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Forum Index : Electronics : Inverter building using Wiseguys Power board and the Nano drive board
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| GleamBright Regular Member  Joined: 21/04/2025 Location: AustraliaPosts: 43 |
Referring to KeepIS' post on page 8 of this thread re: removal of diode and capacitor from nano board rear side. I received two slightly different nano designs, one of which I (think) I've identifed the diode and capacitor. The other one at the top is less clear. Anyone want to have a stab at identifying the relevant diode and capacitor? Soon to attempt firmware downloads ahead of commencing the build.  |
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KeepIS Guru  Joined: 13/10/2014 Location: AustraliaPosts: 2259 |
EDIT: Made an Error with the two boards shown There are two types of the SECOND board, one does not allow you to disable the +5V supply, and it looks like that is the board in the photo. Sooo! the second board is NOT correct. However removing that CAP does disable the Nano reset problem (checked), use it for the LCD displays or for poidas Saturation tester. Just out of interest, I extracted the +5V pin on the USB socket and that obviously solves the +5V problem (same as removing a diode), but it's not feasible for most. A final thought, in my inverter I have a small adaptor cable from the USB socket on the Nano to the Cabinet front panel for a tablet or PC if a Menu Setting needs to be adjusted. You could simply disconnect the +5v wire in that lead, if you had a few of those boards that would at least solve that problem. The First Board? I don't have one exactly like that? The Cap and Diode can be in very odd places on some boards. Measure from the reset pin to the cap, one side should be connected to the reset pin. Removing the Cap at least removes the reset issue. As a refresh: 1: The Diode isolates the USB external +5V from the Nano controller. 2: Cap removal stops the USB Port from resetting the Nano controller on port connection and when connecting to a Serial program for setting the Menu options. : Edited 2026-09-04 14:37 by KeepIS NANO:Inverter V 8.4ks - Linux AvrDude GUI script V4.1 |
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| KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 2259 |
Corrected previous post, slight difference in the boards that I missed the first time I replied  NANO:Inverter V 8.4ks - Linux AvrDude GUI script V4.1 |
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| analog8484 Senior Member  Joined: 11/11/2021 Location: United StatesPosts: 222 |
A bit surprised to see the Vds overshoot. Don't remember it to be quite as large in your past builds. Wonder if it affects the gate drive waveforms. Is this really unloaded? That's quite a bit of ringing for unloaded. Nice to see the beads really work. |
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| KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 2259 |
Like I said in the post, worst case I could find, it depends on exactly where in the waveform you zoom into, again, this is a test setup without the massive capacitance of a LiFePO4 battery, and no 0-gauge or 00-gauge cables, just 15A resistive connections to the DC supply, the ESR of these test caps are not as good as the 120000uF CAP Bank sitting across the supply in the Main Inverter. Most times, ringing in the test unit is just those normally short, fast decaying 2 to 3 cycles apparent in some parts of the SPWM envelope. Random captures from 2023.   : Edited 2026-09-06 13:59 by KeepIS NANO:Inverter V 8.4ks - Linux AvrDude GUI script V4.1 |
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| Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1252 |
@keepIS, how do you ensure the transformer core doesn't get a DC magnetic bias on it over time; for even with absolutely symmetrical switching on each 1/2 cycle, differences in the timing of mosfet drivers and the mosfet on resistance can cause an imbalance; this can build up over time, causing the transformer to start making unusual noises as it slowly saturates. Just interested as I'm making an inverter to drive our large sewerage pump. Cheers Mike |
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| KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 2259 |
FYI: After correcting the 1/2 Sine array: The result around Zero Crossing. Old Code: Versions Version 8.2 and earlier. Optional Dual Version 1.5 and earlier:  Corrected Code: Version 8.4, Optional Dual Version 1.7.  NANO:Inverter V 8.4ks - Linux AvrDude GUI script V4.1 |
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| KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 2259 |
I've never seen that happen in the Inverter. That is a rabbit hole I've seen engineers go down, but usually on large installations. I reason that if Major manufactures can getaway with a design that uses a compromised smallish Toroid with 1.5 to 1.7 Telsa and a crap design, then I should not have an issue with a big Toroid wound closer to 1 Telsa. As you likely know, I have spent countless months monitoring the Inverter running our property. We start Large workshop equipment with big heavy Induction motors on top of the normal home loads (all electric), I was constantly recording startup and running currents with the DSO and a logger, any core saturation over time would have been recorded or shown up, it has never happened, this includes daily loading with something close to DC injection via a Heat Gun with heat switch using a dam Diode in one side of the Inverter AC supply. The Inverter has run uninterrupted for 12 months at a time, powering the property and workshop at up to 14.3kW continuous output and surge DC Input currents above 30kW, and no soft ramp-up or ramp-down to reset the Toroid flux for over 12 months. The Toroids run virtually silent under all load currents, with the exception of a Hair dryer with Diode across the AC taking a bite out of one half of the AC cycle. A very subdued buzz is heard, that's all. That info may not be of any help at all, but it's all I have. I would add that the Inverter sits 3 meters behind me in a very quite part of the workshop, and except for the slight diode heat switch buzz, not a peep from it, can't even remember the last time the Toroid Fans come on. NANO:Inverter V 8.4ks - Linux AvrDude GUI script V4.1 |
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| Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1252 |
That's excellent, your design works extremely well, so hopefully I won't have to worry too much about that, but will make future provision in the software to detect and compensate should it occur. Was planning to add a few turns around the core as an isolated AC sample, then pass to an OP Amp integrator with 2.5v zero reference, if both halves of the AC wave are identical the output is 2.5v, any flux imbalance and the result output will be + or - with respect to 2.5v, CPU can then use this data to bias the spwm slightly to bring the output back to 2.5v. Are you using edge centered spwm or center aligned spwm in your design?. |
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| analog8484 Senior Member Joined: 11/11/2021 Location: United StatesPosts: 222 |
Good point about the caps. Perhaps that's why there are DC bus snubbers in some designs. |
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| analog8484 Senior Member Joined: 11/11/2021 Location: United StatesPosts: 222 |
Poida would probably know best. But I remember it uses "Fast PWM" when I looked at the code a while back which suggests it's left aligned PWM pulses. |
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| KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 2259 |
That method of trying to overcome flux imbalance had been discussed and implemented, and the last time I looked at the subject, most simple attempts usually created more problems. To me, it's a solution looking for a problem that does not appear to be a issue in an isolated off grid Inverter. As you know, the code that generates SPWM output in the Nano Hardware was written and designed by the forum member Poida. The code I wrote is based around his Nano SPWM Generation Code. My off grid situation exposes the Inverter to extremely rapid, high, short duration currents, and long periods of high power demand, or both together, conditions not normally encountered with most basic Off-Grid power setups. I had specific Error Trip conditions and Inverter control conditions that I needed to implement for these loads, I wrote the code needed to accomplish these around a massaged version of Poidas SPWM scheme, and all built around wiseguys Inverter hardware designs and his SPWM Symmetry drive, which poida merged into the SPWM drive code. As for the purposeful implementation of any SPWM alignment methodology by Poida in his SPWM CODE, for a single phase off-grid Nano controller?? I doubt the hardware timing or need would be there. Obviously you could PM him for his thought process, or perhaps poida can correct me here, which would be fine. : Edited 2026-09-07 10:41 by KeepIS NANO:Inverter V 8.4ks - Linux AvrDude GUI script V4.1 |
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| nickskethisniks Guru Joined: 17/10/2017 Location: BelgiumPosts: 487 |
I actually don't use them for improving the thermal transfer but more for the more robust isolation, so I didnt do any testing on that matter. Yes you still need to use some kind of grease. |
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| nickskethisniks Guru Joined: 17/10/2017 Location: BelgiumPosts: 487 |
The ringing will allways be there, switching is done so fast this is inevatable. A year ago I did A LOT of testing and it was frustrating attempting to reduce ringing. I used more then 10 different beads, resistors,caps, etc.. but it was difficult to keep myself to the same protocol and document everything on a structered way and then do a write up over here, I had good results but lack of time and other priorities. Hats off Keepis to share so much value over here! I did some testing with H bridges and only low value inductors as load, so energy is circulating and current become verry high without a big power supply. This gave interesting repeatable results. Low value inductors gave really nasty ringing (low di/dt?), this is why that series inductor we use is one of the most important components in the system. A first protecting layer for the mosfets. The beads are the only thing I tested that completely removed the ringing BUT with the side effect of introducing one big spike that gets higher with higher current. And that raises the question if higher voltage mosfets should be chosen to coop with that, allthough the energy of the spike is verry low and keepis his inverters don't seem to have problems after 1-2y of testing, only time will tell if this is allso after 10-15y. Putting some resistors over the beads, this somewhat reduced the spikes with a few volts but not really worth the trouble. On the other hand ( and maybe my preference) using snubbers will allso dramatically reduce the ringing without that big spike introduction. Just 1 or 2 1uf mkp capcitors soldered directly on the powerboard (power bus) did lower the amplitude of the ringing, then a combination of 10R and 2.2nF on the ac output or 4 individual over the ds legs did finish the job. I will try to post some scoop pictures later, I have populated some boards. Edited 2026-09-07 18:56 by nickskethisniks |
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| analog8484 Senior Member Joined: 11/11/2021 Location: United StatesPosts: 222 |
If only for isolation, did you consider alumina ceramic pads? They are much cheaper but the thermal conductivity is not nearly as good. |
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| analog8484 Senior Member Joined: 11/11/2021 Location: United StatesPosts: 222 |
It would be interesting to see scope captures showing the effects of different snubber components. Did you also try higher gate resistor values? |
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