I have one project, where I'm going to use two stepper motors and two EasyDrivers. The power supply to the motors, through the EasyDrivers, will be 24 V. The controlling bord will be an Arduino Uno.
It would be nice if I just could use the 24 V power supply for everything. The EasyDriver has a 5 V output, max 70 mA according to this page. Am I safe if I connect the 24 V to both EasyDriver boards, then I connect both of the 5 V output to my Arduino Uno? The Uno is said to use 50 mA while idling. But the supply would be 140 mA, so it should be enough, right? The Uno will drive the two stepper motors through the two EasyDrivers, probably one solenoid, too, through its own transistor.
What makes me thinking is that the 5 V output of the EasyDriver is said to be for "external circuitry". Since the max output is 70 mA and the Uno runs at around 50 mA when idle, does "external circuitry" only mean like simple sensors and not control boards like Arduino?
The 24 V suppy is from the power unit from an old typewriter (220 V AC -> 24 V DC).
Wouldn't it be a lot simpler just to use a 7805 voltage regulator to drop the 24v to 5v for the Arduino? Then there would be no strain on the Easydrivers.
Probably yes, but at the moment I don't have a 7805. And my question is, is the 5V output meant for this in the first place. And is it possible to just add two outputs, i.e. connect them parallel?
"70mA max is required for Easy Driver functionality"
What does that mean.
That the big chip uses 70mA max, or that you can steal 70mA max.
I have my doubts for both. 24>5volt is a 19volt drop. That will dissipate 1.33watt@70mA.
Enough to eventually melt the tiny SOT-223 regulator off the board.
Leo..
I don't mind disliking answers I get. If I would, I'd hava a hard time figuring out whether I can ask my questions or will they lead to answers I don't like.
Anyway, I got an answer from the Sparkfun tech support:
You should be able to combine the 5 volt out pins on both easydrivers to double your 5 volt output current. The 5 volt line is used to supply power to the logic side of the driver IC and you shouldn’t have any bleedover into the driver side. Since we don’t have a blocking diode on the board, it’s a good idea to hard wire the M+ and GND pins on the power input together on both boards to ensure both come on and shut off at the same time just to be safe.
"to double your 5 volt output current". That sounds good. I'm going to try this. If it gets too hot, I add a heatsink. If it is still too hot, I'll connect another power supply for the Arduino.
Turns out I need a third stepper motor and driver for my project. So I'll be connecting three drivers parallel - well, not the motor outputs of course, but the power inputs and the 5 V outputs. This way each 5 V output only needs to output a third of the total needed current.
You should never connect regulated voltage outputs in parallel.
The individual output voltages are NOT the same and the regulators will "fight" each other, leading to possible oscillations, overheating and other malfunctions.
