[PIC] Choosing a suitable PIC microcontroller for a solar charger

[omega6]

Hi All,

I'm planning to build a PWM solar charger for home use with flexibility/scalability in mind. I'm a beginner with less experience in pic programming. I expect to incorporate the solar charger with below features.


1. Based on PWM algorithm
2. Charging multiple 12V sealed lead acid batteries
3. 20x4 character LCD display for displaying voltages,current,power etc
4. Over voltage / Under voltage / Lightning protection
5. Reverse power flow protection
6. Short Circuit and Over load protection

After much research I have decided to go with microchip XLP micro controllers. These are the options i have, but need to know whether these chips would be adequate or better option are available.

https://www.microchip.com/wwwproducts/Devices.aspx?product=PIC18F85K90
https://www.microchip.com/wwwproducts/Devices.aspx?product=PIC18F45K80
https://www.microchip.com/wwwproducts/Devices.aspx?product=PIC18F47J13

Any suggestions or help would be appreciated from anyone.

Thank You.

 

[betwixt]

Some of those requirements are nothing to do with the controller except for possibly reporting the condition. You can use any of them and many more are also suitable. What you are asking for it at the core of almost all PIC types so your choice is really about whether there is enough IO resource and memory. Also consider any external interfaces you need, for example USB or Ethernet.

Brian.

 

[Easyrider83]

Do you have any schematics or it is just an idea for far away future?

 

[omega6]

Hi betwixt,

Thank you for taking the time to read this thread. Yes, you are correct. Many mcu can do all of that. but my real concerns are the power consumption, memory and IO pins of the micro controller. Also I'd like to know whether there better alternative out there.

Can you please tell me the usefulness of the external interfaces (USB or Ethernet).

Thank You.

- - - Updated - - -

Hi Easyrider83,

Well, right now I don't have any schematics on hand and this is not just an idea for a future design. I'm in the process of tying to design an efficient solar charger at this moment. Any suggestion are welcome as I'm a newbie.

Thank You.

 

[betwixt]

You only need USB or Ethernet if your unit has to communicate with other systems. If it works on it's own you don't need them.

PICs are a good choice, there are several free or low cost development tools and the products are reliable and predictable. I would not worry about the power consumption of the processor itself, even at high speeds they only take a few mA. I have a PIC18F46J11 running here at 38MHz and it only uses 5mA! For your application you don't need a lot of memory. The exact amount depends on what algorithms you use and to some extent the language you write the program in but I would guess you could fit all the things in your list into about 10K quite easily.

Brian.

 

[omega6]

Hi betwixt,

Well, right now i have no plans for any communication interface, but that seems interesting if i could implement remote monitoring through it. BTW is it possible to add USB externally to the system if the PIC does not have it internally.

Is there any other useful features which you may think would be good to have in this system rather than the mentioned common features by me. I would like to implement a system which is unique.

Appreciate all the help from you.

 

[betwixt]

For future expansion I suggest you use a serial interface because it can easily be interfaced to most other systems, including by RS232,RS422,RS432 and also USB through a simple converter. All but the very smallest PICs have built in serial ports (USARTs) so its a very easy system to implement.

Bear in mind the USB has a maximum distance of a few metres but would let you connect directly to most computers/laptops. RS422 and RS432 can go over 1Km! A serial port will offer the option of both.

A feature on most of my designs is a socket to allow re-programming of the PIC from outside the unit. It's very handy if you want to do software upgrades without dismantling anything. The PICS have ICSP ports so try to keep those pins free from other things driving them and bring them to an external connector. Lots of information on this in the data sheets.

Brian.

 

[AMSA84]

Hi omega6, I am starting to learn programming microcontrollers. Right now I have the PIC18F4550 with its respective development board. I think that for starting it is enough. I want to start with the basics and then, progressively go to more sophisticated projects, like for example, digital control of simple DC-DC converters and AC-DC converters.

 

[omega6]

Hi betwixt,

The USART looks promising, and thank you for suggesting. By now I'm well aware of the ICSP ports and gonna put a connector for it.

I have one dough, whether the pic micro controllers I have mentioned in the 1st post is an overkill for my purpose. Do you think a small pic would be sufficient or can you recommend any other pic which is capable of handling solar charging functionality and has additional features/flexibility for later upgrades.

Appreciate all the help from you.

Thank You.

- - - Updated - - -

Hi AMSA84,

The PIC18F4550 is a powerful micro controller and has a lot of features. Good luck with your journey with pics and hope to see a project from you on this forum.

 

[betwixt]

There is nothing stopping you from using an 18F4550 but you could use a much simpler PIC if you wanted to. Much of the 18F4550 would be unused.
For PWM, an analog measurement and an LCD you could consider something like the 16F1847 which is cheaper and smaller but check it has enough IO pins for your needs first.

Brian.