I'm quite new to the Arduino world and I would love some recommandations about the right way to do something.
I'm planning to use step motor 28BYJ + the driver named ULN2003.
The technical sheet says that it's working on 5V but I sometimes saw that this is not a good thing to plug it to the 5V of the Arduino board but more to an external power supply.
Do you have any recommandations on that ? (or link to where I can buy such external power supply ?)
Second question, I'm planning to use a lot of these motors. I saw that I can extends the digital pin (using 74HC595 for instance) but does it mean that each motor will need its external supply ? How can I compute how many of these motors I can bind to a single Arduino Uno board ?
The power supply will need to be shared across the motors and a common ground back to the Arduino too.
How many motors will dictate most the the current that you need for the power supply.
IIRC they draw about 150mA per motor so two motors would need 300 mA and so on.
Some of that will also depend on the load / torque applied to the motor shaft.
A single UNO can be used up to a max of around 400mA but experience shows that motors are ALWAYS better off with a seperate PSU and each item be it a simple sensor or other component will use part of that 400 mA.
A "lot of these motors" doesnt really help out anyone wanting to guide you more on your power needs as it is not specific enough and may also depend on what else you also may want to connect.
One power shift register, like the TPIC6B595, can replace one 74HC595 and two ULN2003 chips.
They, like the 74HC595, can be daisy-chained.
So 'many' of them can be controlled with only three Arduino pins.
Several projects with "many steppers" on this site.
Use the search field on top of this page.
Leo..