Hi!
I'm currently building the inmoov hand i2 and facing issues with adequate power supply.
I haven't found a solution yet, which is why I decided to write my first forum post.
The project:
6 servos (JX PDI 6225MG 300) are connected to the fingers and wrist to move the prosthetic arm.
The problem:
If I connect only 1 servo it moves to 0 position as I coded it to do and therefore the finger flexes completely.
The more servos I connect, the more the voltage drops and the less the servos move, thus the fingers aren't flexing completely.
With a multimeter I measured the following:
Stall current of each servo: 1.3 A. Therefore 1.3A x 6servos = 7.8A, meaning a 10A power supply should be good!?
Voltages (under load): 6V for 0 servos -> 4.1V for 1 servo -> 3.8V for 2 servos -> 3.6V for 3 servos -> ...
Is one of the following things maybe going in the right direction for a solution?
use thicker cables (I'm using regular jumper wires to connect the servos)
a friend suggested that a motor driver might help but I found many posts that also had voltage drops despite using them
capacitors could be a solution? If so, how many do I need, and at what capacitance [µF]?
This is my first project with Arduino and electronics and I am unsure about what I should do right now and hoped to find some helpful advice here.
What's the make of the power supply? Chinese supplies sometimes deliver either 6 volt or 10 amps, but not at the same time.
Is there a current limit adjust on the power supply? It might be set rather low.
Is there an operators manual of the supply available?
If those voltages were measured at the supply, you have a bad supply. If measured at the servos, you've identified the problem. Replace with good 18ga wires for + and - to each servo, and provide a reference gnd connection between Arduino ground and Servo power gnd. That should solve it.
at your Servo power supply, both wires should be heavier gauge(16 or 14) until the point where you fan out to the individual servos, which can be 18 ga.
Model: SHNITPWR SNT-0312-120
I can only adjust the voltage, not the current.
A german operators manual came with the package but there's no helpful information in there.
I can't find (an english) one online.
A reference GND is already connecting the Arduino and servos.
And I honestly don't know the gauge of the cables I'm currently using. They seem to match the servo's cables...
I measured the voltage at the soldering at the bottom of the perfboard where all the servos are connected to the power supply.
Should I measure somewhere else to know whether they are to thin or...?
If you could replace them with a pair of wires soldered to the perfboard you'll be a lot better off. Still not perfect, but you should see a much higher voltage there if you do that.
I've had problems with almost that exact same kind of power supply. Might of been the same one. Take the green terminal adapter out and splice some other kind of connector on.
Motors have inrush current at startup and your calculation for the maximum current demand and therefore your power supply demand could be way off.
This would quickly become more a problem as you add more servo loads.
My approach to improving this is first, as suggested by @camsysca in post#11, to use 14ga cables, that I will screw into the screw terminal (connection 1) at one end, and solder along the pins on the bottom of the perfboard (connection 2) at their other end.
