18v and 12v from same source?

Hi,

This may be a very stupid question, but here goes.

Is it possible to get two different voltages from one battery pack?

My thinking is if I use 6 x 3v cells to make an 18v battery pack, would I be able to connect the arduino to just 4 of those cells to run it off of 12v.

I have attached a rudimentary schematic of what I had in mind.

Thank you.

Yes, but why 12V? Why not 9V? Make life easier for the 5V regulator.

That is fine, although the lower 4 cells will discharge faster than the top two.

One solution would be to power the Arduino through a 9V regulator or even a 5V one from the full 18V output of the batteries. If you use a switching "buck" regulator then this would be even more efficient than a linear regulator.

Thank you for both your replies. I am looking into using a 5v regulator rather than the switching regulator mainly because of simplicity. Would anyone be able to explain the purpose of the capaqcitors in most voltage regulator circuits?

Once again thank you.

The capacitors stop the regulator from oscillating, they are not optional. See the data sheet from the manufacturer of the device you are going to use for the minimum values to use. More will do no harm.

Awesome thanks.

Galiphat_1G:
I am looking into using a 5v regulator rather than the switching regulator mainly because of simplicity.

A switching regulator is very simple. You just buy one.
The small ones are very efficient, and can run from a 18volt source.

A lineair regulator can be problematic. Current = heat = shorter battery life.

Tell us what you are planning to do.
It might be better to use a 2C battery (7.2volt) and a boost converter for the 18volt device.
Leo..

Galiphat_1G:
Hi,

This may be a very stupid question, but here goes.

Is it possible to get two different voltages from one battery pack?

My thinking is if I use 6 x 3v cells to make an 18v battery pack, would I be able to connect the arduino to just 4 of those cells to run it off of 12v.

I have attached a rudimentary schematic of what I had in mind.

Thank you.

That's still two battery packs in disguise - you still have the situation where one pack
will discharge at a different rate to the other, which is usually undesirable.

Wawa:
A switching regulator is very simple. You just buy one.
The small ones are very efficient, and can run from a 18volt source.
Pololu 5V, 500mA Step-Down Voltage Regulator D24V5F5
A lineair regulator can be problematic. Current = heat = shorter battery life.

Tell us what you are planning to do.
It might be better to use a 2C battery (7.2volt) and a boost converter for the 18volt device.
Leo..

I'm planing on running the arduino uno off of the 5V(or 9V) power supply. Then using a motor shield to run an 18v drill motor that draws between 5A and 15A.

I will start looking into the switching regulator as well.

Thank you all for your help.

Then using a motor shield to run an 18v drill motor that draws between 5A and 15A.

Can you get motor shields with that current capacity?

Grumpy_Mike:
Can you get motor shields with that current capacity?

Yes, this one from Cytron is good for 13A continuous with 30A peaks. It runs off of between 5V and 25V