Hello, I have a school project and I have to power an Arduino UNO, 2-3 servos (not at the same time) and a toy DC motor. Is it possible to power the whole setup with 4 AA batteries?
I personally tried to power my Arduino with a 4 AA batteries (alkaline) with a servo connected and it didn’t power on, so I’m kind of worried, perhaps I didn’t do something right? But is there a way to make it work? Or I am at a dead end here?
Thanks for your help
4AA batteries is 4*1.5 or 6Volts at full strength for standard alkali. That is too much to feed in as the regulated 5V and too little for the raw power input. So you are in a bit of a bind.
No the servos should be ok to run direct from the battery pack. Have no clue about your motor, but if it is a 6V hobby motor than it should work as well. The problem is your Arduino. What you need is a regulator to get you regulated 5V from the 6V supply. Most linear regulators need “headroom” or an extra 2+ volts above their regulated voltage to work. If you want 5V, you have to supply 7 volts or more in. The rest gets burned up as heat.
But you do not have the headroom for a linear regulator. So what you need is a switching buck regulator to get the 5V. They do exist and for not that much money. But this is not the end of your problems! As your AA batteries die, at some point they will go bellow the 5V and now you will need to boost the batteries to 5V. So you should be looking for a buck-boost regulator that will output 5V. Something like this might work:
or a linear LDO (low drop out) regulator. These can take a little experimentation to make them stable in some circumstances, but I could still recommend it-- Except! as fil-freak pointed out, if you stop at 5V, there's a lot of battery life left. Fortunately, your microcontroller, although made for 5V, can probably run considerably lower, and may have an absolute max of 7V, so you should be able to make it work.But you do not have the headroom for a linear regulator. So what you need is a switching buck regulator to get the 5V
Thank you for your replies. I tried powering the Arduino with 4 AA Duracell batteries and plugged only one servo in with the power connector connected to the 5V pin of the Arduino and it worked! I don’t mind battery life because it only needs to work for 2 mins. I haven’t tried with more servos (still in shipping), but when I get my other ones, I will try it and keep you updated.
One more question:
I’ve done some research and I find that most small projects, people have two separate power supplies, one for the Arduino and the other one for the motors. The common one seems to be the 9V for Arduino and 4 AAs for the motors. Why is that so popular? Isn’t there a way to have only one power supply for everything? Like a motor shield, would this work?
Thanks for your time!
Two power rails are popular to keep the noise from the electric motors out of the electronics. It is also nice to have the separation so when the motor batteries die, the brains can still shut things down. I used to have an RC car where as the single battery would die, the receiver would stop functioning properly. It always seemed to fail with the throttle wide open leading to much damage.
I have done some reseach and found those Pololu Adjustable Boost Regulator 2.5-9.5V:
http://www.pololu.com/catalog/product/791
Could I plug my battery pack to the GND and Vin of this regulator and then plug the Vout of the regulator to the Vin of my Arduino UNO and without forgetting to have my GNDs all linked together? Like that I could boost my voltage to a 9.5V instead of a unstable 6V. Would that work?
That’s a very nice product. For lower battery drain, set the Pololu regulator’s output voltage to 7 or 7.5V, just high enough that the UNO’s regulator gives a reliable 5V.
Thank you again for your quick input. I will buy it and give this voltage regulator a try. Just to make sure I don’t short circuit anything, I connect the Vout of the regulator to the Vin of the UNO and have everything’s GND connected together (regulator, battery pack, UNO)?