I am trying to make a system which can alert me in case the current through a wire exceeds a certain threshold. Say a wire has current in the range of 0-5 A flowing through it and i would like to be alerted when the current crosses the 3 A(say) mark. The threshold point may be customized as per the requirement of the system. I am more or less a beginner and have not used current as a signal source before.
Basically i would like a pin to be high when the current is more than 3A(say) and to be low at other times. The main project is for monitoring currents of higher values of the range of 100A. I figure i can use a current transformer (a 100:5 maybe) and get the range to a more manageable 5 A. And set the required threshold point on the secondary of the CT at 3 A(say). Is there an alternative way without using the CT?
If anyone can help me out with any ideas, I would be very grateful.
are you using an Arduino? If so i suggest using a normal fuse in series with where you want to be alerted of the current, and program the Arduino to alert you when the fuse is broken.
Comrade_Oscar:
are you using an Arduino? If so i suggest using a normal fuse in series with where you want to be alerted of the current, and program the Arduino to alert you when the fuse is broken.
Yes i am using an Arduino. The fuse would be a one time solution. I would like this system to work continuously and alert whenever the current crosses a certain set point.
You should look at Hall current sensors. By magnetic sensing they convert the current into a small voltage readily measured on analog input by your Arduino.
Even Amazon sells them. Search "arduino current sensor"
I've bought a few on eBay. 100A models are available. Many have digital readouts which is convenient. Be sure to get one with a voltage output since your Arduino does no have eyeballs
Are you measuring AC or DC? If you are measuring AC, the CT will work fine, and if you use a rectifier, cap and resistor on the output, you can get a fairly reasonable DC average of the AC value. Admittedly you won't get the fastest response from the results, but it will work.
For AC and DC, a hall effect sensor is more accurate, and can respond faster, but will be more expensive. Though at 100A it won't be cheap. Again, make sure it gives you a non-visual output that the Arduino can interpret.
You can also use a really small value, high power resistor as well, called a shunt. If you measure across the shunt, you'll get a voltage, and since I=V/R you can get the current. However, a shunt that can handle 100A is probably also going to be expensive. It will work with AC and DC. You also need to make sure the shunt is isolated from your Arduino (And probably located near ground), or you could release the magic smoke. And possibly flames.
Finally, anything that can supply 100A is very, Very, VERY dangerous. Be very sure of what you are doing, since you could cause serious injury, death and/or significant property damage with such currents. Have someone else competent check over your work before proceeding with hooking it up to the final system. If you can just buy a premade and professionally tested module that would be a very good idea.
mirith:
Are you measuring AC or DC? If you are measuring AC, the CT will work fine, and if you use a rectifier, cap and resistor on the output, you can get a fairly reasonable DC average of the AC value. Admittedly you won't get the fastest response from the results, but it will work.
For AC and DC, a hall effect sensor is more accurate, and can respond faster, but will be more expensive. Though at 100A it won't be cheap. Again, make sure it gives you a non-visual output that the Arduino can interpret.
You can also use a really small value, high power resistor as well, called a shunt. If you measure across the shunt, you'll get a voltage, and since I=V/R you can get the current. However, a shunt that can handle 100A is probably also going to be expensive. It will work with AC and DC. You also need to make sure the shunt is isolated from your Arduino (And probably located near ground), or you could release the magic smoke. And possibly flames.
Finally, anything that can supply 100A is very, Very, VERY dangerous. Be very sure of what you are doing, since you could cause serious injury, death and/or significant property damage with such currents. Have someone else competent check over your work before proceeding with hooking it up to the final system. If you can just buy a premade and professionally tested module that would be a very good idea.
Yes I am well aware of the dangers involved. I dont think i will actually be handling or working with the 100 A current. At least not at the moment. Right now i am just trying to figure out the best way to do this project.
I would be working with an AC current so a CT should work fine. I could take the AC output current from the CT and take the voltage across a suitable resistor. The voltage will be AC however. If i manage to get rid of the negative cycle then the arduino will read the RMS of the resultant voltage i suppose?
The alternative suggestion of the hall effect sensor is a good one, but what are the pros and cons of using the hall effect sensor? I guess i can get a direct voltage output from the Hall effect sensor, right?
I looked up at Amazon. Seems like the more common device is the CT. I could not find a Hall effect sensor to measure upto a 100 A current. If there is one around, that can directly give a small proportional voltage output than can be given to the arduino then it will make my project more compact. If you can find one please give me the link.
I could not find a Hall effect sensor to measure upto a 100 A current. If there is one around, that can directly give a small proportional voltage output than can be given to the arduino then it will make my project more compact. If you can find one please give me the link.
