PhysicsOpenLab Modern DIY Physics Laboratory for Science Enthusiasts
The latest “born” at Micod is a driver for Geiger-Muller tubes. It is a circuit (shown in the image above) which has the function of providing the high voltage (400 or 500 V) necessary to drive a Geiger tube. The driver is characterized by numerous features :
- Supply voltage between 1.5V and 5V. It can therefore be powered by normal 1.5V batteries
- Ultra-low power
- High Voltage selectable between the values of 400V and 500V
- Pulse forming circuit to produce pulses of 5V and lasting 10μsec
- Supply of a service voltage of 5V
- Geiger Resistor Load of 10MΩ
- Possibility of having a snubber circuit
- Terminal block with screw terminals separate from the high voltage connector
The image below shows the rendering of the circuit, note the HV connector for the geiger tube on the right and the main terminal block on the left. The selection between 400V and 500V is obtained on the indicated connector : open 400V, closed 500V.
The driver was immediately tested with the classic SBM-20 geiger tube, for which a voltage of 400V and a load resistance of 10MΩ are fine. The image below shows the connections from the driver board to the Geiger tube. Of course the connections must be made respecting the correct polarity of the voltage.
The circuit supplies a very low current but it is still recommended to be careful with high voltage.
The image below shows the connection of the driver with a small 3.6V rechargeable lithium battery.
The driver is equipped with a pulse forming circuit that outputs a clean pulse of 5V amplitude and 10μsec duration, as shown in the trace acquired with an oscilloscope presented below
the 5V-10μsec impulse can be easily detected and “counted” with any type of micro-controller, like Arduino o Theremino.
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