Max Current on Pmod CON3

[Asher Webb]

Hello! I am interested in using the Pmod CON3 servo driver for a robotics project. I was curious is anybody knows what the output current limit is on it. I plan to use 4 MG996R servos per board, which would draw a peak current of 10A.

Thanks!

[JColvin]

Hi @Asher Webb,

I don't have exact component details to provide (when I'm trying to look up the specific parts, I'm just seeing "connector header, 1x3, male, straight" or "terminal block, 1x2 position, screw terminal") which doesn't help for looking up datasheets.

However, if we use this datasheet as a general representation of the 1x3 100 mil spaced header, https://mm.digikey.com/Volume0/opasdata/d220001/medias/docus/937/Female_Headers.100_DS.pdf, it states a maximum current of 3 Amps. Screw terminals of course tend to have higher current ratings due to their increased size.

I don't know what kind of cable you'll be using to connect from the 1x3 100 mil header, but I would anticipate that if you're using a wire style similar to UL1015 that you aren't going to have a drastically better current or wattage rating (this detail isn't readily specified from what I can see, https://iq.ul.com/awm/stylepage.aspx?style=1015).

Regardless, the question is if when the 4 servo motors are drawing their start/stall current of 2.5 A for a brief period of time, will the 'weak point' of the system (i.e. the jumper block that selects whether you are using external power or host board power for powering the servo motors) be able to handle up to 10 A for some small amount of time?

I don't have a definitive answer for this, but my gut says that as long as you aren't deliberately stalling them (thus giving any materials time to dissipate any accumulated thermal energy), I think you could be okay. To be clear, I'm presuming this based on the fact that the Pmod CON3 has four different outlets and that Digilent would have tested running four different motors simultaneously when this module was designed way back in 2005, though the specifics on that have been lost to time and I don't have 4 servo motors nor a 10 A supply to try this out myself.

Anecdotally, you can find a number of tutorials showing people attaching their external power supply to solderless breadboard rails which aren't rated for high current or wattage, so pragmatically speaking you should be okay (again making sure you aren't stalling the motors).

Let me know if you have any questions.

Thanks,
JColvin