Programmer

[Jay.slovak]

Another quick question. The schematic has the ground from the power supply hooked up to Vss. Which is also connected to pin 5 on the serial port. If the 78L05's com is on the same ground could it hurt the serial port at all?

No serial port is prety hard to damage... Dont worry about it :wink:

 

[Jay.slovak]

The Power supply is not the problem! But the way the PIC is connected with serial Port is not good. Because RS-232s voltage levels of +-12V :? are "Clamped down" to 0-5V using PIC's internal diodes...
I would definitelly use JDM design instead...

I'm sorry, that is what I meant. But wouldn't the resistors bring the voltage down before entering the PIC?

Yes, but if you look into datasheet, it says that voltage on any PIN mustn't exceed VDD, diodes are ment for protection, not for regular use 8)

 

[williB]

Another quick question. The schematic has the ground from the power supply hooked up to Vss. Which is also connected to pin 5 on the serial port. If the 78L05's com is on the same ground could it hurt the serial port at all?

you need to connect both grounds ,(RS232 & Programmer/pic ) otherwise it wont work.. and if everything else is hooked up correctly it wont damage your serial port..

 

[GatorGuy]

Here is a rough PCB that I made so far. I added the CAPS to the input power and added a few other parts. This is the view looking down at the board if it were clear.

 

[Jay.slovak]

Here is a rough PCB that I made so far. I added the CAPS to the input power and added a few other parts. This is the view looking down at the board if it were clear.

OK, just two notes.
1. is that PCB for SMD PIC?
2. place those ceramic caps, as close to the 7805 as possible, and after the diode...

 

[GatorGuy]

OK, just two notes.
1. is that PCB for SMD PIC?
2. place those ceramic caps, as close to the 7805 as possible, and after the diode...

1. No, it is not for SMD. The first screenshot has all of the layers visible. I added a ss of just the bottom copper layer.

2. Moved the caps.



Thank you Jay!

 

[Jay.slovak]

OK, just two notes.
1. is that PCB for SMD PIC?
2. place those ceramic caps, as close to the 7805 as possible, and after the diode...

1. No, it is not for SMD. The first screenshot has all of the layers visible. I added a ss of just the bottom copper layer.

2. Moved the caps.



Thank you Jay!

Well, it looks pretty good, the board is kinda big, but that should be ok.

 

[GatorGuy]

OK, just two notes.
1. is that PCB for SMD PIC?
2. place those ceramic caps, as close to the 7805 as possible, and after the diode...

1. No, it is not for SMD. The first screenshot has all of the layers visible. I added a ss of just the bottom copper layer.

2. Moved the caps.



Thank you Jay!

Well, it looks pretty good, the board is kinda big, but that should be ok.

Yeah that ss's are a little large. I had to leave them that way to show some detail. The actual size is 3.8" X 2.5". This SS is about the right size. Of course I haven’t taken the time to edit it. I like to clean up the lines and square all of the pins. Also the PIC will be replaced by an 18-pin socket. So I will have to move the soldering points.

 

[GatorGuy]

Would it be possible to put a 78L05 in line with the input pins to regulate the voltage? Or would that affect the data being programmed?

 

[Jay.slovak]

Would it be possible to put a 78L05 in line with the input pins to regulate the voltage? Or would that affect the data being programmed?

Oh absolutelly NOT!
1. Data are bi-directional
2. that IC would corrupt data...

But using Zener diodes would be Ideal!

 

[GatorGuy]

Oh absolutelly NOT!
1. Data are bi-directional
2. that IC would corrupt data...

But using Zener diodes would be Ideal!

:idea:

Gotch Ya! I will work on that.