So why don't we use NE555 for voltage doubling and negative voltages?

[rustypinto]

I was able to add a -33 volt charge pump output to a 555 based SMPS, which I detailed in this thread (halfway down page 6): http://www.diystompboxes.com/smfforum/index.php?topic=74088.100

I had a couple of stabs at using a 555 as a charge pump for positive voltage doubling with multiple doubling stages, but didn't get it completed before (as usual) I got sidetracked by another project.

I was looking for that thread too, thanks!

Did you apply your -33V to anything (tube, transistor, any other amplifying device)? I'm just curious about the noise you might be getting from that unruly BJT-type 555. It was just awful in my findings, noise on the order of +/-100mV with a TI NE555P.

[frequencycentral]

OK, I have succeeded in using a NE555 as a charge pump to generate 80.5 volts. Cool. 



The circuit is running from a 12 volt supply. Not tested under load yet, I'm hoping to run a Murder One from it, but I'm out of output transformers at the moment. I'm also assuming that the 100pF cap is putting the oscillator well above the audio range.

If all works out it will be pretty cool - I need 12 caps and 12 diodes to get 80 volts out of a MAX1044 - this circuit does it with less components, and the cost of an NE555 compared to the cost of a MAX1044 is a joke.

[PRR]

> So why don't we use NE555....

The newer chips are better promoted. And documented for this chore.

The 555 is a big crude beast. It can dump 200mA, much more than the new toys (far-far most than CD400x CMOS gates). OTOH it wastes about a Volt, which hurts when working from 5V or 3V supply. And sucks quite a few mA even when not doing anything; the new-toys are far thriftier on small loads.

There are times when the new-toys just won't pull the load. Your "80V" supply has 8X leverage. (Already we see you only get 10.1V action from your 12V supply: that's about half 555 losses.) Whatever current you suck from your 80V node is reflected back at least 8 times bigger (and I suspect 16 times bigger?). So even with the brutal 200mA available, you may only get a few mA at 80V before smokage.

And classic 555 is not protected against all overload.

Note also that small diodes like your 1N4148 may be rated 100mA. The 555 may be able to kill the first one before it quits. If they survive, the first diode has a few tenths more voltage drop (multipled by 8 to the final voltage) than a larger diode. However jellybean 1N4007 won't turn-off quickly at 20KHz rates, which spoils the action.

> Not tested under load yet

That may be more "fun". Wigging the short end of a stick with 1:8 leverage is tough, much tougher when something is on the other end.

Ratios like you propose are more often done with transformer than diode-string. One lossy part instead of eight. But as mentioned, magnetic design is alien to many of us. You can get started by using wall-power iron. 12VDC totem-pole into 6VAC winding, or 12VDC push-pull into 24VCT winding, 100Hz-500Hz, can induce near 120V squarish-waves on the 120VAC winding. Yes, 400Hz vibrator is audible, but common power iron gets lossy long before you get out of the audio band, and you just can't beat the availablity of small power iron. Many-many car radios ran 400Hz vibrators and the whine was not too bad.

[alparent]

Don't want to hijack, just need some clarification.

I also need -9v for an effect I'm building. I know about the MAX1044 but don't have any.
I do have  A LOT of 555's.

Anybody have a schematic for a 555 based circuit that will give out +9v and -9v above 20khz that R.G. was talking about?

Thanks

[frequencycentral]

Anybody have a schematic for a 555 based circuit that will give out +9v and -9v above 20khz that R.G. was talking about?

http://www.circuitsonline.net/schakelingen/139/voedingen/negatieve-spanning-met-ne555.html

Not sure of the clock speed but you should be able to tweak it.

[alparent]

Thanks Rick.....................but the clock speed was the part I was wondering about? 

[frequencycentral]

Thanks Rick.....................but the clock speed was the part I was wondering about? 

Google translation says:

........delivers a square wave with a frequency of about 20 kHz.

It should work with 1n4148's in place of the BAT85's

[alparent]

What do I do to change the frequency like R.G. suggests?  

Do I just change the value of C2?

What frequency should I aim for?

[frequencycentral]

I think C1 is the timing cap. Probably best to google for a quick 555 tutorial though.

[frequencycentral]

OK, I have succeeded in using a NE555 as a charge pump to generate 80.5 volts. Cool.  



The circuit is running from a 12 volt supply. Not tested under load yet, I'm hoping to run a Murder One from it, but I'm out of output transformers at the moment. I'm also assuming that the 100pF cap is putting the oscillator well above the audio range.

If all works out it will be pretty cool - I need 12 caps and 12 diodes to get 80 volts out of a MAX1044 - this circuit does it with less components, and the cost of an NE555 compared to the cost of a MAX1044 is a joke.

Hmmm, some very weird results. I breadboarded and posted this a couple of weeks ago. I just got some output transformers delivered, so I thought I'd try the this charge pump under load. I plugged it in without load and found that I'm getting 52 volts. Whereas previously I was getting 80 volts. It's the exact same breadboarded circuit.  

So I breadboarded it again, using new components. Same result, 52 volts. I just can't work out why I was getting 80 volts 2 weeks ago but only 52 volts now. Anyway, under load (a Murder One amp) it drops to 45 volts. It powers the amp well, without any whining or noise. Good result in one way I guess, but I now need to add a few more doubling stages to get up to the desired voltage.

[earthtonesaudio]

The total energy output of a charge pump comes from the capacitors, through the diodes.  They are useful devices for generating high voltages (sometimes millions of volts) at low currents.  Ask more current from them and they will sag a LOT.  Remember that those 80 volts you measured at no load were coming from the output cap, and not the 555 (at least not directly).

The ways to increase the current are:
Increase the frequency
Increase the capacitance
Increase the current output from the oscillator

[frequencycentral]

Damn! gtudoran tried the 555 charge pump circuit today and got 82.5 volts. I'm soooooooo confused. Need to understand this. I want my 80 volts back!

[Renegadrian]

I could be dead wrong here, but I believe that raising that electros would help with more current?! say 220µF?!

[panterafanatic]

Can I combine caps to get higher voltage ratings like resistors for higher power? I've got a bunch of 50v 47uF but not 100v, can I use 4 50v to rig a 100v section?

[compuwade]

Can I combine caps to get higher voltage ratings like resistors for higher power? I've got a bunch of 50v 47uF but not 100v, can I use 4 50v to rig a 100v section?

No. You'd still be putting more than 50 volts across the caps. You can put smaller caps in parallel to make one larger cap. Like 2 100uf caps to make a total of 200uf. That works well. 

[PRR]

Identical caps in series, the voltage ratings almost add. Two 50V in series will stand this 84V; altho maybe not 100V.

In this plan the voltage increases 10V-11V per stage. You can go several stages with 50V caps. Start building, measure each stage. When you get to 40V, make your next stage a series-pair.

[compuwade]

Identical caps in series, the voltage ratings almost add. Two 50V in series will stand this 84V; altho maybe not 100V.

In this plan the voltage increases 10V-11V per stage. You can go several stages with 50V caps. Start building, measure each stage. When you get to 40V, make your next stage a series-pair.

I don't mean to be argumentative, but I've seen way too many electrolytic caps expload to be comfortable with doing something like that. I'm by no means an expert on the subject, and I'm sure it can work, but isn't it easier to just get a 150v cap and be done with it?

[PRR]

> isn't it easier to just get a 150v cap and be done with it?

YES.

But....

When we get past 450V, we can't use inexpensive electrolytic caps. Paper/plastic caps are easy to get but costly in large values. Many-many-many large tube amps "stack" e-caps to run at 400V to 700V.

panterafanatic has no 100V caps but an abundance of 50V caps. Me, I'd rather get some 100+V caps "and be done with it", the cost is not large (though the shipping-charges are worse than the parts-cost). But yeah I'd bread-board with whatever. (I've made some awful ugly breadboards.)

[kupervaser]

Does anyone have a vero layout of a voltage inverter for -9V with the 555 chip?

Thanx

[Hides-His-Eyes]

Does anyone have a vero layout of a voltage inverter for -9V with the 555 chip?

Thanx

Better: you do your best at making a vero and I promise we'll all double check it for you.

The only way to learn is to try it yourself!