As this project is a film prop, it dose not need to actually detect radiation nor will it need have any audio, as this will be dubbed in during editing. However, the unit must give the impression that it is operating and be able to be controlled both internally or remotely to indicate high and low levels of radiation during filming.
Fortunately, I had damaged 1960's British Army Geiger Counter which still had a meter inside which I extracted to form the basis of the Geiger Counter, (Any meter would do really) which not only added a certain realism, but also gave a familiar feel to old 50's nuclear scifi films which I personally love.
In the process I tried out a few different layouts and knobs, etc. before I got the right look.
Then I printed a Fascia label to give an impression that the knobs actually do something (which they do but not real Geiger Counter related).
But don't expect to see this unit looking so shiny in the film, as it will be most likely scuffed up and spray painted to give the impression it survived a strange apocalyptic disaster along with it's user.
The control circuitry is very basic and robust using an off-the-shelf flashing LED for the Power Indicator, this also provided a pulsating voltage source through a resistor network to modify the meters movements implying strange activity. 10K Linear Potentiometers are used to control the voltage to the meter from a small 6V battery pack and a 2 pole 4 position switch was used to switch between external or internal controls, and pulsating or smooth control.
I installed a small 3.5mm phono socket at the rear that allows for the attachment of a remote control so that the meter can be controlled off-camera in a similar way to the internal knob in the video below. Where the different selections between smooth and pulsating control of the meter will give the film makers the flexibility for different scenarios during the film.