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Topic: Need more power. (Read 1 time) previous topic - next topic

deadbird

Hi everyone.
I have a little problem. I have an Arduino Mega, a 128*64 GLCD, a 9V futaba servo (soon there will be another) and a 9V geared motor. The whole is supplied with a regular 9V battery.
When I reset the arduino, my program draws things on the LCD and then operates (at this time) the servo only. And here's the problem: when the servo works, the LCD dims. I think I need a bigger power source? Or something else? What would you recommend? Knowing that I really would like to have only one 9V power supply that my model can carry away.
For more details about the project itself, check my blog out: http://hexecute.blogspot.com

Thanks ;)

deSilva

You are joking about that 9 volts block battery, aren't you?

deadbird

Unfortunately no. I knew that these batteries are less powerful than multiple AA batterie...but the problem is that 9V battery is small enough to fit my project in terms of size. 4 AA would fit too, but deliver only 6V where I need 9/10 V.

RuggedCircuits

A typical 9V battery will drop its voltage by a lot when called upon to supply this much current (servo+motor). You need a bigger power source, or more accurately, a type of battery whose voltage won't drop so much when called upon to supply a lot of current.

NiCd, NiMH, and lead-acid batteries might work better. Still, in a 9V form factor that power won't last long and you will need to replace/recharge batteries frequently.

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Check out our new shield: http://www.ruggedcircuits.com/html/gadget_shield.html

deSilva

#4
Aug 30, 2010, 01:21 am Last Edit: Aug 30, 2010, 01:23 am by mpeuser Reason: 1
The only alternative I know is using very small LiPoly cells from the RC scene. You will need something called "3s" giving you nominally 11.1 volts (more common "2s" will give you 7.4 volts only) You will also need a special charger and all that is not really cheap....

Mind the 9V rechargeables! They might provide the correct current, but they generally come as 6 internal cells = 7.2 volts!! Manufacturers are not ashamed of printing a 9V label on it...

deadbird

What about 8 AA? I could get 9.6V and up to 8*2700=2.16Ah !

RuggedCircuits

That would definitely be better than a single lowly 9V battery.

--
Check out our new shield: http://www.ruggedcircuits.com/html/gadget_shield.html

deadbird

Indeed! Do you think this would be enough?

RuggedCircuits

It would probably be enough to keep the voltage above 7V as input to your board, but it really depends upon the actual current draw of your servo and your motor. Do you have any estimates or measurements on those?

If together they draw <1A I'm guessing you'll be fine.

--
Check out our new shield: http://www.ruggedcircuits.com/html/gadget_shield.html

AWOL

@deadbird:
Quote
I could get 9.6V and up to 8*2700=2.16Ah

Want to do the sums again?
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

deSilva

Hint: The solution is not 2a.b but c.7 Ah

deadbird


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