I am working on a Project with:
Can I power my Arduino UNO with a common 9v Battery?
I also have in mind to use an external power supply for servos... but what to use?
Please suggest me a perfect power supply system
Unfortunately, the perfect power supply system doesn't exist yet. However, powering an Arduino is simple. You have to main options 9V for standard "full size" Arduinos (such as the UNO that you mention), although you could go for the low voltage 3.3V options.
Covering just the 9V option, from the Power section of Arduino Uno:
Power
The Arduino Uno can be powered via the USB connection or with an external power supply. The power source is selected automatically.
External (non-USB) power can come either from an AC-to-DC adapter (wall-wart) or battery. The adapter can be connected by plugging a 2.1mm center-positive plug into the board's power jack. Leads from a battery can be inserted in the Gnd and Vin pin headers of the POWER connector.
The board can operate on an external supply of 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may be unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts.
You should probably also take a look at Power Supplies, in particular the section on Batteries and cells, also from the following section Voltage conversion and regulation, it states:
In a very simple scenario, you connect a disposable 9v battery (probably one of the (approx) 4cm x 2.5cm x 1.5cm units with two snap connectors on one end) to your Arduino, and the Arduino's built in voltage regulator takes care of reducing the voltage to a consistent 5v or 3.3v, depending on the sort of Arduino you have.
So you have a couple of choices regarding 9V, either the P9 cell
or a pack that holds six 1.5V AA or AAA batteries.
You may find this link, How to run an Arduino (clone) on (AA) batteries for over a year – part 2, an interesting read. Here the chap uses four AA batteries, which only gives 6V, to power an UNO:
I have just highlighted some information, you should take the time to read the links fully, and google for more information.
Regarding the servo motors, more current may be required. You can use the same four AA battery pack, thusly:
but the capacity of the batteries may leave something to be desired, especially if you use rechargeable batteries (which in today's eco-concious world, you should), so you may require something more hefty. A quick google will show you the options available.
The video Flite Test : RC Planes for Beginners: Batteries and Safety - Beginner Series - Ep. 7 is an extremely useful video tutorial about LiPO batteries for RC projects.
Everything @Greenonline said plus...
A 2 Cell Lipo battery is 7.4 V. A modest 500 mAH battery would run your project for several hours, perhaps days. If you're not satisfied with the run time, buy a battery with more mAH, they go well past 5000 mAH! After all, these are the same types of batteries used in all forms of Radio Control Aeromodeling (lots of servos and brushless DC motors).
The Uno can regulate the 7.4 V although you'll need to buy/build a cable to connect the battery to the Uno. I'm not sure how much current the Uno regulator can provide but I've driven two micro servos with mine.
If the servos chatter, hum, are otherwise not working right or if there is smoke coming out of the regulator, you probably need a separate power source for the servos. A BEC like this https://en.wikipedia.org/wiki/Battery_eliminator_circuit is an inexpensive alternate and also a common RC part. :)
Selecting a power supply involves considering the following:
1. Voltage Requirement
2. Current Required
3. Running duration
4. Cost
Voltage Requirement:
From the list of items specified all of your items except the microSD card (which works at 3.3V) works at 5V.
Current Requirement:
Arduino UNO: about 50mA
9G servo motor: 730mA peak
LED 5mm: 20mA*2 = 40mA
microSD Card Reader: 200mA peak
Speaker: 350mA
Total Current: 1.370 Amps
Running Duration:
Say I want this device to run for 1 hour straight, in order to this I will need a battery supplying 5V 1370mAh and a 1C rating. So if you want your device to run longer you will need to get a battery with a higher capacity (for 2 hours 2740 mAh and so on)
Cost
I dont think i need to mention much in this criteria
Solution 1:
For these requirements your easiest solution is to use a USB power bank with 2000mAh or more.
On a protoboard solder 1x USB male, 1x USB female, 2x header pins. Solder All the positives together and all the negative together. And now you have a breakout for the power rails from the USB as well.
Power the Arduino via usb, microsd card via the 3.3V on the arduino and the rest via the breakout pins.
Solution 2:
Using lipo batteries. Lipo batteries have the advantage of having a large capacity in a small package (or a high power to weight ratio). In order to use this you will need a voltage regulator to get 5V. Please note that as per the calculation you will need a total of 1.37A to power your device at peak, this cannot be done via the on board regulator of the Arduino.
In total you will the following components to get this to work:
LiPo battery
Voltage regulator
LiPo Charger
Solution 3:
Using Alkaline battery. You can refer to the Minty Boost tutorial over at Adafruit to learn about this.
Conclusion:
If you want a headache free solution to your problem, buy a USB power bank , but if you want a more customizable and low cost solution go for the LiPo battery
And if you dont need a portable solution. Go for a wall adapter 5V/2A, thats pretty much every high end mobile phone charger
I have had a lot of success using an off-the-shelf power bank - they're easy to get, already have charging circuits (from USB), and are at the right voltage (+5V). You can plug the power bank directly into the USB port of the Arduino.
The only problem I've had is that some power banks shut down if there is not enough current being drawn - a resistor from +5V to GND solves that problem (make sure you work out how many watts your resistor is letting through, to make sure it can dissipate the heat - I used a 100Ohm resistor, at 5v; I put "Ohms Law calculator" into google, filled in 5V & 100 Ohm, and found that it needed to be a 1/4 watt resistor - perfect! I also noted that it drew 50 milli amps AKA 0.05 amps. I tried resistors with a higher resistance e.g. 200 Ohm, and the power bank powered down. If your project is drawing more power (continuously!) then you might get away with a higher resistance).
My power bank can supply 1.5 Amps, which should be plenty for your project.
You can use 9v battery and use separate one for servos. Due to voltage being "relative," you still need to connect the grounds.
You can connect the + of the battery to the VIN of the Arduino.
