SI-3BG geiger tube IS NOT PIECE OF JUNK

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Science & Technology

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• MOV06853

[tesla242]

The SI-3G and the SI-1G are nice small tubes to carry in an every day pocket geiger counter, just to carry it every where. They are pretty insensitive so, if you hear a slight increase in the click rate, you can be sure the object (or the place), it´s above normally radioactive.

Im bulding one probably with a SI-1G these days.

[fuuturist]

@tesla242 I'm trying to make a small GM counter that draws only 0.3-0.5mA, and when count rate increases alarm will start screaming!

[tesla242]

thats a very low current but It´s posible, try the circuit in techlib, with a little tunning I think they can reach that value. And use as many mosfets as you can (instead of bipolar transistors) , and CMOS gates, their power consumition during a steady state it´s "almost" cero. a CD4093 I think it could be used as an oscillator and level detector.

[fuuturist]

@tesla242 Yes, I will use Carl Wenzel's shematics. This is also his oscillator, but power consumption is too high - about 1.5mA

[tesla242]

@fuuturist I just found this: eetimes.com/design/power-manag­­ement-design/4009593/Bias-sup­p­ly-powers-low-power-Geiger-M­ue­ller-tube

The desing claims a quiescent current of 80uA, quite impressive. Too complicated for my, but could be usefull to you if you want to cut down on power.

Sorry with the repeated messages, I have troubles pasting the link

[fuuturist]

@tesla242 wow -_- I'm amazed! I will try this! Thanks!

[tesla242]

@fuuturist Try working with the electrolytic cap. I use that circuits without regulation. I found out, that the voltage doubler it´s not generally necessary, 1 diode and 1 cap it´s enough to get 400v using an isolation transformer from a modem.

Another low power solution it´s to use a variable duty cycle oscillator and a large inductor. Then tune de values of frequency and duty to get the minimum working voltage for the tubes.