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4hv.org :: Forums :: General Science and Electronics
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Help calculating the frequency of this timer!

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Plasmaarc452
Fri Jul 25 2008, 04:23AM Print
Plasmaarc452 Registered Member #1394 Joined: Sun Mar 16 2008, 06:18PM
Location:
Posts: 111
Ok I just finished building this 555 flyback driver but now I need to know what what frequency is operates at.

This is the driver

Link2

Now here is the formula I used

F = 1/(.693 x C x (R1+R2))
The website I got the formula from was Link2 scroll down to the astable operation and there it is.

I am assuming that the potentiometers are at there max 10k setting.

F = 1/(.693 x .00000001 x (11,000 + 11,000)

I got 6,560 Hz

Can anyone tell me if this is the correct frequency? It does seem kind of low for a flyback but then again the potentiometers were at there max.

Also the duty cycle

Same website but this is the duty cycle formula

D = (R1+R2) / (R1+ 2R2)

I got a 66% duty cycle which seems about right.

I just want to make sure these formulas work for this configuration.

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Myke
Fri Jul 25 2008, 05:10AM
Myke Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969
Yup, seems right. I think flybacks like low or high duty cycles.you might also want to put some snubber on the mosfet so that the spikes don't kill it. The snubber would be a backwards diode and a cap I think.
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Dr. Dark Current
Fri Jul 25 2008, 12:07PM
Dr. Dark Current Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
You might consider replacing the IRF510 with IRF540. You might get maybe 4x less heating.
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Plasmaarc452
Fri Jul 25 2008, 10:56PM
Plasmaarc452 Registered Member #1394 Joined: Sun Mar 16 2008, 06:18PM
Location:
Posts: 111
Thanks for checking, the duty cycle and frequency seemed to be about right but I needed to make sure!

I am going to replace the mosfet and rebuild part of this circuit to make it capable of 36v at 20amps like the zvs driver.
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Dr. SSTC
Fri Jul 25 2008, 11:16PM
Dr. SSTC Registered Member #1407 Joined: Fri Mar 21 2008, 07:09AM
Location:
Posts: 222
Dr. Kilovolt wrote ...

You might consider replacing the IRF510 with IRF540. You might get maybe 4x less heating.


and 3 times longer arcs tongue
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