I am building a custom solution where 4 servos will be controlled from each SSC-32U. Each servo on each board will only be moving one at a time. Each board / servo will be on a separate slider, otherwise I’d connect all of the servos to a single control board.
My question is this. To simplify wiring, I want to run all three boards off of the same 12V 3A wall power supply, with a cut off switch at the power connection and another at the board. This is only to save on wiring and assembly. I could run three separate power supplies if needed.
Given the board itself is powered from the USB cable, and only three servos could be operated at any given time across the three boards, and the power supply is rated at 3A, do you think it’s safe to use the same power supply?
We assume your system uses motor control interfaces that require 12 V DC? Mentioning this just in case. Sometimes people think the SSC-32U makes the input voltage “RC safe”; it does not. It is passed along to its VCC/GND rails as-is.
Actually, only the USB-UART TTL interface chip is powered by the USB cable. The on-board logic is powered through an on-board voltage regulator connected to VS1.
Well, this really depends on your servos and power supply (minus the negligible losses of your wiring, etc.). What is the peak current required by your motors with their highest load? If all three of them require this current at once, does it exceed the current provided by the power supply?
If so, you may want to get a stronger power supply to provide enough current for such loads. It is worth nothing that the startup current of a DC motor under load is basically very similar to the stall current. Of course, it does not stay there permanently, but a large drain from 3 motors near-simultaneously or in quick succession may cause a brownout situation if your power supply cannot keep up.
If you do need more power, we do have a new power supply that is perfect for most heavy loads. It is the RB-Hap-06. It provides 15 A @ 12 V DC and it has proper protections against short and others.
Yes, that is completely safe. Typically if the motors draw too much current, the voltage will drop. If it is a mild drop, you will get less torque or even no motion at all (if the motors do not get enough power). If the current spike is so high as to drop the voltage significantly, the SSC-32U may enter a brownout state and reset. That being said, it can survive quite large voltage drops with the two massive caps near the screw terminals. If the board does reset on huge power draws (check the blue PWR LED; it should be solid all the time when powered, no flickers) then you need a bigger power supply.
Thanks for the reply. To clarify, I’ll be running three USB cables from a USB hub to each of the three boards. For the power, One central supply with a main toggle switch branched to each board which will have it’s own toggle switch. Each servo is under extremely light load, as in they are just rotating a 3" by 4" piece of sheet aluminum so I expect the loads to be very light. As I said in the original posting if the servos were on the same slider I would use the same board for all 12 servos.
That said, If I do encounter problems with the power supply, I’ll check out your new unit with the higher amperage.
As for your switches, we recommend using double pole switches (to connect/break both VCC & GND), such as a double pole single throw (2P1T). Ex: RB-Sct-1106.
Sincerely,
P.-S.: Feel free to post some pictures and/or descriptions of your project on our project showcase section. We are certain members of the RobotShop community would be curious to see more about it.
This is for a client so I’m not sure if I can post the full solution publicly. That said, I made use of a number of Lynxmotion solutions in a way I’m sure they weren’t intended for and am combining them with MakeBlock components as well (structural pieces, not the electronics).
My solution for power is to use a PC power supply (in this case a Corsair CX-650M), cut the ends of basic connectors (keeping the power supply connectors intact), hook the wires up to the switches, and use the 12V switched lines to feed SSC-32U’s, and Stepper Motor Drivers connected to Arduino Uno boards (the Uno boards draw power from the USB connection). Got a special part to plug into the large power supply connector so it thinks it is plugged into a computer, and have that jumper wire connected to a toggle switch as a master kill to each unit.
A simple solution to save me from well over a dozen AC to DC power bricks.
Sounds intriguing. If you do ever obtain the right to publish this information in the future think of us!
Great idea!
I’ve done the same multiple times, too. I used to work in IT and kept a bunch of various grades of power supplies around for testing stuff. Once I started doing more electronics and robotics, a small 500 W µATX power supply became my new best friend quickly. The main advantage, I figure, is that they are high quality, very stable power supplies with good isolation. And, you know… they are quite easy to find for cheap (or free!).
