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Topic: auto-reset does not work anymore (Read 523 times) previous topic - next topic

Stuggiduino

Hi there,
after experimenting with a LCD on my Arduino UNO  the Arduino board does not auto-reset when I plug in my USB cable. I have to push the reset button manually or (re)upload the sketch again. Even opening the serial monitor works fine to start the sketch again. When I tried to connect the LCD for the first time the UNO turned off (power LED slowly fading out), when I disconnected the ground cable again the Arduino turned on again. Do you guys know what that means?
I found out that a cable wasn't soldered to the LCD properly. After I fixed it everything worked fine. Is it possible that a short circuit damaged the parts that provide the reset function? I'm sure that it worked before.
Thanks for any help.

James C4S


after experimenting with a LCD on my Arduino UNO  the Arduino board does not auto-reset when I plug in my USB cable.

"Auto-Reset" in the context of Arduino means the existing sketch restarts from the beginning.  Is this how you are using "auto-reset"?



When I tried to connect the LCD for the first time the UNO turned off (power LED slowly fading out), when I disconnected the ground cable again the Arduino turned on again. Do you guys know what that means?

This means there was a short circuit somewhere.

There are two very bad practices mentioned here that you should avoid:
1.  Do not disconnect Ground, disconnect Power.  Ground is important.
2.  Do not change connections while your circuit is powered.  This will eventually lead to a mistake that will cause damage.
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

Stuggiduino



after experimenting with a LCD on my Arduino UNO  the Arduino board does not auto-reset when I plug in my USB cable.

"Auto-Reset" in the context of Arduino means the existing sketch restarts from the beginning.  Is this how you are using "auto-reset"?


Yes, that is how I understand the function. If I start the serail monitor or push the reset button, the sketch restarts. If I just plug in a cable it does not.



When I tried to connect the LCD for the first time the UNO turned off (power LED slowly fading out), when I disconnected the ground cable again the Arduino turned on again. Do you guys know what that means?

This means there was a short circuit somewhere.

There are two very bad practices mentioned here that you should avoid:
1.  Do not disconnect Ground, disconnect Power.  Ground is important.
2.  Do not change connections while your circuit is powered.  This will eventually lead to a mistake that will cause damage.


Thanks for the advice. I'll keep that in mind.

James C4S

#3
Jul 09, 2012, 04:41 pm Last Edit: Jul 09, 2012, 04:44 pm by James C4S Reason: 1
Okay, so that is not an "auto-reset" issue.  Plugging in the USB cable does not trigger auto-reset.

Instead, you have a "start" issue.  Does this also occur when no other hardware is connected?  (You may need to program the blink sketch to verify, so you can actually see something happening.)
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

Stuggiduino

Hi James,
thank you very much for your help so far.
Ok then, let's call it a "start" Problem. Sorry for misleading you.
I disconnected all the hardware and tried the blink sketch - works fine!! Thanks. The funny thing though is that the "problem" always occurs when I connect the display (5v/ground), even with the blink sketch. Is that some kind of normal behaviour of the Arduino. Seems odd ;)

James C4S

Do you have a link for the display?  It suggests it is causing enough of a load to prevent the chip from coming out of reset (on initial power up) properly.
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

Stuggiduino

Hi, I got this here --> http://www.sure-electronics.net/download/DE-LM010.pdf

Im no expert but at first sight everything seems normal , doesn't it?

James C4S

I don't think the LED backlight has a current limiting resister.   On power up it is probably drawing a significant amount of current (and damaging the backlight).

Try a 33-200 ohm resistor in series between the 5v and pin 15 of the LCD.  (or as a test, disconnect the backlight all together and see how the behavior changes.)
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

Stuggiduino

I already tried to use a 100ohm and 240ohm resistor but the backlight is barely visible then, thats why I always used it without any resistors. It's just not bright enough with a resistor in series.
But as a test I just tried a 1.5k ohm resistor and there is of course no backlight visivle anymore. But the start-problem still occurs, EVEN with the backlight completely disconnected. So the backlight is not the problem.

My setup is the same as in a tutorial from ladyada.net --> http://www.ladyada.net/images/arduino/lcdtut/bigpicture.jpg

thanks again for your help

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