Help on Robot Power

Using Arduino Motors, Mechanics, Power and CNC
#1

Hello there,
I know this issue have been posted several times, but after reading the similar topics Im just more confused than ever.

Im a total newbie in this eletronics and Arduino world, but Im willing to learn, I got my Arduino UNO and started to design my project:

a autonomous robot, with the parts:

1 Ultrasonic sensor as eyes,
2 IR sensors as table edge detectors
1 mini breadboard
1 H Bridge (L298N)
2 common DC motors (those yellow plastic with yellow wheels avaliable in many stores)
and my custom power suply, a 7.2V, 1300ma (6pack rechargeble grouped in paralell)

My questions are:

1) Can I use this battery pack as my only power source, for everything? Will I have problems with the sensors if I do it this way? (I really dont want 2 power sources, as for simplicity sake).

**2)**is this the best way to connect it is to plug the battery on the H bridge (V input and ground)?, plug the motors on the H bridge and connect the external 5V output of the H bridge to the Arduino board 5V input. The ground of Arduino goes to the same ground input of the H bridge (same as the battery ground also goes). Is this correct?

3) If im using the 5V pin of the arduino to power it, How do I power my sensors? Using the same output on H bridge to the breadboard and plug them all on it? That way my H bridge would have 2 cables on the 5V output connector (1 to Arduino and 1 to breadboard for sensors) and 2 cables on the ground connectr (1 from the battery pack, 1 from the arduino board)

As far as I undesrstood so far, the above 3) plan will not harm my circuit, but Im willing to learn if there is a better way to do this, it feels somewhat weird to plug 2 cables in one connector of the H bridge. Is this what is known as paralell power suply?

Thanks a lot for take the time to read this, sorry for my poor English. Im having great fun so far and learning tons a day. But Im still too newbie to do it all by myself without the fear of burning things.

Thanks again, Arduino community.

#2

Are you using manufactured ultrasonic board?

Connect the battery into the power socket on the Arduino and use the 5v output to power the sensors.

Please provide a link to the motors so we know what voltage and current they need.

Weedpharma

#3

It is inconvenient to use two battery packs on a robot, but you are guaranteed to have problems using just one. There are thousands of posts on this forum from people learning this lesson.

The motors introduce electrical noise into the power supply that confuses sensors and can cause the Arduino to reset, or in some cases damage it. Avoid this by powering the Arduino and sensors separately, but connect all the grounds together.

With careful design this problem can be greatly reduced or eliminated, but few experimenters have the skills to do so.

#4

Thanks weedpharma, I got the specs of the motors:
Working voltage: 3v to 6V , current: 160mA at 6V each.
weeeeeeeed.

jremington
Thanks for showing me that I am wrong, and specially why. Im changing my design to fit 2 batteries.

So please, now I have more questions than ever.

I found this guide:

There I figured I should use another 7.2v 1300ma battery to power the arduino, plugged in the Japan Jack (Barrel) instead of the VIN pin because of the regulator, right? Then power the sensors from 5V+ out to the breadboard. The motors battery goes directly into the H bridge. Is this safe and OK?

About the grounds, they all should be together, but thats a little tricky to me, where exactly should they "meet"?
Please, give me some light on this:
if I use the Jack for one battery, the ground is already "inside" Arduino, right?

Does the ground out from the H bridge goes into one of the arduino GND pin on arduino, or should I plug the secondary battery ground direclty into the GND pin?

The other GND pin goes to breadboard and grounds all sensors.
Does the Arduino board gets all the ground together "inside"?

Thanks again, sorry for such noob questions, I got the original Arduino board and am very very afraid of burning it.

#5

In general power motors separately, then things tend to work better (ie its a very good idea).

#6

here I figured I should use another 7.2v 1300ma battery to power the arduino, plugged in the Japan Jack (Barrel) instead of the VIN pin because of the regulator, right? Then power the sensors from 5V+ out to the breadboard. The motors battery goes directly into the H bridge. Is this safe and OK?

That is what many people do; should be fine as long as the battery voltage stays above 7 V (the minimum for the Arduino).

Ground pins on any one module are always connected together internally, unless clearly labeled as an exception (sometimes you will see "analog ground"). Connect two modules together using any convenient ground pins. On a motor module, the motor power inputs will be clearly identified; observe proper polarity of course.

#7

Of course in practice the first sign your battery is getting low is the Arduino resets, which can keep cycling
and lose you control. This is less desirable the larger the robot gets.

#8

jremington thank you for the very descriptive answers, this will help me a lot for sure.

hey MarkT , if I get a battery with more voltage, say one more cell goin to 8.4V , same 1300ma, does this make a more stable source when the battery is low, would it last longer or this woudn't matter, ? also, you know if the type of battery avaliable matters (Ni-CD or Ni-MH)?

thanks again

#9