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Arduino Controlled Electrics


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#46 tiger99

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Posted 19 April 2017 - 11:13 PM

No, that DOES NOT COME ANYWHERE NEAR MAKING IT SAFE! There is no way of knowing what the Arduino may do as it is dying, and the most probable failures are due to software errors and transient upsets due to noise, neither of which you will be able to do much about. If you really must do something like this, it is ESSENTIAL that you apply all the principles of fail safe design to both the hardware and software. For a start you will need a safety critical microcontroller, which more or less means a Ti Hercules, as you will not be able to get the others in small quantities. And, even when designed by a fully competent team, with independent verification and validation, these will only achieve SIL3. And all of this needs far more expertise than one person at home can ever hope to achieve.

 

I have been designing safety critical systems for a lifetime, and if someone could do it, I could. But I can't, because I fully know and understand the risks and what is required to mitigate them, and it requires a large and highly competent team with a vast amount of hardware. For a start you will need an EMC test chamber and many hours of testing with all sorts of random interference to ensure that it never crashes.

 

No insurance company is going to pay out on an accident caused by home-made software.



#47 samg2007

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Posted 20 April 2017 - 12:46 PM

Thanks for your thoughts. Although I think you're missing the point here. All this system is doing is triggering relays, in a very similar way to how the normal light switches work. The one difference is that if the classic switch shorts or burns out, the lights go out. Here, if the arduino dies the lights stay on.

 

I'm not intending to mass market this, it's just a way for me to upgrade my wiring and no different to a homemade loom.



#48 tiger99

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Posted 21 April 2017 - 09:09 PM

Here, if the arduino dies the lights stay on.

 

And you have done a rigorous analysis to prove that? Compliant with ISO26262? With a single processor? What kind of hardware backup? You can't get SIL4 in software, and only barely SIL3, which as I said needs vast development resources.

 

It is very, very different to messing about with switches and wires and adds thousands of extra failure modes, many of which will remain unknown to you until one bites suddenly. You should save the effort for non-safety critical but useful things, of which there are plenty, and leave the headlights alone.



#49 samg2007

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Posted 22 April 2017 - 09:50 AM

OK,thanks

#50 Ethel

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Posted 22 April 2017 - 11:05 AM

I'm sure you could use a 4017 chip or similar in tandem with the 'duino as belt 'n braces. You'd still have the headlamp flasher too.



#51 Hedgey

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Posted 24 April 2017 - 05:37 PM

Great project man!! It's great to see diy developments like this and people contributing with ideas. Ignore the haters, you don't need a team of experts to create something fun and usable! Keep going, it's great project to follow!

#52 Mini Manannán

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Posted 24 April 2017 - 06:25 PM

Great project man!! It's great to see diy developments like this and people contributing with ideas. Ignore the haters, you don't need a team of experts to create something fun and usable! Keep going, it's great project to follow!

 

I totally agree, I love this kind of thing.  One of these days I'm hoping to be able to build something similar myself.



#53 samg2007

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Posted 27 April 2017 - 07:27 PM

Great project man!! It's great to see diy developments like this and people contributing with ideas. Ignore the haters, you don't need a team of experts to create something fun and usable! Keep going, it's great project to follow!

  

Great project man!! It's great to see diy developments like this and people contributing with ideas. Ignore the haters, you don't need a team of experts to create something fun and usable! Keep going, it's great project to follow!

 
I totally agree, I love this kind of thing.  One of these days I'm hoping to be able to build something similar myself.

Shhh, it's not a dead project... Don't let anyone know!

#54 tiger99

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Posted 29 April 2017 - 12:42 PM

Ethel, safety critical design is far, far more than adding a chip in parallel. For a start, the chips are running at some lower supply voltage, typically 5V, and a failure of the power supply will be catastrophic. There are THOUSANDS of failure modes to consider, and properly mitigate, in any safe design. The analysis would involve about 1000 pages of A4 and take a competent engineer, independent of the designer, 3 months of full time work.Then that would have to be confirmed by independent testing, including fault injection, and it would mostly have to be done again if the software needed to be updated, The analysis would inevitably produce unsatisfactory results, and so you would end up paralleling it with the main light and dip switches, so what would be the point?

 

Far better to be doing things like making the fuel gauge accurate, properly controlling the interlocking of fog lights with the headlights, replacing the troublesome hazard and indicator flashers, detecting bulb failures, maybe even monitoring brake temperatures, which can be done without the major safety consequences, and would best involve an Arduino. Loss of indicators, for instance, is only MAJOR, not CATASTROPHIC in the terms used in safety analysis, because it doesn't cause you to crash in a dark night on a twisty road, so the integrity requirements are much less. And there is only one basic precaution needed to make a better fuel gauging system using the normal sender. That is, limiting the voltage and current fed into the sender, even in fault conditions, to below the intrinsic safety limits.

 

And how about another Arduino idea, an average speed meter? If you come across average speed cameras at road works on the motorway, you press a button as you pass the first camera, and keep an eye on the indication, such that you pass the next camera with it showing 50 (or whatever limit is set) even when you may have momentarily exceeded it in between, to make up for being slowed down sometimes? That could speed up progress and save your licence. I would suggest a GPS module for the speed, but you can't legally use it as the main speedo.

 

But you CAN use an Arduino, and a sensor on the gearbox instead of the cable drive, as part of your official speedo. The Arduinos usually have an area of EEROM where the recorded mileage can be saved periodically, as that must be maintained even when the power is off.

 

Then there is control of the heating system, electric mirrors, synchronised independent wipers, wiper delay, monitoring of anything that takes your fancy, as on modern cars. Tyre pressure monitoring if you can fit ABS speed sensors to each hub, to sense the different speed of a deflating tyre. All in all there is plenty that you can do safely and legally.

 

But one thing you CAN do with the headlights is to use solid state switches instead of traditional relays, as long as you observe strict duplication between left and right. That lets you use TWO fuses instead of FOUR, one feeding left and the other feeding right. Safety requires that the left and right side switching is in separate boxes. The protected switches look after local faults, so you can feed each side of the lights with its own fuse from the starter solenoid, keeping the unprotected wiring as short as possible. But there is no software or complexity involved, the dip switch simply feeds control voltage to the solid state switches, which always have battery power. You would split the dip switch output 2 ways at the switch with resistors in the lines such that a short on one side did not affect the control signal to the other. The light switch and dip switch would only be handling tens of microamps, they might need a ballast resistor to load them up to at least 10 milliamps to keep the contacts clean. That scheme actually improves safety, because it has reliable redundancy, unlike the standard system, except for the light switch and dip switch. No software, no logic gates etc, only some resistors and zeners to protect the control inputs on the switches. The proper parts will be rated to withstand alternator load dump.

 

Is that enough SAFE ideas to be getting on with?



#55 carthorse

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Posted 01 May 2017 - 09:42 PM

Oh for heavens sake he's building this to go in a classic mini not a commercial airliner. It's going to be at least as safe as a crusty 25 year old wiring loom with corroded connections.
Tiger99, I think you've made your point - let it go but thanks for taking the time to worry
Samg2007, carry on because I really want to see how this comes out. I'm thinking of incorporating some similar ideas into my pickup build when I get to that stage.

#56 Big Sam

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Posted 11 August 2017 - 04:45 PM

Any more updates Sam? Quite impressed so far!



#57 mark-c

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Posted 22 March 2021 - 08:09 PM

Bit of a thread resurrection but just came across it when searching for something else.

 

I've just read through the thread and it was a very interesting read. Did you continue with this project Sam?..would be great to see any updates or where the project ended up. 



#58 jonlad

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Posted 23 March 2021 - 10:48 AM

and what happened to Tiger99? I dont see him around here any more  :unsure:



#59 Mini Manannán

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Posted 25 March 2021 - 07:54 PM

and what happened to Tiger99? I dont see him around here any more :unsure:

As I remember, he got ticked off by the admin team and that was the last we heard off him.

#60 samg2007

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Posted 01 April 2021 - 09:27 AM

Bit of a thread resurrection but just came across it when searching for something else.

 

I've just read through the thread and it was a very interesting read. Did you continue with this project Sam?..would be great to see any updates or where the project ended up. 

 

Hi, it's been a loooong time. I never really took this any further, but has always been on my list to come back to. Did you come across anything similar that has been completed?






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