Power for 2 small servos and ardunio

Hello,

I'm planning on building a small robot as a first foray into robotics. I have two SG 90 servo motors which I have modified for continuous rotation, an ardunio Uno and a wifi shield which I will use to send commands to.

My question is how to power this all.

The servos need between 4.8-6v, they work fine individually, when connected to the 5v pin on the Ardunio so I'll aim for about 5v.

The input voltage on the Ardunio is 7-12v.

As i understand it the Ardunio would probably struggle to power this all from the 5v pin. That means the servos would need to be connected directly to a battery.

I think, and would like to use, a Li-poly battery. They seem to come in 3.7 or 7.4. So I would plug the battery into the Ardunio vIn pin.

I'm struggling with getting the best way to reduce the voltage down from 7.4 to 5v for the servos.

Also I've read that the voltage of a battery drops as it discharges, will this be a problem, how would I allow for this?

Any help much appreciated

Ben

Look for "DC-DC converter". Something like this.

If you use a 2S lipo (7.4V) the converter will compensate for the voltage until it gets too low...and you should never let a lipo get below about 3V/cell.

Steve

Another possible power source is a power bank.

slipstick:
Look for "DC-DC converter". Something like this.

If you use a 2S lipo (7.4V) the converter will compensate for the voltage until it gets too low...and you should never let a lipo get below about 3V/cell.

Steve

Thanks Steve, that looks like what I would need. How would I ensure that the voltage doesn't get too low. If it got lower than 3v wouldn't the Ardunio stop working as it needs above 7?

vinceherman:
Another possible power source is a power bank.

Interesting! I think I have a spare one lying around, how would I connect it to the servo? Just hack a usb cable?

That is what I have seen done.

btb331:
Just hack a usb cable?

That is what I have seen done.

Here is an example. I think he powers the arduino with it as well.