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[2020-05-05 07:10:46] <guru3> Hmm, the frequency of the generated AC will also dip under generator load, so using the AC frequency to control the engine may have unintended consequences
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[2020-05-05 20:09:59] <Lucifer_arma> guru3: But detecting those dips is kinda the point
[2020-05-05 20:10:47] <Lucifer_arma> the electrical load on the generator gets translated to mechanical load through the alternator, so it is necessary when the electrical load increases to also throttle up to get the frequency back in line
[2020-05-05 20:11:39] <Lucifer_arma> likewise, when the electrical load drops, like when the a/c cycles off, at the current throttle position the engine will start to rev up, increasing the frequency of the generated AC
[2020-05-05 20:11:43] <Lucifer_arma> so I need to detect *that* and slow it down
[2020-05-05 20:11:43] <Lucifer_arma> ]ping
[2020-05-05 20:11:43] <ljrbot> pong
[2020-05-05 20:13:03] <Lucifer_arma> so, the generator in question generates 60hz AC at 1800rpm. So it generates one period every 30 turns of the crankshaft
[2020-05-05 20:13:11] <Lucifer_arma> right? I'm doing the math right?
[2020-05-05 20:13:17] <Lucifer_arma> ]math calc 1800/60
[2020-05-05 20:13:18] <ljrbot> Lucifer_arma: 30
[2020-05-05 20:14:45] <Lucifer_arma> so if I chop up the period into 30 equally spaced slices, I can get the crankshaft at TDC. So the angle of the AC wave has a correspondence to the crankshaft angle.
[2020-05-05 20:14:59] <Lucifer_arma> I need the crankshaft angle. :)
[2020-05-05 20:15:55] <Lucifer_arma> The generator uses a wasted spark configuration, and is a two cylinder. So when cylinder 1 is at TDC-compression, cylinder 2 is at TDC-intake. Both plugs fire, and cylinder one combusts, and cylinder two does nothing (but proceeds to start the intake stroke)
[2020-05-05 20:16:23] <Lucifer_arma> 360 degrees later, the two are opposite. #1 is at TDC-intake and #2 is at TDC-compression.
[2020-05-05 20:17:08] <Lucifer_arma> Logically, then, I can use one fuel injector in the throttle body, rather than two separate fuel injectors, and I can use the wasted spark idea with the fuel injector. By opening it at the same crankshaft angle every time, I will inject the correct amount of fuel into the manifold.
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[2020-05-05 20:18:17] <Lucifer_arma> So what I'm ultimately trying to calculate is when to open to fuel injector, and for how long to keep it open
[2020-05-05 20:19:02] <Lucifer_arma> And I'm looking at ways to measure the position of the crankshaft, because that tells me where the pistons are :)
[2020-05-05 20:19:48] <Lucifer_arma> I dug around and found a guy who "fixed" his generator's governor by simply letting it fail and putting an arduino in there. He used a laser sensor attached to the fan, which is driven by the crankshaft directly
[2020-05-05 20:20:31] <Lucifer_arma> The governor on the generator uses one of several ways to determine engine load mechanically and then opens/closes the throttle accordingly
[2020-05-05 20:21:14] <Lucifer_arma> So, I could use the same sort of laser sensor he used to get engine speed, but I'd have to do something physically to the fan to make one particular blade stand out, ideally the one that givens me TDC
[2020-05-05 20:21:39] <Lucifer_arma> that eliminates all the circuitry involved, anyway
[2020-05-05 20:22:21] <Lucifer_arma> so down the road, I'm looking at yanking the governor completely. The engine speeds on a generator can be regulated using the fuel/air mixture. The reason the throttle is used is because it's carburated.
[2020-05-05 20:22:58] <Lucifer_arma> But I want to move to an inverter model, where the generator revs between 1000 rpm (low, possibly even 800 rpm) up to about 3000 rpm.
[2020-05-05 20:23:26] <Lucifer_arma> That would boost the power output significantly, maybe turning a 4kw generator into a 7kw generator.
[2020-05-05 20:23:41] <Lucifer_arma> But you see what's happening. The AC output will range in both voltage and frequency.
[2020-05-05 20:24:49] <Lucifer_arma> So then I have to convert the output to a solid 15VDC, slap some schottkey diodes on the output (which would bring the voltage down to 14.something, which is fine), and feed it into a power inverter to get it back to a solid 120VAC 60hz signal
[2020-05-05 20:25:26] <Lucifer_arma> typically, the power losses in the inverter are more than offset by the gains in efficiency by being able to cycle up/down the generator to generate only the amount of power needed
[2020-05-05 20:26:06] <Lucifer_arma> so all of this leads to the questions that matter :)
[2020-05-05 20:27:02] <Lucifer_arma> 1. If I convert to fuel injection now, but run it as designed, how much fuel efficiency will I gain? This generator, by being a 4-pole generator and running at 1800rpm is already at/near its peak efficiency for a carburated system.
[2020-05-05 20:27:51] <Lucifer_arma> 2. Will it be worth the effort/money to convert it to an inverted system? I'd need power inverters starting in the 3-4k range, and then I'd need to stack inverters up to 8k to ensure that I can use all the power
[2020-05-05 20:29:00] <Lucifer_arma> The rest of the power system matters, too, though. There will be a large battery bank, preferably capable of running one AC unit for 10 hours (about 1.5kwh battery bank). The batteries will be/are 12VDC, because that's what the rest of the power system uses already
[2020-05-05 20:30:15] <Lucifer_arma> Solar panels for RVs are generally sold at 100W/panel, and there's enough room on the roof to fit 5-7 of those. In the winter, in a place like Texas, I could easily go days without turning on the generator
[2020-05-05 20:31:21] <Lucifer_arma> And those are just permanently mounted panels. If I'm boondocking, I could also have a storage bay with another 4-6 panels tucked away that I can take out and spread out.
[2020-05-05 20:32:03] <Lucifer_arma> So the advantage to moving to an inverter style generator is actually in the battery charging system, because I'd have to build a charging system that integrates the generator and solar panels and the alternator from the RV engine
[2020-05-05 20:32:43] <Lucifer_arma> as for what I'm going to do right now, I still need to find the slideout battery trays. I thought I'd determined they were in the generator bay, but then I put an actual generator in it and there's no room for batteries in there
[2020-05-05 20:33:24] <Lucifer_arma> and I need to put the carburator back on the generator, and find out in the process if it'll fit in the bay (I had to remove it because it made the generator too tall to slide through the opening
[2020-05-05 20:33:25] <Lucifer_arma> )
[2020-05-05 20:33:43] <Lucifer_arma> So, RVs aren't just for old people. They're also for nerds.
[2020-05-05 20:36:36] <Lucifer_arma> shit, I can't do rpm/hz. Duh.
[2020-05-05 20:38:03] <Lucifer_arma> ]math calc 1800/60
[2020-05-05 20:38:04] <ljrbot> Lucifer_arma: 30
[2020-05-05 20:38:51] <Lucifer_arma> so that's 30 rotations per second
[2020-05-05 20:39:39] <Lucifer_arma> so one rotation of the crankshaft results in two periods of the AC generated
[2020-05-05 20:43:26] <Lucifer_arma> so for 180 degrees of rotation on the crankshaft, I get one period of the AC wave form. So measuring the voltage doesn't give me one crankshaft position, it gives me two.
[2020-05-05 20:45:39] <Lucifer_arma> the fan sensor is the better choice, when looking at it like that. It's technically less accurate, but easier to work with.
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