my pic based MPPT development

by **monster** » Tue Mar 09, 2010 7:37 am

hi

i just made my first PIC project. it is a pic controlerd power supply. it can vary the PWM of a mosfet to limit the current. the output is probably a square wave because i have no peak smoothing capacitor or inductor. i just increased the frequency of the switching so high that it read like DC on my multimeter. right now i have it controlling the brightnes of a 20w light bulb but i could easily reprogram it could be control the current draw from a solar panel. it wasn't too complicated but i made lots of mistakes and it has taken me about 3 full days to get it working. i'm so chuffed that i can program pics now

by **TonyB** » Tue Mar 09, 2010 11:59 pm

Hey congratulations mate. All you need now is an inductor and capacitor and you will have a proper BUCK converter.

Decrease the frequency to just above the audible range (around 20KHz) to increase efficiency, and make you pic control the increase or decrease the PWM to regulate an input voltage, and you will have a maximiser.

by **monster** » Wed Mar 10, 2010 12:08 am

thanks Tony. do you have any suggestions for capacitor values?

i did try to add a capacitor and then a buck-converter bit to it. i was expecting to see a difference between flashing and constant brightness but there was none. i didn't realise it was for efficiency. :lol:

i had no clue as to what values of capacitor/inductor to use, just what i could find out of an old computer power supply. where does the inefficiency come from in my mosfet switcher and how does the buck converter bits help?

by **TonyB** » Wed Mar 10, 2010 12:30 am

Hello, if your working around the 30Khz mark, try using something around 100uH inductor, and around 300+uF capacitor.
The inefficiency comes from the high currents (I2R Losses), when your switching high current on and off. Its more effecient to have current in between, or smoothed out, so to speak.

The inductor you have there looks good (for 30 to 40Khz) at this stage, just use a lower voltage higher capacitance cap.

Because the light bulb is a resistive load, you don't really need the inductor and capacitor, because your turning the energy into heat anyways. But, if you using your converter to charge batteries or power electronics of some sort etc, then they are a must.

by **monster** » Wed Mar 10, 2010 9:32 am

thanks for your help. its weird that you need two things to level the peaks (linductor and capacitor). i'm new to this

by **monster** » Tue Mar 16, 2010 10:55 am

hey tony i've just realised that this PIC idea could be used to control regen braking on an electric bike. all i need to do is add a boost converter. do you have any tips for me, for component values etc? i just fried my mosfet trying to do just this, probably had to much "on time". i used the same diode and inductor.

by **ramalakshmi.aps** » Fri Mar 19, 2010 6:01 pm

do you know how to implement MPPT in 8051 microcontroller?

by **dch** » Thu Apr 01, 2010 9:20 am

To do MPPT you just need to measure the voltage and the current. Here's where TonyB described it: Board index ‹ Australian International Model Solar Challenge (AIMSCC) ‹ Tech Talk ‹ Easymax Documentation

See Wikipedia - but that just references TonyB!

my pic based MPPT development

my pic based MPPT development

Re: my pic based MPPT development

Re: my pic based MPPT development

Re: my pic based MPPT development

Re: my pic based MPPT development

Re: my pic based MPPT development

mppt in 8051 microcontroller

Re: my pic based MPPT development

Who is online