Cap Dump Circuit

[Farmhand]

Disregarding the power dissipated by the switch due to slow rise and fall times I
think the following holds true.

Basically with a total Capacitor dump the rise time of the driving pulse which is the
close time of the switch is most important in order to begin max current flow
quickly.

But with a coil discharge the fall time of the driving pulse which is the opening
time of the switch is more important in order to collapse the magnetic field
quicker, which in turn causes a fast voltage rise from the coil discharge.

..

[BroMikey]

Great Information

Disregarding the power dissipated by the switch due to slow rise and fall times I
think the following holds true.

Basically with a total Capacitor dump the rise time of the driving pulse which is the
close time of the switch is most important in order to begin max current flow
quickly.

But with a coil discharge the fall time of the driving pulse which is the opening
time of the switch is more important in order to collapse the magnetic field
quicker, which in turn causes a fast voltage rise from the coil discharge.

..

Thanks A Million Farmhand

You have no idea what this kind of instruction means to me. That is a great circuit. I will keep it. I will ponder this circuit as I grow in confidence.

I had an old man 80years in the hood come to me saying his only transportation had failed him. It is a 36vdc scooter using 3 batteries in series 12ah each so this was my big chance.

I can effectively discharge at 90vdc. One batteries cracked and went bye bye. I had a replacement all conditioned and ready for the show. The other two were getting warm and I had to stop. They all charged up one at a time and together as well but you know how it is, only up 14plus volts, not the best.

But since I lost my big SG OSC I almost forgot how much it is needed. I have two others. Anyway the heat kept building and I realized after your post that my mind was not on the chemical aspect as it should have been.

I have been all through this time and time again. I just put 1 on the SG OSC at 10 watts, thanks

I just wasn't thinking when I said that cap dumping is good enough.

She was warming up and I know I have to cool it before proceeding. I usually wait 20 minute to an hour depending the size.

You guys are a great help and I want to thank you for popping in like this and correcting my path.

Encouragement is a powerful word. I am looking at the pixane controller and thinking.........Hummm..................do I need to pull out my code books???....Humm..............

Mike

[Farmhand]

Bromikey, one thing I wondered. Is your mosfet/switch in the positive rail above the battery or in the negative rail below the battery.

For driving mosfets a low side switch is the easiest to make work well.

It's good to help older folks, these days they tend to be overlooked a bit as far
as general helping hands and conversation goes. Well done.

Cheers

[BroMikey]

Negative

Bromikey, one thing I wondered. Is your mosfet/switch in the positive rail above the battery or in the negative rail below the battery.

For driving mosfets a low side switch is the easiest to make work well.

It's good to help older folks, these days they tend to be overlooked a bit as far
as general helping hands and conversation goes. Well done.

Cheers

Hey Farmhand I am 56yrs

My desire to do more electronix has blossomed these past few years.

I use the far right hand terminal source to bring in the negative side of my cap bank so my red wire goes directly from the cap hot to the battery hot.

So I pulse the negative wire. Is this good?

Mike

[BroMikey]

3Capacitor discharging Units

Bromikey, one thing I wondered. Is your mosfet/switch in the positive rail above the battery or in the negative rail below the battery.

For driving mosfets a low side switch is the easiest to make work well.

It's good to help older folks, these days they tend to be overlooked a bit as far
as general helping hands and conversation goes. Well done.

Cheers

This is how I have built 3 dumps

Mikey's Capacitor Discharge Unit fix.JPG

Mike

[BroMikey]

Pathetic Waveform

One more thing I have final learned tonight about my dumps. Let me say that I have been learning how to work this fancy scope (HP54100D) and tonight for the first time I realized that the way I had been previously viewing my wave forms is incorrect.

I am learning to use the "Magnify" function with this controls like "Offset" and "Vdiv" and fooled myself.

So you see the hundreds of hours of using this scope is paying off.

My waveform is a SAWTOOTH. This is one of the first waveforms all beginners generate. Turning off the Direct Current and then back on again.

I can see now that this sort of pulse is not going to compare at all to the latest rise and fall times associated with more modern topology.

Obviously this is good bye to the old way as this version for beginners started 100 years ago. I never realize how embarrassing this design actually looked on the scope til today.

Here she is, slower than molasses in January. Hilarious

But it works That is the funny part. Oh and real easy to build.

Sawtooth.JPG

Mike

[BroMikey]

Testing Phase

Continuing on with my progress I have ordered and installed all new Mosfet's and have shelved the IRFP250n Mosfets as they can not be used long term to pulse charge more than a 24vdc battery bank. Anything over 60vdc and up to 75vdc will randomly trash your project due to reflected back spikes.

This is not an oscillator. This is not a CLAMPED capacitor discharging circuit.

This is a circuit that welcomes some ringing and therefore MUST use a higher voltages rate HEXFET.

I will proceed no further til I am completely sure why I have blown dozens of FETS. I am getting very comfortable with my HEXFETS.

My silly drive circuit offers only a ms rise time and fall time and when using IRFP250's over 50volts they get hot fast under any kind of even a medium load as specified by the manufacture. This is because of the way my circuit is made so as not to eliminate ringing.

I have an adjustable supply 0-100vdc @30 amps that has a fan on both the variac and rectifier sink. It is hooked to a regular wall plug that will max out at 90vdc @20 amps so I can't turn it all of the way up.

I have 3 devices running for days now, they are the new IRFP450 FETS. I have pulsed these Mosfets up to 500 watts of repetitive discharges that go like this.

A single pulse is showing 20 amps and will actually be some larger value.

Pushing the duty and frec's to around 6hz @50 percent these 3 devices heat up about 8 degrees about room temp in 2-4 minutes without running the fan yet.

They can handle 90vdc all day long with a slow rise and fall time so I am finding out day after day that these part are going to do the job.

I will now add the remainder of my devices, 9 more.

Next will be the addition of the fast driving circuits. 6 drivers TC4420 6amp each driving 12 FETS, 2 fets per driver chip. I am looking at the idea of using heatsinks on my driver chips.

The one unknown is will a single TL594 power up 6 TC4420 drivers?

Mike

[BroMikey]

Radiant Cap charger

Here is a radiant Oscillator in forced MODE charging caps for dumping. The cap dumps operate at a higher efficiency when used together.

You can that his diagram.

Powerful Single Coil Radiant Charger by Sul-Tech - YouTube

This is very simple stuff, almost anyone can do.

600 miliamps at 19vdc is 11 watts that charges a 1000uf cap to 220vdc in seconds.

With an Oscillator like this filling capacitors a large battery can easily be charged from a tiny input.

I have used these Oscillators to fill caps in a cap dump circuit and watched the scope while the discharge occurs.

The Oscillator goes out of tuning for a few microseconds lowering it's output almost completely, when the dump takes place and this is best. There are other ways to turn off the supply to a cap dump momentarily like to employ a Mosfet switch controlled by a microprocessor based chip.

This radiant method (Bedini Forced Oscillator) of charging capacitors is more efficient and should also have some form of over voltage shutdown circuitry to protect the Oscillator if batteries fail to receive a charge or short out.

Either way capacitors are charged more advanced circuits are needed to perform a practical application than proof of concept.


If batteries are ever accidentally hooked up backwards circuits can be added to prevent this.
Simple Way To Prevent DC Reverse Polarity - YouTube

Mike

[BroMikey]

Capacitor Sizes

One very interesting thing I should add about capacitor sizes. Let's take two separate caps to look at so i might get this across to each of you.

I have one cap bank that is 48,000uf and it has a max voltages rating of 100vdc.

Next I have another cap bank that is 85,000uf with a higher than 100vdc max voltage rating.

Okay so now i have one bank almost twice as big as the other and each bank will only be charged to 31vdc.

What do you think happened? Well it is quite surprising really to me that the meter for the small dump shows a one half amp pulse.

The larger bank I figured should have shown double that or even better, yet it produces a 5 amp pulse.

Wow! Of course the bigger value dump is physically larger by 20X than the smaller value uf bank.

So we can see that for the same uf rating the figures are very deceiving and if you want a bank that holds more and can give back energy faster you need a larger physical size.

The smaller bank actually gives me less than i quoted so don't be fooled into thinking that all you will need is certain uf number without spreading out capacitance over a bigger area.

Caps types vary. They can all be electrolytic and still be worlds away from being anywhere near the same. A 50,000uf bank can be the size of a softball ( I have one) or it can be the size of a beach ball (I have that one also).

Another interesting thing to note about the larger dump i just mentioned is that when I charge the caps to 31vdc i get a 5amp pulse but when i lower the voltage down only a handful of volts to 25vdc my pulse is cut in half to only 2.5amps.

Using 250vdc capacitors is the way to go for the serious cap dump builder. The price is much higher for good reason. I think I paid $20 for the small one and the big one is worth over $700 depending on how much you want to spend.

Mike

[BroMikey]

TL594 Question

If anyone has any experience with the 594 as single pulse operation please fill in the blank. I have a picture below of the TL594 and you will notice the TIMING CAP and the TIMING RESISTOR Rt AND Ct.

The red arrows point at this section of the chip.

Question

What two part values would I start with to get say 10 pulses per second?

Thanks. I can do trial and error but maybe someone has used this circuit before for a cap dump.
594.JPG

Mike

[BroMikey]

TL594 Timing

Here is what I found from the semiconductor company

594Time.JPG

So going by this approx I need 200k of resistance using a .1uf cap.

Just more resistance should bring the pulses down to a slower speed according to this information.

Let me know if anyone is into using the TL594 and understands this question.

Mike

[BroMikey]

Dump Frequency

So far using the above formula I get this





1.1/ 200,000Ohm X .000001 Farads =5.5HZ

Mike

[BroMikey]

More questions

Also I have noticed engineers putting a .001uF cap from pin 2 to pin 3.

Some say polypropylene. Why? Does it filter better than a ceramic or what?

Here is the diagram



These questions will only apply to those who have built these circuits using the 594 chip.

Thanks, Mike

[BroMikey]

Answering my own Questions

Capacitor types

Ceramic capacitor: The ceramic capacitor is a type of capacitor that is used in many applications from audio to RF. Values range from a few picofarads to around 0.1 microfarads. Ceramic capacitor types are by far the most commonly used type of capacitor being cheap and reliable and their loss factor is particularly low although this is dependent on the exact dielectric in use. In view of their constructional properties, these capacitors are widely used both in leaded and surface mount formats Read more about the ceramic capacitor



Electrolytic capacitor: Electrolytic capacitors are a type of capacitor that is polarised. They are able to offer high capacitance values - typically above 1μF, and are most widely used for low frequency applications - power supplies, decoupling and audio coupling applications as they have a frequency limit if around 100 kHz. Read more about the electrolytic capacitor



Tantalum capacitor: Like electrolytic capacitors, tantalum capacitors are also polarised and offer a very high capacitance level for their volume. However this type of capacitor is very intolerant of being reverse biased, often exploding when placed under stress. This type of capacitor must also not be subject to high ripple currents or voltages above their working voltage. They are available in both leaded and surface mount formats. Read more about the tantalum capacitor



Silver Mica Capacitor: Silver mica capacitors are not as widely used these days, but they still offer very high levels of stability, low loss and accuracy where space is not an issue. They are primarily used for RF applications and and they are limited to maximum values of 1000 pF or so. Read more about the silver mica capacitor



Polystyrene Film Capacitor: Polystyrene capacitors are a relatively cheap form of capacitor but offer a close tolerance capacitor where needed. They are tubular in shape resulting from the fact that the plate / dielectric sandwich is rolled together, but this adds inductance limiting their frequency response to a few hundred kHz. They are generally only available as leaded electronics components.



Polyester Film Capacitor: Polyester film capacitors are used where cost is a consideration as they do not offer a high tolerance. Many polyester film capacitors have a tolerance of 5% or 10%, which is adequate for many applications. They are generally only available as leaded electronics components. Read more about the polyester capacitor



Metallised Polyester Film Capacitor: This type of capacitor is a essentially a form of polyester film capacitor where the polyester films themselves are metallised. The advantage of using this process is that because their electrodes are thin, the overall capacitor can be contained within a relatively small package. The metallised polyester film capacitors are generally only available as leaded electronics components.



Polycarbonate capacitor: The polycarbonate capacitors has been used in applications where reliability and performance are critical. The polycarbonate film is very stable and enables high tolerance capacitors to be made which will hold their capacitance value over time. In addition they have a low dissipation factor, and they remain stable over a wide temperature range, many being specified from -55°C to +125°C. However the manufacture of polycarbonate dielectric has ceased and their production is now very limited. Read more about the polycarbonate capacitor



Polypropylene Capacitor: The polypropylene capacitor is sometimes used when a higher tolerance type of capacitor is necessary than polyester capacitors offer. As the name implies, this capacitor uses a polypropylene film for the dielectric. One of the advantages of the capacitor is that there is very little change of capacitance with time and voltage applied. This type of capacitor is also used for low frequencies, with 100 kHz or so being the upper limit. They are generally only available as leaded electronics components. Read more about the polypropylene capacitor
Glass capacitors: As the name implies, this capacitor type uses glass as the dielectric. Although expensive, these capacitors offer very high levels or performance in terms of extremely low loss, high RF current capability, no piezo-electric noise and other features making them ideal for many performance RF applications.


So going by this info the polypropylene caps are high tolerance over a wide range of voltages and for low frec's.

For those of you who are still exploring this chip (TL594) and it's application to energy pumping, "Stay Tuned".

When this circuit is done we can all build it with confidence.

Mike

[Farmhand]

Hey Farmhand I am 56yrs

My desire to do more electronix has blossomed these past few years.

I use the far right hand terminal source to bring in the negative side of my cap bank so my red wire goes directly from the cap hot to the battery hot.

So I pulse the negative wire. Is this good?

Mike

I'm just a decade or so younger than you.

Yes it is good, low side switches are much simpler to drive.
Learning to drive high side switches well does open up a lot of other possibilities,
like two stage pulsers, capacitor voltage doublers, half and full H bridge switching solutions ect.

I'm very much a learner myself, and I enjoy learning new stuff so I'm happy to
be a learner. I'll review what I've missed lately.

..