Need help !

Ive got this circuit for an Arduino Self Shutdown, but I am having problems turning the Arduino off by turning a arduino pin high on the bottom BJT transistror. Any ideas on what I am doing wrong?

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OPs circuit

but I am having problems turning the Arduino off by turning a arduino pin high on the bottom BJT transistror

How do you turn it ON?

As HIGH is OFF, when you go HIGH the power is disconnected, then the controller powers down and goes LOW so it powers up again?

You need to pull LOW to turn OFF, that is make the controller HOLD itself ON, HIGH!

Tom… :slight_smile:


I drew that momentary PB(red), when I push the PB the circuit turns on and stays latch. To tun off the circuit, I need to set the BJT NPN transistor to high. when I set the arduino pin to high on the base of the BJT nothing happens it seems like the arduino restarts but it does not turns off, but when I take my wire and make contact with +5V it turns off, but not with the arduino output pin. I also tired getting rid of the BJT and getting a jumper from the GATE of the MOSFET to a arduino output pin and setting that to LOW and it did not worked but when i got the jumper and touched ground it turned off. do you have any idea of what am i doing wrong?

Thanks for your help Tom.

I don't think you got what Tom said.
When you have an Arduino output pin, and there is no power on the Arduino, that pin looks like a LOW signal. Thus it turns your Arduino on again.


Do you think that changing that NPN to PNP and having the base of the PNP HIGH, and then to turn it off, set the output pin to LOW will work?

what can i do to make it work?

Thank you!

Do you think that changing that NPN to PNP and having the base of the PNP HIGH, and then to turn it off, set the output pin to LOW will work?

No, then you will never be able to turn it on.

I have a circuit with Mosfets transistors that latches powers when a PB is pressed, and when you ground the gate of the N Mosfet it turns it off, I used another PB for that. I wanted to use it with an arduino and turn it off with a output pin going LOW (ground). but that did not worked, so I used a NPN tansistor. My logic was when I turn an output pin HIGH on the base of my BJT transistor the transistor would work like a switch and it would let the base of my N mosfet go to ground, but it didn’t worked either. I can give it 5v+ to the base of my NPN transistor and it works but, it doesn’t work when I use the output pin HIGH on my arduino.
is it drawing to may amps? I need help.

Thank you !

What kind of load are you switching? The Arduino?

If a capacitor keeps the output voltage high, for some time, that voltage can keep your circuit active, as soon as the NPN base goes low again.


Yes, I am using an arduino to turn it off, but the output pin HIGH of the arduino will not turn it off! I can take a 5v+ wire from the same power supply that is powering the circuit to my base of my NPN transistor and it turns it off.

The weird thing is , as soon as my arduino turns its output pin HIGH, the arduino resets the internal LED on the arduino starts blinking and the program restarts.

do you think that the the output in HIGH is not staying HIGH long enough to shut it off?

Thank you

Are you turning the Arduino off? This won't work.

Yes, I am trying to turn the Arduino off. why not?

The Arduino outputs can have any (low) voltage when powered off. Then the caps on the board can turn on your flip-flop again. I'd suggest a simple flip-flop, with an added power FET to isolate and drive the load.

Why do you want to power off the Arduino, instead of simply putting it asleep?

Another suggestion to turn off the Arduino would be to use the Arduino as the latch. Modify your circuit such that it needs a hi from the Arduino to stay on. When you remove that hi output, the circuit will collapse.



It makes sense, Thank you! I will try that flip flop. And I do not want to use the sleep mode on the arduino because it might not be used in days or weeks and the sleep mode used some power right?



I will give that a try! Do you have a circuit diagram for that?


Is this the same as this?

You are being told here what you were told in the other thread....

Tom... :slight_smile:

@renearvizu, do not cross-post. Threads merged.


Can you please post a copy of your circuit of a hand drawn circuit in jpg, png?

Not the CAD simulator circuit you have been posting.

Include the Arduino and the power supply and the ON switch/button.

Tom… :slight_smile: