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I purchased a v2 30A kit almost 2 years ago and I'm extremely pleased with it. Now that I've finally upgraded the firmware, I'm of course seeing 0's for nearly everything on the display.  So, in DIY form, I'd like to add the current sense circuit. Except for finding a 28 ohm resistor, it should be very easy to assemble, then a little tricky to attach to pin 23 of the 328p.

My plan is a perfboard with the requisite parts and coil connector, adequately insulated and 'suspended' between the ground bar and the board. Wires to the board for 5v and pin 23, ground to the bar.

Apart from the obvious:

1. Don't short anything out onto the aluminum case.

2. Be careful soldering a wire onto the 0.4mm pin.

3. You're going to try soldering a wire onto a TQFP32??? :)

Does anyone see something I've overlooked or a (serious) problem doing this?

Regards,

-Paul

Cool. I'm trying to locate the appropriate combination of resistors to make the current sense appropriate. What calibration 'knobs' are there to tweak in the firmware if I can't get close enough?

What precision should I aim for when selecting the combination for the 28 ohm? I'm looking at 3x 10 ohm 10% in series hoping to get three sub-10 ohm to get close.  Or if I can find a 68 ohm to put in parallel with the 47's I found to get ~27.8 ohms.

Sorry, hadn't found that bit in the code when I asked.  Order is in! :)

 

The retrofit was a success - I probably need to do some calibration but I'm still figuring out how I want to do that. It's actually not that hard, except for finding a place for the current tap and still fit everything into the aluminum box. :)

 

If anyone is interested, I can create a guide for doing this.

-Paul

Paul,

Just read your retro fit for the EVSEOpen V2 board to add current sensing circuit,

Cool it works!  I'd like more info on how to retro my V2 board too.

If you could put together a guide that would be great!

I just upgraded the FW and I hate just seeing those Zeros. 

Jeff

 jeff,

  I still could. Of course, I'd need to re-learn everything I did, and take pictures. I'll consider starting a guide but it'll take me a while to disassemble everything again.

-Paul

Hi Paul,

Thanks for the reply.  If you could list the components and circuit layout

for the current measurement circuit in a how to guide, that'd be great.

I look forward to the V2 current sensing circuit retrofit guide.

Wondering if you did the (3) 10 ohm resistors in series, or the combo resistors

in parallel to get close to 28 ohms.

Thanks!  Jeff

Paul,

Was wondering if the current sense circuit also includes

the circuit that I circled in red.

Are there only (3) connection points to the OpenEVSE board?

1. R25 to +5V

2. GND to R21

3. A_CT pin 1 to the MEGA8-AI pin 23 ( AMP READ )

or am I reading it wrong.

Jeff

Paul,

Does the current sense circuit also incude the circuit that I circled in red?

Are there only the (3) points to connect the circuit to the Open EVSE board?

1. R25 to +5V

2. GND to R21

3. A_CT pin 1 to the MEGA8-AI pin 23 ( AMP READ )

Thanks,

Jeff

No, that would be the input power filtering already on the board.

As I said, I need to disassemble my unit to figure out what I did and take pictures. I wasn't bright enough to take pictures while I was doing it apparently.

-Paul

Sorry, I missed your other question. Yes, those three points. Ground, +5v and the microcontroller.