Summary

Are Power Distribution Modules a game changer or an unnecessary complexity? In this Webinar we will break down the pros and cons to both PDM's and traditional fuse and relay setups to help you choose the right option for your build.

00:00 Welcome ladies, gentlemen and mechanics.
00:02 I'm Caleb here at High Performance Academy and today we've got another webinar.
00:06 Today I'm going to talk about relays, fuses and comparing them to PDMs.
00:12 It's something I'm sure we've all had a discussion about at some point.
00:15 What's better? What's more expensive? Who should use what? Who's a peasant for using what? And it's a discussion that I see a lot on forums especially and it gets some pretty interesting points.
00:27 I want to try and clear up some of those and let's see if we can come to maybe a bit of a decision at the end of what is actually better.
00:34 Now, this is a live webinar but if you can't watch it right now or you need to watch it later it will be recorded and you can watch it at another point in time.
00:42 So, don't stress if you've got to go pick up the kids.
00:45 Also if you're watching this at a later point in time, if you have any questions, jump on the website, emails at support at HPAcademy.com or jump on the forums and chuck your question in there.
00:56 If you're here now listening and watching, put your questions in the chat and one of our boys will get them on screen for me here to answer at the end.
01:04 Try and keep your questions nearer to the end just because I naturally should go through and hopefully answer some of them for you.
01:10 So, let's start off with the absolute basics.
01:13 So, electrically we have an issue where we hook something up to a power source and it's something like a light or an actuator, it will stay on indefinitely until we interrupt that power.
01:24 And naturally the normal way we do this is with a switch.
01:28 Things have evolved since and we've had to be able to switch those loads with computers, sensors, other components or to automate things.
01:38 And from that the relay was developed.
01:41 And if we come over to our whiteboard here, our overview, got a few drawings here.
01:47 Let's ignore everything to the right and just have a look on the left here.
01:50 We'll start off with one of the more important things of a circuit and that is circuit protection.
01:56 If you know anything about electronics you know that we can sometimes cause issues where we have a serious amount of current go through that we don't want and that will let the genies out and that's not something we want because they can cause fires.
02:08 So, to stop that we have fuses.
02:11 Obviously, this is a bit too small for you guys to see but it's a standard blade fuse.
02:14 Have a drawing here of the basic layout.
02:16 Pretty simple idea, conductors either side.
02:20 They allow our power to go through.
02:22 They are designed in the center here with a thinner, usually thinner, with a higher amp that will be a bit thicker.
02:27 It's designed in a way that at a certain temperature, certain current, because when current passes through it creates heat.
02:34 If it gets too high above, say if this is a 20 amp rated, if it gets around that it's going to get really hot in here.
02:40 I'm going to use red just for theatrics.
02:42 That'll get really hot and it'll break and destroy our connection, effectively cutting off the supply and stopping the car from breaking down.
02:50 Now, this is what you'd call a sacrificial protection.
02:54 So, once that's done and busted, we can't open it up, re-solder it and fix it.
02:58 It's a throwaway.
02:59 We replace it with a new one.
03:01 Good for circuit protection.
03:02 It's lasted for centuries and, well, it's not centuries, sorry, decades, and it's worked great so we still use it.
03:08 There are obviously different sizes.
03:10 We get a smaller micro blade.
03:12 We also, I'll touch on circuit breakers.
03:15 I have one of them here.
03:16 Same idea.
03:17 It's a circuit protection, but instead of having a point that fails for good, it's got a, generally a bi-metallic, bi-metallic, bi -metallic? Yes.
03:26 Strip inside which will bend at a certain temperature, disconnects our connection and then closes once it cools down.
03:33 Essentially the same thing, but has the advantage of resetting itself.
03:37 Sometimes they are manually reset and these are used a lot as well.
03:41 You'll see them in things like power window circuits.
03:44 When you put your power window up, it hits its limit.
03:47 It's still trying to power the motor.
03:49 You might hear it click and that is your circuit breaker tripping out to say you've tried to close your window and it is actually closed.
03:55 So, stop doing that.
03:57 That's our circuit protection and we'll go back to now our relays.
04:01 Our switching mechanism that is used pretty commonly these days.
04:06 Still in a lot of OEM cars and especially throughout our older 90s cars and things.
04:12 I'll show you what we've got here.
04:14 This is a fairly standard relay.
04:18 It doesn't even have a brand on here.
04:20 But it's a 4 pin relay.
04:22 This is our circuit diagram.
04:24 This is what's going on inside which if I show you here, this is actually when I've ripped open.
04:28 We've got a coil which is here.
04:30 You can see it's quite obvious with the many windings of small wire.
04:35 They are connected to our outside pins.
04:37 These are used to control the relay.
04:40 They are our controlling circuit.
04:43 Put power across a coil and it creates a magnetic field.
04:47 What that magnetic field is then doing, we have a lever.
04:51 It's a strip that is able to be magnetized.
04:56 Well it's attracted to magnetic fields.
04:58 That is pulled down and because of the levering action it's going to push these contacts together.
05:03 These are our switching contacts where we want power to pass through.
05:07 I'll show you this here.
05:09 It's a little bit different.
05:10 It's just on its side.
05:12 We have on this side here our levering action which just goes back and forth between these two contacts.
05:19 Really small to see.
05:20 I don't know if it's zoomed in enough but that's the basic idea.
05:24 Now, one thing I always hear from people is that... I'm jumping ahead a little bit.
05:29 I try not to jump back and forth too much but PDMs are more complex.
05:32 There's more to go wrong.
05:33 But having a look here at a relay it's actually not as simple inside as you might think.
05:37 We have a hell of a lot of coils here going around.
05:40 Really small wire.
05:42 Thin bits of metal that are moving back and forth constantly.
05:44 Little contacts inside here.
05:46 Everything is moving and can wear out.
05:49 So, it's still an object that is prone to mechanical failure because of that.
05:55 Now, the whole reason of a relay.
05:58 It helps us with switching large currents.
06:00 If we have a small switch on our dash.
06:03 Generally, things like fuel pumps or fans.
06:07 Something that's going to draw a fair bit of current.
06:09 Those switches can't handle that and the contacts on those switches.
06:13 The connectors.
06:14 Even the wiring going to those switches.
06:16 If it's not large enough will burn out because of that current.
06:19 What the relay allows us to do.
06:21 The switch only controls the current to our coil.
06:24 That has a very very small current draw.
06:27 When that's switched on it mechanically switches our switch and allows current to pass to our load source.
06:33 And this just takes away all the current from that switch and allows you to have smaller wiring to your dash.
06:40 Less current going to anywhere that you're using a switch.
06:43 And this is an idea that's used not just in cars but all over the place.
06:46 You can get relays for household, industrial that switches AC from a DC circuit.
06:54 I won't try.
06:54 I'll try not to get into that too deep.
06:56 This is going to be a debate at the end of it between the two.
06:59 I just want to try and give you an idea of how everything works.
07:02 Great object.
07:04 Great part.
07:04 It's always worked.
07:05 They come in a variety of sizes.
07:07 This is an ultra micro relay.
07:08 Does the same job.
07:10 They come in different pin outs.
07:12 This is a five pin.
07:14 So, rather than the single contacts it's got a contact either side.
07:18 When it's off it has current passing through two pins constantly.
07:22 Turn it on it swaps over to another pin.
07:25 Called a changeover relay.
07:26 Generally, your relays you'll come across are standard and changeover.
07:31 Now, when it comes to relays you can't just chuck it in your car and that's done.
07:35 You need a way of mounting them.
07:37 That can come in a variety of ways.
07:39 This is a pretty standard relay base.
07:42 It just allows you to wire into the base using crimp terminals.
07:47 I've got one here that's been crimped.
07:49 And then that just allows you to insert into the base and the relay plugs into the top.
07:56 It can only go one way even though you'll try and put it in three different ways and it'll never be right.
08:01 And then that's wired into your car.
08:03 You'll generally more often than not have three to four circuits going to it.
08:08 Two for the coil.
08:10 Turning that on and off you'll need a power in and an earth to switch it.
08:13 And then a power in power out or it can be a ground in ground out.
08:17 You'll just need to interrupt a circuit somewhere.
08:20 Some of these will be three wire and that is because if you have power going in it will share that power over to the coil and you can switch the negative side.
08:29 Simplifies the wiring a little bit and if you're in a situation where you're going to be using this with ignition off or something like a horn that always needs power and you're going to switch it anytime the car is off you need constant power there.
08:43 The coil is going to need constant power.
08:45 A problem we have sometimes or I see it a lot when people have wired up their own relays with ECUs.
08:51 Relays are really good for switching high current components from an ECU.
08:55 The ECU isn't designed to switch high currents but it can switch the coil quite easily and it's happy to have that small amount of current.
09:03 So, they're always or not always sorry they're often used with ECUs to switch things like fans where the ECU is supplying an earth to our coil there's a ignition or constant power to the other side and that switches it.
09:15 And I've just touched on there what the problem is sometimes people will wire a constant 12 volt to a relay that is earth switched by the ECU and the problem we have is there is a lot of ECUs that'll actually default to a ground when they're turned off.
09:30 So, you turn your car off the ECU powers down its outputs then go to a ground and it turns on your fans because they have a constant power to your relay.
09:40 So, one thing to generally make sure of is when your circuit is being powered where it's being powered and switched by making sure you have the correct switching current to one side whether it's ignition or straight power or something else entirely.
09:54 Next, there's another kind of base this is just a weather sealed one it comes pre-wired.
10:00 Personally for me I don't like pre-wired things just because it adds another point where we're going to crimp onto here extra wires you've already got a crimp inside there we're adding in one more point of failure.
10:13 Also I've seen very much with cheaper relay bases and cheaper relays in general just anything that is cheaper these crimp terminals are sometimes less quality the crimps themselves are pretty bad and the wiring can be bad.
10:27 Now, I'm not ragging on fuses and relays they definitely have their place as I've said they're used a lot for being switched by ECUs it's an advantage where the ECU is taking a signal like your temperature and it can decide at what point it wants to switch your fan on rather than you having to sit there watch your temperature and go hey car's getting too hot I'm going to switch on my fan relay.
10:52 So, now what about PDMs? Why does everyone rave on about them? Why do people badmouth them sometimes? Why, why, why, why PDMs? Well they do the same thing really they are taking over what we've got here circuit protection and power distribution hence the name PDM Power Distribution Module.
11:16 You will find sometimes I've seen fuse boxes and just general yeah fuse and relay boxes are referred to as PDMs technically they are a power distribution module or box but when we refer to PDMs these days we are referring to electronically controlled computerized power distribution modules.
11:37 A lot smarter, a lot better to work with.
11:40 So, how do they do the same thing? Well this is going to come into my weird little box here with NPN Emitter Base Collector.
11:48 I'm going to touch on this really basically because it's something you can delve into quite deep.
11:53 The PDM uses what's called a transistor.
11:57 Now, these are really, really, really small modules, electronic parts that do the same job as a relay.
12:06 They allow current to pass through when a signal is given to them.
12:10 And what I have here it's called a NPN transistor hence this you can also get PNP.
12:17 There are quite a few different types of transistors this will just give you a basic overview.
12:21 What we have is one side and the other side they are it's a it's a silicon that is now let me try and explain this in a way that's not going to lead into too much over talking.
12:33 It's a semiconductor which doesn't allow current to pass through because of the way that the materials in here electronically pass the current through.
12:42 There are barriers here and in short the electrons can't actually pass from one side to the other.
12:49 This is our switching circuit, it's our two contacts on our relay.
12:52 We want current to go through and to do that on our base we have a signal that comes to this point.
12:58 In different transistor situations this can be just a different voltage, a current, there's a lot of different ways that can explain it.
13:04 We might go into that in a later video but basically when that signal is supplied here it essentially opens up these gates and allows current to pass through.
13:12 Now, the big advantage here that most of you will hear when people are talking about PDM versus relay is that they are solid state, there are no moving parts.
13:21 When we have the relay here as we zoomed in and saw earlier there's mechanical moving parts that are going back and forth.
13:28 The issue we have here is these contacts every time they're switching back and forth there's potential for arcing to happen across those contacts.
13:34 There's damage that can happen, the springs can all wear out, there's a lot of mechanical parts that actually can break.
13:41 Now, when we have a completely solid state, no moving part electronic device, there's no moving parts, they can't wear out.
13:49 Basically, they are a lot more reliable and as I said they are packaged a lot smaller.
13:56 Transistors these days work into the nanometers, two to three nanometers small and that's like I can't even show you here how small that is but basically yeah you'd be able to fit trillions of them on this whiteboard so I'm not going to bother trying to draw it.
14:11 So, that is one of the big advantages is they are small.
14:14 Now, to go on that though, these small transistors can't handle the current that a relay can.
14:21 That is one of the advantages of a relay, they can handle quite a bit of current because of the large mechanical contacts they're safe to use.
14:29 But there are certain transistors like MOSFETs that you'll hear of, they are what are used for power switching.
14:35 They are specifically designed for switching those high current loads and that is exactly what is in our PDMs.
14:42 I'll show you here, this is a PDM that's on the market, ECU Master PMU16.
14:48 These are a really good unit, they are well priced for what they are.
14:52 We run three of them in Andre's SR86 project race car.
14:58 This is actually one from it, hopefully I'll get it back in before he sees this webinar.
15:03 This is a 16 channel which basically just means we have 16 relays and fuse circuits that this can control.
15:10 So, what is inside is 16 of these transistors and the advantage of all this is it's electronically controlled.
15:19 It has a brain essentially, it sees the current going into these transistors, current going out and it's able to read that and work it into a computer language and keep track of it.
15:31 A fuse, it blows, yeah you'll know about it but that's basically it.
15:36 There's nothing else happens, the fuse blows, your circuit's dead and you're stuck on the side of the road.
15:41 You can replace a fuse, swap them from another point and you'll be on your way again.
15:45 It's simple, it is effective but there are limits to that.
15:49 Those limits are definitely better in the PMU PDM because it is electronically controlled.
15:56 The computer inside of this can actually see what kind of current is passing through and that's its fuse circuit protection.
16:03 It'll see what current goes through, you program it to say hey we don't want any more than 5 amps to go through this, it knows that, it sees that if it gets up to 5 or above 5 it'll electronically shut these transistors off, not allow the current to pass through and you've essentially cut your circuit without causing any damage.
16:22 Similar to how your circuit breakers work, it's stopped the power going through, hasn't caused any damage or made parts need to be replaced but also not like the circuit breaker, there's no mechanical parts that have to move to do this.
16:36 We're back to our transistor which is controlling everything electronically and without any moving parts.
16:43 So, that's one of the advantages of being able to control the current electronically and this is also, having all the information electronically on the unit, you can data log this.
16:53 That makes diagnostics so much easier.
16:57 Sometimes you'll blow a fuse, often you'll have multiple circuits on that fuse, you've got no idea what's actually happened.
17:03 You might recall what switch you flicked but a lot of the time it's happened randomly and you just got to kind of figure it out.
17:10 Logging on a PDM, it'll actually tell you what switch you've flicked at what time, what parameters have actually happened, when that amperage has gone too high and this can really help narrow down where that problem has actually occurred.
17:24 So, that's one of the PDMs that's on the market which is a really good choice.
17:28 When you're going to go really high end, you start going into things like the MoTeC.
17:33 This is a PDM32.
17:35 32 circuits, so we got 32 essentially relays and fuses.
17:41 These are a motorsport spec, you can tell by the autosport connectors.
17:45 These are not cheap, as Andre would say the price is eye-watering, but they are worth the money essentially.
17:52 I'll go over a bit later of the price comparison because I think that is probably one of the biggest factors of when people are comparing a PDM with a relay or circuit breaker or fuse.
18:03 So, touching on that price, yes, they are more expensive, but have you ever actually sat down and worked out the price of what it would take to wire up 16 relays and 16 fuses? If we jump over to the computer for a second, I have just got here quickly a spreadsheet that I've done up just quickly.
18:26 I've used Kiwi Connectors here who supply ECU master products, just trying to go by some off -the -shelf prices here just to keep things fairly relatable.
18:37 This is all in New Zealand dollars, but it's trying to compare apples to apples.
18:41 So, I'll just chuck this here.
18:43 One ECU, we've got 16 outputs for that.
18:45 So, let's now make that up in relays and fuses.
18:48 Now, I'm going to pick things on the more expensive side just because we want quality.
18:52 At the end of the day, these PDMs are designed to a high quality.
18:55 They are designed with motorsport in mind generally, which allows them to tolerate high heat and vibration, all that kind of stuff.
19:03 Relays, fuses, they are designed for harsh environments as well.
19:08 Particularly though, you often need to use things like those weatherproof bases.
19:14 Because if you have a look at the actual relay base itself, a lot of them aren't weather protected and you're getting all that in a PDM.
19:21 So, when I compare prices here, I'm going to look a bit more on the expensive and better quality side as far as relays.
19:27 Now, this is on a bit of an extreme side.
19:29 It's an OEM relay.
19:30 This is a replacement part, $115 straight away.
19:33 That price is getting a bit ridiculous, but I'll use a normal, fairly common Narva 5 pin relay, which is going to cost us $34.99.
19:42 So, I'll just add that in here quickly.
19:44 $34.99 for one relay.
19:46 Next, we need a base for that relay.
19:49 Here we've got another base, a Jalec relay base.
19:52 We can mount that wherever we want.
19:54 It comes with a terminal so we can wire it.
19:55 It's not pre-wired, which is my preference.
19:57 That is $24.99.
20:00 $24.99.
20:02 Next, we need some circuit protection.
20:04 Now, just using a standard blade fuse isn't really a good comparison for a PDM because they have those smart circuit protections.
20:12 And the closest thing to that would be a circuit breaker.
20:14 So, we're going to use one of these blade type circuit breakers, which come in at $19.99 each.
20:20 Chuck that in there as well.
20:22 And of course we need somewhere to put that.
20:24 I'm going to use just a standard inline fuse holder.
20:26 Now, we do get fuse blocks, things like that, that can hold a lot more, work out a bit cheaper.
20:32 I'm trying to do a bit of a worst case scenario here, but I'll touch on that a bit later.
20:36 For one of these, $15.49.
20:38 That is waterproof, which goes with our sort of PDM specs.
20:42 Now, I will say they're not 100% waterproof, they are just weatherproof.
20:45 They have seals on connectors and things.
20:47 So,rry, what was that? $15.49.
20:51 So, for our ECU Master, that is 16 of these relays and outputs.
20:56 So, let's chuck a 16 in all these.
20:58 I'm up to $1,527 just in those parts, which yes, there's still a gap between the ECU Master and these fuses and relays.
21:08 But at the same time, you have to think there's wiring on top of this.
21:12 With a PDM, you're wiring a main power in, a main earth, and then it will be a lot of inputs and outputs and you're done.
21:21 Whereas with a relay, each individual relay, each fuse all need a connection.
21:26 You will have generally four to five connections on each relay, two connections on each fuse.
21:33 And that time really adds up when you're sitting there pinning them back and forth and working out where things go.
21:38 It's a good place to make mistakes as well.
21:40 When you're wiring up a PDM, especially if we have a look at this back over at the whiteboard, the PMU-16.
21:47 As you can see, we have a main terminal for our power and then just one simple connection, which is going to have all our inputs, outputs and grounds.
21:54 And it just makes it so much easier.
21:55 You know, you've got one plug, chuck it on, done.
21:58 Think about having 16 of these fuses and relays.
22:02 I will show you like this relay does have an inbuilt fuse, which makes things a bit easier as well.
22:07 Problem with this is you're often mounting these relays probably somewhere fairly far from your power distribution, your power stud or whatever you're using to distribute your power.
22:17 And you ideally want your fuse closer to that point, not all the way at your relay, but this can get you out of trouble pretty quick.
22:23 So, that's the other issue is you're adding a lot of complexity as far as wiring.
22:28 Now, to go on the relay and fuse side, PDMs do involve software and using your computer to set them up afterwards.
22:38 And it adds on to the complexity.
22:42 I think once you've used a few PDMs, you've got the idea.
22:45 Even have a play around with the software before you buy one to work out what you want.
22:49 If you can build a several layer building in Minecraft and protect it from zombies riding chickens, I'm pretty sure you can work with software to work PDM.
23:03 It's relatively simple once you get into it.
23:05 We do have a course that is specifically for setting up PDMs that's really valuable, goes pretty in depth.
23:11 So, that side of it, I feel like isn't much of a complexity to add on.
23:15 It's similar to wiring up each individual relay and fuse, but it's just a bit simpler on the end of you just sit at your computer and type in things.
23:27 Also, the other side of that is if you make a mistake with the relay and fuse, pin it the wrong way around, put something in wrong, go to power it up, there's a really good chance you're going to let those genies out and there's going to be some serious consequences and possibly damage things.
23:43 PDM, there's still that potential of damaging it if you wire it up wrong, but I feel like it is a lot simpler to work in that regard and doesn't actually allow you to come to those genie letting out problems.
23:57 Mainly because you have one main power in, that's the power source and your PDM will take care of things internally.
24:04 If it sees there's too much current passing through at one point, something's not quite wired up right, generally they will have their internal protection that will take care of that and you won't go damaging a part.
24:14 Having said that, please don't wire them up purposely wrong to prove me wrong and blow up an ECU, master PDM, because I am not responsible and it will get replaced.
24:24 Anyway, another common thing I hear people talk about is again that complexity of a PDM.
24:32 People say it's more parts, more things to go wrong, it's unproven technology or something it hasn't been around for that long.
24:40 At the end of the day, transistors, they've been around for decades, they've been around for a long, long time.
24:46 And one thing to think about is how many of you out there have cars that are running on an ECU? If we have a look at this 3S-GTE ECU that I have here above the whiteboard, this has transistors, well a lot that you won't even see, but along here four big units right there, they are transistors that control our injectors.
25:06 They are switching on and off over and over again, thousands and thousands of times every day when you drive your car.
25:12 They are dealing with the earth side of the injector and the computer is switching them on.
25:19 ECUs have been doing this for so long and transistors have been around for that long, it's nothing new, it's not a new technology.
25:24 PDMs, they're just doing things in a different way, they're controlling higher currents and doing it really well.
25:33 What was the other point I was going to make here? 3S-GTEs are really good.
25:39 So, I will note they are only powering injectors as I said, so it isn't a high current situation.
25:45 The MOSFETs, the type of transistor in PDMs, are a higher current power switching situation and generally that's why you will tie in an ECU with a PDM.
25:56 Your ECU won't come with those MOSFETs, they will come with some for things like drive-by -wire control, but having a PDM allows you for a lot more control.
26:06 The ECU can talk back and forth.
26:08 Another really good point, you can't talk to a relay and a fuse with CAN bus, they won't have any idea what you're talking about.
26:16 Most PDMs these days will come with CAN bus network capabilities, they can talk to everything from your dash to your keypad to the ECU and it just allows a lot more information to be used and makes them so much more... what's the word? Use them in a lot more places.
26:33 My brain is having a real blank on what the word is.
26:39 Anyway, so they're not a new technology.
26:42 Even the phone in your pocket that you're using to look at memes, that has got billions of transistors in it at the microscopic level and they've been working for decades and they do go wrong occasionally, but it's like a relay.
26:54 How many of you have had a relay fail in a car or a fuse blow and everything fails at some point? Transistors are proven to work for a long time and they're in everything.
27:04 Computer, screens, phones, absolutely everything.
27:08 So, the PDM, its technology is not new, don't be afraid of it in that direction.
27:13 Don't be afraid of the software, it is relatively easy once you get into it, just work on one or two circuits at a time and you'll get it pretty quick.
27:22 Next,, let me just go through my notes.
27:24 I will take a point here, if you've got any questions start chucking them into the chat because we'll come to the end soon and we'll get them all in if I haven't covered something or I've been really vague on something, chuck a question in and I'll try my best to answer it.
27:43 So, I'll touch on just the controlling of PDMs.
27:49 They can be switched just with your generic switches, much like a relay, or they can be controlled with, like I said, our CAN bus keypads or with ECUs.
27:57 Versatility, that's the word I was looking for, they are really versatile in what they can use.
28:02 And that also means with your software you're able to change things really easily.
28:08 If you have 16 relays or even 32 as we're looking at with the MoTeC PDM, you have all of them in one place with a whole heap of wires and you want to just change the point where something switches or change what current is allowed.
28:24 There's a lot of wiring, you know, swapping around moving and it can just get a bit too complex or you might need a completely different relay, you might need a changeover instead of just a normally open or closed.
28:34 And so with a PDM it's as simple as saying hey I'm going to change this output to this and I want it to do it at this point, use this math channel, use all this information and you can really make it as complex as you want or as simple as you want.
28:47 They're really good for things like if you're switching your indicators.
28:50 Conventionally you would need a flasher relay and this would cause a flash, it turns on and off.
28:58 The PDM can be designed internally that it's going to decide that flashing, flash rate, when it's going to flash and it does that all through these transistors turning them on and off.
29:08 The other really good point with transistors over relays, they do it really, really, really quickly.
29:14 Excuse me.
29:16 We may not be able to, you know, interpret it by our eye or whatever, you know, how we're feeling our relays but there is a brief delay between, you know, magnetizing this, the contacts closing.
29:27 Things like those contacts, when they close, they can actually bounce a little bit and cause fluctuations.
29:33 Transistors are so much better at doing this, quicker, more reliable and efficient.
29:38 The one downside, which also the downside with relays is heat.
29:43 With pretty much any electronic device, it's going to have some waste electronics, less electrical power and that comes out as heat.
29:51 So, these things heat up.
29:52 If you've ever touched a relay when it's been sitting in the car with something turned on for a considerable amount of time, it will feel quite hot to touch.
29:58 Same with transistors and components like that.
30:02 And you'll see most things, like in this ECU, I'm not sure if these are transistors or regulators.
30:08 One thing with circuits, you will find things are packaged in a similar way and can be completely different components.
30:14 But most MOSFET transistors will look sort of like this and they are often mounted to an aluminium piece that will disperse the heat evenly and allow it to cool down.
30:25 So, that is still a point that we need to consider.
30:28 A lot of our PDMs, they are a solid case of aluminium which allows some cooling aspects.
30:36 Inside they're generally mounted in a way that the MOSFETs will be in contact with this aluminium casing and that is actually part of the cooling.
30:44 So, when we mount these, we need to make sure that there is sufficient airflow and they can disperse that heat.
30:51 As with everything, things have limitations.
30:54 But when it comes to working out those limitations and how you're going to mount things, it's generally the same.
30:59 You're not going to mount a relay and fuse directly next to your turbo and exhaust manifold, it will melt.
31:05 As with the PDM, it's going to get too hot and cause failures.
31:09 When it comes to it though, things like this relay block, we want 32 of these.
31:15 Mounting that in your car somewhere is going to be pretty difficult.
31:18 Whereas mounting this in your car, or mounting this, it's so much easier.
31:22 You've got mounting points which can be bolted straight in.
31:25 They take up considerably less room.
31:27 I wasn't going to go buy 32 relays and fuses just to prove that point, but I think we can all sort of picture it in our head.
31:34 So, being compact and space saving is another really good aspect.
31:40 Now, coming up to questions soon, there's one more thing I want to touch on.
31:44 Just see if we've got any... yep, we've got plenty of questions, so I'll get to that in a second.
31:50 Now, I feel like I may have been talking bad about relays and fuses and really up-talking PDMs.
31:57 Relays and fuses do still have their place.
31:59 They are still in cars, we still use them all the time.
32:02 I installed a few relays and fuses in my car just a few weeks ago.
32:06 I can't remember off the top of my head what I was actually wiring in.
32:08 I think it was something to do with the stereo.
32:10 But they are still definitely used.
32:12 They still 100% have their place.
32:14 Probably the biggest factor is price and availability.
32:17 Most automotive shops will have them on the shelf ready to go.
32:21 Most automotive shops won't have a PDM ready to go.
32:24 And if you want to get something up and done quickly, a relay and fuse will definitely get you there quickly.
32:29 As far as being reliable, they are both...
32:33 they both... what's the word? You get what you pay for.
32:37 If you're going to buy a really cheap non -branded PDM, it's probably cheap for a reason.
32:43 Same with relays and fuses.
32:44 If you're going to buy them off AliExpress, yeah they might work for a while.
32:48 But please don't use that as an excuse because they probably are going to fail at some point.
32:53 So, from a cost aspect, definitely relays and fuses are in that more enthusiast level.
33:00 But like I showed with that example, once you start adding up a considerable amount of them, you're coming pretty close to that price of a PDM anyway and it's kind of worth that extra cost.
33:10 Especially when you get the things like software control, the added circuit protection capabilities, and just in general being a cooler little device that you can brag about.
33:20 But like I said, they do still have their place.
33:23 I use them when you're doing something that only needs a couple of circuits added.
33:27 Maybe you're adding fog lights onto your car, spotlights, and you're only going to need to switch one or two circuits.
33:33 In those situations, it definitely makes more sense to go buy a relay and a few fuses rather than going and buy a whole PDM.
33:40 On that though, if we come over to the laptop, there are actual situations, there are cases where you can get smaller PDMs.
33:48 What I'm looking at here is a Metric Motorsports UPDM4.
33:53 This is Australian dollars, this is Garage 7 in Adelaide.
33:57 They are a small PDM which has four outputs.
34:01 They're primarily designed around working as a power ECU relay and drive-by-wire.
34:09 They can be set up without CAN bus and just chucked in and they work off the bat.
34:13 Being a lot cheaper, it's a lot more considerable when you're only wiring in a few components.
34:20 Still, the price of four relays, four fuses, and a fuse block won't come to that sort of price, but you're getting that extra circuit protection, the capability to control the software and control how things work, and you're also getting diagnostics.
34:35 These also have CAN bus capabilities so they can talk to your ECUs and other PDMs.
34:40 In situations before, I've wired them in in the boot of a car where you don't really want to wire all your fuel pump powers coming from the front of the car where your PDM might be, but you have one of these small units right at the back.
34:53 They talk to the other PDM through CAN bus and they can switch things like fuel pumps.
34:59 Greatly minimizes the amount of wiring.
35:01 You go from having four, five, six, seven big thick power wires coming down for fuel pumps to just having a twisted pair of CAN bus and a power and earth for the unit and it can deal with everything from there.
35:14 But on that note, if you are going the relay and fuse route, there are better options than what I've showed you.
35:21 Those fuse blocks and inline fuse holders.
35:27 Like I said, I really don't like pre-wired stuff.
35:30 That's a bit of a personal thing, you might be able to do it neater and get a better job than what I do, but more often than not I like to have the terminals and be able to wire it in directly myself with my own wire so I know everything is up to the spec of what I'm wiring it for.
35:44 I'll show you on the computer here These are ones that I've used before and these are supplied by MTA.
35:52 They are a really good little fuse and relay unit.
35:56 They come in all these different modules that can allow for things like micro fuses, big mega fuses, different size relays, so there's all different types.
36:05 They can be packaged together for different situations depending on what you're doing.
36:10 It's just a much neater option.
36:12 You get the terminals.
36:13 Another thing I really want to specify or go on is when you buy these relay blocks they will have one terminal size so it doesn't matter what size gauge wire you're using, you've got to make it suit to that terminal which sometimes really isn't very nice to do.
36:27 You have a really small wire or incredibly thick wire, whereas these units will come with several different size terminals for those different wire gauges.
36:37 This just makes it a lot neater, a lot more reliable and in the end a better job.
36:43 So, if look here they use things like micro relays, but they also... one of my favorites is the ISO 280 if I get that somewhere... more micro relays... here we go.
36:57 ISO 280 relays and diodes.
37:00 Basically, these use the same pins on the relays as your micro blade uses.
37:05 I have one right here if we quickly go back to the whiteboard.
37:09 This is their ultra micro relay.
37:11 It's a 20 amp from memory and it works the same way as our four pin relay, but in a really compact situation.
37:19 If I compare that... I'll bring over our other relay... this is another four pin.
37:25 It still doesn't actually tell me what rating it is, but it's probably around the 40 amp.
37:28 So, it is double the rating, but you know in situations where you don't need that high level rating, you've got something small like this takes up a lot less room.
37:35 You can fit basically four of these in that same space and then you can get these relay blocks...
37:40 go back over the computer, sorry... that make it a lot neater.
37:44 And the advantage of these as well is they can be laid out in different ways.
37:48 Down here it's got a sample configuration.
37:50 You can mix and match this however you want.
37:52 I will note the pins do have an orientation, so they will have to be in this orientation.
37:58 The micro relay can't be put vertically or the fuses can't go vertically, but it still allows you to mix and match.
38:04 You could fill this whole thing up with ultra micro relays if you wanted.
38:07 The whole thing could be a fuse block and then have another one next to it for relays.
38:11 So, there are really good options for that kind of thing and you can make a relay and fuse setup nice and neat.
38:17 And when things are neat they're definitely more reliable, they're easier to diagnose and it's just in all a much more pleasant thing to work with.
38:27 It does take a little bit more time sometimes, but just like working with the software of a PDM, a little bit more time involved in it and you can work things out, work quick ways to do things, get your head around it and it does make it a lot easier.
38:40 Like I said with these they have different mounting options, so you can work out lots of different ways to mount it in your car.
38:46 We will note these aren't generally waterproof or weatherproof.
38:51 I don't think they have seals on the terminals, but they are the kind of design for inside of a car.
38:59 They also have things that make it easier like busbar terminals where you'll have a single power wire coming in and it'll crimp to one part of this busbar and that will actually distribute power across several terminals, meaning you don't have to individually wire each relay or each fuse with power source.
39:18 Do you need to take into consideration the total current that you're going to be putting through these? You don't want to exceed whatever the terminals are rated for by putting all that current through that one terminal.
39:29 Also one you've probably seen quite a bit are the busman relay and fuse blocks.
39:36 These again are a bit more of a professional solution, they definitely cost a bit more but they're incredibly worth it.
39:44 These are waterproof, weatherproof, when I say waterproof I'm not saying dunk it in water, but they have a rubber seal around it and the pins on the back have a rubber sealing as well so environmentally they are a lot better.
39:57 You can mount them in your engine bay and things like that whereas your standard fuse and relay connectors don't have that weather protection and that can be a cause of corrosion and failure.
40:09 Another good point with these is the different types of things you can plug into them.
40:13 Obviously, there's the relays but they have the circuit breakers, blade circuit breakers.
40:19 They come in a manually resettable or just a standard automatic reset.
40:23 You get fuses, fuses with little lights that turn on when they blow which is a nice little feature that I don't think I've ever used in my life but that's still cool.
40:33 Diodes and resistors which can be handy when you're wiring and things like for example I've wired in alarm systems with indicators, you don't want it backfeeding so have a diode in there and keeps everything nice and neat and not permanent and if you accidentally put the diode the wrong way around you can quickly flip that around.
40:52 So, like I said, relays, fuses, they do have their place.
40:58 They are definitely a cheaper, quicker option.
41:01 PDMs, they're more expensive but you are getting what you pay for and you're getting much more advanced technology.
41:08 It's again not new technology as it's something that's been around for quite a while and especially with transistors, the world revolves around transistors these days and if they were to disappear, everything would disappear.
41:19 So, it really comes down to a situation based decision.
41:26 It's going to highly be influenced by one, your wallet.
41:31 Just because you can't afford a PDM doesn't mean you can't do a good job.
41:35 Get a nice relay and fuse block, wire it up really nicely.
41:39 To be honest, I've seen some fuse boxes and relays that have been wired up quite impressively neatly and they're good to look at as well.
41:47 A nice aluminium case for a PDM is nice but also a well laid out relay block is just as nice.
41:55 So, I guess at the end of the day, is one better than the other? I want to say it's up for debate but I will say the technology in the aspect of cost and use case, they each have their place.
42:13 Relays, fuses, they're much cheaper, easier to use.
42:17 PDMs, much better technology, more expensive but you get what you pay for.
42:22 I think that's pretty much covered everything I've wanted to say.
42:27 I've definitely probably missed something but I think that gives you a bit of an idea of, I want to really bust down that whole relays and you don't need to use them anymore, there's no place for them, why don't you just build it with a PDM.
42:39 You might have a case where you need it.
42:42 I'll have a look at the questions now and let's see what people can stump me with.
42:48 All right, what have we got here? I have a Howtech R5 and PD16 in a rally car with a silly intercom and RaceLogic camera system having trouble with noise interference coming from the R5 when using one of the outputs to switch on the intercom and camera.
43:12 It only shows on the RCA from the intercom to the camera.
43:15 I've recently changed the R5 outlet to switch a relay and running the steelo off the relay direct from the battery.
43:22 Is there a better way of suppressing the noise interference from the Howtech gear? This is a bit of a long-winded thing just because it comes into noise and everything, which is basically a whole other topic in itself.
43:39 Again,, it's the kind of thing where higher-end PDMs and such will have a bit more noise suppression on those outputs and things like that.
43:47 The inputs of the cameras and intercoms should have some sort of noise suppression.
43:53 I'm trying to think off the top of my head what would be the best thing.
43:56 Things like, I will talk about just quickly, relays are prone to giving off noise in themselves.
44:04 If you saw the last webinar that I did, I talked about magnetic fields expanding and collapsing and that creates noise on a wire.
44:14 What your coil is doing every time you switch that coil, that electromagnetic field is expanding, pulling your switch closed, but then you switch it off, that field collapses.
44:24 That induces noise into components around it.
44:27 Relays are actually a really high noise source, especially if you're switching them on and off regularly.
44:35 I'm trying to think off the top of my head what would be a good solution for this.
44:38 So,rry, but I'm probably not going to be able to give you a straight-up answer.
44:44 It probably comes down to as well where wires are run, signal wires and the audio gear.
44:51 You've got to try and keep wiring away from main power lines.
44:56 Noise definitely comes down to...
45:00 It's there in a car, you can't really avoid it.
45:03 So,rry, the idea is you want to try and avoid it.
45:06 It's there, you've got to try and wire around it, do some things to suppress that noise.
45:11 It's definitely a whole subject in itself, so chuck that message on the forums or to our email and we should be able to get back to you and maybe other people might be able to help and come up with a better solution.
45:23 What have we got next? We've got MPG Racing.
45:26 What does a failure in a PDM show up like? Okay, that's another good point that I probably didn't touch on is failure points.
45:33 Like people always say, a relay or fuse fails and you see a blown fuse, you can pull that out, replace it and you're back on your way until you run out of fuses.
45:46 PDMs... I won't talk about a whole PDM itself failure because that is pretty rare.
45:52 You know, you're not going to end up on the side of the road with a busted PDM that's just decided not to work.
45:56 When a circuit does overload, what the PDM generally does is, internally with that transistor, shuts off that circuit.
46:05 And one of the big advantages with PDMs is those circuits can be designed where they'll retry that circuit.
46:12 Because sometimes you might have some really bizarre electrical problem that has overloaded that circuit briefly, just enough to blow a fuse or trip that circuit in the PDM and it doesn't actually return and theoretically you can just up and go again.
46:26 A PDM will have a programmed amount of retries and it will keep retrying that circuit and trying to see if it will work again.
46:34 If it does work, it'll just continue on as normal.
46:37 If it doesn't work, they will also have a feature where it'll shut that off completely, effectively becoming your circuit breaker or fuse, shutting that circuit off to protect everything.
46:47 When you cycle your ignition, turn your car off and on again, it'll reset back to the original state and it'll go through trying those functions again.
46:55 So, if you're on the side of the road, you've managed to actually fix the problem, you've rewired that spotlight that you accidentally wired up a little bit, ski whiff, and it's earthed out to your ball bar accidentally, cycle that ignition and everything's back to normal, you're on your way again.
47:11 For more critical circuits that you don't really want to keep trying, if it does overload, you want to shut it off and leave it shut off, you can program that in the software to stay shut off until you've actually gone into the software and said, hey, I'll fix the problem, let's carry on.
47:26 So, that's probably another huge advantage, is just the software allowing you to control these different aspects, allowing you to retry circuits, because the argument of a fuse blowing on the side of the road, if you haven't got any fuses, you're stuck and you're there trying to bridge the terminals with a paper clip which then becomes dangerous and genies go everywhere.
47:51 Hopefully that answers the question.
47:53 A full PDM failure, a lot of them, I'm pretty sure most, will have a failure state where certain circuits can stay on, but in general you won't have power to anything and it'll be like fuses, relays, when they fail, they're just done.
48:13 Next, we have Kentucky Hunter, Hunter spelt with a 3.
48:18 Any PDM recommendations for marine use? Marine isn't something I've done a lot with, there should definitely be some marine specific.
48:28 The biggest thing with marine is just environment protection.
48:32 You're going to have to look for something that can withstand being sprayed occasionally, that salt environment, a highly corrosive environment.
48:40 Generally, if you can seal normal PDMs in a unit that doesn't get all those weather effects, that can even be a solution.
48:49 I've seen a lot of boats that use car automotive gear and it's just taken extra care into how they're mounted, special enclosures to keep them from being damaged.
49:03 Andrew Z28, in your experience, what's the life expectancy of a correctly mounted PDM? I'm yet to see any that have really failed for any serious... if a PDM's failed it's usually because, like I said, it's been mounted wrong, it's been mounted too close to a heat source, it's been mounted at someone's feet and they've gone for a full drift and the passenger has stepped on it.
49:28 They generally don't fail.
49:31 I've seen one unit fail before, it was an older unit and from memory it was the main power solenoid, it had been bridged in a weird way.
49:42 I think that was more down to a quality situation.
49:46 One of the biggest advantages to transistors in electronics, they have a huge cycle life, they can be turned off and on millions and millions of times before they have any kind of degrading or failure.
49:58 And because that's what the PMUs, PDMs are based on, you get that life expectancy.
50:03 So, yeah, if you mount them right, wire them right, do all the right things, really they should outlive your car.
50:10 Andrew again, HowTech versus MoTeC.
50:12 I'm having a hard time justifying the 200% plus price difference.
50:17 Can you help? Is the money going to durability? Is it going to actual components inside the PDM as far as quality-wise goes? I've already heard that the HowTech is much simpler to set up.
50:28 Yeah,, so you've touched on a couple of things there.
50:30 I mean, I've had a bit of experience with the HowTech PDM setups and the MoTeC.
50:35 Yeah,, the HowTech is simpler as far as a software base.
50:40 You'll probably find if you really delved into the MoTeC, you probably get more out of it feature -wise.
50:46 If you're looking to do fairly simple automotive things, you're not looking to control things in a weird way or a different way and try new things, the HowTech will probably do everything you want it to do.
50:57 Something going up higher end, like the MoTeC, there's a lot of software differences.
51:02 It may look more complicated.
51:05 It's probably because there are more functions.
51:07 It's kind of like comparing a MoTeC Emtron ECU to the HowTech or something simpler.
51:12 It's just you're paying for extra features.
51:15 There are definitely internal differences.
51:18 I've never myself ripped open a MoTeC or a HowTech to personally compare, but generally a lot of the expenses when you're designing electronics comes into the quality of all those individual components, like the transistors.
51:31 They can vary from really low grade cents per transistor that probably won't last for too long up to full-on motorsport military grade that are designed to withstand really high temperatures, withstand vibrations, all that kind of stuff.
51:49 So, definitely the price has got to go somewhere.
51:54 Most of these companies, yeah, they got to make money somewhere, but they generally won't charge you a ridiculous amount of money for nothing.
52:01 There is some reason there for it.
52:07 William Ray's, or is it William RR's? William Ray's 4554.
52:12 Since you mentioned heat, is there a point where the heat generated could become a problem? I guess what I'm trying to say is if the PDM could be overworked or if you could run into issues if not set up correctly.
52:23 100%.
52:24 Mainly not so much from being set up incorrectly.
52:28 Generally, the design of them, the manufacturers will design it in a way that they will test it at its peak of whatever its total amp, which if you go into the data sheets of it, it will tell you a total amp draw of that entire unit.
52:43 If you're keeping at that point, you should have no issues with heat unless you've mounted it in an incorrect way, which again, manuals and data sheets, they will generally tell you what kind of things you have to do as far as mounting.
52:55 There might be a specified distance around the unit from where you mount it to other components or to main heat sources.
53:04 At the end of the day, yes, you can definitely cause situations where they will overheat.
53:09 They should generally also, for a good quality unit, will have an internal temperature reading.
53:13 It'll be able to log that, show you that.
53:16 It'll log it itself and have a look and if things get too hot, generally they should shut down and create a fault problem before it actually causes damage to your unit.
53:27 AndrewZ28 again, I'm loving all the questions.
53:29 Do you need any sort of fuser switch as protection on the cable straight from the battery to the PDM? I think this has just been a typo here.
53:38 Fuse switch as protection on the cable straight from the PDM.
53:41 Personally, whenever I'm wiring up a car, I will have some sort of main protection, a main circuit breaker that goes in beforehand.
53:49 If you're wiring, in the case of our SR86, these PDMs are mounted pretty much directly next to the battery.
53:57 There is a very short length of cable going to it and from memory, there is no fuse or circuit breaker in between that.
54:04 The only real time you're going to have an issue there is if that cable from the battery to your PDM becomes damaged in some way, it connects to an earth and causes issues in that regard.
54:15 As long as it's done right, technically you shouldn't actually need it.
54:18 But to be safe, I think the PMU16 has a total amps of 150 and chucking in a nice midi or mega fuse before that rated at 200-250 amps, depending on the cable that you've used, it's one of those better safe than sorry situations.
54:38 But at the end of the day, you don't really need it.
54:40 The main idea, if you have a look at a fuse box in a car, a lot of the time that cable is going to a main larger fuse elsewhere in the engine bay, or sometimes not fused at all, depending on how far the power cable goes.
54:55 If it's going straight to the battery, it'll just go to the distribution to your fuses and that is much like the PDM.
55:02 And my voice is getting sore.
55:05 But I think that is the end of the questions.
55:08 Uh, yep.
55:09 That looks like that is it.
55:11 So, hope this has been educational in some way.
55:14 I know there's probably a lot of things that I haven't touched on.
55:17 Things like transistors.
55:18 There are so many different types.
55:19 It goes quite in depth.
55:21 If that's something you want to look into, there's some really good YouTube videos out there.
55:25 It's something I wouldn't mind doing a, you know, some more content on as far as how that works.
55:30 So, hopefully I'll look out for that later on.
55:32 For now though, hopefully that has given you some sort of insight and helped you make a decision on whether you'll spend the money on a PDM or if you are going to be able to get away with just a relay and fuse.
55:43 Like I said, both things have their place.
55:46 There's a situation for everything.
55:48 At the end of the day, it's up to you and I hope you make the right decision, but it's going to come down to you and the information I've given you here.
55:56 Get out there and work on your own cars.
55:58 Uh, yeah, give it a go.
55:59 Come back to us with any questions that you have, jump on the forums, email us at support@hpacademy.com and I'll see you next time for the next webinar.