I am building a pic programmer. I sort of asked this previously, but I asked it in a way that I didn’t get the answer I was looking for.
Here is the site from which I got the info for the programmer
http://feng3.cool.ne.jp/en/pg5v2.html
According to this page:
http://feng3.cool.ne.jp/pdf/pg5v2r8pcb.pdf
It looks like the ground is just floating.
I just need some help. How do I ground this, and where do I ground this too?
Note, it says not to use the COM port GND, so I have been told it is a chassis ground, but It doesn’t show me where that is supposed to be on the circuit.
I posted the PCB, but I won’t be working with a PCB i will be doing it with prototyping board.
If you could be very specific with your answers that would be great as I don’t have much of an electronics background, and am still learning.
Thanks a bunch
schematic here:
http://feng3.cool.ne.jp/pgm5v2/sch528.gif
2 responses so far ↓
1 Matt D // Oct 30, 2008 at 11:59 am
The ground that I see on your schematic under Additional Details is the symbol for chassis ( straight lilne with three small legs) which is then usually tied to earth ground via the AC power connection. So if this is a prototype.. you could just tie those points to chassis via any kind of wire. If you have no metal chassis then tie all the points together and tie them to your power supply return (low side of the DC power source).
See also
2 C Anderson // Nov 2, 2008 at 2:02 am
To simplify schematics, the author will often just show a ground connection to a grounded point rather than tying them all together on the schematic. All of those little symbols with three legs sticking out the bottom are tied together - and in a much more NORMAL schematic would be connected to the ground side of your power supply. However…
What further confuses the issue is that the author is “stealing” power from the PC’s serial port, so it’s hard for you to even know where the power is coming from until you sort carefully through the schematic! Cute design, but a little tough to follow for a novice. A better explanation in the project text would have helped you a bit.
Just tie those three-legged grounds together and you’ll be good to go. They don’t need to be tied to any chassis hardware or anything else. There are several ground symbols, and the author just didn’t pick the best one, adding some confusion for the poster above.
As the author says - do NOT connect the ground (GND) lead from the RS-232 port to any of those other grounds. They need to be kept separate.
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