Guru
Joined: 13/10/2014
Location: AustraliaPosts: 2282
| Posted: 10:45pm 03 Dec 2022 |
Most NEON globes strike at 90v (glow) they draw a few ma and an appropriate resistor is required in series, you can get then rated @ 240ac with the resistor installed in a small housing (around 240k resistor from memory) but the neon itself is about $1.25 or less, I think I used a 100k for this purpose. I have not shown the neon in my circuit and I will update that.
My version is almost exactly the same as the one you have, just modified to work as a base board, and plug in daughter board. It takes all of 4 seconds to remove the daughter board to modify and experiment with. I did this to virtually isolate the high voltage DC from the daughter board, I'm extra careful around these voltages due to my age and two recent heart attacks. That's why my cap bank is completely enclosed
. You don't have to worry about the cap discharge time, it is almost instantaneous when switching them across a low impedance load like a 12 to 24 ohm restive heater element.
There is a more complex arrangement happening here that is a mix of the thermal sink that the load is exposed to, like the heater element in water, and that changes with the temperature delta between the water in the tank and the element temperature, so the efficiency of that short pulse from the CAP bank is not static. Then you throw the Solar panel size and power curve into the mix and it's not just a simple switching time algorithm.
The Cap bank is not completely discharged in each cycle, the waveform across the caps swings between the upper voltage discharge point and the low voltage trip. In may case from 120v to 210v, so a 90 volts charge discharge cycle.
It's a simple matter of directly connecting the load and checking the current into the load verses the voltage under low solar conditions, in my case I found the low point of 125v @ 5.1 gave me 600 watts, below that the power dropped of rapidly. So having got my low switch point, the high discharge point is the max power point voltage, or a bit lower if it appears stop charging in half decent solar conditions.
So Charging time for the most part is pretty fast, but then you have the conundrum of how much cap is the sweet spot for the chosen load
I know various ideas have been talked about for measuring the real power delivered to the load with this type of controller. My plan now is to quickly code a small fast micro to simply measure the power flowing to the load with a power measurement taken ever few microseconds (or as fast as the code will run), this should show accumulated / averaged power per second, the idea is to get a fast running total displayed and hopefully get a pretty good idea of the real power to the load.
Apology for long post.
EDIT: I forgot to add: The idea of the micro measuring power is that it's very simple to then have the micro control/vary the switching to achieve the max power into the load under all conditions.
Mike.
Edited 2022-12-04 08:56 by KeepIS