how can turning on/off a switch produce electromagnetic force outwards?

[rata478]

I just recently tested this out with a simple frequency counter, is it because of the electromagnetic field around the wires collapsing/rising?

 

[BrunoARG]

If a high current is flowing through the wires and those are so long or are wrongly placed that they convert in a coil, an electromagnetic field will be generated.

Actually, a straight wire will create a elctromagnetic field if a current goes through it, and it will increase with current and the number of turns it has.

If a wire goes perpendicular to another its magnetic field won't affect the other cable signal at all. Try that if your device is not working well.

 

[D.A.(Tony)Stewart]

High impedance counter can detect AC field nearby or close to current with N loops around wire. This transforms current to Voltage from change in flux or visa versa. Low impedance probe would attenuate voltage.

the counter will have a threshold to ignore noise below a certain level with a variable threshold.

 

[rata478]

Im actually talking about the electrical grid in our homes,ive read about such things interfering and also wonder exactly on why, they seem to be at a way different frequentie so why does it interfere?

 

[D.A.(Tony)Stewart]

A current surge on switch on or a voltage arc on switch off , creates a fast risetime which spans a very wide spectrum. Could thu stray capacitance with ant wire acting as antenna will pick up more signal with higher frequency so glitches are most common.

Other than this , high impedance inputs are sensitive to low freq. AC hum if imbalanced or unshielded. A 10M probe can easily detect >50Vpp from human touch to tip only.

 

[Audioguru]

I think you are asking about interference crackles heard on an AM radio or seen on an analog AM TV picture. FM does not have the interference. Analog TV sound is also FM.

 

[D.A.(Tony)Stewart]

Very high voltage on a coil can be produced from rapid open current across a coil, such as a small LiPo cell across a large turn N coil . V=L deltaI/delta t, where delta t is <<1microsecond from a momentary relay close, open contact to coil.

normally in air HV pulse is 1-3kV per mm arc. when it breaks down.. Not when pulling away arc.

 

[rata478]

Very high voltage on a coil can be produced from rapid open current across a coil, such as a small LiPo cell across a large turn N coil . V=L deltaI/delta t, where delta t is <<1microsecond from a momentary relay close, open contact to coil.

normally in air HV pulse is 1-3kV per mm arc. when it breaks down.. Not when pulling away arc.

So basically when closing a switch at this high voltage it makes a arc which then ceates a electromagnetic field around it at random frequencys?

 

[BrunoARG]

Yes, both the coil and the spark (HV pulse).

If it's a high impedance input, add a pull-down resistor so it's less sensitive to static energy and ambient noise.

Chech how much current the IC output which is connected to the input can supply without suffering damages. Then you can calculate the minimum value for your pull down resistor. Put a value close to the minimum and increase it as much as possible whenever it works.