pgrovetom
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Proximity Detection - Having trouble finding an explanation

Thu Nov 03, 2011 2:10 pm

I have designed my own EVSE but am having trouble finding a precise description of how the EV proximity detection actually works. Does anyone know what the J1772 spec or specifically the Nissan Leaf is looking for on the "proximity" pin to decide the connector is engaged. I've looked around and all the descriptions are vague and don't provide a description, block diagram or schematic as with the pilot signal. The pilot signal is well described but most sources simply state the proximity pin is used by the EV to know the connector is engaged but without details.

My J1772 cable/connector provides a wire for the proximity pin but I've been unable to find anything that explains what the EVSE provides on this signal pin. Can anyone provide me with either an explanation of what the EVSE must provide on the proximity pin?

Is it grounded?
Does it have a specific resistance to ground?
Is it related to the EVSE/EV states/pilot sequence?
Is it connected in any way to the connector engagement button?
My cable/connector has a direct connect from the proximity pin to the wire and the button has no effect on it.
thanks
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Re: Proximity Detection - Having trouble finding an explanat

Thu Nov 03, 2011 2:33 pm

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pgrovetom
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Re: Proximity Detection - Having trouble finding an explanat

Thu Nov 03, 2011 3:13 pm

Sorry, I should be more specific with my question. The J1772 spec shows a partial schematic but doesn't discuss how the the switch inside the J1772 connector and 330/150 ohm resistors and actual detection circuit uses them.

Its the purpose both functionally and for safety or reliability of the engage lock button and the disconnected, being engaged but S3 open and fully engaged with S3 open - 3 states are actually used by EV that I'm wondering about. Since its vague, I can't help but wonder if the Leaf, Volt and other EVs behave differently as the not inserted to being inserted lock button pushed to fully inserted plus if the human doing it starts, stops, pushes button, changes mind and or is erratic... etc.. what happens? Does it matter?

The J1772 spec shows a diagram with a switch, 150 ohm and 330ohm resistor that appears to be integrated into the J1772 connector. I says that when the connector engagement lock is pushed, the 330ohm resistor is shunted such that the 150 ohm resistor appears from ground to the proximity pin. Once engaged and the lock released, the 150 + 330 ohm resistors or 480 ohms appears to ground. The EV provides a 330 ohm pullup and a 2.7K pulldown to ground. When the connector is disconnected, the 330 ohm pullup dominates and the EV proximity detection circuitry sees 90% of the +5V which tells the EV, the connector is not inserted. When the connector is inserted with the lock pushed shunting the 330 ohm, 150 ohms appears to ground and the EV proximity circuitry sees about 1/3 of the +5v due to the series 330 ohm to +5v and 150 ohm to ground. Then when the lock is released and the connector fully engaged, the 480 ohm ( 330 + 150) results in 480/(480+330) * 5V to the proximity detector.

So it looks like they want to discriminate between connector not engaged, connector being engaged with lock pushed and fully engaged and lock released. My real question is does the Leaf actually look for the full transition and how it reacts.

Resistance across proximity pin to ground equal to:

open = not engaged
480 ohms = being engaged with lock being pushed by installer
150 ohms = fully engaged = ready and safe to connect power and charge

The J1772 connector and cable I have appears to have no integrated resistors or electrical switch S3 tied to the lock button.

Is it really necessary to provide the lock button interlock?

If the EVSE simply had the 150 ohms to ground without the additional delay due to the lock button interlock state (480 ohms), will it result in any functional issues. It seems one purpose of this scheme is to possibly assist in prevented arching of the AC pins.

On initial insertion, the AC is disconnected due to the pilot/state sequence. But on removal, the charging could be underway and arching could occur if the connector is pulled out. If the EV detects the lock button being pressed and shuts off its current draw, then this scheme could help prevent any removal bounce arching.

Does anyone know specifically how this scheme is used on the Leaf and what would be the downside to not providing the button pushed 480 ohm removal condition? Is the risk functional or arching protection or both?

Since my connector does not implement the scheme, I could have a switch on the EVSE to simulate the lock button switch. Its not as good because one needs to remember to use it but my only other option is getting a new connector/cable.

Does anyone have any additional thoughts on the implications of the scheme and how the Leaf uses it?

thanks
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davewill
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Re: Proximity Detection - Having trouble finding an explanat

Thu Nov 03, 2011 3:38 pm

pgrovetom wrote:Is it really necessary to provide the lock button interlock?...
Yes, otherwise when unplugging, the AC contacts could be powered and drawing current. The interlock's main function is to prevent that. The car has to cut the current draw very quickly whenever the latch button is pressed.

Someone here measured the current during charging, and found that pressing the button did indeed kill the current draw, and releasing the button (without unplugging) restored it.
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Re: Proximity Detection - Having trouble finding an explanat

Thu Nov 03, 2011 4:26 pm

davewill wrote:
pgrovetom wrote:Is it really necessary to provide the lock button interlock?...
Yes, otherwise when unplugging, the AC contacts could be powered and drawing current. The interlock's main function is to prevent that. The car has to cut the current draw very quickly whenever the latch button is pressed.

Someone here measured the current during charging, and found that pressing the button did indeed kill the current draw, and releasing the button (without unplugging) restored it.

Correct, when the latch is depressed by a user to remove the nozzle from the car, the car will immediate stop drawing current in order to prevent arching while removing the plug.
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Thinwing
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Re: Proximity Detection - Having trouble finding an explanat

Thu Feb 16, 2012 3:23 pm

On the av equipment plug with cable ,there are two wires in addition to lg guage power cables...a orange one that carries the square wave pilot signal..the blue ,one the proximity detector connects to where??kpc

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garygid
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Re: Proximity Detection - Having trouble finding an explanat

Fri Feb 17, 2012 12:21 am

In many/most cables, since the Proximity interlock is properly handled in the J1772 nozzle (plug) with a switch and 2 resistors, there is no "proximity" wire in the cable.

In these cables, there are two large "Hot" wires, a healthy Ground wire, and only one other wire, the small Control Pilot wire.

If a the cable has a 5th wire, to the Proximity switch, the EVSE usually ignores it.

FYI: Check your description:
You describe the switch as shorting the 330 ohm resistor when the nozzle's "Release" button is pressed, but then say that the 480 (330+150) ohm condition is with the button pressed. These contradict each other.

The Release-detection is an important function, to stop potential arcing when unplugging an on-going charge session.

Some of the (especially arlier) made-in-China nozzles do/did not have a switch in the nozzle.

Can you modify yours to add a micro-switch, perhaps epoxy it in?

Possibly, open up your J1772 plug, take (and post) some good pictures around the Release Button (pressed and released), and we might be able to help.

Putting a "proximity" switch on the EVSE is not a good idea, for safety. However, having a "Stop" button your EVSE is a good idea.

If you MUST use that J1772 plug (with no switch), and CANNOT add a proper Release-Button switch to it, I might have other suggestions, but they are less safe.
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