Hi, is my first timpe posting on EEVBlog forum and I ended here with my problem because I think is my last place to receive some professional solution for my problem.
I am working on a project with ATmega 328P for a vacuum cleaner to a self service and I made all the electronic needed for the project. The software was made by a close friend because I am not a pro in this teritory. All good and working as expected (I made some rigurous tests before) untill I put my electronic inside of the vacuum cleaner.
The screen (LCD 2x16) stoped responding but in a random maner. I will put some pics down with the weird screen that I have problems with. I created more then 10 prototipes and some of them reacted a bit different (it works for more then 30 operation until it chrashes) (I think is all about the manufactoring process).
My first impression was that I have an EMI problem because of the big mottor (3kw) that has to starts and stops by the commands of ATmega. For this reason I put some resistors (6 x 1k) on top off the display to the data lines (register select, enable, D0, D1, D2, D3) closer to the Ic of the screen in order to make the signal stable during the instructions, but this is not all the story. In concluzion the problem is: the glici was a persistent but with more operation as before. So I decided to disconected the mottor and restart the application. It didn't work.
The second impression (without the 3kw motor) was that the power supply (all power supplies was brand new from manwell) was not well galvanic isolated and I have parasitic ac voltage because I was zziped durring the tests. Afterwards I found that between neutral (from the power supply) and the negativ terminalI have almost 387V
(tested with my oscilloscope picture down below). After I changed the power supply I had my third impression because the problem was the same.
The third impression: My door from the vacuum cleaner is stainless steel and is grounded to the power supply grid (PE), I put some aluminium foil to shield the entire electronics during the operation and the screen just stopped responding like before without touching any button and the relays from inside starts and stops without any meaning...
Please someone who has any ideea what is happening?
I'm prepared to put the electronic inside an aluminium case and connect to the the ground of the sistem withot touching the ground off the power supply grid in order to make a Faraday cage. Is this going to work?