Friday, 8 July 2011

LM386 is godsend.

LM386 is very fun. It is a multi-purpose power amplifier 8 pin chip designed to amplify small power. I ve used it to amplify small signal from my crystal radio receiver and it works marvelously! It can even power up an 8 ohm speaker, to the sound level of mobile phone speaker.

This amazing chip i bought from Ebay for GBP 3.17 , and got ten of them. To use it as crystal radio amplifier, just Google the circuit schematic. I ve used the following schematic from


Is LM386 only amplifying audio signal?? Nope. Like i said in first line, it is a MULTI PURPOSE POWER AMPLIFIER. Therefore, I deduced if I can amplify sawtooth signals generated from ubiquitous 555 DC pulse generator chip (another chip, not to be confused with LM 386), and further amplifying the resulting pulses with transformer, then I can get high frequency, high voltage, low current alternating current. Lets see...

The overall view. At the very left is the 12V DC battery power supply. Note two chips on the breadboard. The first one is 555 timer while the second one on the right side is the so called LM386. At the very right lies the so called transformer. I cracked open a battery charger to get this transformer, which its original role is to convert 240V AC current from mains to about 2.8V DC for battery charging purpose. I inverted its role as a step up transformer, by connecting its secondary to the circuit on the board. By applying 12V to the circuit ( where 4.3V goes to the primary of the transformer that linked to the circuit), I got 183V, 66mA alternating current at the very end of the transformer's secondary ( the red wire at the end of the transformer, see the magnified view below).

The close look on the transformer. The red ends are carrying high voltage between them (183 VAC), high frequency (about 200Hz) low current (66mA). When you touch it, you will feel a zap, but more pleasant and less painful than conventional shocking pen. I touched it many times becuz it felt great. :P

What amazed me the most about the high voltage high frequency current circuit above is that when I touch the two red ends, I felt the same impulse i ve got when I touched the shocking pen few years before but less painful and more fun. Back then, I wondered how did the shocking pen (shown by my friend to me) can gave such a very painful shock, now i manage to build the circuit myself! Haha. But poorly, this big circuit never ever fit any pen. Maybe its miniaturization will become my next project.

The ensuing photos explains more than words can do...

The circuit...actually the LM386 parts ( the power amplifier circuit) is just the one being depicted before. The 555 part can be Googled anywhere, it generates spike signals. I used spike signals rather than square or sinusoid since spike gives more intense impulse to our fingers. :D

The overall circuit. I dont know how to rotate it, you do it yourself.:P

Next project, small Tesla coil. Gotta work, see me in the next post.


  1. Can it detects impulse signal and convert it into bit(s)? Mcm2 aplikasi blh guna peranti tersebut...

    knpa tak gabung pengetahuan sdra ttg kimia dgn elektronik? Invent new cell fuel? New chip?

  2. I am not much into computing so i cant answer to your question bout bits. If i m not mistaken, 555 is used to generate pulsed DC, not to detect impulse. Correct me if i m wrong.

    Bout that invention, thats already in my plans. Pray for me. :D

  3. ok then. good luck. Insya'Allah. first -vision, second -implementation. nice work.