Picture of Build a Pocket Ionizing Radiation Detector (PIRD)
2012-05-28 13.22.52.jpg
2012-05-28 13.23.05.jpg
Visit my youtube page for cool projects and more:

In this instructable I will be demonstrating how to build a pocket radiation detector or "PIRD." The parts for this radiation detector will all be salvaged (that means no pricey GM tube off of ebay), but building will require steady hands and alot of patience! This is a "clicking" radiation detector, unlike many other DIY versions without a Gieger-Muller tube out there, and I have yet to see anyone try this concept and/or make one like it. Although it may not be as sensitive or practical as a standard geiger counter, it does detect background radiation (most likely gamma rays). Similar concepts are seen on the CERN website, demonstrating the potential to detect both alpha rays and background radiation: ( and on youtube (

Here is a video testing it using a small amount of radioactive Americium found in a smoke detector:
Remove these adsRemove these ads by Signing Up

Step 1: How it Works

Picture of How it Works
This geiger counter works on similar principles that any other ordinary geiger counter works on. Essentially there is a small gap between two wires - a high dc voltage is applied to both wires, and when an ionizing particle moves between the wires, an ion channel is created and electrons arc across the wires, creating an audible "click" on a radio. Normally, the gap is inside of what is called a "geiger muller tube," where gases ideal for ionization are held for increased sensitivity. With this geiger counter, the absence of gases ideal to ionization is made up for by placing the wires in closer proximity to one another (so close that to the human eye they appear to be touching). The process of slowly moving the wires closer to one another is called "spark gap quenching".
1-40 of 47Next »
grospietro2 months ago

Molto interessante, bisogna provarlo!

ashtianiphys4 months ago

where did you conect the radio?

rfox49 months ago
How difficult would this be to modify for use with a Geiger Muller tube?
florinc rfox47 months ago

Add in a variable resistor in the positive side of the output circuit, and then connect a GM tube to the rest of the output circuit and adjust the resistor.

mammasboy2 years ago
Does the PIRD have much range? in the video the Americium was right next to it, at kind of ranges can it detect radioactive materiel's?
It depends in the type of radiation, Americium-241 produces almost all alpha particles , which are like positive helium ions (going quite fast) so only goes about a cm in air.
beta radiation on the other hand is a electron(or in some rare cases a positron) so can go up to 15cm , sources include potassium-40 (in bananas) and tritium(hydrogen-3 in the SUSAT)
The last type of radiation is gamma rays which is literally light but at a very high frequency so can travel through materials easily , (similar to xrays but higher energy so goes through bone)
all are very dangerous but if you haven't got any protection try to stick to alpha because unless ingested its pretty safe
squishyjoss12 months ago
Its great :)
interesting one
redox6021 year ago
How should a potentiometer be soldered into the circuit in order to adjust the voltage output? With one AA battery, I'm getting 360V, and with two AA batteries, I'm getting 650V. I'd like to be right around 400.
chocokitti1 year ago
The tips of the brass screws I used seem to corrode very quickly. It sparks frequently at first but tapers off and after several seconds it does not work at all. Anyone know what I'm doing wrong?
There is the possibility that when the screws corrode, it creates some kind of residue or something that acts as an insulator, you might want to check that out.
sciman12 years ago
why not make a simple wooden bracket to hold two small machine thread srews.
kinda like a ~||_||~ u shaped bracket with the screws from either side.
then you could pretty simply just twist in one of the bolts till it "auto quenched"
sand the tips of the srews to remove any burrs... DONE.
Maters2 years ago
Nice instructable but the name is funny for me cuz PIRD in my language means - to fart.
jiovine2 years ago
Hi, I like your project. However I am not convinced you're detecting gamma radiation. If you like to verify the function of your detector, it's a pretty straight forward test. Bring a radioactive source close to your detector. If it is detecting radioactivity you ought to see and hear an uptick in the number of radioactive particles detected when the source is close by.
TheHomebrewGuru (author)  jiovine2 years ago
I don't have any radioactive samples, I'll try to get my hands on some Americium. But judging by the fact that I only hear the clicks once or twice every couple on minutes, it's a safe bet. Also, a similar idea was published on the CERN website as an educational experiment for use in detecting gamma radiation
Go to a hospital and see if you can pick some up from X-ray those cancer treatment rooms.
Spark detectors can detect alpha particles but not beta, gamma or x-rays. If you look at this youtube video you can see a video of a alpha particle spark detector I built a while ago.

TheHomebrewGuru (author)  jiovine2 years ago
Video added
TheHomebrewGuru (author)  jiovine2 years ago
The spark gap quenching could be accomplished easily using an insulating bracket and two finely threaded screws facing each other (tip to tip). Such a configuration would also lend itself more easily to recalibration.
I was thinking something like wires held in by screws to calibrate, but this sounds much easier!
kelseymh2 years ago
That is a really awesome I'ble! I wish I had seen it before Randy, so I could get the glory of Featuring it :-)

I had a bit of trouble following the pictures and descriptions -- you might consider using the "image notes" to identify exactly where in each picture we should focus.

One comment about your "ambient air" G-M counter. You note that when properly aligned, the counter should discharge every minute or two. That's consistent with sea-level cosmic ray rates in the Northern Hemisphere. I wonder if you could get a more quantitative calibration using an Am-241 source scavenged from a smoke detector?

TheHomebrewGuru (author)  kelseymh2 years ago
Video added
Nicely done. And a good demonstration that your device really does work to detect ionizing radiation. Thanks!
TheHomebrewGuru (author)  kelseymh2 years ago
I'll try to get my hands on some soon
florinc2 years ago
Have you tested it using some radioactive material (lie tungsten rods or mantle)?
TheHomebrewGuru (author)  florinc2 years ago
Video added
TheHomebrewGuru (author)  florinc2 years ago
I don't have any radioactive substances to test it out, but something similar was posted on the CERN website as an educational tool:
emcelhannon2 years ago
I want to see yours tested on a smoke detector.
TheHomebrewGuru (author)  emcelhannon2 years ago
I'm going to ask a friend if I can have his old ones
Video added
ricks2 years ago
We built this but only see about 200 volts or so when connected to a 3v button cell pack. While we hold the button cell to the leads, the HV output continuously drops.

On an earlier build we thought if 3V gets us 200, then 8v might get use 500 or so, but it seemed to "kill" the unit. Back to the store for a new camera.

Any ideas on what we are doing wrong. We are nowhere close to the 400-600 volts needed to allow the ionization.

TheHomebrewGuru (author)  ricks2 years ago
I got 400-600v easy. And do not buy cameras, ask for free used disposable cameras from stores that develop photos. I got hundreds (not to mention free AA batteries). Try a different model camera or make sure that your batteries have enough juice
atrumblood2 years ago
Hmm this looks like a fun project. In the field I work in we deal with compact radiation sources that I could test this on. Something a little more "hot" than an old smoke detector.
techno guy2 years ago
that's pretty cool, i didn't think it would be possible by just putting the contacts close together, but apparently i was wrong
Caspar2 years ago
ps. Am-241 might not have penetrating radiation and may be poisonous. Check the MSDS.
TheHomebrewGuru (author)  Caspar2 years ago
Opening a slit in the tin might allow the radiation to hit the spark gap
Caspar2 years ago
There are various disposable camera HV supplies, one type uses a neon tube. With a bit of modification, the neon tube (which indicates when the capacitor is fully charged) can be the spark gap. The glass envelope around it makes it rather insensitive, though humidity and vibration effects are eliminated. The neon will strike at around 80-100 V, and some sort of voltage stabilization will improve its performance. Or you could just buy a neon tube, at around 15 to 50 cents.

TheHomebrewGuru (author)  Caspar2 years ago
I would like to see someone try this, though getting the correct voltage might be a pain. It would eliminate the need for any DIY-er to buy a GM tube off of ebay which would be a first (never been done before). I thought this originally but getting the correct voltage would be difficult. Using multiple neon tubes might increase sensitivity
1-40 of 47Next »