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Offline cooldogTopic starter

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check my schematic?
« on: January 01, 2010, 10:04:31 PM »
hey guys,
so i worked on this for a bit today and was wondering if you guys could check it over for mistakes or any suggestion. its a Atmega8 board with motor driver and 2 sensor ports.

**notes**
there is no programmer pins
there is no actual led just header pins

thanks  ;D

i included:
eagle schematic file
eagle board file
pdf of schematic

also here is a picture of my board i rendered in 3D (thanks admin)
http://i273.photobucket.com/albums/jj217/connornijsse/robotics/alarmclock.jpg

(i know about the words in the top right corner
anyone know how to make the fit? they fit on the eagle board.)
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Offline Trumpkin

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Re: check my schematic?
« Reply #1 on: January 01, 2010, 10:29:45 PM »
Looks good except your going to want to connect your 0.1uf capacitor to the atmega8 more directly (right next to the pins).
EDIT:
While not necessary, you might also want to have a separate power supply for the motors. You can also add a capacitor after the regulator to filter out voltage spikes.
« Last Edit: January 01, 2010, 10:39:38 PM by Trumpkin »
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Offline Soeren

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Re: check my schematic?
« Reply #2 on: January 01, 2010, 10:41:38 PM »
Hi,

[...] wondering if you guys could check it over for mistakes or any suggestion.

Here's what a quick glance got me to note:



(i know about the words in the top right corner
anyone know how to make the fit? they fit on the eagle board.)
Make what fit? and make it fit what?
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
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Offline SmAsH

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Re: check my schematic?
« Reply #3 on: January 01, 2010, 10:44:01 PM »
Soeren beat me too it, overall good but some of the traces take really weird routes through the middle of header pins etc.. Try to avoid doing this if its possible as they can sometimes be a bitch to etch.
Also, some of the traces are thinner than needed, try to make use of all available space, especially for the motor traces as they have heaps of room to grow.
« Last Edit: January 01, 2010, 10:46:12 PM by SmAsH »
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Offline Trumpkin

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Re: check my schematic?
« Reply #4 on: January 01, 2010, 10:47:07 PM »
Did you use the auto route feature of Eagle or did you route the traces yourself?
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Offline cooldogTopic starter

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Re: check my schematic?
« Reply #5 on: January 01, 2010, 11:34:13 PM »
@soeren
wow that helps alot thanks. just a question, what are acid traps? and how do i fix them?
if you look at the link i attached it shows the words running off the board

@trumpkin
i think i will add the capacitor, and move the other. thanks
im not going to be running anything to big so i think ill let it all run from the same. bat. but thanks
its all auto routed. guess i need to go back over it.

btw how do i make the traces bigger on eagle?
how do i make the 90o corners better? like 45
« Last Edit: January 01, 2010, 11:42:50 PM by cooldog »
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Offline SmAsH

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Re: check my schematic?
« Reply #6 on: January 02, 2010, 12:04:01 AM »
btw how do i make the traces bigger on eagle?
how do i make the 90o corners better? like 45
I attached an image of how to do both, on the right is the trace width, the left is the kind of corners.
You must have the wire tool selected to do either of these. Right clicking cycles through the kind of corners too.
Quote
what are acid traps?
An area in a circuit where the acid used cannot flow freely in and out, causing problems of under or over etching.
They are the yellow things in Soerens image, they come from having weird angles mostly, compare the circled joints to the ones not circled and you will see the difference.
« Last Edit: January 02, 2010, 12:10:09 AM by SmAsH »
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Offline cooldogTopic starter

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Re: check my schematic?
« Reply #7 on: January 02, 2010, 09:03:27 AM »
this is the new board.
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Offline Soeren

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Re: check my schematic?
« Reply #8 on: January 02, 2010, 09:51:08 AM »
Hi,

@soeren
wow that helps alot thanks. just a question, what are acid traps? and how do i fix them?
Acid traps are inside corners below 90°, in which it is hard to clean the etchant out properly and hence it will continue to etch the copper and may result in broken tracks over time, as well as generating electrolytic phenomenons (think little batteries in strange places in your circuit), with the humidity out of the air.

You fix them by never making inside corners below 90°.

I have attached a revised file. write "ratsnest [enter]" or hit the ratsnest button when you have loaded it into Eagle.
I have moved some components a bit and traced it with controller power separated from the ADC4/5 ports (as I first thought they were for servos.
Since you didn't hook up the motor driver (Don't call it VCC, when power is called +5V), I have left that for an exercise for you - I have hinted a likely trace route, but then the ADCs and the other tap should be supplied from the line feeding the controller.

if you look at the link i attached it shows the words running off the board
It doesn't on my screen, but I have changed it anyway.


@trumpkin
i think i will add the capacitor, and move the other. thanks
im not going to be running anything to big so i think ill let it all run from the same. bat. but thanks
its all auto routed. guess i need to go back over it.
My comments, in the last post as well as this one, only covers the PCB, as I got the idea, that you weren't finished with the schematics, but just wanted an early oversight.
You definitely need a cap of say 100µF (at least) on the input of the regulator, 1nF to 100nF over the supply of the controller (I personally prefer to smack a 1206-size cap on the solder side after assembly).
As I don't know what the circuit's intended purpose is (an alarm clock with servos?? - for pouring a bucket of cold water over hard sleepers perhaps ;D), I won't comment the schematic further.


btw how do i make the traces bigger on eagle?
That depends on whether you wanna do it for the auto router, for manual routing or you wanna change some traces on an allready routed board.
Auto router - type "drc" and press [enter] (or hit the drc-button) and set up the auto router as you want and then save it into a dru-file.
I could send you a reasonable dru that you can put into the DRU folder under the Eagle folder if you like.
Manual Routing - Change the width parameter on the top of the screen when you are routing.
Allready routed - write "change" and [enter] (or hit the change button), select "width" and finally, the width you want.


how do i make the 90o corners better? like 45
Yes (or even rounded corners if you like, but that's harder on a crammed PCB).

You should take some time to go through the Eagle tutorials (in the subfolder "DOC").
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline cooldogTopic starter

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Re: check my schematic?
« Reply #9 on: January 02, 2010, 02:51:48 PM »
thanks alot for the revised version :D

just a question, should the cap. go before or after the reg.?
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Offline SmAsH

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Re: check my schematic?
« Reply #10 on: January 02, 2010, 04:35:06 PM »
The 100uf is on the input and the 100nf on the output stage.
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Offline cooldogTopic starter

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Re: check my schematic?
« Reply #11 on: January 02, 2010, 09:27:55 PM »
okay, i think i included everything you guys recommended. some of the traces are rather skinny but are needed to get past others.
can someone tell me if i chose the right parts for what i want on the schemtic?

also here are the 3d pics of it (front, back, bottom)
http://i273.photobucket.com/albums/jj217/connornijsse/robotics/alarmclock.jpg
http://i273.photobucket.com/albums/jj217/connornijsse/robotics/alarmclockback.jpg
http://i273.photobucket.com/albums/jj217/connornijsse/robotics/alarmclockbottom.jpg
robot will rule the world and i will be building them
-admin

favorite web sites
http://www.societyofrobots.com/
http://www.instructables.com/

Offline SmAsH

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Re: check my schematic?
« Reply #12 on: January 02, 2010, 10:13:29 PM »
Looks great! Wish i could render my board *grumble*...
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