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Home > Articles > Geiger Counter Enhancements & Options, Page 1
Geiger Counter Enhancements & Options
In the following sections you will find enhancements and options for the basic Geiger counter.
Revised Schematic
We have a revised schematic shown in Figure 1. The basic Geiger counter circuit is identical to the previous circuit.
The revision is the adding of the components for our three optional
enhancements; external power input, headphone jack and digital output,
boxed in red.
Figure 1. Revised schematic showing the enhancements in red boxes.
External
Power – The external power is designed to allow a wide range of wall
transformer to power the Geiger counter. Wall transformers that can
supply a minimum of 75 mA with voltages that range from 7-12VAC or
7-12VDC will work. The bridge rectifier is rated at 25V 1 amp. Pretty
much any bridge rectifier with specifications around these
specifications (or better) will work when placed inside the circuit.
The positive output lead of the bridge rectifier is placed after the D9
diode. The D9 diode protects the battery when using external power.
Headphone
Jack – Aside of its obvious use for a headphone, this jack may also be
used as a temporary output for an Analog Meter. The headphone jack is a
3.5mm 2-conductor jack with a SPST switch. The switch automatically
disconnects the speaker when the headphone or analog meter is plugged
in.
Digital Output – The digital output jack
provides a +5V TTL logic pulse every time a radioactive particle is
detected. The digital output uses an unused gate off the 4049 as shown
in the schematic. We will build a small interface between this output
and a Windows PC. This will allow you to use one of the free Geiger
counter graphing programs.
For those who
have purchased the PC board for this project, the enhancements may be
added by wiring in the three jacks as shown in Figure 2.
Figure 2 Connecting the three 3.5MM jacks to PC board.
Geiger Counter Enhancements & Options pg2 "Analog Meter"
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