An energy harvesting project

[JulesP]

Hi Rodolphe,

Good to see your progress on the build. I hope the diagnostics section I presented in the manual was helpful in getting things set up and checked in a straightforward manner.

Regarding your swapper LED, there is not enough power to operate it and start the chip counting so it is probably not going to be a problem. If SW2 is not isolating properly then some leftover charge, stored in C6 (1,000uF) and which, if you look at the attached schematic, feeds the input to SW2, and could be getting through. Disconnect the center wire on the switch and see if that stops it. Or you can try shorting out C6 after switching off the whole circuit and seeing what happens. If not then, as you say, it must be some leakage within the chip, but it is not likely to be of any consequence. When using my cap dump circuit, I often get the power on LED dimly lit for a while as some small power leakage is finding its way through to it when the PSU is on.



From memory, my little cap adjustment inside the voltage divider didn’t do much either but the adjustment on the cable feed to the scope channel did so I was able to get nice square waves using that.

However, if you are going to use the voltage divider then you will need to calibrate it against an ‘impulse’ signal from a signal generator and not a square wave. The 5V impulse signal I used is far more like the spikes you will be measuring. Super accuracy here is not required since the divider is just to give confirmation of the peak HV and which should be similar to the avalanche rating of the device.

There is no reason why you can’t use your 2000V probe. The conventional power in the spikes is small as there is hardly any ‘hot current, a fact demonstrated by the fact that the small relays are passing the HV spikes through to the correct battery with no problem or damage.

J

[pearldragon]

Hi Julian,

Testing/Startup
This weekend I started with testing components and sub-systems; went pretty ok, see image below. Swapper works. One thing that I noted was that when SW2 is OFF (swap on/off), LED3 (swap on) was still lit very faintly… I measured the voltage over R11 (10k), this was 0.12V. (9.6V when SW 2 is in the ON position). So either that switch is not completely disconnecting in the off position, or U1 (CD4060 unit) is leaking from somewhere a bit.
(White tape indications will be replaced with stickers further down the road)


Voltage divider
Furthermore I put a +/-2V 1kHz square wave signal from my scope on the voltage divider and used the probe from the same scope to compensate/tune the radius-ed edge of the square wave output with the trimmer, but to no avail: in the screenshot below you see the signals with the trimmer in both extreme positions, 8.9pF & 57pF. Any idea what might be the cause? Before using the voltage divider I did calibrate the probe itself with the same square wave signal (but without the voltage divider in between).
I disconnected the trimmer to double check if it didn't burn out in the soldering process (very tiny and sensitive thing ), but it was working properly and connected it again.

Another thing I realized is that I do have an additional set of HV probes, with a ratio of 100:1. My question is; could I use on of those probes directly, or would the energy in the spike be too much and damage it? https://eleshop.eu/owon-oscilloscope-probes-2kv.html

Best regards,
Rodolphe

[JulesP]

Hi Rodolphe,

The highest inductance will be with Ferrite rods.

I had reason to contact Devan so he is on the look out for an email from you so try again. He might find your previous ones but write anyway saying what you need.

Tests so far are indicating the best voltage for cap dumps in actually much lower around 20V but tests are not complete. In a few weeks I might have a more complete picture.

J

[pearldragon]

Hi Julian,

I find it 273mH versus 370mH i find still quite a difference. I will machine the rods I have here to size when I have time, but it won't hold me back of continuing finishing the setup and move in the direction of starting the test (subcomponents of the) system.
If anything, having the option of testing with different inductances might be an other interesting variable to test with: dV/dT of the HV spike. With the rods machines to size I will then have 3 options: air coil, welding rods, ferrite rods.

I haven't tried to contact the supplier again yet since currently there are no components I still neede although in saying that; i do not have the STW12N170K5 Mosfet yet... I might shoot them another mail and let you know if I get a response.

Regards,
Rodolphe

[JulesP]

Rodolphe, Your inductance and resistance readings are similar to what I got (14Ohms, 368mH) Of course when the coils are in parallel then the total values will change.

Did you manage to try the quote form for the ‘hard to get’ component place? If all else fails I can suggest another place.

Julian

[pearldragon]

Hi Julian,

Quick update regarding the coils:
-Resistance (individual): +/-14 Ohm
-Inductance (individual) without any core material: 62.5mH
-Inductance (individual) with core material*: 273.5mH

*The Ferrite rods I ordered from Aliexpress are slightly too big, so stacked 1 coil with welding rod material, see picture (material: R45-G / DIN: 8554: G1 / w.nr 1.0324)
Will put the ferrite rods on a lathe and turn them down to fit and remeasure.

Measured with: LC100-A Digital LCD High Precision Inductance capacitance L/C Meter (aliexpress)

Regards,
Rodolphe

[pearldragon]

Hi Julian,

Thanks for all your clear and elaborate answers.

Yes, my coils will be on a separate base plate, I’ll post some pictures when it is done, but first will finish the main base plate/circuit connections.

For the accurate current measurements, I’ve bought the digital multimeter you used; Owen XDM1041, it already has a dust layer on it, since I haven’t used it yet .

Nice to hear how you’re progressing/plan to progress, good luck with it and keep us informed here on the forum!

Best regards,
Rodolphe

[JulesP]

Hi Rodolphe,

Your build has come along very nicely and with its own unique base design. I’m sure you’re pleased.

Re your questions:

PRF meter: Yes you can simply run a wire under the unit between the two GNDs for that to work. When I ran with the rotor I used the external meter a lot but when using solid-state then I tend to rely on the PWM display, but it's good to have some confirmation.

PWM module: If you look at the attached graphic, which shows my setup of both the two small meters and the PWM module on the same panel, you will see the ground connection next to the signal output. However, I found it was not necessary to wire that one up and the output signal was fine without it. If you scope it and find the signal a bit ‘noisy’ then a link wire between the V- and the Gnd will probably improve it but so far I have not found it necessary.

Also shown there is the series current connection for the two meters, coming from the fuses, through both meters, and then off to the Ground return to the PCB.



Volt/Amp meters: As shown above, the meters are both in series with the negative line that is being switched. While it may be possible to wire them up with separate negative lines it would offer no advantage. The voltage feeds are ‘individual’ for obvious reasons but the same current will be passing through both hence the present arrangement.

Bear in mind that these small meters are not accurate and should not be used for readings during testing. In fact, the current that shows would only show on one of the meters, the other reading zero while the two separate voltages would show. They can be calibrated using small adjustment pots on their circuits but they don’t hold well across a range. They serve as an indicator rather than for accurate measurements.

For accurate current measurements, you should place a decent meter between the positive terminal of the supply battery and the positive connection to the PCB, as indicated below. If you place the meter on the negative side it might be influenced by currents flowing to and from battery 2 so it’s best to have it in a dedicated position. Of course, this only works when Batt 1 is the supply, which is the way I have it, and Batt 2 is the one being charged and monitored by the CBA. When swapping is happening then, for the stage when batt 1 is being charged, I can use a clamp meter on batt 2 but its reading should be the same since nothing is changing on the circuit and coil side.




Soldering: With the multi-strand wire, when it is inserted and removed repeatedly into the terminal blocks then it would start to get messy so I used solder to hold all the strands together and would usually flatten the soldered end with pliers and trim its length so it would fit easily into the blocks. Whatever works for you but the terminal blocks do not offer an opening big enough to take many other types of connectors.

When you have connected and disconnected all the wires to the PCB multiple times you get to find out what works best for you to maintain the integrity of the wire end.

With the mini switches I used, instead of the rockers type you are using, the switch terminals were too small to use with spade connectors or similar. They are best suited to solder connections, as are the small pads on the underside of the PCB.

. . . .

I assume your coils are on a separate base to connect to your PCB coil terminals?

If it turns out that a cap dump unit is required for optimum operation then that could be on another small base. I have made a few hard-wire mods to the v4 PCB to work with a cap dump unit and will of course provide details of those if, as, and when needed, as indeed for the cap dump unit itself.

I am gearing up to start my various capacitor configurations testing and am awaiting some 1,000 uF 200V capacitors. My 53,000uF bank will only work up to 80V and my new ‘multi-voltage’ cap dump design will go up to 140V.

I have had to use 'Devan' again for some hard-to-get components. Finding a local source of 150V P channel FETs is impossible at the moment, but he has plenty. My original supply was of poor quality and all but one have failed at the moment so I have my second stage prototype installed, which is using just one FET and which will do the main task. The photo shows the breadboard to first prototype stages. I can’t have automated swapping until I have the other two installed but there is a whole heap of testing I can do without battery swapping so no rush there.

[pearldragon]

Hi Julian,

Finally got the amp/volt meters in which enabled me to finalize the base plate and continued building see picture below.
I have a couple of (layman) questions/double checks which I hope you can help me with regarding connecting the components.
Unless stated otherwise my questions relate to the electrical diagram on page 1 of your manual.

PRF meter
1) I have 4 connections; 2 for the power supply (+ and GND), and 2 for the signal (IN and GND), is it correct that I can connect the two ground (GND) connections together (since in this case the power supply is not a separate system from the system to be measured)?

PWM module
2) I have 4 connections; 2 for the power supply (V+ and V-), and 2 for the signal (PWM and GND). For now I left the GND connection open/not connected. But same question as above; could I connect the V- to the GND?

Volt/Amp meters
3) Why does the amp meter part (of the combined volt/amp meter) of both the meters have a common line to both the negatives of the batteries? -> Why are they not in the individual lines of the batteries (before they join together in the “T”, before the main switch?

Soldering
4a) In the beginning of the manual you propose to solder the ends of wires instead of letting them stranded (for the screw terminal connections). Any particular reason for that?
4b) To connected the wires from the PCB to the rocker switches and the fuse box, you used soldered connections. Any particular reason for this instead of using terminal connectors/plugs?

Thanks in advance,
Best regards,
Rodolphe

[pearldragon]

Hi Julian,
I soldered the terminal blocks in the holes for the diodes en put the diodes in the terminal blocks for easy swapping, see image below.

As you can see in the close up image, I used a different socket for H25 as i described in an earlier post. Reason: the contacts in the socket mentioned in the manual did not make well enough contact to my taste with the Mosfet contacts prongs.

[JulesP]

Good stuff. Have you added some extra connector blocks alongside each of the output diodes? Is that so you can try different diodes easily? Using just one IN5408 instead of three made a small difference also but not as much as using an SC diode.

[pearldragon]

Hi Julian,
finished th voltage dividerr this weekend and continued on the PCB. Anticipating that the SD diodes would potentially give an increase (as you described in your post above). I used the terminals there as well so i can easily swap between diodes D3, D4, D5).

[JulesP]

Following on from my experimenting with a single Silicon Carbide Diode (C3D06065A), instead of my original three parallel IN5408 diodes (see pic), I have found about a 15 - 20% increase in CoP values across a selection of batteries. This will be useful for future testing.



After a very constructive discussion with Geoffrey Miller, there are a few tweaks I will be making to my experimental procedure with regard to load tests using the HV pulses alone. My earlier suggestion that the battery being charged does not have time to assimilate the energy input before it is called upon to be a supply, seems to be the right view and so I will be incorporating a 60 min rest time into my swapping. As such I am going to call this 'punctuated swapping' and where the 60 min rest period will not show on the monitoring graph as I will pause the monitoring during the rest phase. Let's see if the original CoP results bear more fruit if it is given a chance to manifest.


Regarding my various 'Cap dump' developments, the attached shows the various configurations I will be exploring over the coming months to see what delivers the best results. What I refer to in them as the 'router' and the 'relay' in C and D, are now built as modular add-on circuits, and the revised design of the main cap dump unit, to accommodate discharge voltages up to 120V, is also now complete and due back from JCLPCB. It will be built as a test version to check the various adjustment to all the various biasings for the various BJTs and P-channel FETs. The aim is to allow a wide range of discharge voltages for experimentation and then, if one particular one or configuration stands out, I can issue a PCB design for those who would like to use it. Similarly with the router and relay.

I think spring is making an appearance - now the clocks have gone forward it ruddy well ought to!

Julian

[pearldragon]

Hi Julian,

Just got back from holiday. Will have another look at the DVD soon and let you know if some more of his comments/details about the HV pulses.
Most of the components came in, still waiting for the the volt/ampere displays, which are holding me back of ordering/finalizing design of the base plate. Picture below is work in progress. Main thing I'm battling at the moment is time .

Best regards,
Rodolphe

[JulesP]

Hi Rodolphe,

That’s interesting and I wonder if it’s because of the reason I suggested, that there isn’t time to process the radiant energy in electrochemical terms. Does JB give any further details as to why?

What I have shown is marginal so I’m hoping the use of the cap dump system will give much clearer results.

Other researchers are using the mechanical output of the primary load (rotary switching system) to drive a normal type of generator to produce regular ’hot’ electricity. Presumably they use the HV pulses to run a cap dump system as well to feed back to the batteries.

Another major issue is around the impedance of the system and the convenience of using SLA batteries, Lead Acid or Lithium, is more than offset by their high internal resistance. A typical 7Ah battery will be around 200-300mOhms compared to a fluid filed car type battery of 20-30mOhms. One is far more likely to see radiant effects with the latter which I will soon be examining.

Yes, in due course I will be trying to run a load off the battery being charged using both HV and cap dump pulses.

Lots of variations to try, which is far better than hitting a dead end!

J