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That Works posted:Awesome thanks! One more thing to note, that battery you have is very much capable of dumping a whole lotta amps into a dead short (I'm amazed your multimeter didn't fry or blow a fuse honestly). Not enough to dramatically explode your meter or anything, but definitely enough to blow up thin wires or heat up thick wires to the point where they start a fire, just keep that in mind. I think you mentioned you had a fuse in line with the battery already so I wouldn't worry about it in normal operation, just watch out if you're fiddling with it y'know. BalloonFish posted:I know this is all Electrical Devices 101, but as someone who thinks he doesn't understand electricity I'm very pleased that I've managed to replace my generator's oil light Congrats, it's always a nice feeling to repair something yourself 
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May 14, 2020 20:43
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Sagebrush posted:also resistors don't slow the current down; it always travels at the speed of light (+/-). resistors change how many electrons go through per time interval. the water analogy is okay for the most basic explanations of electricity but you really can't make any deeper assumptions based on how water works in pipes because electricity is not water in a pipe Changes in electric field propagate through a conductor at or near the speed of light but the drift velocity of electrons in a conductor is very slow. https://en.wikipedia.org/wiki/Drift_velocity Drift velocity is proportional to the conductivity of the conductor, so it is inversely proportional to the resistivity of the conductor and therefore slower in higher resistances, assuming the same length and cross section of conductor. However, "slowing electrons down" is not why we care about resistors; I'm not sure that drift velocity ever really matters in circuit analysis. BattleMaster fucked around with this message at 20:55 on May 14, 2020 |
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May 14, 2020 20:49
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BattleMaster posted:Changes in electric field propagate through a conductor at or near the speed of light but the drift velocity of electrons in a conductor is very slow. That's always been one of the weirdest things about electricity to me, electrons are actually real fuckin' lazy and barely move at all. Or I guess they're more clumsy than lazy since they're slow due to constantly bumping into stuff.
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May 14, 2020 20:55
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BattleMaster posted:Changes in electric field propagate through a conductor at or near the speed of light but the drift velocity of electrons in a conductor is very slow. Yeah, when students start asking me about "so how does the battery store all the electrons" or whatever I try to impress on them that a conductive wire is more like a garden hose full of marbles than a hollow pipe. You don't have a stream of electrons shooting out of the wall and running through your computer and going back to the power plant. Just another way that the water analogy falls apart. I suppose I could have been more clear and specified that current measures how much charge goes by per unit time, while the electrons themselves just kinda sit and spin, but you always gotta find this balance between accuracy and clarity. Which model is the appropriate one to teach students at this point in their learning? It seems like physics classes from elementary school through at least first-year university are just an endless chain of "okay, the stuff we taught you last year -- that's not actually how it works. The real way is --" only to have that new model also invalidated the next year.  Reminds me of that Feynman video where they ask him about magnets. Sagebrush fucked around with this message at 21:06 on May 14, 2020 |
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May 14, 2020 21:01
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Shame Boy posted:That's always been one of the weirdest things about electricity to me, electrons are actually real fuckin' lazy and barely move at all. Not that weird. It's like you've got a big metal poking stick. You push on one end, the other end moves basically at the same time even though the stick as a whole doesn't move that fast.
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May 14, 2020 21:23
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Sagebrush posted:You don't have a stream of electrons shooting out of the wall and running through your computer and going back to the power plant. Just another way that the water analogy falls apart. Your wall socket (or well, the power plant) is like two pistons full of water that alternate going in and out, transferring energy while not actually giving or taking any net water  Foxfire_ posted:Not that weird. It's like you've got a big metal poking stick. You push on one end, the other end moves basically at the same time even though the stick as a whole doesn't move that fast. Oh yeah I get it, it's just they go real fast in a vacuum if they're not bumping into atoms, so it's kinda amazing how much slower they go in even very good conductors, and how little that actually matters.
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May 14, 2020 21:31
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Chakan posted:We received multiple echo dots over the past few years from the same uncle of mine who just forgot. I managed to get rid of two, but now I've got a third. I was cleaning the other day and found it, so it's either going in the bin or I'm re-purposing it. The boards don't seem very useful, and I couldn't find anything about wiping them anyway, so I was thinking about just using the case for something as a novelty. Does anyone have any ideas or help? Looking at the dimensions it's a little small for even the smaller raspberry pi's but I'm not very familiar with microcontrollers in general so maybe there's something that works in a similar vein. Is this even the right thread? I think your post got lost in the other chat but I wanted to say, while I don't have any suggestions on projects, there's plenty of teeny tiny dev boards that would fit in an echo dot case and offer a ton of performance if you need it, like the Teensy: https://www.pjrc.com/store/teensy40.html
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May 14, 2020 21:35
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BattleMaster posted:Changes in electric field propagate through a conductor at or near the speed of light but the drift velocity of electrons in a conductor is very slow. Wow, I've never calculated or seen somebody calculate the drift velocity in a metal wire. The number in the linked wikipedia page, 23 um/s, is slow! Max drift velocity in a silicon field effect transistor is faster--I see numbers that are > 1 km/s. I think the micro-scopic reason for the speed differential is that silicon, being a semi-conductor, has a lower density of electrons which contribute to electricity conduction, even when turned on via the Field Effect, so the electrons don't collide with each other as much. I think also the fact that silicon is almost chemically and structurally a perfect crystal helps improve the speed. edit: I just watched the Richard Feynman magnet video Sagebrush mentioned. I've never heard him talk before. His intensity, high pitched voice, and New York accent reminded me a lot of that one scene with Joe Pesci's character in Goodfellas. silence_kit fucked around with this message at 22:16 on May 14, 2020 |
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May 14, 2020 21:46
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That 23um/s example is for 1A of current in 2mm diameter copper. Silicon saturation velocities are km/s, but those are when increasing voltage stops making electrons faster. That doesn't happen until there's tens of kV on it. That much voltage will make the copper electrons much zippier too.
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May 14, 2020 22:49
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Foxfire_ posted:That 23um/s example is for 1A of current in 2mm diameter copper. Silicon saturation velocities are km/s, but those are when increasing voltage stops making electrons faster. That doesn't happen until there's tens of kV on it. That much voltage will make the copper electrons much zippier too. Oh that makes sense, I'm making a comparison between a low electric field velocity to a high electric field velocity. Tens of kV per centimeter, you mean. Still, it could be argued that it isn't a horrible comparison even though I attribute the bulk of difference to the wrong thing--the field strengths in a transistor usually tend to be high while the field strengths in a wire usually tend to be low.
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May 14, 2020 23:58
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Sagebrush posted:Just another way that the water analogy falls apart. The water analogy works pretty well here too, though! Think of electron drift velocity as the fluid velocity and the speed of light in the medium as the speed of sound in the fluid. We could, say, take a large pipe and drill tiny holes into it, and cap one end and attach the other end to a valve whose other side is attached to a constant pressure liquid source. Say a huge reservoir at a fixed water level. Ambient atmospheric pressure is like ground potential and the tiny holes function as high resistances to ground. The valve functions as a switch. The pipe leaks down to atmospheric pressure. You close the switch/open the valve. The diameter of the pipe is much larger than the holes so there's no appreciable displacement of the fluid inside, but the tiny holes all start spurting water, first near the valve then further from it. You can even watch the pressure wave propagate through the pipe much like you can watch an EM wave propagate through a transmission line, complete with reflections. It's me. The hydraulic analogy defender has logged on. I just like having electrical analogies for mechanical systems. "Hydraulic ram pumps and boost converters work the same way" is an important realization to have at the right point in the development of your understanding of either. I'll grant there are electrical things impossible to explain with elegant hydraulic things. Magnetics other than water-hammer-as-inductance are a great example. Also almost everything about water flowing in pipes is more complicated than electrical analogies. Don't design your plumbing in SPICE or you might think you can suck water up to the 20th floor instead if pumping it up and accidentally build a barometer.
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May 15, 2020 00:33
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Shame Boy posted:I think your post got lost in the other chat but I wanted to say, while I don't have any suggestions on projects, there's plenty of teeny tiny dev boards that would fit in an echo dot case and offer a ton of performance if you need it, like the Teensy: https://www.pjrc.com/store/teensy40.html Thanks! I'll take a look.
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May 15, 2020 00:37
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Stack Machine posted:The water analogy works pretty well here too, though! Think of electron drift velocity as the fluid velocity and the speed of light in the medium as the speed of sound in the fluid. We could, say, take a large pipe and drill tiny holes into it, and cap one end and attach the other end to a valve whose other side is attached to a constant pressure liquid source. Say a huge reservoir at a fixed water level. I'm not really that mechanically inclined, so sometimes I try to understand mechanical things by using electrical analogies. I don't know if the following is correct, but in my head, a car's transmission is just a tunable impedance matching circuit from the engine to the car's wheels. The 'impedance' (~= torque / rotation rate) the car's wheels present to the engine is almost like an open circuit at rest, and so the transmission needs to transform the engine's natural impedance level where it is able to deliver the most power to the wheels to a higher one to match the car's wheels. This is first gear. As the car gets moving, the car wheels' rotation rate goes up, and so the transmission needs to transform the car engine's impedance level to a lower impedance level than before for a better match. This is like the higher gears in a transmission.
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May 15, 2020 01:21
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If you get an electron going fast enough in a conductor or semiconductor will they emit x-rays?
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May 15, 2020 01:26
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The electron needs to be free and accelerated to a pretty high velocity before it will produce anything near x-ray. Most x-ray sources use bremstrahlung braking to shed a photon. This requires free electrons and a vacuum to achieve. The lower energies start at 5-10kV.
um excuse me fucked around with this message at 01:37 on May 15, 2020 |
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May 15, 2020 01:34
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silence_kit posted:I'm not really that mechanically inclined, so sometimes I try to understand mechanical things by using electrical analogies. I don't know if the following is correct, but in my head, a car's transmission is just a tunable impedance matching circuit from the engine to the car's wheels. This is valid as well. Torque is the equivalent of voltage and rotational speed current. Gear ratios are like Vout/Vin for a DC-DC converter. The caveat when discussing mechanisms, though, is the circuit node. The only thing I can think of that obeys the equivalent of Kirchoff's current law is a differential. Having 2 components connected to a node is like having a shaft going straight through. A single shaft with multiple springs/brakes/etc is like a series circuit. (Flywheels are inductors! Vanes with air resistance linear in rotational speed are resistors. ratchets are diodes. Clock springs are capacitors!) If you want to connect more than one component to a node you'll need a differential, like the one on the rear wheels of a car. Having one wheel start spinning is like shorting the output of your power supply and having the voltage drop to zero and the current go to its limit until the short is removed. A cruise control in this analogy is a constant current regulator. The car is like one hell of an inductive load, too. You'd dump a lot of energy as arcing if you were to just open the circuit up all of a sudden. Stack Machine fucked around with this message at 02:43 on May 15, 2020 |
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May 15, 2020 02:24
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^^^ Also an RC circuit is the same as a spring and damper system I got myself a de10-nano because it looked like a fun FPGA platform to play with and since it's used by MiSTer I expect it to be supported at least by the community for a long time. Also if nothing else it runs MiSTer. Since the add-on boards are not very complicated and open source, I decided to just make them myself. Ordered 5 each of the IO board and the dual-chip 4 layer 128MB SDRAM board from JLCPCB but the 32MB board looked simple enough that I'm going to have a go at etching it myself while I wait for the others. Also the 32MB chip is a Winbond W9825G6KH and only costs ~$2 so I figured it would be handy to have on hand for other projects anyway. Anyway, I don't have a ton of experience with highish speed boards so just wanted to check if I'm crazy or not. I attached a picture of the gerber, left to right is top, bottom, combined. My plan is to just point to point wire the top since I only have single sided PCBs but I'm not 100% clear on the reason for the little island in the middle. My assessment is that it's just for convenience of wiring up stuff since the perimeter simply encloses all the pads that need Vdd. The outer bit is ground. Does that sound about right? Not sure if it does some EMI function as well is why I ask. This is a 3.3V chip, I believe it runs at up to 133MHz for the MiSTer. Forseti fucked around with this message at 02:35 on May 15, 2020 |
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May 15, 2020 02:29
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If I'm understanding what you're saying, you're going to: - Have no copper at all on the bottom - Duplicate all the connections that were done by the bottom copper with discrete wire ? It will be noisier and may or may not work. For EMI, you want to minimize the loop area that current flows around. Return high frequency current will more or less want to follow as closely as possible to the outgoing current. Like if the entire bottom of the board was a ground plane, the return current for a trace will follow the trace's path across the ground plane. If you force it across a bigger path (cut up ground plane usually, discrete wire here), the loop area increases and it will both radiate and receive more.
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May 15, 2020 03:45
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Forseti posted:My plan is to just point to point wire the top since I only have single sided PCBs but I'm not 100% clear on the reason for the little island in the middle. My assessment is that it's just for convenience of wiring up stuff since the perimeter simply encloses all the pads that need Vdd. The outer bit is ground. Does that sound about right? Not sure if it does some EMI function as well is why I ask. This is a 3.3V chip, I believe it runs at up to 133MHz for the MiSTer. That's a power plane and is likely there just because it's considered a PCB best practice. Having planes for your supplies instead of just routes is great for a number of reasons. Inductance in series with a power supply is bad because you don't want current spikes on clock edges to cause your supply to dip. Capacitance on supplies is good for the same reason. Planes have less parasitic inductance and more parasitic capacitance than point to point routes. The planes also serve to, in combination with the routes over them, form a relatively controlled-characteristic-impedance transmission line and give the routes more capacitance to ground (or any supply. A cap to anything DC looks identical electrically to a cap to ground if the supplies are stable) than to each other. This reduces cross-talk by making the bottom side of the effective capacitive voltage divider large.
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May 15, 2020 04:04
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Pretty much, I know to avoid multiple loops, so the plan was just connect each thing that needs a ground directly to a whatever grounded pin on the header in a straight line instead of chaining them together for instance. Just full confession my degree is in Computer Science, so I'm used to working in the magical realm of ideal behavior. Edit: I'll give it a try, somehow this monstrosity works so I should be good  https://www.youtube.com/watch?v=HILEYKIFixw Forseti fucked around with this message at 04:15 on May 15, 2020 |
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May 15, 2020 04:10
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I'd be surprised if you had much trouble. Star topology on your grounds/supplies keeps inductance low too and as long as you place the decoupling caps near the power pin you're golden for that. That does mean caps should go on the same leg of the star as the IC they're decoupling though.
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May 15, 2020 04:45
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Next part of the project. 20A PWM solar charge controller https://www.windynation.com/Charge-...1319?p=YzE9MTc= 100W solar panel https://smile.amazon.com/gp/product/B01HHDC6NQ/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1 Panel is overkill, but I may scale this up to a larger battery to power a small water heater in the winter to keep an insulated water bottle inside the coop just above freezing. That and maybe I'll use it for other projects later on or something.  Per the instructions I inlined a 30A fuse between the + lead from the panel to the charge controller. Ok so here's the questions / concerns I am having. 1. Is there a recommended / better way to connect to those odd solar panel wire plugs? Or do I just buy a set of M/F plugs and wire them up to a short run and connect that to the controller? I managed to connect jumper wires to each using some small M bullet connector crimp ons but I imagine this isn't probably ideal longer term. 2. Suggestions / criticism on splicing connections from the battery. Battery terminals are just spade clips (on the bottom of the battery in the photo). I made short jumpers to eye fittings that I bolted through then used the nut and bolt to attach new eye fittings to that have short wires to spade clips for other 12v output. These are all taped down so they don't move into contact and short out and once everything is connected I was going to fashion a cover for the + side wiring entirely. If this is all woefully bad please let me know. 3. The coop itself is in a shady area under trees. During the winter it gets direct sun but now through November it's no good. So, the panel will need to be set up either on my deck or on a small brick pad in the backyard. Both are about 20-30' from the coop. So, I need to run some wiring. The plan I'm thinking right now is to build a plywood stand large enough to accommodate the battery (or a much larger one), and a place to mount the charge controller with the appropriate spacing and ventilation for this and the battery. The top of this box will be cut at a 41 degree angle for optimum panel position oriented S at my latitude. So the panel acts as a roof for the structure. 4. Wiring from the panel-battery-controller stand to the coop. I was thinking of wiring the 12v leads into a female 110v type socket and using an exterior rated extension cord and running that out to the coop. In the coop would be a 110v male plug that fits to the extension cord and this would be split to apply 12V to the linear actuator and to the Buck converter which would connect to the Pi via USB cable. Is wiring it this way a bad idea? Just thinking of how to use stuff I already have or have easy access to that are cheap and can be set up in a way easy to keep weather proof. Up suffering from insomnia, sorry if this is less than clear.
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May 15, 2020 08:14
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That Works posted:4. Wiring from the panel-battery-controller stand to the coop. I was thinking of wiring the 12v leads into a female 110v type socket and using an exterior rated extension cord and running that out to the coop. In the coop would be a 110v male plug that fits to the extension cord and this would be split to apply 12V to the linear actuator and to the Buck converter which would connect to the Pi via USB cable. Is wiring it this way a bad idea? Just thinking of how to use stuff I already have or have easy access to that are cheap and can be set up in a way easy to keep weather proof. Bulkhead fittings: https://smile.amazon.com/dp/B07V6NJ37P/ Extension cables: https://smile.amazon.com/dp/B07Z7T494M/ Etc.
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May 15, 2020 15:26
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Don't do it just to prevent the future That Works from plugging 120V into their 12V somehow.
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May 15, 2020 15:41
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If you have a 100W panel you might be able to get away with just sticking it in the shade where it's convenient since it seems like you won't need anywhere near that much power. What are you running with it? Is it just the Pi and then maybe a solenoid or two firing occasionally? The Pi doesn't take much power anyway but if it isn't doing a whole lot you can even under clock it to save power I believe.
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May 15, 2020 15:44
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sharkytm posted:Don't do this. 120VAC cords are for 120VAC Also if you start running 12v lines a long distance you will rapidly discover what Tesla was on about back in the 1890s. Power transmitted is the product of current and voltage, P = V*I So if you need to carry 480 watts you can do that with 480v * 1A, or 120v * 4A, or 12v * 40A, or any combination that multiplies to give 480W. However, the power dissipated in a resistive load (like a wire) is the product of resistance and the square of the current, P = R*I2. This means that your resistive losses go up exponentially with current flow, and thus the lower the voltage (for a given load) the less efficient it is. 14ga house wire has a resistance of about 3 ohms per 1000 feet. Let's say you have a 100 foot run to your chicken coop. That is 200 feet in the circuit and thus about 0.6 ohms total. Doesn't sound too bad. But if we compare the 120v circuit to the 12v circuit, (120v) P = R*I2 = 0.6*42 = 0.6*16 = 9.6W. Not bad, in transmitting 480W you've lost only 2% to wire resistance. (12v) P = R*I2 = 0.6*402 = 0.6*1600 = 960W oops. In your attempt to transmit 480W at 12v you've dissipated twice as much power in the wire as the load itself draws. If you do a little more math you can also work out how much heat you'll get from attempting to shove 40 amps down a 14ga wire. Your solutions are (a) replace the wire with a thicker, heavier cable that has lower resistance, which is simple but wasteful and expensive, or (b) transmit the power at high voltage and low current, requiring a transformer at one or both ends but being vastly more efficient. This is why high-tension lines are high-tension (tension being an old term for voltage -- it's not about the mechanical tension in the wires) and run at hundreds of thousands of volts. That lets them transmit megawatts of power with relatively small amounts of current, reducing transmission losses as much as possible. e: oh I see that you have actual figures we can work with. At 30 feet away and using a 100W solar panel and 14ga wire, you're losing 12.5 watts at 12v and 0.25 watts at 120v. The numbers there aren't as bad but you decide whether you care about the difference between 87% efficiency and 99% efficiency. Sagebrush fucked around with this message at 16:22 on May 15, 2020 |
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May 15, 2020 16:13
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Sagebrush posted:At 30 feet away and using a 100W solar panel and 14ga wire, you're losing 12.5 watts at 12v I don't think that's right. At 3 ohms per 1000 ft, that'd be 0.003 ohms per foot, 0.09 ohms per 30ft. 100W at 12V is ~8.33A, I2R of that gives me only 6.25W of loss. e: I was initially off by a factor of 10 too but stealth-edited it so
Shame Boy fucked around with this message at 16:41 on May 15, 2020 |
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May 15, 2020 16:39
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Solar powered cable heater
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May 15, 2020 16:41
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Shame Boy posted:I don't think that's right. At 3 ohms per 1000 ft, that'd be 0.003 ohms per foot, 0.09 ohms per 30ft. 100W at 12V is ~8.33A, I2R of that gives me only 6.25W of loss. Wouldn't it be 60 feet, though, since you have the same current on both the upstream and downstream legs and thus resistive losses both ways?
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May 15, 2020 17:02
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Sagebrush posted:Wouldn't it be 60 feet, though, since you have the same current on both the upstream and downstream legs and thus resistive losses both ways? Oh you want the current to be able to go back too? Well aren't we needy today (Yeah ok )
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May 15, 2020 17:05
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sharkytm posted:Don't do this. 120VAC cords are for 120VAC. There are low-voltage connectors widely available that will meet your needs. For example: the SAE 2-pin connector used on battery chargers: https://smile.amazon.com/dp/B01N4B3RPH/ and similar products. Thank you! Part of the process for me right now is just figuring out what is even available on top of how all of it works. Forseti posted:If you have a 100W panel you might be able to get away with just sticking it in the shade where it's convenient since it seems like you won't need anywhere near that much power. What are you running with it? Is it just the Pi and then maybe a solenoid or two firing occasionally? The Pi doesn't take much power anyway but if it isn't doing a whole lot you can even under clock it to save power I believe. That was a near term plan and might be good enough? During the summer I only need to run the Pi, a temperature sensor and 2-3 times a day firing off the linear actuator to open and close the coop door. During the winter if possible / feasible I'd like to power a small heater in an insulated water container to keep from it from freezing. I have not yet begun to look into heating elements and what kind of current that would draw, etc. If it's not feasible I can just power that off 110VAC from the house instead. The upside in the winter is that the coop becomes more sunny again once the leaves go, so efficiency might come up a bit although the daytime gets substantially shorter (I am in coastal RI). I might just try this 1st since it involves the least amount of new materials and I can just let it run in place and see how battery charge looks after a while. Sagebrush posted:e: snip - informative math and facts Would there be any benefit to having the battery and charge controller at the coop and having the panel stand-alone 25-30' away and wired directly from there to the charge controller? E: maybe using something like this? https://smile.amazon.com/BougeRV-Extension-Female-Connector-Adaptor/dp/B07BRFPD6R And, with step ups to higher voltage don't I start generating more heat? (not sure if its enough to be an issue) Any products / resources etc to consider if I was going to go with step-up and step down transformers? Not sure what is commercially available, a cursory glance shows a few that go from 12 to 48V which I am not sure would be a big enough gain in efficiency to be worth the trouble / cost. Thanks again all for your help. I am starting from very little knowledge here so its a huge help to have the advice. That Works fucked around with this message at 18:19 on May 15, 2020 |
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May 15, 2020 18:16
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taqueso posted:Don't do it just to prevent the future That Works from plugging 120V into their 12V somehow. Never  That's a good point, if not me then some errant houseguest or something in the future tries to "help" and causes a problem.
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May 15, 2020 18:17
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Depending on how much you care about doing things correctly/safely/durably, you should ask in the wiring thread. This thread is mostly ersatz electrical engineers, not electricians. They're related fields, but mostly only know enough about each other to confidently do things wrong. How to build infrastructure wiring and connections in a way that is safe/cheap/durable/doesn't-invalidate-insurance-if-there-is-a-fire is a whole field and it's easy to do things that work, but past experience has shown to be bad and are forbidden by code. Some specific things that I think are wrong from your pictures (but don't know enough to be sure): - The tape and terminal block isn't a good way to connect stuff since there's exposed live surfaces and generic electrical tape adhesive doesn't last. There are a bunch of approved ways to do a splice, I think wire nuts are probably easiest. - That wire doesn't look like it's supposed to be run outside of a chassis or conduit. You can get armored cable with wear+weather resistant jacketing or pvc flex conduit.
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May 15, 2020 18:58
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Foxfire_ posted:Depending on how much you care about doing things correctly/safely/durably, you should ask in the wiring thread. This thread is mostly ersatz electrical engineers, not electricians. They're related fields, but mostly only know enough about each other to confidently do things wrong. Thanks! Yeah this for now is just getting things tested with what I've got on hand or can get cheaply. I was not aware of the other thread / differences between the two. The final system will almost certainly have a bigger battery etc and the stuff connecting to the coop I was planning on running in flex conduit according to our code but need to double check that. Got the Black and Decker wiring guide / electrical codes for 2020 here to go through as well. Thankfully the entire system is standalone well distanced from the house so in the case of absolute catastrophe we'd be cooking some chickens sooner than planned. Once I kind of get my head around how everything fits and will it even work in the space it's for then I wanted to nail down safest practices for wiring, minimizing risk of fire in the coop, etc.
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May 15, 2020 19:08
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I'm gonna check in with the wiring thread as suggested but was wondering if anyone had any input on solar panel operation in a shaded area as I continue to try and figure out if I want to have the panels just on the coop or mounted 32' away on a more sunny area. The 12V, 100W panel I got https://smile.amazon.com/gp/product/B01HHDC6NQ/ref=ppx_yo_dt_b_search_asin_title At 8am in total shadow on a partly cloudy day it's producing 6.1W *Based on measured 18V, 0.339A Users of this panel have reported up to 15W in shade. I'll see how it looks in full shade at solar noon. Average sun hours for this region are 4.23 per day. If I estimate 8W average over 4.23h that gives me 33.8 Wh expected *0.7 to assume I am only 70% efficient with wiring etc leaves me with 27 Wh per day. So looking at load estimation: Spring / Summer / Fall: ~30 Wh per day load (Raspberry Pi zeroW running wifi, temp sensor, 2-3 cycles per day on the linear actuator) being very generous with estimated power consumption here. Not gonna go into Winter stuff yet, gotta work out water heating stuff, problem for another day. So it's a little under what I'd need to run the panel in shade, but I think I am overestimating inefficiency here and also overestimating power consumption. Likewise the 8W average panel output is a lower end estimate as this is in total shade. Right now I'm leaning towards installing the panel on the coop roof (angled properly) and having the battery and controller etc directly below in a sealed and vented enclosure. What do yall think? At this point I'd rather get an extra panel vs a distant run since it'll probably be helpful for Winter usage (keep coop water from freezing). If that setup works I'll figure out how to safely wire it all up. That Works fucked around with this message at 14:06 on May 16, 2020 |
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May 16, 2020 13:56
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That Works posted:At 8am in total shadow on a partly cloudy day it's producing 6.1W *Based on measured 18V, 0.339A
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May 16, 2020 14:24
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FYI, I just got my Zero W yesterday and it draws about 80mA with wifi connected and idle, maybe up to 200 with the CPU and wifi chugging at full tilt. You could probably go lower if you downclock it but 10Wh for the Pi/day should be plenty. No idea about the actuators or heating of course.
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May 16, 2020 14:38
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evil_bunnY posted:How did you measure this? You have an mppt solar controller? 20A PWM controller I measured V directly off the panel leads and mA from the + panel lead to the + input of the PWM controller. Did I screw up something again? e: while the PWM was charging the battery.
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May 16, 2020 14:39
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That Works posted:e: while the PWM was charging the battery.
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May 16, 2020 15:11
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| # ? May 9, 2024 06:23 |
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What is the best way to measure a solar panel anyway? I tested out a 6W one I got for peanuts off a promotion yesterday out of curiosity by wiring the panel directly to a 600F supercap and measuring the voltage on the cap. So for example I measured on the capacitor a start V of 31.7mV at 14:14:15 and an end V of 62.0mV at 14:17:20. So I calculated code:Edit: had the start and end backwards in the calculation Edit2: Looked up the cap, my memory is way off, ESR is more like 2.6 mOhm. Datasheet Forseti fucked around with this message at 17:27 on May 16, 2020 |
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May 16, 2020 17:22
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