Arduino + 9g servo from 2 AA battery

Hi everybody!

First sorry my bad english and you know I haven't too big electrical knowlege...

I make a project with Arduino Pro Mini, 9g servo and some small parts (LED and receiver).

It Works fine from wired power (eg. USB).

I have a small project box space for two pcs AA battery and a 0.5A 5V boost step-up converter like this:

http://www.ebay.com/itm/5PCS-PFM-Control-DC-DC-USB-0-9V-5V-to-5V-dc-Boost-Step-up-Power-Supply-M213-/401277024478

I experience 'reset effect', when start up the arduino and get the first position the servo the whole system restart - I think there is no enought power. I tried to separate feeding the servo - it looks like there is enought the two AA battery power for just the servo power.

Have you some experience how to power up this project from 2 AA battery - eg. use capacitor or bigger step-up converter or other good idea?

Important aspect the energy efficiency - use step-up converter to bypass the board regulator and there is sleep event too for the longer battery life.

You are experiencing a "reset" because that regulator and battery combination can't supply enough current for the servo.

Yes this is my opinion too.

But have you got some idea how to resolve it?

Use a power supply for the servo that's capable of 1A without dropping out? 0.5A is pushing it for most miniature servos, and certainly not sufficient for standard servos. Servos need decent power.

They normal scenario for servos is using a NiMH pack designed for the purpose, ie high current rechargables.

If you can use 3 x AA cells everything should work without needing any voltage converter.

...R

So do you think it will work with a 2A 5V booster?

What do you think about something capacitor with this 0.5A power supply?

Robin2 It's a 5V system

3xAA NiMH 3x1.2 = 3.6V its not enought 3xAA alkaline 3 x 1.5 = 4.5V not enought too

Otherwise I tried 3 AA with the booster but not OK.

How do you think without voltage converter?

dolcevita: 3xAA alkaline 3 x 1.5 = 4.5V not enought too

I built a little demo with a Mega, a Leonardo two servos and some LEDs all working directly from 3 x alkaline cells.

If you use an Atmega 328 chip on a breadboard it will happily run from 2xAA cells. I have never tried a servo with 3v but I think you can get some low-voltage devices.

...R

How do you power in?

To VCC - bypass the onboar regulator?

Or to RAW?

I know VCC must be exactly 3.3 / 5V

RAW (168 chip) ideally voltage form 6 V to 12 V

dolcevita: How do you power in?

I just connected the battery to the 5v pin. Obviously it is ESSENTIAL not to exceed 5v - but a bit lower does not cause a problem.

...R

Thank you for your answers - good to know.

But I think this is not my solution now because I want to leave possibility to use 1.2V rechargeable and 1.5V alkaline cells too.

Maybe a capacitor can help.

dolcevita: But I think this is not my solution now because I want to leave possibility to use 1.2V rechargeable and 1.5V alkaline cells too.

Have you tried the rechargeable cells - maybe they will work?

...R

Try 4 AAA cells. AAAs are smaller than AAs. Also try 2 li-ion batteries from old Nokia phones. They are small too

DanielFernandes: Try 4 AAA cells. AAAs are smaller than AAs. Also try 2 li-ion batteries from old Nokia phones. They are small too

CAUTION. 4 x AAA cells or 2 x Li-ion cells exceed the 5v limit for an Arduino.

...R

Oh, yeah your right. I thought about adding a voltage regulator then.

DanielFernandes: Oh, yeah your right. I thought about adding a voltage regulator then.

I was deliberately trying to avoid the need for a voltage regulator.

...R

So here is my conclusion

With 470 capacitor no change but with 1000 μF capacitor is a half solution:

Works the servo but it's a little slight - with some load sometimes reset the arduino... But overall not bad.

Then I tried with two step-up converter. One for the arduino (and peripherials eg LED and receiver) and the other just for the servo.

This solution totally stabilize the arduino run but servo is not too powerfull too. At this time capacitor not cause any change...

So this is my experience.

I not need too much power from the servo so I think I will use one but I don't know what is the better solution (professionally and safer). What do you think?

And what do you think about the capacitor for the 2nd solution? Is this needed and what circuit arduino or servo?

Of course if somebody have a better idea please share

Thank you