Improved Clicker - and an Oddity...

The original single transistor driving the indicator LED and sounder was poor. I have improved this by using the first transistor to drive a second, which then switches the LED and sounder. I have also replaced the small sounder with a 1.5" cone 8Ω loudspeaker. The result is a much louder click and a nice bright flash from the LED, to indicate a detected particle/quanta.

I did attempt to use a trick I've seen on others builds of similar architecture, that is, using an extra diode and capacitor to obtain an extra supply from the HV circuits, higher than the supply but low enough for safe use for the indicator circuits. This gave me around 6V, but the current went through the roof (35mA) and it was clear that the drive oscillator was not cutting back as it should. For the moment I have abandoned this approach. The 3V circuit I'm using seems quite adequate.

But there is an oddity... the LED is always very dimly lit, and on close observation, can be seen to be flickering. Now, if I touch ANY part of the low voltage side of the system - the LED goes out, except when pulsed by the transistor switch. And I do mean anywhere! I can put a finger on the +Ve supply connection, or the ground, or the battery itself! However, if I touch the potential divider input to the 1st indicator transistor (i.e. the G-M tube cathode connection), the LED lights with a very bright fast flicker!

It seems quite obvious that the cause of this is leakage of the HV generators oscillator. I suspect that some bypass capacitors will be required to tame this.

In this configuration on the breadboard, the circuit draws just 1.63mA from the 3V supply. This is with the regulator transistor controlling the oscillator transistors collector. I might be able to get it lower, and improve the regulation, by controlling the base, but that's an experiment for later, as is lengthening the output pulses to a fixed pulse length for an external counter interface.