Hi Guys,

I would like to put forward a proposal where fellow members of the forum can join in and design a pic based charge controller for solar/wind/hydro.

The concept will be it can be used for different input voltages as the input signal will just be a voltage divider and with a few tweaks in the software. Once finished a new thread will be made and placed in the RE projects section. The whole idea of starting this is in the spirit of open source I feel we can create a great database of RE related projects.

Initial Suggestions
The lcd will show the voltage and input current from the RE array. A preset voltage will either setup to short the PV panels or divert the load to another source(ie: dumpload). Datalogging is also a great idea to incorporate.


OK I'll leave things at that and wait to see the feedback on this proposal.

Regards Bryan

__________________
" The only way to avoid human error is to avoid the use of humans"

 

OK, I'll start, how about I knock up a circuit with a 16F886, an LCD and keypad on Portb 0-6 and Porta 5-7. This will keep the analogue pins, the ccp modules, the uart, the MSSP and the ICSP pins free. I could then write some basic menu stuff as a place to start. Anyone any preference on language? I suggest BoostC as I have most of it already written (and it's free).

Mike.

 

Sounds cool!

One thing I would suggest would be to keep the C to the simplest C expressions possible, so it can easily be converted to other C compilers, BASIC, ASM etc.

Like instead of large compound expressions you could split it into small single-line expressions, that is much easier to convert (especially to ASM).

Also instead of;
for(x=0; x<16; x++) blah

you can do;
x=0;
while(x<16)
{
blah
x++;
}

I think a menu button system might be more user friendly (more attractive too?) than a numeric keypad, not sure what you had in mind there.

 

Very interesting, have been wanting to do this for a while for a single 75W solar panel. A Microchip app note AN1211a has a maximum power point algorithm. Although that appnote is for a boost topology, I think it has some good ideas.

Would like to do a 10A (solar) prototype. Although I am sure that others would want something much larger, or have more diverse interests. One could use #ifdef to add options for energy type, current ratings, etc. at compile time.

These are some parts on hand, for current sense, the Allegro Hall effect ACS712ELCTR-20A-T or the Maxim 4081. And a large Bourns inductor.

Using Mclr as a menu button sounds good. Key pad could work, if explained a little more.

Might follow along with GCBasic port, and learn something about C in the process.

 

I'll help. Done projects similar to this before.

Although I'm going to be too busy until October.

Vacation!!!

 

Well, I've put together a little circuit, with a 16F886 (could be a 16F88), a 16*2 LCD and 4 push buttons. It only used 7 I/O pins and keeps all the multi use pins free.

I've also written a simple menu system in BoostC. It is not very elegant due to some (newly discovered) limitations of BoostC. Namely, no ROM pointers. It mimics the early mobile phone menus with "back up down enter" buttons and can handle 255 entries and up to 8 levels. I'll tidy it up over the next few days and post it as it will probably be useful for other projects.

Now, what to do next? Anyone any suggestions?

Can anyone suggest a menu structure that I could implement as a test. I always find a real world example the best test.

Mike.

 

Hi Pommie,
Great mate, that your starting on the project, I have plenty of pic's here but not boostC, I do have Oshonsoft Basic both the 16f IDE and the 18f IDE with all the bells and whistles. I have tried to learn C for the pic's but I always stumble on the simple things. Time for me doing electronics is very limited due to my work, the family and running the farm.

Lots of people just go 12 volts with RE for the first time but don't realize the benefits of going for a higher voltage like 24 or 48 volts.

With solar as the only RE input 99.9% of charge controllers simply short the PV panels. As an example that shunt controller schematic I put in the projects section just diverts the input power away from the batteries to a dumpload for a preset period. My dumpload is set for a 19 amp dump which can make my analogue voltage gauge bounce then when the dump switch's off the voltage rises quickly again turning the dumpload on. Now the main bank I have connected is 24 volts @ 500ah so when the batteries are fully charged I do waste the dumpload in heating air.

A good thought for dumploads is stepped switching to multi dumploads depending on the input current that needs to be diverted. The main reason I went with a 19 amp one was the I have have full sun and it's windy I could be getting around 12-14 amps from the PV array and a further 5-20 amps from my 2hp motor conversion wind genny and I am only in the shed briefly at night after work and on weekends.

I do intend to make some new dumploads using nichrome wire and I'll take a heap of pic's and make a thread in the projects section.

More discussion from other members on the design will be welcome as I feel the needs of my system is very different to others.

Regards Bryan

__________________
" The only way to avoid human error is to avoid the use of humans"

 

Why are you dumping the load on PV panels? Or is that the only type of charger controller you have right now?

 

What would you suggest he does with it?.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

Nothing. Unless I missed something huge, PV panels can be in the sun open circuit.

 

It's for wind and hydro as well.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

Two position dip switch for selecting hydro, solar, or wind power?

Rough menu idea.
EDIT: O.K. see there is a combo system of wind and solar in use, so possible to have a Hybrid system setup or menu choice.

 

Just a thought; change the menu for more "human" feel as the thing you will probably want to do most is just view the data, and maybe some simple control functions;
obviously some would have sub menus but the basic control is more user friendly, normally you want switch between displaying stats, then sometimes control stuff, then very rarely chaneg the setup options.

 

Hi Guys,
Good to see some great idea's coming in with the menu system. The idea of dumping the stored data to a PC is one of my goals but I thought it would be a bit audacious of me to suggest it.

For the amount of data suggested I feel a 18f pic say a 18f2550 USB would be perfect for the job. I have the USB addon for OS basic so by using the ready available USB routine would make a HID device easy. Now I did suggest basic for this project, Pommie has suggested using 'C' so whynot make this project code in basic, 'C' and asm to suit everyones flavor of coding. I'm sure with the knowledge of our forum members this can be accomplished so any member that wants to build the project can choose the coding language they are familiar with.

I will have a big think over the next few days with some thoughts on a menu system and post them in here.


It is really great to see this first RE project coming to life and I really hope we can make this project a reality. I feel then the RE section of this forum will bring in a heap more RE people who will help out with questions posted.

Regards Bryan

 

Had thought about the USB question too. If you keep to the RS232 side of things then a lot more options are available to the end user.
1) More devices available, and pin for pin compatibility (e.g. 16f886_887 is same as 18f2620_4620).
2) More compiler options available, as most free versions will not support USB?
3) As an option one could burn a USB PIC with Microchip precompiled hex demo to make a $2-3 serial to USB device, or just use a cable converter.

Good question on what data logging medium to use; eeprom, flash, sd card? Like the idea of eeprom(s), as it would fit with the I2C rtc (DS1307) library that I have. In the end, the control software will be most important, and the interface could be a user definable issue.

Haven't fooled with switchmode stuff before, but willing to learn. Is it right to think this will be a buck regulator/converter? Also that the current control part of the charge profile is likely to use mppt (i.e. check current, test current for max/min boundary, vary PWM up/down to find max reading within boundary). And, that the voltage control part will use a PID algorithm to feed the PWM duty cycle to keep the voltage constant during load swings.