Any electronics buffs?

Cigaro · World Chat Champion Joined: 28 Mar 2007 Karma :

Hi,

I need a 555 timer IC circuit with variable frequency from around 10 to 1000 hz. Could someone please give me a schematic and tell me what value of variable resistor to use?

Also, I wish to drive a small transformer with it to create high voltage AC, what sort of power transistor should I use at the output? Do I need a diode on the transformerr's primary?

Cheers!!

The Shaggy D.A. · Super Spammer Joined: 12 Sep 2008 Karma :

For the first question...

https://www.elektropage.com/555timer/?id=25

...still thinking about the second Smile

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nick606 · World Chat Champion Joined: 12 Nov 2006 Karma :

What you making ? a tazer Laughing

yandy_yay · Brolly Dolly Joined: 01 Aug 2008 Karma :

What kind of voltages where you thinking of switching ? primary coil resistance ? and yes i'd slap a crowbar diode across the primary to stop the back EMF popping your transistor maybe a fast switching shotskey (however you spell it)

Anyd

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carvell · Scuttler Joined: 05 Sep 2003 Karma :

Try something like a TIP120 on the output, make sure you check the specs and calculate the output power you're going to be switching (use the resistance of the coil) to ensure that it'll handle it. I'm pretty sure the transistor will handle 5A on the collector so you should be fine.

No need for a diode with the TIP120, it handles it.

Consider a power MOSFET too.

What PSU voltage/current are you using?
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rotax81 · Nearly there... Joined: 10 Sep 2008 Karma :

i got a book from maplins about a year ago.

its called something like 'ic 555 circuits and was about £5.
it has all sorts of circuits in there using the ic555 timer chip Thumbs Up

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