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Topic: my Uno won't start up! (Read 181 times) previous topic - next topic


Hi all,I am using a Duinotech(?)Uno, with a motor shield to control my radio controlled rowing boat.

It used to work well!

The Uno is powered by a 9v battery pack, via the barrel jack, the brushed DC motor is powered by a separate 14v battery pack, via the motor shield, and everything was working properly.

Last time I put the model away, 2 weeks ago, I left the switch on, so, naturally the 9v battery went flat.

No problem, new battery!

Now, the Uno won't start up when I connect the 9v battery.

There are no lights, nothing!

 I am getting 9.6v at the plug, normal for a new 9v battery. I even replaced the plug, but it made no difference.

It works perfectly if I power the UNO with the USB cable from the laptop, I can up load the sketch, I can run the whole boat on the bench when connected to the lap top,

My question is,

Would leaving the 9v power on for a long time, (2 weeks) damage the UNO ? Either mechanically or electronically?

It is always put away dry after a sailing session, on a shelf in a well ventilated dry environment.

I have pulled it all apart, shield off, shield on,  the UNO works on USB power, but not on battery power.

I worked in the engineering trade for a few years, and so I have logically gone through it all ,step by step.

This problem is bugging me! And I really hope that some-one can help me.

Thanks in advance,




My guess would be a broken connection in the jack itself, or just after.

Try putting that 9V into Vin with wires as mentioned here:

Leads from a battery can be inserted in the GND and Vin pin headers of the POWER connector.


Thank you, meltDown,

The lights come on when I connect 9v to VIN and Ground.

It is a workaround, but unfortunately I am using the 2 Grounds for the IR sensor and the radio Rx.

Is there a fuse in the circuit for the barrel jack, and is it re-settable or replaceable?

And would leaving the power switched on for an extended time blow the fuse?




I am using the 2 Grounds
I am using a Duinotech(?)Uno
I've never seen one of those, but on a real Uno, there are 3 grounds... there's one next to pin 13.

(And you could always solder up a "Y"connector.)


Thank you, meltDown,

Today I found something that I've never seen before in my history of playing with batteries!

I use a 6 pack of 1.5v AA batteries to power things. (9V) (There is a reason!)

When I took out all the old, flat batteries, 6 of them, from the packs, they got mixed up with the brand new ones in the box.

No problem, a multi-meter does wonders!

The first battery I tested showed -0.21v!

OK, check the leads into the multi-meter, all OK, red to pos, all OK.

Next battery showed -0.19v

Next battery showed 1.61v, (a bran new battery) so the meter is working!

I found that 5 of the 6 batteries all showed a negative voltage!!

As the switch had been left on for two weeks, the UNO had slowly drained the batteries to a point that the polarity of them had changed!

I've never heard, nor seen of that.

I don't think that there are many PCB's around that will tolerate reversed polarity, and so my UNO has slowly fried itself.

So just a message to all inventors out there,  TURN OFF THE BATTERIES!!!!!

Now I just have to buy another UNO, they aren't all that expensive!

Thank you.


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