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I'm working on a project about a self-stirring robot with sensors to avoid walls.

This project is composed by one Raspberry responsible for all the algorithms, one Arduino to deal with the sensor and the motors, one sensor to measure the distance in front of the car and two motors to make the car walk though the environment.

I need to place everything correctly in such a way that the car moves freely without wires connected to it for not much than 1-2 hours.

What I'm actually doing is powering up the Raspberry with his micro-usb wire then connecting the Arduino to the Raspberry USB port and then connecting the rest to the Arduino power source.

Obviously the Arduino isn't providing the necessary power for the two motors and the sensor although when I was searching I read that the motors need an independent power source because of network distortion they make...

So what kind of battery configuration circuit will I need to keep all this up? Maybe a 12V lithium battery?

Information I've collected about the power needed in:

  • 1 Raspberry (3): Works with 5V/2A
  • 1 Arduino (Uno): Works with 7-12V
  • 1 Sensor (HC-SR04): Works with 5V (normally from Arduino)
  • 2 motors (28BYJ-48 with driver ULN2003): Works with 5-12V
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    \$\begingroup\$ Generally speaking both stepper motors and raspberry pi's are ill-suited to battery power. It's also better not to mess with lithium batteries in learning projects where many mistakes are likely to be made. Your Arduino can be powered with 5v via the USB (including by plugging it into the pi). So one idea would be some large number of AA cells for the motors and a USB power brick for the electronics, another would be a switching buck regulator from the motor supply to the electronics which if done right will overcome come sharing issues. You will probably get at best a few hours runtime. \$\endgroup\$ Dec 10, 2019 at 19:27
  • \$\begingroup\$ You have provided insufficient information for anyone to provide a specific answer. If you want to know if the motors need a separate supply then yes they do. \$\endgroup\$
    – scorpdaddy
    Dec 10, 2019 at 19:29
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    \$\begingroup\$ You had better read through the help section at electronics.stackexchange.com/help/asking It will explain how to ask an acceptable question. \$\endgroup\$
    – scorpdaddy
    Dec 10, 2019 at 19:38

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We did something similar back in college for the IEEE micro-mouse competition. Chris Stratton is correct in that I wouldn't mess with Lithium batteries just yet. Use a bunch of NiMH batteries, as they are robust against shorting (though the wires may not be!) and easy to charge.

I think for my project I used about 8 AA batteries in series with a buck regulator to step it down for the CPU. We used a micro-controller to drive stepper motors drivers which drove the steppers directly from the battery. We would get about 30 minutes of dev time per charge with this configuration.

Now in your case you have some power hungry computing specified, so you may need to do a little math: Estimate your instantaneous power draw. \$5v*2A + 3.3V*0.1A + etc... = ?W\$.

Most NiMH are around 2000mAh. So 8 in series gives you \$1.2V*8*2Ah=19.2Wh\$

Finally divide your estimate by your battery pack to get a time estimate: \$\frac{?W}{19.2Wh}=?h\$

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  • \$\begingroup\$ 8 NiMh cells in series is 9.6 volts. At 2Ah, that's 19.2Wh. \$\endgroup\$
    – JRE
    Dec 10, 2019 at 22:26
  • \$\begingroup\$ That's what I get for doing math in my head...doh! \$\endgroup\$
    – Aaron
    Dec 10, 2019 at 23:26
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You should choose a minimum battery voltage that can supply 5V-10% or so plus LDO dropout for a FET type LDO. e.g. 6V min to ? max

The 28BYJ-48–5V Motor resistance is 50 Ohms and rated for 5V so the current 5V/50ohm= 100 mAmp. 12V supply voltage is less efficient with PWM but can be used to control heat,torque. Otherwise the tiny motor may overheat if drawing 0.2*5V=1W.

So 3x NiMH sounds ok then 2x Li Ion's if low duty.

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