DIY Home EVSE

[Fuzzylogic]

The LM358 is used for GFCI not the pilot, it is far too slow for the 1khz square wave. The pilot uses the LF353 which is a much faster opamp, it is not a rail to rail device so it does have a small voltage offset (spec sheet says 10mv). I only have access to a LEAF, so far the pilot with the LF353 works perfectly. If other vehicles have an issue with the slight voltage drop, an LT1498 would be simple to drop in...


I am not sure why it will not solve GFCI (typo maybe). GFCI is performing quite well with the EVSEs I built so far.

Oh i'm sure your GFCI design works, looks very good actually... I just meant that changing the Opamp to a rail-to-rail device might prevent connection problems on other cars.

I just double checked your schematic, but IC2 is labelled as a LM358 (typo) ?

 

[hcsharp]

Oh i'm sure your GFCI design works, looks very good actually... I just meant that changing the Opamp to a rail-to-rail device might prevent connection problems on other cars.

I just double checked your schematic, but IC2 is labelled as a LM358 (typo) ?

Fuzzy, he said the LM358 is used for the GFCI, not the pilot. Only the pilot signal needs a r-to-r opamp because it has to go to +-12v from a +-12v power supply. The GFCI signal is coming from the current sensor and requires a much smaller range to drive the AD pin on the microcontroller.

While we're on the subject of opamps, I used a cheap one that was temperature rated down to 0C in my UMC. We had a cold snap to about -8C the other night and the device was unable to compensate well enough to work properly until it was plugged in for about 5 minutes to warm up! The pinout is fairly standard so I'll swap it for a better one.

 

[W.Petefish]

Not at all, I will be happy to add any contributers to site, send me an e-mail with your google username to chris1howell83 at gmail dotcom. I welcome anyone to post schematics, code and wiki pages...

PM sent.

 

[Chris1howell]

Good catch Fuzzy. The schematic with gfci has the wrong label for the pilot opamp. The basic schematic is correct. I will correct the label.

 

[PV-EV]

What are you using for the power supply (+/- 12V)?

 

[Chris1howell]

I am using a dual output (+12V -12V) switchmode power supply from Micropower Direct. I am working on a lower cost solution with a single output (+12V) switchmode supply plus a 1W DC\DC converter for the pilot.

 

[W.Petefish]

Create a virtual ground using one Opamp and a few passives.

 

[Chris1howell]

I am not sure a virtual ground would work in this case. The pilot return path is also the vehicle ground. The DC /DC is very small and only $4. I should be able to test this configuration in the next few days.

 

[richkae]

To build the home EVSE you probably need similar cable that is used in the HPC between the box and the connector.
The chunk of cable in the Tesla J1772 adapter is labeled: 2/C 6 AWG 1/C 8 AWG 2/C 16 AWG EVE 105C water resistant 60C 600V
I'd like to build something without a J1772 end on it - where would you get cable for that?

 

[Kevin Sharpe]

where would you get cable for that?

hcsharp is working on a 63A "mennekes-to-roadster" cable... maybe they'd sell just the cable with Roadster connector attached.

 

[PV-EV]

I too would like to build the EVSE to plug directly into our Roadster. Essentially a DIY HPC Most likely I will have to modify our Spare Mobile Connector. Has anyone disassembled this connector?

 

[dwegmull]

I made some progress on my own EVSE. David Wegmuller - Google+
My schematic is a bit different than the others: I had a PCB mount power supply that has a single (double insulated) 24V output left over from another project, so I used a virtual ground to create the +/-12V needed by J1772. The op-amp shown in the schematic is not the one I ended up using. I'm using an LM6144.
The software basically works, but I would like others to look at it to point out any problems with it. I will clean it up (lots of debug code right now) and post it. It is just over 200 lines in Arduino (which is really C in disguise) code.
Now I need to sum up the courage to connect the circuit to a live 240V outlet...

 

[TEG]

It looks like there is a little momentary switch on the PCB... Is that a reset switch?


Is there a way to select different pilot signal levels?

 

[hcsharp]

I too would like to build the EVSE to plug directly into our Roadster. Essentially a DIY HPC Most likely I will have to modify our Spare Mobile Connector. Has anyone disassembled this connector?

I built my own HPC and the total cost was under $400. That included the Roadster connector which I built myself from scratch and rated to over 70A.

I'm working with a machine shop to produce more of the roadster connectors and hope to be able to sell them if there's enough interest. Not sure what the price will be but hoping it will be similar or cheaper than the cost of a spare mobile connector. I know that sounds high but I won't be making much money. I've built 6 prototypes and it's not easy! Even if you buy a spare mobile connector from Tesla, at a minimum you still have to drill and tap for a larger strain relief, drill out the sleeves inside to re-crimp for larger cable. I also have some EVSE cable rated to over 70A but can't sell any for a couple of weeks until I know how much I have left over. It will be approx $10/ft. I hope this helps.

 

[vfx]

I'm waiting for Tesla to offer their new socket for the Roadster.

 

[Lloyd]

Then we are waiting for Tesla to offer their new cable to the exisitng HPC.

 

[dwegmull]

It looks like there is a little momentary switch on the PCB... Is that a reset switch?


Is there a way to select different pilot signal levels?

The switch is indeed a reset. It came with the Boardunio... At this point, the entire design revolves around plugging into a dryer outlet (everything is sized for 30A max, 24A continuous), therefore it is set to 24A. Adjusting the PWM duty cycle is a one line change in the software.
I might buy some twist lock plugs with extra contacts to make "smart" adapters for various outlets that would set the current limit accordingly... I know of at least one place where a 16A "welder plug" would come in handy. Being able to use two 120V outlet from two phases at either 12A or 16A could be handy too.
First, I'll get the basic unit going and then give in to feature creep ;-)

I have collected most of the documentation, including the source code here: Welcome to Google Docs

 

[richkae]

But nobody has a mail order source for 70 amp capable EVSE cable?

 

[W.Petefish]

But nobody has a mail order source for 70 amp capable EVSE cable?

J1772 or Tesla?

 

[dwegmull]

But nobody has a mail order source for 70 amp capable EVSE cable?

Here: J1772 Adapter