quick circuit schematic question

[jhu]

i'll be attempting to make this sometime this weekend. since the only circuits i've made in the past (in physics classes no less) never had wires to ground, where are those ground wires supposed to go?

actually i'll be making this one instead. why am i doing this? because i'm anticipating that my new thinkpad 770e that i just bought off ebay has the supervisor password set to something the seller doesn't know. grrr....... what does that mean for me? what i thought was a good deal turns out to be an exercise in learning how to solder and constructing circuits with a breadboard.

 

[BrownTown]

link no work

 

[jhu]

ok, link should work now

 

[YahoKa]

Ground is just a common point on the circuit, so as long as everything connected to ground is connected physically, it's fine.

 

[BrownTown]

just connect everywhere it says ground together....

the "ground" is just the reference potential you are assuming to be 0 in the circuit, so it is on the low end of those 3 batteries, and the high end can be thought of as being at 4.5V, becasue that is its voltage relative to "ground".

 

[jhu]

i actually won't be adding the batteries since sufficient power should be supplied by the serial port. but i guess i still connect all the grounds together? or connect them to something else like a metal computer case?

 

[BrownTown]

no, not like a computer case. Connect them to each other.

 

[slpaulson]

As long as you have everything that needs to be grounded connected to that serial port's ground it will be fine.

Also since you aren't putting those batteries in, how do you plan on getting ~4.5V to those ICs? Assuming you are connecting to a computer serial port, I don't believe there is a +5V output on a serial port.

 

[TuxDave]

Originally posted by: jhu
i actually won't be adding the batteries since sufficient power should be supplied by the serial port. but i guess i still connect all the grounds together? or connect them to something else like a metal computer case?

Doesn't the serial port have a ground pin in addition to the power pin that you're attaching to the circuit?

 

[slpaulson]

Originally posted by: TuxDave

Originally posted by: jhu
i actually won't be adding the batteries since sufficient power should be supplied by the serial port. but i guess i still connect all the grounds together? or connect them to something else like a metal computer case?

Doesn't the serial port have a ground pin in addition to the power pin that you're attaching to the circuit?

Well none of the pins of the serial port are going to VDD in the schematic.
According to the official rs232 spec here there isn't a power pin.

I mean you could probably force one of the pins to +12V in software, but that might not work to well if you put a load on it...

 

[jhu]

Originally posted by: cRazYdood
As long as you have everything that needs to be grounded connected to that serial port's ground it will be fine.

Also since you aren't putting those batteries in, how do you plan on getting ~4.5V to those ICs? Assuming you are connecting to a computer serial port, I don't believe there is a +5V output on a serial port.

actually the eeprom is still attached to the mainboard of the computer so it should get power from that. but it turns out i'll probably be making this one instead

 

[TuxDave]

Originally posted by: cRazYdood

Originally posted by: TuxDave

Originally posted by: jhu
i actually won't be adding the batteries since sufficient power should be supplied by the serial port. but i guess i still connect all the grounds together? or connect them to something else like a metal computer case?

Doesn't the serial port have a ground pin in addition to the power pin that you're attaching to the circuit?

Well none of the pins of the serial port are going to VDD in the schematic.
According to the official rs232 spec here there isn't a power pin.

I mean you could probably force one of the pins to +12V in software, but that might not work to well if you put a load on it...

Well the signals to transmit data have a voltage and to do that you have a signal ground reference or else it will be meaningless. But in the link you sent, there's the signal ground that I was talking about on pin 5 (9 pin) or pin 7 (25 pin)