EMF Meter Project

[kpatz]

Here's some old pics from when I was starting to put it together:

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[audioguru]

Opamps with a low frequency response can pick up a cell phone at 900MHz or at 1.8GHz.
I think it is because the input transistor of the opamp is overloaded and becomes an AM detector diode then the opamp amplifies the low frequency modulation.

I don't know if an opamp can pickup a signal from a ghost.

 

[kpatz]

Opamps with a low frequency response can pick up a cell phone at 900MHz or at 1.8GHz.
I think it is because the input transistor of the opamp is overloaded and becomes an AM detector diode then the opamp amplifies the low frequency modulation.

I don't know if an opamp can pickup a signal from a ghost.

My latest iterations use BJT circuits on the input stages and then an op-amp for the final stage. So far this seems to work better to achieve the sensitivity I need. I use a dual op-amp and the second one conditions the signal to feed into the PIC's ADC.

My most recent amp attempt (still on a solderless breadboard) is sensitive enough to pick up my quartz analog wristwatch from several inches away, and it even responds if I wave a magnet across the coil, so it can go down to really low frequencies. And that's with my wimpy coil, not my Coil From Hell™.

 

[grendal]

As a tech manager, I don't sugguest building an emf meter yourself. Mainly cause they are so cheap now. However if you want to build something for ghost hunting, I sugguest a simple low frequency magnetic field flux meter. The principle behind emf, is that ghosts are a form of energy, this energy like heat, light and even rf, give off a electromagnetic radiation signature. Similar to how your current emf meter is picking up a light bulb. The only difference is, with ghosts it's believed to form in pockets with no apparent source. While I don't believe whats on tv, I know from experiance.

Another thing you could do is build a tri-field meter, though they are quite harder to build. Some places to hit would be, here FREE CIRCUIT DIAGRAMS 4U: August 2009, and elektor, elektor has a everyday practical electronics magazine where they did 2 emf meters. In comparison I found elektors emf meter little harder to trip, though the one your trying to build, was a little too easy to trigger. The best thing you can build though is a motion alarm. They are very handy when combined with cameras. For example, if I place a camera at the end of a hall way, I generally put 1 motion alarm in each door way, of the room, and in the hall it's self, and you want leds, so they light up when going off, along with sound.

When I get my computer up and running again I'll kick a few schematics and part lists your way.

 

[ghostman11]

eccentric enough to be British!!! utterly brilliant. i love posts like this

 

[Mr RB]

Opamps with a low frequency response can pick up a cell phone at 900MHz or at 1.8GHz.
...
I don't know if an opamp can pickup a signal from a ghost.

Maybe the ghost will be using a cell phone?

 

[ghostman11]

Maybe the ghost will be using a cell phone?

if they are i hope they got a beaver shield

 

[stdee]

https://www.surplussales.com/Images/Inductors/RFCoil/ich-240-5700.jpg

kpatz the emf cct calls for a one milli henry coil I hope the link above will show a picture of it

 

[stdee]

kpatz
here is a link i hope it works
https://www.epanorama.net/zen_schematics/Circuits/Testgear/emfprobe2.html

 

[stdee]

kpatz
here is a super simple one

https://www.epanorama.net/zen_schematics/Circuits/Misc/staticdet.html


you should be able to buy a one milli henry choke from RS in the states
but I have seen this stated to be about the same inductance
if they have not made a mistake, seems too few turns to me.

150 turns, 36swg
series wound over a 100k ohm one watt res

 

[teddyparis]

." I don't see a coil at all" It's probably because they use a hall detector. It's the same shape then a transistor. if you could teel use what is written on every "transistor looking" little component that could help. On the other side of the pcb is there anything at all? Im interesting in buying this product so if it only use a dualop and a hall capteur i'd rather build one than spend nearly 100usd with shipping !

 

[kpatz]

." I don't see a coil at all" It's probably because they use a hall detector

I haven't been on here to check this thread in a while, but I did purchase a K II and a couple other meters to "reverse engineer" when time permits (yeah right). I'll have to open up the K II and see if there is a Hall sensor in there. I thought one time I looked and only saw transistors though.

So far not much luck in getting ghost energy on my homemade meters, but I know a local ghost hunter that uses a certain $30 or so meter that seems to work well, so I may purchase one of those to reverse engineer.. maybe add an output jack to it so it can be connected to a digital audio recorder to capture whatever the meter is picking up... then I can tune the meter to whatever frequencies ghosts tend to produce.

 

[Dr_Doggy]

Hi folks... I've been developing a homemade EMF meter with LED bargraph display, and am looking for some tips on tweaking the EMF sensing circuit.

I don't have a schematic for my actual circuit handy (circuit's at home, I'm at work), but it's based on this one:

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But, if I disconnect the side of the coil going to the + input on the op amp in the schematic, leaving it free floating, then I can pick up fields. So, in essence, it's acting more as an antenna than an inductor. Any thoughts on this? Maybe I need a better coil?

My 2nd question: the circuit is a LOT more sensitive if I connect it to an earth ground, such as when I connect the grounding clip on my oscilloscope when taking readings. Any thoughts on this? Since I intend this device to be portable, I can't be earthing it all the time.


I'll post a more complete schematic this weekend when time permits, but thought I'd post what I have in case anyone has suggestions for making it better!

Thanks,
KJP

sounds like your pickup coil is out of tune with your compactor, and tunes in when you unplug the + pin, due to higher resistance,

Maybe run pickup coil to ground?

 

[teddyparis]

Here is a famous one made by Velleman. It's a very simple pcb, one layer only. could be very simple to reproduce BUT Those bastards drills the 3 UC !! so we can't see anything! It only shows that 2 Uc are ST electronics probably the same type (lm324??!) and the last one no idea. Here are pictures of this device ( cost around 40 usd ). It has 5 led to measure on-1-3-6-10 mg.

 

[teddyparis]

could you take a picture of the reverse side of the KII pcb please? thank you.

 

[teddyparis]

I did receive a K2 (rev4). I'm very disapointed. It's much less sensitive than the velleman emf ( the one above). and cost much more. It has no hall effect capteur, the coil is such a very simple 4 track printed on the board. it uses 3 npn transistor and 4 pnp (generic one: P100 and P200). besides that it use a lm324. So very simple very cheap and cost 60-50 usd !! defenitly go for the velleman with a real big coil not for this sh**.

 

[jbarrington]

kpatz,

I was noticing your topic and your project. I've been searching the web for an EMF project and saw yours. Would consider posting your final circuit EMF design here? I wouldn't mind tackling this too.

 

[tlhIngan]

Can we get an update on this?

 

[gauravjaina]

how much voltage are you getting into the amplifier and whats your gain

 

[pomoanbill221]

How about using the RS telephone pickup? You would still need to add some low pass filtering in your amp and roll it off around 50 hz so that 60 hz would not be detected, and use some rather large decoupling input caps to the op amp.