[schwinn]

Great info in the video... good explanations throughout (as always with your videos!). I'm pretty good with electrical and I also have friends who are EEs that I can consult with if needed.

I guess the question is, what are you looking for? I presume you're looking for a way to replace/fix this unit? Since it's potted, I don't think fixing an existing one is in the cards for most people (though you may have the skills to do this, from what I've seen). You mentioned that the factory one uses coils... do you have detail on what those look like?

Hall sensors are certainly a better way to go, as they are off-the-shelf, usually far more durable. What you'd need is a linear hall sensor, which is designed to measure distances. Here's a quick description of how they work: https://www.electronics-tutorials.ws/electromagnetism/hall-effect.html

 

[schwinn]

Got it... makes sense.

Again, I think the temperature is attainable. I think the potting is the bigger task, but also doable.

Since you have the skills, tools, and transmission, you're certainly in a great place to perform the testing and work. I'm happy to help as best I can, and I think we can certainly put something together that could work. But you'll be the one doing all the heavy lifting, so it's totally up to you. I'm happy to help in whatever way I can. We can do this here or take it offline over email or something as well. And, like I said, one of my best friends is an EE, so I can pull in that resource... we often tackle crazy topics like this, so it's not out of the ordinary for us.

 

[schwinn]

I would try very hard to dig out one of the original sensor components from a defective module. It will likely have markings that can be used to identify the exact part they used, possibly through reference to an SMD marking code guide. At that point the job becomes a lot easier -- look around for a part with compatible specifications and a higher temperature rating.

Without knowing the original part number, it's going to be challenging to find a suitable replacement. You might find that a lot of different parts "seem to work," but not for long and/or not very well.

The original sensor is reported to be a coil, not a hall sensor. We're trying to make it a hall, as there is an aftermarket company who has done this. Our effort is simply to see if we can get there, publicly, so others can do this work themselves as well.

@jjrichar As for the spec. First step, are you sure you're getting 5V from the car-harness for these coils? If so, then yes we can run a 5V sensor... otherwise we may have to put in some voltage regulators or something. Can you confirm what voltage the car delivers?

As for actual components, I would get a few of them (they are low cost) and see if anything gets us close to start with. I think the key spec to watch is the temperature, to find something that is well tolerant. I don't think we can guess at the specs otherwise, since we're coming from non-hall to hall-sensors anyway... but after testing a few you may find one that works, or something that gives us guidance as to what is most important. For example, you mentioned the magnet feels weaker, so a "longer range" one may be needed, so that it's more sensitive to the weaker magnetic field. That's why it's best to grab a few and try them, I think. Be sure they're "linear" hall sensors, of course.

If you still want to dive into specs, then we can consider trying that... I'd need to know what distance we're dealing with between where the magnet is and where the sensor "would be" inside the potting.

It might be good to get a bad assembly, and clear out the epoxy so you can see what space you have to work with inside. This would also give you a way to build test assemblies and double-stick-tape sensors at varying heights or something, so you can try various distances as well.

I think this needs to be an iterative exercise, as we are going off-script for what the original part did... but I can dive into math if we really have to go that way.

 

[schwinn]

-40 to 150C is great... yeah, I'd say get a couple of those and run with it.

As you noted, initially speaking, it may not operate in the "direction" you want, and we can fix that. The first test would be to see if you can get it to have a similar "span" for voltage (regardless of direction/polarity) when at an appropriate distance (hence digging out space in an old part so you can space it as necessary).

Keep in mind that you may be able to change the direction by orienting the sensor in different directions - ie flipping it over or spinning it 180-degrees may fix that as well... but if not, it's easy enough to fix that with circuitry.

 

[schwinn]

For now, I wouldn't worry about the "optional noise filter"... chances are, there is filtering present in the car already, and if there isn't we can visit that later. The resistor is for "fault detection" which we don't need either.

The cap at the voltage input is just to provide some basic filtering from noise on the input voltage. On a bench, you won't likely have much of this anyway, but it doesn't hurt to have a cap to start out with. Note that it says minimum of 0.01uF. Since you're using multiple sensors, you can certainly go higher and use a single to cover them all. Whatever you have above 0.04uF would be fine, I'm sure... don't overthink it, haha.

Be sure the sensors are all wired parallel to the Vcc and ground... don't wire the sensors in series. (You said you were doing this, but I just want to make sure you keep doing it, haha.)

A few other comments from the manual:
1) Note that the device "switches" internally between two different operating voltages... and that changeover happens right at 4.5V. For this reason, I'd recommend getting a true 5V power supply instead of the 3x 1.5V batteries you've been using so far. A typical USB charger should be able to get you this (get a USB cable and cut the end, if needed)... you may have other options, of course. Ideally, if you can get a true benchtop power supply, that might be ideal... because the USB chargers can be VERY noisy.
2) Note there are 5 different versions of these sensors (A1-A5)... not sure which one you are getting, but be aware of this.
3) Section 8 in the manual is worth a quick read... they give you some guidance on how these sensors are intended to be used, orientations to the field, etc... something we should keep in mind as we work forward.

Our first step goal is to get the proper voltage range for the car's expectations. This is where spacing and orientation is important, so that's the first challenge - can we voltage movement at the ranges we have with the existing magnets. Once we get movement, we can adjust the voltage to meet what the OEM delivers via external circuits... so let's focus on the first thing - getting voltage movement.

One thing that might help is to test with the OEM part and see what the range is for the voltage. So, while you're waiting for sensors to arrive, put the OEM part back in, and see what you get for voltage ranges at varying shift positions. I don't recall if PIWIS will tell you this, but you can also probe this with a volt-meter if that's easier for you. See if you can record the min/max in actual operation for each sensor (remember, we want actual shift positions, not the full range of the sensor... so maybe you just do this with your working trans in the working car setup?) If you can't get them all, that may be ok... get what you can.

 

[schwinn]

DAMNIT! It's PWM?! Well, that throws a big wrench in the matter... I never expected that.

 

[schwinn]

Not your fault... I certainly never expected a PWM for such a simple signal!

 

[schwinn]

@jjrichar (and everyone else): I emailed my best-friend/EE over the weekend, and just called him this morning... he was in a meeting, so I couldn't dive in deeper, but he says that there are other electronics in that chip already and he believes that we can generate a 1kHz PWM from that chip directly. I certainly didn't see that in my quick reading, but I will chat with him later on and get more detail on it... so don't toss out those chips just yet!

EDIT: He may have been talking about a different variant of that product line, and maybe I misunderstood, but we'll see... I'll report back as soon as I have a chance to chat.

EDIT2: Ok, so his statement was that there was probably a timer chip (eg a 555 timer) inside the epoxy as well, that generates the PWM. He said it's stupidly-easy to recreate that for our 1kHz PWM if we wanted. But he's feels it's silly that Porsche would go through all that trouble, and he thinks they are probably averaging the PWM on the car-side of things, and using that DC level to determine position. If that's the case, we can skip the PWM and just use the analog DC-level ourselves, saving ourselves the hassle.

So, to test this, the suggestion is to feed DC voltages into the car, and read the positions from PIWIS, to see if they correlate linearly. If they do, then that's what they are doing... and we, too, can skip the PWM completely. So, if you have a bench-top variable power supply, you can simply use that to feed voltage into the car at a few levels (eg 1V, 2V, 3V, 4V) and record what the PIWIS readings are at each level. I can detail the wiring setup further if needed.

Alternatively, if you don't have a variable power supply, then you can use single, double, and triple-battery setups and do the same (ie 1.5V, 3.0V, and 4.5V). Again, I can detail the wiring if needed... but basically you want the negative on the shared-ground-wire, and the positive will go to whichever signal-line you want to test.

I this test shows a linear relationship, then we have our answer, and can skip PWM. If they are really using the PWM in the car, then these would all read "0" or some max value, since our battery/power supply is only putting in DC voltages (ie, there is no pulse).

DISCLAIMER: All of this should be safe to do, as it's low voltage and well within the input levels of these signals. However, we are testing and doing this "off the reservation" and mistakes can happen, so I don't want anyone coming after me for damage caused to anything. I would feel comfortable doing these tests on my own car, but if you mis-probe or miswire, I don't know what could happen and bad things might happen. I just don't want someone coming after me for damages (the USA can be very litigious!)...

 

[schwinn]

Ok, I'll sit back then since you have help in this now. I can contact my EE if needed, just let me know... but it sounds like you're on the right path!

 

[schwinn]

Needless to say, I fully support the open-source, DIY mentality. I'm a degreed Mechanical Engineer, but that's not a requirement of any kind. My best friend is non-degreed, but we share the same mentality that we can really fix anything. As my day job, I worked in the semiconductor industry on multi-million dollar machines (the ones in cleanrooms). We dealt with NANOscopic particles (which we detected and COUNT), toxic gases, high voltages (over 350kV) and currents (over 400A), high and low temps (down around 10C abolute temperature), vacuum systems that were down in the millionth-of-a-torr, ion beams, radiation, moving machinery, automation, signals of all kinds, etc. Then I worked in healthcare building MRI machines (superconductivity, low temps, radiation, etc). I also have over a dozen patents to my name, for various things I created in the industry. I continue to work in automation, and I have my own company where I work on PLCs, robots, automation of all kinds, etc. Hell, I even programmed all the way back to assembly-language on some chips, not that I care to do that anymore... nowadays, high level languages are much easier to work with, of course. Anyway, you get the idea.

You can't possibly tell me that a car has ANYTHING more complicated than any of these systems... but we worked on these day-in/day-out. And we made them safe to use for operators who don't have any experience (or sense, sometimes) with these systems. I have always been able to fix or design systems that worked... every project I ran had a successful outcome with a product or device that delivered the operation required.

There's nothing magical about the PDK. It's a dual clutch transmission... the only difference is that it has two clutches and a computer controller. Mind you, "computer" in this sense is a low-power control unit, far less complicated than the robots or PLCs I normally work on. The only complication here is the lack of documentation on it, and the weird protocols used on it (eg a PWM for the distance sensor). Sure, there may be a good reason for PWM... but no one will tell us. That doesn't mean we can't reverse engineer it... nor should we be prevented from doing so. It's not magic... it's just a signal.

In the end, with or without degrees, we can all learn to work with these systems... and that's the effort I will always support.

I'm not saying that a vendor can't do this either... as we can see, we have one here that can. And they can take as much profit as they want as well in a capitalistic system. That being said, it doesn't mean we can't come together and find another alternative as well.

As for the complaint about the pricing... IMO $1890 isn't that different from the $2k that was mentioned before, so I'm not sure the "alarm" is justified. Also IMO, if the product is proveded at a lower price to indys and such, that's great... but if we DIYers can't get it then it's a moot point. Why the (artificial) restriction? Again, these are my opinions on the matter, so feel free to disagree if you want.

EDIT: I just want to be clear. I'm not calling anyone out, attacking anyone, or anything like that. I'm just stating various facts. I am in agreement with other DIYers here (and everywhere) that I'm tired of being told that I need to leave anything to "experts". I'll concede that the designing engineer for any of this stuff could certainly be an expert. But the mechanic working at my local dealer? No way... he/she may have access to documents (again, hiding info is just stupid) and maybe more experience, but they are not all science/engineering minded... so if something goes awry, they have no clue what to do next. I, on the other hand, can figure it out... and so can many DIYers. I have fixed MANY issues with my cars that well-experienced shops couldn't figure out... and the solutions were VERY dumb and simple.

 

[schwinn]

Awesome to see this progress. Again, I'm here at the ready to help whenever needed. I don't want to get in the way or have "too many chefs" so I'm staying out for now. I will be reading and following the thread with interest regardless!

The times allotted to work has always baffled me. For example, my wife's Jetta (inline 5 engine) needed a replacement O2 sensor. It's ridiculously easy on that car because of the inline arrangement - you pull the plastic cover off (1 clamp on the intake hose, and the rest pulls off the rubber grommets)... and it's clear as day and easily accessible from under the hood. Took me about 30 minutes to swap. The shop wanted 3 hours and $400 to do this (part was $100). And I'm older and less experienced than a shop... I just don't get it. Sure, shops should be able to make money on it, but this seems silly...

Anyway, back to the point of this particular post, I wanted to highlight the right-to-repair movement going around in the USA. We passed it in MA (when I lived there) and it's now gaining traction as a national movement, so I encourage all of us to support it. Check it out here: Learn About the Right to Repair — The Repair Association There are state-level movements as well, so support those if you can as well... the more states that can make this a thing, the better it is for the national movement.

Granted, this won't likely help us on these older cars, but things like PIWIS and specialized tools are directly targeted by this movement. We should be able to get the info to repair our own cars (and other items like cell phones, computers, etc)... there is no reason for this info to be hidden as it is today, other than to promote scarcity and increase prices. I encourage everyone to support this movement, so that indy shops can get the tools they need, and so that even we DIY-ers may be able to access the tools we need. Nothing in a car is "rocket science".

I mention this because I was with a fellow Porsche person the other day in-person, as we tried to get his headlight module coded for this Cayenne. He had never heard of this movement. I couldn't believe it... so I figure, this is a great place to mention it. Spread the word!

 

[schwinn]

My guess is that the grooves may be there from an older design requirement? I think someone said these were used on many different vehicles, and potentially different transmissions as well? They could also be left there just to provide visual alignment, though that's an expensive way to do it, I suppose.

As for the plastic printed housing... I would be concerned with thermal cycling causing the plastic to crack over time? Remember, this part likely sees a lot of thermal cycling over time... while plastic will hold up to the temps, I question if it will hold up over time as well? But for initial testing, I see no reason not to run with plastic for now... easier to work with. Again, OEM was probably metal if this was an older design, since 3D printing wasn't as popular in the past (and certainly not in the automotive world).

I don't know enough about 3D printed materials to make a suggestion between the options you have, so I'll leave that to others. Don't forget about considering chemical resistance as well - I know ATF is typically pretty aggressive, chemically speaking... I don't know what the PDK fluid would be like, but just remember to consider that when choosing the plastic.

 

[schwinn]

I agree with the decision to use 3D printing for prototyping, and then a machined part for final "production". Don't get me wrong, there are applications for 3D printed parts in production... I work with many industrial machines that are setup that way. But for something tucked away like this and in a non-atmospheric location, I'd certainly stick with the OEM material if possible.

One thing you may want to look at, is to be sure to use the "right" potting material to prevent thermal expansion concerns. You're not going through drastic temperature changes, but it's good to check, just in case. I don't expect a problem, but better to look and be sure. Also, might want to see if the OEM part has any special ribbing or anything to help with the potting. I don't expect it does, but might not hurt to look there either.

Lastly, for the potting, are you planning to use vacuum to get all the air bubbles out? I would recommend thinking about that, as it ensures a good seal throughout the part.

Don't let me get in the way... you are all doing a great job! Kudos upon kudos!

 

[schwinn]

Excellent progress... great info! I'm glad you did the oven test... and found that it wasn't going to hold up as well as the specs say. Better to see that before it's in a car!

FYI, not that this is necessarily a solution for you, but when we wanted to "quench" some of the stray magnetic fields (back in my semiconductor engineering days) we would put a u-shaped iron on the magnet, so that the field had a "path" to follow. Basically, if you put a metal cap on the disc-shaped magnet in your picture, it might help direct the stray field and keep it from going too wide.

I think the angled sensor is the best idea for now, or moving them a little further away if you can. Or maybe specifying a "weaker" hall sensor component.

In any case, you're all on the right track for sure! Just wanted to give a few other ideas/options.

EDIT: Here's a picture of what using metal to "short circuit" the field looks like:

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www.researchgate.net

The article may be related, but I thought the picture was perfect to show what I was trying to put into words.

 

[schwinn]

Hey everyone. I'm just curious to know how this project is progressing? Not that I need it (I have a 987.2 MT), but I always love to see the fruits of such labors!