GEIGER_COUNTER_TO_IBM_INTERFACE

Published:2009/7/14 2:01:00 Author:May | From:SeekIC

The simplest way to connect a Geiger counter to the IBM computer is to use a headphone jack to the parallel port. The headphone jack provides a +5- to 0-V pulse for each radioactive particle detected. The signal from the Geiger counter is +5 V. When radiation is detected, the signal pulses down to 0 V for a few milliseconds before returning to +5 V. Even though the signal is in the 0- to +5-V range, it is not safe to connect wires from an external circuit or instrument directly to the parallel-port lines without buffering. The op amp operates from a single-pole +5-V power supply. In this particular case, invert the signal from the Geiger counter. Because the pulse signals are +5 to 0 V, we do not require any amplification from our op amp. Therefore, the op arnp is configured as an inverting unity-gain follower. Remember that the Geiger counter outputs a steady +5V through the headphone jack. When it detects radiation, the output pulses down to 0 V for a few milliseconds. By inverting the Geiger counter signal with the op amp, the computer reads a steady 0 V on its line and a +5-V pulse when radiation is detected.



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