The Story of SIT: It all started with replacement of old 500 watt system with VM-III 3kva with 2.7kva Solar Panels. VM-III seems to be quite intelligent as compared to the older system. I had routed power to One Air Conditioning Unit , Water Pump, Refrigerator and Microwave Oven through VM-III; with the intention that during electricity failure my solar will keep home running even though I have to ration power to ONE big appliance at a time in addition to normal small appliance usage. So far so Good. Installation went well and the Dashboard display keep telling me Solar is taking-up major load.

The first shock came, when despite monitoring through out the day over few weeks the Solar system failed to cross 2kva of Solar Production. Where is this extra 700 watt is going? Is there any bad panel installed within the array? Checking with supplier and reading the manual I came to know 3kva is not actually 3kva; its 24v x Max charging current ie 80A = 1920 Watts. So the system which I thought is 3Kva Solar is infact 2KVa Solar and 3Kva Overall load limit.

The second shock came in middle of the night when Grid tripped and the whole load shifted to batteries. Did I mention I had not invested in batteries and around 200MAH only batteries were there for backup. So within few minutes there were buzzers going on as the inverter was unable to produce required Amperes from batteries and I had to turn off few appliances to bring it into range. Again a call to the vender next morning, that how to take off few items off the system, but only when at night there is no Grid power. As per his statement there was no remedy as installation of batteries is must which I avoided. Here came the first customization with help of a timer switch and a relay, the system would only provide power to big Appliances during 9:30 to 15:30 hours in case Grid power is not available.

The next shock was when I tried to play smart with Timer Setting of the inverter when to switch to Solar only and when to use SUB settings. Well I ruined it, yes it was my fault, the inverter would switch to Solar only setting during peak Solar hours. But now it also tries to switch to Solar at 00:00 hours; right in mid night. Another call to vender he helped in doing a factory reset and every thing went well, and for couple of hours I will get a Solar only auto switching too. But after few weeks the inverter was again trying to switch to Solar only in middle of the night !!!. Anyways long story short now SIT checks if inverter tries to switch to SOLAR only in middle of night, it automatically corrects it to SUB settings.

The next shock was when One of the Grid Phase went off. Yes it was the one on which inverter was connected. My fault again, I had shifted all appliances and light sources to that ONE phase. I have power in other two phases but inverter wouldn’t get them. I have designed a solution to this with help of two automatic switches usually used in diesel backup generators when grid power is not available but this is yet to be deployed.

If you remember the first shock mentioned above, you would have already guessed that in best of the circumstances when there is no Grid power I would only get max 2kva Power from Solar at peak hours and with Grid Power max power I can draw is 3kva and the load I have installed is more than 5Kva , So it’s became a second nature to manually manage Power usage every now & then when our inverter will exceed its capacity as most of the times the Air Conditioning and Microware would go into usage together or while Grid is Off and Air Conditioning is ON our beloved Clouds will test the installed capacity. The requirement of an Intelligent system to manage load was apparent. Further, I want to route Solar Power to other appliances too, which I cannot do with a dumb inverter setup. A solution to this problem is again designed but yet to be deployed as additional Software is yet to be written and hardware yet to installed.

Anyways, the blessing came with Covid lockdown and I got time to look at my long pending wish list in which DIY upgrading of my Skywatcher EVO 150 with EQ5 to Goto capability was listed. By that time I have heard the word Arduino from a physics nerd but other than that I had no idea about it. Google as usual came to help and I ended-up finding OnStep solution for this DIY. Thus, resulting in ordering all the parts from Ali Express. Due to Covid the shipments got delayed and what one would do in lockdown waiting for parts. YES!!! Right I decided to do some research on Arduino so when the parts arrive I could easily assemble and install them. Youtube took me to Paul McWhorter channel, which definitely gave me the idea of controlling turning ON/OFF my Air Conditioning based on Inverter’s data that I could derive from it’s communication port. At the end, I ended up writing around 6000 line code that resulted in SIT.

The journey continues auto routing of Solar Energy where needed and auto avoiding Overload are still to implement.

I addition to above, there was many websites which helped in learning and development of SIT, I would specifically like to mention W3Schools and RandomNerdTutorials here, though my Favorites bar is full of links now.