Hi all. I'm a complete newbie and stumbled across this project online and thought i'd give it a go. My main aim was to learn more about programming and also find out when and what was consuming the power in our home.
I purchased the emontx kit and soldered everything together and uploaded the firmware. Everything went together fine and as an initial test I just loaded the EmonLibrary example for current only, connected the CT clamp to CT1 and placed this around the power cable to my computer as I have an app that I can run which gives me the Watts used by my computer, so that I could use that to verify what my emonTX was sensing.
Now when I run it I get the following serial output
0.41 0.00
0.41 0.00
0.41 0.00
0.41 0.00
0.41 0.00
0.41 0.00
0.41 0.00
1.47 0.01
0.41 0.00
1.47 0.01
0.41 0.00
0.41 0.00
0.41 0.00
2.48 0.01
1.47 0.01
0.41 0.00
0.41 0.00
0.41 0.00
0.41 0.00
The power usage on my PC reports around 120-130Watts. If I run some intensive tasks on my computer this then jumps up to around 200W however the serial output from the emonTX does not change much from the above output.
Even if I disconnect the CT clamp from CT1 the output still shows the same as above? Am I missing something or is my initial test incorrect? By disconnecting the CT clamd should the values drop to 0 in the serial output? And if so then is there a possibility I may have bridged a connection between some components during the soldering phase?
Any help would be much appreciated.
many thanks.
C
Re: emontx newbie help
Hello and welcome.
A current transformer works by sensing the magnetic field around a wire. If you have put your c.t. around two wires in a two-core (or 3-core) cable that are carrying the same current but in opposite directions, the fields will cancel and you will read nothing.
You need to pass just one wire - either line or neutral but not both - though the c.t.
You can read in Building Blocks about c.t's and installation. (Don't expect a 100 A c.t. and an input that is scaled to read to 24 kW to give highly accurate readings at very low powers).