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Remote Serial Terminal Connectivity From Anywhere DT-06 WiFi

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LoadMaster XP - A Smart PV MPPT Solar Hot Water Controller

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  • LoadMaster XP - A Smart PV MPPT Solar Hot Water Controller 5 days ago

    Hi Vladimir.
    This sounds like PWM switching noise is somehow getting into the digital ground or being picked up in cabling. How have you assembled the circuit? - made a PCB,? used 2oz copper, stripboard etc? The layout is critical and requires a good attention to the segregation of Power Gnd and Digital 0V with only a single point of them joining at the current sense resistor. No PV switching currents must find their way into the digital side of the circuit. The Inductor, Capacitor and Diode on the output side are key to slowing dV/dt and dI/dt and this reduces the radiation of switching noise which could potentially corrupt sensor comms (are they fitted?).

    Loadmasters Power (PV) Gnd & digital 0V must remain isolated from earth. Have you seen the sensor wiring notes in the 'External wiring diagram' of the 'Assembly notes' document in the downloads section? (i.e using twisted pairs in ethernet cable with the cables shield connected to PCB main ground point (U12) at loadmaster end only). Does the Water cylinder have a good earth connection? and are all sensors & sensor cables isolated from earth at the cylinder? Avoid running the sensor cable adjacent to the Heater power cable. If you still have problems, please drop me an email PVhotwater@btinternet.com. Cheers Steve

  • LoadMaster XP - A Smart PV MPPT Solar Hot Water Controller 22 days ago

    Hi Isdeekelis
    Many thanks for your interest and compliments. It sounds like you also have a very interesting project going on there.
    Why 5Khz...(its currently at 3.9kHz), well, initially I had problems getting high PWM frequencies and reasonable PWM resolutions on a Nano, however that's now achievable. As the basic principle is Capacitive energy storage I was aware dielectric and switching losses could rise with freq (but probably still unimportant - just couldn't find data for many caps etc), There is some audio noise (see assembly doc) but its really minimal. I modelled the cct in TI tina and then ended up at a common cap value and freq giving only a few Volt ripple in the PV Vmp volts. Basically! i haven't had a major need to try higher frequencies - maybe one rainy day i will test it out.
    Use a pre-set range etc for Vmp? - Well up until 2 days ago! I had never seen a problem of multiple peaks in an arrays power output - a project builder having an array of mixed panel types reported an issue were it could lock on to a lower power level peak. In many systems, with an array comprised of the same panels and with no major shading issues then there has been no sign of an mppt tracking problem. Adding some Vmp acceptance window in the P&O mppt code could definitely be an option to fix that. As far as I am aware many Mppt routines just assume a normal V-I curve and single power peak. (if you see any code for that I would love a copy)
    All the best for your project, Steve

  • LoadMaster XP - A Smart PV MPPT Solar Hot Water Controller about 1 month ago

    Hi Craig
    Thanks for your interest in the project. You will most definitely see a benefit from using mppt in winter months. At the moment I am holding back a little from publishing the PCB gerber data. There is now a growing number of systems working and being made around the world and I wish to collated any feedback from those prior to releasing artwork etc. I have some PCBs which I can supply. Please drop me an email to pvhotwater@btinternet.com, Cheers Steve

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