Arduino Uno Resets On Triggering Of Second Relay


I have a problem with a pair of relays that I can't quite fathom.

I have an Arduino Uno wired up to a 6v battery and two relays. They're meant to turn on and off at various times in the day, without anything hooked up this all works fine.


With the devices installed (one 6v one 9v with a step up converter), after being off for a while the whole thing struggles to turn on again, it just sits there repeatedly trying to turn the first device on then taking down the uno.

If I leave it clicking on and off for a while eventually it sorts itself out but this can leave the device in a state where it thinks it turned the devices on but it hasn't.

I'm thinking some sort of power smoothing might help but I'm not sure about how to set this up, or could it be something else?

If usb is connected everything works fine.

Any help would be greatly appreciated.



Possible that you have made the unfortunate mistake of connecting something to the "Vin" terminal or "barrel jack". :astonished:

These are simply not useful/ usable for anything other than operating an Arduino with nothing connected to it other than a couple of LEDs with current limiting resistors restricting them to 20 mA. :roll_eyes:

If you do not propose to power the Arduino via the USB connector with a 5 V regulated power supply (a computer or a "Phone charger"), then you need to connect the same 5 V supply to the "5V" pin. What are you using for a 5 V supply?


Yes, I'm using the DC in jack.... I guess that's a mistake! The system needs to be battery operated

Power is provided by 4 D cell batteries that give out just over 5v