Hey Bskitter!
First of all...
I am using the Arduino with an Ethernet Shield to control the device, I will have 8 relays connected to a TPIC6C595 chip and control that chip with the Arduino. I also want to be able to measure the power consumption of each power outlet (there are 8 of them) I have seen many people use the ACS712 chip on their Arduino's but I fear that the current will be to large (I dont know if that is the correct term to use ) for the chip. The relays I am using are rated at 220v 16Amps I also want to put a fuse before each relay and a surge protector at the inlet plug.
Let's have a talk about the ACS712 chip... I know you are not familiar with this kind of stuff, so I try to explain it... When I open the datasheet I see this at the top:
Fully Integrated, Hall Effect-Based Linear Current Sensor IC with 2.1 kVRMS Isolation and a Low-Resistance Current ConductorIt's a Hall Effect based design, this means, it will use the magnetic field arround a wire to measure the current... For this to do (and this is why they use hall effect sensors) you need enough current. So this means for your 16A application, it won't smoke your application. An other side note: It will only blow up an application if the power dissipation (P=U*I) is too high... and as the resistor is only 1.2mOhm, this won't be a problem for only 16A.
Conclusion: YES you can use the ACS712 chip if you want:
The left side you need to connect in series, That's the 1.2mOhm resistor, where your 16A is flowing (Ip). Becose of the high current ability, there are 2 pin connections for each side...
The right side is your measuring side: You apply 5V voltage, and it will give a voltage in the range of 0-5V analoge output. (between 66 to 185 mV/A output sensitivity)
As your arduino has analoge pins, just connect it to the pin. It has an high input impedance so there is almost no current flowing in your arduino, so that won't give a problem either... (an example for a measurement below)
The next thing...
This is how the CT operates under different input currents and indicates what burden resistor I must use from this diagram it looks like I should use a 50 Ohm resistor to get an output between 0.01 and 5 volts but Ill only get 5 volts output if 60 Amps goes through it and I dont think that will ever happen since its a 16 Amp plug but tell me why I am wrong.
Let me say it: You are wrong...
So you want to measure between 0 and 5V, and you have 16Amps goiing in...
So let's see on the graph:
So on the graph I marked your maximum measurements in red.. As you see, you have 2 known curves arround it (green) above (the invisible) 500 ohm and underneath 200 ohm. Which one should we choose... Well.. when we would choose the 500 ohm, we would measure arround 7.5V for 16A, so way too much. When we take the 200 ohm, we would measure some little above 3V, that's like 50% of our range, so not as good...
Well, get something in between... I would say go with 270 ohm and see what you get, i guess it will be arround 4.0-4.5V @16A you will measure, that will get your job done...
So Basically can someone help me put together a small circuit to get readings from this CT I have and what Chip can I use with the Arduino to iterate through the readings of each of the CT's.
Nope, I won't do that, then you won't learn something.. and I think that's the purpose of goiing to school (just like I still do).
Try it and post your "totally not drawn in paint picture" underneath... A tip: I showed you how to measure with arduino and how the IC works... Not plug and play.. but not that hard...
Last problem...
I also want to power the Arudino and the TPIC6C595 chip off the 12V supply but they need 5V inputs so I googled "12V to 5V circuit and this is the first one that popped up, is it sufficient any circuit that could do a better job that you guys could recommend ?
I think this is "meehhhh".. It's not the best solution... I would make a little bigger circuit to get a stable 5V supply, becose the LM78 series is switching power supply, and will give some noise... Yes you can use some caps arround it (I would set an additional 100nF on the output of that picture)...
Just like I told in the first thing of my post: the power dissipation... 12V-5V = 7V is more than 50% of the power will transfer into heat... Even it is for low current, you may need a little heat sink for that...
When you are doiing this, there are even beter things on the market than the old fashioned lm78 series, like the LT3080 that David used in he's power supply, It's a linear one, and you can easy set the desired output with a single resistor (even trimable with a pot)
Much beter!
Now, it's 0:41 am here, so i'm goiing to get some sleep, i'll see what you answer
Regars,
Lovely Santa