Introduction: Build a Pocket Ionizing Radiation Detector (PIRD)

Picture of Build a Pocket Ionizing Radiation Detector (PIRD)


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Here is a video testing it using a small amount of radioactive Americium found in a smoke detector:

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".

Step 2: Finding a Radio

Picture of Finding a Radio

Any radio will do, just as long as when you create a "spark" (touching a wire to a battery) you hear a "click" on the radio. I tested my radio on the oscilloscope in this video: 
As you can see, there are little valleys when I create sparks. This means that the radio is detecting the disturbances properly. The radios I used were a $1 mini radio and a larger more sensitive radio I salvaged from my grandfather.

Step 3: Making a High Voltage DC Power Supply

Picture of Making a High Voltage DC Power Supply

A high voltage DC power supply can be created from a disposable camera. First, take out the big black capacitor. Take out the smaller capacitor near it and place it where the bigger capacitor used to be. This will be used as a "filter capacitor." Take off all the unnecessary odds and ends (the xenon flash tube, the battery contacts, etc.) refer to the before and after photographs. I added a potentiometer to adjust the output voltage, but this is not necessary (that's the blue thing, don't worry about it). Make sure that if your camera had a "charge" button, solder the two contacts for the button together so that the unit is always in "charge" mode.

Be careful! The output from this unit will be around 400-600v! Test it out by touching two AA batteries to the + and - spots that were taken out, and the red LED should be on (or whatever other light is there).

Step 4: Spark Gap Quenching

Picture of Spark Gap Quenching
This part is a bit tricky. You now need to put the hv output wires from the camera unit so that they are almost touching, but not arcing continuously. This may take a while to do.

Once you do this correctly, there should be arcs every so often, but not continuously (maybe once every couple of minutes). This means that the unit is detecting ionizing radiation! To hear the "clicks," turn on the radio. 

I have attached a picture in which I have produced a spark gap between an alligator clip and a screwdriver, but any type of gap would work (between a wire and a plate, between two plates, between two wires, etc.). 

Here are some videos of proper operation (notice and listen carefully for the audible "clicks"):

Step 5: Boxing It Up

Picture of Boxing It Up

Now, all that needs to be done is to box it up and make it all look pretty. With a bit of patience and lots of tape, spark gap quenching is possible in the little box too!

I added a switch and added an LED popping out from the box to replace the LED in the camera HV DC board. After gutting the mini radio, everything fits in a little altoids tin (perfect for pocketing).

The wires may need to periodically be re-calibrated, and the unit needs to be held still for it to work (vibration can cause an arc). Don't blow on the spark gap!

I hope you enjoyed this instructable! Rate, comment, and vote!


SHOE0007 (author)2017-11-12

I find this quite cool. However If you want to play with radation please get a good beta, alpha and gamma meter like this. They allow accurate detection of Counts Per Minute and uS an Hr.

jiovine (author)2012-06-24

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)jiovine2012-06-24

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

Get yourself a chunk of granite, it is mildly radioactive and shows a noticeable increase on a Geiger counter compared to background radiation. I'm a school science technician and this is what I issue for students to handle, as the sealed radioactive sources can only be used for teacher demonstrations.

Unfortunately I'm about 4 years late with this comment... but felt the need to add this for reference!!

aayoung (author)TheHomebrewGuru2016-05-27

You can buy uranium on Amazon.

Go to a hospital and see if you can pick some up from X-ray those cancer treatment rooms.

DIY-Guy (author)magranger152014-12-28

My friends in the medical business tell me that nobody is allowed near rad sources, except the patient and the technician. It's a security issue. And rooms where those treatments occur will not be "leaking" outside the clearly marked areas. It would be a bad thing to detect radiation outside those limits.

But, if you do know how to get some low-risk samples to test this I would really like to hear about it. :) Good luck!

jiovine (author)TheHomebrewGuru2012-06-25

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)jiovine2012-08-06

Video added

TheHomebrewGuru (author)jiovine2012-06-24

redox602 (author)2013-06-09

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.

use a resistor to cut the differance

ashtianiphys (author)2014-06-08

where did you conect the radio?

to the batery where else

grospietro (author)2014-07-27

Molto interessante, bisogna provarlo!

rfox4 (author)2014-01-08

How difficult would this be to modify for use with a Geiger Muller tube?

imitt12 (author)rfox42014-01-10

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.

mammasboy (author)2012-10-23

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?

SMarshall14 (author)mammasboy2013-12-02

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

squishyjoss (author)2013-10-27

Its great :)

KatherineSchreiber (author)2013-09-06

interesting one

chocokitti (author)2012-10-27

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?

techno guy (author)chocokitti2013-05-11

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.

sciman1 (author)2012-10-23

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.

Maters (author)2012-10-23

Nice instructable but the name is funny for me cuz PIRD in my language means - to fart.

yellowdart31 (author)2012-09-25

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!

kelseymh (author)2012-06-23

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)kelseymh2012-08-06

Video added

kelseymh (author)TheHomebrewGuru2012-08-06

Nicely done. And a good demonstration that your device really does work to detect ionizing radiation. Thanks!

TheHomebrewGuru (author)kelseymh2012-06-24

I'll try to get my hands on some soon

florinc (author)2012-06-24

Have you tested it using some radioactive material (lie tungsten rods or mantle)?

TheHomebrewGuru (author)florinc2012-08-06

Video added

TheHomebrewGuru (author)florinc2012-06-24

I don't have any radioactive substances to test it out, but something similar was posted on the CERN website as an educational tool:

emcelhannon (author)2012-07-01

I want to see yours tested on a smoke detector.

I'm going to ask a friend if I can have his old ones

Video added

ricks (author)2012-07-04

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)ricks2012-07-07

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

atrumblood (author)2012-07-07

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 guy (author)2012-06-26

that's pretty cool, i didn't think it would be possible by just putting the contacts close together, but apparently i was wrong

Caspar (author)2012-06-25

ps. Am-241 might not have penetrating radiation and may be poisonous. Check the MSDS.

TheHomebrewGuru (author)Caspar2012-06-25

Opening a slit in the tin might allow the radiation to hit the spark gap

Caspar (author)2012-06-25

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)Caspar2012-06-25

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

spiceyweasel (author)2012-06-24

It says my breath is radioactive. :(

Vibrations can make it arc

AndyGadget (author)2012-06-24

Do you have to recalibrate depending on the weather?  I'm thinking that high humidity would cause arcing more easily, and therefore the electrodes would have to be further apart.

Thinking on from that, using a variable HV supply and the flash tube from the camera may make a more stable version as the gas is fully contained.  Commercial GM tubes use a variety of noble gases, of which the xenon in the tube is one.

I thought of using the flash tube initially, and it might work, but you would need a higher hv dc power supply I think

About This Instructable




Bio: IF YOU HAVE QUESTIONS CALL ME AT 8059157065 Hello I'm Mad Scientist Trevor Nestor. If you like my instructables see my youtube channel! http ... More »
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