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TOPIC: Don't power your geiger tube using usb with a laptop that has a GENERIC power adapter.

Don't power your geiger tube using usb with a laptop that has a GENERIC power adapter. 3 years 1 month ago #524

  • Tine
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First of all don't power your tube with a laptop that uses a generic power adapter.

That was the source of my erratic and high counts for my tube.
I was powering the tube using the 5v usb on the laptop, and the adapter was fluctuating its supply enough that the geiger tube didn't like it.
It was not obvious at first, but when I used a power adapter that has a usb port on it, the high readings and fluctuations went away.

The generic laptop supplies are made so they can work with a wide range of laptops, but sacrifice voltage stability.

Oh, perhaps i should have put this in a different section...
The universe is a living enigma, and you, are its child.

Despite the enigma of the singularity, the big bang theory is unquestionably one of the most successful ideas in the history of science. —Tom Yulsman, Astronomy, September 1999
Last Edit: 3 years 1 month ago by Tine.
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Don't power your geiger tube using usb with a laptop that has a GENERIC power adapter. 3 years 1 month ago #525

  • mw0uzo
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Welcome back Tine! :)

Yeah I've had that problem using the MyGeiger with the RPi and a phone SMPSU. The - on the secondary side is not way actually connected to earth so can float about. This can cause unintended 'detections'. I found the counter was only stable if I connected the coax screen and tube to earth. t think the problem was using coax for the connection between the counter and tube. I think the be st way is screened double core cable, with the tube connections on the internal wires and gnd on the screen. The only SMPSU with earthed negative I could find was sold out and unavailable, so that put the RPi setup out of action.

I only had the problem if the coax was used and the SMPSU was used. Removing the coax, using a linear supply or using the SMPSU with the - connected to earth solved the problem. In my case the extra counts were frequent so it was immediately noticable.
Last Edit: 3 years 1 month ago by mw0uzo.
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