 This is a super quick tutorial showing you how to build a liquid rear stat, which is a variable resistor for load testing Turbines and other kinds of generators. This one's just going to be using water and washing soda It's a dollar's worth of materials. You can make it in about five minutes, basically I'm going to be using this to test my winter turbine prototype and my water turbine prototype Basically, a liquid rear stat is just a variable load It lets you set how much resistance you're putting on your generator, which then determines how much of like an amperage load is being put on it And you can then plot your power curve to try to find where your volts times your amps is the most amount of watts, essentially. You can also use light bulbs of various kinds, a classic choice, although they have certain issues such as like their resistance can change if they heat up And also they're quite discreet, like you plug in a light bulb, you get that much more load Whereas this one is like purely analog, you can set it across, you know, basically infinite points between your high and low resistance It's super easy to build, like about 10 minutes, about a dollar's worth of materials or so So liquid rear stats are quite an old-school Victorian era kind of like solution to this kind of problem Traditionally, they were mostly, very large, for one thing, this one's quite small They used sodium chloride and water, traditionally, usually That's also an option. We're going to be using washing soda for the main reason that sodium chloride when current goes through it will electrolyze to hydrogen gas, which this will also produce, but it's not such a problem It's not going to be much, it's not going to build up like explosively The main problem is that sodium chloride when electrolyzed releases chlorine gas Again, that's not a massive health concern But if it's avoidable, then all the better. And also you will go through your sodium chloride over time, you need to keep it topped up Whereas with this one, the washing soda pretty much stays in solution. It doesn't get affected. The water will hydrolyze off to oxygen and hydrogen, but Not in a way, which is super problematic and you just keep the water topped up I find that I do, if I'm going to be using this thing fairly long-term, which generally I don't, it's just for like at the start to just kind of like get those power curves It, I do need to, the resistance does increase with time, which is to say that the washing soda becomes less conductive with time So I just keep that topped up But I only need to do that like once a week or so if I'm using it across the week So the materials for this are very basic. You just need a plastic bottle About the size is good In the cap, I have drilled two holes Which are for the electrodes In this case, I'll be using stainless steel Bikespokes, I'll just cut them off a wheel. You will definitely want to use stainless steel rather than mild steel otherwise you're going to get a lot of stuff coming off into your solution basically Copper, aluminium You can maybe get away with but stainless steel is best in order to Tell the difference. The easiest way is the magnet This is a galvanized mild steel spoke and you can see that it's quite magnetic. Don't use that The stainless ones are Very slightly magnetic, but basically not at all Also, you can just see that the stainless is a bit shinier the Galvanized is a bit sort of grayer and matter You will definitely know if you're using non-stainless steel in the first sort of three seconds of Actually using the thing because you're gonna get stuck in a lot of black precipitate coming off one of those electrodes. The other main material is Sodium carbonate, which is just washing soda You can get this like this looks like it's like a chemical that I've had to like order in or whatever It's just because I've got a bag of it. You can get this in like pharmacies and it's just it's washing soda You know, it's a household item. It's completely non-toxic and then the other main materials that you'll need are Just a bit of some kind of pipe plastic pipe which Drill a whole bunch of holes in this is purely for the sake of keeping your electrodes kind of close to each other because if they start to Splay out or go all over the place in your bottle, then you're gonna have your resistance vary on you Which you don't want and then the hole that is to allow the sort of exchange of Solution through and across the electrodes so that you don't end up with Like different, you know resistance inside near the electrodes as away from them and then Just two of these wego connector type things are quite standard get the the three-way connections because you'll need all of those I've just Drilled a small hole in the back of one of these Or both of these rather so that the electrodes can go through them and that contact and so then you can vary that electrode While remain maintaining contact to your wires and your meters If you can't get these for some reason then just standard alligator clips We'll do a fairly equivalent job But these are just a little bit nicer and then the other material is a bit of heat shrink to insulate one of your electrodes so that the variable electrode Basically can't touch it. I'm just gonna cut a bit off the bottom there So there's like basically electrons coming out of here going through like a little bit of water and then Into this electrode and out You don't want to ever touch these electrodes or you're gonna blow the fuse in your Meter basically But if it's going through like even if it's only like a couple of millimeters really of The solution then that won't pull so much current as to like blow your 10 amp fuse So the first step is to make the non variable resistor So you're just gonna take one of your electrodes you're going to chuck it through that guy You're gonna put it through the cap you want to drill your holes in your cap small enough that It kind of grabs a bit Just so that when you're setting your variable resistor It stays in place And also so you get sort of minimal leakage out the hole here It's probably good idea once this is all made up to have like a second cap that you can just like take this whole assembly you think out and then Leave the solution as it and then put a cap on which is going to lock lock that off. So you don't get any leaks So you're gonna set that to make some there you're gonna get your heat shrink There measure it so you've got just like maybe half a centimeter of Gep of the end with the water and then just Using the heat gun, but it stopped working You do want a good seal on this because if water can sort of come up inside there, then it's gonna connect conduct electricity out Which you definitely don't want okay That's the first electrode finished basically and then the second one You're going to measure such that it can't touch this guy so you can either just make it like a little bit shorter or What I'm gonna do is put Just like a little bit of heat shrink On the end there so that there's basically no overlap Between the two that'll also help to stop you from like pulling the whole thing out just in case you Do that and that's basically the electrodes done essentially so that's pretty simple and Then There Here you could theoretically and I did last time use Stainless steel rope It's like cable basically instead of these it's another sort of like good accessible source of cheap stainless steel the issue with that is that it's bendy and if you're Putting it in here can sort of like snag on the side and curl up and sort of go weird on you. It's a bit. Um, it's a bit annoying So this is now just gonna go Here physically speaking That's your liquid rear stat. That's it finished the Rest of it is going to be just adding Washing soda to this to get up to the Activity so we can have the the homage that we want To use and test and calibrate this you will need two multimeters one for volts one for amps You will need a battery And you'll just need some you know just wire so the purpose of the battery is because unfortunately if you just put a multimeter on Oms on resistance measuring across these electrodes the mode the meter's gonna freak out It's not gonna make any sense of what's going on in here at all Your your number is gonna go all over the place so the way to test the resistiveness of this is to Put a put a null and voltage through it So I've got a 18 volt just like a power drill Battery, it's gonna put that through the thing. I'm gonna measure the voltage in the system I'm gonna measure the amperage of the system. So Once you know your voltage going through the system once, you know your amperage going through the system then you can very easily calculate your homage your resistance because Vcr your resistance equals your voltage divided by your current by your amps. So for this one I'm gonna Be testing the hydro turbine which is probably gonna be putting out about a hundred and twenty volts Open circuit so under zero load, but under sort of maximum load one there like Under load that's gonna come down to maybe 60 volts and I want to have this Good up to at least six amps So 60 volts divided by six amps equals 10 ohms So what I want in calibrating the system is to have when this is when this the variable electrode is Maximally into the system Then I want a 10 ohm Resistance reading from there and then as I pull that out of the bottle. It's going to Increase the resistance and so drop the current down to pretty much zero if I just have like just like The the very end of this like touching the water And I might get like a hundred ohms or something which is and so then being able to vary that from Minimum current to maximum current and then when I'm testing the turbine Plossing those data points will give me like a power curve And then it'll let me find the peak of that power curve Which is the maximum power that can be a bit like the the load that I want to put on to the turbine That'll give me the maximum wattage out You'll want to use this with Direct current only if you try to use this with like AC coming off an alternator. It's gonna go weird on you so You will need to put your AC if you're generating AC through a bridge rectifier So you've got DC going through you got like coming off your bridge rectifier going through your amp meter going through your Reostat and then back to the other DC terminal of the bridge And you'll want to measure when you're using this to measure to load test your turbine the voltage across the two terminals of the bridge rectifier not the two terminals of the sky because they will give you a slightly skewed reading just because of the rest of the resistance on voltage drop of the system. I made that mistake When I was testing the hydro turbine and also made the mistake of under investing in my alligator clips Which were like really really thin wire. It's got them cheap and so they were putting up a lot of resistance and it looked like I was And then I was measuring just across here and so it really threw off my readings So I got just decent wire and measured across the bridge and everything was happy basically So you're gonna come from your battery through your amp meter amps on 10 It doesn't really matter Which of these is your in and which is your out. It's basically symmetrical. It'll go either way So your Is gonna come into This is why these way go connectors are really good because you just like chuck whatever in them And then your volts meter be volts DC 20 it's gonna come Here as well again, if you're using this Like actually test you'll have this across your bridge rectifier But we want to find this the resistance of this guy self There and then the other volt meter Guy is gonna come the other one here and Then you're gonna want one bit of wire very long Just double that over because that's gonna be going into the battery terminal So the schematic of this is very simple You've got it in your battery through your amps to your electrode through what will be the solution out to your electrode Back to your battery. So just bleh bleh bleh bleh bleh bleh and then you got your volts in parallel across your electrodes now it's just a matter of Put it some water in this guy and then starting to add the washing soda until your volts divided by your amps equals Your ohms that you'll want it would be obviously nicer if like a multi medium multi meter would just measure the resistance of This accurately, but it doesn't But you're gonna have to use this exact same setup to measure your your output From your from your thing anyway, so you might as well, you know get used to it now So that's water You don't need or want to fill this right up to the top because you don't want any sort of like interaction of You know basically a short circuit Across here if it were like right up the top So I forgot to bring a funnel from the kitchen so I just made on one piece of paper and some tape and then I'm just going to start adding the soda to the water until I've been testing My volts and amps until I get a number that I like and then basically we're done Okay, let's measure that each time you use this also like immediately before you Run your run your generator You will want to give this a shake or at least just turn it upside down and act down again just to disperse the Disperse the soda so that's all sort of even because it will tend to Congregate at the bottom over time. It doesn't drop out super quickly but it's a good idea just to your bottle just before you you run your Bion or whatever as you're testing Here Okay, and so we want to test with Your maximum connectivity your minimum resistance. So both electrodes like fully immersed Basically Now being careful again, you don't want to I mean we've made those electrodes that they can't touch each other But just make sure that your electrodes can't touch each other And you are now sticking wires into batteries. So a certain level of respect is due So this is on 10 amps 10 amps fused. This is on volts DC 20 you'll do it's an 18 volt battery that you'll you know depending what your generators will Determine what you want to put that on when you're actually using this but for now That's all good. And we touch that 19.7 So which is like do five that's about 15 16 ohms so we're getting kind of close I'll add just a little bit more just to bring it down towards 10 But I could I could quite happily use it as is to be honest So that's your lesson in how toxic this stuff is which is not at all toxic But it does have a certain lemony kind of zesty kind of flavor, which um Yeah, don't fucking Essentially, I would not recommend Doing lines of this stuff. You can see that some of this is Not that Jesus This is why I'm not a chemist man because I would definitely die on day one So you can see that there is some of this like doesn't dissolve it Stays on as clumps That's fine As long as we get the numbers that we want even it's great. I'm just gonna take a reading of this At its minimum to see what that looks like Get towards 40 ohms so That's not as little as I would like But it's just kind of the trade-off like if you want to make it more conductive for more More current you're also making it more conductive for Your lower end of things the solution to that is to have Longer electrodes in a longer bottle just so that you can get more distance between them So here I'm sort of limited by the length of my bike spokes because they're only coming down to about You know like three quarters of the way down the bottle if I had longer bits of metal I come all the way down I could get that extra bit of resistance but so I'm getting about a 3 to 1 4 to 1 Ratio between my like my high and my low so I might leave it there. I don't really want to add too much more soda just because it's gonna Make it difficult to measure my low amp side of things So I'm happy with that so I call this up basically and so that's it. That's a good real stat Very simple for a cheap pretty effective It's a good option for if you're testing stuff like way off grid that you're out in the field somewhere and You don't have access to too much else basically And there are other options you can use like I say you can use toaster why you can use Light bulbs and the like but they also have their own issues I find this is a little like the most robust and the most easily easily variable so I'm now going to be taking this out to Glasgow to Trial my Water turbine prototype out there gonna be tested site for that. I'm gonna be trying different things so just be a matter of plug this on to the Turbines have got like turbines running in alternator or they're going through a bridge rectifier three feet three phase AC to DC Plugged this in as I had it plugged in here back at the same Try a thing write down some numbers Altered the like the the electrode pull it out a bit right down volts and amps We'll probably just like have the camera point it multi meters and then just like analyze that later Tweak something on the turbine Power curve afterwards and then That'll give me all the data they need to see how to optimize the turbine and how much power and efficiency it can do with the Available also got the Winston vine up on the roof here Which I'll be low testing In a similar way a few notes on safety just the ways in which you could potentially damage yourself with this electricity is involved, so don't touch any of the metal like the Variable resistor is exposed metal it kind of has to be because it has to like be able to slide through the through the cap Testing it with the battery you're only looking at like 20 volts you're probably not going to do yourself much damage with that but Don't touch the middle basically um if you're concerned about that Where gloves any kind of gloves just like latex gloves will see you right Providing you don't get yourself like you know covered in water or whatever when you're testing your turbine that can be a very different situation That can be a lot of volts a lot of amps depending on the thing itself. So again, just be super careful Basically if you can Essentially just don't touch the thing if it's something that you can do discreetly if you can like Flip a switch to like to break the circuit Adjust the thing. This is if you've got any concerns about electrocuting yourself whatsoever and you should Then you can break the circuit adjust the thing turn the you know the switches all safe hit there Write on your numbers turn it off and do it discreetly Or like I say gloves are probably good idea I will be using gloves when I'm testing the water turbine with this because it's water You know, I'm gonna you know get splashed and stuff and that turbine can put out enough power to you know Do some damage this is not more dangerous than pretty much any other kind of load If you know get your finger in some exposed metal with you know current running through it And then you'll wish you hadn't basically Chemically like I say the washing soda is pretty benign. It's washing soda You're not gonna do something damage even if you inhale a lung full of it like I just did and The rest of it is just you know basic tools and stuff to drill through your hand or whatever Oh the other thing hydrogen gas Is the other sort of like main thing to to worry about in that? Don't really worry about it. It's Not going to build up. So it's got much pressure or much volume or much sort of propensity to explode If you're concerned about it, you can just drill an extra hole in here so that it can waft off as soon as it As soon as it builds up Don't smoke directly into your liquid rheostat. I guess that's pretty much, you know good for various reasons Like I say if you're using sodium chloride or other kind of like Electrolytes for this sodium chloride will put off chlorine gas when it electrolyzes I don't want to use it for that reason but as I understand it you're unlikely to Get like actually dangerous levels of chlorine gas even in a closed space, which you're unlikely to be using this in It's not like you do much harm Chlorine gas is quite good in that It lets you know when it's poisoning you like it'll build up or start stinging your eyes You get a taste in your mouth So if that happens then you know open a window or whatever And then if you're using some really weird stuff don't Watching so easy to get just use watching so it's easy There's a process for converting baking soda into washing soda just by putting it in your oven If you're somewhere that you're that hard up for for options then Probably use table salt Honestly, if like you just got like nothing to work with you can just just use cable table salt keep it topped out keep yourself aerated and And you'll be fine Think that's about it So hopefully that was useful to you. I don't think there's another tutorial on the internet on how to make a liquid Rear step not one that I've found These this is why I use myself so it's it's the best option that for me for testing stuff in the field if you have any questions or suggestions or the usual then tag them below and Yeah, the the next time you'll see this will be in Probably the next video that I'll do which will be the results from the Water turbine testing to see this in action there Thanks for your time. Hopefully this is useful to you and I will see you around