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  1. #11
    I've finally got it working to a reasonable level . . plus there is some actual machining in this one!

    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  2. #12
    Making some improvements - open loop to self-calibrating closed loop!

    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  3. #13
    Great set of videos! Iíve got a similar problem and wanted to ask about how to build the AC side of the circuit. I have the power data scraped from the inverters modbus port so just need to simulate the signal for the harvi.

    Iíve found some ac 240v to 5v transformers so was planning to put that into a small box with an esp32. Then use the esp to generate the signals to control the simulated ct clamp.

    I just canít work out what components youíve used or how the ac part functions. How does it deal with the ac? A lot of the components Iíve found for variable resistance only allow dc

  4. #14
    That’s why it took several months to solve the problem. The Harvi needs a varying AC current to determine the current in the cable (using a CT clamp). Getting a simulation of this signal took some working out.
    My solution uses an AC transformer (AC to AC) and an LED/LDR combination to control the AC current. I couldn’t find another way to do it. The LED is pulsed by the microcontroller and this varies the LDR resistance in the AC side. That is the principle but it also took several hundred lines of code.

    What system have you got in terms of panels, batteries, and inverter?
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  5. #15
    Iíve got a solis hybrid inverter with 48v dc coupled batteries. I had botched some code to read the inverter registers but then someone else wrote a really good integration for home assistant. It can read out all the power info from the inverter and can even can control some inverter settings.

    Unfortunately the myenergi api doesnít allow for sending data otherwise it consuls all be done in software.

    Your solution is a great workaround to send info to the system. I have a lot of work on currently but am going to look into the variable ac signal control some more. Im hopeing someone makes an ic designed for the task. I found a digital potentiometer on RS that can deal with AC up to 12.5V (MCP 4551)

    The only issue is the current limit is really low, 2.5mA so out of range from what you found for the ct clamps.

  6. #16
    Ok my batteries are 160V so probably helps with a detectable level of current for my CTs. What sort of DC current flows there in your system? Would a CT detect it? You can wind the cable around them multiple times to upscale it, assuming the cable will bend enough!
    After that you are into intrusive options like shunt resistors and current sensor boards but you will have to decide how safe those are, insurance risk etc.

    Software interfacing would be a great option as it is so customisable compared to hardware solutions. These always have a valid range of operation which means many options are not suitable.

    The other thing I looked at was the main chip inside the Harvi can read all sorts of protocols including i2c which is what the Arduino can output! But it would require significant changes to the Harvi and probably more knowledge than I have. But it would cut out all the AC current creation and just tell the Harvi the current level directly, but still would need the CT clamp to detect it.

    Also try posting on the myenergi forum and I think there was a Home Assistant forum too?
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

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