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Topic: Motors stop when I switch to battery power (Read 187 times) previous topic - next topic

rhj4

My robot works just fine when tethered by its USB to my PC. I can issue commands from my cell phone (terminal mode) to the robot and they are transmitted and received via HC-05 bluetooth. The robot has two 9V batteries wired in parallel that currently have 7.65 volts (in line voltmeter) and power the L298N H-Bridge. The VCC output from the H-Bridge provides power to the Nano. 

When connected VIA USB, diagnostic output is transmitted over the Serial port back to the PC which displays this information. When I disconnect the USB, the robot, LED 13 on the Nano and the power LED on the H-Bridge are still lit; however, the Bluetooth connection is lost and the HC-05 starts its rapid blink. 

My goal is to be able to run the robot autonomously, but I am a bit stuck here. I have two questions:
1) How do I diagnose what is happening here? 
2) As a general rule, when running the Nano off battery power, what might be causing it to fail?

MarkT

9V batteries aren't able to provide large currents (as needed by motors).  They are at least an order of magnitude too feeble.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

TomGeorge

Hi,
What does the 5V pin on the Arduino measure, with the USB plugged in and with it unplugged?

What model Arduino are you using?

Thanks.. Tom.. :)
Everything runs on smoke, let the smoke out, it stops running....

rhj4

What if I have 2-4 9V batteries wired in series? Will that be strong enough?

zeus2kx

What if I have 2-4 9V batteries wired in series? Will that be strong enough?
You need them in parallel.

slipstick

And if you mean those weedy little rectangular 9V batteries they STILL won't work. Maybe a dozen of them in parallel might.

But rechargeable AA batteries are best for high power requirements like motors and servos.

Steve

MarkT

What if I have 2-4 9V batteries wired in series? Will that be strong enough?
I gave my advice, you can ignore it if you want.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

TomGeorge

Hi,
Do you have a DMM to measure some circuit parameter?

Tom... :)
Everything runs on smoke, let the smoke out, it stops running....

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