Geiger counter hack: simply homemade, uses Soviet era Geiger counter (pancake) detector tube

By Dorian Stonehouse

With technical input from John David Stonehouse M.Sc.

THERE are many and varied types of Geiger counters on the market nowadays; and even the modest models will not leave you much change from a £1000 pounds ($1,300[approx]).

So, here are few ideas to whet your appetite and get you involved in building your own Geiger counter for a fraction of the cost.

Don’t forget however that the humble fly zapper gives out over 1000 volts, so if you are very young, see teacher first!

Comparing ionization inside the Geiger counter tube with a plop, plop droplet of water!

It may be useful to compare the water disturbance in the picture/s ⇑⇓, not only with the gamma waves travelling to our Geiger counter tube; but also with the effect the radiation has on the gas inside the tube.

A special event sending out ripples of energy

A radiological event sends a burst of energy into the Geiger counter tube

And it’s another bullseye hit!

The gas atoms in the detector tube are so violently disrupted by a nuclear event that many electrons are knocked out of their orbits, leaving the atoms with a net positive charge (ionized).

This enables tube current to flow from cathode to anode, producing the familiar “click.”

The Geiger counter detector tube: 

Are they nothing more than one-way (glorified) light switches?

Geiger counter hack: simply homemade, uses Soviet era Geiger counter

(pancake) detector tube

Yes, the Geiger detector tube is nothing more than a switch with a resistor in series with it.  In fact if the tube is removed and the two wires are repeatedly touched together, the same clicks will be heard through the loudspeaker.

Geiger counter block diagram:

bug zapper

With just a few components, a working Geiger counter can be made in next to no time. 

This simple design does not have a digital counter to tell the operator how many counts per minute are registered.  However, once the observer knows what the “normal” counts per minute are for a particular area.  Then it’s…

… as easy as riding a bike!

Geiger counter hack: simply homemade, uses Soviet era Geiger counter

(pancake) detector tube

All that is needed to make that Geiger counter detector tube glow in the dark is the finishing touch – a radioactive source. 

And to achieve that I am very fortunate to own a lovely old luminous clock:

the cherry on the cake

A shot in the dark

When the Geiger tube (especially in darkness) is held close to a radiation source, the gas within the tube lights up due to ionisation (does not show up very well on my camera!).

 A bit more of a challenge…

introducing the “Easy Read” Homemade Geiger counter

Geiger counter hack: simply homemade, uses Soviet era Geiger counter

(pancake) detector tube

Actually, the “Easy Read” uses two Geiger counter tubes:  one in the external probe and the other (backup unit) round the back of the box.

Many see it as mundane Thermos mug, but I see it as a beautiful thing!

Geiger counter hack: simply homemade, uses Soviet era Geiger counter

(pancake) detector tube

The circuit is very straightforward and consists of two 555 chips and a handful of components.

Q1 ⇑⇑was initially meant to drive a small modified analogue meter (“met”) in order to present an average radiation value in counts per minute. However, this idea was shelved due to insufficient room, and Q1 base was instead connected to the output of Ic2 in order to drive the mini timer relay.

Main board layout of the

“Easy Read”

Geiger counter

Geiger counter hack: simply homemade, uses Soviet era Geiger counter

(pancake) detector tube

Ic2 ⇑⇑is configured as a timer chip and is set to operate for one minute, routing the pulses from Ic1 to the digital panel counter.

Q2 drives Ic1, which effectively improves the audio component by extending the pulse coming from the Geiger detector tube.

Inside the box

To the left are two lithium ion batteries (Li-ion), with circuit protection diode and fuse. 

Straight ahead is the timer pcb etc, as described above.

The horizontal board is the Mini amplifier pcb; and on the right is the bug zapper board, which supplies high voltage to the selected Geiger detector tubes.

Inside the lid

Here we have the loudspeaker and digital counter.

The print side after a nice layer

of circuit lacquer is applied

Geiger counter hack: simply homemade, uses Soviet era Geiger counter

(pancake) detector tube

Geiger counter hack: simply homemade, uses Soviet era Geiger counter

(pancake) detector tube

Some more info about the SI-8B Geiger counter detector tube

I have used these tubes since my youth and, when it comes to making Geiger counter tubes, Russian technology is pretty hard to beat.

For example, how many pancake Geiger detector tubes can detect alpha radiation with such remarkable sensitivity as the SI-8B, without using a super light and highly damageable mylar film, costing loads of dosh (cash) !?

The newer type Geiger detector tube

Geiger counter hack: simply homemade, uses Soviet era Geiger counter

(pancake) detector tube

But they are not without an

Achillesheel

(The older type Geiger counter detector tube)

Most of the SI-8B Geiger detector tubes on the market are photosensitive – they give higher counts in sunshine than in the shade.

This might be okay if you are working in the woods in Transylvania, but not if you have to test a piece of land in broad daylight in Brynamman!

Like me, they also do not like high voltage surges when switched on!

Voltage surges can cause the SI-8B’s to give up the ghost in the field time after time, for (apparently) no reason; thus putting a heavy financial burden on your department.

Geiger counter hack: simply homemade, uses Soviet era Geiger counter

(pancake) detector tube

The answer to the above problems is twofold: first, ensure that the detector tube you have ordered is NOT photosensitive by asking the seller to confirm this. 

Usually the non-photosensitive tubes have a circle in the middle (compare the new type detector tube against the old one in the pictures ⇑⇑).

Second, always place a high value resistor in series with the detector tube. This will be a minimum value of 1 megohm and will reduce any surges, along with the number of counts per minute.

And please remember that upping the anode voltage and placing a radiation source near the tube to get maximum sparks jumping inside the detector tube is a big no-no!

 Highly recommended viewing:

http://www.nuclearconnect.org/about

 

https://www.youtube.com/user/bionerd23

 

 

Please may I ask all visitors to post links on their social media accounts directing visitors to electrosparkles.com so that more people can enjoy the website, and join in to present their technical ideas for featuring.

Heartfelt thanks

Dorian.

 

 

[whohit] Geiger counter hack: simply homemade, uses Soviet era
Geiger counter (pancake) detector tube [/whohit]