Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

555 Stun gun producing less volts than power supply

Status
Not open for further replies.

brotherbear

Newbie level 3
Joined
Sep 15, 2014
Messages
3
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
24
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.
 

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.
 

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.
 

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
 

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

Allen
 

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]
 

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.
 

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....

**broken link removed**

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

Allen
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top