Hello all !
So I was wondering how you design your circuits for a car. I mean vehicles are very harsh environment for electronics.
I am actually trying to create an alco lock system that renders car immobile when alcohol level is above some limit.
My plan is to break the circuit to the starter until driver blows into the mouthpiece. After that necessary actions are to be taken (either keep it open or close so that car may start).
I dont think traditional components are heavy duty enough.
Please share your thoughts, ideas and experiences.
Thanx !

 

If you de-couple the circuits and use shielded enclosure for the circuit I see no need to seek out anything but normal off the shelf components.
Max.

 

Suppressing load-dump transients (positive and negative) and avoiding temperature excesses are essential.
Components specifically intended for automotive applications are available.
Component and connector mountings need to withstand severe vibration.
Wide margins should be allowed for voltage and current ratings.

 

If you de-couple the circuits and use shielded enclosure for the circuit I see no need to seek out anything but normal off the shelf components.
Max.

How to decouple the circuit ? By caps ?
Anything special required for shields ?

 

Hello all !
So I was wondering how you design your circuits for a car. I mean vehicles are very harsh environment for electronics.
I am actually trying to create an alco lock system that renders car immobile when alcohol level is above some limit.
My plan is to break the circuit to the starter until driver blows into the mouthpiece. After that necessary actions are to be taken (either keep it open or close so that car may start).
I dont think traditional components are heavy duty enough.
Please share your thoughts, ideas and experiences.
Thanx !

If you need to ask on a forum then you don't have near the skills to design something like this. What are you going to do when the car does not start due t there.

 

Hello,

Perhaps the following books on the internet archive might be of use:
https://archive.org/details/fea_Automotive_RFI_Elimination
https://archive.org/details/ERIC_ED318916
https://archive.org/details/springer_10.1007-b101849
https://archive.org/details/springer_10.1007-978-3-642-72146-5

Bertus

 

Suppressing load-dump transients (positive and negative) and avoiding temperature excesses are essential.
Components specifically intended for automotive applications are available.
Component and connector mountings need to withstand severe vibration.
Wide margins should be allowed for voltage and current ratings.

Taking all of the above into consideration you want to design what is commonly called a "blow and go". With today's automotive systems this involves disabling things like ignition and fuel supply, I suggest you not worry about the starter. The alcohol sensor needs some form of calibration for the Go or Not Go. Then features like during Go after a period the user must blow again as I typically enjoy drinking scotch doubles or at least a beer while driving. Drinking and driving is just a lifestyle for me.

A good blow and go really annoys me as I get tired of asking friends to blow so I can drive my truck and I also hate the ten min. warnings to blow again after I am driving for awhile. That is so annoying.

Seriously, you need to sit down with a real sharp pencil and a plain sheet of paper and start defining exactly what you want to do, then determine any sensors and a calibration method. That done how to interface with an automotive system computer or ECU.

Now please excuse me as I enjoy my scotch and I also need to get to the store to buy more scotch. Thank you and have a nice day.

Ron

 

The operating temperature range for automotive electronics is large. Consumer grade (+70 C) is not good enough. +85 C is 185 F. The passenger compartment of a dark-colored car parked on a city street in Arizona with the windows rolled up can exceed that.

ak