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There are many types of sensors "thermal - optical - Chemical ....." But here we will learn another type of sensitive he is sensitive touch .. Everyone knows Darlington circuit "consisting of two Transistor " that Amplify the current of a good rate.You can see the touch-sensitive circuit "Darlington"

https://www.instructables.com/id/Breadboarding-The-...

But what if we add a three Transistor to the circuit how would be amplifier!!

If that were amplification in Transistor is the first 200 will be the total amplification with the 3 Transistor is 200 * 200 * 200 = 8000000 gain

i found this circuit in amazing website. look at it you will see many of the wonderful circuits

http://www.talkingelectronics.com/

## Step 1: Some Info

This circuit is so sensitive it will detect "mains hum."

Simply move it across any wall and it will detect where the mains cable is located. It has a gain of about 200 x 200 x 200 = 8,000,000 and will also detect static electricity and the presence of your hand without any direct contact. You will be amazed what it detects! There is static electricity EVERYWHERE! The input of this circuit is classified as very high impedance.

## Step 2: What We Need

• - 3 transistor NPN {BC 547 - BC 337 ......}
• - 3 resistors {1 Mega ohm - 10/100 k ohm - 220 ohm }
• - LED 5 Millie "Any color of your choice"
• - power supply { 5 or 6 or ...volt whatever }
• - wires Of course

## Step 3: On Breadboard

Now you need to put the components and their connection to the breadboard. also show pictures that appear in front of you.

The wire that comes out of transistor first is the sensor wire, "he can fumbles for the lowest electrical signal and being amplified

## Step 4: Eventually

Finally, the circuit is ready to use you can add Antenna to Fumbles to areas farther than 1 meter .

i do not show you them how it's work i will let you to make it yourself and watch how its work Yourselves and you will certainly be surprised .... because it can even detected "ghost"

.

Thank you for reading I hope that you will have benefited

I'm sorry for my poor English

Will you please explain me how does this circuit work?
if I wanted to add another transistor, how would I do that? what resistor would I use?
<p>you can't add 4th transistors </p>
In theory, you should be able to add an infinite number of them. In practice however, I haven't been able to get the fourth one to work.
<p>i think you should better test it using hit &amp; trial method but of course the resistance of 4th resistor should be even less than 3rd.!</p>
<p>can you please post a tutorial and a test video</p>
<p>This would be an interesting thing to enter in the Sensors Contest....</p>
<p>yes exactly</p>
<p>Very nice idea and nicely done instructable.</p>
<p>thank you :-)</p>

### About This Instructable

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Bio: student at electrical engineering i'm proud to be like Nicola Tesla, EEngineer
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