shematic of my atmega8 board

[gaurav.p]

hello guys,
i m new to eagle and i have made this board specifically to control 3 dc motors(1 in bi directional and other two in single direction)using l293d and it will be using 5 ir sensors which i will add it later
i m just posting this board schematic to confirm weather i m going in the right track
there are 4 pins n/c in l293d coz they are motor connection and please tell me if i have done any mistake and how will i add a reset switch to the board?
please help thanx in advance

regards,
-gaurav   

[Soeren]

Hi,

No purpose in diagonal corners in the schematic, save that for the PCB (where it matters).

Attached is 2 iterations, one "squared up" and one using a BUS - with all signals in it (and then some) for later use.
It could be made with a separate BUS for each port, one for analog power and one for digital power etc. to make it easier to follow, but that's left as an exercise for you

[chelmi]

please give us a PNG on your schematic, I don't have eagle or whatever you used to create it.

[gaurav.p]

ok i have finally made the modifications and i m embarrassed to ask u how to convert it to png format

-gaurav

[Razor Concepts]

On the mega8, AGND and GND should both be connected to the same ground.
AVCC, VCC, and AREF should be connected to the same +5v.

Right now you have them split off, some are going to an external connector.

[Joker94]

go print, and down the bottom near the prind buttom it has the option of pdf, if you click on that it will make a pdf copy. If you post that that should be fine as most people can read pdf format.

[Soeren]

Hi,

On the mega8, AGND and GND should both be connected to the same ground.

Analog and logic/digital ground (Vss is the correct term for the latter) should be connected in only one place (with proper decoupling). If they should just connect together, there would be no purpose in differentiating, but you really-really don't want digital noise on the analog ground if you're going to use A/D-C.

AVCC, VCC, and AREF should be connected to the same +5v.

Almost the same applies here, Aref should be seriously decoupled if connected to Vdd (which is the proper name, Vcc assumes BjT technology Vdd assumes FETs - whatever Atmel calls it in the datasheet).

[gaurav.p]

so finally i have connected aref,vcc,avcc together and agnd and gnd and the schematic is in the attachment .thanks joker94 .can anybody suggest me how can i add a reset switch in the controller

-gaurav parida

[SmAsH]

Just add a switch to the reset button to pull it high with a pull down resistor.
I don't have eagle anymore so i cant show you... Sorry...

[gaurav.p]

thnx i have made the changes accordingly and added crystals and caps to reduce the noise

[chelmi]

thnx i have made the changes accordingly and added crystals and caps to reduce the noise

If you're talking about the caps associated with the crystal, they are not here for noise filtering. What I understand is that they are
load capacitors and their role is to start the crystal oscillating.