what do you mean "This will give me a total of 18 Volts (The components should only need 17)."?
how did you get that number and why would you need that many volts?
you can actually run the Arduino straight from certain AA's. 4 normal non rechargeable AA will give out around 5.7-6 volts which will hurt your arduino
if you use 4 of these AA Robot or human? you will get 5.3 max on full charge and 4.9 volts when your batteries are dead (and you can recharge them) these types of AA can also last longer on a charge then regular AA (they are 2300 mAh).
By using this setup you can completely get rid of the 9 volt battery (which die fairly fast)
for your case the AA could work for everything the Arduino,sensors,servos and motor driver.
just so you know, you would not plug the AA to the barrel jack or the Vin pin on the Arduino because the regulator would drop the 5.2 volts down to 3-4 volts
you would need to plug the AA into the 5 volt pin and ground directly
the 5 volt would be the voltage out as well as where you plug in your batteries.
you should never use the 3.3 volt pin unless a device is suppose to use it as you can damage it.
I think I know the Tamiya gearbox and motors that you are using. Very common. I have the same. But I just ordered these:
They are Tamiya motors also, and fit in the gearbox. Advantageously they use twice the voltage (6v) at half the current. They are also very cheap at $1.79 us each. 70mA free running and 800mA stall
If I were you I would use a 9v with the barrel plug for the arduino and the ultrasonic sensor (which uses a tiny amount of current) and 4 or 6 aa rechargeable batteries for the motors and servos (common ground with arduino). That would reduce the electrical noise on your circuit and increase overall efficiency. I can't think of a reason you would ever use the same power for the arduino and inductive loads like the servos and dc brushed motors.
If the maximum voltage for your servos is 6v then you might want to think of using 6aa batteries ~9v (if they are alkaline) with a 7805 5v voltage regulator. 5v should be just fine for the servos and motors but you need at least 7v for the 5v regulator to work properly.
I hope this makes sense. I have a project that I am working on that has components very similar to yours so please feel free to ask if you need clarification or guidance.
I forgot to mention that for my motors I use TIP 120 transistors (with flyback diodes) for electrical isolation from the arduino. You'll need something like this for your motors. There are many options depending on your intended use. h-bridge etc....Let us know what you are doing exactly and we can be more help. You may need an h bridge.
He said he was using "Arduino Motorshield R3 " I'm guessing that has a H-bridge and and isolation circuits.
I would not use the 9 volt battery.
I have been using the rechargeable AA in just about every one of my robots with no problems what so ever.
if you can get away with out using voltage regulators you should. voltage regulators can't give a lot of current without heating up.
To figure out how much heat a voltage regulator will give out take the input voltage (9) minus the output voltage (5) and multiply it by the current use in amps so say you are using 200 miliamps (.2 amps), thats .8 watts of heat which will heat up your Arduino
I use to use 9 volt batteries a long time ago, they are expensive and don't last long.
here is a example image of how you would hook up the AA battery pack (It has to be the rechargeable AA )
You are right! He did say he was using a motor shield. I was thinking of how I would do it with what I have instead of how he would do it. Without the shield, I stand by my comments though. A 9v alkaline powering the arduino with average input is fine. Definitely not for inductive loads though.
After reading about the motor shield, doesn't it only support 2 motors and ONE servo though? He has two servos.
I currently have a RC truck made into a robot. It has a ping))) ultrasonic distance sensor, two motors the specs of which are unknown, a piezo speaker, 4 rechargable AAs connected via barrel plug, and a 6v 600mAH rechargable battery that came with the truck. The 6v battery is soldered to the ground and vin connectors on the motor shield so most of that power goes directly to the motors but the whole thing can run at about 3/4 full speed with the AAs unplugged.
you should not plug in the AA's in the barrel jack it wont work since the barrel jack is regulated the 5.2 volts will go down to 3-4, you need to plug the AA in directly to the 5 volt line and ground
9v batteries are terrible for arduino projects, I used two on my truck at first and my sensor was acting as if it wasn't getting enough power, now I have even less voltage and it works great. The mAH on 9v PP3 batteries must be terrible compared to AAs.
arduinopi,
just to clarify...
nominal voltage of aa Ni-MH batteries is 1.2 v. Total of 4.8v.... 4.9 v when batteries are dead? Is this from experience? I'm not doubting you. I'll go to wall mart tomorrow.
In any case I would still go with at least 7v with the 7805 voltage regulator (with smoothing capacitors). Extra energy can be dissipated with a simple nut and bolt as a heat sink through the TO-220 hole but probably not needed. There may be some wasted energy but is your robot going into outer space? It'll be best in the long run.
cherryguy:
9v batteries are terrible for arduino projects, I used two on my truck at first and my sensor was acting as if it wasn't getting enough power, now I have even less voltage and it works great. The mAH on 9v PP3 batteries must be terrible compared to AAs.
Agreed, six Alkaline AAs in series will have a nominal voltage of 9 VDC just like one 9V battery, but the total charge capacity will be a few times higher than the 9V battery. There are battery holders for six AAs are readily available online, usually carried in electronics stores, and sometimes can be found at hardware stores.
If more charge capacity is necessary or desired C and D sized batteries have the same nominal voltages as AAs and AAAs, but significantly more capacity. One useful thing I've found when using D sized batteries are these holders that are modular and can be setup in series, parallel, or a combination of the two based on how you snap them together.
