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555 Stun gun producing less volts than power supply

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brotherbear

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trying to make this https://www.555-timer-circuits.com/stun-gun.html its for educational purposes so please do not frown upon this thread. For some reason my circuit produces only 200mV max. I got the wrong transformer don't I? I got this one:

1K ohm Centre Tapped - 8 ohm Output Transformer
- Primary/secondary 1k ct/8 ohms
- Ferrite core
- 350mW rating.

Also could someone redraw the voltage multipler part of the circuit so I could check if I did anything wrong with mine.

Thanks.
 

Audioguru

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The 555 operates at a fairly low audio frequency and the diodes are very slow. So you should use a 1k ohm to 8 ohm audio transformer with the 8 ohm winding at the BD679 and the 1k winding at the voltage multiplier. The article should say the required power rating of the transformer which might be 10W or more.
A transformer with a ferrite core is for high ultrasonic frequencies or higher. Your small transformer might be for a ultrasonic pest repeller.

The voltage multiplier is already clearly drawn.
 

FvM

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As mentioned by Audioguru, you apparently connected the transformer the wrong way.

It should be however noted, that there's a fair chance that the transformer burns immediately, either due to primary overcurrent, or secondary insulation breakdown.
 

brotherbear

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The 555 operates at a fairly low audio frequency and the diodes are very slow. So you should use a 1k ohm to 8 ohm audio transformer with the 8 ohm winding at the BD679 and the 1k winding at the voltage multiplier. The article should say the required power rating of the transformer which might be 10W or more.
A transformer with a ferrite core is for high ultrasonic frequencies or higher. Your small transformer might be for a ultrasonic pest repeller.

The voltage multiplier is already clearly drawn.

how do I tell which side of the transformer is which? one side has 3 legs other side has 2
 

Allen6502

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The side with 3 legs is most probably the primary (1K ohm). Is this an audio transformer from transistor radio?

Allen
 

SunnySkyguy

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Audio transformer insulation is not suited for very high voltage maybe a few kV . You can get far better results with a small auto ignition coil. 30kV for example.

Energy out will not exceed what you put in e.g. E=1/2 L I^2 * t [Joules]
 

Audioguru

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The side with 3 legs is most probably the primary (1K ohm). Is this an audio transformer from transistor radio?
Brother bear said that the transformer has a ferrite core so I think he is wrong, it is probably an old little audio output transformer that will be overloaded in this powerful zapper application.
I think my portable AM radio had a little audio output transformer about 57 years ago.

- - - Updated - - -

If the 1k output impedance of the transformer is properly matched (I doubt it) then I calculate the current in the 8 ohm primary winding of the transformer to be 11V/8 ohms= 1.38A peak. It is powered only half the time. Then the power rating of the transformer should be at least (11V x 1.38A)/2= 7.6W. So the little 350mW transformer is 21 times too small.
 

Allen6502

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You can either use an old TV flyback transformer or auto ignition coil as mentioned by SunnySkyguy. Or get a stepdown transformer from a wall wart and use the low voltage side as the primary.

Or you can buy a 220V to 6v-0-6v transfromer from eBay....

https://www.ebay.com/itm/1-EI-Ferrite-Core-Input-220V-50Hz-Vertical-Mount-Electric-Power-Transformer-2W-/281090986530?pt=LH_DefaultDomain_0&var=&hash=item4172541222

They should work better than the little output transformer that you're using.

Allen
 

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