Greetings,
I own a TED (The Energy Detective) 1000 model. It's quite a few years old, and does whole house monitoring. It communicates using PLC.
I decided I wanted to build my own, and use a current transformer on each circuit. This would allow me to really see where my power is going, and I think it sounds fun.
So, I grabbed a $10 CT from sparkfun, along with an MCP3002.
I attached this all to a Raspberry Pi, and so far so good(ish).
Let me step back a quick moment. First, to test the MCP3002, I used a simple 100k pot, and attached that to the input pin.
Since the MCP3002 is a 10-bit ADC, I was able to get ranges from 0-1023 without a problem.
I attached the CT using a 110Ohm burden resistor so the ADC will get ~0-3.3v for the input, since it's using 3.3v as the analog reference.
Using a multimeter, and math, I am able to calculate the output, and it's correct, when I get to about 1200 watts (hair dryer).
My readings on the raspberry pi are all over the board. I definitely can tell there is some accuracy here, but it spikes up and down continuously. I am wondering if this is because the analog input to the ADC is RMS, and therefore goes negative, and depending on when the input is read through to the pi, it could be anywhere on the AC sign wave.
If that could be confirmed, great. And if that is the issue, I am looking for some suggestions to overcome it. I considered a full wave bridge rectifier, but with the very low voltages it won't work, and i'll lose the precision I am looking for,
Thanks!
I own a TED (The Energy Detective) 1000 model. It's quite a few years old, and does whole house monitoring. It communicates using PLC.
I decided I wanted to build my own, and use a current transformer on each circuit. This would allow me to really see where my power is going, and I think it sounds fun.
So, I grabbed a $10 CT from sparkfun, along with an MCP3002.
I attached this all to a Raspberry Pi, and so far so good(ish).
Let me step back a quick moment. First, to test the MCP3002, I used a simple 100k pot, and attached that to the input pin.
Since the MCP3002 is a 10-bit ADC, I was able to get ranges from 0-1023 without a problem.
I attached the CT using a 110Ohm burden resistor so the ADC will get ~0-3.3v for the input, since it's using 3.3v as the analog reference.
Using a multimeter, and math, I am able to calculate the output, and it's correct, when I get to about 1200 watts (hair dryer).
My readings on the raspberry pi are all over the board. I definitely can tell there is some accuracy here, but it spikes up and down continuously. I am wondering if this is because the analog input to the ADC is RMS, and therefore goes negative, and depending on when the input is read through to the pi, it could be anywhere on the AC sign wave.
If that could be confirmed, great. And if that is the issue, I am looking for some suggestions to overcome it. I considered a full wave bridge rectifier, but with the very low voltages it won't work, and i'll lose the precision I am looking for,
Thanks!