Building a Functional Lie Detector: Troubleshooting Tips and Breadboard Basics

In summary, the individual is trying to build a simple lie detector and has encountered issues with their LEDS getting destroyed and not turning on properly. They are seeking help to verify their breadboard setup and looking for a tutorial on breadboard basics. They receive assistance with correcting their schematic and successfully getting the green LED to turn on, but are still having trouble with the red LED. They ask for a double check on the transistor placement in the schematic.
  • #1
maverick99
74
0
I'm trying to build this simple lie detector (picture below). I'm 90% sure that i have it built correct on my breadboard, but for some reason my LEDS are getting destroyed if i try applying the full 9V. It takes around 3V to make the LEDS to turn on about halfway. For some reason, there is a lot of current going through this thing. If someone could draw the components on a breadboard picture for me that would be awesome. I just need to see if I'm building this right. Also, if anyone knows a good site that has a tutorial of the basics of breadboards i would appreciate that too.
Thanks
 

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  • #2
This "should" work.
 

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  • #3
faust9 said:
This "should" work.


Alright thx! I owe you!
I will be shore to reply once i test it out on monday!
 
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  • #4
I tried it in class today and I'm 90% sure i set it up right. It doesn't turn the leds on at all. Can you double check the schematic?
 
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  • #5
here is a picture of the circuit itself not on a breadboard if it helps
 

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  • #6
http://www.iguanalabs.com/breadboard.htm

You're right though. It appears I drew VR1 to the collector of T3 but it should go to the b ase of T2. R1 and R2 are labeled backwards but that's inconsequential.

The VR change should fix everything.
 
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  • #7
alright cool thx
 
  • #8
I switched the VR1 today and now my green LED comes on, but for some reason my red LED isn't coming on. I have tried applying lower resistances to the probes, but the red LED isn't coming on. Are all of the transistors in the right spots on the schematic you drew? If you could double check, i would greatly appreciate it.
 

Related to Building a Functional Lie Detector: Troubleshooting Tips and Breadboard Basics

What is a lie detector and how does it work?

A lie detector, also known as a polygraph, is a device used to measure and record physiological responses in an individual when they are asked a series of questions. It works by measuring changes in a person's blood pressure, heart rate, respiration, and skin conductivity, which are believed to increase when a person is lying.

How accurate is a lie detector?

The accuracy of a lie detector varies and depends on many factors such as the type of questions asked, the experience and training of the person administering the test, and the physiological responses of the individual being tested. Studies have shown that the accuracy rate of a lie detector ranges from 75-90%.

Can someone cheat a lie detector test?

It is possible for someone to manipulate their physiological responses and cheat a lie detector test, especially if they are trained to do so. However, polygraph examiners are trained to detect these attempts and have techniques to ensure the accuracy of the test.

What are some common challenges when troubleshooting a lie detector?

Some common challenges when troubleshooting a lie detector include technical malfunctions, environmental factors such as noise or distractions, and the individual being tested not understanding the questions or being too nervous, which can affect their physiological responses.

Are there any alternative methods to a lie detector test?

Yes, there are alternative methods to a lie detector test, such as voice stress analysis, brain imaging techniques, and microexpression analysis. However, these methods also have their limitations and may not be as widely accepted as a polygraph test.

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