External power plug wiring.

[EricJ]

22 minutes ago, carusoam said:

I’m still trying to figure out how the three prong plug checks polarity, before opening the relay though...

That's what the diode does.   The coil in the relay will only energize (and close the relay) when current flows from the external source through the coil.   If the polarity is reversed, the power conductor voltage will be below the ground reference, so the diode will prevent current from flowing backwards through the coil since it will be reverse-biased.

 

Edited December 7, 2020 by EricJ

[carusoam]

+1 for the Yetti drawings...

+1 for having an engineer to explain it... 

Thanks Eric!

Go MS!

Best regards,

-a-

[1001001]

7 hours ago, carusoam said:

-a-

I’m still trying to figure out how the three prong plug checks polarity, before opening the relay though...

It doesn't, except through the pin sizes.  The top pin (as oriented on my 201) is a smaller pin than the other two.  The top two pins are wired together and connected to the positive terminal on the power supply.  The bottom pin is large (same size as the middle pin) and connected to the negative side.  If someone mis-wired the power plug or power supply it could be no fun at all.

[N201MKTurbo]

8 hours ago, carusoam said:

+1 for the Yetti with drawings!

Thank you!

Best regards,

-a-

I’m still trying to figure out how the three prong plug checks polarity, before opening the relay though...

if you hook up the jumper cables backwards, the diode will be reverse biased and no current will flow in the diode. With no current in the diode, the solenoid will not close.

[Blue on Top]

This thread is fascinating to me (I'm not an EE).  Plus, I needed to post something to stay in the loop on this one.  Thanks all y'all