Hi(sorry for my bad english),
I’m currently use the SSC-32 to move 32 servo HS-645MG.
I am powering VL with 1 generator set on 6V (because LM2937 will product 5V) and
I am powering VS1+VS2(use jumper) with another generator set on 6V.
When I lift up my robot (0 servo touch the ground), I measure 6V on connector VS1 and ~6V for alim. on left and right side.(current total is ~5A)
The problem is here:
If robot stand by itself I measure 10A and i lose 1V if i check directly the alim of servo.
I still measure 6V on connector, but not directly on the servo.
My theory is the Ohm’s law (V=R*I), because my current augment I lose more power between the connector and all servo.
Can you help me to solve this problem because I can’t just raise my tension because my servo can support 6V max?
Thanks for the pictures; that’s a nice robot! We wanted to see where specifically you making your test points, but you have four pairs of probes connected, so it’s a bit hard to tell…
Are you noticing a difference between the voltages at the servos for servos 0-15 and for the servos 16-31? If so, the VS1=VS2 jumpers are limiting too much the current. Can you try connecting your power supply to both the VS1 and VS2 screw terminals?
If it’s not (just) that, can you try using your multimeter to follow the traces to see where there’s a lot of current? For example, between the negative (-) screw of VS1, and 1) the GND pin of servo 0, 2) the GND pin of servo 15, 3) the GND pin of servo 16, and 4) the GND pin of servo 31. And can you do the same between the positive (+) screw of VS1, and the middle pins of servos 0, 15, 16, and 31?
Note that the SSC-32 board isn’t necessarily made to work with currents this high. An option would be to bypass the problem entirely and connect your power supply to the servos separate from the SSC-32 board.
yes but negligible, only 10-20 mV difference.
If I force left side the right side will lose 10-20mV more, and
If I force right side the left side will lose 10-20mV more.
I measure with 2 multimeter for now only use the probe on Red cable on connector for entrance and for servo it’s the down left probe.
I think it’s an option to bypass but the datasheet say support 15A each side for a total of 30 A
ps: I can measure all current but it’s will take a bit of time.
It’s the result of all measure
VS1gnd-servoGnd
[table][tr][td][size=1]servo 0[/size][/td][td][size=1]90mA[/size][/td][/tr][tr][td][size=1]servo 15[/size][/td][td][size=1]390mA[/size][/td][/tr][tr][td][size=1]servo 16[/size][/td][td][size=1]60mA[/size][/td][/tr][tr][td][size=1]servo 31[/size][/td][td][size=1]260mA[/size][/td][/tr][/table]
VS1vcc-servoVcc
[table][tr][td][size=1]servo 0[/size][/td][td][size=1]30mA[/size][/td][/tr][tr][td][size=1]servo 15[/size][/td][td][size=1]290mA[/size][/td][/tr][tr][td][size=1]servo 16[/size][/td][td][size=1]10mA[/size][/td][/tr][tr][td][size=1]servo 31[/size][/td][td][size=1]260mA[/size][/td][/tr][/table]
Problem solved,
I will use the NSR020A0X43Z, a DC-DC module.
I will use a Lipo 7.4V to power this module and output 6V out, and I will use the sense pin to adjust directly on servo.
Thanks for the info. For your measurements above, are they the current consumption of each servo (in mA), or the voltage drop between the pins of the servos and in the power terminal (then should be in mV)? It would be better for us if we can get the voltages…
It’s unusual that the 0 & 15 servos are experiencing more voltage drop than the 16 & 31 servos: the 0 & 15 are much closer to the VS1 terminal so should have less resistance…
The datasheet for the SSC-32 does say that it can work with 15A per side, but that’s peak (inrush) current, not necessarily for constant current. We’ve updated the specifications to make this clearer.
The NSR020A0X43Z supply is an interesting idea, but the 1V drop is still unusual…
