Look again...the rails are supplied from the Arduino 3v3 terminal.
More importantly, @CD_
look at Figure 7, Typical Application Schematic, on page 10 of the datasheet for suggested wiring information. There are NO connections visible in your pictures shown in post #1 for pins 9 through 16 on the quad half-bridge h-driver chip, SN754410. Pin 16 is supposed to be connected to the positive logic supply, not left "floating" in space. As @danadak
mentioned, it is wise to use both moderate-valued (100 µF or so) electrolytic capacitors in parallel with medium valued (0.1 µF or so) plastic- or dipped mica-dielectric capacitors to "noise bypass and filter" the power supply rails. Also, until you know wtf you are doing, try to avoid using solderless breadboards except to "try out" new or novel circuits, after which time you should transfer those circuits to soldered components on either perforated board or a printed circuit board (PCB). The Chinese can make PCBs very inexpensively, but there is a steep learning curve concerning what documentation is required and how to prepare and send it to the PCB manufacturer.
has already mentioned, there should be a separate power supply, completely independent of the Arduino power supply, for the PMDC (Permanent Magnet Direct Current) motor. This is COMMON PRACTICE when driving high-current, reactive loads such as motors or solenoid coils, where the switching current controlled from the Arduino PWM outputs can cause a ground-loop that injects switching transients into the logic circuits. The PWM current pulses have fast rise and fall times that can play havoc with supporting logic-level circuits if the currents produced have a common path back to digital common. ALWAYS keep power, analog, and logic commons separate until the commons are joined at ONE location.
Hi, I'm a beginner to electronics and have an Arduino.
Well, good for you. And welcome to the Maker Pro (formerly ElectronicsPoint) forums. As a beginner, you should be aware of some things about this community. Many who post here have many years of experience and training in the ART as well as the SCIENCE of electronics. If someone like @Bluejets
offers advice, it behooves you to accept it at face value without delving into long-winded arguments or asking uninformed questions.
We understand that you want to learn, but everyone here offers their assistance in the forums free of charge. Our time is valuable to us. We don't want to waste it on argumentative trolls, or lecturing newbies who haven't a clue. So, first of all, READ and UNDERSTAND the damned datasheet: ALL of it! If there is something that you don't understand, you may ask questions here.
Second, if you are new to Arduino and are programming this open-source marvel for the first time with a new, un-debugged, application program, please visit the Arduino forum
and lurk there for awhile before posting. The world-wide Arduino community is HUGE, and most of us are willing to help beginners who demonstrate a willingness to learn.
Third, we were all beginners once upon a time. I started down this path in 1953 at age nine, but you have to run like hell just to keep up in electronics. I have been running for a very long time. With electronics, it helps to expand your horizons to include physics, chemistry, optics and electro-optics, and the principles of mechanics. Never stop learning! Do some research using library books, a somewhat heavy and cumbersome collection of printed paper pages held together with string, glue, and stiff covers, conveniently arranged on shelves and sorted by subject matter... usually available for borrowing without a lending fee. Get to know your local librarians. They can help point you in the right direction for learning. Beware of ANYTHING you "discover" on the Internet. Always fact-check your sources of information.
Fourth, start a laboratory journal where you record with writing and photographs what you are doing, what you have learned, and what mistakes you have made in your journey of learning about electronics. If insanity is defined as doing the same thing over and over and expecting different results each time, then a good journal will help preserve your sanity. Journal keeping will also allow you to easily and quickly incorporate your new-found knowledge into your latest projects.