# Question about ne555 stun gun

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#### mohsen 2012

##### Member level 4
Hello , i want to build this stun gun based on ne555 :

I did not find the bd679 and the audio transformer , can i use bd537 instead of bd679?
and the transformer i have 220 to 9v centered tape step down transformer , her impedance is
1.2 k primary and 5 Ohms secondary :

#### FvM

##### Super Moderator
Staff member
can i use bd537 instead of bd679?
You should use a darlington transistor (BD537 isn't) or redesign the base drive circuit.

Considering diode and capacitor voltage rating, the 20 kV number looks like a joke.

#### mohsen 2012

##### Member level 4
You should use a darlington transistor (BD537 isn't) or redesign the base drive circuit.

Considering diode and capacitor voltage rating, the 20 kV number looks like a joke.

OK and what about the transformer ??

#### Audioguru

##### Advanced Member level 5
The original circuit used an audio transformer that works perfectly at the fairly high frequency used. Your low frequency mains transformer might not work at the high frequency. The slow mains diodes also might not work at the high frequency.
The simple circuit might stun a mosquito, not a person.

The original 8 ohms to 1k ohms transformer steps up the voltage about 67 times. Your 9V to 220V low frequency transformer will stepup the voltage a little more than 25 times.

#### FvM

##### Super Moderator
Staff member
The original 8 ohms to 1k ohms transformer steps up the voltage about 67 times.
No. The windings ratio can be expected to be squareroot(1000/8):1 = 11:1.

But we don't know anything about the transformer size. Similar the ridiculous 20 kV number...

#### Audioguru

##### Advanced Member level 5
I calculated 6VAC into the 8 ohm winding will produce 4.5W. Then I calculated that 67V into the 1k winding will also produce 4.5W. But I forgot to divide the 67V by the 6V to result in a voltage stepup amount of 11.2 times.

I do not calculate AC impedances of 1.2k and 5 ohms on the mains transformer. They are probably the DC resistances.
I think the original circuit produces about 300VDC at no current or about 80V at 10mA.

I saw a mosquito zapper tennis racket at The Dollar Store for only $3.00 and I think it comes with a battery worth$3.00 so the circuit is free. Maybe it is THIS circuit. I wonder how may volts it puts out?

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