Sale ends todayGet 30% off any course (excluding packages)

Ends in --- --- ---

PDM Installation & Configuration: Electric Handbrake & Wiper Motor

Watch This Course

$149 USD $74.50 USD

Or 8 easy payments of only $9.31 Instant access. Easy checkout. No fees. Learn more
Course Access for Life
60 day money back guarantee

Electric Handbrake & Wiper Motor


00:00 - So far, through the body of this course, we've looked at the basics or fundamentals of the power distribution module and we've also learned about the way we can program a power distribution module to achieve certain functions.
00:13 We've also looked at some of the advanced functionality that we can incorporate in a PDM.
00:18 In this module though, we're going to look at how we can actually confirm and validate an output or a configuration before we commit to wiring it and this can be problematic.
00:28 Particularly with some of the more advanced functionality, we may find that once we've committed to the wiring harness and we've got everything installed, something doesn't quite work exactly as we expect so particularly with some of the more advanced outputs that we may want to function, it can be beneficial to spend the time and quickly make up a test harness for our work bench and actually make sure that we can control the output exactly as we expect, once we've confirmed that, we can then commit to the final wiring harness design.
01:02 So in this module, we're going to look at a couple of these examples and we're going to start with our electronic handbrake arrangement that I've got on the bench in front of me.
01:10 What we're going to look at here is how we can control an Audi electric handbrake mechanism.
01:17 Before we go too far I'll just cover off the electronics and the complexities that are involved with this particular configuration which on face value does seem relatively simple.
01:29 The unit we're talking about here or using here is an Audi electric handbrake and this is being installed on the back of a Toyota FJ40 offroad vehicle.
01:38 We've converted that from factory drum brake to disc brake and that creates a few complexities around incorporating the factory mechanical cable driven handbrake assembly.
01:49 Now we decided that the neatest solution here was to do away with that and go with the electric handbrake and I will just mention here that absolutely this is not the cheapest way of achieving this.
02:03 It requires, as we'll find, quite a lot of reasonably expensive electronics and if cost saving was your priority, this would not be the way to go.
02:12 However the reality is that cost isn't always the main driver with our decisions and particularly with the case of this vehicle, the majority of the electronics were already being installed so the extra requirements to drive the handbrake wasn't actually a big consideration.
02:28 Alright let's talk about the complexities of this setup.
02:31 So we've got our Audi electric handbrake and this is a simple handbrake that incorporates a normal hydraulic pressure driven piston as well as a servo motor that can drive the handbrake on and off.
02:45 It is a two wire device and the complexity here is that when the handbrake is engaged, one of the two wires is driven to 12 volts and the other to earth.
02:56 On the other hand when we disengage the handbrake, that is reversed.
02:59 We end up with 12 volts going to the opposite wire and the wire that did have 12 volts becomes ground so that allows us to drive that servo motor in either direction.
03:09 Now this creates straight away a complexity with our MoTeC PDM32 which is our power distribution module for this project because the outputs from this power distribution module, doesn't actually incorporate half bridge outputs, each of those outputs will only go to 12 volts when it is active.
03:29 So we can't switch polarity which is what this needs.
03:32 Now I will mention that yes there are some power distribution modules on the market that include half bridge outputs as well as conventional outputs which would allow this to be driven directly.
03:43 That's one of the things you do need to keep in mind when you are considering the purchase of a particular unit, making sure that you first of all understand how you're going to be driving the outputs and then choose a device that's going to be appropriate for those outputs.
03:58 In MoTeC's defence, I will say that including half bridge outputs on a power distribution module is certainly not the norm, albeit as I mentioned, yes there are models out there that do.
04:10 We'll probably see more of this coming in the future as well.
04:14 OK so that's the electric motor for the handbrake and the fact is at this stage, we cannot drive it from our PDM.
04:21 The other issue though is that we also need to understand how the electric handbrake is functioned.
04:28 This usually involves a little bit of digging into how the OE manufacturer did this.
04:32 We found that Audi use a current target.
04:36 So when the handbrake is engaged, the handbrake will be driven in the on position until it reaches a certain current.
04:44 In this case it's about 18 amps.
04:46 This is important because it ensures that we've always got a consistent amount of clamp from the handbrake.
04:53 Essentially you could look at it like the handbrake, or the current draw I should say from the handbrake motor increases, the more pressure is applied onto the brake pads so by targeting a specific current, we're always getting or ensuring that the handbrake is applying the correct amount of clamp load.
05:12 OK so the plus side is that our power distribution module is able to monitor current, the downside of course as we already know, we can't drive it directly.
05:20 How we're going to solve this requires two more pieces of electronics.
05:25 First of all we have a MoTeC dual half bridge controller.
05:30 So this includes, as its name suggests, two half bridge outputs.
05:34 We supply power to it, we can control it using our dash which I'll talk about in a second and then this allows us to either drive two servo motors in a single direction.
05:44 We can pulse width modulate it to control their speed or really what we're interested in is it allows us to drive a single serer motor forwards or backwards.
05:53 So that's our solution there to actually being able to do the polarity swapping to drive our motor on and off.
06:00 Remmeber though, we still need to do this current targeting.
06:04 So what we conventionally do with our dual half bridge controller is provide direct battery power to it.
06:10 Instead what we're going to do is we're going to provide the power to our half bridge controller from our power distribution module.
06:16 That then allows us to indirectly measure the current on those outputs from the PDM to the dual half bridge controller which of course is going to be the same as the current being drawn by the handbrake so that allows us to do our current monitoring.
06:30 So we're getting close.
06:33 The problem is we can't directly control our DHB unit from our PDM so we're using another piece of electronics to do some functions there which is our MoTeC C127 dash.
06:46 Alright things are getting a little bit complex but stick with me here and we'll see how all of this comes together.
06:52 The beauty of the PDM is that we are sending messages between the PDM and the dash via our CAN bus.
06:58 This means that the dash is able to monitor the current that is being provided to the dual half bridge controller.
07:05 Now what we're doing is using a table inside of the MoTeC C127 dash to target our current target that we want to achieve.
07:15 On the other hand, the MoTeC dash, we're using two of the auxiliary output channels to control the dual half bridge controller.
07:23 So how this essentially works is we've got a wired switch, in this case for our bench test.
07:30 Ultimately we would use a CAN keypad for this but just for a quick test here on the bench, this is a nice simple way of doing it.
07:36 That's to a digital input on the PDM, that's triggering our handbrake on and off.
07:41 When we switch the handbrake to the engaged position, what's going to happen is that the status of that input to the PDM is also sent to the MoTeC dash via a CAN message.
07:54 What the dash will then do is decide what to do with the dual half bridge controller.
07:59 When we switch the handbrake on, what it's going to do is provide an output triggering the on position for the dual half bridge controller and then engaging the handbrake and driving that servo motor but remember we also needed our current limit.
08:13 So we've got the current coming through to the dash, we're also using that as a user condition and when the current exceeds our preset limit, what will happen is that the dash will then stop driving the handbrake.
08:26 So basically in the PDM, we are using that to provide power to the dual half bridge controller.
08:33 We're using it to drive the handbrake into the on position for 3 seconds when it's triggered and it won't drive for that full 3 seconds but depending on where abouts the handbrake is in its cycle, we may need to drive it for a reasonable period of time.
08:49 So it's basically using two limiting factors, it'll drive for 3 seconds or until our current reaches our target.
08:56 Remembering we're trying to target around about 18 amps.
08:59 On the other hand, when we drive the handbrake off, we don't really need to be worried about current, the current draw is initially a little high but it's very easy to disengage the handbrake so that drops away pretty quickly.
09:11 So we're only driving it for a set period of time which is around 1 second and that means that we're backed off enough to provide no drag on the brake pads but we're still sitting there ready to reengage.
09:24 OK so again I know it is a little bit complex but let's dive into the actual electronics in the laptop and we'll see how this all works.
09:33 First of all in our input pins over here we can see we've only got a very simple configuration, we're only testing our one particular function so we've got A2, our auxiliary input 2 which is set up at the moment and we can see we've given that a channel name which is handbrake on and you can see that that is active when it's low so essentially when that switches to ground, it will be active.
09:55 So that's our trigger for the whole system, remembering that particular channel, the status of A2 there is what's also being sent through to our C127 dash.
10:06 Let's have a look at our output pins here and again very basic, we've only got our 2 outputs for our handbrake being run at the moment.
10:14 So we can see that those are on output 9 and 10.
10:19 We are paralleling these so that we have sufficient current handling capability.
10:24 So these will allow up to 10 amps per output and we can see that that's exactly what I've got that set up to be.
10:32 These are paralelled so essentially they're both doing exactly the same thing so we'll just dive into one of these.
10:38 And the condition with how this will work is it'll provide handbrake power, so that's power to the dual half bridge controller, that's the name of the channel.
10:47 And it will do that under these conditions.
10:50 So this is a pulse, so when the handbrake on signal comes in, it will on the rising edge, trigger this for 3 secconds.
10:58 So that's in the engage mode.
11:00 On the other hand, on the falling edge, we will end up driving it for 1 second so that's the disengage mode so remember that's the first part of this process but we still aren't doing anything with the actual current handling and we're not actually controlling the handbrake itself.
11:18 All that is doing, the PDM is simply providing the power to our dual half bridge controller which then in turn also allows us to monitor the current draw from the handbrake.
11:28 Alright that's pretty simple, let's jump into our C127 dash and we'll see how all of this works.
11:33 So first of all if we go to our auxiliary output pins we can see we've got two outputs and these are being sent out to that dual half bridge controller or they're wired I should say, these aren't CAN messages, to our dual half bridge controller.
11:46 We've got a simple setup here, one will become active when our handbrake is on and the other will be active when our handbrake is off.
11:56 Pretty straightforward but we're still not doing anything about our current handling capabilities.
12:01 Let's go into our calculations here and our user conditions.
12:05 I've got a bunch set up here which I want you to ignore, we're really only interested in these three at the bottom here.
12:12 So let's have a quick look at our handbrake on.
12:15 Alright so the handbrake on channel will become true when first of all, PDM input state 1 is true, so that is our switch, that's our handbrake signal going into the PDM, if you'll remember I said that that was being transferred through to the C127 dash as a CAN message.
12:35 So first of all when that's true and secondly, and this is the important bit, when our HB or handbrake current limit equals 0.
12:44 OK so pretty straightforward there.
12:45 When we haven't reached our current limit which we'll look at in a second, and the handbrake switch is active, we're going to be true on that particular condition.
12:54 Close that one down, handbrake off is essentially the same.
12:58 In this case, our PDM state, PDM input 2 state is 0, in other words it's off.
13:03 We don't need to worry about current handling in this particular condition though remember, that's not important here.
13:10 We're only going to be driving this for a set period of time.
13:13 The important part here is our handbrake current limit, we'll open that up.
13:16 And we can see here we are monitoring our PDM output 9 current and in this case, I've got it actually set up, there's a little interesting part here which we'll go over.
13:27 It is equal to or over 5 amps for a 10th of a second.
13:33 Now let's just break that down, you'll remember I said that the Audi handbrake is functioned to target 18 amps and 5 amps doesn't sound anything like 18 amps but we need to understand a little bit more about what's going on.
13:46 First of all, you'll remember that I'm paralleling the two outputs.
13:50 So that's 5 amps on 1 channel.
13:53 Within reason it's fair to assume that if the two paralleled outputs, if one of them is drawing 5 amps, we're probably going to have pretty much exactly the same on the other so that's 10 amps.
14:04 Still not at our 18 but there is a reason for that.
14:07 There is a relatively slow communication rate here between the PDM and the dash in terms of the current so we're not sending this at a very high rate.
14:17 So in order to actually arrive at approximately 18 amps, I found that setting a target of what ultimately is 10 amps worked out to be about right.
14:27 It's a little bit of flexibility in here, might not be 18 amps every time but we're within about +/- 0.5 amps which I'm absolutely fine with.
14:36 The other aspect there is I've got that delay in there of 0.1 of a second when we first bench tested this.
14:42 The inrush current when we first activated the handbrake was enough to trigger that 10 amp target so I just put in a small delay there, it's a round about way of getting us through that in rush current which only lasts for a 10th of a second or obviously less.
14:57 OK so that is our output there which we'll activate.
15:01 And the other thing is, because once that's activated it's going to stay active, we are deactivating it when our PDM input 2 state equals 0.
15:10 So in other words when we turn the handbrake off, it resets or deactivates our handbrake current limit.
15:16 OK again, I accept this is a relatively complex way of getting a handbrake to work and again, absolutely not the cheapest and easiest solution but it is an effective way of getting it done and sometimes you will be working with electronics which require a little bit of out of the box thinking.
15:34 The other thing I want to mention here is that this is not a black and white, this is the only way of making this particular unit work.
15:43 There's a variety of different ways we could have achieved this aim, this just happens to be the one that I'm demonstrating so don't for a minute think that this is the absolute only way that we could have got this result.
15:54 So anyway, let's have a look now at what happens.
15:57 So we have our handbrake at the moment in the off position and we'll switch our switch.
16:02 And we hear the motor drive for a second or so and then you can hear it load up and then it reaches the current liimit and it switches off.
16:13 We'll deactivate it now, remembering no current limit in that situation, it's simply driving into the off position and that's just time based.
16:22 Switch it on again and that's how the system works.
16:27 We can get a little bit more involved here so let's bring up our channels here in our C127 dash.
16:35 And what we'll do is we'll cycle through to the ones that we're interested in here.
16:39 Obviously a lot of information in here that is irrelevant and first of all we've got handbrake off and handbrake on so those are our statuses there and our handbrake current limit.
16:51 Now you can see at the moment that handbrake current limit is in value 1, in other words it's active.
16:57 We've just turned the handbrake on, it's driven until it's reached that 10 amp target and it's triggered and that's cut the output to our dual half bridge controller.
17:08 So what we're going to do is turn the handbrake off and what I'll get you to do is just watch what happens to the values here.
17:16 When I turn the handbrake off, first of all we're going to see the handbrake off status go from 0 to 1.
17:21 At the same time it's going to reset that handbrake current limit so let's do that now.
17:27 So we see that reverse, our handbrake off is still true, we'll now switch our handbrake back on and you'll watch the handbrake on go between 0 and 1.
17:37 Shortly after you'll see that handbrake current limit come in as well so let's have a look at that now.
17:43 There we go so we see our handbrake current limit hit one and that deactivates the handbrake.
17:48 Alright so hopefully at this point you've got a pretty good understanding of what's going on in a relatively complex setup but to go one step further, let's pull some logging now and we'll actually have a look at what's going on with our handbrake when we function that.
18:04 Alright we've got some logging downloaded out of the C127 dash and obviously this isn't what we'd normally use the C127 dash for but it is a really good way of validating exactly what's going on with our PDM so let's have a look here.
18:17 So first of all we've got our PDM input state for input 2, remembering that's obviously our handbrake on and off switch.
18:25 So we can see that at this point here, the handbrake was triggered on and at this point here, it was triggered off.
18:32 We've then got our next channel here which is our handbrake current.
18:36 Now I'm actually doing this as a math channel, remembering that there are two channels here and we want to add them up so this is the actual raw output from the PDM over CAN to the dash for output 9 and output 10.
18:49 Those were the two channels we'd paralleled in order to drive the handbrake.
18:53 And then just for interest's sake below, we've got our PDM total current.
18:57 Just while we're looking at this, you can also see the sort of square nature of this output and this is an indication of the rate at which the data is being transmitted across to the dash so no matter what rate we actually log at in the dash, that's not going to help and that's again why I said that we're targeting a slightly lower current than what we're achieving.
19:20 Anyway, looking at what happens here, as we trigger the handbrake on and we go from position 0 to position 1 on that switch, we can see that initially we have a really high in rush current which is what I was talking about needing to get around, we're almost pulling 20 amps but only for a really brief instant.
19:37 It drops away and this portion through here is where the handbrake is just starting to drive the piston up against the pads.
19:45 So there's relatively little current being drawn in this particular period under one amp.
19:50 Then we can see the current starting to ramp up as the piston pushes harder against the pads and we can see at this point here, which is where our handbrake current limit is triggered, we're actually pulling pretty much right on our target, 17.4 amps so close enough and we could always tweak that 10 amp target or 5 amp target as we see fit in order to just fine tune that and get it exactly where we want.
20:18 Good enough for our purposes of our demonstration though.
20:21 So at this point the current obviously drops back down to 0 because the current limit has been triggered in the dash.
20:28 The output to the dual half bridge controller is cut off so it's not doing anything.
20:33 And at this point here, we switch the handbrake back off, we can see that our current jumps up a little bit and in this case our peak current draw is around about 8 amps so much much lower than what we saw putting the handbrake on and we can also see that the current drops down quite quickly and at this point here we've got past our timer of 1 second and our handbrake function is complete.
21:02 By bench testing this function, it just gives us the confidence that first of all, we've got a strategy that will work.
21:10 And again there's no single way that we could have achieved this or gone about achieving this but it gives us the confidence that at least when we commit to the wiring, we know that once we get it in the vehicle, it is going to work as intended.
21:22 In some instances we may find that we simply can't get a solution that's suitable and we may have to either go with a different hardware solution or potentially rethink the entire way we're going about this.
21:35 In our second bench test demonstration here, we're going to be running through the setup and configuration testing of the windscreen wiper motor from the Toyota FJ40.
21:44 Obviously in the body of the course, Zac has already covered off some of the intricacies of wiring up and controlling a wiper motor using a PDM so I'm not going to really dwell on the same facts and information here.
21:59 However there are some intricacies with our FJ40 wiper motor that we do need to go through and we'll also talk about some of the control strategies that we are using here.
22:08 The problem with the FJ40 compared to the demonstration or information that Zac provided in the course, is that the wiring for this particular motor is essentially reversed.
22:19 Instead of having two power feeds for the low speed and high speed control and a common ground, the way the FJ40 wiper motor is wired as per the factory diagram, is that it uses a common power feed and earths for either the high speed or the low speed control.
22:38 Just as with our handbrake example we can't do this using our power distribution module.
22:46 Fortunately with a little bit of investigation, we could easily rewire the wiper motor to use a common ground and then use two power feeds.
22:55 The other intricacy with this is that the way the wiring worked once we've made this change, the park switch needed a little bit of rejigging as well.
23:05 This isn't too difficult to understand, it requires a little bit of investigation into how the wiper motor park switch worked.
23:14 Fortunately in our case, very easy to open the motor up and we can physically see the contacts for the park switch.
23:21 We could then rewire so that the park switch simply goes to a digital input on our power distribution module and then the other side of the park switch goes to a sensor 0 volt.
23:33 So that part now is completely separate to the actual wiper motor.
23:38 In our instance here, we wanted to integrate the control using a CAN keypad and we wanted to introduce a feature that wasn't available on the FJ40 which was an intermittent control for our wiper speed.
23:52 So we're going to go through how exactly we did that.
23:56 Let's jump into our PDM manager.
23:58 Obviously again we're using our PDM32 from MoTeC here but the functionality essentially is going to be very similar regardless what you are using.
24:06 So for a start we'll have a look at our CAN keypad here which we've got in the left hand menu and very simple here, we've just got one button set up.
24:14 We'll call that button wiper control and we are using the LEDs on the Grey Hill keypad here just to indicate what the wiper speed is so we can see that these are functioned off the following output channels.
24:28 We've got wiper.int for intermittent, we've got slow and then we've got fast, all pretty self explanatory.
24:35 So that's our actual input.
24:37 We'll quickly go through the function as well and just see how we ended up doing those output channels for our intermittent low and high.
24:45 So if we come across to our functions here in the left hand menu and click on that, we can see that we've set up a user function here called wiper speed control.
24:54 Double click on this and we're using this as a counter and as we can see here, minimum value there is 0, the highest value is 3 and what that's going to do is it's going to count up every time it sees an input on the rising edge for the wiper control button.
25:12 So every time we press that button, that counter is going to increment.
25:15 Once it gets up to 3, it's going to reset and go back to 0.
25:19 Alright so that's what we're getting with our counter there.
25:22 And then what we can do is use the counter to control or create each of these additional functions so in this case as you can see, wiper.int, that is true when our wiper speed control equals 1.
25:37 I won't go through the rest of them, they're pretty self explanatory, obviously as we count up we go from intermediate to low speed and then to high speed.
25:43 So now we've got our control strategy or our control inputs I should say, coming from our keypad.
25:48 We've also got those LEDs which we'll see in a second which gives us a visual cue as to what the wiper speed currently is.
25:55 Let's have a look at the outputs.
25:58 We'll go and click on our output pins here and we can see that we are using in this case output 9 and output 10.
26:07 Just as discussed in the body of the course, the PDM32 does require a specific output for the low speed winding which is output 9, that is why that is the two that we are using here so very important to understand that, otherwise we do risk doing damage to the PDM.
26:26 You want to also allow the braking function to work as intended.
26:30 Now if we double click here on our wiper speed low, the other element that we need to understand here is wiper control.
26:38 So this is again a special function, we'll click on that and we can see that we've got this enabled, just a point here, if you are dealing with one of the older MoTeC PDMs, this is a function that is only available on their version 2 hardware and above so if you've got a very early one, it's possible that the linked wiper control will not function.
26:58 Now we can see that we do need to choose the output that it's linked to for our high speed which of course is output 10.
27:05 We'll come back to our setup here and just have a quick look through this.
27:07 We've got our usual features here such as our current and our retry delay etc.
27:13 What we're really interested in is our functionality here which we'll go through.
27:17 So we've got a couple of elements that are going to be true here.
27:20 First of all, we can see our first function here is when our wiper slow is active or true, this output will function.
27:31 So obviously in our slow speed, we want that to function.
27:34 We've also got it set up for when our wiper is in the fast position.
27:38 Now this actually delinks the output 9 when the high speed is active.
27:45 This is for the braking function that comes in when we switch back from our high speed or switch our wipers off.
27:51 We've also got this function here which is our intermittent.
27:54 So you can set this up to whatever we want but we're using the flash function here, it's flashing when the wiper intermittent is true so when we've got that wiper intermittent function turned on that will be true.
28:06 It's going to turn on or go active for 1 second and then it's going to deactivate for 3 seconds.
28:12 That 1 second essentially is just enough to move the wiper off that park location and actually get it started.
28:20 It's going to essentially do one swipe with the wipers, it's going to then reach that park position and turn off again and it's going to wait for 3 seconds.
28:27 Now if you want to get a little bit more granular with this you could set up multiple different intermittent speeds just like we'd see with the majority of modern factory cars.
28:37 Then finally we've got the deactivation which is when our wiper parked is false, so when the wiper is not parked it will run, obviously when the wiper parked position, that switch is true, that will turn our wipers off.
28:54 So that's our low speed there.
28:57 We'll have a quick look at our high speed which is a little bit simpler here, we're only functioning that when our wiper fast is true.
29:04 So that's a bit of a rundown on the background there, let's now have a look at it actually functioning.
29:10 So what we'll do is we'll bring up our PDM monitor here, we can see that as we're sitting here, the wiper parked switch is true.
29:19 I won't go over the setup for that, it's a very simple digital input there, doesn't really need much more explanation.
29:25 So down here, we've got our wiper speed control, our intermediate, our slow and our fast so we'll be able to see those change from 0 to 1 as we cycle through the different positions and then of course up here we've got our outputs.
29:40 So let's just get this running here and we'll just hold this and we'll first of all put it into its intermittent position.
29:49 So we can see it does exactly what we'd expect, drives for a second, gets it off that parked position, then it disables for 3 seconds or becomes inactive.
29:57 We'll now go to our second position which is our low speed, now we've obviously got it running continuous, and we can see that the LED status changes and then we can also see that our current draw here's just a touch under 3 amps so obviously allows us to confirm our maximum current for that particular channel.
30:16 Let's switch our CAN keypad again, we'll move up to our high speed and we can see that our high speed becomes active.
30:24 We also check here, we can see that we've got around about 4, 4.2 amps being drawn, we can see there's no current draw on our low speed output anymore and then finally we'll switch our CAN keypad again and it deactivates, comes back to the parked position and stops.
30:41 So as I've mentioned, while we have already discussed wiper control, in some instances, like our FJ40, doesn't quite match the example that Zac gave and again just bench testing an item like this allows us to confirm that everything is working before we commit to the wiring.
31:01 It also gives us the opportunity to just work through some of the control strategy that we want to use before we commit to the final design and start installing our components.

We usually reply within 12hrs (often sooner)

Need Help?

Need help choosing a course?

Experiencing website difficulties?

Or need to contact us for any other reason?