Thanks everyone for your continued input.
I’m not sure if it’s the way I’m reading this or not, but I’m sensing that I’m being flamed for asking questions on this forum. I am a newbie, so please go gentle. But, I’ll assume that it’s the way I’m reading it.
Judging by some of the replies, I think somewhere along the line I’ve managed to confuse the situation, so I’ll try and straighten things out. I have a 1988 VW Golf. I have a rear differential from a 2002 VW Golf 4Motion. I’m trying to put the two together. My 1988 Golf has none of the wiring or sensors used by the 2002 VW Golf donor car. So I’ve done my research as best I can to find out how the diff was controlled originally. Haldex, the company who make the diff and supply the controller to operate it to VW, don’t publish too much info about how it works, hence finding the inputs, but not a lot more. Given that, all I can do is recreate the sensors however I feel best.
I can code, albeit mainly in VB and SQL, not C. But, hey, we can all learn and I have been working through the samples on the main Arduino site. Unfortunately, electronics is something I know little about, which is why I'm here. I have no intention of creating this project and throwing it in the car and taking it out for some high speed testing, hence why I asked about being able to recreate inputs on a PC, so I can test various scenarios before heading off for some testing away from public roads.
So, back to the project….
A bit of research suggests VW ABS sensors return an AC voltage that rises with wheel speed. Guessing that has to be analog?
I'd question the research, then. There is very little AC stuff on automobiles, unless you are referring to air conditioning. AC and Arduino do not go together.
As per JesperKonge’s comment, it would appear it is AC. Chatting to a friend he mentioned that there is a way to convert AC to DC using a 4 way phase rectifier and a smoothing capacitor? So, it is possible to work around it. Only thing is, I'm not sure if it is an AC voltage or frequency change from the ABS sensor. Can anyone help? I can then monitor the feed from each wheel, and when one wheel's feed exceeds a specified threshold, we can assume we have wheel spin and activate the stepper motor.
but I'm guessing that the original ECU is converting a signal from a potentiometer mounted on the steering column. As I'm not using the original ECU, let's assume it's an analog reading from a multi turn potentiometer.
No, let's not assume that. Go look in the car and see.
There is no point, as I have nothing on the car. The steering wheel angle will be calculated by whatever I fit. So, once again, let’s go with JesperKonge’s comment and go with an encoder.
Again, the engine output is delivered from the original ECU and I have no idea how.
Seems to me that you are dead in the water, then.
Well, no. Not really. As mentioned before, I’ll make this first version a reactive system, rather than proactive. This means I’ll wait to detect wheel spin before engaging the diff, rather than trying to predict when it will spin and proactively engaging it before it does. We’ll save that for V2. Don’t want to over complicate my first project now, do I?
As I'm not using the original ECU and having thought about it, I want to make my life simple, lets ignore this one for now.
Ignore the whole project? Good idea.
Why did you copy just that bit? On it’s own it means nothing. In context it means, let’s not worry about the engine torque figure input, for reasons outlined above.
I don't think you know what all the inputs are - type, format, range of values, etc. However, it is likely that they can all be emulated in software. After all, the inputs are just numbers.
That’s true, I don’t know what the inputs are. That’s why I’m here, looking for guidance from you guys. As I say, electronics are new to me and I’m willing to listen to your suggestions in order to learn and complete my little project. So how can I recreate the inputs then?
As for running the inputs through the code, the obvious question is "What code?".
I’ll have to write some code for the Arduino in order to produce an output based on the inputs. I haven’t written anything yet, because without having inputs, or being able to recreate them, I can’t start. This is why I’m here in the first place.
Yes, you can see the outputs that you produce. Whether they are even remotely close to what the original controller produced, or not, I couldn't even begin to guess. I have my doubts that you could, either.
They don’t need to be anything like the original, as I’m not using anything from the donor car, other than the diff. So as long as I can deal with the inputs from the components you guys suggest/I select, I’m up and running.
Let's see: new to Arduino, new to C? Noisy electrical environment, multiple inputs, implying somewhat complex code. That code to control a mission critical system, such that bugs may have life threatening consequences. Lack of knowledge about how the cars systems work.
Again, feel like I’m being flamed here. Why do you feel the need to do this? Yes I’m new to Arduino. Yes I’m new to C, but let’s be honest, coding in C is not that difficult. Mission Critical system? Well, no, not really. The car runs front wheel drive for 99% of it’s life. The rear wheels are only engaged when the fronts loose grip. So yes, if it cut out mid corner at 100mph, then it could be nasty. But, am I really gonna build something and then make that my first test? No. That’s why I want to create a testing environment on the PC, alter inputs and make sure the code doesn’t do anything silly, before going and testing in the real world away from public roads. I understand the concept of the system, and that’s all I need if I’m not using the original electronic components.
I do like the idea of data logging though. Might include that. No need for the comment about my relatives being able to decipher the exact cause as to what killed me though. That’s not called for.