Introduction: How to Know Whether a Person Is Dead or Alive, Under a Second

By Analog Digital
About: DIY, Guy.I have a degree in electrical engineering. I have broken more thing than making one. But I usually combine 10 things that I have broken, to make one true masterpiece.

Warning:

Preface:
There are various ways to know, whether a person is dead or alive by measuring breathing pattern, heart beat or by using sophisticated brain scanner (Picture shown above). Measuring vital signs takes a lot of time and any novice will have a hard time figuring out the body parameters. Word device and DOAOS are used interchangeably in this article.

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I thought of making a small contraption using cheap, off the shelf electronic components, to measure whether person is dead or alive. The name of the device is Dead or Alive under one second (DOAOS). The final device is shown above.

I have incorporated animation, if you are facing any problem, you can see my whole article here or at http://rafalerobotics.in/doaos/

For more richer experience, view this article in my website, by clicking here.

Step 1: Device in Action

The final working device is shown below (testing my hands with it) and YES! I am alive.

The input probe is delivering the small current, which then flow through the hand and then picked by the output probe. If there is flow of current through the body, the output signal will be registered by the device and will turn ON LED and buzzer.

How does it work ?

Most of you must be wondering, hey this is cool, but wait a minute how does it work. It work on the principal of Electrodermal activity (EDA), sounds bizarre. Electrodermal activity refers to the variation of the electrical properties of the skin in response to sweat secretion. Our exposed skin always contain small amount of sweat, no matter what is the temperature outside. (see above pics)

Human body contain lots of nerves, which conduct signal from our brain to periphery and vice versa. These are divided into sympathetic nerves and parasympathetic nerves. These nerves are involuntary i.e. we can’t consciously control them. Our main focus area is on sympathetic nerves, because these are the nerves which control our sweat glands.

So, if you are alive (you must be, otherwise there is no way you can, read this), then your brain is continuously commanding your sweat glands via sympathetic nerves to produce sweat. Sweat (good electrolyte) this means we can use our body to conduct electricity.

What happens if a person is dead ?

If a person is dead, that means his/her brain is not working, the signal to turn ON the sweat glands will be off. If we attach our little device on this person, our device will not register any current (as there is no sweat for the flow of current) , and there would be not output. That means, Sorry! the person is gone.

Step 2: Demonstration of the Device (DOAOS)

a) Alive:

To stimulate, the working of the living hand. I made a quick small drawings of the hand. For mimicking the real sweat , I took some water and then put some common salt on it.

Then I put a drop of (salt+water) mixture onto hand drawing. Now I attached the two probes of the device on the salt-water mixture, which is representing sweat of our body.

If a person is alive, he will have small quantity of sweat on his/her body. The above experiment is stimulating the same scenario. We know, that sweat in our body is electrically conductive as well as the salt-water mixture in our drawing. After attaching the probes across the sweat, LED as well as buzzer will turn ON, and there will be continuous light and sound of LED and buzzer , indicating person under test (PUT) is alive.

b) Dead:

Finding a dead person was required for this experiment, as to make everyone believe, this is not hoax. I must admit, finding any sort of dead thing was nightmare for me. I had to find out a clearer way. I bought a doll from the shopping mall, because dolls are dead, and then I had made special coffin for the doll, let’s see what happens next.

I have attached the device on the armpit of the doll. You can see there is no output registered by the device. Lovely doll, you are dead. (see above pics)

Let’s zoom inside the hand of the doll, as to see what is really happening.

As you can see in the drawing,(see above for pics) there is no sweat present in the hand to conduct electricity, because sweat gland are no longer working in the dead body. The input probe and output probe are no longer sensing each other.
No sweat, No flow of electricity

Alas! Doll you are dead.

Step 3: Now Let’s Make Device Itself:

Bill of materials:

see above pictures for bill of materials.

Working of the device using block diagram:

a) Battery:

In this device, 9V battery is used, because these are ubiquitous and just by connecting with snap connector, we’re ready to go.

b) Transistor:

In this device 2N2222 NPN transistor is used, you can also use any small signal NPN transistor and it will work.

Transistor is used here as a switch. Right most leg of the transistor is collector, middle one is base, left most is emitter. Battery output is connected to the skin via input probe, this initiates flow of current throughout the body. The base of the transistor is one which measures the feeble current which is flowing throughout the body. If base of the transistor detects a current, it then allow a larger current to flow from collector to emitter. The LED and buzzer are connected in the path of current which flow between collector and emitter. If base detects any current it will turn ON the LED and buzzer.

c) Probes (Input & Output):
In the device, both input and output probes are the extension of wires, which are electrically conductive. Input probe allow current to flow from 9V battery to human skin via sweat. Output probe detects the feeble current which is flowing in the human body and then directs the current to the base of the transistor.

d) Output (LED & Buzzer):
LED and buzzer are the output component of the device. As already described, LED and buzzer are connected in between 9V battery and the emitter of the transistor. If base which is connected with the output probe, detects any current in the body, it will allow current to flow from collector to emitter, which will then turn ON LED and buzzer.

Schematic:

see above pictures for schematic diagram.

Step 4: Animation of the Device in Action:

GIF animation is not supported here, if you want to view animation of the device, you can watch it here or http://rafalerobotics.in/doaos/3/

For more richer experience, view this article in my website, by clicking here.

Animation explained:

The small inverted triangle in the above animation represents the battery. First current flows from battery to the red probe and in the skin. Then current starts flowing from one end of the skin to the other end. When the current reached the other side of the skin, it is picked up by the black probe The black probe samples the current from the skin and into the base of the transistor. Here in this configuration, transistor is used as a switch. As soon as current starts flowing in the base of the transistor, it allows a larger amount of current to flow from battery to the ground , thus turning both LED and buzzer ON. If black probe can’t sample the current, then LED and Buzzer will not turn ON.

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