PIC 16HV Family

[Isaac Newton]

Hey guys,

I'm thinking of using one of the pic16f family members for one AC powered project and, choosing the right resistor and the right cap, can I use the equivalent for the pic16HV family powered directly from the mains? I would need some sort of protection circuit for the garbage that we find on the AC line, but the idea is the same. Well, sure it would reduce the costs with parts to build a AC-DC convertes but it all seems to be too good to be true...

[marinedalek]

The highest voltage rating I can see for the PIC16HV range is 15V, which is also a DC rating, not AC. You would still need a transformer with a suitable tap along with a reservoir capacitor and, depending on load, possibly a regulator. The simplest solution is to cater for a 3.3 or 5V voltage rail (which you'll probably need for digital logic anyway) and use a regular PIC16F. In looking up the range of the 16HVs I discovered that there's barely any information on them other than the datasheets, so they don't seem particularly widespread.

[Bloch]

Hey guys,

I'm thinking of using one of the pic16f family members for one AC powered project and, choosing the right resistor and the right cap
<snip>
family powered directly from the mains?

Sure http://ww1.microchip.com/downloads/en/appnotes/00954A.pdf but promise me that you will read and understand all the warnings in the PDF 

[Isaac Newton]

Thanks.

[Psi]

While there's nothing wrong with capacitor based mains power supplies you do need to think carefully about your circuit I/O, since it's not mains isolated like it would be if you used a transformer.

There are also a few types of capacitor mains powersupplies, some are earthed and some move up and down with the mains voltage.

Note: Figure 11 on page 10 of that PDF seems wrong, or I just don't like it.
It's got no current limit capacitor in series and just has 2K of resistance plus the zener across the mains. ??
Even assuming its for 110VAC, that's 150V peak into 2k  = 75mA = 11.2W into two 5W resistors (10W).
It would probably work since the voltage isn't at peak for much duty but it's still not a good design.

[Isaac Newton]

I agree. I give up using this option. I mean, transformers aren't expensive, so...

[RCMR]

Hell, just use a disassembled fake Apple USB supply -- I know where there are two that will be going for a song right now!