Author Topic: Arduino inverter load controller  (Read 23488 times)

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ontfarmer

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Re: Arduino inverter load controller
« Reply #33 on: June 23, 2016, 07:24:29 AM »
Up date I have arduino uno,  9 volt wall wart.  Capacitors and relays are on order.

What else should i be getting?  Will  something be needed to cut the 135 volt from the panels

back for the uno?

Thanks

OperaHouse

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Re: Arduino inverter load controller
« Reply #34 on: June 30, 2016, 04:46:39 PM »
For other readers this project is a basic dump load controller that could be used on a
mill with slight modification. The same thing could be done with a GHURD controller.

I have to ask what what experience you have in electronics and equipment available.
Also, what parts stock do you have available?  Out town has electronics recycling and
I pick up an old UPS every chance I get.  Become friends with the dump guy, bring him
a bottle of Ripple wine.  Point is there is electronic waste everywhere.  An old plasma
TV has almost two dozen great FET to use in projects.

The 9V wall wart is fine for powering but it doesn't have enough voltage to  insure a FET
is driven into full saturation.  Keep looking till you find a 12V to 15V one.  You have
enough power to use two wall warts.  Placing a common 5V wall wart in series with the 9V
will supply enough voltage (14V) for the driver section.  Some of these are polarity
sensitive and will only work on one polarity when connected to the solar panel bus.  If
you find a higher voltage wall wart the voltage can be dropped to 9V with about 5 or more
diodes in series.  The input of the UNO will work fine with 12V input but the on board
regulator is small and tends to overheat with higher input voltage.  If a lot of stuff
is added an external 5V regulator should supply that.

The standard software of the UNO has a PWM of 490Hz.  Such low speeds are very forgiving.
I use opto isolators to drive the FET.  They are slow, the turn off speed is about four
times slower that the turn on. The transitions are often the biggest source of FET heating.
When operating at 20KHz and higher these transitions are critical, not at 490Hz.  A lot of
people want to use a real FET driver so they look professional. If you are not very experienced
these driver chips can get you in a pack of trouble.

Have you settled on a FET yet?  Select one with at least 250V and plan on using three in parallel
with them being at least 15A each.  Tried any programming yet on the UNO?  When you get to making the capacitor bank, make it simple to disconnect about 5 caps at a time so a shorted cap can be found easily.  You should start your own thread to document the project.
« Last Edit: June 30, 2016, 04:53:01 PM by OperaHouse »

ontfarmer

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Re: Arduino inverter load controller
« Reply #35 on: July 02, 2016, 06:04:04 PM »
   I have very little knowledge on electronics. Have a lot of knowledge on mechanical,
 electrical, hydraulics, pesticides. Learned quit a bit ( for me ) recently studying electronics.

I have equipment and experience with ( some guidance ) to put this together.

Have local recycling on electronics, a bit in surplus stores, most has to be ordered.

Might be able to get fets from a TV ?

Read the programing of the UNO but have not done it, Received the capacitors and soldered  them in groups of five.



Mary B

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Re: Arduino inverter load controller
« Reply #36 on: July 03, 2016, 09:32:09 PM »
Be very very careful of that capacitor bank! You have enough instantaneous current to melt those wires if they short!

OperaHouse

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Re: Arduino inverter load controller
« Reply #37 on: July 05, 2016, 11:40:12 AM »
It can pack a wallop.  I suggest initial testing only be done with one bank of capacitors.  The bank will be at a fixed voltage, peak current will always be the same.  Only the pulse width will change and the average power.  For this reason the power module should be placed as close to the load as possible.  Since it is opto isolated, the micro controller can be placed 100 feet away from the power module with no problem.  The wall warts can also be placed at this location with cheap telephone cable bringing the signals to the micro.  It is a good idea to connect the high voltage sense lead through a 47K or higher resistor.  That will become part of the voltage divider and prevent any cable short from burning up a light cable wire.  These are lethal voltages so protection against touch should be implemented.  A bleed resistor, around 300K, should be included to discharge the capacitor bank when the system is off.

A new thread should be created rather than hijacking this one.  I'd like to hear what Rich is presently doing with the system.   When you get down to about 30V with those SMPS power supplies some extra voltage margin can be gained by shorting out the diode and the resistors (for EMI filtering) in series to the main cap.  These can often add up to more than a dozen ohms.  Two to three volts can often be gained which is a lot at 30V.
« Last Edit: July 05, 2016, 06:26:57 PM by OperaHouse »

ontfarmer

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Re: Arduino inverter load controller
« Reply #38 on: July 05, 2016, 07:56:11 PM »
Richhagen   Sorry got carried away with my own personal project
on your thread.

My Apology

Fredrik

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Re: Arduino inverter load controller
« Reply #39 on: January 25, 2019, 07:05:12 AM »
Hi, I know this is an old thread, but trying to understand the electronics so; What is the purpose of the capacitors, can't the voltage just be sampled without?
Sincerely F.

OperaHouse

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Re: Arduino inverter load controller
« Reply #40 on: January 25, 2019, 08:49:02 AM »
Depends on what you are doing. With solar panels and resistive heating it is absolutely necessary for efficiency. The output is PWM and the capacitors store the energy when the output is off for a short period of time. Simply put, 5A from the panel and 5A from the capacitors will provide a 10A pulse for a period of time. The more capacitance, the more energy can be stored and used for a longer period of time. Even though it is for a very small fraction of a second. It also produces a more stable voltage the micro has time to read  keep the panels at power point. You have asked a very open ended question that can not be answered without further detail.

Fredrik

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Re: Arduino inverter load controller
« Reply #41 on: January 25, 2019, 06:00:25 PM »
Thank you for the quick answer Opera, it helps me understand it a little better I think. ( My understanding: The capacitors harvest the energi “between” the panel PowerPoint and the pwm voltage on point)
I have an off grid cabin in snowy Norway that I would like to upgrade in stages, first more solar, 3x300w panels and a new charge controller. This will give me excess energy most of the time and would like to use it to heat water in two stages. One tank to about 10 degrees C and one to 70degrees, the goal is to have running hot and cold water year round when we arrive. Rough calculations implies I need about 2kWH to achieve this, less with better insulated tanks.
I will probably need to augment with a small wind turbine to ensure that I can harvest enough energi from November to February.
So I would like to dump excess solar to: 1 cold water tank, 2 hot water tank, 3 space heater, Wind in the same order.
Also would be nice to manually switch energi to an element in the tank below the toilet to help the drying out process when needed.
Have read all your Arduino posts and have a grasp of the the coding required and the possibilities a micro opens up.

Will also ad a diesel heater that I can remotely control via a gsm shield to the uno.

That got long quickly, and any inputs is much appreciated:)
Sincerely
F

OperaHouse

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Re: Arduino inverter load controller
« Reply #42 on: January 26, 2019, 11:36:24 AM »
I have good luck in the summer diverting about 2500WH to about 30 gallons.  With a PWM controller, energy is harvested from the panels between on cycles. In MPPT whenever the battery charge current lightens, panel voltage raises.  The heater control detects that and diverts whatever it can.  A diode should isolate the capacitor bank from the panel. Without this the increased current from the capacitor bank could destroy the FET by exceeding the current.  With a MPPT controller, the isolating diode  makes the tracking more responsive.

That also can be diverted to the dishwasher when it is on and it demands energy for heated drying.  That switching is fairly simple with just a relay. For other loads the priority is set by adjusting the power point voltage. Whichever is lowest wins. This allows distributed control. It is a quite practical system and allows me to only have a car battery running everything with the fridge having highest priority. Unless you consider a medical device that has to run. At one time I had the micro running everything but recently I have gone away from that.  I had a lightning strike that took out the micro and was glad I could put individual systems back online one at a time.

Fredrik

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Re: Arduino inverter load controller
« Reply #43 on: January 27, 2019, 04:21:21 AM »
Opera your solution is a big inspiration, I have read and reread your post several times to gain understanding, even ran the schematics by the electro engineer are at work. His comment was; Elegant and what a patient wife:)

Time to start collecting parts and testing coding on the bench. When you say that you don't run everything with the micro anymore, what do you mean? Do you have nanos on every appliance or circuit board based solutions?

One last question, I'm looking at the Midnite Classic CC as a starting point for this upgrade path but that isn't cheap so any input on that? (

OperaHouse

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Re: Arduino inverter load controller
« Reply #44 on: January 27, 2019, 02:15:25 PM »
 and what a patient wife.      She wasn't about the dishwasher and didn't appreciate the comment that I thought I married one! Had to install that pretty fast. We schedule dish washing around mid day when there is the most sun. Not really an inconvenience.

I was on a quest to make the cheapest highest performing solar system from consumer electronics that were thrown away and a very minimal battery storage. It never got much interest, but I achieved my goal. As solar is becoming more common there is a lot of broken equipment for cheap.  With this I am trying to make a more normal looking system so projects are compatible with others.   As the program became large any updates could knock out the system for an hour or more if there was an unusual bug that stumped me.

I've made more than a dozen ways to heat water with PV. The control panel is changing all the time.

OperaHouse

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Re: Arduino inverter load controller
« Reply #45 on: January 29, 2019, 02:47:09 PM »
Thought I would throw this TL494 board found on ebay mod out there. This is the waveform at 255W with a boost converter from 30V to 75V.  At 300W the boost converter goes into current limit so this is about full power.  Yellow trace is inverted and is the output of the TL431, low is inhibit.  Green is drain of paralleled FET, low is powering the heater.  Tall spikes are the dead time for the TL494.  With two heaters, each isolated output could use mechanical thermostat or combined thru a relay.

Fredrik

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Re: Arduino inverter load controller
« Reply #46 on: February 06, 2019, 06:54:55 AM »
OperaH am I understanding you correctly if you now run everything with standalone controls like the inverterboards and the tl431 based designer?
Tried looking for a complete overview of how you have your system running, but got lost somewhere between cool ideas, my lack of understanding and your inputs on other people's projects:)

So I'll come right out and ask for a bit of help, I would like to run a series of PV dump loads from a 3*300w panel that will be connected in series due to long wire runs needed.
1. Load would be hot water tank top element,
2. Would be hot water tank lower element,
3. Would be oil filled space heater(s)

I would like to controll it with an arduino and also use the thermostats in the tank.
The code I can figure out from the sum of your other posts and a bit of previous knowledge, but unsure of the requirements circuitry to make it all behave in a safe an reliable manner.
I get the need for the capacitor bank, the slow high voltage fets, the opto couplers to drive them, but get lost in how to make it all into a system and if I also need the tl494 board as well.

Any help is much appreciated as it would be nice not to burn the cabin down or electrocute my self.

Sincerely
F

OperaHouse

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Re: Arduino inverter load controller
« Reply #47 on: February 07, 2019, 02:46:21 PM »
I've done a number of programs that may work.  Trouble is finding the ones that were actually working among the others.

There are various methods.  One counts up and down 1,000 powering four elements in sequence. Primary element is PWM and when that is maxed out it goes to the next and so on. if that isn't enabled it goes to the next. These programs are so individual to the user whether temp is electronically controled or dead time is included for mechanical thermostats.  PWM a bunch of elements at the same time should be avoided. onlu PWM one at a time.  Seems I was working on one that only did dead time on one heater at a time.

Fredrik

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Re: Arduino inverter load controller
« Reply #48 on: February 08, 2019, 07:13:57 AM »
I liked the counting loop program and will try/modify it to begin with. Temp control will be with electronic sensors feeding the arduino so I avoid switching the AC thermostats. I need to modify the code a bit so it switches an element off as well when required temp is reached instead of just adding more load in sequence.
So the plan is to sense voltage at the capacitor bank, and switch on via opto couplers to suitable FETs or SSRs.
Does that sound about right?