From what I see he basically creates a crude radio transmitter and receiver and uses his body as the channel to pass the radio waves between the two. I reproduced the experiment and it does work and now I'd like to experiment a little further with sending signal through the human body as I assume different frequencies, amplitudes and signal power work better than others.
First I need to create different signals with different amplitudes (peak to peak voltage?) and frequencies. I know I can get signal generators that can do high Mhz signals but they are mains powered and I'm a bit apprehensive about grabbing the wires of something thats connected that way; if I could find a battery powered one that goes up into the high Mhz range that would be ideal but all I've found so far are ones that max out at around 2Mhz; can anyone suggest a better one?
Second the transmitter power has me curious; the amplifier used in the above guide was an LM386 power amplifier which suggests a regular op amp wouldn't have been powerful enough to make the setup work.
Would I be right in thinking that I could safely connect a power amplifier like the lm386 to the output of the signal generator to give me the required power to make a system with variable signal work (so long as it's within the amplifiers signal range etc)?
Thank you for any help you can offer or suggestions for the above.
That is all there is to that Instructable. It has nothing to do with radio.
So where would I go to find out more about what is actually going on in the above experiment? Seeing as the signal has nothing to do with radio in any way at all whatsoever I would like to know what sort of signal it actually is if it isn't radio; I would like to know what areas of study I can look into to learn more about it and experiment with it safely and effectively.
arduino_x:
Which is just as well, since RF burns are not for the feint-hearted, in the most literal sense.
That brought back memories of submarine life. While surfaced coming into port, the junior officers liked to sit on these nifty stools that raised out of the top of the sail. Those stools are also known as a an-bra-34 antenna which we would be transmitting UHF on.
Then why does it also work if you make the wires long enough like antennas and put them into proximity with one another but not touching? (30cm apart)
The human body conducts electricity.
That is all there is to that Instructable. It has nothing to do with radio.
Seeing as this definitely isn't in any way related to a radio setup or anything even tenuously similar to a radio signal in any way at all whatsoever of course.
Parasitic capacitive coupling
Capacitive coupling is often unintended, such as the capacitance between two wires or PCB traces that are next to each other.
Edit: If you really, really want to believe that this observation has something to do with radio, then you can think about it in the following way. In the case of two parallel wires, the varying electric fields between the wires cause varying charges to accumulate on the wires, and an AC (audio) signal can thereby be effectively conducted over the air gap, just as an AC signal is conducted through a capacitor with no direct electrical connection. It is a "near field" effect, whereas radio is generally regarded as a "far field" effect.
The Instructable however, works by conduction of current directly through the body, and demonstrates why you should not stick your fingers in a light socket.
Edit: If you really, really want to believe that this observation has something to do with radio, then you can think about it in the following way. In the case of two parallel wires, the varying electric fields between the wires cause varying charges to accumulate on the wires, and an AC (audio) signal can thereby be effectively conducted over the air gap, just as an AC signal is conducted through a capacitor with no direct electrical connection. It is a "near field" effect, whereas radio is generally regarded as a "far field" effect.
Yes an oscillator connected to an antenna inducing signal in another wire through means of an electric field does sound slightly similar to the principle behind radio.
Whatever the signal is whether it be capactivie coupling or just electricity induced in the body; surely it must be possible to safely and effectively experiment with it with respect to sending signal through the human body?
jremington:
To experiment with the human body as a conductor of electricity, use only low voltages (< 20 volts) and low currents (< 1 mA). Stay dry.
And MOST DEFINITELY don't use your wife as the test subject. I did that with a remote dog training collar. The wife didn't see me touch the two together (turning it off) when she tried it on me. I just tensed up a bit every time I saw the red light come on in the transmitter. We traded, and again, I touched the two together (turning it ON, set to 10) and let er rip. Oh boy....a sailors mouth she had. I wasn't allowed to put it on the dog after that incident.
Okay perhaps It's best to approach this 1 question at a time.
We have two circuits...
A "transmitter" (effectively an audio amplifier with an output linked to an antenna)...
And a receiver (a series of transistors with an antenna)...
And a conductor (the human body with resistance so essentially a resistor) joining the two.
So we have essentially a resistor between the two antennas.
We have the two above circuits joined with a resistor and current is flowing from the transmitter to the receiver.
This seems strange to me as I was always under the impression that for electricity to flow you needed a complete circuit with a return path (IE a common ground etc).
How can electricity be flowing between the two circuits when there is no common ground or return path?
AC currents are flowing through all the stray capacitances to ground, not shown in your diagrams.
That is why an audio oscillator is required to show the effect.
If you just touch the audio amplifier input terminal, you should be able to hear a hum from the 50/60 Hz house wiring, capacitively coupled to your body.
Yes , later they switched to 2 wire communication.
In early training days i took part in a restoration// display of early devices.
I think one of them is now at the science museum next to madame tusssaurds.
