Hi. I am building an obstacle avoidance robot with an arduino and motorshield, and I am having trouble choosing batteries mainly because I can't figure out how the motorshield an arduino work together. I just need some advice before I purchase batteries that won't work.
I am using two of these motors: http://www.pololu.com/product/2212, an arduino uno, an arduino motorshield, a few optical sensors and IR/phototransistors, and encdoders. I have a very compact design, so the smaller the batteries the better.
So, when I have the arduino connected via USB the robot drives fine without any issues and all the sensors work. I planned to use a 9V battery for the arduino and several NiMH batteries for the motorshield, but I don't want to burn up the board or not have enough power.
If I connect 6 AAA NiMH (7.2V total 850mAh/per battery) batteries to the motor shield and a standard alkaline 9V battery to the Vin pin in the arduino, will the motors have enough power? The stall current is 1.6A, so do I need better batteries than that? Will 7.2V be enough for two 6V motors?
I have read many similar situation in the forums, but I am still having trouble answering these questions. I don't understand how the USB can provide enough power to run the entire board and the motors without an additional power source for the motor shield. Would it be possible to power the entire system with one power source?
What ever you do ,make certain that both boards share a common (-) negative on the power…
Your not going to be stalling the motor,the last thing you want to do is throw more voltage and/or current to a motor that has stopped moving.
I use a 9.6 pack for the motor driver and a 6volt pack for the UNO… aslong as they share a common negative its fine.
An yes you can use one power source you could just use your 7.2volt pack… on your motor shield there(maybe) is a 5volt output that you can run to the arduino…
need a little more info on your actual motor driver.Pic?
How do I decide if I can use a AAA 7.2V pack or do I need a AA 7.2V pack. The AAA packs usually have a 850 mAh capacity while the AA packs can have up to 2200 mAh capacity? Space is pretty limited, so I would prefer to use AAA if I can.
850mah refers to a batteries capacity…I look at it as the battery can sustain a 850ma load for one hour…Its alot more involved than that…but the jest is …the higher the MaH of a battery the more capacity …the longer it will last…
Nimh batteries by design and chemistry will only produce and withstand a certain amount of load…
A higher capacity battery can supply more current…but we are talking milliamp …I doubt if your L298P bridge driver would even get warm after a full battery cycle of nonstop use…
I would go as far as to say the amount of load(discharge of your batteries) would even get them warm.
nothing you have is current hungry…unless your going off road or through shag carpet with your bot.
Okay. Thanks. That helps a lot. I think I will probably go with 850 mAh batteries since the robot will driving on tile or hardwood mainly, and I need the smallest batteries possible for space.
Any advice on finding cheap batteries and a charger? Is it necessary to get something like an iMAX balance charger? I know better chargers charge faster, but it seems like it may be a worthy investment.
However I have the IMAX B6AC, I love it …it will charge just about any type of rechargeable battery ,
not money wasted…a guy really never knows where the next project will lead…you could go smaller with the batteries using 7.4v lipo …The iIMAX charger will be there if you need it.
I just use E-bay to buy my batteries and battery holder’s…
