Donald Smith Devices too good to be true

[soundiceuk]

The 5408 also have an "SF" version SF5408 it is also rate 1kv/3a/75ns.

Got to be 100ns

I have another question about the fixed capacitor c1-c2. The one I have under hand are ceramic disc (see the photo) They are quite smaller than the doorknob one I see in the photo of guys steup... Do you think they will do the job?

I'll find out if they will do for a proof of concept.

These are what one of the builders is using.

[tswift]

It might work, at least it's worth a try. The amount of ripple current through them is the problem, they will be subject to many charge/discharge cycles per second with every pulse of the PPV. If the gap breakdown voltage was the full 20KV rating of the cap I think you might have a problem with this, but running at a narrow gap width the breakdown voltage is probably more like 1000-1500V and I'm sure they can handle this. I tend to suspect that in the yet-to-be-seen future improvements of the device they will be operated closer to their voltage ratings and you might find them getting warm or failing entirely. But for now I would use them so it's one less part to spend money on.

[Wistiti]

Better scale image.

[Wistiti]

you could try the Ultrafast version of 1N5408, just replace "1N" with "UF". UF5408

http://www.vishay.com/docs/88756/uf5400.pdf

75 ns recovery time

I ordered a lot of these cut them short, connect by soldering and wrap them with teflon then electrical tape, put it inside a ballpen *case for extra protection and sturdiness and you will have UF high voltage diode with less leakage (its just going to be longer than the expensive ones.), but it works, this is what I use.

or maybe the low amp version of it. uf4007 (1kv 1A). these are more flexible and much easier to connect to form like a spiral, so it wont be that long (considering you have to connect 30 in series to achieve 30kv).

The 5408 also have an "SF" version SF5408 it is also rate 1kv/3a/75ns.



Thank you Soundiceuk for the reply on the pot. I have another question about the fixed capacitor c1-c2. The one I have under hand are ceramic disc (see the photo) They are quite smaller than the doorknob one I see in the photo of guys steup... Do you think they will do the job?

[ricards]

Ultrafast Diode

Yeah, if I had a bunch of 1N5408 diodes laying around it would be worth a try. Regular HV diodes internally are just a bunch of diodes in series, which is why they have a larger forward voltage drop than regular diodes. So it would probably end up acting a lot like the HVM-12 diodes I already have. I notice that the datasheet for the 1N5408 device only specifies characteristics at 60 Hz and doesn't specify reverse recovery time so it's certainly not an "ultrafast" or probably even a "fast" design or they would make a point of it. Doesn't mean it won't work but probably won't work well. Unfortunately there's really no substitute for true HV diodes that are also high speed. By the time you add "high voltage", "high speed" and "high current" into the mix, you get devices that are neither small nor cheap, I paid almost $4.00 each for the 100 mA 30KV 100ns diodes.

http://www.diodes.com/_files/datasheets/ds28007.pdf

you could try the Ultrafast version of 1N5408, just replace "1N" with "UF". UF5408

http://www.vishay.com/docs/88756/uf5400.pdf

75 ns recovery time

I ordered a lot of these cut them short, connect by soldering and wrap them with teflon then electrical tape, put it inside a ballpen *case for extra protection and sturdiness and you will have UF high voltage diode with less leakage (its just going to be longer than the expensive ones.), but it works, this is what I use.

or maybe the low amp version of it. uf4007 (1kv 1A). these are more flexible and much easier to connect to form like a spiral, so it wont be that long (considering you have to connect 30 in series to achieve 30kv).

[tswift]

I should have mentioned, I'm glad to know it's not just me having problems with the UX-FOB devices. They seemed like a good buy for the specs, an 8KV 500 mA diode for not insane money but they don't seem to work well in practice. I didn't know whether mine had just suffered from the various experiments I have put them through or whether it's the diodes themselves. I found a datasheet for them and they look OK on paper, 8KV, 0.5A, 40 ns. I have done some experiments where I got better results with the HVM-12 non-fast diodes even at 30 KHz or higher, so that made me suspicious. I would recommend other experimenters steer clear of them.

[tswift]

Yeah, if I had a bunch of 1N5408 diodes laying around it would be worth a try. Regular HV diodes internally are just a bunch of diodes in series, which is why they have a larger forward voltage drop than regular diodes. So it would probably end up acting a lot like the HVM-12 diodes I already have. I notice that the datasheet for the 1N5408 device only specifies characteristics at 60 Hz and doesn't specify reverse recovery time so it's certainly not an "ultrafast" or probably even a "fast" design or they would make a point of it. Doesn't mean it won't work but probably won't work well. Unfortunately there's really no substitute for true HV diodes that are also high speed. By the time you add "high voltage", "high speed" and "high current" into the mix, you get devices that are neither small nor cheap, I paid almost $4.00 each for the 100 mA 30KV 100ns diodes.

http://www.diodes.com/_files/datasheets/ds28007.pdf

[tesluh]

I haven't been having luck with ux-fob diodes working well either, or cl01-12, if you want something to try in the meantime while your china ones come in try 1n5408 https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

connected in series in a chain. cheap enough to see if they do what you need. I don't know the specs aside from what you see on the amazon ad.

[soundiceuk]

Well, at least part of my problem appears to be in the diodes. Those UX-FOB diodes I've been using are rated 8KV but they don't seem to be working right. I substituted the two diodes shown in the picture for a single HVM-12 standard recovery (non-ultrafast) microwave oven type diode and actually got around 3KV on the capacitor instead of 1KV. The "standard recovery" diodes don't actually say how fast or slow the reverse recovery time spec is, it could be fast enough to be useful but I have noticed before when using them that although they do give some rectification at 30+ KHz frequencies, they also get warm and I'm sure there is some reverse leakage during the recovery period every cycle.

So I'm stuck on progress until my diodes come in, I have some 30KV 100ns 100 mA diodes on order but coming from China (groan). Might be a week or more before I see them. I did receive my large spool of 40KV wire so I can begin building the coils for the next upgraded version in the meantime, doing calculations now.

Yes 100ma, 30KV, 100NS are perfect for D5.

[soundiceuk]

I noticed the mention of 2 grounds - has it been built and tested?

Yes, it has Dragon.

You know more than most people about using two hot spot earths and that it works.

You're probably one of the very few that knows already how to set up the earths too.

A counterpoise antenna will work too but which is a better option.

What we can't do is compare results from both antenna/ground, ground/ground in multiple locations around the world.

So here it is for replicators to try, if they wish to.

Mwtj, you could do a comparison test and see what works better and provide third party validation.

In theory it should work in low elevations.

That hasn't been tested.

Mwtj is in Holland and hasn't exactly got a high elevation, yet he got the circuit working with no insulators and lots of leakage.

[tswift]

Well, at least part of my problem appears to be in the diodes. Those UX-FOB diodes I've been using are rated 8KV but they don't seem to be working right. I substituted the two diodes shown in the picture for a single HVM-12 standard recovery (non-ultrafast) microwave oven type diode and actually got around 3KV on the capacitor instead of 1KV. The "standard recovery" diodes don't actually say how fast or slow the reverse recovery time spec is, it could be fast enough to be useful but I have noticed before when using them that although they do give some rectification at 30+ KHz frequencies, they also get warm and I'm sure there is some reverse leakage during the recovery period every cycle.

So I'm stuck on progress until my diodes come in, I have some 30KV 100ns 100 mA diodes on order but coming from China (groan). Might be a week or more before I see them. I did receive my large spool of 40KV wire so I can begin building the coils for the next upgraded version in the meantime, doing calculations now.

[dragon]

Very interesting Dragon!

Will research this.




Here is an extract of Bruce's latest PDF



This might be more favourable!

I noticed the mention of 2 grounds - has it been built and tested?

[soundiceuk]

hi guys!
do the 500k pot have to be a powerfull one or a small one is ok? What is the sugest watt for it?
Thank you!

No current flow in this part so take your pick!

500k potentiometer | eBay

Seems dearest one is 9 bucks!

[soundiceuk]

hi guys!
do the 500k pot have to be a powerfull one or a small one is ok? What is the sugest watt for it?
Thank you!

I'm looking into this. Will respond ASAP.

[soundiceuk]

Here is an antenna design that I purchased plans and tested years ago. Much simpler than stringing lots of wire in the air. At the time, I used a battery between ground and the cap connection to polarize the cap and was able to get 4-10 watts of energy periodically. It would run consistently in the range of 5 to 20 hz with varying degrees of output. Using a 2 in dia tube 8 ft long offers the same surface area as 500 ft of 20 ga wire.

With the HVM it might be enhanced to operate at higher frequencies... the trick might be in the balancing of power required to maintain the HVM and energy harvested by the system. As well, like Tswift is experiencing, controlling the "leaks"

Free High Voltage Energy From The Air (Downloadable Plans) - Information Unlimited

Just a thought from past experiences with HV harvesting...

Very interesting Dragon!

Will research this.




Here is an extract of Bruce's latest PDF



This might be more favourable!