jt123
Posts: 31
Joined: Thu Nov 30, 2017 7:55 pm

Easiest way to activate an EVSE using passive components

Mon Jan 29, 2018 9:46 pm

I'm trying to build a device powered by an EVSE's J1772 connector, and would like to know what the easiest way to trigger the activation is.

Based on my understanding, all I really need is an inline diode on the pilot pin, connected to passive resistor from pilot to ground (2.74k), and then a second resistor (1.3k) in parallel which can be activated with a switch. When the first resistor is connected (2.74k) the EVSE should think there's a car connected, and once the 1.3k resistor is placed in series (making a net resistance of about 880ohms), the AC lines will energize.

The proximity side of things is simply for the car's sake of knowing if there's a EVSE present or not - would be nice to use this to detect the button press on the gun to stop drawing power, but in this case I could also just turn things off by disconnecting the 1.3k resistor above.

If I want to find out the amperage of the EVSE I would then have to actually read the duty cycle of the pilot, which I probably won't need for this application.

Is the above interpretation of the signalling protocol correct?

(mods feel free to move to "off-topic" or a more fitting sub-forum if deemed necessary, since this is not a Leaf-specific engineering topic, but I do sometimes see related tech discussions in this section occasionally :) )
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Re: Easiest way to activate an EVSE using passive components

Mon Jan 29, 2018 11:07 pm

I built an adapter box that receives a J1772 plug to power a 6-50 outlet. If memory serves, I just used a diode and a ~880 Ohm resistor.

I’ll check it tomorrow to verify if the more learned on this forum have not responded by then.
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JeremyW
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Re: Easiest way to activate an EVSE using passive components

Mon Jan 29, 2018 11:49 pm

Some recent EVSEs do not like going from state A to state C without first going to state B. I would use the resistors and a switch as described.

This presentation from Chris Howell covers the J1772 spec quite well.
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jt123
Posts: 31
Joined: Thu Nov 30, 2017 7:55 pm

Re: Easiest way to activate an EVSE using passive components

Fri Feb 02, 2018 5:07 pm

great, thanks! i will most likely go with the two-stage route with a switch connected to the second resistor.
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