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Thread: OpenEVSE build

              
   
   
  1. #1
    Empulse R #24 frodus's Avatar
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    OpenEVSE build

    I got the OpenEVSE last year and totally slacked on building it. My Brammo came with an EVSE, so I had very little reason to build it. Decided to finish it up this last week while it was rainy. Very easy kit. It's flexible enough such that you can spend as much or as little as you want. I went inexpensive on this build.

    I first bought my OpenEVSE kit when they were getting the orders in. Now they have an online store.

    The main page is here:
    http://code.google.com/p/open-evse/
    The store is here:
    http://openevse-store.myshopify.com/

    Here's what I bought:

    1 - OpenEVSE Plus v2
    1 - Current Transformer
    1 - RGB LCD[/li]
    1 - Leviton J1772 15A charge cord
    1 - NEMA 5-15P from the hardware store
    2 - cable glands from the hardware store
    2 - 3' length of 12GA 3-conductor SO cord
    2 - 120/240VAC 20A relays with 12V coils from a local surplus supply
    2 - CC type DIN rail mount fuse holders with 20A time delay fuses installed
    1 - 20A terminal for ground connections

    Stuff I scrounged:
    1 - Plastic enclosure with switch from the trash at work
    1 - 20A terminal for ground connections
    1 - 4" length of DIN rail
    2 - DIN Rail clamps
    Various screws, cables, etc that I had laying around.

    Assembly was pretty easy. I decided to just mount the LCD to the plastic subpanel that was already installed inside the enclosure I got. Relays, DIN rail and the OpenEVSE board mounted right to the back panel. Wiring was pretty clean and easy.

    Here's what it looks like:
    [img width=400 height=225]http://www.evfr.net/coppermine/albums/openevse/normal_20140511_234101.jpg[/img]

    [img width=400 height=225]http://www.evfr.net/coppermine/albums/openevse/normal_20140511_234119.jpg[/img]

    When I first plugged it in, I could hear the relays clicking (part of the test routine), and the LCD was lit, but it didn't display anything. On the back of the LCD, there's a contrast potentiometer and it was turned all the way one direction. After removing the LCD and adjusting, the LCD displayed a few boot screens, then "READY".

    There's a few settings the user can get to using long-press on a pushbutton. It allows to enable/disable some of the tests, setting of MAX current, etc. The LCD has an RTC, so it keeps the time. You can also set up charge delays. I haven't flashed the latest firmware and I'm not sure what any of the new the options are, but it's all Open, so it would be fairly easy to change things a little. I know there's a serial connection available for a remote terminal. Right now this is for setup only. The Current Transformer is so that the OpenEVSE can detect a ground fault and stop charging.

    Overall it was pretty easy to build and will allow me to do L1 and L2 charging at 15A, which is the limit of my motorcycle. I could have built it a bit smaller, but I could fit this in a backpack, or in my topcase when I finish designing a rack for the Empulse
    Last edited by frodus; 12 May 2014 at 1020.
    Travis

  2. #2
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    I've built two of these to date - one for my own Leaf and one for a friends.

    Like yours I have mine configured to charge at L1 or L2 but I get it to do so based on which power cable I use to plug it in, so that if the wife finds herself needing a charge off a domestic socket it automatically limits charge to 10A without her having to do anything, but with the 16A pluglead attached is selects the full 3.6kW charge rate. No buttons, no settings, fully sealed, and completely idiotproof.

  3. #3
    Senior Member jonescg's Avatar
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    Spoonman - that's cool. How do the smarts inside the pilot pins determine whether or not you're plugging into a 10 A, 16 A or a 32 A connection?

  4. #4
    Empulse R #24 frodus's Avatar
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    The power supply is wide voltage input and works with 120/240V. The AC detection on the board knows what voltage it is.... So just set to auto.... Set your current and go. I think you have to change L1 and L2 currents separately. Haven't tried yet.... As I only use 120V.

    Is all in the software and it's all open and new stable builds are posted online on github.
    Travis

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    Different over here Frodus - everything is at 240V so you can't rely on voltage level detection.

    My EVSE is a box with a 5-pin plug for power in and the standard Mennekes socket for power out.
    On the input side, in the power lead, 3-pins account for Phase, Neutral and Earth. The other two carry a resistor.
    That resistor ties to one of the Arduino ADC pins and ground when the lead is connected to the box, and acts in a pulldown config on the ADC pin (there's a pullup resistor hardwired on the board).
    A high value resistance (>5k) produces an ADC value which is greater than a predefined threshold in the code - this instructs the duty cycle of the pilot pulse to be reduced to limit current draw to 10A.
    A lower resistance reduces the ADC value and instructs the code to extend the duty cycles to allow 16A charging.

    So the lead with the standard plugtop on it, has no sense resistor in place (infinite resistance) - meaning that the ADC is always topped out and the charger selects 10A charging.
    The lead with the 16A connector on it though has a 1k resistor between terminals 4&5 - meaning that the ADC value drops and the charger selects 16A charging.

    In this manner the system is fully scalable - declaring different ADC ranges, you can associate any number of leads with any desired current draw simply by installing the appropriate resistor.
    Sense resistor failure in an open state leads to 10A charging so no danger there, and there's a lower threshold on the ADC as well to account for a short circuit failure just in case - which also leads to 10A charging.

    So ultimately this means that I can charge at the full whack at places like my folks house or camping sites where there's a 16A connection available, and simply plug into a domestic socket anywhere else (within reason) without fear of doing any damage.

  6. #6
    Empulse R #24 frodus's Avatar
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    Oh cool! Neat way to do it!

    What openevse Rev do you have?
    Last edited by frodus; 13 May 2014 at 1100.
    Travis

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    It started out as v0.5.0 but it's fairly significantly modified from that now - all the serial data comms code is stripped out, as is the ground fault loop code (I have an RCCB in the main loop so it's redundant), and with those cut, then the watchdog code can go as well.

    After that it's just a few new pin definitions, a modification/hijacking of the m_bFlags value, and a readjustment of the default and max current settings.

  8. #8
    Empulse R #24 frodus's Avatar
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    I don't mean code.... I mean board Rev. I'm using the openevse plus v2.

    Hes doing a v3 that will have some more features. Check out the forum on their page.
    Travis

  9. #9
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    oh - no that's my own layout.

    The original was done on a proto-shield, but i subsequently revised that to a custom PCB (on an shield footprint).

    Drew it up in Eagle and outsourced the etching to a crowd called PCB-pool who I use reasonably regularly (although I'm hoping I won't need to soon enough as we're taking delivery of a Stepcraft 300 in work in the next few weeks )

    There are a couple of very minor fitment errors in it, but I just patched them appropriately and it works perfectly.

    Have been meaning to do up a second revision which incorperates the patches but haven't bothered yet.



    I haven't been keeping an eye on how the actual OpenEVSE has developed since - will swing by the forum and take a look.
    Last edited by Spoonman; 15 May 2014 at 0133.

  10. #10
    Empulse R #24 frodus's Avatar
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    The upcoming V3 has:
    - IEC proximity pilot to auto detect cable current
    - 3rd relay output for AC contactors up to 240V
    - 2 12V outputs that can be used for IEC cable lock/unlock actuators (or DC relays)
    - current measurement

    Thread is labeled: increasing power/current
    Travis

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