Go Down

Topic: Power advice with only AA batteries (Read 974 times) previous topic - next topic

ler1m

Hi,

I got a project to do for school and we are restrain to use only  4 AA batteries. We're gonna have to power a couple of accessories, probably 2 DC motors, 1 servo and maybe a distance sensor.

I already have an arduino uno and a motor shield (DRrobot 2A motor shield http://www.dfrobot.com/index.php?route=product/product&filter_name=motor%20shield&product_id=69 )

So my question is, since I only have 4 AA batterie (4x1.5V)s, what is the best solution to power all my accessories ?

I saw that polulu have a voltage booster that boost from 3V in to 25V out. Is it a good solution ? Or I'd have enough juice with 4 AA batteries  ?

Thank you,

JimboZA

How do you define "juice"?- Volts? Amps? Amp-hours?

For a start, you Uno needs either 5V at the USB input, or 7+ at the barrel or Vin, so you're already going to have to regulate your 6V down to 5 or up to 7.... Although I'm assuming the Uno needs to be powered from those batteries?, or will it remain hooked up to the PC on the USB?

Then that motor shield uses a 298, which eats volts.... from memory, and you will need to check the data sheet, it drops a minimum of 2V up to 3 or so depending on current, so you need to put at least 2 more volts in than your motors need... you didn't say what they are: if they're toy types at say 3V then you could be ok.

And the servo will need 6V.

You'll need to do some sums as to what current you need for all of these things.....
Roy from ITCrowd: Have you tried turning it off an on again?
I'm on LinkedIn: http://www.linkedin.com/in/jimbrownza

retrolefty


How do you define "juice"?- Volts? Amps? Amp-hours?

For a start, you Uno needs either 5V at the USB input, or 7+ at the barrel or Vin, so you're already going to have to regulate your 6V down to 5 or up to 7.... Although I'm assuming the Uno needs to be powered from those batteries?, or will it remain hooked up to the PC on the USB?

Then that motor shield uses a 298, which eats volts.... from memory, and you will need to check the data sheet, it drops a minimum of 2V up to 3 or so depending on current, so you need to put at least 2 more volts in than your motors need... you didn't say what they are: if they're toy types at say 3V then you could be ok.

And the servo will need 6V.

You'll need to do some sums as to what current you need for all of these things.....


Hobby type R/C servos don't NEED 6V, their typical operating voltage range is 4.8 to 6vdc. They were very much designed to operate from 4 series wired AA cells as that was a very common R/C airborne fight battery before the advent of nicad/nimh/li-po choices that one now has.

Lefty

JimboZA

Roy from ITCrowd: Have you tried turning it off an on again?
I'm on LinkedIn: http://www.linkedin.com/in/jimbrownza

zoomkat

Quote
Hobby type R/C servos don't NEED 6V, their typical operating voltage range is 4.8 to 6vdc.


Well, the lower voltages are ok when only a rudder and other light loads are being moved. If the servo is expected to hold/move any real load, 6v will be much better. Check the torque specs for servos operated at 4.8v and 6v.
Consider the daffodil. And while you're doing that, I'll be over here, looking through your stuff.   8)

retrolefty


Quote
Hobby type R/C servos don't NEED 6V, their typical operating voltage range is 4.8 to 6vdc.


Well, the lower voltages are ok when only a rudder and other light loads are being moved. If the servo is expected to hold/move any real load, 6v will be much better. Check the torque specs for servos operated at 4.8v and 6v.


Just means one just needs to pick out their servos while keeping in mind the operating voltage they will be using.

Lefty

zoomkat

Quote
Just means one just needs to pick out their servos while keeping in mind the operating voltage they will be using.


It also means that when somebody is requesting suggestions, the suggestion should be for a chiose that has the best chance for success instead of what might be barely acceptable.
Consider the daffodil. And while you're doing that, I'll be over here, looking through your stuff.   8)

retrolefty


Quote
Just means one just needs to pick out their servos while keeping in mind the operating voltage they will be using.


It also means that when somebody is requesting suggestions, the suggestion should be for a chiose that has the best chance for success instead of what might be barely acceptable.


That's a "have you stopped beating your wife" type of statement. Hard to refute. My point is that their are a zillion servos available out their and if one starts out a project stating they will be using 4 AA cells for power and they know the torque and speed requirements (or if that is important to their application or not) they might need then there shouldn't be difficulty finding a match. Or are you saying servos should always be powered by 6vdc because that way they deliver their highest speed and torque?

Lefty

ler1m

thank for the reply guy.
First of all, @jimboZA, when I say "juice" I mean all kind of power. Is it possible? or 4 AA batteries is simply not enough... ? Then, 4 A batteries is the ONLY thing I can use to power everything, from servos to dc motor. Also, the DC motor are toy types @3V.

And with the sum of all current, why that matter  ? is it because the batteries can't provide enough ?

Then, about the servos, it wiould probably be use onlyy for direction so the speed isn't a big concern. It's the required torque that I'm mostly concerned.

This is my first project with arduino and all type of micro controller so every obvious information would be usefull ! :)

zoomkat

Quote
Or are you saying servos should always be powered by 6vdc because that way they deliver their highest speed and torque?


I said "If the servo is expected to hold/move any real load, 6v will be much better. Check the torque specs for servos operated at 4.8v and 6v".  If a person has a choise of voltages to drive a servo, I'd suggest selecting the voltage near the high end of the voltage range. The below servo has the specs for operation at 4.8v and 6v. I see a noticable difference in performance with my servos just between 5v and 5.7v.

http://www.hobbyking.com/hobbyking/store/__23487__HK15328A_Analog_BB_MG_Servo_58g_12_8kg_0_20s.html
Consider the daffodil. And while you're doing that, I'll be over here, looking through your stuff.   8)

ler1m


Quote
Or are you saying servos should always be powered by 6vdc because that way they deliver their highest speed and torque?


I said "If the servo is expected to hold/move any real load, 6v will be much better.(...)



What about the way to plug it? Directly into the motor shield (or via a breadboard...)

And same question for the power to my Arduino... Do I plug directly the 6 volt into the shield and let the shield power everything so far ? Or there's a circuit that would optimized my ernegical demand?
Thaanx again guys

zoomkat

Quote

What about the way to plug it? Directly into the motor shield (or via a breadboard...)

And same question for the power to my Arduino... Do I plug directly the 6 volt into the shield and let the shield power everything so far ? Or there's a circuit that would optimized my ernegical demand?
Thaanx again guys


Good homework assignment. Same basic questions asked/answered daily.
Consider the daffodil. And while you're doing that, I'll be over here, looking through your stuff.   8)

ler1m


Quote

What about the way to plug it? Directly into the motor shield (or via a breadboard...)

And same question for the power to my Arduino... Do I plug directly the 6 volt into the shield and let the shield power everything so far ? Or there's a circuit that would optimized my ernegical demand?
Thaanx again guys


Good homework assignment. Same basic questions asked/answered daily.


I've been searching a lot and the most frequent answer is to power both of em. Although, I can't find any on with the same power restriction as I have.

Go Up