SparkFun Forums

[MrPotatoHead]

Hi friends,

My brother & are both nerds. I figure that will help explain why I want to create something complicated that really isn't needed. On with the complicating..

My brother has iguanas in his back yard in a big cage. There are 9 of them. As of this morning, I am an uncle to four little new ones. Yah. We have 13 now. In the winter, there are heating pads to keep them toasty. In the summer, there are fans with misters so there are not toasty. Right now, my brother turns them on for basically the entire day. It is a waste of power. We can do better.

The idea is to have a single master control board with N number of slave AC channel control boards. Each slave AC board would be a glorified outlet that can be controlled by the master board.

Main control board:
- USB for programming & debug
- Ethernet for real time access
- Slot for wifi upgrade
- RTC
- Temp sensor
- Web host (instead of having software on a PC to control it, you log into it like you would a router)
- SD card for storing data (or something similar. no real preference)
- I2C for AC channel boards

AC channel board:
- I2C for control
- 10 amp & 20 amp versions
- 220AC
- Electrical isolation from main board so a failure does not fry everything.
- Relay, Triac, or something to shut on/off the AC power
- Current measurement so i can plot power usage vs time/temp
- Automatic shutoff for over-current conditions
- Low power uM. Maybe a MPSP430 because I have always wanted to try one.

Advice on any part of this is appreciated. In particular, I need some guidance on the AC channel boards. I do not know the best way to control the AC power with a uM. Relay vs Triac? How to measure the current? Sense resistor vs hall effect current measure IC.

Thanks in advance.

[JonChandler]

Might be a good place for Opto-22 type modules. A low current 5v input controls high voltage AC.

[thebecwar]

Do you plan on using a pre-made webserver, or roll your own?

[MrPotatoHead]

Do you plan on using a pre-made webserver, or roll your own?

I would prefer to roll my own. It is something that I want to learn

Might be a good place for Opto-22 type modules. A low current 5v input controls high voltage AC.

I looked at their website. Stuff is way out of my price budget.

[JonChandler]

Might be a good place for Opto-22 type modules. A low current 5v input controls high voltage AC.

I looked at their website. Stuff is way out of my price budget.

Definitely pricey. Sometimes some great deals can be found on ebay.

[MrPotatoHead]

Unless it cost 10-20 per channel, I would rather build my own. It is more fun that way.

[JonChandler]

Look at the relay boards towards the bottom of this page. They may not handle the current you need, but it's a nice design you might follow. It uses a driver (a FET if I remember correctly) to isolate the relay from the micro.

[MrPotatoHead]

Look at the relay boards towards the bottom of this page. They may not handle the current you need, but it's a nice design you might follow. It uses a driver (a FET if I remember correctly) to isolate the relay from the micro.

Not a bad place to start. I wonder if a TRIAC would have better long term reliability compared to a relay?

[thebecwar]

Do you plan on using a pre-made webserver, or roll your own?

I would prefer to roll my own. It is something that I want to learn

In that case, you'll want to refer to RFC 2616 (HTTP/1.1) which you can get at http://www.w3.org/Protocols/rfc2616/rfc2616.html

You can always see what a web server's response looks like by using telnet on port 80. (Just turn on local echo on your telnet program)