yellow violet
yellow), R6 (100K bands brown black yellow) and R7 (47K bands yellow
violet orange ).
Attaching GM Tube
The
Geiger Muller tube has two leads. The lead connected to the metal sides
of the tube is the ground. This is soldered to the (-) GM terminal on
the PC board, see Figure 7. The center terminal of
the GM tube has a removable solder lead. Remove the lead, solder 1.5”
of wire to and. Reattach the lead to the center terminal of the GM
tube. Take the opposite end of the wire and solder to the (+) GM
terminal on the PC board.
The Geiger Mueller
tube is delicate and should be protected in an enclosure. You should
face the GM tube toward a 1/2” hole in the enclosure that allows the
front surface (mica window) of the GM tube to remain exposed. This way
alpha particles can pass through the thin mica window and be detected.
We
mount the GM tube to the PC board using scrap of wire. The GM tube is
positioned above the GM Tube silkscreen outline on the Printed Circuit
board. One end of the wire is solder into one of the side holes. The
wire is looped over the GM tube and soldered into the second hole on
the opposite side. Keep the wire snug when soldering the wire into the
second hole.
After securing with a wire a small amount of glue or epoxy can be dabbed on the wire tube assembly for added support.
Figure 7. Detail showing GM tube secured on PCB
Build Your Own Geiger Counter pg 7 "Radioactive Sources"
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