EEVblog #469 - Cockcroft-Walton Multiplier

[EEVblog]

A new EEVblog segment, Fundamentals Friday!
How to generate high voltage DC with a Cockcroft-Walton Multiplier circuit.
a.k.a Cockcroft-Walton / Villard / Greinacher Cascade

[c4757p]

A new EEVblog segment, Fundamentals Friday!

Haven't even watched the video yet and it's already my favorite segment! FF sounds great.

[Chipguy]

I like that idea, but i have to say i like teardown tuesday the most.
More important, once there is a whole lot of fundametal fridays they will make a really really useful educational collection.
Thanks for the good work.

[JoannaK]

Like the explanation of the doubler circuit.

One thing you forgot to mention, is that those voltage doublers (with high volt input) can be quite nasty things. So testing them on low volts is really good idea for first timers.

Or, perhaps you could add second part, with real Hi-pot design and some nice sparks 

[firewalker]

 

Alexander.

[hammy]

Fundamentals Friday is a very good idea! 

[c4757p]

One thing you forgot to mention, is that those voltage doublers (with high volt input) can be quite nasty things. So testing them on low volts is really good idea for first timers.

If you can't figure out that a voltage "multiplier" will produce a higher voltage than what you put into it, you will not be able to figure out which of the little bits in front of you are the capacitors and which are the diodes...

[Skimask]

If you can't figure out that a voltage "multiplier" will produce a higher voltage than what you put into it, you will not be able to figure out which of the little bits in front of you are the capacitors and which are the diodes...

And possibly if the place you are in is yours or your neighbors...

[c4757p]

If you can't figure out that a voltage "multiplier" will produce a higher voltage than what you put into it, you will not be able to figure out which of the little bits in front of you are the capacitors and which are the diodes...

And possibly if the place you are in is yours or your neighbors...

Well, that could explain how you came to have the caps and diodes in the first place!

[pickle9000]

15 minutes long eh? (we always say eh? in Canada)

Well I suppose you couldn't help being jinxed by the doubler subject matter and the oversized whiteboard.

[TacticalCode]

Actually, I was hoping to see a section like this on your blog. Considering that this is a form of education, don't worry about the time. I wouldn't have wanted to watch this information squeezed into 10 minutes... You often said in previous blogs that something's function was a whole separate video, and I really hope you'll catch that up and explain some "fundamentals" in detail. This is really important (to me), as beginners will learn from that, it helps them to find a way into electronics and how things work.
On my personal blog, I published an article about how we educate people and why it is important to make it easy for everybody to learn something, and I got many mails with feedback - there is a huge need for this way of education. Free knowledge for the masses. So I'd actually appreciate if this section wasn't too off-the-cuff.

Thanks Dave, please keep up the good work.

[EEVblog]

15 minutes long eh? (we always say eh? in Canada)

Well, I did decide to chuck on the practical demo at the end.

[EEVblog]

Actually, I was hoping to see a section like this on your blog. Considering that this is a form of education, don't worry about the time. I wouldn't have wanted to watch this information squeezed into 10 minutes...

The time limit problem is at my end, not necessarily the viewer.
If I go into a video with the mindset that I will keep it deliberately (fairly) short, then it motivates me to actually do it. There is nothing worse than realising from the get-go that a video will end up being an hour long. That means several hours of actual footage, plus usually some practical aspect as well which takes time to setup etc.
For regular weekly videos I do not want to pressure of knowing that it will take me all day to shoot something.

[EEVblog]

So I'd actually appreciate if this section wasn't too off-the-cuff.

Sorry, I only do off-the-cuff!
T-Shirt slogan? 

[c4757p]

Sorry, I only do off-the-cuff!
T-Shirt slogan? 

I've always liked that about EEVblog, but if you're going to do instructional segments like that, you need to be very careful about precision of terminology, etc. Things like suddenly realizing "oh, I should use peak-to-peak voltage instead of just peak" halfway through an explanation will confuse people.

[Skimask]

Finished watching this video less than an hour ago.
Had (notice the usage of the word HAD) a need for a quick/dirty method to trickle charge a 4 cell AAA NiMH pack off the USB port.

20 minutes, 1 BAV99S diode array, 1 4x .1uf SMT cap array, 2 resistors (current limit at the USB port and current limit at the battery pack), a microUSB connector, and a dead-bug layout later, I got a decent ~6v output for the NiMH pack that doesn't piss off the USB port when I plug it in.

Is it a fast charge?  No, doesn't need to be.
Is it clean?  Nope, doesn't need to be.
Is it quick, dirty, cheap, small?  Yep...meets every one of those requirements.

[c4757p]

Huh? Unless you left something out of that list, where's the AC coming from?

[EEVblog]

I've always liked that about EEVblog, but if you're going to do instructional segments like that, you need to be very careful about precision of terminology, etc. Things like suddenly realizing "oh, I should use peak-to-peak voltage instead of just peak" halfway through an explanation will confuse people.

Yeah, but that's the way I work.
I a) don't really know exactly what I will say until I hit record, and b) I don't review every segment after I shoot it.
So often I don't realise I've said something wrong or not clear until I go to edit it. And even then, I often miss it because I either don't watch the entire segment, or I simply don't notice because it's my work. (Which is why proofreading your own work doesn't work). I also do not watch the final video in it's entirety before I upload.
So yes, I can try to be a bit more careful, but ultimately, there will always be a good chance of things I miss, get wrong, or don't explain.
In this case I realised peak may have been confusing, but it wasn't really worth going back and reshooting that. And I also added a test annotation overlay in editing to clarify a point.

[nathanpc]

Loved the new segment. Looking forward to the next episode!

[Skimask]

Huh? Unless you left something out of that list, where's the AC coming from?

DOH!  Sure did.
Circuit has a PIC with a spare pin for some easy PWM, a 2N7000 MOSFET, and just added a 10uf bulk cap across the V+ from the USB which really smoothed out the output a bunch.
I'm happy.  Sure, it'll take literally days (4+ according to my calc's) to charge a dead 4 cell AAA NiMH batt pack, but that wasn't the point.

[Orpheus]

Love the idea of Fundamental Fridays. It doesn't matter how you do them, JUST DO THEM!

The details? that's what comments and the Web are for.\, once you're clued in and fired up.

I've been meaning to fiddle with diode ladders for, oh, 35 years now, at least. Never got around to it. So this example had special meaning for me. Maybe I'll even be motivated to try it myself now!

[Shale]

Actually, I was hoping to see a section like this on your blog. Considering that this is a form of education, don't worry about the time. I wouldn't have wanted to watch this information squeezed into 10 minutes... You often said in previous blogs that something's function was a whole separate video, and I really hope you'll catch that up and explain some "fundamentals" in detail. This is really important (to me), as beginners will learn from that, it helps them to find a way into electronics and how things work.

Thanks Dave, please keep up the good work.

I really like the new addition to the blog. This is already going to be my favorite part.

[owlhawk]

Great new segment! As interesting as test equipment reviews may be, the videos on actual electronic design are my favorite part of the show. I look forward to seeing more of that each week now.

[Flsgd]

As an ECE student struggling on electronics seeing it put so matter-of-fact gives me hopes!

Keep this a thing, Dave!

Thanks!

[Strada916]

Love the FF Segment. Keep it up.