I have an unpowered ATMega328 (Arduino Nano). What would happen if I sent 5V into its ground pin? All voltage supply pins would not connect to anything.

The 5V comes from a separate supply with no other connections to the Nano. Hence, I believe the voltage will have no reference and then no harm, no foul.

The Nano is used to drive several (6) LEDs. Two don’t work. I suspect that I miswired these two and want to test them. I’d like to avoid cutting them out entirely. So my test involves cutting the lead that is supposed to connect to the anode, feed 5V on the ground/cathode while grounding the cut lead. If it then works, I’ll cut it out and reverse the leads.

Am I going to run into problems?

 

It's your part so take my opinion with a large grain of contempt.

Seems like your analysis is correct. I would do it to my own part... though I would probably also ask here before I did!

 

2nd paragraph - yes, no harm.
You need to make sure you have the current limiting resistor in series with the LED when you apply 5V to it.

 

2nd paragraph - yes, no harm.
You need to make sure you have the current limiting resistor in series with the LED when you apply 5V to it.

That’s part of the reason I didn’t want to cut it out entirely. The LED and its current limiting resistor, is cast inside an object, otherwise I’d just look at which wire is connected to which end of the LED.

It’s a variant of Murphy’s Law. The number of miswired components is directly related to the how difficult it is to visually confirm the wiring.

 

If all the other pins not connected to ground you should be OK.

What kills parts is excess injection current into or out of a pin
by taking pin a Vbe or greater outside either power rail. That
can blow out internal bond wires, cause internal short between
Vdd and Vss due to triggering internal parasitic SAR, or cause
local hot spots that reach high enough temp to melt silicon. Or
enough current to migrate internal metal layer routes. Or HV
discharge on a pin, like static, that can cause Gate to
Source/Drain shorts of internal MOSFETs. Eg, rupturing gate
oxide of MOSFET.


Regards, Dana.

 

I have an unpowered ATMega328 (Arduino Nano). What would happen if I sent 5V into its ground pin? All voltage supply pins would not connect to anything.

The 5V comes from a separate supply with no other connections to the Nano. Hence, I believe the voltage will have no reference and then no harm, no foul.

The Nano is used to drive several (6) LEDs. Two don’t work. I suspect that I miswired these two and want to test them. I’d like to avoid cutting them out entirely. So my test involves cutting the lead that is supposed to connect to the anode, feed 5V on the ground/cathode while grounding the cut lead. If it then works, I’ll cut it out and reverse the leads.

Am I going to run into problems?

I am at a lose as to why you want to go through all of that trouble. Why not just apply power to the nano and write a quick program to test the LEDs? What do you mean you "suspect" you miswired them? Can't you just figure that out and know for sure?

 

I am at a lose as to why you want to go through all of that trouble. Why not just apply power to the nano and write a quick program to test the LEDs? What do you mean you "suspect" you miswired them? Can't you just figure that out and know for sure?

I’ve written several test programs. To “just figure that out” is why I am trying this.

This is part of a theatrical prop. The wiring to the part with the LED (and it’s resistor) is buried in a casting. Of course, the LED and resistor was tested on a breadboard. I wired the device (simulated candle)with a red and black wire, purportedly connected to the anode and cathode respectively. It is not outside the realm of possibility that I accidentally reversed the leads on one or two candles. Then it was soldered to the Nano and the test program executed.

Two candles do not work. Additionally, another digital pin, used to blink a status LED, seems to be non-working as well.

While the Nano has six PWM pins, apparently two are not working. Plus another digital pin.

I have another Nano. I plan on loading the test software and checking each pin with a multimeter. I double-checked the current draw. Everything attached draws 129mA. The highest pin draw is 18mA, well under the 40mA a Nano pin can supply.

I have 24 hours to get this working. Thanks for your help.

 

I did a simple setup on NANO and got the first 5 PWM outputs all working
correctly. Do not know why D13 is not working, as stated in Arduino ref manual.

void setup() {
  // put your setup code here, to run once:
  analogWrite(2, 25);
  analogWrite(3, 100);
  analogWrite(4, 25);
  analogWrite(5, 100);
  analogWrite(6, 25);
  analogWrite(7, 100);
  analogWrite(8, 25);
  analogWrite(9, 100);
  analogWrite(10, 25);
  analogWrite(11, 100);
  analogWrite(12, 25);
  analogWrite(13, 100);


}

void loop() {
  // put your main code here, to run repeatedly:

}

So I changed D2 thru D13 and got D2, D4, D5, D6, D9, D10, D11 to work as
PWM pins on the NANO. Not 7 PWMs, just the pins I could output to.



Regards, Dana.

 

I think the problem is solved. On a Nano, the pin numbering system is a little confusing. A couple of guys in the Arduino forum straightened me out.

I’ll get on the workbench tonight and rewire the Nano. Wish me luck!

 

I think the problem is solved. On a Nano, the pin numbering system is a little confusing. A couple of guys in the Arduino forum straightened me out.

I’ll get on the workbench tonight and rewire the Nano. Wish me luck!

Good luck!

 

Bingo! It works. Just got confused by the pin numbering on the Nano.

 

Looking for suggestions. Going to enhance this.

When the candles are “blown out”, right now I just shut them off. I want to sequence them, so they extinguish in the order by the distance from the actor that they appear. I’ll also extinguish then in groups. First, the closest candle, then two of the next closest on one side. Then the two farthest and finally (after a noticeable delay) the last recalcitrant candle. I might even make it so it looks like it requires another ‘puff’ from the actor.

Extinguishing each candle will be done with the following pattern:

• The candle goes bright
• A short delay where it looks extinguished
• It glows bright again
• From that level, it fades out over another short (very short) delay

What I’m asking is, does anyone have a suggestion for a sequence to simulate a candle blowing out?

 

I googled this, several hits - "arduino candle blowing out"


Regards, Dana.

 

Looking for suggestions. Going to enhance this.

When the candles are “blown out”, right now I just shut them off.

When I think of candles being blown out, the principle indicator is the movement of the flame in the wind. I know you can't do that, but, a kind of varying of the intensity as it is blown accompanies it. Maybe you can make that bit more dynamic.

I also wonder if you could use a mike, with a suitable high pass, to sense the blowing and have it react to that the way a flame would.