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Forum Index : Electronics : Timer/voltage sensitive relay with arduino
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| Godoh Guru  Joined: 26/09/2020 Location: AustraliaPosts: 529 |
I don't know anything about coding, but am wondering if it is possible to use an arduino to replace what I now use a timer and voltage sensitive relay for. At the moment I use a timer with inbuilt relay to turn my inverter on in the morning and off in the afternoon so the GTI inverters can back feed when the sun gets on the panels. I also use a Voltage sensitive relay set to turn the GTI inverters off when the batteries are fully charged. At the moment I turn the GTI inverters off when the batteries are 28.8 volts and then they come back on when the battery voltage falls to 26 volts. Just wondering if it would be possible to use an arduino to do this job and also to switch a solid state relay or Mosfet so I can do away with the mechanical relays. Does anyone know if this is feasible or worth the trouble doing? cheers Pete |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2580 |
It is feasible but if you don't have much coding experience Arduino C++ can be steep learning curve. Young minds can manage it readily enough but I have abandoned it. All versions BASIC are far easier to learn and for your application maximum execution speed isn't needed. So an interpreted version such as MMBasic is easier still as no compiler is needed. MMBasic has a built in editor so the program can be written end modified in the chip with just a terminal program. A PicoMite (a R Pi Pico with MMBasic firmware) would be my choice. Its very cheap, firmware loading is just drag-n-drop to its USB port which then becomes its serial console port. The TBS Microcontrollers forum is largely PicoMite so you can get plenty of help there. Firmware and manual here https://geoffg.net/picomite.html Edited 2025-06-27 18:42 by phil99 |
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| Godoh Guru Joined: 26/09/2020 Location: AustraliaPosts: 529 |
Thanks for the reply Phil, I will have a look at the site you mentioned. It will depend on how I go with learning the lingo. So far i have had trouble with the cheap relays failing on the voltage sensitive relays so have ordered some solid state relays to replace them on the boards. If they work out reliable then I may stick with what I am using. Cheers Pete |
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| analog8484 Senior Member  Joined: 11/11/2021 Location: United StatesPosts: 145 |
Assuming everything is working fine besides the failing relays, it would be easier to use the voltage monitoring relays to drive bigger more durable contactors (inexpensive central A/C contactors have worked well for me). Of course, if you are looking to learn Arduino then it's certainly a doable project. Edited 2025-06-29 03:41 by analog8484 |
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| Godoh Guru Joined: 26/09/2020 Location: AustraliaPosts: 529 |
thanks for the input Analog, i had a look at mmbasic and figure the complexity of learning it and the extra parts needed is probably too much for my tiny mind As you say the system works well, it is sometimes let down by cheap components, but i will add more robust solid state relays and leave it as it is. I have three of these systems working at the moment, as two sheds have their own solar systems as well as the house. thanks pete |
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Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1151 |
Just a quick search for some examples. https://forum.arduino.cc/t/voltage-monitoring-with-timer/572163 There are likely many others around, just interesting seeing what others are working on. Cheers Aaron Off The Grid |
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Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1435 |
Pete just think about this in logical steps and write them down as they come to mind  So all we are doing is monitoring voltages and when preset voltage is reached things are turned off until another preset voltage is reached. Get the picture mate Now the manual does show clearly how one can set things up so grab a pico and a touch LCD and take baby steps while you learn. In the long run I will be looking to do the same mate for my setup so lets do this together so we can reach that goal. Cheers Bryan |
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| Godoh Guru Joined: 26/09/2020 Location: AustraliaPosts: 529 |
Hi Bryan, yes the voltage monitoring part doesn't seem that difficult, I also want the unit to do what my current setup does, which is turn the inverter on in the morning and off again in the afternoon. I adjust the turn on and off times to suit the time of year and the time the sun hits my panels too. So when the inverter turns on the GTI inverters wake up and start to backfeed into the batteries. When the batteries are full the voltage sensitive switch turns the GTI inverters off. so the steps I would need are. Turn relay on to switch battery inverter on at say 9am Voltage controlled relay then measures battery voltage if battery voltage is below 28.8 volts, Then the relay closes and switches the GTI inverters on( the GTI inverters are fitted with relays inside that i put there to cause them to anti island when the relays are switched off) When battery voltage rises to 28.8 volts then switch relay off. When it gets to 4pm in winter then open the relay to switch the battery inverter off. In summer I need to adjust that setting easily to 5pm or even 6pm So the 24 hour clock needs to be easily adjustable.. Pete |
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| Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1435 |
Pete if I have this right one relay to the main inverter and one relay each for GTI's so that makes it 3 relays to switch in total. Now the pico board could go in sleep mode over night if the board is in your shed and a LDR ( Light Dependent Resistor) could easily wake the board each morning and shut everything down at night. A LCD would be good so you see what everything is doing and it could all done via the GUI method where each event has a number etc. So basically a few LED's that flash green when on red when off, the current time and date would be handy and a input box where one change the start and finish times. Now by writing all this down does give the idea of what has to happen then we can break it down to step by step until we have everything. Now like you I can think about what I want to do but putting that into code has always gone on the backburner as the grey cells kick in. Cheers Bryan |
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| phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2580 |
That could entirely replace the clock and calendar on / off times. Another option, instead of the LDR is to monitor the panel voltage. When it is high enough to power the GTI switch it on and when the panel voltage falls to the point where the GTI is no longer useful switch it off, unless high Vbat has already done that. |
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| Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1435 |
Don't forget Phill Pete is in Tasi where cloud cover and rain are the norm  so the LDR may just be the best option.So in the morning the LDR switch's everything on and monitors the battery voltage now if it is a rainy day and has been for days a low cut off point would need to put in. Now if Pete wanted sound the pico could send a message when the batteries are too low "turn on the genset ya wanker" could be the message Aussie style. |
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| Godoh Guru Joined: 26/09/2020 Location: AustraliaPosts: 529 |
Hi Bryan, I only need one relay to switch the GTI inverters on. And one to turn the battery inverter on. At the moment I use a timer to turn the battery inverter on, and the voltage sensitive relay board to turn the GTI inverters on and off. I plug both the GTI inverters into the voltage sensitive relay board now and it turns them both on and off together. An LDR sounds like a good way to go. There are days when the cloud cover is so thick that we get no solar input at all. Fortunately they are rare, and we have enough battery storage to go for at least 3 days without taking the batteries below 70% charge. We don't have a back up generator. We had one but didn't need it so we gave it away. As an emergency ( which hasn't happened since adding more panels) we have a 5 hp motor that runs a car alternator. I delta connected the alternator so can pull 50 amps from it if required. It hasn't run for about 3 years now. Thanks phil and bryan for the input Pete |
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