My tracking box is nearing completion. I plan to power it using some lead acid batteries at first, but I’m wondering if it would be possible to use Power Over Ethernet. I’m not sure if it would be able to provide enough current. My box is almost to the point that I can measure the current, but was wondering what I should expect.
I think the motors alone draw 2-3A 12-24V
Is that compatible with PoE?
Hello! We have the same idea about POE. We will do some tests maybe in two days. There is the option to use 30V or even 40V and then use 2 regulators (one for 5V and one for 12V)
@DL2ZZ I think that the last time I measured the current consumption of the motor (between the motor and the driver) was about 1A
Hmm ok. does this mean you set the current on the driver to 1A? I think the datasheet of your motors say something like 2A max. Just wondering as you went from nema14 to nema17 motor to get more torque.
The ultimaker 2 uses nema 17 motors. I believe we set them to 1.6A. you can use them at lower amperages, but that will ‘cost’ you a lot of power. Also note; the standard poolu stepper drivers can overheat, which leads to missing steps. This is problematic for a 3D printer, but killing for a satalite tracker.
Electronics is not my field, but you are free to check out the (electronics)schematics of the UM2, they are open sourced. I’m actively considering just using ultimaker 2 electronics to make the box work. Saves me a lot of effort.
The vRef setting depends on the value of the current sensing resistor on the driver. Some Pololus use a 0.05 ohm resistor, and others (Stepstick) have a 0.2 ohm resistor. This means you cannot always go by the vRef setting someone else is using.
My Kossel Mini uses a Printrboard with A4988 Pololu Stepstick drivers.
I have my vRef set to 1.65v. This comes out to just under 1A of current per stepper.
Explanation and formula here:
Pololu drivers current limit configuration
I have experimented with this setting, and found that heat quickly becomes an issue for both the motor and the driver with settings much higher than 1A. The steppers were actually hot enough to warp the PLA motor mounts on my printer.
Ok, so If we assume a current of about 1A per stepper. The highest power PoE injector/tap I’ve seen are about 30w or (2.5a @ 12v) This isn’t leaving us much room to run the other electronics.
I’m thinking about the possibility of running the tracker from battery power, but using PoE to keep the battery charged.
The UM2 does not overheat. The UMO steppers overheat (and need active cooling). The motors will get quite hot (definately hot enough to deform PLA!)
The other posibility is to ensure that the system mechanicaly stays in place, so you won’t need to use the steppers to ‘hold’ everything in place.
@manthos and I measured the current of the tracking box with two different PSUs: 12V / 15A and 19.5V / 4.62A. The configuration of the tracking box is: arduino pro micro shield and PSU board GitHub, a TP-Link WR703N with openWRT that runs rotctr and rigctr and rtl-sdr doggle for antennas. The measurements can be found here.