Long break

After a long break during which time I designed a buck-boost section for the circuit board, and took a vacation. I am back onto the project.

So once i realized the necessity of the buck boost I went about drawing the circuit and laying out the board, with the help of various websites I got the circuit mostly done. Then came the need to calculate the necessary capacitors and inductors... The numbers I came up with were HUGE! I means really big! and big things usually come with a big price tag. I really needed to get them under control.

The size of the storage elements is inversely proportional to the frequency of the PWM, the faster the PWM, the less storage you need. So I started looking into reducing the time period for the PWM module, and it helped a little, however as it also reduced the resolution and limited how close you could get the actual output to the desired output, I couldn't go low enough to really fix the problem. So I had to look elsewhere.

I started poking around the Microchip website and found the PIC24EF128MC202. The "MC" in the middle stands for "Motor Control" and implies that there is a high speed PWM module on board. After looking into it some more I decided that this was the device to use. With the internal oscillator and PLL running at full clatter, it will run at 70MHz (or so), and that translates into a PWM frequency of ~250kHz with enough resolution. Another benefit was that the device was almost pin compatible with the previous microcontroller I had chosen, so for the main part it was a drop in replacement that would run 5 times faster.

This reduced the need for storage, so I went ahead and finalized the schematic and board and placed orders for the necessary parts. This all came in just after I had left for vacation, so it was about 2 weeks later that I got to start playing with "real stuff"