USB disconnects in automotive environment....

Peter Jakacki · 2016-06-26 17:46

You would need a better scope to detect glitches and noise and it's a pity that you can't lay your hands on one to see what's going on. However as I pointed out you would only need to do this if the problem persists and the idea of adding the isolated DC/DC converter was to eliminate the power supply and its ground as a problem. So don't go thinking you have to fix everything before you actually check anything. Just hook up your grounds as you would and check it. If it doesn't disconnect or play up then who cares if all the rest isn't quite right.

If it still plays up then take photos of your board wired in and maybe a couple of other shots that would give anybody on the other side of the planet an idea of how it actually is wired up.

eagletalontim · 2016-06-26 18:25

If I could squeeze out a bunch of money on a nice O-Scope, I would love to do it. They are just way too expensive for me

The USB disconnect is a very persistent issue and happens all the time when connected to a vehicle, just at random times. I believe it has to do with environment noise since I can bench test my device running from a single 12V battery and not have any issues. As soon as I put the circuit on the vehicle's power, it disconnects the USB consistently. This leads me to believe the issue is power filtering on the low voltage side. The only thing that happens is the USB disconnects. The Prop and all the other items on the board still work reliably. Since the circuit works, I feel like I have accomplished a bunch, but now there is a glitch that I just can't figure out how to fix with my current knowledge.

Each pin on the header is named for what it does. If you hold your cursor over the pad, it will display what it is connected to. This is how it is connected in the vehicle and bench tests.

Peter Jakacki · 2016-06-26 23:00

Have you connected the DC/DC converter yet?????????

eagletalontim · 2016-06-26 23:20

No, I have not bought one yet.

Peter Jakacki · 2016-06-27 00:15

!@&^#%$%#^! - this is the first step that is also the easiest, no need to talk about grounds and scopes unless you decide not to use a DC/DC converter and try and make it work as is but that is still too much guessing for me from this end.

eagletalontim · 2016-06-27 00:59

I was under the impression that the DC to DC converter would cause an issue and make reading of other sensors that are being fed voltages from an outside source no able to be done since there is no common ground. This is why I did not order one yet. Plus, there is a minimum order on Digikey and I would have to pay shipping too. If the DC to DC converter would be what I need, would there be anything else that I would need along with that?

Peter Jakacki · 2016-06-27 01:24

I know other people say other things and there may be other issues anyway but rather than being confused and not knowing what to do you must eliminate possible causes of your problem and if you take this approach with a converter even with minimum order and shipping then surely this is "cheap" compared to redoing the board and buying a better scope etc. I will give you a link to a better converter or an alternate supplier as I am only talking about a few bucks anyway.

Everything costs and as the proverb says that before we start building a tower we should count the cost otherwise we just look foolish. Always expect any project to cost more and take longer than you planned, then you will be prepared to do what's necessary to complete it.

btw, if you decide not to follow a recommendation for "some reason" then at least communicate this back as this project has gone way over the time I would expect to allocate, and a lot of that is because you haven't applied the advice that you are asking for and was given freely.

eagletalontim · 2016-06-27 01:52

I did want to try the converter since it seemed to be a logical decision to do. Since I have never messed with an isolated DC to DC converter, I can only go by what others are saying. The issue about isolating the ground came up and I did not see a reply stating this would not be a problem at all or if there was a problem, I could simply use "X" component to fix the issue. If I needed to order "X" component, I should do that on the same order instead of paying shipping twice

Just trying to keep all the ducks in a row right now.

eagletalontim · 2016-06-27 23:32

So should I go ahead and order the DC to DC converter and hope for the best that I have all the parts needed? I don't have a bunch of money to be ordering parts all at different times. Sorry for being a pain, but I just don't know what I am getting into. Common sense tells me that if I isolate a connection, the outside voltages that are fed from the vehicle's ECU to the isolated ground of my circuit will not be a complete circuit.

feng · 2016-06-28 10:45

eagletalontim · 2016-06-28 12:42

The names of each component are automatically given in the Diptrace software. Not everyone use the Diptrace software and are used to their own program. I am used to Diptrace and I know how to get a complete list of all the components I have used as long as I put the part number in the certain field.

Yes, I ask a bunch of questions and sometimes the answer given is not the solution, but I just give up on the whole project because people get frustrated with me because I don't do everything by the book as though I went to college for electronic engineering or something. For this issue... the USB disconnect has been brought up a LONG time ago and bring a really dead thread back to live is frowned upon sometimes. The answer was given in that thread that the shield of the USB cable needed to be separate from the ground plane. Other random things were thrown out there like the ferrite bead, but since there are hundreds of thousands to choose from, how could I possibly figure which one would be best for my situation? Yes, Peter has given me a value to go by and I do plan on redesigning the whole board yet again to accommodate for the additional components on the UART that I did not know should have been done that way and what values to use. Once again, I am a hobbyist.... not an electronic engineer.

I am not selling this product at this point due to all the issues. I actually used this product for over a year in my own vehicle and worked on fixing different things hence all the other threads. Most of those are resolved and I don't have to ask the same question again thanks to the helpful people who understand I am limited on knowledge of certain types of components and circuitry. I know enough to be dangerous, not enough to pick components I have never used out of thousands of others and know it will work for my application. I would love to get to that point, but without going to a technical school or college and spend thousands of dollars to educate me for a hobby I have, it is not worth it. So I have to ask and hope that what is replied works so I can learn from the mistakes I made from the beginning.

Genetix · 2016-06-28 18:57

eagletalontim,

I hate to tell you this but you are actually still early in the Product Life Cycle.
It's good that you are doing long term testing and at this stage making changes is cheap compared to later on.
As Feng mentioned when customers start returning product then changes become costly.
Since a vehicle is a very noisy environment you want to employ EMI reduction techniques, a few of which you have mentioned.
I would start with Peter's suggestion since power line noise is a very common issue. It's also not uncommon for electrical noise to travel through a vehicles electrical system since all that wiring acts like a large antenna.

Feng also mentions Reference Designators which is Electronics 101. Assemblers and technicians learn this stuff.
J is for Headers and electrical connectors while U is for ICs (Integrated Circuits).

USB disconnects in automotive environment....

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