EMF "geiger counter"

Hi all. I am trying to build a EMF sensor that announces detection with "clicks" similar to a geiger counter. however, I have been getting almost no readings through the serial port. The method I am using has a 1M ohm resistor between an analog input and the ground. Is the Arduino sensitive enough for this or do I need an amplifier of some type?

Also, not quite sure how to map levels of emf to distance between clicks.

Thanks, Will

While photons are particles, they do not come in discrete events like ionizing radiation.

It is more of a continuous wave. However, you still cannot detect "emf" they way you want to, you will probably need an amplifier or receiver if you want frequency selectivity.

All you might detect this way is 60/50 Hz.

Im just trying to detect electromagnetic waves from operating electronics, etc. something like this - http://makezine.com/2009/05/15/making-the-arduino-emf-detector/

While photons are particles, they do not come in discrete events like ionizing radiation.

Yes, they do, if the equipment is designed to detect them as particles (like ordinary photographic film).

It is quite easy to demonstrate this.

Bitten by QM again!

I was trying to distinguish between the discrete decay event that the geiger counter catches and the wave nature of typical EMF generation.

mrwillcreates: The method I am using has a 1M ohm resistor between an analog input and the ground. Is the Arduino sensitive enough for this or do I need an amplifier of some type?

adc does not read rf or short pulses. you need antenna and diode. avr comparator is better for this than adc. in fact even plain digital is good enough. for extreme sensitivity dollar ebay "radiation flash" modules can detect very low power rf and emf many meter away:

http://www.ebay.com/itm/Mobile-Phone-Signal-Flash-Light-Radiation-Power-DIY-Suite-BEST-US-/191437972872?hash=item2c9297a588:g:3MUAAOSwzOxUXcHV

mrwillcreates, that is not a serious project, but it can be fun (a little). The 3M3 or 1M makes a difference. I suggest to use a resistor between 3M3 and 10M and use a wire that is long enough.

Thanks for the help! I'll try using a 3.3M.

Don't use any resistor.

Just use a diode to each supply rail.

a lot depend on whether you want to sense electro-static fields or electro-magnetic fields. generally emf refers to the latter in context of equipment noise.

if thats the case no resistor will just cause random readings as pin floats high or low. diodes to supply rails alone are no better. a resistor without any diodes at all dont work either for reasons i mentioned.

you need an antenna (wire or coil), diode, and very weak pull-down. theoretically a cap too but the few internal pf of pins works as long as the resistor to gnd is at least 10meg or more. dc biasing can increase sensitivity or for real gain use the circuit i linked earlier. i suggest looking at the schematic and parts list which are available for that.

if electro-static sensing instead of electro-magnetic is required then you need electrometer grade transistors (ie 2n4117 nfet) and glass resistors in the hundreds or thousands of megohms (not cheap).

i have been involved in the design of both types.

john1993:
a lot depend on whether you want to sense electro-static fields or electro-magnetic fields. generally emf refers to the latter in context of equipment noise.

Sorry, wrong.

By convention, “EMF” refers to Voltage, not “electromagnetic field”.

And the device that mrwillcreates cites is in fact an electrostatic field detector using a 3.3M resistor. The one you cited detects only UHF or microwave radio transmissions - and then only the high-powered pulse transmissions of digital mobile phones very close nearby. The question is - was that what mrwillcreates wanted?

john1993:
if thats the case no resistor will just cause random readings as pin floats high or low. diodes to supply rails alone are no better. a resistor without any diodes at all dont work either for reasons I mentioned.

The diodes to the supply rails do two things - they protect the Arduino from static, which is important, and they keep the input voltage in the range the Arduino can sense. Any sensitive EMF detector will indeed pick up random fluctuations, and for maximum sensitivity you want to utilise the full input impedance (hundreds of Megohms) of the Arduino chip without any lower resistance damping it.

john1993:
if electro-static sensing instead of electro-magnetic is required then you need electrometer grade transistors (ie 2n4117 nfet) and glass resistors in the hundreds or thousands of megohms (not cheap).

However the input impedance of the Arduino with no resistor at all is a convenient approximation.

john1993:
i have been involved in the design of both types.

I am sure you have, but what this fellow wants is a simple indicator of field. What I have suggested, with a short “antenna” wire on a digital input with only the diodes, will rather nicely approximate his “Geiger Counter” concept; with some low-level random fluctuations as a background, and a more definite response corresponding to mains or low RF fields in the vicinity.

Paul__B:
Sorry, wrong.
By convention, … refers to Voltage, not “electromagnetic field”.

EMF measurement - Wikipedia :

EMF measurements are measurements of ambient (surrounding) electromagnetic fields that are performed using particular sensors or probes, such as EMF meters. These probes can be generally considered as antennas

Paul__B:
The one you cited detects only UHF or microwave radio transmissions - and then only the high-powered pulse transmissions of digital mobile phones very close nearby.

actually that circuit as-is will detect a cell phone and also low frequency devices from many meters away. idk if you consider that “very close nearby”. frequency is determined by inductor turns and with proper tuning can detect milliwatt transmissions up to couple kilometers.

simply removing the coil completely allows detection of just about any emf, static or magnetic. this includes cloud charge, ambient 60hz, and am or fm stations. in fact with minor biasing mod can sense waving your hand few meter away. so my point was this is an excellent starting point for high sensitivity measurements of all types of emf.

without more info we dont exactly know what op needs in the way of type or sensitivity so my comments are directed at anyone interested in emf experiments in general. i am convinced an unconnected avr input or one with just a resistor is of little use here. ymmv.