First Arduino Project

So I got my first Arduino (Mega 2560) two weeks ago. I've been playing around with it and learning the basics and what not. I have decided on a useful project and have been thinking through it and researching out the parts. The parts have been ordered and on the way. So I decided for the mean time I would go ahead and do a wiring diagram of how I think it will eventually go all together. But since this is my first project I thought it would be prudent to have the wiring diagram reviewed by those of you who know what you're doing already.

My project consists of:

20x4 LCD Module
An RTC Module
2 9g Servo Motors
A DHT22 Temperature and Humidity Sensor
A 4 Channel Relay Shield to Control a 120 volt line and a 12 volt line

My plan is to provide a 5v line for the Arduino itself, a 5v line for the other 5v components, a 12v line, and a 120v line. I plan on using an Arduino Nano in the project so my Mega will still be available afterwards.

So if anyone has the time and is willing to look over the wiring diagram real quick, I'd sure appreciate any feedback or suggestions for improvement. Thanks.

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Workshopshed over 10 years ago

Hi Todd,
Some observations. You mention you are using a Mega but the schematic uses the Nano. I don't know what schematic tool you are using but there's some libraries over on the Eagle section of this site if that's what you are using. Your I2C port for the RTC does not seem to be connected up to the standard pins, see
http://www.pighixxx.com/test/portfolio-items/mega/?portfolioID=314

The servos can be attached to any digital pin on the Mega and it will easily handle 2. So they are ok.
http://playground.arduino.cc/Code/MegaServo

You'd need to include a link to the datasheet for your LCD module and specific relay shield to let us know if that's wired correctly. For example does the LCD need 8 data pins attached? Also not all relays can handle 120v (AC?) so that's something you'd want to check with the data sheet.

Cheers,

Andy
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Workshopshed over 10 years ago

Hi Todd,
Some observations. You mention you are using a Mega but the schematic uses the Nano. I don't know what schematic tool you are using but there's some libraries over on the Eagle section of this site if that's what you are using. Your I2C port for the RTC does not seem to be connected up to the standard pins, see
http://www.pighixxx.com/test/portfolio-items/mega/?portfolioID=314

The servos can be attached to any digital pin on the Mega and it will easily handle 2. So they are ok.
http://playground.arduino.cc/Code/MegaServo

You'd need to include a link to the datasheet for your LCD module and specific relay shield to let us know if that's wired correctly. For example does the LCD need 8 data pins attached? Also not all relays can handle 120v (AC?) so that's something you'd want to check with the data sheet.

Cheers,

Andy
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dukeofmarshall over 10 years ago in reply to Workshopshed

I plan on using the Nano in the final version of the project. I plan on continue to use this device for quite some time and didn't want to tie up my Mega.

Here is the relay shield I'm going to tie into. I tried to make sure it would handle the voltage and from everything I've looked up on this, our should be able to handle that much voltage. If I'm reading that incorrectly please let me know. Sure don't want to burn anything down.

http://www.ebay.com/itm/200984268296?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

And here's the LCD Module I have ordered.

http://www.ebay.com/itm/131373850431?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

The wiring I learned about for this HD44780 interface is from here:

http://m.instructables.com/id/Connecting-an-LCD-to-the-Arduino/

Sorry for the wiring diagram as well. This was also my first schematic in eagle and had to create a few of the components that I couldn't find libraries for. The relay shield was one of them. I did get the Nano component from the element 14 library I find.
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Workshopshed over 10 years ago in reply to dukeofmarshall

Ah yes, just read the data sheet, the HD44780 has a switchable 8bit and 4bit data bus so you can connect that up with just 4 data lines.
The HJR-4102-L 5V relays are rated high enough and you've got thick traces on the shield. Just be aware that the screws will be live when it's connected up so don't stick a screw driver into one of the holes unless you are certain the power is off. You'd want to box up your project for similar reasons.
The schematic is fine, I was just a bit confused by your comment about the mega and then the Nano in the diagram. One of the key things to watch for on these arduinos (particularly when adding lots of accessories) is that not all of the pins have the same capability and sometimes they are shared (SCL/SDA on the Uno is a class for that). That's why the Pighi diagrams can be useful
http://www.pighixxx.com/test/portfolio-items/nano/?portfolioID=314
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