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4hv.org :: Forums :: High Voltage
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Best arc I can get with 555

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Author Post
Platinum
Mon Feb 27 2012, 07:50PM Print View
Registered Member #3926
Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 505
Don't know why the driver I have just fails, gets warm on 12v input...

Here the 555 in 13vdc, and 45volts into the FET, limited by the primary of a ignition coil, as it's the only thing that doesn't melt, because of oil in it.

Sorry about the quality couldn't focus webcam...

Very little arcs here about 3.4cm very low current... :(



Why so fail?

Here is a schematic...



Zener and UF4007 removed. Could get more power by removing the limiting ignition coil, but I have only 1 555 timer, so I could also replace MOSFET for a better one like IRFP250n or even IRF640n... tried 250n, but it was a lower voltage arc....

I've seen a 555 on 30v 4a and it was very good power, I want higher voltage, not current, I'm also using the flyback's internal primary, which seems to give more power.
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Patrick
Mon Feb 27 2012, 07:59PM
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 4393
you are connecting the 13vdc with + and ground wires right?
and you are using both + and ground on your 45volt side right?


from your schematic it looks like maybe your 45volt main power is being poorly grounded or sunk through the IC... maybe?

given your posted schematic the 45volt should kill the 555 as you have drawn it.

excluding all the above posibilities, it may be that your timing freq is to short with on-time, or to low in freq... if everything else is correct.
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Platinum
Mon Feb 27 2012, 08:02PM
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Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 505
I know how the circuit works.

13VDC to - and + to 555 input, and 45vdc + to vcc+ on the output end of the driver, and - of 45vdc to - of the 555 input...

I think I'm doing it right, maybe I'm wrong?

Ever since I removed the TVS, the circuit is just bad... on 19vdc I could get very big arcs and with 45vdc input big arcs but not as big as 19vdc input when I got the driver...

So what's wrong, is there anything in the circuit that needs replacing because Sulaiman, did use this circuit on 12vdc 1a...
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Patrick
Mon Feb 27 2012, 08:04PM
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Location: Chico, CA. USA
Posts: 4393
Platinum wrote ...

I know how the circuit works.

13VDC to - and + to 555 input, and 45vdc + to vcc+ on the output end of the driver, and - of 45vdc to - of the 555 input...

45 volts should not be applied from pins 4,8 to pin 1, on the 555. is it?

what supply are you getting the 45 volts from? where did you get the 19volts from?
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Platinum
Mon Feb 27 2012, 08:06PM
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Posts: 505
I have applied 45vedc where it says 20vdc on the schematic...
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Patrick
Mon Feb 27 2012, 08:08PM
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Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 4393
disconnect your 45v supply, reconnect your 19v supply and tell me how well the 19v circuit works...do you still get the High energy output like before?
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m4ge123
Mon Feb 27 2012, 08:10PM
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Joined: Mon Oct 03 2011, 04:50PM
Location: MD
Posts: 140
Take out the ignition coil...
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Platinum
Mon Feb 27 2012, 08:12PM
Registered Member #3926
Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 505
19vdc is terrible, it shuts off as it pulls to much current. MOSFET needs a fan...

Sorry about this schematic, but this is how I power the circuit.

Instead of 19vdc I'm using 45vdc for more power, the 19vdc is a laptop SMPS, 19v 4a.

The 45vdc is a CB radio supply, I modified, for just the transformer and bridge and smoothing caps, and it output 45vdc and 20a shortcircuit, then the voltage drops to 25v...

Thanks for helping.

If I take out the ignition coil, then I'll probably blow it up.



Maybe an IRFP250N would be better...



Before I used 5v for the 555, but the gate threshhold is 10v I think, so now I use 13v to turn the gate on all the way.
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Patrick
Mon Feb 27 2012, 08:15PM
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Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
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Platinum wrote ...


If I take out the ignition coil, then I'll probably blow it up.


yes it will.

I presume you are using the primary of the iggy as the limiter?
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Platinum
Mon Feb 27 2012, 08:18PM
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Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 505
Yes, and I'm also using the primary of flyback...

So any problem with the circuit?
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Patrick
Mon Feb 27 2012, 08:19PM
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Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 4393
Platinum wrote ...

Yes, and I'm also using the primary of flyback...

So any problem with the circuit?

you should be getting hv out of both then, the iggy and flyback.

your effectivley dividing your 45v and whatever Amps between two transformers, with vastly different frequency behaviours. i trying to think.... what freq are you operating the 555 at?
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Platinum
Mon Feb 27 2012, 08:20PM
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Location: UK.
Posts: 505
No, the frequency is very high for the ignition coil.

Is there anything in the circuit that needs taking out, mind you the circuit is a awesome plasma speaker on 45volts.
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Patrick
Mon Feb 27 2012, 08:23PM
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Location: Chico, CA. USA
Posts: 4393
Platinum wrote ...

No, the frequency is very high for the ignition coil.

Is there anything in the circuit that needs taking out, mind you the circuit is a awesome plasma speaker on 45volts.

the iggy wont respond well above 6khz, but the flyback wont do well until above 10kHz or more, the iron of the iggy and ferrite of the flyback are not series compatible. thats your problem.

i think you should get a 10 or 20 ohm power resistor, then change the freq and on-time.
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Platinum
Mon Feb 27 2012, 10:57PM
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Location: UK.
Posts: 505
But it works bad without the iggy too.


Conundrum...
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Marko
Tue Feb 28 2012, 10:22AM
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Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Hm, the output looks great to me for such a crappy circuit, especialy if you've put an ignition coil or whatever in series with flyback primary?


You can limit the voltage overshoot by placing a capacitor in parallel with the mosfet, which will recycle the stored energy back to the supply.
The flyback will still saturate when drawing arcs though and very hot or blown mosfets would be no surprise.


And actually, I've shown you a schematic based on UC3842 some time ago that solved both problems, but you decided to ignore it.

Marko
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Platinum
Tue Feb 28 2012, 12:57PM
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Location: UK.
Posts: 505
I don't have the parts to build that, but I'm going to try to build a halfbridge soon...
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Patrick
Tue Feb 28 2012, 05:38PM
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Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 4393
Platinum wrote ...

I don't have the parts to build that, but I'm going to try to build a halfbridge soon...
A halfbridge is way more complicated than any of the circuits you have so far built, and i dont think you have learned enough yet to move on to a bridge arrangment of any kind yet. if you cant get the parts for a UC type ic circuit, i seriously doubt youll get even some of the parts needed for a half bridge.

you still have much to learn about the single switches before you will be able to move on.
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Platinum
Wed Feb 29 2012, 12:10AM
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Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 505
I know how ZVS works, and 555, but not much, anyway I would still like to build a halfbridge, or at least a good driver...

I don't like the 555, and I don't like the ZVS driver.
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Thomas W
Wed Feb 29 2012, 01:38AM
Registered Member #3324
Joined: Sun Oct 17 2010, 06:57PM
Location: UK, Dorset, Broadstone
Posts: 1192
Just.. learn how it works inside out and dont kill yourself with it, a halfbridge can be more dangerous then a ZVS if used in the 'correct' way, i was really worried when you were saying how youve been getting electricuted by the ZVS i sold you... just stay alive

-Tom Williamson
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ASHPoD
Wed Feb 29 2012, 01:48AM
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Joined: Thu Jul 21 2011, 01:52AM
Location: Orlando, FL
Posts: 657
Ask quack, he is telling me how to make one.
this is the schematic he's telling me to use:
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Platinum
Wed Feb 29 2012, 12:30PM
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Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 505
Tom Williamson wrote ...

Just.. learn how it works inside out and dont kill yourself with it, a halfbridge can be more dangerous then a ZVS if used in the 'correct' way, i was really worried when you were saying how youve been getting electricuted by the ZVS i sold you... just stay alive

-Tom Williamson


I going to go halfbridge, if I die I die, which I wont....The ZVS you sold me was fail, I've made it alot better...
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Alex M
Wed Feb 29 2012, 02:31PM
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Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 551
HighVoltageChick wrote ...

Ask quack, he is telling me how to make one.
this is the schematic he's telling me to use:




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Daedronus
Wed Feb 29 2012, 06:20PM
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Joined: Tue Sep 01 2009, 08:25AM
Location:
Posts: 353
lol, my feelings exactly

on the other hand not long ago I was trying to drive high side mosfets with low side drivers and wandering why it didn't work.

in my case just as in this case the problem is a lack of understanding of basic stuff.
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Platinum
Wed Feb 29 2012, 07:35PM
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Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 505
Yes I'm a noob, but I have basic understanding how 555 and halfbridges work...

I would like to build a simple h bridge...
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Patrick
Thu Mar 01 2012, 03:16AM
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Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 4393
Platinum wrote ...

... but I have basic understanding how 555 and halfbridges work...

I think not, or your previous circuits would be working well by now.

I dont want to discourage you, or be too harsh, but thats how i see it. Also you really need a O-scope for a full h bridge, the timing of the gate waveforms are pretty important.
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teravolt
Thu Mar 01 2012, 04:43AM
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Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1047
hi Platinum, a 555 has a voltage range of 3-18 rail voltage . take R4 and put it in series with the drain and ground your source same as pin 1 on the 555. you could try putting your uf4007 in series with R4 as I sujested or in parallel with the drain and source. I suspect that you are getting kickback from your coils. each one has a sertian amount of resonance so you want to turn your fet on for only 180 of that frequency. to do this you may want to convert your 555 to a straight oscilator and add a one shot and driver to the output for gate drive.
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teravolt
Thu Mar 01 2012, 05:30AM
Registered Member #195
Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1047
like this

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Platinum
Thu Mar 01 2012, 10:20PM
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Joined: Fri Jun 03 2011, 08:32PM
Location: UK.
Posts: 505
Patrick wrote ...

Platinum wrote ...

... but I have basic understanding how 555 and halfbridges work...

I think not, or your previous circuits would be working well by now.

I dont want to discourage you, or be too harsh, but thats how i see it. Also you really need a O-scope for a full h bridge, the timing of the gate waveforms are pretty important.



When I said basic understanding, I meant it...

Yes I need a O-scope, but I don't have the money...
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teravolt
Thu Mar 01 2012, 10:40PM
Registered Member #195
Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1047
for something basic you could get one of those 1MHz color one chanel 100$ hand dso scope would get you over the hump. I also bought a old tecktronics scope for 100 on ebay
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Xray
Fri Mar 02 2012, 04:35AM
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Joined: Sun Nov 21 2010, 02:04AM
Location: Minnesota, USA
Posts: 288
teravolt wrote ...

for something basic you could get one of those 1MHz color one chanel 100$ hand dso scope would get you over the hump. I also bought a old tecktronics scope for 100 on ebay


Yes, you can get a very nice tektronix scope for a fraction of the original cost. I bought a model 453 dual channel, dual trace portable scope for $160.00 a few years ago, and it's been one of my most valuable and most used pieces of test equipment.

I've heard mixed reviews of those little color pocket scopes. I never played with one, so I don't know how good or how bad they are, but in my opinion if you're going to spend that much money for scope, you would be better off buying a used American made tek or hp scope. Just make sure that the buyer gives you some sort of guarantee or right of return in case it doesn't work, or is in poor condition.
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