a while ago I had one of my viewers write in and ask how I made a load tester he saw me use in one of my videos so in this video we're going to cover how to make a load tester so before we get into the build let's take a quick moment to discuss our load test we're going to be building now the type of load test of a building is called a resistive load tester and essentially it uses wire wound resistors to act as a load on something so essentially what the resistor therefore is to convert electricity into heat now why is this useful well let's say you bought a buck converter like this one and you want to put it through a stress test and make sure it outputs the correct power make sure it's stable make sure it doesn't blow up and send full voltage through to whatever components you have normally hooked up to it so you can hook up your load tester test it for a few hours make sure all is well and then it passes the test or it doesn't it's great for testing new circuits maybe you've built something new and you need a load to dummy loads to test the circuit without hooking up any expensive equipment before knowing that it actually works you could also test out empathize so sometimes audio technicians will want to run a 1 kilohertz sine wave through an amplifier for various reasons and testing and trust me the 1 kilohertz sine wave is really ear piercing and annoying if you're playing it through a speaker so a resistive load tester like we're going to build in this video can be advantageous because it's essentially as far as amplifiers concerned replaces a speaker exactly the same but it doesn't make your ears bleed it's absolutely silent of course so that is a couple of ways we could use a load tester so now let's look at the components we're going to need so over here I've got 8 terminal mounts so these can accept a banana plug in the end or they can screw down on some beer wire and no particular reason I got these colors there is a positive or negative with the resistors we're using naturally so just get whatever color you like I've got four millimeter by eight millimeter long pot roots to secure the wire around the resistors in the enclosure later you can use nuts screws bolts whatever it takes your fancy now let's talk about the style of resistor I'm using these are wire wound and they mounted in a aluminum heatsink to help dissipate heat and you can scale this up or down to suit whatever requirements you want so all the resistors they've got here are 50 watts however if you need a 500 watt resistor you can buy that so just use this as a template and build from it I'm going to be using two 16 ohm resistors into 8 ohm resistors for my load tester today we're going to need some three millimeter heat shrink some 18 American wire gauge tinned copper wire and an abs jiffy box so how's everything and as far as tools go it's going to be the basics drill soldering iron wire strippers cutters just the basics nothing fancy let's get into the bill so the first thing I've done is gone ahead and marked out the front panel where I'm going to drill holes so I can mount all my terminals along them so now I'm going to go drill that out with an appropriate size drill bits and mounted my terminals so finish drilling the holes and just screwing in the terminals into the top of the enclosure and you'll note that I've mounted them quite high on the enclosure and that's so that when we install the resistors on the bottom plate here that they give us plenty of clearance rule the wire and everything to bunch up now what I'm going to go ahead and do is mark out where I need to drill my holes for all these resistors and then secure them to the bottom plate using these pop rivets so I've got my wire wound resistors or pop riveted securely to the base of the enclosure and the next job is to wire up the connectors on the resistors here two pairs of 10 mils on the top so these resistors you can see they have eyes and the the lugs and what I recommend doing is stripping off a fairly good length of copper and shredding the wire through the eye and then bending it back on itself and what that means is should this resistor get hot enough to melt solder which it shouldn't by the way but in the event something catastrophic happened and it did get hot enough to melt solder there's still a mechanical connection preventing this wire from just breaking free and plus we're going to put some heat shrink over the entire tension it's going to strengthen that even further so I'm going to go ahead and solder all the connectors to matching pairs on the lid here off camera so that's going to be tedious and quite boring frankly so come back on that stub so I've just finished soldering and heat shrinking all the connections that there's no exposed connection points and basically every resistor is soldered to a red and a black so that I don't lose track of what is what and I've just used a label maker just to remind myself that the 8 ohm and the 16 ohm are on either side so now we can sort of bunch the wires up and press everything together and then secure the enclosure with the included screws you now our load tester is assembled and ready to use so now I'm just going to go over some basics of how you can use this from different configurations so basically we're not limited just 18 and 16 ohm loads how we wire the resistors together can change the amount of resistance we can either lower or increase this so for instance if we wire the two 8 ohm as they're over here if we were over to 8 ohm resistors together in parallel you will essentially get a 4 ohm load similarly if you wire them in series you'll get a 16 ohm load same with the 16 ohm of course super wire them in series we get 32 we wire them in parallel we get 8 ohms and you can't effectively if you want to wire the two 16 ohm resistors in parallel you get 8 ohms and you might think that's a bit pointless because we already got 8 ohm resistors over here well actually no there is a point to that because remember each of these resistors was rated at 50 watts so if we wire two of them in parallel we get 8 ohms and we also can handle a hundred watts of power rather than 250 and there's many many other combinations you could do you know it's not too hard to work out what sort of resistance you're going to get with different combinations but failing that a simple multimeter was up with a resistance test will tell you exactly how you've wired them and configured them I'll make up some little wires here just so that I can connect and bridge any of the resistors together I want but a better alternative to just a wire is to buy some banana plugs and just make simple British connectors so you can plug any resistant to any other resistor for any type of testing you need to do so one thing I briefly want to discuss is how we calculate how many watts of power we're pushing through our load tester because naturally we don't exceed the maximum rating on our resistors so I'll leave a link in the video's description foolís owns little calculator so it's make up a hypothetical scenario let's say I have a 12 volt power source and my load test is 4 amps of current being passed through it at calculate and we can see here our wattage is calculated at 48 watts another thing I want to discuss is heat management of these resistors so although the resistor itself can handle 50 Watts just fine continuous the enclosure I've used here certainly will not like that for extended period of time they're going to get very warm and they probably get to the point where they melt or at least distort a plastic so when you're building your enclosure take things like that into account you could use a die cast aluminium box that's going to not only have high temperature resistance to help dissipate heat you could have ventilation you could even put a fan in the box if you wanted so depending on your application take those into account now to demonstrate what 50 watts of power push through a 8 ohm resistor looks like I've got a hundred watt 8 ohm resistor here as a test so but as I said I'm only putting 50 watts through this resistor I've got my multimeter hooked up to it with a K type sensor so we're going to see the temperature its measured over here in Celsius so I'm going to run it for a minute and we're going to see how roasty-toasty this resistor gets you so we're a minute now and you is absolutely no sign of that temperature hitting a threshold anytime soon it's still rapidly climbing so yeah definiteiy listen to account when designing an enclosure if you're pushing high wattage through one of these resistors you're going to need adequate cooling to handle that for a sustained runtime so that about wraps it up for this video I hope you found it useful if you did please give the video a like I'd be much appreciated and also if you like this video go check out some of the others I'm sure there'll be something in there you'll find entertaining we've also got plenty of future projects planned and some very exciting ones at that so please stick around hope to see in the next video bye for now