I have a little experience with Arduino, and this is my first post.
After doing a few projects on the breadboard, it's time to start the soldering work, and I was wondering:
what exactly is the necessity of a power supply module, and whether there is a way to deliver the required voltage and current without them.
Thing is, some of the projects I'm working on are best physically as small as possible, and I would do well to drop this bulky piece.
Could I just power Arduino Nano and a single servo motor (say SG90) with a USB cable that is torn open and delivers the 5V to the circuit, which then feeds it to the servo and to the Nano?
I'm under the impression that a USB cable caps to 5V, so why would I need to use the power supply module, e.g. MB102?
I would like to power everything from one port, and I have gathered that one should not power the servo from the Nano 5V port
Generally, why do people use these power supply modules, and not just cables that deliver the wanted voltage?
Eventually, I would like to have this project using one servo and one Nano working from a single battery that I could charge with a USB port.
So if anyone has suggestions of a decent battery, I would also be grateful. It's difficult to find a battery, and everyone seem to point to having 4 AA batteries for a servo and a 9V for the nano. This won't do. For the finish product, I don't want to be changing and undocking batteries all the time, when I could just plug in one single cord.
If you really need battery, consider a 5V power bank. Lots of current, lots of capacity, portability.
The issues are, the Nano regulator is not designed for anything beyond it's own needs. Using USB to power your Servo will give you grief, as most USB computer connections are limited to 500 mA(there are other options, like a USB charger, which will give you more). Your servo may draw well in excess of 500 mA if stalled, check the spec for the particular servo you have.
Batteries? Batteries just allow a project mobility. Considerations when choosing a battery are battery voltage and current. A twelve volt 5 AH battery can in theory supply 12 volts @ 1.0 amp load for 5.0 hours. A 12 volt 100 AH battery can support a 12 volt 1.0 amp load for 100 hours. You choose a battery on the intended application including how long you expect a battery to support a load.
When using mains power, eliminating need for a battery you choose a power supply with the correct voltage and current rating for the anticipated load. That plus about a 20% overhead since you don't really want to run a power supply at its rated maximum current out. USB is 5.0 volts. However the 5.0 volt USB ports on a PC are not an infinite power supply. The maximum allowed output current from a USB rail is limited in a USB-powered system. A unit load is defined as 100 mA in USB 2.0. A device may draw a maximum of five unit loads (500 mA) from a port in USB 2.0. Note, reference is USB 2.0.
When we start adding peripheral hardware to for example an Arduino board we need to consider the current draw. 5.0 volts is just that 5.0 volts. There is no issue with the voltage, the issue is with load current verse supply maximum current.
To choose a battery you need to know the max load current for a given voltage and how long you want a battery to last before either disposal or recharge. What is your maximum load current?
The main necessity of a power supply module is to simply supply power to everything in your system. As camsysca said, powering everything from a usb cable will only work if it can supply enough current to power everything in the system.
Another reason to use a power supply module such as the MB102 is to convert the supply voltage into the specified voltage for your devices.
There are all kinds of power supply units out there for projects like these that are in a smaller form factor that the MB102.
