Introduction: Simple Lie Detector (from Solid Components)

During the summer I have many times to build gadgets, and when I found this easy circuit on the internet I' ve decided to make my own and to show you how to build a lie detector. First of all I am 15 now and now learn english in the school so sorry for my bad english. When you put your fingers on the touchpads you activate the circuit and you will hear a static noise. If you lie your fingers will get moist and the speaker will change its noise.

Step 1: Tools and Materials

*Materials: 2 AA Batteries

-Battery box

-9V battery clip (if you have a battery box like me)

-A small cardboard box

-A 8R speaker

-2x100k and 1x1k resister

-1 BC557 transistor and 1 BC547 transistor

-Electrical Tape

-2 pieces of 1.5x1.5 inch aluminium foil

-Wires

*Tools: Soldering Iron, Glue Gun, Needle

Step 2: Making the Circuit

I've made my circuit with an other speaker, but it worked fine. You need to solder two wires to the touchpads, because those will come out from the box. Be careful with the transistors, one of them is NPN and the another is PNP.

Step 3: Building the Case

1. With a glue gun we need to glue everything inside the cardboard box. On the bottom I put the 9V battery clip, because my battery box can connect to it, on the top is the speaker. With a needle you need to make two holes for the wires of the touchpads and ten or more holes for the speaker. The electronics are just simply soldered together, not on a PCB board. You can make another design. At the end you need to make the touchpads, which connects to the two wires.

Step 4: Testing

Put your fingers on the touchpads, and lie for a question. If you lie you will hear a static noise.

Now make your own lie detector and try it on a freind!
This is an easy project for school, or just for fun. I hpe you like it!

Comments

author
daniel -williams (author)2017-01-11

how do you put the wires andall the transitors and resisters together

author
mohaimenmahtab (author)2016-08-14

what is the scientific explanation of this project???. i want to know how every component worked.
thank you

author
grimreaper122 (author)2016-02-02

would a 9v battery fry the circut

author
ShubhraG (author)2016-01-18

Also could you clarify what the battery box is?

author
Imetomi (author)ShubhraG2016-01-18

It's a bettery box for 2 AA batteries.

author
ShubhraG (author)2016-01-18

Could you provide a rough estimate of the time taken to build this? Trying to do some time planning.

author
Imetomi (author)ShubhraG2016-01-18

Hm, if you have the parts already one or a half hour is enough. So isn't a hard project.

author
aarushi1605 (author)2015-10-25

amazing project!

though it would help a lot if you could upload a video or give step by step instructions for the circuit.

thanks.

author
aarushi1605 (author)2015-10-25

amazing project!

though it would help a lot if you could upload a video or give step by step instructions for the circuit.

thanks.

author
LillianG made it! (author)2015-07-01

We made four of these at the Silver City Public Library in Silver City, New Mexico, USA this June 2015. Young students helped create them; it was a great way to teach soldering. I have one comment: I did not realize until the last minute that the project requires a 10nF capacitor. I have been learning how to read circuit diagrams, and I had trouble identifying the two parallel lines that said "10n" next to them. The capacitor is not on your list of materials. Please add it to the list, if possible! Thank you.

20150630_165629.jpg
author
Mol_Hale (author)LillianG2015-10-15

What was the voltage on your capacitors?

author
LillianG (author)Mol_Hale2015-10-24

500 volts maximum. It seemed to work well; adding the capacitor to the circuit caused the sounds to change more subtly depending on the amount of contact made with the user's skin.

author
Ayush0007 (author)2015-09-04

Please make a video bro

author
Imetomi (author)2015-02-23

Sorry for the late reply! Thank you for the interesting and I answered the questions in a message, hope it was helpful gor you.

author
shihabudeenshanavas.s (author)2015-02-20

we r doing this as our mini project....thank you

author
souheib.sfaxi (author)2015-02-13

Hi, i did it but the noise is irregular and it doesn't depend on lying or not, do you have any solutions ?

author
Mateo JCF (author)souheib.sfaxi2015-02-19

Hello souheib.sfaxi! I had this problem before and it turns out that some bare wires were touching, finishing an unwanted circuit. So make sure that no bare wires are touching and hopefully that will solve the problem. Hope this helps!

author
Mr AbAk (author)2015-02-10

Cool Ible......

author
Imetomi (author)Mr AbAk2015-02-10

Thank you

author
Han_Solo_Order66 (author)2015-01-10

might put it on emp power gaunlet

author
india5spp (author)2014-11-10

No problem! And I am going to make this, so some how will let you know who it works!

author
amansinghaljpr (author)2014-11-10

Probably your English was good but this project is actually not a lie detector it will always beep when you put your fingers on the pad because our bodies always produce some current and we also have some resistance which help to saturate the base of the transistors so the speaker will always beep..... but hey nice try!!!!

author
Imetomi (author)amansinghaljpr2014-11-10

Yes, but when anybody lies the resistance of your finger will be smaller, so the speaker changes it's noise.

author
india5spp (author)2014-11-10

That's awesome! Why is your finger moist when you lie?

author
Imetomi (author)india5spp2014-11-10

When you lie you will be excited, and when you are excited usually your skin will be wet. And agian, thanks you!

author
muhuwj2 (author)2014-11-10

You're English was actually very good!

Anyways, that's one genius Instructable.

author
Master Wasi 47 (author)2014-11-10

Simply genius. I rated it.

author
Computothought (author)2014-11-09

NTE123AP=bc547

NTE159= bc557

author
Imetomi (author)2014-11-09

Thanks you all!

author
anguspodgorney (author)2014-11-09

Well done!

author
Electrospark (author)2014-11-09

Nice!

I'm going to make one of those! :)

author
Kafukai (author)2014-11-09

A lie detector is based on the heat level and urea in your sweat, actually it'll be more efficient on the forehead than the fingers. Try to upgrade it, good luck :-)

author
KookyKreations (author)2014-11-09

Your English is outstanding - your Instructable is clearer and better written than MANY by native English speakers. Keep up the good work. Nice project!

author
Imetomi (author)KookyKreations2014-11-09

Thank you very much!

About This Instructable

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Bio: Hi, I'm Tamas (Thomas), a 17 years old Hungarian guy. My hobby started more than 10 years ago. I learn electronics, physics, programming, IoT ... More »
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