EMF Detector

[Capsos]

Hi everyone. Ive worked with electronics for years but never progressed past basic. But for my job I want to build a hand help emf detector. Some jobs I go to they have issues with there WiFi and it's sometimes down to this and want a way to detect it and if so how much. Does anyone have a diagram and a parts list so I could build one please.

 

[Alec_t]

Welcome to EP!
'EMF' = voltage, which you can detect with a multi-meter.
Do you mean 'EMI' (Electro Magnetic Interference)?

 

[Irv]

http://www.instructables.com/id/Arduino-EMF-Detector/

You should be able to build this in 10 minutes with a few dollars worth of parts.

I would use a smaller Nano (Chinese copy of Arduino, 3 for $10 from Amazon),
and an OLED for readout ($10 same source) because of the low power requirements.

I run one from one of those little tube-shaped $5 cell phone rechargers for 50-60 hours before recharging. Makes it very portable. 9v battery works, also.

The program and pin connections will have to be modified slightly if you use the OLED, but the OLED is more like a tiny text terminal, rather than a simple 7 segment display. Obviously, more versatile.

I would fit the whole thing into a clear plastic tube 8 or 10" long, very portable and professional looking.

 

[Externet]

Electro magnetic field detector schematics :

---->https://duckduckgo.com/?q=emf+detector+schematic&iax=1&ia=images

 

[Capsos]

Welcome to EP!
'EMF' = voltage, which you can detect with a multi-meter.
Do you mean 'EMI' (Electro Magnetic Interference)?

Yes sorry. EMI "autocorrect"

 

[Irv]

EMF = Electro Magnetic Field https://www.cdc.gov/niosh/topics/emf/default.html
EMF = Electro Motive Force https://en.wikipedia.org/wiki/Electromotive_force
Same acronym, different results. One shocks you, the other cooks you. Now go have fun!

 

[davenn]

Yes sorry. EMI "autocorrect"

do you really want to detect 'EMI' (Electro Magnetic Interference)?
you first post didn't indicate that ....
but detecting interference is a whole different ball game involving very wideband scanning equip like spectrum analysers


you were right the first time
EMF = Electro Magnetic Field

EMF just happens to have another meaning that Alec_t latched onto

Are you specifically only wanting to detect WiFi signals ? there are units available to do that sort of thing
I use one when I am travelling to detect WiFi coming from motels etc that I may be able to log into whilst storm chasing

 

[Irv]

I would guess that he's suspects there's some machinery which generates RF noise which interferes with WiFi signals in the client's workplace. If that's the case, then walking around with an EMF detector would probably do the job, since the noise itself would likely be wideband.

On the other hand, there "could" be a source of interference which is on the same frequency as the client's wifi. (an illegal transmitter, perhaps?). That would take something different (maybe the FCC would like to know)

 

[Capsos]

do you really want to detect 'EMI' (Electro Magnetic Interference)?
you first post didn't indicate that ....
but detecting interference is a whole different ball game involving very wideband scanning equip like spectrum analysers


you were right the first time
EMF = Electro Magnetic Field

EMF just happens to have another meaning that Alec_t latched onto

Are you specifically only wanting to detect WiFi signals ? there are units available to do that sort of thing
I use one when I am travelling to detect WiFi coming from motels etc that I may be able to log into whilst storm chasing

I go to jobs when there WiFi / WAP units are having issues and sometimes its due to hi levels of EMI from hi voltage cables or power lines or something else. I wanted to make a scanner that could direct me to what ever is giving out high levels of EMI

 

[Capsos]

I would guess that he's suspects there's some machinery which generates RF noise which interferes with WiFi signals in the client's workplace. If that's the case, then walking around with an EMF detector would probably do the job, since the noise itself would likely be wideband.

On the other hand, there "could" be a source of interference which is on the same frequency as the client's wifi. (an illegal transmitter, perhaps?). That would take something different (maybe the FCC would like to know)

Yes that's it ! I try and trace the RF causing interface to the WAP / WiFi unit.

 

[davenn]

Yes that's it ! I try and trace the RF causing interface to the WAP / WiFi unit.

as I suggested that's where a high quality scanner or spectrum analyser are valuable for finding EMI

 

[Irv]

OP said he wanted to build one. Building a spectrum scanner or analyser is possible.
He also said he's a beginner. Not so possible.
A beginner building a high quality spectrum analyser? Still possible?

None of that is necessary, unless the noise is actually coming from a tuned circuit acting as a transmitter or an actual transmitter.

Any of the simple circuits posted earlier should do the job, with varying degrees of accuracy.

If you just want a light to flicker when some EMF is detected, use one of the 741 op amp circuits.

The Android circuits could give you a bit more info, such as relative level, if you need that.

If you want a user-built "spectrum scanner", then a $20 SDR would - sort of - work.
I have a couple of those, and they work to scan the spectrum, but:
1. they don't usually do well above 2ghz, and WiFi uses 2.4 and 5 ghz, and
2. they have lots of spikes from harmonics of the SDR and the computer that you use with it.
Most of those spikes won't be the spike you're looking for.

Or, buy a spectrum analyser, a few hundred to a few thousand dollars.

 

[(*steve*)]

If it's for detecting interference with WiFi then all you need is a WiFi module that can report noise levels.

There's a simple project using the nrf24l01 module that does just this.

 

[Irv]

Could there be another wifi router using the same frequency? There are free apps for phones/tablets that can display that info.

 

[(*steve*)]

It could just be a leaky microwave oven.