Today we will make a lie detector with our own hands, which measures different reactions that are sent by the body to human skin in different situations and with different emotions. The coolest thing is that all these reactions can be seen on the Arduino graph.
Step 1: How it works
Our skin is an amazing organ. It is a conductor when we touch anything, it protects us from disease, it holds all our organs together, but you probably didn't realize that the skin changes electrical conductivity depending on things that affect our mood! This effect is called electrodermal activity (EDA) and you can read more about it on Wikipedia. Simply put, our skin changes electrical conductivity depending on how we feel.
We will start by connecting the Arduino to the research object, and then connect the Arduino and the computer with graphics software. The following steps will tell you how to do this.
We need to start asking the subject easy questions that we know for sure that he will answer truthfully. For example, “what is your name?”, “where do you live?” - this is how we set the baseline. We can then start asking questions that the subject may answer with a lie, and if so, he will likely be nervous, and we can read this from the change in the baseline we noted before.
Step 2: Parts List
We need a microcontroller that will control three diodes and send data to the computer. In order for the computer to receive data, the microcontroller must have a serial communication chip. This means we won't be able to use an Arduino Pro Mini or an Adafruit Trinket, so when choosing a microcontroller, make sure it has a serial communication chip (USB communication chip) built into it.
Electronics list:
- Arduino Nano (link)
- Green LED (link)
- Red LED (link)
- Orange LED (link)
- 10k resistor (link)
- Wires
List of materials:
- Cardboard
- Foil
- Velcro
- Hot glue
List of tools:
- Hot glue gun
- Stationery knife
Step 3: Wiring
The wiring is very simple, we will start connecting everything in this order:
- Connect a long piece of wire to analog pin 0 on the Arduino
- Connect the 2K resistor to ground and to extended pin 0 of the Arduino
- Connect a long piece of cable to the 5 volt pin of the Arduino
- Connect the anode (long leg) of the green LED to pin 2, and the cathode (short leg) to ground
- Connect the anode of the orange diode to pin 3 of the Arduino, and the cathode to ground
- Connect the anode of the red diode to pin 4, and the cathode to ground
This is all the wiring associated with the Arduino. Now we need to somehow secure the sensor wires to the fingers - we will return to this later.
Step 4: Software and code
To create a polygraph with our own hands, we will use the latest software - Arduino IDE. The latest update provided users with new opportunities to perceive data received from Arduino. Instead of a textual representation received from the serial port, the information can be displayed in the form of real-time graphs. This will help us determine when the data changes its dynamics (when someone is lying).
To open the graph builder, open Arduino and go to the tools menu, there you will find the tool you need.
Now download the attached code and upload it to the Arduino board.
Files
Step 5: Creating the Finger Clips
Now that the basics of the project are complete, we can start adding to it. Let's start by creating clips for the fingers - this will make the device more convenient, creating a reliable connection between the fingers and the wires. Glue the foil to the outside of the Velcro (you need to glue it to both parts: the “hooked” part and the “curly” part). Now wrap it around your finger until it forms a tight ring (see photos). Then secure the bare end of the wire coming from pin 0 to the foil. Do the same with the 5V pin. Make sure to create a reliable connection.
Step 6: Making the Case
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The plan is to create a small compartment in which the finger pads will be folded and make 3 holes for the LEDs to peek out of. The case can be made from cardboard and, if you want the same case as mine, then do the following:
- Cut two rectangles 15*3 cm
- Cut one rectangle 15*5 cm
- Three rectangles 5*3 cm (make a hole for USB in the middle of one of them)
- One rectangle 9*5 cm
- One rectangle 6*5 cm
A 5*15 rectangle is the base. Two pieces 15*3 and two pieces 5*3 are glued to the sides of the base. Next, glue the third piece of 5*3 to the base at a distance of 6 cm from the edge (closer to the middle - see photo). Now you should have a rectangle divided into two parts - one 6 cm long and the other 9 cm. In the 6 cm long part we will put the electronics, and in the other part we will put the finger pads.
Next, in a piece of cardboard 6*5 cm, cut three holes according to the size of the diodes and glue it to the 6 cm side (it will be the cover). Finally, we need to tape the short side of the 9*5cm rectangle to the remaining open part of the box (this piece of cardboard will act as a lid that opens up and down, giving us access to the finger pads).
Step 7: Putting it all together
Finally, we need to assemble the lie detector together and secure all the electronics in the case. Start by gluing the Arduino and all the wires to the short part of the case. Thread the long wires into the second half of the case. Glue three LEDs to the holes and start testing. If everything is done correctly, then you will have a portable lie detector using Arduino. But I want to warn you that this system is not very accurate, since in fact most of these detectors have other sensors in addition, such as a heart rate sensor, etc.
Do you want to know if your loved one is cheating on you? Or maybe you're working on a science project?
This simple lie detector can be done at home using fairly simple electronic devices. If you are a child, please ask an adult to help you.
Read also:
1. Find something suitable that you will use as an electrode (conductor). You can use metal alligator clips, but this may cause harm to the person you are testing.
Can be used to make a home lie detector electrode pads for hospital equipment, but requires the use of wire and electrical tape.
2. Assemble the circuit according to the diagram.
Do not attempt to test the device on a person until you have fully assembled it.
3. Attach the electrode to the back of the subject's hand.
Place the electrodes at a distance of approximately 2.5 cm. Place the measuring device where the current strength is zero. If the instrument readings begin to fluctuate, it means the subject is lying.
4. Resistance measurement:
This DIY lie detector is based on measuring skin resistance. When you tell a lie human skin loses part of its ability to resist pressure. Such a system will measure the subject's resistance and alert you when a lie is told. Keep in mind that this system is very simplified compared to professional detectors.
The veracity of the information provided by the subject can be verified in many ways (analysis of collected facts, psychological testing). There is also a special device called a polygraph or lie detector. It’s difficult to assemble this kind of device at home, but making a cool toy for pranking friends in a fun company is quite possible.
Simple polygraph (lie detector) diagram:
In order to find out the truth from a person, it is not necessary to inject him with psychotropic drugs or torture him by putting needles under his nails, you need to use more humane methods.
Before you begin your experiments to determine the truth, you must understand that a lie detector or polygraph does not show whether a person is telling the truth or a lie. The polygraph only indicates a change in the psychophysiological state - which in turn may indicate the presence of a stressful state that occurs when lying. The fact is that when a person lies, he is usually nervous. And stress leads to changes in the general condition of the human body, for example, palms begin to sweat, eyelids twitch, or pupils dilate.
The principle of operation of a lie detector (the diagram of which is given below) is based on the fact that when a person lies, his palms usually sweat.
Figure No. 1 - Scheme of a simple lie detector R1 – 47 KOhm
R2 – 47 KOhm (Build precision)
R4 – 10 KOhm
R5, R6 – 1 MOhm
VT1, VT2, VT3 – 3102 (n-p-n)
VD1, VD2 – Green and red LEDs
The lie detector circuit is very simple and cheap, available elements are used. Any conductive surfaces can be used as sensors. You can use pieces of foil or metal as a sensor, or solder wires to ordinary iron coins. I didn’t try very hard to check the functionality of the circuit, and therefore I assembled a surface-mounted lie detector, and used simple candy foil as electrodes.
Figure No. 2 - My version of the device The circuit can be powered from a Krona battery (9V) or any stable power supply. Resistors R5, R6 are a voltage divider, and thanks to it, the voltage on the sensors at the moment of switching on is half the supply voltage (about 4.5 V).
The lie detector circuit works very simply, the voltage at the point between R5 and R6 varies depending on whether the skin resistance is less than or equal to the resistance of resistor R6. The voltage at this point drops if the skin resistance drops (palms sweat). Capacitor C1 acts as a low-pass filter (removes low-frequency interference and interference from the human body). A buffer stage operating in emitter follower mode is assembled on transistors VT2, VT3. VT1, VT2 is a voltage comparator, and if the voltage at the base of transistor VT1 is higher than at VT2, then the green LED lights up (which means the person is telling the truth), but if it’s the other way around, then the person is lying and the red LED lights up.
Setting up the circuit is quite simple. Take both electrodes in your palm and rotate the knob of the tuning resistor R2 until the red LED goes out and the green LED lights up.
Figure No. 3 – How to hold the electrodes in your hands Then wet your palms slightly and pick up the sensors again. The red LED should light up (this state corresponds to the moment when a person is lying)
As a rule, when a person lies, he experiences stress on a subconscious level (nervous) and begins to sweat (palms sweat). The resistance of dry skin is about one megaohm. The resistance of wet skin (sweaty palms) decreases by about ten times, and this leads to a voltage drop at the base of transistor VT2 and the red LED signals a lie.
The given circuit (polygraph) lie detector is just an ordinary toy, the results of which should not be particularly trusted.
We hope you have a good time playing pranks on your friends with this simple lie detector. But we warn you right away, it is quite difficult to recognize lies, specially trained people do this, so you should not trust the readings of a dubious device, but trust yourself and your family and friends! And also don’t forget to visit
Electromagnetic radiation is constantly around us, but it is inaccessible to human hearing. If you want to hear electromagnetic radiation, you can use a special device that we will make with our own hands.
To make an electromagnetic radiation detector we will need:
- old cassette player;
- glue;
The cassette player needs to be disassembled and the board removed from the case itself. It is recommended to familiarize yourself with the board not only for self-development, but also to ensure that no parts are broken when assembling and disassembling this device. This part is very sensitive to electromagnetic waves.
The most important part on the board is the read head, which will be useful to us later.
There are two wires near the read head, which are secured with bolts. These bolts will need to be unscrewed. After unscrewing the bolts, the reading head should remain, which will hang on the cable. You need to be extremely careful with it so as not to tear it off.
If the player does not have an external speaker, then we connect ordinary headphones to a special connector, which will help us hear electromagnetic waves.
Now we lean the read head against the TV. We can hear electromagnetic radiation. The radiation can be heard at a distance of up to 40 cm, the further we move away, the worse the sound will be heard. It is important to note that the old TV (cube) gives us a lot of radiation.
If we connect our device to a new generation of TVs (liquid crystal), we will also hear interference, but not so strong.
A big surprise was the fact that even the TV remote control emits electromagnetic radiation.
It's no secret that radiation also comes from the phone. When tested, the sound was similar to when you make a call and have your speakers turned on. The radiation comes from absolutely any phone, even the coolest and most sophisticated one, and you don’t have to dial the number, you can go online.
Even ordinary phone chargers and door handles emit electromagnetic radiation.
Using a regular player, you can hear radiation that is not heard by the ears and not seen by the eyes.
One of the most popular methods for determining a person’s honesty, desire to hide information or involvement in any events is the use of a polygraph, commonly referred to as a lie detector. The proposal to test using such a machine makes you nervous even when there is no reason for it, and makes you think about how to deceive a lie detector. This happens because polygraph testing is an interrogation, if we talk about the essence. Every person has personal secrets that he would not like to talk about.
Is it possible to fool a lie detector?
There is no single answer to the question of how non-experts can deceive a lie detector. According to reviews from people who service the device, the program has perfect sensitivity and is able to detect any slightest desire to lie. This is due to the fact that our subconscious mind keeps a trace of events that took place in the past, so no matter what you try to think about, the subconscious mind itself will give a reaction. A lie causes a kind of conflict between the consciousness, which is trying to control the situation, and the subconscious, which is recognized by a lie detector.
Secret service workers who undergo special training can deceive a polygraph. There is an opinion that not only agents, but also certain categories of people are capable of outwitting a lie detector: pathological liars who themselves believe in their lies, and actors. Lawyers who have to deal with the polygraph believe that rumors about it are an advertisement for the device and a kind of psychological preparation of subjects for the procedure, and the result of the test largely depends on the level of training of the specialist reading the indicators.
Where can I take the test and the cost of the service?
In almost every city there are companies offering lie detector testing. For example, in St. Petersburg it is the “Laboratory of Truth”. This service is not provided free of charge. Its cost depends on the reason for the application and varies from 4 to 5 thousand rubles: investigation of theft - 5,000 rubles, employment verification - 4,000 rubles. Muscovites can order the service at the Center for Applied Psychophysiology.
Depending on the reason for the request, the price varies, ranging from 3 to 6 thousand rubles. The most expensive studies are those of a private nature. For residents of other cities, the website Detector-online.ru offers an online lie detector service. In addition, there are several free applications that can be installed on your phone. With their help, gadget owners can take the test themselves.
Ways to fool a lie detector
There are several very diverse, sometimes naive, methods of protection against this device, described in the literature for specialists working with polygraphs. Among them are such as rubbing antiperspirants on the palms of the hands, armpits, and taking 5 aspirin tablets before the test. Real practice proves the low effectiveness of such methods. In addition to them, there are also ways to deceive the polygraph, which are usually divided into three types:
- Psychological – ways to concentrate on other situations (solving problems in the mind, reading poetry),
- Pharmacological – use of sleeping pills, psychotropic, stimulant drugs before the test,
- Mechanical – attempts to distract from the procedure by causing unpleasant sensations to oneself (biting the tongue, squeezing the sphincter).
What questions are asked during the inspection?
Lie detector testing lasts from two to three hours with short five-minute breaks. During this time, the printer will be able to ask about a hundred questions. They are repeated periodically, which allows you to find out accurate information about the subject. The text includes questions that determine the presence of negative or illegal experiences: has the subject ever stolen, taken and is taking drugs, committed minor violations (has crossed the road in the wrong place).
In some cases, the printer is interested in his personal life: has there been any family betrayal? Overly frank and intimate questions are not asked during the interview. In addition, if testing using a lie detector is carried out when applying for a job, then they ask about the attitude towards management in general, towards others, towards a specific company, and towards maintaining trade secrets. Before asking tricky questions, printers offer to talk about their negative experiences without using equipment.
How to pass a polygraph without problems when applying for a job
Testing an employee applying for a job with a lie detector comes down to finding out his lifestyle, attitude towards his professional responsibilities, and ability to meet the requirements of the team. First of all, you cannot lie during testing, because a lie is perceived by the employer as evidence of dishonesty. In fact, the employer is more interested not in the fact of your past mistakes, but in your attitude towards them. How can a test subject fool a lie detector?
- Do not take any medications, alcohol or drugs before the procedure. This step will be regarded as an attempt to hide the truth. The specialist will definitely note this in the examination report on the detector.
- Get a good night's sleep.
- Use the oxymoron method, the deliberate use of contradictory answers.
- If questions are used that are incorrect, unclear, or that affect your interests, views, or beliefs, you have the right to refuse to answer them or you can ask to reformulate them during the polygraph test.
- Don't try to hide the truth, answer sincerely.
- The results of testing on the detector in many companies, with the exception of government agencies, are advisory in nature. The final word remains with the leader. Therefore, do not lose your composure and confidence in the successful outcome of the matter.
How to influence the test results
Several tips from polygraph specialists can help influence the results of a lie detector examination. Among them is breathing control. After a problematic question, subjects take a “breath of relief.” In addition, with the help of breathing it is possible to control blood pressure and heart rate. To learn this, use breathing exercises and yoga. Playing the fool will help you bypass the polygraph.
In this case, you should be extremely non-serious when testing on the detector. Due to frequent illogical answers, the lie detector will become confused and will not be able to determine the required calibration. To avoid being suspected of deliberately strange behavior, which will only cause a negative attitude towards your person, you must adhere to the rule of the “golden mean”. Acting skills will help to cope with the lie detector, thanks to which the test subject tries on the role of another person.
A long lack of sleep will help you bypass the polygraph, deceive it, and hide your true thoughts. At this time, the body is in a state of trance, reactions to questions will be insignificant, which will be shown by the result. But the most important recommendation is not to exaggerate the role of the polygraph, perceive the procedure on the detector as something ordinary, nothing insignificant in your life, and certainly not fateful.
Video: how to fool a polygraph
The detector is designed to record changes in pressure and heart rate in order to determine the veracity of the subject’s answers. To do this, sensors are attached to the human body to ensure that changes in physiological parameters are transmitted to the computer. Experts from the NLP Institute demonstrate how this is done. In preparation for the examination procedure, the polygraph examiner and his subject reveal some secrets of the lie detector, which you can learn about if you watch the video from YouTube: