I built an Otto robot based on an Arduino Nano board and powered it with a 9 V block battery and everything worked as intended.

I'm currently recreating the project with a group of kids, but we only had Arduino UNO boards available. I did not think anything of it... but now when I have uploaded the sketch and switched it on to run (only) from battery power, the UNO just makes ticking noises and flashes its lights. The battery is connected to VIN and GND, and cables run from 5 V and GND to the servos.

I understand that the ticking indicates the power is too low, but the exact same setup works with a NANO... so do they consume power so differently?

Another problem: if I just connect the battery to the servos and power the board via USB, the servos will not work either.

So where's my error?

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  • 2
    weak battery?.. – Juraj Dec 6 at 13:07
  • What is on an Uno board that can make noise? – JRobert Dec 6 at 14:22
  • Well, I feel stupid now. It was a weak battery. Not an empty battery. I had just used it for something else without problems, so maybe that's why I did not think of this possibility. Well, at least, I know to tell the kids when to change their batteries... @JRobert: I don't know. Sounds like a switch changing between on and off very fast. – bstabens Dec 7 at 21:06

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