Electronics > Electronics

First Circuit Schematic - please look over

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cjwillms:
I'm a newbie to circuitry, and I need a bit of help. If possible, please look over my schematic, and tell me if you notice any errors. The whole thing will be built on a breadboard, mostly just for experimentation. I'm really just trying to understand the basics of circuitry design, by controlling a few LEDs and a servo motor.

http://img151.imageshack.us/my.php?image=firstcirucit6wt.jpg

Any suggestions would be appreciated.

Afroman:
First schematic eh? You might wanna stick to something simpler then ;)
Anyways your LED bank is looking good.
I don't think you are meant to connect XTAL1 and 2 to ground.
Your cap C1 is incorrectly wired. It needs to go in parallel with VCC and GND

cjwillms:
I could do simple, but then again, complexity is fun! Lol, anyway, thanks for the suggestions. I went ahead and fixed the errors.

Admin:
Hmmm yea I dont think xtal should be connected to ground either, what does the atmel manual say?

As for the LED's . . . I calculated only 7mA not 10. Do the LED's you are using work with just 1.4mA current? You may or may not want to reduce the resistor sizes.

As for the cap, you probably want ~10mF, not 10uF (and in parallel with ground as Afroman said). But it depends on your power source and amount of current your servo will drain too.

cjwillms:
According to the manual, Xtal1 is the input for the internal crystal, and Xtal2 is the output from the internal crystal. I just figured that since Xtal2 was sending out a signal, connecting it to a GND wouldn't hurt it.

Truthfully, the LEDs confused me. I bought them from here and I really don't know much power they draw. I used this article for guidance, and they mentioned that there 3mm LEDs produced a 1.4v drop, so I figured mine would be around it as well. If not, 7mA is plenty.

I'll be running everything off a 5v power regulator. According to one of the articles on your site (here)


--- Quote ---Capacitors can also be used to prevent power spikes that could potentially fry circuitry. Next to any on/off switch or anything that that could affect power suddenly should have a capacitor across it.

Capacitors can improve efficiency and longevity of electric motors up to 100%. Place a small ceramic capacitor of like 10uF across the two leads of your motor. This works really well with el-cheap-o motors. Not much effect with high-end expensive motors however. These capacitors will also signficantly reduce EMI (Electro Magnetic Interference) and system noise too.
--- End quote ---

10uF seemed reasonable to me. It's really just there to help prevent EMI. The Voltage regulator should stop most surges, and I'll be running off a battery so I shouldn't have any surges.

Anyway, thanks for the suggestions.

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