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### Topic: My ground is burning the arduino out! (Read 421 times)previous topic - next topic

#### Wawa

#15
##### Oct 21, 2018, 10:49 pmLast Edit: Oct 21, 2018, 10:51 pm by Wawa
Still have the problem that there is that 5volt on the TX/RX lines of an Uno all the time.
Connecting 5volt to the TX/RX pins of a Teensy might fry the Teensy.
No experience in Teensies though.

I2C is an open collector bus, and much more suited to join devices with different logic voltages.
Leo..

#### NenaGirl

#16
##### Oct 21, 2018, 11:15 pmLast Edit: Oct 21, 2018, 11:59 pm by NenaGirl
I think i found the arduino killer when measuring i found out that the 2 buttons IN where measuring -3 volts. Without connecting the teensy or something else. Probably a ground loop as mentioned by you guys!

Im going to look at it further...

Ill try to use the INPUT_PULLUP of the uno to connect it otherwise mayby this will solve my problem.

Nena

Edit:

Can it be that the cabel is making too much resistance that the pullup resister is not seen anymore as a damping but as a divider resistor, the cables are atleast 2 meters long so the travel distance is 4 meters. Just a thougth.

#### Grumpy_Mike

#17
##### Oct 22, 2018, 12:37 am
Quote
Ill try to use the INPUT_PULLUP of the uno to connect it otherwise mayby this will solve my problem.
Sorry no it won't. It is nothing to do with pull up resistors, solve it at source. What are these buttons connected to?

Quote
Can it be that the cabel is making too much resistance that the pullup resister is not seen anymore as a damping but as a divider resistor, the cables are atleast 2 meters long so the travel distance is 4 meters
No, the resistance of two meters of wire is negligible compared to a pull up resistor.

If that voltage on the buttons is AC pick up then use a 1K pull up resistor and a 0.1uFceramic capacitor to ground. Also put a diode cathode to input anode to ground to chop off any negitave voltages.

However all that would not point to blowing a hole in a regulator.

#### WattsThat

#18
##### Oct 22, 2018, 02:32 am
After you find out what's blowing up the Unos, you still have the issue that the Teensy 3.6 I/O is not 5V tolerant. A TXB0104 might be simple solution although I really want ask... what is the Teensy doing? I don't see any I/O connected. That's a lot of computing power for a serial connection.
Vacuum tube guy in a solid state world

#### NenaGirl

#19
##### Oct 22, 2018, 01:08 pmLast Edit: Oct 22, 2018, 04:07 pm by NenaGirl
Hi Guys,

Found the arduino killer! The +5v was probably shorten by the earth connection... I took a photo from the connections and made a new connection and sealed the earth. (is not needed there) (as you can see at the background!)

Thanks a lot!

After you find out what's blowing up the Unos, you still have the issue that the Teensy 3.6 I/O is not 5V tolerant. A TXB0104 might be simple solution although I really want ask... what is the Teensy doing? I don't see any I/O connected. That's a lot of computing power for a serial connection.
It worked fine with testing and let it run for seven days without problems, ill keep in mind that TXB brakeout! Thanks!

Uhm, there are only two rx/tx used now but there are 20 switches that need to be connected and 2 audio sensors and all the communications from the network are going to the teensy and from the teensy to the arduino.

EDIT:

It did the trick! IT WORKS

#### JohnRob

#20
##### Oct 23, 2018, 01:59 am
Before connecting the grounds again I would use a voltmeter between them and see what voltage is that is causing the current that is damaging the Arduinos.

To burn a hole in the regulator like the one that was shown in your photo is a very high current likely in the amps range.   You should check the 5v/3a v- compared to the common of the +/- 12 volt supply.  I think you will find they differ by a significant amount.

In addition, I usually in such a case I connect the grounds with a very small 100 to 200 ohm resistor with the belief that the resistor will fail before anything expensive fails.