Hi guys, this is Jason, a college student interested in helping Fukushima inhabitants by making and donating a pocket radiation detector for the ones in need.

I found that currently existing Geiger counters in the market are often too complicated and time consuming to quickly detect the polluted food or area (radiation hot spots).

So I wanted to make a simple radiation detector with a sensitive PIN photodiode and a blinking LED. What I am aiming to make is a radiation detector similar to this one on the URL below.

Ref. #1
http://www.techlib.com/science/geiger.html#Worlds Smallest

However, although I have managed to build one based on the circuit above, it was not operating properly. (If you know the reason please share your insight with me.)

So I am attempting to make a new one by referring to your article below.

Ref. #2
http://einstlab.web.fc2.com/Xdetector/detector.html


What i wanted to ask for your help is:

My goal for now is making a simple detector with a blinking LED (increasing frequency with increasing intensity of radiation) instead of a sophisticated monitor attached on Ref. #2.

In order to do so, i believe i need to add a circuit with a transistor or an op amp in order to drive the LED that i want to add. However, i am not capable to come up with the exact circuit.

Can you guys help me how to adjust the circuit Ref. #2 to meet the goal?

I appreciate your help in advance.

 

Simple cheap detectors only have very low sensitivity. They will be useless for safety checking where the radiation under test will be extremely low.

You should do some homework before thinking about taking this project further.

 

If you are attempting to detect low level radiation you need to be able to detect and count single photons. The sensitivity of the detector will depend on the energy of each photon and hence on the radioactive element.

Small, compact Geiger-Muller tubes are available for building your own detector.

 

http://www.ohio.edu/people/piccard/radnotes/detectors.html

I believe you might want to look at the use of photographic film products, perhaps something like the Polaroid self-developing ones, for cheap and easy ways to detect contaminated objects and food-stuffs.

 

If I may wade in with a few comments.

1) The people of Fukushima have government sponsored surveillance of radiation levels in their food and environment. Remember, this country has good reason to be very concerned about nuclear radiation. Having said that, many people will find peace of mine with the device you propose.

2) Radiation detection is all about statistics in a simple way. The intensity of radiation can be viewed as the number of photons/second/square cm. If you use a small area detector you will just have to wait proportionally longer in order to make a assessment with a given accuracy.