Any raspberry pi-ists?

[Tinbasherdan]

This is a lot more complicated than you think, first you need to know the transfer function of the sensor voltages to the actual measured values, where will you get that?

It needs to be made robust for an automotive environment, the pi is not. You will indeed interface electronics designed to accommodate this so as not to blow up your pi.

You need custom code to interpret the voltages from the sensors and map them to actual values.

This is a lot of work and will be expensive unless there was a large market for the end product.

I did a project like this 15 years ago and it was a lot of effort.

I'm sure if you do a bit of googling you will find that someone else has already done it and has a solution. Much easier to start from a product that almost does what you want and take it from there.

The autoPi does almost what I want but with obd, which was essentially the question, how could I make the analogue sensors talk to it

 

[sako243]

If you're after an off the shelf version then Martin over on Defender2 I think does kits that make the normal sensors talk to a Puma dash which may do what you want.

 

[Tinbasherdan]

If you're after an off the shelf version then Martin over on Defender2 I think does kits that make the normal sensors talk to a Puma dash which may do what you want.

I imagine the puma dash uses some proprietary wizardry that’s not compatible with anything on the planet. It seems the sort of thing lr would do

 

[northwest]

How old a "landy" are we talking?

It's a blue one.

I'm sure if you do a bit of googling you will find that someone else has already done it and has a solution.

This^^^^^^. Stay away from re-inventing the wheel if you can.

 

[RaceDiagnostics]

The autoPi does almost what I want but with obd, which was essentially the question, how could I make the analogue sensors talk to it

If it doesn't have inputs for analogue signals (I dont know if it does or not) its not what you are looking for and adapting it to do so is unrealistic.

Google something like, "automotive display with analogue inputs", there will be solutions out there.

 

[Tinbasherdan]

If it doesn't have inputs for analogue signals (I dont know if it does or not) its not what you are looking for and adapting it to do so is unrealistic.

Google something like, "automotive display with analogue inputs", there will be solutions out there.

Even modern coolant temp sensors are surely analogue, so there has to be some way of converting that signal to something readable. Effectively what the obd system is doing, spitting it out in a digital format which is what the autopi is utilising. There must be a simplified way to make that bridge between the two

 

[Fastdruid]

If it doesn't have inputs for analogue signals (I dont know if it does or not) its not what you are looking for and adapting it to do so is unrealistic.

It does but the RPi GPIO is only 3.3v.

 

[Fastdruid]

Even modern coolant temp sensors are surely analogue, so there has to be some way of converting that signal to something readable. Effectively what the obd system is doing, spitting it out in a digital format which is what the autopi is utilising. There must be a simplified way to make that bridge between the two

There is but you have to convert 12v (and up to ~15v) to an acceptable level/format for the RPi to accept. Although that said, some of the sensors on modern cars are designed for 5v rather than 12v and are fed direct from the ECU rather than the "main" power.

I have a little bit of experience here, I had made my own design board to take an Arduino and add on CANBUS, a number of 12v analogue inputs and outputs. With them suitable isolated etc...

 

[ChrisBailey]

If it were me I would buy a digi dash, the tyoe used in kitcars and track day cars.
They are already setup to read a whole bunch of different sensors.

I wouldnt even consider doing it yourself with a raspberry pi, not unless you have years of embedded software development experience and electronics knowledge.
It can definitely be done, but its a massive job.
Youd have to basically implement a CAN bus, sample multiple sensor types and convert the analogue readings to a pretty accurate real world representation, i.e wheel speed, engine temperature etc etc.
Honestly not worth it.

 

[Dev]

How well would WiFi work from (say) inside an engine bay to cab?
4 wire serial connection could be done with alarm cable, or 4-core flex if you wanted something a bit "beefier".

Easy, realistically it only has to reach <1m. Assuming you don’t run the sensor wires (or the wifi antenna) back to the centre console and in that case - right next to the pi.

 

[Tinbasherdan]

If it were me I would buy a digi dash, the tyoe used in kitcars and track day cars.
They are already setup to read a whole bunch of different sensors.

I wouldnt even consider doing it yourself with a raspberry pi, not unless you have years of embedded software development experience and electronics knowledge.
It can definitely be done, but its a massive job.
Youd have to basically implement a CAN bus, sample multiple sensor types and convert the analogue readings to a pretty accurate real world representation, i.e wheel speed, engine temperature etc etc.
Honestly not worth it.

If I get a digi dash I might as well just stick to analogue gauges to be honest as it will then be back to a separate head unit, gauge bank, cb etc. I was hoping to condense at least the gauges and head unit into 1 if at all possible

 

[RaceDiagnostics]

Even modern coolant temp sensors are surely analogue, so there has to be some way of converting that signal to something readable. Effectively what the obd system is doing, spitting it out in a digital format which is what the autopi is utilising. There must be a simplified way to make that bridge between the two

That's correct but all cars use a custom programmed microcontroller to do this to take in the analogue signal and convert it into a value ( analogue to digital converted and firmware) that can be put out on the obd port or be used by the engine management to control fueling or injection etc or be displayed on the dash. There is no one generic chip to do this, all sensors have a transfer function that is catered for in the software, you won't know what that is for your car without getting the data sheet for the sensors on your car or characterising them yourself.

This is all possible to do, or hire someone to do, but it is not trivial.

Your better looking for a solution designed for this type of custom display. Then someone will have done the hardware design and software for you, you will then just need to teach it the transfer function for your sensors if they exist on your car.

 

[Tinbasherdan]

That's correct but all cars use a custom programmed microcontroller to do this to take in the analogue signal and convert it into a value ( analogue to digital converted and firmware) that can be put out on the obd port or be used by the engine management to control fueling or injection etc or be displayed on the dash. There is no one generic chip to do this, all sensors have a transfer function that is catered for in the software, you won't know what that is for your car without getting the data sheet for the sensors on your car or characterising them yourself.

This is all possible to do, or hire someone to do, but it is not trivial.

Your better looking for a solution designed for this type of custom display. Then someone will have done the hardware design and software for you, you will then just need to teach it the transfer function for your sensors if they exist on your car.

What sensors/senders on the car are moot to be honest, they can and indeed will be getting swapped out no matter what direction I go in, and I would think there would be some info on aftermarket ones available. Someone, somewhere must have done it. I fail to believe a fat sheet metal worker from Cumbria is the first person to ever consider it

 

[RaceDiagnostics]

I'm willing to bet there is a solution out there on the internet, just do a bit of browsing.

This is the one I did 15 years ago, it could either take in obd or be connected to sensors for pre obd cars. However it took me about 400 hours to get to this stage.

 

[ChrisBailey]

An option would be to fit an aftermarket ECU, something like a haltech. You can then fit a Powertune digital dash which would do eberything on a single screen.

Need deep wallet though.

Is your landy EFI or on strombergs?

 

[m_c]

What sensors/senders on the car are moot to be honest, they can and indeed will be getting swapped out no matter what direction I go in, and I would think there would be some info on aftermarket ones available. Someone, somewhere must have done it. I fail to believe a fat sheet metal worker from Cumbria is the first person to ever consider it

You won't be the first to consider it, but there is a reason why very few do it, and why aftermarket options will reflect the complexity in their price.

It may appear a simple thing to achieve, but there are lots of individual parts involved to make it fully functional.

 

[Tinbasherdan]

An option would be to fit an aftermarket ECU, something like a haltech. You can then fit a Powertune digital dash which would do eberything on a single screen.

Need deep wallet though.

Is your landy EFI or on strombergs?

It’s a big old dirty Cummins diesel, completely mechanical. I don’t need any info on engine speed or injectors or any crap like that, I just want to know it’s got oil pressure, what temp it’s running at, what air pressure I’ve got in the tank, and if I’m feeling especially fancy, boost pressure

 

[bigegg]

It’s a big old dirty Cummins diesel, completely mechanical. I don’t need any info on engine speed or injectors or any crap like that, I just want to know it’s got oil pressure, what temp it’s running at, what air pressure I’ve got in the tank, and if I’m feeling especially fancy, boost pressure

Do a search for pressure and temp sensors.
There are *thousands* of (maybe tens of) them that are basically " plug+ play - they take VCC (5V or 3.3v) + GND, and output a "signal" - either an anolog between vcc+GND, or digital binary, or serial i2c.

Its just a matter of plumbing them in, and connecting to your MCU. (raspPI).
Worst case, you can get "logic level convertors" or amplifiers(?) which will convert the 0-12V sensor to 0-5v(3.3v?) output. Most are available as self contained modules from bangood/AliExpress.

I'm not definite, but some MCUs have an "aref" pin - I *think* that means that the ADC will accept a value between gnd and AREF, rather than gnd+vcc.
Ie, connect 12v to AREF, and (on a 10bit ADC) you'll get 1024 distinct values on the input (signal) pin.
*THIS MIGHT BE WRONG *

 

[RaceDiagnostics]

I'm not definite, but some MCUs have an "aref" pin - I *think* that means that the ADC will accept a value between gnd and AREF, rather than gnd+vcc.
Ie, connect 12v to AREF, and (on a 10bit ADC) you'll get 1024 distinct values on the input (signal) pin.
*THIS MIGHT BE WRONG *

Connect 12v to any microcontroller and you will have a dead microcontroller.

 

[bigegg]

Connect 12v to any microcontroller and you will have a dead microcontroller.

ah. Is the AREF pin to only *reduce* the voltage range, then? I did say I might be wrong.

there are still easily available modules to change the voltage range, either way