Power Controller/Circuit Breaker

Hi am I making a power controller/circuit breaker. One of the main tasks of the design is to be cost effective. Ive decided to use the arduino platform (since I am a beginner) and once the design is complete, but the atmega328 chip and etc and make it a standalone design. I am aware that the 128 is used within the Arduino Duemilanove, but I was wondering if I were to use a Mega board, which does not use the 128, would it stil lbe able to create a standalone version (with just the Arduino Mega 2560 chip)?

Aside from those questions above, I also want to ask about whether or not arduino seems suitable for my project. Essentially a source may be around 120V (AC) with a rated current of 15A in which any current larger, should cause the circuit to break (I assume I can use voltage regulators to regulate the voltage, and a current transformer to measure the current). For the voltage I assume I can use a ADC (e.g AD7041) to output the value of the of the voltage and somehow input that into the arduino and allow it to compare it to a reference value given (in which if the voltage or current go higher than the reference value, would cause the circuit break to trip). For this purpose, does the arduino seem like a suitable platform? I also would like to be able to send an alarm/notice to a host computer (connected to the arduino either wirelessly (zigbee) or through serial (rs232) ) that the circuit can been tripped. Any help regarding this would be awesome, as I’m very new to microcontrollers but would like the design to be as efficient and financially feasible (one of the project tasks) as possible.

This was made for your project it is called a Power Switch Tail 2 http://www.makershed.com/PowerSwitch_Tail_II_p/mkps01.htm

Arduino is fine for your project. The main items you need are a power control relay (you could use the Power Switch Tail 2) and a current sensor. I would recommend you try these:

Relay: http://www.sparkfun.com/products/101 with board: http://www.sparkfun.com/products/9096

Current sensor: http://www.pololu.com/catalog/product/1186

but I was wondering if I were to use a Mega board, which does not use the 128, would it stil lbe able to create a standalone version (with just the Arduino Mega 2560 chip)?

If you are good at surface mount soldering, yes. Have you seen how many legs those chips have, and how small they are?

zack : i will be designing this on my own rather than purchasing the product for it but thanks :)

guitarbuilder : The relay tutorial definetly helped out alot, i will definetly implement it into my design

paul : yeah i think i may just stick with the ATmega328, and just seperate it from the arduino when I want to make it standalone. Do you think the ATmega328 can handle what I would like for it to do?

Maybe some additional details about what you're trying to achieve and what constraints you're working to would make it possible to give you more suggestions. Is this just a budget DIY project in a tight budget? Do you have any practical packaging constraints?

If you only want something to happen when the current/voltage gets too high, you might be better off starting with a conventional circuit breaker, and triggering (something) to do whatever it is you want when it has tripped.

If you're not against some soldering, you can simply use a 5V coil / 220V load relay. Since mains IS dangerous, use some ready-made board/modules. Cheap from China, in theUS cheap from lady ada or others.

Measurement of current can be done using hall effect detectors (isolated), but voltage detection is relatively more complex and to be honest less relevant, as you can't have any impact on it ...

I just bought a set of 5A - 20A range ACS712 module current sensor modules, but didn't receive those yet. Alternatively, there are other current sensors ready to plug on some PCB. But you need to be sure that there will never too much current for the PCB trace width, so it can be tricky...

Hey all sorry for the late reply…hate midterms :p. Well basically I need to use a microcontroller that when it sees that a current or voltage is higher than specified (coming from main line), that a signal will be sent from the microcontroller (analog) to a optocouple which will trigger a switch to break the circuit. When this happens, it then needs (through wifi / serial) alert a host computer that a circuit break has occured. This is essentially the core of my project. I decided with arduino due because I could then just buy a standalone atmega chip (and then bootload it) my program onto the chip. The reason being is that I want to make this project with as little cost as possible and thus, if I were to make a bunch of these circuit breakers, they do not all need standalone arduino due’s. They just need the atmega (bootloaded) with any surround resistances and capacitances etc. Atmega’s are quite cheap, and arduino programming (essentially C) is much simpler than machine language. This is why I chose the arduino over the PIC as though there are C compiliers for PIC, they seem to be quite expensive and regardless, seems that PICs are meant to be programmed through assembly naturally. The price of a standalong pic compared to an AVR (e.g atmega328) isnt that different. One of the concerns that I now have come up with is that if my microcontroller just needs to do somethign as comparing a value and sending a high analog signal when the value exceeds another, that maybe something even simple can be used…such as PICaxe. Unfortunetly, this requires a programmer and such and I believe it works out to be more than the arduino due set up that im thinking of (unless someone can prove me wrong).

tochinet : yes soldering will be done. i will be creating the power supply myself. The issue with hall efect detectors, is that though they are isolated they require power suppled so I think Ill be using a current transformer to read the current. Well for voltage detection im probably going to use a power transfomer as well and Im sure it can be done via the same method as the current transformer.

PeterH : the project isnt exactly budget, but I would like to make it as cheap as possible. Not because I dont have money I just want it to be very efficeint. Hence, the difficulty with choosing the right microcontroller lol.

If you're hoping to use this to protect against spikes on the power line, I'd say it's not a feasible approach. The reaction time will be orders of magnitude too slow to prevent damage. You need some sort of crowbar/clamp protection, of the sort already readily available in surge protected power outlets.

It still seems to me that what you're trying to create is a circuit breaker that combines over current protection and over voltage protection, and the best way to provide both of those is to adopt existing tried and proven mechanisms. Cut open a surge protected power strip and glue the guts onto the side of a conventional mains breaker, by all means.

The easiest way to tell that it's triggered still seems to me to look for a voltage difference between the input and output, and use that to power whatever you want to report the problem. For example you could hook a bunch of these into one Arduino and have it raise some sort of alarm when any of them go 'hi'.

For this purpose, does the arduino seem suitable? To send an alarm/notice to a host computer or through serial (rs232) ) that the circuit can been tripped. Any help regarding this would be great, as I'm new to microcontrollers but would like the design to be as efficient and financially feasible (one of the project tasks) as possible. Do the circuit breakers have to be in perfect working order to protect the equipment from damage in case of surge?