I'm hoping for some guidance. I am working on a project with an Arduino Mega running 46 SG90 Micro Servo's. I have done projects before with a couple servo motors but never this many, and am hoping for some guidance on powering and connecting this many motors.
I have a DC variable power supply that can go up to 30V and 10A that I was initially planning to use to power the servo motors (arduino will be connected to and powered from computer usb). However, with 46 servo motors I'm calculating that the total current required would be closer to 30A (servo draw up to 600mA (0.6A) x 46 = 27.6A). With the voltage set at 6V.
For those more experienced, does this look right? And if so, would running with this current level require the use of higher gauge wires, or other considerations? In any case would it be a smarter move to split the system into to two or three servo groups, with multiple power supples at 15A or 10A powering separate groups of servo's instead of one for everything? (They would still all need to connect to a common ground on the arduino and the arduino pins, would there be any issues here?)
Any help or advice would be greatly appreciated.
Thank you so much!
split up, yes. One supply or many, but FUSE the wiring appropriately either way.
How many will function simultaneously, though? Do they all need active drive signals all the time? Explore the concept of shutting down some, to conserve power.
Much more detail is needed about your application before we can help guide you further.
Wire size is determined by mechanical requirements or current, the one that requires the larger gauge is the one you should use. Remember this motor is starting from zero and will draw stall (inrush) current until it spins up. Your power supply and wireing needs to accommodate this current. This is important and should be calculated before doing any system power design.
Thank you so much, this is already really helpful. I have not worked with fuses before so had not even considered that. I have looked into it and will be adding these to the system.
Some more project detail: essentially this is multi/tandem robot arm system. Although it would be great if all 46 of the motors moved simultaneously, this is not strictly necessary. They can be split into groups (ex: first quarter of motors rotate to set position, then next group does the same and so forth). I understand that the holding servos would have a lower current draw (0.1A-0.2A). Functionally the servos would all rotate to a position, hold for a little bit, then rotate to a second position, hold, repeat until full sequence has been moved through (hundreds of rotations).
I am currently considering a set up with a secondary DC power supply at 10A, splitting the servos into two separate systems (so 23 servos per power supply), and only moving ~12 servos at a time per system. So holding servos would be at 110.2A = 2.2A and moving servos 120.6A = 7.2A for a total current draw of ~9.4A.
I would also include a 10A slow-blow fuse for for each power supply (and a capacitor as well). I believe I would also need to make sure that the servos are initialized in stages to avoid inrush currents from overloading the system. Does this seem right?
Thank you for your advice. Looking at the potential inrush current for this many motors it appears it could max out any system I have (approximately 70A total for 46 servos with a peak current around 1.5A). To work around this I am thinking to power up/connect servos sequentially in groups of 6 at the initialization stage. This should, I hope, take care of the inrush current?
Depending on your design you may not need fuses. Many power supplies have built in current limiting, if you wire can handle that much current A fuse may not be needed. The primary function of fuses is to protect the wiring (circuit protection), not the load.
They are also used to isolate faults. Many times fuses are sized to protect a specific unit and are generally contained therein. When you have a bunch of loads, the wire gets smaller and then fuse(s) or poly fuse(s) (an automatic resetting thermal fuse) can be used.
In your home you have breakers, sized for the wiring, not the lamp you plug in, the same in your car, note the wire gauge changes.
Fuses serve as a protect/isolation service, and sized to the application and the designers requirements.