Author Topic: Control for heating with solar off grid no batteries  (Read 15901 times)

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ontfarmer

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Re: Control for heating with solar off grid no batteries
« Reply #108 on: March 23, 2017, 04:51:10 AM »
I will check that and get back.  Thanks

OperaHouse

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Re: Control for heating with solar off grid no batteries
« Reply #109 on: March 23, 2017, 07:04:52 AM »
A FET can be damaged by a static charge to the gate. Puncture occurs when voltage on the
gate exceeds 20V. Even a minimal puncture can cause the device to fail a long time after
that has occurred.  It is a good idea to place a resistor from the gate to the source before
building the rest of the circuitry.  This will prevent damage from a floating gate either
in construction or an inadvertent disconnect. A failed FET almost always has a short from
the gate to the source. A floating gate can cause the FET to partially turn on causing
excessive heat and then failure.

So, it might be a good idea to have a pulldown resistor on each gate so if one FET is
removed or common is lost, the other one is still protected. A 1.5K resistor on each gate
would work.  That program is from another project I was working on and I changed the A/D
input and output pins.

ontfarmer

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Re: Control for heating with solar off grid no batteries
« Reply #110 on: March 29, 2017, 04:39:47 AM »
Very Happy day yesterday I got the uno working.  The day was perfect for testing, heavy
overcast to bright sunshine back and forth several times.  Just have one pin operating at the
 moment but will hook up the other one.

DamonHD

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Re: Control for heating with solar off grid no batteries
« Reply #111 on: March 29, 2017, 06:35:40 AM »
Well done!  Hurrah!

Rgds

Damon

ontfarmer

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Re: Control for heating with solar off grid no batteries
« Reply #112 on: March 29, 2017, 07:43:16 AM »
Thank you. I hope to have a better understanding for the next ones.

OperaHouse

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Re: Control for heating with solar off grid no batteries
« Reply #113 on: March 29, 2017, 08:36:19 AM »
So, does it actually seem to hold the voltage at power point?  Are the FET running cool.  How big is the load?  Did you do anything to adjust it?

ontfarmer

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Re: Control for heating with solar off grid no batteries
« Reply #114 on: March 29, 2017, 09:15:31 AM »
Yes the voltage says at power point.  The load varied a lot through those conditions yesterday.  At the end of the day when I checked the load voltage was 18  the panels130.  Just have one fet operating off pin #3 it is hooked to a 750 watt  240 volt baseboard heater and the fet  is only warm.  Going to hook up another heater that is the same to operate off pin #11 with its own fet.  Have not done any adjusting yet,  could use some help with that.
I am going to take one of the panels out of series and put it back in parallel. That will drop
the voltage  by almost 40 volt. Will the code have to be changed ?

ontfarmer

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Re: Control for heating with solar off grid no batteries
« Reply #115 on: April 01, 2017, 09:14:48 AM »
 Installed a second opto-isolator and fet.   Got the second baseboard heater hooked up which
is controlled from pin #11 on the UNO.  Today is perfect for observing the performance heavy
cloud cover to bright sunshine changing frequently. Drive #1 , #2 vary from both on full power to partial  power on just drive #1.  Very happy to see this is working.  Want to let you guys that have been following this know.

DamonHD

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Re: Control for heating with solar off grid no batteries
« Reply #116 on: April 01, 2017, 11:03:52 AM »
Thanks for the update: it's good to know when things work, as well as when they don't!

Rgds

Damon

OperaHouse

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Re: Control for heating with solar off grid no batteries
« Reply #117 on: April 01, 2017, 11:11:41 AM »
Good job, you'll be doing a youtube video next. I'll need to do a 4 heater version next. It is tax time and the desk is cleared off for that for a while. How many adjustment pots do you have in the system now?  If you hav an old analog dc meter, it can be used to make the adjustment. Just tune for higher voltage. Software update will come soon. Buy more fets.

ontfarmer

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Re: Control for heating with solar off grid no batteries
« Reply #118 on: April 02, 2017, 04:59:43 AM »
Will not be doing a youtube video.  It has been quite a trip for me getting this far.  I am starting to get a bit of  a idea of how and why this operates.  There are two adjustment pots
in the system now.  I have a old analog meter that can be used.  No rush on new software
just when it happens.  ( still in amazement watching the load on the drive  change on this one )  My plan was to have two systems,  six panels on each  one.  Should I be thinking different ?  Have more fets on the way.

ontfarmer

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Re: Control for heating with solar off grid no batteries
« Reply #119 on: May 08, 2017, 04:15:29 PM »
Just an update  to let you know that the unit is working.  The load is controlled so the solar panels maintains  power point voltage.  The fets only get slightly warm. A very slight change
of brightness to the panels and the load changes instantly.

OperaHouse

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Re: Control for heating with solar off grid no batteries
« Reply #120 on: May 09, 2017, 12:21:32 PM »
Sounds good. I'll be getting back into it shortly.Currently laying out a general purpose
board with a small capacitor bank and up to six FET. This will be be the base for a one
or two element MPPT heater, heater and MPT buck converter, linear current booster for
running a pump motor without a battery, and whatever I dream up in the future.  This will
make it easier for others to build these projects.  Then I will have to start cleaning up
and standardizing the code.

george65

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Re: Control for heating with solar off grid no batteries
« Reply #121 on: May 10, 2017, 11:25:22 PM »

If you could put up the code and the board schematic it would be a great help to a lot more people than just the code itself.