I have a Pic18f27J13. All of a sudden it started getting warm. I first noticed because the 7805 was getting really hot (and I guess the LDV33 too). Seemed to be working fine then all of a sudden boom.

Not sure what I did. I do have 3 pins connected to a 74238 which takes 5V but they are input pins on the 74238. Is this OK?

And yes I know I have VDDCore hanging open but I have done this before without issue.

 

No idea what's happening but no cap on VDDCore is a No No. Letting it float might lead to instability in the core VDD regulator.
https://forum.allaboutcircuits.com/threads/vddcore.77091/

 

No idea what's happening but no cap on VDDCore is a No No. Letting it float might lead to instability in the core VDD regulator.
https://forum.allaboutcircuits.com/threads/vddcore.77091/

Go ahead and haunt me with one of my old post, why don't you?

OK I got a cap tacked in thee. Wasn't easy.

Good thing I have a backup pic. Hope that one does not go too.

 

The PIC is powered by 3.3V but you have J6 feeding 5V signals direct to the PIC pins?
If so, don't do it.

 

The PIC is powered by 3.3V but you have J6 feeding 5V signals direct to the PIC pins?
If so, don't do it.

That is a very good thought, which leads me to wonder what signal the Horne sensor gives out. Is it 12V? 5V?

 

The PIC is powered by 3.3V but you have J6 feeding 5V signals direct to the PIC pins?
If so, don't do it.

No J6 is an HC05. Those at 3,3V pins from the HC05 going to the pic. The HC05 requires 5V in with a 3.3V LDO regulator on board. My guess is to make it easy for the Arduino people. A jumper would have been nice. I should look at just jumping that regulator out.

Besides RX1 and TX1 are 5V compliant anyway.

 

That is a very good thought, which leads me to wonder what signal the Horne sensor gives out. Is it 12V? 5V?

Home sensor is actually a 74HCT238 that is driven by the Pic.

There is no 12V involved in this circuit other than the supply. The 12V is too power the hard drive motor controller.

 

The PIC is powered by 3.3V but you have J6 feeding 5V signals direct to the PIC pins?
If so, don't do it.

Actually J4 is tied to 5V through a pull up. It was easier to do it that way as far a PCB design. Rc5 is 5.5V tolerant.