An energy harvesting project

[pearldragon]

I would be ok with uploading a parts list for the forthcoming PCB within the next week if anyone wants a head start on that issue.

You can count me amongst the 'anyone's' . I'm guessing that only the diodes and the mosfets were a bit harder to get and the other components on the list are available from the at least one of the regular component suppliers (farnell, RS, mouser, etc)? So I could place an order with Jinftry this week already just for the the diode and mosfet?

Regards,
Rodolphe

[JulesP]

The DHG1011800PA diodes were easily got from Aliexpress for about 7 Pounds for 10pcs with delivery. For the FETs try the attached.

[Ron Hammar]

Hi all, I have a need for help. I was reading on one of the forum were there was a link of a video of a patent about using water as a fuel by heating it up, The USPTO #3,939,814. Can any one recall reading about it? It dealt with heating up water over 1000*F and it caused it to cause the H2O to separate and the H2 burned off so the water being injected into the chamber keep the temp high so the action would keep on heating. I think the posting was some time ago. Thank you for any help in this. Ron

[JulesP]

Hi Ron,

This is probably not the right thread for this discussion but while you’re here I will share what I can.

I’m not aware of any process whereby water is heated first before some process maintains the heat flow. Given water’s large specific heat capacity (due to its ‘peculiar’ bonding) there must be a substantial amount of energy pit in first to reach that state.

The only valid process I’m aware of for using water as a fuel is that developed by Walt Jenkins in Florida whereby high voltages are applied to water in a way that results in vacuum energy entering the system via, rather than from, the water. This has yet to prove itself to the scientific community but he has acquired patents for it all over the world so it must have some technical merit to jump those hurdles.

For a physicists treatment of this there is Moray King’s book: Water as Fuel’ that looks at the science and then there is Walt’s site at:
https://cyberstreme.wixsite.com/mysite
which gives a fair amount of info.

Before Covid they had planned to run a bus right across America using just water but that was paused due to the pandemic and I haven’t heard yet whether that is going to be undertaken soon.

Sorry not to be more helpful re your enquiry, but at least I’m referring to the same substance!

Jules

[pearldragon]

Hi Julian,

The DHG1011800PA diodes were easily got from Aliexpress for about 7 Pounds for 10pcs with delivery. For the FETs try the attached.

I had a look already there and saw that they were available, but thought that buying them from Aliexpress would be risking buying 'dodgy' components as you warned me for in the cap dump thread and better left as a last option. The screenshot/link also seems a Chinese company. What was your consideration buying them there rather than from jinftry? (I just had another look at the reply from Jinftry and realize/see now they also are a chinese company).

I saw that jinftry cannot not supply the DHG1011800PA, but can supply the DSEI 12-12A. In case I want to use the STW12N150K5 or STW12N170K5: instead of a DHG1011800PA, I assume I could also put two DSEI 12-12A in series? or is there a particular reason why I should not (apart from the fact that your PCB probably does not accommodate for it).

P.S. I just see that I have some C4D02120A* diodes here already, could I use them instead of the DSEI 12-12A? I see that the DSEI have a higher current rating, but unsure if that high a current rating is necessary if it is just to ground the voltage peak during switching on of the mosfet?

*Spec sheet C4D02120A: https://cdn-reichelt.de/documents/da.../C4D02120A.pdf
Spec sheet DSEI 12-12A for comparison: https://cdn-reichelt.de/documents/da...12-12A_IXY.pdf

Best Regards,
Rodolphe

[JulesP]

You don’t need a high current rating and the DSEI12 will not work with the 150 or 170 as it will breakdown at a lower voltage than those with the spike we want, on FET shutoff.


I have never used two diodes in series so don’t know how that would work. If that diode breaks down at 1200V max then I’m not sure that two in series will manage 2400V. As you say the PCB is set for one device at that point.

The Ali express ones I got are fine and work well. Yes it’s possible to get duff devices but these are good ones. Visit the following link on AliExpress: https://a.aliexpress.com/_EI3y3L7

The dodgy device I had was a comparator from a UK source.

When I post the component list for the ‘replication’ PCB I will indicate in some cases exactly where I got them from. In many cases, like with resistors, they should be ok from just about any source.

Jules

[pearldragon]

Hi Julian,

I ordered the 1800V diodes from the Aliexpress link you posted, thanks: I figured for the money they cost there I shouldn't doubt and just buy them.

I did a RFQ for the 1800V diodes and the 1700V & 1500V mosfets at jhykjic.com (from proper manufacturers). I'll see what they come back with. Jinftry could supply the 1500V mosfets, but not the 1700V versions. If jhykjic.com can't either, I'll just go for the1500V versions.

I ordered the (semi) automatic coil winder from my post #11.

Thanks for all the quick replies.

Best regards,
Rodolphe

[pearldragon]

Hi Julian,

I’m watching some youtube video’s about mosfets (switching). In the following YT movie @52 sec, it shows the mosfets with an already built in diode to protect against/ground the spike during the switching on of the mosfet. Which is further shown in the Vds and Vgs Graphs @3min: only a spike during switch off.
If I open the specsheet of one of the mosfets you named in your documents/we’ve been discussing here, I also see that diode: https://www.st.com/resource/en/datas...tw12n170k5.pdf

So my question is:
Is this built-in diode not already doing the grounding job, where you intended the DSEI-12-12A/DHG10i1800PA for?

Best regards,
Rodolphe

[JulesP]

Hi Rodolphe,

I’m not an electrical engineer but my understanding on this is that all MOSFETs have an internal, also called body or parasitic diode, by virtue of the PN junctions that are part of their innate structure. This is shown within the symbol for the FET on the right hand side (see pic).

The role of the body diode is to allow a current path to ground during the period between switching on and off to release the charge collecting at the junction and is particularly relevant when switching inductive loads. However, they have a slow response time that can cause a significant build-up of charge at the junction and with associated problems, depending on the circuit you have and the application.

Adding an external fast recovery diode, thereby shunting the body diode in parallel, will release that charge more effectively than the indigenous body diode and usually prevent the body diode from ever having to switch on.

For regular power switching, where you don’t want the flyback pulses appearing at the Drain and causing problems (EMI etc) then often another diode is used to discharge the ‘damaging’ pulse and which the body diode can’t do since it's being reversed biased.

Alternatively, many of these active devices have an 'avalanche rating' whereby over a certain voltage they break down to discharge the pulse to ground, This is shown in the other graphic. This latter feature is the limiting factor in the peak flyback pulse voltage as I have mentioned elsewhere.

Of course, we do want this pulse so we don’t add an additional, above-mentioned diode across the inductor to discharge it to the battery (as is shown in this video: https://youtu.be/6YOctFtOuwY). Please note that this video does not make reference to the spike that results from the coil switch-on but focuses on the one at switch-off.

You might reasonably ask why we don’t do that as the pulse will still arrive at the battery. I believe the key answer here is that shunting the coils with a diode would prevent the spike voltage from building up to the 1-2kV that we do see and want and instead clamp it at a low value, along with a small amount of current. This is a very different result from delivering a high potential pulse directly to the battery terminal which is what we need to elicit the ‘phenomenon’ at the interface of the pulse and the electrochemistry.

So instead we let the voltage spike exist as a pure voltage potential delivered to the battery terminal instead of using an additional diode across the coil, as shown in the video, which would inevitably change the type, quality and magnitude of the pulse arriving at the battery.

However, we are still limited by the FETs avalanche rating and, if the FET we use didn’t have such a rating, then it would be easily damaged by the very pulses we seek to use.

So to summarise, an external FRED, Schottky or another type, is added to support the discharge of the pulse energy generated during the FET on duration and which would otherwise build up as charge at the Drain-Source PN junction. This is due to the slow response of the body diode, which is not optimised for this role, and is not there from a deliberate design choice but on account of the way the device is constructed.

I hope that gives you some clarity.

Jules

PS. I'm busy writing the assembly manual and so will be limiting my responses on here for the next month or so.

[pearldragon]

Hi Julian,

The role of the body diode is to allow a current path to ground during the period between switching on and off to release the charge collecting at the junction and is particularly relevant when switching inductive loads. However, they have a slow response time that can cause a significant build-up of charge at the junction and with associated problems, depending on the circuit you have and the application.

Adding an external fast recovery diode, thereby shunting the body diode in parallel, will release that charge more effectively than the indigenous body diode and usually prevent the body diode from ever having to switch on.

This is all very clear how you explained it. Thanks.

Of course, we do want this pulse so we don’t add an additional, above-mentioned diode across the inductor to discharge it to the battery

I understand what you mean, but the sentence looks/reads a bit strange to me, what I expected you to say was: Of course we do want this pulse, so we don’t add an additional, above-mentioned diode across the inductor. Without this diode the pulse discharges to the battery.
But again, I understood what you meant.

Please note that this video does not make reference to the spike that results from the coil switch-on but focuses on the one at switch-off.

Well exactly that confused me a bit, that put me on the track that the built in diode was already performing the function of the external diode in your circuit, but all is cleared up with your explanation.

But the following thought crossed my mind:
By grounding this ‘switching-on-pulse’, we are wasting it… could the circuit not be constructed that we catch this pulse too? Since it is in the reverse direction, I guess we would need a capacitor for it first and when voltage has risen high enough, dump it to the battery -> so a cap dump circuit after all . But only to catch the switch on spike.

PS. I'm busy writing the assembly manual and so will be limiting my responses on here for the next month or so.

No worries, I might post some more questions here, but please don’t feel any pressure to respond to them quickly. And maybe Gary will be able to help out too.

Best regards,
Rodolphe

[JulesP]

But the following thought crossed my mind:
By grounding this ‘switching-on-pulse’, we are wasting it… could the circuit not be constructed that we catch this pulse too? Since it is in the reverse direction, I guess we would need a capacitor for it first and when voltage has risen high enough, dump it to the battery -> so a cap dump circuit after all . But only to catch the switch on spike.

The answer to your question is addressed by the doc ' Report - Cap Dump Circuit' in the docs folder.

The new PCB v4 has arrived and the test/check build will start in the next week

[pearldragon]

Hi Julian,

The answer to your question is addressed by the doc ' Report - Cap Dump Circuit' in the docs folder.

I assume you refer to the document “Interim Report – Battery charging vs CDF (Oscillator)”? I read through it but could only find reference to catching the HV spike when switching OFF the mosfet, but no reference to use a cap dump circuit to catch the switching ON spike.

In other words, the HV spike when switching the mosfet OFF would still go directly to the battery, while the spike when switching the mosfet ON would first be caught by a capacitor and then dumped to the battery. So both spikes would be used, instead of only one. For an (over) simplified sketch of catching the switch ON spike, see attachment.

PCB looks very nice Julian! Curious to hear how it performs.

Best regards,
Rodolphe
Attachment.pdf

[pearldragon]

Small update/info for those who want to build Julian’s setup as well and considering where to buy the mosfet and diode. This is my experience so far:

Jinftry:
Quick and friendly with replies, but sending parts via DHL cost about 50Euro/USD, so mainly an interesting option for bigger orders.

Jinghongyang electronics technology (post #17):
I’ve sent them several inquiries, but they never replied

Aliexpress/eBay:
Seem quickest and cheapest options.

Regards,
Rodolphe

[JulesP]

I have attached grabs from two docs in the folder indicating that delivering cap dump type pulses to the battery did very little and would required another circuit. The contribution to CoP from such would not be noticed next to that from direct HV pulsing. It would be like adding 1 to 20 and wondering if having 21 is worth the extra effort and expense.

Some of these chips are hard to come by. If I find other suppliers I will post them, especially if they are cheaper to deliver. AliExpress etc can be good for many things but I haven’t found any of the 150/170k5 IGBTs on there so far.

[JulesP]

While I’m posting here is the components list for the new v4 PCB.