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I've just received a Keyestudio W5500 Ethernet Development Board, I bought this device because Arduino Ethernet Uno r3 was discontinued, and I don't want loads of shields. So anyway it arrived this morning.

The device needs to be powered by 7 - 12 Volts DC power source via a barrel connector. However, the polarity is unclear.

  1. The power polarity is not indicated on the board anywhere
  2. It isn't indicated on the box that the device came in
  3. It's not indicated on the company webpage for this product here: https://www.keyestudio.com/keyestudio-w5500-ethernet-development-board-for-arduino-diy-project-without-poe-p0368.html
  4. It's not on the wikipedia page either: https://wiki.keyestudio.com/Ks0304_Keyestudio_W5500_ETHERNET_DEVELOPMENT_BOARD_(WITHOUT_POE)
  5. The sales team need to consult with engineers to find out... and that could take a while...

So I'm wondering if there is a way to check what the polarity is using a multimeter?

Now I've checked that the outside of the barrel connector goes through to all the ground pins. But I read somewhere that ground can be negative or positive, so actually, I'm not sure that helps me.

I'm an electronics n00b. Are there standard ways to checking these things?

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    \$\begingroup\$ You should be able to do a simple continuity test with the VIN and/or GND pins on the connector to determine which is which. \$\endgroup\$ – Ron Beyer Jun 18 '20 at 16:03
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    \$\begingroup\$ Check resistance/continuity between the barrel pins and the Ground pins on the board. The one that is shorted is GND. As a sanity check you can check the other pin, follow input diodes and so on. \$\endgroup\$ – Wesley Lee Jun 18 '20 at 16:03
  • \$\begingroup\$ Thank you very much for your answers, so I've determined that the outside of the barrel goes to the ground connections on all of the pins (and the metal ethernet cover and usb shield). I'm sorry if i'm being dense here, but does that mean that the outside of the barrel is negative or positive ? \$\endgroup\$ – Owl Jun 18 '20 at 16:08
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    \$\begingroup\$ There is a cylindrical (electrolytic) capacitor next to the barrel jack. One side is marked with a black strip (that is negative.) If that has continuity to the outside of the barrel jack, then the outside is negative. If the strip side instead has continuity to the center pin, then the outside is positive (unlikely.) \$\endgroup\$ – rdtsc Jun 18 '20 at 16:52
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I just wanted to put an answer here in case anyone else is looking for the power parameters of this device.

So the inside of the barrel connector is positive, and the outside is negative.

Thanks to the helpful comments, I went through with a multimeter, testing the LEDs, but i saw that the tiny amount of current flowing through the diode was enough to illuminate it. Once i worked out which direction the electricity flowed through the diode, i connected one lead of the multimeter to D4, and one to the ground and i saw that the diode illuminated.

This told me that since the black lead was connect to the ground and the red was on the other side of the diode, that the polarity must be (+) in the center and (-) around the outside.

I then cautiously powered up with 3v instead of the usual 7-12v and the diodes illuminated, which is good, i'm guessing they wouldn't otherwise, so then i powered it up with 7.5v and the board seems fine.

If anyone has a better way of doing it than this please leave an answer.

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